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CONTEIBUTORS. 
 
 FONES, ALFRED C, D.D.S. 
 
 HOPEWELL-SMITH, ARTHUR, Sc.D., L.R.C.P., M.R.C.S., L.D.S. 
 
 KIRK, EDWARD C, D.D.S., Sc.D., LL.D. 
 
 MERRITT, ARTHUR H., D.D.S. 
 
 MINER, LEROY M. S., M.D., D.M.D. 
 
 OTTOLENGUI, RODRIGUES, M.D.S., D.D.S., LL.D. 
 
 STRANG, ROBERT H. W., M.D., D.D.S. 
 
 THOMA, KURT H., D.M.D. 
 
 TURNER, CHARLES R., M.D., D.D.S. 
 
MOUTH HYGIENE 
 
 A TEXT-BOOK FOR DENTAL HYGIENISTS 
 
 COMPILED AND EDITED BY 
 
 ALFRED C. FONES, D.D.S. 
 
 BRIDGEPORT, CONNECTICUT 
 
 SECOND EDITION, THOROUGHLY REVISED 
 
 Timitb 218 lllustrattons anJ) 8 plates 
 
 LEA & FEBIGER 
 
 PHILADELPHIA AND NEW YORK 
 1921 
 
-i(o- i^^zZ 
 
 Copyright 
 
 LEA & FEBIGER 
 
 1921 
 
 
PREFACE TO THE SECOND EDITION. 
 
 Five years have passed since the pubHcation of the first edition of 
 Mouth Hygiene, and during that period a number of schools have been 
 organized for the education and training of the dental hygienist. 
 The experience of these schools has shown that several of the funda- 
 mental subjects, such as anatomy, physiology, bacteriology, hygiene 
 etc., require more extensive text than could be adequately covered in 
 any one book. It is, therefore, recommended that standard text-books 
 be utilized for such subjects. 
 
 The second edition of Mouth Hygiene endeavors to meet the need 
 of the dental hygienist for those subjects which pertain directly to 
 dentistry and which are essential to her education. 
 
 A. C. F. 
 
 Bridgeport, Conn., 1921. 
 
LIST OF CONTKIBUTOES. 
 
 ALFRED C. FONES, D.D.S., 
 
 Professor of Preventive Dentistry in Columbia University, New York City; 
 Director of the Division of Dental Hygiene in the Bridgeport, Conn., 
 Department of Health. 
 
 ARTHUR HOPEWELL-SMITH, ScD., L.R.C.P., M.R.C.S., L.D.S., 
 
 Professor of Dental Histology, Histopathology and Comparative Anatomy in 
 the LTniversity of Pennsylvania, Philadelphia. 
 
 EDWARD C. KIRK, D.D.S., Sc.D., LL.D., 
 
 Editor of the Dental Cosmos. 
 
 ARTHUR H. MERRITT, D.D.S., 
 
 Specialist in Periodontia, New York City. 
 
 LEROY M. S. MINER, M.D., D.M.D., 
 
 Associate Professor of Dentology in the Boston University School of Medicine; 
 Assistant Professor of Oral Surgery in the Dental School of Harvard Uni- 
 versity, Boston, Mass.; Consulting Oral Surgeon to the Children's Hospital; 
 Oral Surgeon in the Forsyth Infirmary for Children; Chief of the Dental 
 Service in the Massachusetts General Hospital, Boston, Mass. 
 
 RODRIGUES OTTOLENGUI, M.D.S., D.D.S., LL.D., 
 
 Editor of Dental Items of Interest. 
 
 ROBERT H. W. STRANG, M.D., D.D.S., 
 
 Specialist in Orthodontia; Oral Surgeon to the Bridgeport Hospital, Bridgeport, 
 Conn. 
 
 KURT H. THOMA, D.M.D., 
 
 Assistant Professor of Oral Anatomy and Pathology in the Harvard University 
 Dental School, Boston, Mass. 
 
 CHARLES R. TURNER, M.D., D.D.S., 
 
 Dean of the School of Dentistry in University of Pennsylvania, Philadelphia. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 ANATOMY OF THE HEAD 17 
 
 By Robert H. W. Strang, M.D., D.D.S. 
 
 CHAPTER II. 
 
 HISTOLOGY OF THE TEETH AND ASSOCIATED STRUCTURES . 58 
 By Robert H. W. Strang, IM.D., D.D.S. 
 
 CHAPTER III. 
 
 THE TEETH AS A MASTICATING MACHINE 80 
 
 By Charles R. Turner, M.D., D.D.S. 
 
 CHAPTER IV. 
 
 MALOCCLUSION OF THE TEETH 112 
 
 By Rodrigtjes Ottolengtji, M.D.S., D.D.S., LL.D. 
 
 CHAPTER V. 
 
 INFLAMMATION 136 
 
 By Leroy M. S. Miner, M.D., D.M.D. 
 
 CHAPTER VI. 
 
 DEPOSITS AND ACCRETIONS UPON THE TEETH 149 
 
 By Edward C. Kirk, D.D.S., Sc.D., LL.D. 
 
 CHAPTER VII. 
 
 PYORRHEA ALVEOLARIS 166 
 
 By Arthur H. Merritt, D.D.S. 
 
 CHAPTER VIII. 
 
 DENTAL CARIES 173 
 
 By Edward C. Kirk, D.D.S., Sc.D., LL.D. . 
 
viii CONTENTS 
 
 CHAPTER IX. 
 
 ODONTALGIA AND NEURALGIA 191 
 
 By Arthur Hopewell-Smith, Sc.D., L.R.C.P., M.R.C.S., L.D.S. 
 
 CHAPTER X. 
 
 THE RELATION OF ORAL INFECTIONS TO GENERAL HEALTH . 203 
 By Kurt H. Thoma, D.M.D. 
 
 CHAPTER XI. 
 
 DENTAL PROPHYLAXIS 223 
 
 By Alfred C. Fones, D.D.S. 
 
 APPENDIX 299 
 
MOUTH HYGIENE. 
 
 CHAPTER I. 
 
 ANATOMY OF THE HEAD.i 
 
 By ROBERT H. W. STRANG, M.D., D.D.S. 
 
 THE SKULL. 
 
 The twenty-two bones that enter into the formation of the osseous 
 framework of the head are united by immovable joints, the lower 
 jaw excepted, called sutures. These form a strong supporting and 
 protecting structure termed the skull (Fig. 1). This may be con- 
 veniently studied under four headings: (a) the cranium; (6) the base; 
 (c) the lateral aspect; (d) the anterior aspect or face. 
 
 The Cranium. — The cranium comprises that portion of the skull 
 which contains the brain. It is formed by the union of eight bones 
 which are named as follows: frontal, two parietal, occipital, two tem- 
 poral, sphenoid and ethmoid. In outline it is somewhat egg-shaped 
 and presents for study a superior surface, forming the vertex of the 
 skull, and an inferior surface. 
 
 The external surface of the vertex is convex and is covered in the 
 living subject by the tissues that form the scalp. This convexity of 
 surface is ideal for the resisting and warding off of blows. This surface 
 is traversed by three sutures arranged in the form of the letter "H." 
 The anterior cross suture which is situated well toward the top of the 
 skull is called the coronal; the one passing from this to the posterior 
 cross suture is the sagittal; the posterior transverse suture is the 
 lambdoid. 
 
 The internal surface of the vertex is concave and is marked with 
 elevations and depressions for the accommodation of the irregular 
 brain surface. Through the center, running anteroposteriorly, is a 
 groove in which lies the superior longitudinal sinus, a blood channel 
 performing the function of a vein and carrying part of the return 
 blood from the brain. To the margins of this groove are attached 
 some of the supporting membranes of the brain. 
 
 1 Bibliography: Gray's Anatomy; Piersol's Anatomy; Cryer, Internal Anatomy of 
 the Face; Deaver, Special Anatomy of Head and Neck; Swan, Manual of Anatomy; 
 Chapter on Anatomy of the Teeth, by C. R. Turner, in Johnson's Operative Dentistry. 
 2 
 
18 
 
 ANATOMY OF THE HEAD 
 
 There are also numerous smaller grooves in the bony surface which 
 radiate in various directions and in appearance resemble the branches 
 of a tree. In these run the ramifying branches of the middle meningeal 
 artery which supplies the cranial bones and dura mater with blood. 
 
 The inferior surface of the cranium corresponds to the cerebral 
 surface of the base of the skull (Fig. 2) . It is divided by two trans- 
 verse ridges into three planes, arranged like terraces with the anterior 
 one on the highest level. These planes bear the name of fossce and 
 are called according to their position, anterior, middle and posterior. 
 Their surfaces are more or less irregularly concave, grooved to accom- 
 modate bloodvessels and perforated in many places to allow these 
 vessels and also nerves to pass in and out of the cranium. 
 
 ANTERIOR NA 
 SPINE 
 
 GNATHIONi 
 
 Fig. 1. — Side view of typical skull. According to the present nomenclature the bone 
 marked malar should be zygoma and that zygoma should be zygomatic arch. (Cryer.) 
 
 Description of the Fossae. — Anterior Fossa. — The points of interest 
 in this fossa are (a) the prominent bony spine in the median line 
 called the crista galli (cock's crest); (6) near the front end of this 
 on either side, slit-like openings for the passage of the nasal nerves 
 into the nasal cavity; (c) the cribriform plate of the ethmoid bone 
 placed on a somewhat lower level than the rest of the floor of the 
 anterior fossa forming what is known as the olfactory groove. This 
 groove is divided anteroposteriorly by the crista galli, accommodates 
 the olfactory bulb of the brain and has its floor pierced with many 
 
THE .SKULL 19 
 
 openings for the passage of the olfactory nerves to the nasal cavities; 
 (d) the anterior and posterior ethmoidal foramina, situated at the 
 outer edge of the cribriform plate, the former at about the middle 
 and the latter at the posterior end of the plate. The bone forming 
 the floor of the anterior fossa roofs over the orbital cavities. 
 
 Middle Fossa. — In the middle fossa are seen (a) two openings that 
 communicate with the orbits. The smaller of these is the ojJtic fora- 
 men, transmitting the optic nerve and ophthalmic artery to the eye; 
 the larger one is the siihenoidal fissure or anterior lacerated foramen, 
 for the passage of the third, fourth, ophthalmic division of the fifth 
 and the sixth cranial nerves, a s^inpathetic nerve, and also arteries 
 and veins to and from the orbits; (/>) in the center of the fossa a bony 
 formation that resembles a saddle and for this reason is called the sella 
 turcica (Turkish saddle) . In this bony structure is situated the pitui- 
 tary body, one of the so-called ductless glands, which secretes important 
 hormones that exert a marked influence on growth and development; 
 (c) on either side of this, four openings. The two anterior ones are 
 of particular interest because through them pass the divisions of the 
 fifth cranial nerve that go to the upper and lower teeth. The anterior 
 opening is the foramen rotundum and it transmits the superior maxillary 
 division of the fifth nerve. Behind this is the foramen ovale through 
 which passes the sensory and motor portions of the inferior maxillary 
 division of the same nerve. The smallest of the openings is the 
 foramen spinosum through which the middle meningeal artery enters 
 the skull. The largest of these four foramina is called the middle 
 lacerated foramen. This is closed in the living subject with cartilage. 
 On its posterior wall, however, is seen (rf) the inner opening of the 
 carotid canal through which the internal carotid artery gains entrance 
 to the cranium. 
 
 The bone at the posterior aspect of the middle fossa acts as the 
 roof for the middle and internal divisions of the ear and is somewhat 
 irregular in conformation with their make-up. 
 
 Posterior Fossa. — The surface of this fossa is deeply concave and 
 accommodates the cerebellum. It is marked with (a) grooves for the 
 lateral sinuses carrying return blood from the brain. To the edges 
 of these grooves is attached the membrane supporting the cerebellum. 
 (6) The foramen magnum, centrally located, through which passes the 
 spinal cord; (c) the anterior condyloid foramina for the passage of 
 the h}T)oglossal nerves to the tongue; {d) the jugular or posterior 
 lacerated foramina which affords a means of exit to the ninth, tenth 
 and eleventh cranial nerves as well as the lateral sinuses; ie) the 
 internal auditory meati for the passage of the auditory nerves and 
 arteries and the facial nerves. 
 
 The Base of the Skull. — The cerebral surface of the base has just been 
 described under the heading of the Inferior Surface of the Cranium 
 (Fig. 2). 
 
20 
 
 ANATOMY OF THE HEAD 
 
 Groove for super, sagittal sinus 
 
 Grooves for anter. meningeal vessels 
 
 Foramen ccecum 
 
 Crista galli 
 
 Slit for nasociliary nerve 
 
 Groove for nasociliary nerve 
 
 Anterior ethmoidal foramen 
 
 Orifices for olfactory nerves 
 Posterior ethmoidal foramen 
 
 Ethmoidal spine 
 
 Olfactory grooves 
 
 Optic foramen 
 
 Chiasmatic groove 
 
 Tuberculum sellae 
 
 Anterior clinoid process 
 
 Middle clinoid process 
 
 Posterior clinoid process 
 
 Groove for abducent nerve 
 
 Foramen lacerum 
 
 Orifice of carotid canal 
 
 Depression for semilunar ganglion 
 
 Internal acoustic meatus 
 
 Slit for dura mater 
 
 Groove for superior petrosal sinus 
 
 Jugular foramen 
 
 Hypoglossal canal 
 
 Aquceduetus ve^tibuli 
 
 Condyloid foramen 
 
 Mastoid foramen 
 Posterior meningeal grooves 
 
 Fig. 2. — Base of the skull. Inner or cerebral surface. (Gray.) 
 
THE SKULL 
 Incisors 
 
 21 
 
 Canine 
 
 Incisive, canal 
 
 Transmits left nasopalatine nerve 
 Traiunaits desceiuiiiuj palatine vesseh 
 Transmits right nasopalatine nerve 
 
 Lesser palatine foramina 
 
 Posterior nasal spine 
 Musculus uvvlae 
 Pterygoid hamulus 
 
 Sphenoidal process of palatine 
 -Pharyngeal carml 
 
 Pharyngeal tubercle 
 Bituaiion of auditory tube and 
 semicanal for Tensor tympani 
 Tensor veli palatini 
 Inferior tympanic canaliculus 
 Aqtiaednctus rorfJeae 
 Jugular foraimn 
 Mastoid canaliculus 
 Tympanomastoid fissure 
 
 Fig. 3.— Base of tlio skull. External surface. (Oray.) 
 
22 AX ATOMY OF THE HEAD 
 
 The external or inferior surface of the base (Fig. 3) (the mandible 
 removedj presents the following points for study: (a) In front is the 
 hard palate bordered by the teeth. Behind the incisor teeth is a depres- 
 sion in the palate known as the anterior imlatine fossa. In the floor 
 of this fossa are four foramina for the passage of the naso-palatine 
 nerves and bloodvessels from the nose. On the hard palate opposite 
 the last molar teeth are the posterior -palatine foramina transmitting 
 the descending palatine arteries and the anterior palatine ners'es to the 
 hard palate. (6) Behind the hard palate are seen the posterior openings 
 of the nasal cavities on the outer sides of which are the two pterygoid 
 processes of the sphenoid bone, (c) External to these processes are 
 the zygomatic fossce which contain three of the large muscles of mastica- 
 tion, the inferior maxillary division of the fifth nerve and the internal 
 maxillary artery. These fossae communicate with the orbits by means 
 of the large sphenomaxillary fissures, (d) Numerous foramina the most 
 important of which are: ovale, external opening of the carotid canal, 
 stylo-mastoid, posterior lacerated, condyloid and magnum, (e) Two 
 pairs of articulating surfaces, the one to receive the condyles of the 
 mandible and named the glenoid fossce, the other to articulate with the 
 first vertebra, (f) The styloid and mastoid processes which form pro- 
 nounced landmarks and serve for the attachment of muscles. 
 
 The Lateral Aspect of the Skull fFig. 1). — The following landmarks 
 present themselves for study, (a) The malar bone that forms the prom- 
 inence of the cheek, (b) The zygoma which lies very superficially and 
 affords attachment to the masseter muscle, (c) The external auditory 
 meatus and (d) the styloid and mastoid processes. It is of interest 
 to note that practically all of the bone that enters into the formation 
 of the side of the skull above the zygoma is covered by the largest of 
 the muscles of mastication, i. e., the temporal. 
 
 The Anterior Aspect of the Skull or Face. — The anterior portion of 
 the skull is termed the face. The follo'^dng fourteen bones enter into 
 its make-up: two nasal, two lachrymal, the vomer, two superior 
 maxillary, two malar, two inferior turbinates, two palate and the 
 mandible. Passing from above downward the following points of 
 interest are noted : (a) The supra-orbital foramina or notches through 
 which pass arteries and nerves bearing the same names, (b) The orbits, 
 in which well-protected cavities lie the eyes, (c) The nasal fossae. 
 (d) The infra-orbital foramina which transmit the infra-orbital arteries 
 and the end-branches of the superior maxillary nerves, (e) The 
 prominent malar bones, (f) The teeth of the upper and lower jaws 
 supported by their alveolar processes, (g) The mental foramina 
 through each of which an artery and nerve of the same name emerge. 
 (h) The mandible or lower jaw. 
 
 The Orbits. — These are irregular, conical cavities, with the base 
 toward the exterior and the apex inward. The outer edge of the 
 base is in the form of a strong bony ridge which projects a little beyond 
 the e^'e and thus protects it from injury. Seven bones enter into the 
 
THE SKULL 23 
 
 formation of* the walls of the orl)its. On the superior aspect of the 
 outer wall near the base is a depression for the lachrymal gland. Each 
 orbit is in communication with various other cavities and fossse by 
 means of the following openings: (a) The optic foramen and (6) 
 sphenoidal fissure open into the middle fossa of the cranial cavity; (c) 
 the sphenomaxillary fissure gives entrance into the sphenomaxillary 
 and zygomatic fosstt; (d) on the inner wall, the anterior and posterior 
 ethmoidal foramina, which transmit vessels of the same names and the 
 former also the nasal nerve, lead into the anterior fossa; and (e) the 
 nasal duct opens into the nose. The posterior opening of the infra- 
 orbital canal is seen on the floor of the orbital cavity. 
 
 i 
 
 J],-Ostium 
 rnaxillare 
 
 First molar First molar 
 
 Fig. 4. — Vertical transverse section of typical skull. (Cryer.) 
 
 The Nasal Fossae (Fig. 4). — These are large, irregular shaped cavities 
 extending from the floor of the cranium to the roof of the mouth. They 
 are separated from each other by a thin partition made up of bones 
 .and cartilage and called the nasal septum. 
 
 In front these fossae communicate with the exterior by means of 
 two large openings called the anterior nares. In back they open into 
 the pharynx through the posterior nares or choancB. 
 
 The lateral walls are very irregular and are divided by shelf-like 
 bones named turbinates (scroll-like) into three or more sections called 
 meati. The turbinate bones are normally three in number and accord- 
 ing to their position receive the names of inferior, .niddle and superior. 
 
 The floor of the nose is formed by the same bones that make up 
 the hard palate, i. e., the palatal processes of the superior maxillary 
 
24 ANATOMY OF THE HEAD 
 
 and the horizontal processes of the palate bones. The superior surface 
 of these processes receives the name, "floor of the nose," while the 
 inferior surface is called the "roof of the mouth." 
 
 The nasal fossse are in communication by means of openings and 
 canals with the following cavities: (a) The cranium, (6) the orbits, 
 (c) the pharynx, (d) the mouth, (e) three sinuses, i. e., maxillary, frontal 
 and sphenoidal, and (/) three sets of air cells, i. e., anterior, middle 
 and posterior ethmoidal. 
 
 According to function the nasal fossge are divided into two parts, 
 the olfactory and respiratory. The olfactory area is in the upper 
 portion and extends down to include the middle turbinate bones 
 on the one side and two-thirds of the septum on the other. The 
 respiratory portion takes in the remainder of the cavity. 
 
 The nose is lined with mucous membrane which in the olfactory 
 portion is non-ciliated but contains cells that are speciaHzed to receive 
 the sensations productive of smell. That in the respiratory portion 
 is much thicker, contains large plexuses of veins and its cells are of 
 the ciliated variety. Many glands are. found in the mucous membrane 
 of both portions of the nasal cavities. Their secretion is poured upon 
 the free surface of the membrane keeping this moist. The inspired 
 air is warmed as it passes over this membrane due to the heat imparted 
 from the great amount of blood found in the large venous plexuses. 
 
 The hlood supply to the nasal cavity comes through the internal 
 maxillary, the ophthalmic and the facial arteries. 
 
 The nerve supply is of two kinds: (a) that of special sense through 
 the first cranial or olfactory nerve and (6) that of common sensation 
 through the fifth cranial or trifacial nerve. 
 
 The Bony Sinuses and Air Cells.— In all of the bones of the skull 
 that have any great bulk we find cavities. The largest of these cavities 
 are called sinuses while the smaller ones are called air cells. Their 
 function is to reduce the weight of the bone and in the region of the 
 mouth and nose to render the bone more resonant for the purpose of 
 speech. The most important of these sinuses and air cells are the 
 following : 
 
 Maxillary or Antra of Highmore. 
 
 Sphenoidal. 
 
 Frontal. 
 
 Anterior, Middle and Posterior Ethmoidal. 
 
 Mastoid. 
 
 The Maxillary Sinuses or Antra of Highmore (Fig. 4). — ^These are two 
 in number, situated within the bodies of the superior maxillary bones, 
 external to the nose and below the orbits. In shape they are some- 
 what pyramidal, with their bases directed toward the nose and the 
 apices at the prominence of the cheek. They open into the middle 
 meati of the nose at points known as the infundibula. The antra are 
 often divided and partitioned by bony septa. They are lined with 
 mucous membrane which is directly continuous with that of the nose 
 
THE SKULL 
 
 25 
 
 and is covered with ciliated epithelium. The mucous membrane also 
 contains glands. Often the roots of the molar and biscuspid teeth 
 form elevations on the floors of the sinuses and when diseased frequently 
 infect the mucous membrane with most serious results. 
 
 The Sphenoidal Sinus (Fig. 5). — This air cavity may be a single one 
 but is usually partitioned into two distinct cells. It is situated within 
 
 Section turned • 
 
 Sella turcica 
 
 Auditory orifice 
 
 Posterior ethmoidal cells 
 
 Right frontal 
 sinus 
 
 Left frontal 
 sinus 
 
 Infundibulum 
 
 Anterior 
 
 ethmoidal cells 
 Hiatus 
 
 semilunaris 
 Unciform 
 
 process 
 
 Middle meatus 
 
 Inferior concha 
 Probe passing 
 
 into lacrimal 
 
 duct 
 Inferior meatus 
 
 Hard palate 
 
 Alveolar 
 process 
 
 Fig. 5. 
 
 -An anteroposterior section within the nasal cavity, with the middle concha 
 and portion of the cell walls turned up. (Cryer.) 
 
 the body of the sphenoid bone at the posterior aspect of the roof of the 
 nose. It has an opening into the superior meatus and is also lined with 
 mucous membrane continuous with that of the nasal cavity. Often 
 the posterior ethmoidal air cells communicate with this sinus. 
 
 The Frontal Sinuses (Fig. 5). — These are two fairly large cavities 
 within the frontal bone. They are located immediately above the 
 orbits and their position is marked approximately by the eyebrows. 
 
26 ANATOMY OF THE HEAD 
 
 They are really a continuation of the anterior ethmoidal air cells of 
 their respective sides. They open into the middle meati of the nose. 
 Congestion of these sinuses is a usual sequence in a so-called " cold in 
 the head," and gives rise to the accompanying headache so frequently 
 noted in this condition. 
 
 The Ethmoidal Air Cells (Fig. 5). — There are three sets of these found 
 within the lateral masses of the ethmoid bone and named according to 
 their position, anterior, middle and posterior. They are lined with 
 mucous membrane which is a continuation of that lining the nasal 
 passages into which each set of cells opens. These cells are often inter- 
 connected and frequently the posterior set communicates with the 
 sphenoidal sinus. ^ 
 
 The orifices of the canals that lead from the nose to the anterior 
 ethmoidal cells are intimately associated with the openings into the 
 antra and into the frontal sinuses. Thus it is that the antrum, the 
 anterior ethmoidal cells and the frontal sinus of each side are made 
 intercommunicating and their mucous membrane linings practically 
 continuous with each other. These anatomical facts make it very 
 possible for an infection arising within one cavity to travel to one or 
 both of the others. Cases are not uncommon in which an abscess on 
 the root of an upper molar or bicuspid tooth infects the mucous mem- 
 brane of the antrum and the discharge from this tissue passing into the 
 nose infects the lining membrane of the canal that leads to the anterior 
 ethmoidal air cells. The infection traveling up this canal will event- 
 ually involve these cells. The mucous membrane of the frontal sinus 
 may also become involved from the same source, either by an extension 
 from the nasal mucous membrane or directly from that of the anterior 
 ethmoidal cells. Such a pathological condition may be continued into 
 the middle and posterior ethmoidal cells and the sphenoidal sinus. 
 
 The mastoid air cells or antra are situated within the mastoid portion 
 of the temporal bones and will be mentioned under the description of 
 the ear. 
 
 THE EYES. 
 
 These are the organs of vision and consist of two globular bodies 
 situated within the orbits. They are freely movable by means of a 
 ball-and-socket joint formed between the eyeball and a tough, fibrous 
 membrane arranged in the form of a socket. This membrane receives 
 the name of the ca'psule of Tenon. Movement of the eyeball is per- 
 formed through the agency of six muscles that arise from the bony 
 wall of the orbit and are attached to the ball at various points. 
 
 The anterior portion of the eye is covered with a modified mucous 
 membrane which is reflected on to the lids and lines the inner side 
 of these. This membrane is called the conjunctiva and covers that 
 portion of the eye that is commonly called the "white." 
 
 The eyeball (Fig. 6) is made up of three coats within which are 
 three refracting media. The coats are named: 
 
THE EYES 
 
 27 
 
 1. Outer or fibrous. 
 
 2. Middle or vascular. 
 
 3. Inner or nervous. 
 The refracting media are: 
 
 1. Aqueous humor. 
 
 2. Crystalline lens. 
 
 3. Vitreous humor. 
 
 Sulcus circularvi cornecB 
 Posterior chamber 
 
 Conjunctiva 
 
 Sulcus drcularis comece 
 Ciliary body 
 
 Rectus 
 lateralis 
 
 Zonular spaces 
 
 Hyaloid canal 
 
 Rectus 
 medialis 
 
 Sclera 
 
 Choroid 
 
 Retina 
 
 A. centralis retinae 
 
 y\\'\\\\\\\\h2>^ Optic nerve 
 
 Fovea centralis /u.wwwu-as 
 
 Nerve sheath 
 Fig. 6. — The right eye in horizontal section. (Toldt.) 
 
 The Coats of the Eye. — Fibrous Coat. — This is divided into two 
 parts: (a) Cornea, forming the anterior sixth of the sphere and (&) 
 the sclera, forming the remainder, (a) The Cornea. This tissue is 
 made up of cells that will transmit the rays of light and so may be 
 likened to a window. It is more highly convex than the rest of the 
 eyeball, giving this portion of the ball a bulging appearance. Its 
 posterior edge is continued into the sclera. (6) The Sclera. This is 
 a firm, inelastic, fibrous membrane forming the posterior five-sixths 
 of the eyeball. 
 
 Vascular Coat. — This is divided into three parts: 
 
 The iris. 
 
 The ciliary body. 
 
 The choroid. 
 
28 ANATOMY OF THE HEAD 
 
 (a) The iris may be likened unto a circular curtain attached at the 
 periphery and perforated in the center. This "hole" in the center 
 is called the pupil. The iris contains pigment of varying tint and is 
 the tissue that gives the color to the eye. In structure it consists 
 for the most part of muscular fibers of two kinds, circular and radi- 
 ating. When the circular contract the pupil becomes smaller and 
 when the radiating are active the pupil enlarges. 
 
 The iris is suspended in a cavity formed by the cornea in front and 
 the lens behind. It is nearly in contact with the latter structure. 
 This cavity is filled with a modified lymph called the aqueous humor. 
 
 (6) The ciliary body is made up of the ciliary processes and the 
 ciliary muscle. The ciliary processes are composed of foldings, as it 
 were, of the tissues making up the middle coat and are continuous at 
 their posterior ends with the choroid and at their anterior ends with 
 the suspensory ligament of the lens and the iris. They vary from sixty 
 to eighty in number. The ciliary muscle is arranged in the form of a 
 circular band of involuntary muscle fibers lying on the outer surface 
 of the middle coat of the eye between the iris and the choroid. Its 
 function is to control the convexity of the lens so that the rays of light 
 may be properly focused. The ciliary body is an exceedingly vascular 
 area and consequently is very liable to be the seat of an infection, 
 hence it has been designated as the "danger area" of the eye. 
 
 (c) The choroid is that portion of the middle coat that lies posterior 
 to the ciliary body. It is made up of areolar tissue, bloodvessels, 
 and considerable pigment. 
 
 Nervous Coat. — This is commonly called the retina. It is continuous 
 with the optic nerve behind and extends forward about as far as the 
 ciliary body where it ends in a jagged margin. It may be called the 
 end-organ of the optic nerve with the special sense of vision as its 
 function. 
 
 The fibers of the optic nerve are distributed to all parts of this 
 membrane and end in physiological relationship with special cells, 
 the rods and cones, of the neuro-epithelium lining the retina. The 
 rods and cones receive the visual impressions and transfer them to 
 the nerve fibers. 
 
 In examining the retina a white circular area is noted at the point 
 of entrance of the optic nerve. This is called the optic disc and is the 
 one point on the membrane where the rays of light will make no 
 impression. In other words, it is a blind spot. For this reason it is 
 located eccentrically so that the same rays of light will not be received 
 on a blind spot in each eye, damaging the field of vision. Its position 
 is somewhat to the inner side of the center. Directly in the center of 
 the retina is the area where the most acute vision is to be had. This 
 is called the macula lutea (yellow spot) because of its color. In the 
 center of this is a depression known as \h.e fovea centralis. 
 
 The Interior of the Eyeball. — ^The interior of the eyeball is unequally 
 divided by the lens. That portion in front of the lens is further sub- 
 
THE EARS 29 
 
 divided by the iris into two compartments known as the anterior and 
 posterior chambers. The anterior chamber communicates with the 
 posterior chamber through the pupih 
 
 The Refracting Media. — The Aqueous Humor.— This is a watery fluid 
 fining the anterior and posterior chambers of the eye. It is derived 
 from the vessels within the ciHary body and any excess is carried off 
 through spaces and canals that empty into the ciliary veins. 
 
 The Crystalhne Lens. — This is a biconvex, circular body made up of 
 transparent fibrous tissue the component parts of which are cemented 
 together with a transparent cement substance and the entire mass of 
 tissue is surrounded by a capsule. It lies in a depression on the 
 anterior surface of the vitreous body and is held in position by the 
 susyensory ligament of the lens. The function of the lens is to bring 
 the rays of light to a proper focus upon the retina. 
 
 The Vitreous Humor or Body. — In contact with the retina and filling 
 the interior of the eyeball behind the lens is the vitreous humor. It 
 is composed of a soft, jelly-like substance, perfectly transparent, and 
 made up of semisolid connective tissue. This is surrounded by a 
 membrane that is thickened anteriorly to form the suspensory 
 ligament of the lens which holds the lens in position and affords attach- 
 ment to the ciliary processes. The anterior surface of the vitreous 
 body presents a cup-like depression into which the lens fits. 
 
 The Lachrymal Apparatus. — This consists of (a) the lachrymal or 
 tear gland which is situated in a depression at the outer angle of the 
 orbit at its upper aspect and from which several ducts lead and open 
 through the conjunctiva of the. upper lid just before this is reflected 
 on to the eyeball; (b) the lachrymal sac, placed at the inner angle of 
 the orbit and gathering in the tears by means of two small canals 
 leading from the inner corner of each lid; and (c) the nasal duct, a 
 passage that leads from the sac to the inferior meatus of the nose 
 and discharges its contents into this cavity. 
 
 THE EARS. 
 
 The organ of hearing (Fig. 7) is divided into three portions: 
 
 1. The external ear. 
 
 2. The middle ear. 
 
 3. The internal ear or labyrinth. 
 
 The External Ear. — This consists of the cartilaginous structure 
 that is commonly called the "ear" and the external portion of the 
 auditory canal. The latter, known as the external auditory canal, is 
 about one inch in length and runs inward and somewhat forward. It 
 is separated from the middle ear by the tympanic membrane or drum. 
 Its external opening is termed the external auditory meatus. 
 
 The Middle Ear. — This extends from the drum to the internal ear. 
 It approximates one-sixth of an inch in length and is nearly one-half 
 an inch in its vertical diameter. In this cavity are the three ear bones 
 
30 
 
 ANATOMY OF THE HEAD 
 
 or ossicles, as they are called. The middle ear is in communication 
 with the mastoid antrum through a small opening and with the naso- 
 pharynx via the Eustachian tube. Through the middle ear, embedded 
 in its mucous membrane lining, passes the chorda tympani nerve, a 
 branch of the facial, on its way to join the lingual branch of the man- 
 dibular nerve. As will be noted later, this nerve transfers the special 
 sensations of taste from the anterior portion of the tongue to the brain. 
 Hence disease of the middle ear may be attended with loss of the sense 
 of taste on the corresponding side of the tongue owing to involvement 
 of this nerve. 
 
 Cartilage of auricula 
 Attic 
 Incus 
 
 Malleus 
 
 Tympanic cavity 
 
 Tensor tympani 
 
 Tympanic membrane 
 
 Cartilaginous 
 
 part of ext. 
 
 acoustic meatus 
 
 Bony part of 
 
 ext. acoustic 
 
 meatus 
 
 Fig. 7. — External and middle ear, opened from the front. Right side. (Gray.) 
 
 The Tympanic Membrane or Drum. — This consists of an oval mem- 
 brane, obliquely attached to the sides of the auditory canal, the 
 upper portion being nearer the external opening. It presents a con- 
 cave surface to the exterior. Between its layers is bound the "handle" 
 of the malleus, one of the ossicles. 
 
 The Ear Ossicles. — These are three in number and are named from 
 without inward, the malleus or hammer, the incus or anvil and the 
 stapes or stirrup: {a) The malleus is bound to the drum by means 
 of its handle while its so-called head articulates with the body of the 
 incus. (6) The incus is shaped very much like a lower molar tooth in 
 that it has two root-like processes projecting from a body. The body 
 
THE EARS 
 
 31 
 
 articulates with the malleus and the longer of the processes with the 
 stapes, (c) The stapes on the one hand articulates with the incus 
 and on the other fits into the oval window located on the wall of the 
 internal ear. These bones are held in position by ligaments that 
 are attached to the wall of the middle ear. The fiittction of the ear 
 ossicles is to transmit and magnify the sound waves received by the 
 tympanic membrane, conveying them to the lymph contained within 
 the internal ear. 
 
 The Mastoid Antrum. — This consists of a moderately large cavity 
 and several smaller ones, situated within the mastoid portion of the 
 temporal bone just behind the middle ear and in communication with 
 it. These air cavities are often the seat of infection. 
 
 The Eustachian Tube. — This -canal begins at the anterior end of the 
 middle-ear cavity, passes downward, forward and somewhat inward 
 to the nasopharynx. It is about an inch and a half in length. The 
 function of the Eustachian tube is to keep the air within the middle 
 ear of the same density as that of the exterior. This prevents any 
 damage to the drum arising from inequality of air pressure. 
 
 Fig. 8. — Right osseous labyrinth. Lateral view. (Gray.) 
 
 The Internal Ear or Labyrinth (Fig. 8) .—This consists of three parts : 
 The vestibule. 
 The cochlea. 
 The semicircular canals. 
 Each one of these parts is made up of bony walls enclosing within 
 them a membraneous structure. Separating the membraneous por- 
 tion from the bony is lymph which receives the name of 'perilymph, 
 while within the membraneous structures is more lymph, termed 
 endolyviph. 
 
 Of the three parts of the internal ear, the cochlea is placed anteriorly 
 and the semicircular canals posteriorly, while the vestibule lies between 
 them and serves as a connecting chamber. 
 
82 ANATOMY OF THE HEAD 
 
 The Vestibule. — In the external wall of the vestibule is the oval 
 window into which, as already stated, fits the base of the stapes. 
 The vestibule opens into the cochlea by one opening and into the 
 semicircular canals by five openings. It contains two membraneous, 
 sac-like structures, the utricle and the saccule. These are filled with 
 endolymph and are connected with the membraneous portions of the 
 semicircular canals and cochlea. In the utricle are also found many 
 minute calcareous bodies called otoliths. These, by shifting their 
 positions under varying conditions, transmit impulses to the nerve 
 filaments in the mucous membrane of the utricle. 
 
 The Cochlea. — This in structure resembles a snail's shell and from 
 the exterior is somewhat cone-shaped. It is placed with the apex out- 
 ward. In its base are found numerous openings through which the 
 branches of the auditory nerve pass. The base measures about two- 
 fifths of an inch in diameter and the height of the structure is approxi- 
 mately one-quarter of an inch. The spiral canal within the cochlea 
 makes about two and a half turns around the central axis. This 
 canal is divided into three compartments running the whole length of 
 the spirals. In the median compartment, which is the membraneous 
 portion of the cochlea, is the organ of Corti, the name given the structure 
 which receives the sound waves and transmits them to the filaments 
 of the auditory nerve ending within the mucous membrane lining. 
 This compartment is filled with endolymph. 
 
 The Semicircular Canals. — These are three in number and come off 
 from the posterior aspect of the vestibule. They are so located as to 
 be at right angles with one another. Two are in the vertical plane 
 and one in the horizontal. Within these are the membraneous semi- 
 circular canals, external to which is the perilymph and within which 
 is the endolymph. They are lined with a special form of epithelium, 
 the cells of which are in intimate relationship with the end filaments 
 of the vestibular branches of the auditory nerve. These canals 
 undoubtedly play an important part in the mechanism concerned 
 in the maintenance of the equilibrium of the body. 
 
 Interconnection of the Nerve Supply of the Ears and Teeth. — The nerves 
 to the ears are associated, through certain ganglia, i. e., the otic and 
 Meckel's, with the nerves that supply the teeth. Hence it is not 
 uncommon to have earache accompanied by toothache or vice versa. 
 At times earache may be the only symptom of a dental lesion. 
 
 THE MOUTH. 
 
 The mouth may be defined as the cavity at the beginning of the 
 alimentary canal. It contains the organ of mastication and is intimate- 
 ly connected with the function of speech and the special sense of taste. 
 It is bounded in front by the lips; laterally by the cheeks; above by the 
 hard and soft palates; and below by the mylohyoid and genio-hyoid 
 muscles which form its floor. It contains the teeth and the tongue. 
 
THE MOUTH 
 
 33 
 
 Anteriorly the mouth opens to the exterior throuj^h the lips and 
 posteriorly into the pharynx throu^li th(! j'dvces. The mouth cavity 
 is divided into two portions: (a) the vestibule, which lies between the 
 lips, cheeks and teeth, and (h) the mouth i)roper or oral cavity, internal 
 to the teeth. It is lined with mucous mernbraiu; of the stratified 
 squamous variety. This membrane contains many nniccjus glands 
 which pour their contents into the mouth. 
 
 The bony framework of the mouth is formed by (a) the su})erior 
 maxillary bones, (h) the palate bones, and (c) the inferior maxillary 
 bone or mandible. 
 
 Med. jM^'- I'i'J.^ 
 
 Dilatator nauis j'ostekior 
 
 Incisive fossa 
 
 ''\vK''--' U rhitul S.U rf n c e ^^ s,^'^, 
 
 Alveolar canals 
 
 •;'-^W^""^ -•■■'i'l Maxillqry tuberosity 
 
 
 Fig. 9. 
 
 /'finolars 
 Left maxilla. Outer surface. (Gray.) 
 
 The Superior Maxillary Bones (Fig. 9). — These are two in number 
 and form the bulk of bone below the forehead exclusive of the promi- 
 nences of the cheeks. Each superior maxilla consists of a body and 
 four processes. 
 
 The Body. — On the anterior surface is seen, from above downward: 
 (a) a portion of the orbital margin; (6) the infra-orbital foramen; 
 
 (c) incisive fossa, a depression above the roots of the incisor teeth; 
 
 (d) the canine fossa, a depression behind the prominent root of the 
 cuspid tooth, and (e) the ridges of bone overlying the roots of the 
 incisor and cuspid teeth; (/) in the median line a sharj) process of 
 bone called the nasal spine. 
 
 The superior surface of the body forms a portion of tlic floor of 
 
34 ANATOMY OF THE HEAD 
 
 the orbit. It presents the inner opening of the infra-orbital canal. 
 From this canal are given off branch canals which convey the blood- 
 vessels and nerves to the anterior teeth and bicuspids. 
 
 The posterior surface forms part of the zygomatic fossa and pre- 
 sents the opening of the posterior dental canals that take the blood- 
 vessels and nerves to the molar teeth. 
 
 The internal or nasal surface forms a portion of the outer wall of 
 the nasal cavity. It presents the opening that leads into the maxil- 
 lary sinus or antrum of Highmore. This large air cavity is situated 
 within the body of the superior maxillary bone and has been described 
 under the heading of Sinuses. 
 
 The Four Processes: 
 
 1. Nasal. 
 
 2. Malar. 
 
 3. Palate. 
 
 4. Alveolar. 
 
 The nasal process is situated between the nose and the orbit, pro- 
 jecting upward from the body of the bone and articulates with the 
 frontal bone. 
 
 The malar process manifests itself on the outer surface of the bone 
 and articulates with the malar bone. 
 
 The palate process projects horizontally from the inner surface of 
 the body, articulates with the corresponding process of the superior 
 maxillary bone of the opposite side and thus forms with its supe- 
 rior surface the anterior portion of the floor of the nose and with its 
 inferior surface, the corresponding portion of the roof of the mouth. 
 
 The alveolar process is built up on the lower, outer border of the 
 body for the purpose of supporting the teeth, the roots of which are 
 found within its substance. 
 
 The Palate Bones (Fig. 10). — These are two in number. In form they 
 may be likened to the letter "L". Their upright portion, called the 
 vertical plate, helps to form the outer wall of the nasal cavity. The 
 bone corresponding to the base of the "L" is called the horizontal plate 
 and articulates anteriorly with the palate process of the superior max- 
 illa, thus aiding in the formation of the floor of the nose and roof of 
 the mouth. Posteriorly the horizontal plate ends in a free border to 
 which is attached the soft palate. 
 
 The Inferior Maxillary Bone or Mandible (Fig. 11). — In form this 
 bone resembles a horseshoe and is composed of a body and two rami. 
 The latter arise from the posterior ends of the body. The angle 
 formed between the rami and the body varies in degree according to 
 race, type and age. The mandible is the only bone in the skull that is 
 movable. 
 
 The Body. — The external surface is usually concave from above 
 downward, and ends below in a thick ridge. In the median line in 
 front is another thick ridge placed at right angles to the border. This 
 
THE MOUTH 
 
 35 
 
 receives the name of symphysis menti. Below, this fuses with the 
 lower border of the bone to form the prominence of the chin. 
 
 Sfhe nopalatine 
 foramen 
 
 Sphenoidal process 
 Articular portion 
 
 Non-articiilar 
 portion 
 
 Posterior 
 nasal 
 spine 
 
 Pyrmnidal 
 process 
 
 Fig. 10. — Left palatine bone 
 
 HORIZONTAL 
 PART 
 
 Posterior aspect. Enlarged. (Gray.) 
 
 itli^^. 
 
 Mylohyoid line 
 
 BODY 
 
 Fig. 11. — The mandible. Inner surface. Side view. (Gray.) 
 
 Genio- 
 
 glossus 
 Genio- 
 
 hyoideus 
 
 In the region of the first and second bicuspid teeth and about 
 half-way between the upper and lower borders of the bone are seen 
 the mental j or amina, one on either side. These are the anterior open- 
 
36 ANATOMY OF THE HEAD 
 
 ings of the mandibular canals and transmit the mental vessels and 
 nerves. The alveolar process is built on the superior border of the 
 body and serves to maintain the lower teeth in position. 
 
 The internal surface (Fig. 11) presents in the median line four 
 tubercles for the attachment of muscles. Passing back from these along 
 the body of the bone and half-way between its borders is a ridge called 
 the mylohyoid ridge. This serves for the attachment of the muscle 
 of the same name which forms the floor of the mouth. Above this 
 ridge just to either side of the median line are two depressions called 
 the sublingual fossoe and resting in these lie the sublingual glands. 
 Below this ridge in the region of the bicuspid and molar teeth on either 
 side, are two other depressions that receive the submaxillary glands. 
 The sublingual and submaxillary glands pour their secretion into the 
 mouth through a common duct, Wharton's, the opening of which is 
 on either side of the frenum of the tongue. 
 
 The Rami. — The external surface of each ramus serves for the 
 attachment of one of the muscles of mastication, the masseter. The 
 'posterior border terminates below in what is commonly called the angle 
 of the jaw. The internal surface serves as a place of attachment for 
 certain of the muscles of mastication, i. e., the internal pterygoid and 
 the temporal. This surface presents about at its midpoint an opening, 
 the inferior dental foramen, which leads into the canal of the same 
 name. It transmits the inferior dental artery and nerve which furnish 
 the blood and nerve supply to the lower teeth. 
 
 The superior border of each ramus presents two prominences between 
 which is a well-marked notch. The anterior prominence is called the 
 coronoid process and serves for the attachment of the temporal muscle. 
 The posterior prominence is surmounted with an articular cartilage, 
 receives the name of the condyle, and enters into the formation of the 
 temporomaxillary articulation. To the internal surface of the condyle 
 is attached the external pterygoid muscle. 
 
 The Temporomaxillary Articulation. — ^This is a slidiDg hinge joint 
 and is formed by the glenoid fossa on the base of the skull and the 
 condyle of the mandible. The glenoid fossa is somewhat cup-shaped 
 and is limited anteriorly by a ridge, the eminentia articularis. This 
 aids the ligaments of the joint in restricting the forward slide of the 
 mandible. The articulating surface of the condyle is oblong with the 
 long diameter in the transverse plane. Lying between the condyle 
 and the fossa is the intra-articular fibro-cartilage. The capsular liga- 
 ment encloses the entire joint in a fibrous sheath. Four strong fibrous 
 ligaments help to maintain the proper position of the condyle. 
 
 The Muscles Active in Moving the Mandible. — ^These may be divided 
 into two sets: (a) the so-called "muscles of mastication" which bring 
 the lower teeth in contact with the upper in the process of chewing 
 by raising the mandible and (6) the depressor muscles or those which 
 pull the mandible downward as in opening the mouth, 
 
THE MOUTH 37 
 
 (a) The muscles of mastication are five in number, i. e.: 
 
 Temporal. 
 
 Masseter. 
 
 Buccinator. 
 
 Internal pterygoid. 
 
 External pterygoid. 
 (6) The depressor muscles are also five in number. 
 
 Genio-hyoid. 
 
 Genio-hyo-glossus. 
 
 Mylo-hyoid. 
 
 Digastric. 
 
 Platysma myoides. 
 The Lips and the Cheeks (Fig. 12). — These structure are made up of 
 muscles and fibro-elastic tissue. By the action of the muscles found in 
 the lips and cheeks are produced the many varied facial expressions 
 giving the outward manifestation of different mental states. Hence 
 these muscles are known as the muscles of expression. The lips and 
 cheeks are covered on the external surface with skin and on their inter- 
 nal or oral surface with mucous membrane. These two coverings unite 
 at the outer border of the lips. The mucous membrane contains many 
 mucous glands which pour their secretion into the mouth cavity. In 
 the center of the upper lip and sometimes of the lower a fold of mucous 
 membrane is reflected onto the alveolar process. This is called the 
 frenum. 
 
 On the inside of the cheek about opposite the upper second molar 
 tooth is seen a small papilla which marks the opening of the duct 
 leading from the parotid gland. 
 
 The Hard Palate. — The hard palate is formed by the palate processes 
 of the superior maxillary bones and the horizontal processes of the 
 palate bones. Posteriorly it ends in a free border to which the soft 
 palate is attached. It is covered with mucous membrane the surface 
 of which anteriorly is thrown into folds, called rugcB. 
 
 The Soft Palate. — This structure is attached to the posterior border 
 of the hard palate and is formed by five different muscles. These 
 are in turn covered with mucous membrane. The function of this 
 structure is to shut off the nasal passage from the mouth during the 
 act of swallowing. 
 
 The Mucous Membrane. — The mucous membrane or lining tissue of 
 the mouth is made up of two layers, the epithelium and the underlying 
 connective tissue on which this rests. Beneath these two layers is 
 the suhviucosa which is also composed of connective tissue. 
 
 The epithelium is of the stratified squamous variety the outer cells of 
 which become cornified and scaly on that part overlying the alveolar 
 process and the hard palate (Fig. 13) . Under the epithelium is a layer of 
 fibro-elastic tissue the outer surface of which is surmounted with papillse 
 that extend into the epithelium. In this tissue may be seen the ducts 
 of many glands which are passing through the mucous membrane to 
 
38 
 
 ANATOMY OF THE HEAD 
 
 reach the free surface. The glands themselves are located in the sub- 
 mucosa which is composed of large bundles of white fibrous connective 
 tissue, ably supporting the mucous membrane and richly supplied 
 with bloodvessels and nerves. The glands are of two varieties, serous 
 and mucous, and they are constantly active. 
 
 Mucous 
 gland" 
 
 Epifhelinm 
 of mucous, 
 membrane 
 
 Blood- 
 vessels 
 
 '/■'-t^Hair 
 
 ^ follicles 
 
 Epidermis 
 
 Epithelium 
 of mHCous-'\ 
 membrane 
 
 Cross sections /, 
 of muscle'"--. 
 
 Longitudinal 
 sections 
 of muscle 
 fibres 
 
 with high' 
 papillx "" . 
 
 /^ Place where stratum 
 cornenm begins 
 
 Fig. 12. 
 
 -Section through the upper lip of a two-and-a-half-year-old child. 
 X 14. (Szymonowicz.) 
 
 The Tongue.- — The tongue is a muscular organ composed of a root, 
 a body and an anterior free extremity or tip. It is made up of five 
 muscles and is covered with mucous membrane. The under sur- 
 face is attached to the floor of the mouth by a fold of this membrane 
 called the frenum. The base of the tongue is attached to the hyoid 
 bone and to the muscles of the pharynx. 
 
THE MOUTH 
 
 39 
 
 On the surface of the tongue are seen three varieties of papilloB. 
 These are composed of a connective-tissue core developed in the 
 corium (tissue unrler the epithelium) and covered with epithelium. 
 
 Fig. 13. — Stratified squamous epithelium covering the alveolar process: C, corneous 
 layer; P, papilla of connective tissue. About 400 X. (Noyes.) 
 
 s 
 
 Fig. 14. — A section of a taste bud: p, pore; g, gustatory cells ; ep, epithelial cells; 
 .s, sustentacular cells; h, bristles of the gustatory cells. (Schaefer.) 
 
 The most important of these papillse are situated on the back part 
 of the tongue, are arranged in the form of a "V" with the point back- 
 ward, are eight to twelve in number and are called circumvallate pap- 
 illcB. At the base of these papillae are located the taste buds (Fig. 14), 
 
40 ANATOMY OF THE HEAD 
 
 specialized bodies in which filaments of the glossopharyngeal nerve end 
 and through which media the sense of taste is active. Probably there 
 are also some taste buds in the anterior portion of the tongue which 
 are innervated by branches from the chorda tympani nerve that reaches 
 the tongue by joining the lingual nerve soon after it branches from the 
 mandibular nerve. 
 
 On the base of the tongue, behind the circumvallate papillae, is 
 found considerable lymphoid tissue. This is given the name of the 
 lingual tonsil. 
 
 The nerve supply of the tongue is interesting in that it is derived 
 from four different sources. The four nerves functionate in three ways : 
 (a) The nerves of special sense are the glossopharyngeal and the chorda 
 tympani. (6) The nerve of common sensation is the fifth cranial or 
 trifacial and (c) the motor nerve to the muscles of this organ is the 
 hypoglossal or twelfth cranial. 
 
 The Nerve and Blood Supply of the Dental Tissues. — The nerve 
 supply to the structures entering into the formation of and associated 
 with the oral cavity is mainly through the trifacial or fifth cranial nerves 
 and the facial or seventh cranial nerves. Their blood supply is brought 
 by the internal maxillary artery, a branch of the external carotid 
 artery. 
 
 The Trifacial or Fifth Cranial Nerve (Plate I). — This is the great 
 sensory nerve of the head and face. It also contains a few motor 
 fibers. Its connections and terminations within the brain substance 
 are very extensive and far too intricate to be detailed in a work of this 
 kind. With its external distribution, however, the student is expected 
 to be quite familiar. It must be borne in mind that while the fibers of 
 the nerve are described anatomically as running from the brain to the 
 periphery, yet physiologically, sensory nerves should be traced in just 
 the opposite direction because they carry impulses from the exterior 
 to the centrally located ganglia. 
 
 The fifth nerve leaves the pons Varolii (a portion of the spinal cord 
 just below the brain) in the form of two roots, an anterior motor and 
 a posterior sensory. The latter root enters a large ganglion, the Gas- 
 serian, situated on the floor of the middle fossa of the skull just behind 
 the foramen ovale. From this ganglion three large trunks are given 
 off as follows: 
 
 The ophthalmic or first division. 
 
 The superior maxillary or second division. 
 
 The inferior maxillary or third division. 
 
 The ophthalmic division passes forward and enters the orbit through 
 the sphenoidal fissure supplying the various structures in this cavity, 
 the nasal cavity and the upper part of the face, with sensation. 
 
 The superior maxillary division leaves the cranium through the 
 foramen rotundum entering the sphenomaxillary fossa. From this 
 fossa it gains entrance to the orbit via the sphenomaxillary fissure. 
 It passes along the floor of the orbit to the infra-orbital canal which 
 
PLATE 1 
 
 Sensory root 
 Motor root 
 
 A uriculotemporal' 
 nerve 
 
 Distribution of the Maxillary and Mandibular Nerves, and 
 the Submaxillary Ganglion. (Gray). 
 
THE MOUTH 41 
 
 it enters and then emerges from the canal through the infra-orbital 
 foramen to supply the tissues of the face in the region of this opening. 
 Just before this division enters the orbit it gives off the posterior superior 
 dental branches that supply the upper molar teeth. These reach the 
 teeth by passing through the posterior dental canals, the entrance to 
 which are found on the posterior surface of the superior maxillary bones. 
 While in the infra-orbital canal branches are given off that supply the 
 upper bicuspid, cuspid and incisor teeth. 
 
 The other most important branches of the superior maxillary division 
 are the sphenopalatine nerves which are given oft' in the sphenomaxil- 
 lary fossa. These pass to a ganglion also situated in this fossa known 
 as the sphenopalatine or Meckel's ganglion. They constitute the sen- 
 sory roots of this structure. It also receives a motor root that comes 
 indirectly from the facial nerve. Meckel's ganglion is of importance 
 to the student of oral anatomy because its branches, which are numer- 
 ous, are distributed to the mucous membrane of the sphenoidal and 
 ethmoidal air cells and nasal cavity, to the hard palate, the soft palate 
 and the tonsils. 
 
 There are no motor fibers found in either the ophthalmic or superior 
 maxillary divisions of the fifth nerve. Their function is purely a 
 sensory one, that of touch and pain, to those structures to which they 
 are distributed. 
 
 The inferior maxillary division emerges from the cranium through 
 the foramen ovale. Accompanying it through this opening is the motor 
 root of the nerve which joins the sensory division just outside the 
 cranium. This combined trunk is now located in the zj'gomatic fossa 
 and almost immediately is found to divide again. One of these divi- 
 sions contains nearly all of the motor fibers and is distributed to the 
 muscles of mastication, excluding the buccinator. The other, contain- 
 ing but a few motor fibers and made up mostly of sensory ones, is the 
 larger of the two and divides into three branches, i. e., (a) the auric- 
 ulotemporal, which supplies . the tissue about the ear, the temporo- 
 mandibular articulation and sends communicating branches to the facial 
 (seventh cranial) nerve; (6) the lingual which, as previously stated, 
 supplies common sensation to the tongue and which is joined by the 
 chorda tympani branch of the facial nerve; and (c) the inferior dental 
 nerve. This last branch enters the mandibular canal in the body of 
 the inferior maxillary bone, traverses its entire length and emerges 
 through the mental foramen as the mental nerve to supply sensation 
 to the surrounding tissues. While in the mandibular canal minute 
 branches are given off to the various lower teeth. 
 
 Just as the inferior dental nerve is about to enter the mandibular 
 canal it gives off quite a large branch, the mylohyoid nerve. This 
 contains motor fibers and passes downward to supply the mylohyoid 
 and digastric muscles. 
 
 The inferior dental nerve also sends branches to two ganglia, the otic 
 and the submaxillary, furnishing them with their sensory roots. The 
 
42 ANATOMY OF THE HEAD 
 
 most important nerves coming from these ganglia are secretory branches 
 to the saHvar}^ glands. 
 
 The Facial or Seventh Cranial Nerve. — This is the great moto7- nerve 
 of the head and face. It supplies the muscles of expression, certain 
 of the ear muscles, one of the muscles of mastication, the buccinator, 
 and sends communicating branches to three important ganglia, i. e., 
 the otic, the submaxillary and Meckel's. 
 
 The facial nerve also contains a few sensory fibers that convey taste 
 sensation from the anterior two-thirds of the tongue. 
 
 The facial nerve emerges from the pons Varolii and enters the internal 
 auditory meatus accompanying the auditory nerve and artery. It 
 soon leaves the auditory canal and enters another bony canal known 
 as the aqueductus Fallopii and comes out on the exterior of the skull 
 through the stylomastoid foramen. It then enters the substance of 
 the parotid gland and breaks up within this structure into a large 
 terminal arborization known as the pes anserinus (duck's foot) . 
 
 An important ganglion is situated on the facial nerve within the 
 aqueductus Fallopii known as the geniculate ganglion. From this 
 particular part of the nerve important branches are given off that 
 communicate with Meckel's ganglion, the otic and submaxillary 
 ganglia and the tympanic plexus of nerves, thus connecting the seventh 
 nerve with the fifth and ninth cranial nerves. This fact is brought out 
 that the student may realize how closely related and how intimately 
 interconnected are the various parts of the cranial anatomy. Thus 
 symptoms manifested in one area may be but transferred sensations 
 from lesions in quite remote parts. 
 
 One of the most important branches of the facial nerve is the ehordi 
 tympani (Plate I). This is given off in the aqueductus Fallopii and 
 contains mostly sensory fibers. It passes through the middle ear, lying 
 on the tympanic membrane under the mucous membrane, and then 
 escapes from this cavity through a small canal, entering the pterygo- 
 maxillary region. It passes downward and forward to join the lingual 
 branch of the inferior dental nerve. Its sensory fibers pass in this nerve 
 to the tongue and supply its anterior two-thirds with taste sensation. 
 The motor fibers contained in the chorda tympani are passed into 
 the otic and submaxillary ganglia. They are probably the source 
 of the secretory branches given off from these ganglia and going to 
 the salivary glands. 
 
 After the facial nerve leaves the stylomastoid foramen branches are 
 given off to muscles attached to the temporal bone near the styloid 
 process and about the external auditory meatus. The branches form- 
 ing the terminal arborization supply the muscles of expression situated 
 about the eyes, nose, and the upper and lower lips. One of these 
 branches also supplies the buccinator muscle. 
 
 The Internal Maxillary Artery. — ^This is one of the terminal branches 
 of the external carotid artery and arises from that vessel at a point 
 just below and internal to the condyle of the mandible. It embeds 
 
THE MOUTH 43 
 
 itself deeply in the substance of the parotid gland, passes internal to 
 the ramus of the jaw, through the zygomatic fossa to the spheno- 
 maxillary fossa. From here it is continued as the sphenopalatine 
 artery which passes into the nasal cavity through the sphenopalatine 
 foramen. 
 
 Important Branches of the Internal Maxillary Artery. — Soon after 
 its origin from the external carotid, the internal maxillary artery 
 gives off (a) the middle meningeal artery, which is its largest branch. 
 This passes upward and enters the cranial cavity through the foramen 
 spinosum and supplies the whole of the dura mater with blood; ih) 
 the mandibular or inferior dental artery, that passes downward in 
 company with the inferior maxillajy division of the fifth nerve and 
 enters the mandibular canal. It gives off branches to the lower teeth 
 as it passes through the canal and then emerges on to the chin as the 
 mental artery through the foramen of the same name, (c) Branches 
 to the muscles in the maxillary region given off as the artery traverses 
 the zygomatic fossa, {d) In the sphenomaxillary fossa small branches 
 that enter the posterior dental canals in the posterior portion of the 
 superior maxillary bones and supply the upper teeth, (e) The infra- 
 orbital artery, which enters the orbital cavity through the spheno- 
 maxillary fissure in company with the superior maxillary nerve. It 
 passes forward on the floor of the orbit and enters the infra-orbital 
 canal to emerge on the face through the infra-orbital foramen. While 
 in the infra-orbital canal, it gives off branches that supply the upper 
 bicuspid, the cuspid and incisor teeth. (/) The descending palatine 
 artery which enters the posterior palatine canal and comes out on the 
 hard palate through the posterior palatine foramen and supplies the 
 hard palate, {g) The sphenopalatine artery which is the terminal 
 branch. This artery enters the nasal cavity through the spheno- 
 palatine foramen, passes forward on the nasal septum and then dow'n- 
 ward to emerge on the hard palate through one of the foramina found 
 in the incisal fossa. It is then known as the naso-palatine artery 
 and helps supply the hard palate, anastomosing with the descending 
 palatine artery. 
 
 The Lymphatics of the Mouth. — The mouth is well supplied with 
 lymphatics which form rich networks of capillaries in the mucous 
 membrane. These capillaries drain into larger vessels which are 
 connected with groups of lymphatic glands. Most of the lymphatic 
 vessels from the mouth proper, i. e., the cavity internal to the teeth, 
 empty their contents into the cervical lymphatic glands. Some, 
 however, from the lower jaw go to the submaxillary glands. Those 
 draining the vestibule of the mouth are connected with the sub- 
 maxillary and submental glands. These in turn pass their contents to 
 the cervical lymphatic vessels and glands. 
 
 The Salivary Glands. — ^There are three pairs of these glandular struc- 
 tures, i. e.: (a) parotid; (b) the submaxillary; and (c) the sublingual. 
 
 The parotid (near the ear) glands, one on either side, are situated 
 
44 ANATOMY OF THE HEAD 
 
 below and in front of the ears and extend from the zygoma, above, 
 to the angle of the jaw, below. Their ducts, called Steno's or Sten- 
 son's, open into the mouth at points about opposite the upper second 
 molar teeth. 
 
 The submaxillary glands are situated below the floor of the mouth, 
 in contact with the inner surface of the mandible in the region of the 
 bicuspid and molar teeth. The ducts from these glands join with the 
 ducts from the sublingual glands and make their entrance into the 
 mouth on either side of the frenum of the tongue. These ducts are 
 known as Wharton's. 
 
 The sublingual glands are the smallest of the salivary glands and 
 are situated above the floor of the mouth, in the sublingual fossse of 
 the mandible. As has been previously stated, their ducts join with 
 those from the submaxillary glands and make their entrance into the 
 mouth alongside of the frenum of the tongue. 
 
 The Fauces and the Tonsils. — ^The opening leading from the mouth 
 to the pharynx is called the fauces. It is bounded above by the soft 
 palate, below by the base of the tongue, and on either side by two 
 pairs of muscles which receive the names of anterior pillars and pos- 
 terior pillars of the fauces. Between these two pillars, on either side, 
 lie the faucial tonsils. These are lymph nodes which probably act 
 as filtering plants for the lymphatic vessels draining the mouth. 
 Whatever other function they may have still remains a mystery. 
 
 There are two other masses of lymphoid tissue in close relationship 
 to the mouth. One has been mentioned under the description of the 
 tongue. This is called the lingual tonsil. The other is known as the 
 pharyngeal tonsil and is located on the posterior wall of the pharynx, 
 just above the level of the soft palate and between the openings of 
 the Eustachian tubes. Enlargement of the pharyngeal tonsil often 
 occurs in children. The growth, commonly known as adenoids, so 
 completely fills the upper portion of the pharynx as to shut off the 
 passages into the nose and the child is forced to breathe through the 
 mouth. Mouth-breathing, when continued for some time, produces 
 very characteristic symptoms chief among which is a severe oral 
 deformity. Blocking of the orifices of the Eustachian tubes by these 
 growths often produces impairment of hearing. 
 
 THE TEETH. 
 
 The teeth may be defined as the calcified structures attached to 
 the jaw-bones by the alveolar processes and having as their most 
 important function the breaking up of food material in preparation 
 for digestion. 
 
 The teeth must not be thought of as a part of the osseous system 
 of the body for they are in no way related to such tissues morpho- 
 logically. Their origin and structure will be presented in detail in 
 Chapter II. 
 
PLATE II 
 
 '^'■'i^-^ 
 
 A Diagram of a Section Through an Incisor. (Noyes.) 
 
 Showing the bloodvessels of the pulp and peridental membrane. The bone is 
 represented as much too dense. 
 
THE TEETH 45 
 
 The teeth make their appearance in two series or sets. The first, 
 known as the deciduous (falling off), temporary or mill: teeth, are 
 twenty in number, equally divided between each jaw, and named as 
 follows: 
 
 Central incisors. 
 
 Lateral incisors. 
 
 Cuspids. 
 
 First molars. 
 
 Second molars. 
 The second series or set, known as the permanent teeth, number 
 thirty-two when complete. The increase in the number is accounted 
 for by the following: There are three molars on each side in the 
 permanent set instead of two, as seen in the deciduous. Furthermore, 
 these are all three erupted behind the deciduous molars. The latter 
 are replaced when shed by teeth known as the bicuspids. It is there- 
 fore to be noted that while the molar teeth in the deciduous set lie 
 in contact with the cuspids, the molar teeth of the permanent set 
 are separated from their cuspids by two teeth, the bicuspids. The 
 permanent teeth are therefore named as follows: 
 
 Central incisors. 
 
 Lateral incisors. 
 
 Cuspids. 
 
 First bicuspids. 
 
 Second bicuspids. 
 
 First molars. 
 
 Second molars. 
 
 Third molars. 
 Occlusion. — The teeth are arranged in two gracefully curving arches, 
 the lower of which is somewhat the smaller so that the upper overlaps 
 it. The teeth of one arch do not meet those of the other in an end- 
 to-end arrangement, but are dovetailed, as it were, between each 
 other. This brings broad surfaces in contact instead of mere points. 
 There are over one hundred of these surfaces that are in contact when 
 all the teeth are present and in their proper position. These surfaces 
 are known as inclined planes and it is the sliding together of these 
 various inclined planes in a scissors-like action that properly prepares 
 the food for digestion. 
 
 The normal arrangement of the inclined planes of the teeth when 
 the jaws are closed is known as occlusion or normal occlusion (Fig. 15). 
 In this arrangement it will be noted that every tooth, with but six 
 exceptions, is in contact with four other teeth, i. e., one on either side 
 of it and two in the opposing arch. The teeth excluded from this 
 rule are the lower central incisors and lower third molars which are 
 in contact with but three teeth, and the upper third molars, which 
 are in contact with but two teeth. 
 
 The Anatomy of the Tooth (Plate II). — A tooth is divided into two 
 parts, the crown ancl the root, The crown is that portion that projects 
 
46 ANATOMY OF THE HEAD 
 
 above the gum; the root is that portion that, under normal conditions, 
 is surrounded by gum and alveolar process. The bulk of the tooth 
 is made up of calcified connective tissue called dentin. The crown 
 portion of the dentin is covered by the hardest tissue in the body, i. e., 
 the enamel. This is of epithelial or lining tissue origin. The root 
 portion of the dentin is covered with a calcified connective tissue 
 that more closely resembles bone than any of the other tooth tissues. 
 It is called the cementum. It slightly overlaps the enamel at the gum 
 margin. 
 
 
 1 
 
 ^H^^^^Kf 
 
 
 
 ^m W' m 
 
 f^SBfm. 
 
 fyy 
 
 ISj 
 
 WM 
 
 ^B ^ 1 1 
 
 %M 
 
 bf^P 
 
 ll^^^lf^ 
 
 ^fllH 
 
 
 fw 
 
 ^^ 
 
 
 fi 
 
 ^■^^^ 
 
 -^ 
 
 .....^^ 
 
 
 • ;_B 
 
 Fig. 15. — Normal occlusion. (Peeso.) 
 
 In the center of the dentin, extending the whole length of the root 
 and more or less into the crown, is a cavity called the pulp cavity. 
 This contains the remains of the organ that was active when the 
 tooth was being formed and which during this process deposited the 
 dentin. This organ is called the pulp. 
 
 The pulp cavity is divided into two parts, that in the crown, known 
 as the pulp chamber, and that in the root known as the root canal. 
 The root canal communicates with the exterior through a small open- 
 ing at the end of the root. This opening is given the name of the 
 apical foramen. Very frequently there is more than one apical fora- 
 men present. As many as seven or eight distinct openings have been 
 noted. Through the apical foramen the bloodvessels, lymphatics 
 and nerves pass to and from the pulp. 
 
THE TEETH 47 
 
 Surrounding the root and separating it from the bony wall of the 
 socket is a fibrous membrane known as the peridental membrane. This 
 has for its most important function the binding of the tooth to the 
 surrounding bone. The bone that supports the teeth is known as 
 the alveolar process. This is formed about the roots of the teeth 
 as they erupt. When a tooth is removed from its process an opening 
 is left that resembles in outline the shape of the root. This cavity 
 or socket is called an alveolus. 
 
 Surmounting the alv^eolar process is a dense, fibrous connective 
 tissue called the gum. This is covered with mucous membrane con- 
 tinuous with that of the rest of the mouth. 
 
 Nomenclature. 
 
 The following terms are used in describing the anatomy of the various 
 teeth and the student will find it necessary to become familiar with 
 these in order that the text may be clear and the parts referred to 
 definitely fixed in mind. 
 
 The neck, cervix or gingival margin is that part of the tooth where 
 the enamel and cementum meet. 
 
 The apex is the end of the root. 
 
 The occlusal end or surface is the top of the crown, /. e., that portion 
 of the tooth used in mastication. 
 
 A cusp is a projection or tubercle on the surface of the crown. 
 
 The proximal or approximal surface is that surface that adjoins 
 the next tooth. The most prominent point of this surface is called 
 the point of contact or angle of the tooth. 
 
 The mesial surface is that approximal surface that is nearest the 
 median line of the arch, i. e., a line drawn between the central incisors. 
 
 The distal surface is that approximal surface that is farthest away 
 from such a line. 
 
 The surface of the incisors and cuspids that presents toward the lips 
 is called the labial surface. The corresponding surface on the bicuspids 
 and molars, presenting toward the cheeks, is termed the buccal surface. 
 
 The surface of the upper teeth presenting toward the palate is 
 called the palatal surface. The corresponding surface on the lower 
 teeth presents toward the tongue and is called the lingual surface. 
 The palatal surface of the upper teeth is also often called the lingual 
 surface. 
 
 Descriptive Anatomy of the Various Teeth. — The Incisors (Figs. 16 to 
 19). — The crowns of these teeth are wedge-shaped with the sharp edge 
 downward. They present four surfaces and an incisal or cutting edge 
 for study. 
 
 Labial Surface. — This is convex and on the upper incisors is irregu- 
 larly quadrilateral while on the lower it is more of a triangle in out- 
 line. There are usually two grooves running vertically through this 
 surface, known as the developmental grooves. AH the borders of this 
 
48 
 
 ANATOMY OF THE HEAD 
 
 Fig. 16. — Left upper central incisor. Labial surface. (.Johnson.) 
 
 Fig. 17. — Right upper lat- 
 eral incisor; lingual ^^surface. 
 (Johngon.) 
 
 Fig. 18. — Right lower 
 central incisor; labial sur- 
 face. (JohRSOR.) 
 
 Fig. 19. — Right lower 
 central incisor ; lingual 
 surface. (Johnson.) 
 
Tim I'KKT/f 49 
 
 surface are more or less convex, that at the gingivus being markedly 
 so. This margin also ends in a distinct ridge. The mefilo-incisal 
 angle is quite sharp while the dufto-incisal angle is rounded. 
 
 Lingual or Palatal Surface. — This is irregularly triangular in outline 
 with the base downward. The surface is concave and the margins 
 are outlined with ridges. Sometimes in the center of the cer\'ical 
 ridge is a rudimentary cusp at the base of which is a depressitni or pit. 
 
 Mesial and Distal Surfaces. — In outline these resemble arrow heads 
 and their general surface is convex. They present two concave mar- 
 gins, the lingual and gingival, and one convex, the labial. 
 
 Incisal Edge. — The plane of this surface is more or less at a right 
 angle to the crown. It is of varying thickness and in newly erupted 
 teeth presents three tubercles. These quickly wear off as the teeth 
 are used. 
 
 The roots are cone-shaped with the labiolingual diameter greater than 
 the mesiodistal. In the lower teeth the roots are even more flattened 
 mesiodistally than in the upper. The apex of the root often has a 
 slight distal bend. 
 
 Each pulp cavity follows roughly in outline the shape of the tooth. 
 
 Individual Characteristics of the Incisors. — Upper Central. — This is 
 the largest of the incisors. Its root is shorter and thicker than that of 
 the others. Upper lateral. The distal surface of the crown of this 
 tooth is very convex so that the point of contact is quite prominent 
 and the incisal edge, oblique. Its root is the longest of the incisor 
 roots. Lower Central. This is the smallest of the incisors. 
 
 The Cuspids. — The crowns of these teeth present for study four 
 surfaces and an incisal edge that takes the form of a cusp. 
 
 Labial Surface (Fig. 20) . — This is very convex and is marked wuth two 
 developmental grooves between which is a prominent ridge. It has 
 five borders as follows: two approximal, two incisal and one cervical. 
 The approximal and the cervical are convex, while the incisal are 
 usually quite straight. The disto-incisal border is the longer of the 
 two. 
 
 Lingual Surface (Fig. 21) . — This is similar in outline to the labial and 
 also presents a vertical ridge running through the center. The cervical 
 end of this ridge is frequently marked with a tubercle. 
 
 The mesial and distal surfaces are similar in outline to the corre- 
 sponding surfaces of the incisors but are of greater dimensions labio- 
 lingually. 
 
 The Incisal Edge. — ^This is in the form of two planes, a mesial and 
 a distal. The distal is the longer of the two. At their point of union 
 they are joined by the labial and lingual ridges of the surfaces of the 
 same name, to form the cusjJ. 
 
 The roots are conical, flattened mesiodistally and sometimes even 
 concave on these sides. A distal bend at the apex is quite common. 
 The upper cuspid has the longest root of any tooth in the mouth. 
 
 Each pulp cavity has the same general outline as the tooth. 
 4 
 
50 
 
 ANATOMY OF THE HEAD 
 
 Distinguishing Points between the Upper and Lower Cuspids. — The 
 crown of the lower cuspid is more dehcate in shape and shghtly longer 
 than the upper. Its root is shorter and more flattened mesially and 
 distally. 
 
 Fig. 20. — Right upper cuspid; labial surface. 
 (Johnson.) 
 
 Fig. 21. 
 
 —Right 
 surface. 
 
 upper cuspid; lingual 
 (Johnson.) 
 
 Mesial 
 
 Fig. 22. — Left upper first bicuspid; occlusal surface. (Johnson.) 
 
 The Bicuspids (Figs. 22 to 26). — The crowns of these teeth are irregu- 
 larly cuboidal in form and present five surfaces for study, i. e., buccal 
 lingual, mesial, distal and occlusal. 
 
 The buccal surface is convex, is bounded by five borders, and closely 
 resembles the corresponding surface of a cuspid but is somewhat 
 shorter than this tooth in its vertical dimension. 
 
THE TEETH 
 
 51 
 
 Fig. 23.— Left upper first bicuspid ; mesial 
 surface. (Johnson.) 
 
 Fig. 24. — Left lower first bicuspid ; 
 buccal surface. (Johnson.) 
 
 Fig. 25. — Left lower first bicuspid; 
 distal surface. (Johnson.) 
 
 Fig. 26. — Right upper second bicuspid; 
 mesial surface. (Johnson.) 
 
52 ANATOMY OF THE HEAD 
 
 The lingual surface has the same general characteristics as the 
 buccal but is smaller in all its dimensions. 
 
 The mesial surface is irregularly quadrilateral and slightly convex. 
 Its buccal and lingual borders are convex, the lingual being consider- 
 ably the shorter of the two. The cervical and occlusal borders are 
 concave. The occlusal border of the upper bicuspids is quite "V" 
 shaped, the apex of the "V" being between the cusps. 
 
 The distal surface closely resembles the mesial but is much more 
 convex. 
 
 Occlusal Surface (Fig. 22). — The outline of this surface on the upper 
 bicuspids is somewhat egg-shaped while on the lower bicuspids it is 
 more circular in form. It presents for study two cusps, a central groove 
 and a mesial and distal border. The cusps are placed buccally and 
 lingually, the buccal being the larger one. Each cusp has four inclines 
 or inclined planes, as they are usually called. These are named from 
 the surface toward which they slope, i. e., mesial, distal, buccal and 
 lingual. The groove runs mesiodistally and separates the cusps. The 
 mesial border is nearly straight while the distal border is decidedly 
 convex. Both of these borders are surmounted with ridges. 
 
 The Roots. — The upper first bicuspid has two roots. Of these the 
 buccal is the larger. All the other bicuspids have but one root. The 
 buccolingual dimension of the root is the greater. Its mesial and 
 distal sides are concave. A distal curve to the apex of the root is 
 common. 
 
 The Pulp Cavity. — The pidp chamber can be more readily outlined 
 in the bicuspids than in the incisors or cuspids. Its form follows 
 roughly that of the crown while the shape of the pidp canal corre- 
 sponds to that of the root. The upper first bicuspids have two pulp 
 canals, the other bicuspids usually have but one, although two may be 
 found. 
 
 Individual Characteristics of the Bicuspids. — The upper first is the 
 largest of the bicuspids. It has two roots and two root canals. 
 
 The lower first is the smallest of the bicuspids. Its lingual cusp is 
 very rudimentary. Its root is broad mesiodistally on the buccal side 
 and quite narrow on the lingual side. 
 
 The Upper Molars (Figs. 27 to 29). — The crowns of these teeth are 
 irregularly cuboidal, presenting the same five surfaces for study as do 
 the bicuspids. The crowns of the molars are smaller in diameter at 
 the neck than at their occlusal border. 
 
 The buccal surface is generally convex and is divided vertically by 
 a groove. Often in the center of this surface is a pit. When this is 
 present the buccal groove usually terminates in it. The buccal sur- 
 face has four borders. Of these the occlusal is the most striking in 
 that it is marked with two cusps. 
 
 The lingual surface resembles the buccal very closely except that 
 the mesial and distal margins converge more at the cervix as they 
 are continued into one root instead of two as is the case with the 
 corresponding margins of the buccal surface. 
 
THE ti<:i<:tii 
 
 Fig. 27. — Left upper first molar; buccal surface. (Johnson.) 
 
 Lingual 
 
 Fig. 28. — Left upper first molar; occlusal 
 surface. (Johnson.) 
 
 Fig. 29. — Left upper second molar; 
 lingual surface. (Johnson.) 
 
54 ANATOMY OF THE HEAD 
 
 The mesial surface at the occlusal third is convex while the gingival 
 two-thirds is straight or concave. 
 
 The distal surface is similar to the mesial, though perhaps in general 
 a little more convex. 
 
 The occlusal surface is irregularly rhomboidal, the acute angle 
 being the mesiobuccal and the distolingual. It presents four cusps, 
 two of which are buccal, called the mesiobuccal and distobuccal cusps, 
 and two lingual, called the mesiolingual and the distolingual cusps. 
 The mesiolingual is the largest cusp. Running obliquely across the 
 occlusal surface there is in succession a groove, a ridge, and a second 
 groove. The first groove begins in the middle of the mesial margin, 
 and passes distally and buccally across the occlusal surface to the inter- 
 val between the two cusps where it is continued over on to the buccal 
 surface as the buccal groove. The ridge runs from the mesiolingual 
 cusp to the distobuccal cusp. The second groove begins between the 
 two lingual cusps as a continuation of the lingual groove and runs 
 distally and buccally to the center of the distal margin. Just mesial 
 and distal to the center of the oblique ridge are fossce. 
 
 The Roots. — These are three in number, two being placed buccally 
 and one lingually. The lingual is the largest root and the distobuccal 
 the smallest. The apices of the two buccal roots tend to converge 
 toward each other. 
 
 The Pulp Cavity. — The outline of the pulp chamber resembles the 
 form of the crown. On the floor of this chamber are three openings 
 leading into the three root canals. 
 
 Individual Characteristics of the Upper Molars. — The first molar is the 
 largest of the upper molars. It is often distinguished by the fact that 
 it has a fifth cusp situated at the mesio-occlusal corner of the lingual 
 surface. This is very small and rudimentary. The roots of the first 
 molar are usually larger and diverge from one another to a greater 
 degree than in the other upper molars. 
 
 The second molar is often quite flattened mesiodistally. It never has 
 the fifth cusp. Frequently the buccal roots show a distal inclination. 
 
 The third molar, with the lower third molar, is the most variable 
 tooth in the head. If typical it should present but three cusps, the 
 distolingual being lost. It has no oblique ridge, but presents instead 
 a central fossa. There may be three roots or there may be but one, 
 and the root canals vary with the number and position of the roots. 
 
 The Lower First Molar (Fig. 30). — ^The crown of this tooth is also 
 irregularly cuboidal, and presents five surfaces for study. 
 
 The buccal surface differs from the buccal surface of the upper 
 molars in that it is longer mesiodistally and presents two grooves 
 instead of one. Its occlusal border is surmounted by three cusps 
 instead of two. 
 
 The lingual, mesial and distal surfaces all resemble the corresponding 
 surfaces of the upper first molar. 
 
 The Occlusal Surface (Fig. 31). — ^This differs considerably from the 
 
THE TEETH 
 
 55 
 
 corresponding surface of the upper. It is a trapezoidal in outline with 
 the long side buccally and is marked with five cusps, five grooves and 
 
 Fig. 30. — Right lower first molar; buccal surface. (Johnson.) 
 
 a central fossa. The cusps are arranged three buccally, named from 
 mesial to distal, mesiobuccal, buccal and distobuccal; and two lin- 
 
 Lingual 
 
 Fig. 31. — Right lower first molar; occlusal surface. (Johnson.) 
 
 gually, named mesiolingual and distolingual. The grooves radiate 
 from the central fossa and are named mesial, buccal, distobuccal 
 
56 
 
 ANATOMY OF THE HEAD 
 
 (between the buccal and distobuccal cusps), distal and lingual. The 
 mesiobuccal cusp is the largest and the distobuccal the smallest. 
 
 The Roots. — These are two in number and are placed one mesially 
 and the other distally and are known by these names. They present 
 a distal inclination. The mesial root is the larger. 
 
 The Pulp Cavity. — The pulp chamber resembles in outline the crown. 
 The pulp canals are frequently three in number there often being two 
 in the large mesial root. 
 
 The Lower Second Molar (Fig. 32). — This resembles the first lower 
 molar but is a smaller tooth and has but four cusps, the distobuccal 
 being absent. The cusp corresponding to the buccal cusp of the first 
 molar receives the name of distobuccal in the second molar. 
 
 Fig. 32. — Right lower second molar; lingual surface. (Johnson.) 
 
 The occlusal surface presents a central fossa and four grooves radiat- 
 ing from it. 
 
 The roots are somewhat smaller and are situated close together. 
 But two root canals is the usual order. The roots have a marked distal 
 inclination. 
 
 The Lower Third Molar. — This is extremely variable in form but 
 when tj-pical should resemble the second molar in miniature. 
 
 Descriptive Anatomy of the Deciduous Teeth. — The deciduous teeth 
 resemble the permanent teeth in their general form but are of course 
 much smaller. Their cusps are not as well defined and the form of the 
 
THE TEETH 57 
 
 molars and cuspids is such that they are larger at the neck than at the 
 occlusal border. 
 
 The incisors and cuspids are ver}' much like the corresponding 
 teeth in the permanent denture; the lower first molars quite closely 
 resemble the lower second permanent molars; the second molars, 
 both upper and lower, are similar in design to the upper and lower 
 first permanent molars; the uy per first molars, however, are different 
 in certain respects from any of the other teeth and therefore require 
 a more detailed description. 
 
 The Upper First Deciduous Molar. — The occlusal surface presents 
 three cusps, two buccally and one lingually. The latter is so large, 
 however, that it makes this side about as long mesiodistally as the 
 buccal. This surface presents a central fossa with three grooves 
 radiating from it, i, e., a mesial, a buccal and a distal. 
 
 The buccal surface resembles that of any upper molar; the lingual 
 is very convex and has no groove; the mesial and distal are convex 
 at their cervical borders. 
 
 Approximate Age at which the Various Teeth Erupt. — Lower teeth 
 erupt before the upper as a rule. 
 
 The Deciduous Denture. 
 
 Central incisors, 6th to 8th month. 
 Lateral incisors, 8th to 10th month. 
 First molars, 10th to 16th month. 
 Cuspids, 16th to 20th month. 
 Second molars, 20th to 30th month. 
 
 The Permanent Denture. 
 
 First molars, 5th to 7th year. 
 Central incisors, 6th to 8th year. 
 Lateral incisors, 7th to 9th year. 
 First bicuspids, 8th to 10th year. 
 Lower cuspids, 9th to 11th year. 
 Second bicuspids, 10th to 12th year. 
 Upper cuspids, 11th to 13th year. 
 Second molars, 12th to 14th year. 
 Third molars, 17th year to any time later. 
 
CHAPTER II. 
 
 HISTOLOGY OF THE TEETH AND ASSOCIATED 
 STRUCTURES.! 
 
 By ROBERT H. W. STRANG, M.D., D.D.S. 
 
 The Enamel.— This is the only calcified tissue in the body that is 
 derived from epithelial structures. All others have their origin in con- 
 nective tissue. Enamel is also the hardest of the tissues and contains 
 no organic matter. Chemically it is made up for the most part of 
 phosphate and carbonate of lime. As there is no organic matter to 
 be found in its make-up it must be designated as a dead tissue. The 
 epithelial cells that are active in its formation are destroyed when 
 their work is finished. Owing to the fact that enamel is of epithelial 
 origin any diseases that have among their symptoms eruptions of the 
 skin, such as the various contagious fevers of childhood, may produce 
 a disturbance of enamel formation if the attack comes at the age when 
 this tissue is being laid down. This accounts for many of the cases of 
 pitted and poorly formed enamel seen on the permanent incisor teeth. 
 
 Enamel is composed of two structural elements : (a) Enamel prisms 
 or rods, and (6) a cementing substance. 
 
 The Enamel Rod (Fig. 33). — These are prismatic in form, having 
 five or six sides and their average diameter is about one-half that of 
 a red blood corpuscle. Throughout their entire length we find them 
 alternately constricted and expanded. When placed side by side 
 these expansions and constrictions are not dovetailed into each other, 
 but are arranged opposite one another. 
 
 The Cementing Substance.- — Between the rods and filling up the 
 spaces made by this peculiar arrangement of the prisms, is the cement- 
 ing substance. This cementing substance is also highly calcified but 
 is more susceptible to injury than the prisms. When enamel cracks 
 the line of cleavage runs through the cementing substance and not 
 across the rods. When an acid is brought in contact with the enamel 
 the cementing substance is destroyed before the rods. 
 
 The enamel is formed from within outward so the enamel on the 
 surface of the tooth is the last to be laid down. The prisms extend 
 from the dentin outward and are arranged in a manner that will 
 best resist the force that is brought upon them as the teeth are used. 
 The prisms do not always run in a straight line from the dentin to 
 the surface but in many places, especially where the stress is great, 
 
 1 A resume from Dental Histology and Embryology by Dr. F. B. Noyes. 
 
The MameL 
 
 59 
 
 such as on tlie cusps of the teeth, they are intertwined with one anotlier 
 something like the strands of a rope. Such enamel is called gnarled 
 enamel. Straight enamel is that in which the prisms run in practically 
 a straight line from the dentin to the surface. 
 
 In sections of enamel two kinds of markings are distinguished on 
 the cut surface: (a) striation and (b) stratification (Fig. 34). The 
 striation is quite like that of voluntary muscle fibers and is due to 
 the alternating expansion and contraction segments of the rods. The 
 stratificatio7i is seen in longitudinal sections only. It consists of dark 
 bands running through the enamel. These bands are also called the 
 Bands of Retzius from the man who first discovered them. They are 
 due to pigment being deposited in the enamel as it is formed. A portion 
 
 Fig. 33. — Enamel rods in thin etched section. (About 800 X.) (Noyes.) 
 
 of the enamel having been formed, upon the surface of this is deposited 
 pigment. Following this another layer of enamel is laid down upon 
 which is deposited more pigment, etc. These lines of stratification are 
 therefore an index as to just how the enamel is laid down and show that 
 the first layer is deposited at the occlusal end of the crown and suc- 
 cessive layers work their way rootward. 
 
 When a tooth first erupts it is covered with a thin membrane called 
 Nasmyth's membrane. This is the remains of the enamel organ, active 
 during the formation of this tissue. It soon wears off as the tooth is 
 brought into use. 
 
 White or mottled spots are often seen in enamel. These are due to 
 the fact that the cementing substance has not been deposited between 
 
60 
 
 HISTOLOGY OF THE TEETH 
 
 the rods in these areas. The air spaces left by this failure cause a 
 difference in light refraction and make the spot appear opaque or whiter 
 than the surrounding tissue. 
 
 Functions of the Enamel. — (a) It covers the exposed portion of the 
 tooth and prevents irritation of the underlying sensative dentin. 
 
 (6) By its hardness it resists abrasion from the force of mastication. 
 Enamel differs from any other calcified tissue in the following details: 
 
 {a) It is formed by epithelial cells. 
 
 (6) It contains no organic material either in the form of cells or 
 intercellular substance. 
 
 Fig. 34. — Enamel showing both striation and stratification. (About 80 X.) (Noyes.) 
 
 (c) The organ that forms it disappears after its work is complete. 
 
 {d) It is made of prisms cemented together. All other calcified 
 tissue has fibrous connective tissue as its structural basis. 
 
 The Dentin (Fig. 35). — Dentin is a calcified connective tissue and 
 is used to make up the bulk of the tooth. It contains considerable 
 organic matter and yields gelatin when boiled. Its inorganic matter is 
 mostly carbonate and phosphate of lime. 
 
 Structurally dentin is made up of the following elements : 
 
 (a) Dentin matrix. 
 
 (6) The dentinal tubules with their walls which latter structures 
 are known under the name of the "sheaths of Neuman." 
 
 (c) The dentinal fibrils. 
 
THE DENTIN 
 
 61 
 
 Fig. 35. — Dentin showing tubules in cross-section: Dt, dentinal tubules; D, dentin 
 matrix; S, shadow of sheaths of Newman. (About 1150 X.) (Noyes.) 
 
 Fig. 36, — Dentin at dento-enamel junction, showing tubules cut longitudinally. 
 (About 760 X.) (Noyes.) 
 
62 HISTOLOGY OF THE TEETH 
 
 The Dentin Matrix. — This is a homogeneous material that is very 
 elastic. As seen with the unaided eye it is yellowish. It is composed 
 of about one-third organic material and two-thirds inorganic in the 
 form of lime salts. 
 
 The Dentinal Tubnles. — Extending throughout the matrix and radi- 
 ating from the pulp cavity are minute tubes. These take a spiral 
 course in their passage through the matrix. They also intercommuni- 
 cate with one another. They end at the dento-enamel or dento- 
 cemental junction. At the former junction they branch close to their 
 termination in delta-like formations (Fig. 36). These deltas are in 
 communication with one another. This intimate interconnection of 
 many tubules explains why the dento-enamel junction is such a sensitive 
 area under the action of instruments. At the dento-cemental junction 
 the tubules open into spaces lying between the cementum and the 
 dentin. These spaces, ranging as they do along the whole length of the 
 root, form what is known as the "granular layer of Tomes" (Fig. 37). 
 Although several investigators have claimed that they have found 
 communicating channels between the granular layer of Tomes and the 
 canaliculi of the cementum, Dr. Noyes states very definitely that he 
 has never been able to demonstrate this fact. 
 
 The matrix immediately surrounding the tubules is of a more dense 
 composition than that in other parts. This densely formed portion 
 receives the name of the sheath of Neuman. The name is somewhat 
 misleading for it is not a true membrane, but is undoubtedly a special- 
 ized portion of the matrix itself forming a wall, as it were, to the tubes. 
 It has been found that the sheaths of Neuman have considerable 
 elastin as one of their component elements. 
 
 The Dentinal Fibrils. — These are the protoplasmic processes found in 
 the tubules and are extensions from the cells of the pulp that were 
 active in the formation of the dentin. These cells are called odonto- 
 blasts. 
 
 Function of the Dentin. — (a) Forms the great bulk of the tooth. 
 
 (b) Acts as an elastic cushion to the enamel so that this tissue will 
 not break under stress. 
 
 (c) Gives strength to the whole tooth. 
 
 The Cementum (Fig. 37). — This is also a calcified connective tissue. 
 It more nearly resembles bone than does the dentin. It is arranged 
 in consecutive layers around the tooth root and slightly overlaps the 
 enamel at the cervical margin. 
 
 Structurally cementum is made up of the following elements : 
 
 (a) The lamellae. 
 
 (b) The lacunae from which radiate the canaliculi. 
 
 (c) Cement cells or corpuscles. 
 
 (d) The embedded fibers of the peridental membrane. 
 
 The LamelloB. — This is the name given to the layers of cementum. 
 These vary in thickness according to the position on the root, being 
 thinnest at the gingival margin and thickest at the apex. They are 
 
THE CEMENTUM 
 
 63 
 
 arranged concentrically about the root. There is a continuous forma- 
 tion of cementum going on throughout life so that the older the indivi- 
 dual, the more layers of cementum there will be. By virtue of this 
 property of continuous formation the cementum is the one tissue of 
 the tooth that is capable of repairing itself after injury. Destruction 
 of the dentin on the surface of the root may also be repaired by the 
 cement cells filling in such areas with cementum. 
 
 Fig. 37. — Two fields of cementum showing penetrating fibers: GT, granular layer 
 of Tomes; C, cementum not showing fibers; F, penetrating fibers. (About 54 X.) 
 (Noyes.) 
 
 The Lacunoe. — ^The lacunse are minute spaces scattered throughout 
 the cementum, being both in the substance of the lamellse and between 
 the various layers. From these radiate in all directions minute canals 
 called canaliculi. These canaliculi intercommunicate with those 
 from the adjacent lacunae. The cement cells or corpuscles lie in the 
 
64 HISTOLOGY OF THE TEETH 
 
 lacunae. They are the cells that are active in the formation of cemen- 
 tum. Their protoplasmic processes extend into the canaliculi. 
 
 The Embedded Fibers of the Peridental Membrane. — ^The cement 
 cells previous to the formation of cementum are located in the mem- 
 brane that surrounds the root, the peridental membrane. The cement 
 is built from within outward, i. e., that nearest the dentin is the first 
 to be formed. As these cells, called cementoblasts when active, form 
 the various lamellae they build themselves into the structure that they 
 are forming. In this process many of the fibers of the peridental 
 membrane are also built into the cementum and after a time become 
 more or less calcified. These constitute the embedded fibers. 
 
 On the opposite side of the peridental membrane, i. e., that side 
 that is in relationship to the bone of the alveolus, we find that fibers 
 of the membrane are similarly built into the bone. Through the agency 
 of all these embedded fibers the tooth is firmly held in its socket. 
 
 The Function of the Cementum. — It is the tissue which through its 
 ability to attach the tooth to the surrounding connective tissue, holds 
 it in position. The cementum may therefore be considered as the 
 most important of the tooth tissues. 
 
 The Pulp. — This is the structure occupying the cavity within the 
 dentin. It represents the remains of the organ that was active when 
 the dentin was formed. 
 
 Structurally the pulp is made up of the following elements : 
 (a) Odontoblasts. 
 (6) Connective-tissue cells. 
 
 (c) Intercellular tissue. 
 
 (d) Bloodvessels. 
 
 (e) Lymphatics. 
 (/) Nerves. 
 
 The Odontoblasts (Fig. 38). — These are the specialized connective- 
 tissue cells that form the dentin. They lie along the periphery of 
 the pulp in contact with the dentin walls and send long protoplasmic 
 processes into the dentinal tubules. These processes have the prop- 
 erty of transferring sensations of pain to the nerve fibrils within the 
 pulp. 
 
 The Connective-tissue Cells. — These are stellate in form and resemble 
 the connective-tissue cells in young, growing tissue. They are scattered 
 throughout the pulp tissue. 
 
 The Intercellular Substance. — This is quite structureless and gelat- 
 inous in character. Scattered everywhere through it are the cells 
 just described. 
 
 The Bloodvessels (Plate II). — These enter the tooth through the 
 apical foramen and the larger vessels travel through the center of the 
 pulp, giving off many branches. These break up into capillaries which 
 form a rich network about the periphery of the pulp. From these the 
 blood is collected by veins that run with the arteries and pass out 
 through the foramen. The walls of the bloodvessels in the pulp are 
 
THE PULP 
 
 65 
 
 extremely thin even in the arteries and larger veins. This condition 
 renders the tissue particularly susceptible to inflammation. 
 
 The Lymphatics (Fig. 39). — llecently Dr. Noyes has succeeded in 
 demonstrating that there are lymphatic vessels in the pulp. These are 
 connected through the apical foramen with lymphatic vessels that 
 pass through bony spaces to the mandibular canal in the lower jaw 
 and to the infra-orbital canal in the upper and then emerge from the 
 mental or infra-orbital foramina and join the lymphatic vessels accom- 
 panying the facial artery and vein. They empty into the submaxillary 
 lymph nodes. As the lymphatic capillaries pass through the apical 
 space after emerging from the tooth root they are joined by vessels 
 that come from the gums and peridental membrane so that there is a 
 most complete lymphatic anastomosis between the gums, the peri- 
 dental membrane and the pulp. 
 
 Fig. 38. — Odontoblasts. The section cuts obliquely through the odontoblasts. 
 F, fibrils; A^, nuclei of odontoblasts; N', nuclei of connective-tissue cells; W, layer of 
 Weil, not well shown. (About 80 X.) (Noyes.) 
 
 The Nerves. — Several trunks enter the tooth through the apical 
 foramen and run through the center of the pulp giving off branches. 
 These branches pass to the periphery and form a network at the 
 base of the odontoblasts and secondary arborizations around each 
 odontoblast. None of the nerve fibrils enter the tubules in the dentin. 
 Sensation in the dentin is due, therefore, to the irritation of the proto- 
 plasmic processes of the odontoblasts which transfer these irritations 
 to the nerve fibers in physiological contact with them. 
 5 
 
66 
 
 HISTOLOGY OF THE TEETH 
 
 Function of the Pulp^ 
 
 (a) The formation of dentin. 
 
 (6) A sensory function. It responds to heat and cold, and also 
 gives the sensation of pain when irritated. 
 
 Secondary Dentin. — This is dentin that is sometimes formed after 
 the normal amount of dentin has been laid down and the pulp has 
 ceased to functionate. It is due to irritation of the pulp by some 
 external agent and this organ responds by attempting to again perform" 
 the duties for which it was designed. 
 
 r- 
 
 
 
 
 ' 
 
 v_ 
 
 
 I ' 
 
 
 ; " 
 
 r 
 
 
 *W 1 •« 
 
 1 
 
 
 
 } 
 
 
 I 
 
 ^ 
 
 % 
 
 
 
 
 
 ■ ""ft 
 
 J 
 
 
 ^- 
 
 / ■ 
 
 
 
 ^ 
 
 ^'^'/ 
 
 
 i 
 
 '.% 
 
 *i*r 
 
 Fig. 39. — Transverse section just at the apex of the root, showing injected lymphatic 
 vessels in the peridental membrane and in the canals passing to the pulp (oc, 2; obj., 
 16 mm. ; reduced one-third). (Noyes.) 
 
 The Attachment of the Teeth. — As has been previously stated, the 
 teeth are not to be considered a part of the osseous system of the 
 body, as they bear no relation to it from a point of origin. Of what 
 system then are they a part? It has been clearly proved that these 
 organs are appendages of the skin that have through the processes 
 of evolution become highly specialized into the form that we see them 
 in the various animals and in man. The simplest form of tooth is 
 seen in some of the fishes. It consists of a cone of enamel covering 
 a calcified connective-tissue papilla containing tubules and closely 
 simulating dentin. This in turn rests upon a second mass of calcified 
 connective tissue like unto the cementum. Into this latter structure 
 
THE PERIDENTAL MEMBRANE 67 
 
 the fibers of the underlying tissue are built. To such a simple form of 
 tooth no bone is in any way related. In the attempt to find from what 
 structures the teeth were evolved it was noted that the dermal scales 
 on the bodies of certain fish, i. e., the shark and sturgeon, were but 
 duplicates of the simple forms of teeth just described. This fact, 
 together with other sufficient proof, left no question but that the teeth 
 were really dermal appendages that had migrated into the mouth. 
 
 From this simple form of tooth attachment by fibrous tissue to 
 underlying soft parts there are numerous variations of form and 
 methods of attachment according to the work that the individual 
 requires of his teeth and the amount of force exerted upon them in 
 doing this work. So it is noted that as the food upon which an animal 
 subsists becomes harder, the attachment of the teeth becomes firmer. 
 To combat the force of displacement, roots were evolved and bone 
 developed about them until the perfected form of support, as seen 
 in man, was reached. 
 
 At first thought it might seem that the strongest way in which to 
 hold a tooth in place would be to build the bone immediately against 
 the root so as to lock the tooth absolutely in position. If this were 
 done, however, the slightest blow upon the crown of a tooth would 
 either fracture it at the gingival margin or so severely shock the pulp 
 that its life would be forfeited. Furthermore, the transmission of 
 the force of mastication to the bones of the head under such favorable 
 conditions would be productive of severe traumatic shock to the brain. 
 Nature avoids all of this by placing between the root of the tooth and 
 the bone of the alveolar process a fibrous membrane, the function of 
 which is to literally suspend the tooth in its socket. Thus it not only 
 retains the tooth perfectly but also acts as a cushion. This membrane 
 is called the 'peridental membrane and may be considered as the most 
 important of all the dental tissues. Why? Because it makes no dif- 
 ference how perfectly formed a tooth is or how carefully its contour 
 be restored by dental operations correcting the ravages of caries, if 
 this membrane, that bears all the stress during mastication, is not in 
 perfect health, that tooth will be proportionately useless. 
 
 The Peridental Membrane. — Definition. — ^The peridental membrane 
 may be defined as that tissue which fills the space between the surface 
 of the root and the bony wall of its alveolus, surrounds the root occlu- 
 sally, from the border of the alveolus, and supports the gum. (Noyes.) 
 
 From this definition it will be noted that this membrane not only 
 covers that portion of the root that is within the alveolus but also 
 that part between the top of the alveolus and the gingival line. Indeed 
 this latter portion may be considered as the most important part of 
 the membrane, because it is here that the initial lesions which eventually 
 lead to the loss of the tooth, occur. 
 
 Structurally the peridental membrane is made up of the following 
 elements : 
 
 White fibrous connective tissue, 
 
68 HISTOLOGY OF THE TEETH 
 
 Four varieties of cells : 
 Fibroblasts. 
 Cementoblasts. 
 Osteoblasts. 
 Osteoclasts. 
 Bloodvessels. 
 Lymphatics. 
 Nerves. 
 
 Epithelial structures. 
 The White Fibrous Connective Tissue. — A careful study of the distri- 
 bution of this tissue is of absolute necessity if one is to realize the 
 important role that the peridental membrane plays in maintaining 
 the tooth in a functionating condition. 
 
 The fibrous tissues may be divided into two classes of fibers: (a) 
 The principal and (6) the indifferent. The first group is the one 
 concerned in the support of the tooth; the other fibers simply fill 
 the spaces between the principal fibers and support the bloodvessels, 
 lymphatics and nerves. 
 
 The Principal Fibers. — These are built into the cementum in the 
 form of fairly large bundles. Upon emerging from the cementum 
 they break up into smaller bundles, bridge across the interspace and 
 are again gathered together to be built into the bone of the alveolar 
 process or distributed to support the gum. This is the general arrange- 
 ment. The direction, however, that these fibers take as they pass 
 from their point of origin in the cementum to their insertion in the 
 bone or gum is modified in various parts of the membrane and is in 
 definite relation to the force brought to bear upon the tooth as it per- 
 forms the work of mastication and upon the pressure exerted against 
 the supported gum tissue. This adaptation is the more perfect in 
 that this arrangement is the result of this force and the force not 
 secondary to the building of the fibers. This is demonstrated more 
 clearly perhaps if it is borne in mind that the cement-building cells 
 are constantly at work shifting the attachment of fibers whenever 
 there is a change in the direction of force exerted on the tooth. If the 
 tooth is changed in position, the arrangement of the fibers of the mem- 
 brane will be varied to accommodate any changes in the force of 
 mastication. 
 
 For the purpose of studying the arrangement of the principal fibers, 
 the membrane may be divided into three segments : (a) The gingival, 
 that part between the border of the alveolar process and the, gingival 
 margin; (b) the alveolar, that part situated between the border of 
 the process and the apex; and (c) the apical, that portion in relation 
 to the apex of the root (Fig. 40). 
 
 Arrangement of the Fibers in the Gingival Portion (Plate III). — There 
 are four sets of fibers in this area. The first group arises from the highest 
 point of attachment occlusally on the root, passes from this at more or 
 Jess of a right angle, then takes an occlusal curve and passes into the 
 
PLATE III 
 
 ''.' ~l'''V'V 
 
 %lt v-l. 
 
 Longitudinal Section of Peridental Mennbrane. (Noyes.) 
 
 Stained with hematoxylin and eosin. Showing part of the lingual gingivus and 
 border of the alveolar process. 
 
THE PRINCIPAL FIBERS 
 
 69 
 
 gum tissue to be lost aiiKMig the fibers of the conneetive tissue that 
 supports the epithelium of the mucous membrane. 
 
 Fig. 40. — Diagram of the fibers of the peridental membrane: G, gingivaljportion ; 
 AL, alveolar portion; Ap., apical portion. (From a photograph of a section from 
 incisor of sheep.) (Noyes.) 
 
 The second group arises from an area just below the fibers of the 
 first group, passes out from the cementum at right angles and continues 
 
70 
 
 HISTOLOGY OF THE TEETH 
 
 for sufficient distance into the gum tissue to give this perfect support. 
 On the Ungual side these fibers run a longer course than on the labial 
 because the lingual gum receives a greater shock in chewing than does 
 the labial. The distribution of this group of fibers on the approximal 
 side is of extreme importance (Fig. 41) . Here they pass across the inter- 
 vening approximal space to the adjoining tooth and are built into the 
 cementum of this tooth. Each tooth receives and gives off fibers on 
 the approximal side which are built into its cementum. These, as they 
 
 Fig. 41. — Transverse section of the peridental membrane in the gingival portion 
 (from sheep) : E, epithelium ; F, fibrous tissue of gum ; B, point where peridental mem- 
 brane fibers are lost in fibrous mat of the gum ; P, pulp ; F', fibers extending from tooth 
 to tooth. (About 30 X.) (Noyes.) 
 
 pass across the space, are closely interwoven, forming a basket-work 
 structure that supports the overlying gum in a most perfect manner. 
 The third grouy. A little more rootward to the second group is another 
 set of fibers that soon after passing from their attachment in the 
 cementum are inclined apically. These form a very strong bundle 
 of fibers. On the labial and lingual sides they pass to the outer sur- 
 face of the alveolar process and are attached to the periosteum cover- 
 ing the bone here. On the proximal side they either pass to the 
 cementum of the adjoining tooth or are built into the upper surface 
 
THE CELLS 71 
 
 and sides of tfie bone that intervenes between the teeth. These fibers 
 resist any force that tends to pull the tooth from its socket. They 
 form what is known as the dental ligament. 
 
 The fourth gnnqj are arranged like a constrictor muscle around the 
 gingival margin and keep the gum tissue in close contact with the 
 neck of the tooth. 
 
 Arrangement in the Alveolar Portion (Fig. 40). — Here are found three 
 areas of variation in direction of the fibers. First: The fibers coming 
 off from the cementum at the level of the top of the alveolar process 
 pass at right angles across the intervening space to be inserted into the 
 bony walls of the process. This arrangement is continued down the 
 root of the tooth nearly one-third of the distance to the apex. These 
 fibers arise from the cementum in strong bundles and then break up 
 into fan-like forms as they cross the space to be inserted into the bone. 
 In transverse sections of the root at this level it is noted that the fibers 
 that come off from the angles of the roots do not pass immediately 
 across the space but are deflected to right and left. These are the 
 fibers that resist any force that tends to rotate the tooth in its 
 socket. 
 
 Second: As the lower portion of the previously considered area is 
 approached the fibers, after leaving the cementum, begin to pass 
 occlusally and are inserted somewhat higher up on the wall of the 
 alveolus. This arrangement is continued until the apical end of the 
 tooth is reached. This area is large and the fibers are strong because 
 they have to resist the greatest force exerted in mastication, i. e., 
 the thrust force as the jaws are closed. By these fibers the tooth 
 is actually suspended in its alveolus. 
 
 Third: At the lower portion of the apical third of the root the 
 fibers again begin to take a more direct course from the cementum 
 to the bone until they are passing directly across, as noted in the upper 
 third. 
 
 The Arrangement in the Apical Portion (Fig. 40). — Here the fibers 
 after passing from the cementum radiate in all directions before being 
 inserted into the bone. In this way the apical space is filled with a 
 mass of fibrous tissue. 
 
 The Cells. — Fibroblasts. — These are the cells that have formed 
 the fibers and are looking after their welfare. They are scattered 
 throughout the entire membrane. 
 
 Cementoblasts. — These are the cementum-forming cells and lie in 
 contact with this tissue between the points of origin of the fibers. 
 As they form the cementum some of the cells surround themselves 
 with it and then take the name of cement cells or corpuscles. They 
 also build into the cementum the fibers of the membrane. 
 
 Osteoblasts. — These are the bone-forming cells and have their station 
 on the bony walls of the alveolus. They are active in forming the bone 
 of the alveolar process that is in juxtaposition to the roots of the 
 teeth. They too become bone cells when they have surrounded 
 
72 HISTOLOGY OF THE TEETH 
 
 themselves with this tissue. The attachment of the fibers of the 
 membrane into the bone is performed by these elements. 
 
 Osteoclasts. — These are the cells that eat away the bone or cemen- 
 tum when there is a demand for this process. Through their action 
 the fibers of the membrane are detached at any given area. This 
 occurs during the absorption of the roots of the deciduous teeth and 
 it is these cells that are responsible for this process. They are also 
 used when nature believes that the bone in any given place is too 
 thick and heavy for the strain brought to bear upon it. If so, these 
 cells are brought into activity and destroy the thick bone by forming 
 marrow spaces within it. This occurs in the formation of the alveolar 
 process and accounts for its cancellous or spongy character. 
 
 Bloodvessels (Plate II), — The peridental membrane has a very rich 
 supply of blood. The arteries enter the apical space from the bone 
 beneath. They then give off branches which pass into the pulp cavity 
 to supply the organ therein. The main branches pass occlusally in all 
 directions through the peridental membrane. They lie nearer the wall 
 of the alveolus than the cementum. As they pass upward they receive 
 from and give off branches to the bone of the alveolar walk They 
 end by anastomosing with the bloodvessels of the gum tissue and 
 help supply this area. From this it is noted that the blood supply 
 of the gums and peridental membrane is intimately related so that 
 stimulation of gum tissue by massage and brushing will in turn stimu- 
 late the peridental membrane — a fact that is of the greatest impor- 
 tance in the treatment of lesions of this latter structure. 
 
 Lymphatics (Fig. 42). — It has been shown that the peridental mem- 
 brane is well supplied with lymphatic vessels which ramify through the 
 membrane very much as do the bloodvessels. Small lymphatic capil- 
 laries also run from the gum margin and anastomose with the vessels 
 in the peridental membrane. In the region of the root apex the lymph 
 channels of the peridental membrane are joined with those from the 
 pulp and these larger vessels pass through the bone spaces to the main 
 trunks in the mandibular or infra-orbital canals as described under the 
 lymphatics of the pulp. 
 
 The Nerves, — These have the same point of entrance and the same 
 distribution as the bloodvessels that have just been described. It is 
 important to note that these nerves give to the peridental membrane 
 the sense of touch. This sense is well developed, for the lightest con- 
 tact is immediately recognized. 
 
 Epithelial Elements. — As the function of these structures is still a 
 mystery it is sufficient in this text to note that such tissues are present 
 but that their real significance still remains unknown. 
 
 The function of the peridental membrane. 
 
 (a) A physical function, i. e., the maintaining of the tooth in the 
 socket, 
 
 (6) A vital function, manifested through the agency of its cells in 
 the formation of cementum and bone. 
 
CHANGES IN THE MEMBRANE WITH AGE 
 
 73 
 
 (c) A sensory functicju in that it supplies the sense of touch to the 
 tooth. 
 
 Changes in the Membrane with Age. — When the tooth first erupts 
 the space between the root and wall of the alveolus is relatively wide. 
 Each year finds this becoming smaller and smaller because of the 
 formation of new lamellae of cementum on the one side and of bone 
 on the other. The peridental membrane grows proportionately thinner 
 
 Fig. 42. — Unstained section, showing lymph capillaries of the tooth side of the 
 gingivae and their drainage through the ligamentum circulare to the peridental mem- 
 brane. (Noyes.) 
 
 as it is thus encroached upon. However, there is always a membrane 
 present no matter what the age of the individual may be. In other 
 words, the bone and cementum never come in immediate contact with 
 each other. This thinning of the membrane makes it less resistant 
 to irritations and so predisposes inflammatory conditions. Hence 
 diseases of the peridental membrane are more frequently found after 
 adolescence. 
 
74 HISTOLOGY OF THE TEETH 
 
 The Alveolar Process. — As has been previously emphasized, the bone 
 of this process is built secondary to the formation of the teeth or rather 
 coincident to their eruption. It is a product of function and is 
 arranged as to its structure in a way that will best resist the forces 
 that are brought to bear upon it. In the upper jaw we find a dense, 
 hard layer of bone about the necks of the teeth labially and buccally. 
 In the incisor and cuspid region where much force is exerted upon the 
 whole length of the roots the bone is quite thickened over their entire 
 labial surfaces. This is well demonstrated in those lower animals that 
 use these teeth for seizing and tearing their prey. Over the buccal 
 roots of the bicuspids and molars it is very thin. Lingually, all the 
 teeth of the upper arch are well supported. 
 
 In the lower arch again is found the compact bone about the necks 
 of the teeth and their roots well supported buccally, as most of the 
 strain is in this direction. 
 
 The great mass of bone of both the maxilla and the mandible is 
 made up of the cancellated variety about the periphery of which is a 
 layer of thick, dense bone. The wall of each alveolus joins this thick- 
 ened layer at its upper border. Below this point of union the wall 
 of the alveolus is surrounded with cancellated bone so that the alveolar 
 process as a whole is quite elastic and springy. In connection with 
 our reference to bony tissue it is well to mention the fact that this is 
 living tissue, a specialization of the connective tissues, adapted for 
 perfect support and that it is ever throughout life undergoing constant 
 change as a result of the mechanical forces brought to bear upon it. 
 By virtue of the ability to make such changes, nature is able to meet 
 any requirement that is demanded, even though it be far different from 
 the original condition for which the bone was built. So in examining 
 a specimen of bony tissue under the microscope various forms of bone 
 cell activity are seen going on, representing different stages of bone 
 formation and absorption. 
 
 The Gums. — The soft tissue overlying the alveolar processes is 
 known as the gums. It is composed of mucous membrane under 
 which is a submucous tissue which lies on and is firmly attached to the 
 periosteum of the bony process. The cells of the epithelial layer of the 
 mucous membrane are cornified. 
 
 The gum tissue about the necks of the teeth is supported and held 
 in position by fibers from the peridental membrane which pass from 
 the cementum into the submucosa. The bloodvessels and lymphatics 
 of the gums anastomose freely with those of the peridental membrane. 
 vStimulation of the circulation in the gum tissues therefore also causes 
 a free flow of blood through the peridental membrane a factor of much 
 importance in maintaining the health of this membrane. On the other 
 hand this free anastomosis gives excellent opportunity for infection 
 of the peridental membrane from gum lesions or even for systemic 
 infection. 
 
TOOTH FORMATION 
 
 75 
 
 Tooth Formation. — The first sign of the formation of teeth is seen 
 in the embryo at about two and a half months. Ahjng the top of each 
 arch (upper and h>wer) there is seen a heaping up of the cells of the 
 outer layer of tissue. If a cross-section is made of the arch, it will be 
 noted that these cells are also dipping down into the underlying tissue. 
 This formation is known as the dental ridge. From the lingual side 
 of this ridge a shelf -like growth is formed called the lamina (Fig. 43). 
 At intervals along the lamina, corresponding to the location of each 
 tooth, little buds grow from it. The under surface of these buds 
 becomes indented, taking on the appearance of an inverted cup. This 
 cup-like structure is now known as the ena^nel organ (Fig. 44), and 
 will soon begin to lay down enamel along its inner surface. The cells 
 
 Fig. 43. — The dental ridge and dental lamina 
 
 lining this surface are the enamel cells or ameloblasts and are active 
 in the formation of this substance. The enamel organ is of epithelial 
 tissue origin. 
 
 As the enamel organ is forming, the cells of the tissue into which it 
 grows begin to take on activities. As fast as the infolding of the 
 base of the enamel organ takes place the indentation is filled in with 
 these active underlying tissues until a papilla is formed. This is known 
 as the dental 'papilla (Fig. 44) . This structure is of connective-tissue 
 origin and will become active in the formation of the dentin. Growth 
 of the papilla continues until it has assumed the shape of the crown of 
 the tooth to be formed. To this structure formed by the enamel organ 
 and dental papilla is given the name of tooth germ. 
 
76 
 
 HISTOLOGY OF THE TEETH 
 
 After the dental papilla has been formed, the cells at its base develop 
 fibrous tissue which grows up and around the outer side of the enamel 
 organ and over its top so that the tooth germ is enclosed in a fibrous 
 sac. This combination of structures, i. e., the fibrous wall, the papilla 
 and the enamel organ constitutes the dental follicle. This is completed 
 by the end of the twelfth week. 
 
 Fig. 44. — The enamel organ. The outer tunic connected to the lamina by the cord; the 
 dental papilla growing up into the cap. The spaces are shrinkage spaces. (Noyes.) 
 
 Just before the enclosure takes place a secondary bud is given off 
 from the enamel organ, usually near its point of origin from the lamina, 
 which grows downward to become the enamel organ of the permanent 
 tooth (Fig. 45). 
 
 Soon after the formation of the dental follicle the bone of the jaw 
 below this structure sends up processes which pass to the lingual and 
 labial side of the follicle. Later bony growth appears on the proximal 
 sides and finally the top is covered over. This bony structure is what 
 is known as the dental crypt and simply serves as a protection to the 
 forming tooth. The dental crypt persists until the entire crown is 
 
TOOTH FORMATION 
 
 77 
 
 developed and the tooth ready to erupt when the top is absorbed 
 and the tooth passes into the mouth. 
 
 At about the sixteenth week the dentin and the enamel begin to 
 form, the former on the outer edge of the dental papilla and the latter 
 on top of this dentin. 
 
 Fig. 45. — The tooth germ showing the bud for the permanent tooth at P. Calci- 
 fication is just beginning; /?', follicle wall; D, dental papilla; T, inner tunic; T', outer 
 tunic; S, stellate reticulum; O, odontoblasts; A, ameloblasts; B, bone. (Noyes.) 
 
 The roots of the teeth do not appear until the tooth begins to take 
 on the process of eruption. At this time also the first of the cemen- 
 tum is seen. This is formed by cells in that fibrous tissue that grew 
 up and around the enamel organ to complete the follicle. This fibrous 
 tissue now may be considered as the peridental membrane. Coinci- 
 dent with the formation of cementum by the cells on the inner side 
 
78 HISTOLOGY OF THE TEETH 
 
 of this membrane there is a deposit of bone laid down by the osteo- 
 blasts on the other side of the membrane. This is the beginning of 
 the alveolar process. 
 
 The first permanent molars are the only permanent teeth for which 
 the enamel organ arises directly from the lamina. The enamel organs 
 for the second and third permanent molars arise from the buds, of 
 the first and second permanent molars respectively. 
 
 Fig. 46. — Front view of skull. Note the relation of the permanent incisors and cuspids 
 to each other and the roots of the temporary teeth. (Noyes.) 
 
 THE DEVELOPMENT OF THE JAWS. 
 
 While it is impossible in the space alloted this subject to go into 
 detail regarding the growth of the jaws, yet it is quite necessary 
 that the dental hygienist should know briefiy the plan upon which 
 nature builds under normal conditions. For an exhaustive study 
 
THE DEVELOPMENT OF THE JAWS 79 
 
 of this subject the student is referred to Dr. Noyes's text-book, 
 Dental Histology and Embryology. 
 
 In a comparison of the skull of an infant at birth with that of an 
 adult it is noted that as growth proceeds there is practically twice 
 as much development below the nasal spine of the frontal bone as 
 above it. This great downward growth takes place mostly in the 
 region of the mouth and is due primarily to the formation and sub- 
 sequent eruption of the teeth, and secondarily to a continued growth 
 of bone thrown out to act as a supporting structure for these organs 
 (Fig. 46) . This downward growth begins with the eruption of the de- 
 ciduous denture and continues until all the permanent teeth anterior to 
 the first molars are in position. After the completion of the deciduous 
 denture two new directions of growth manifest themselves, a lateral 
 or expanding growth to allow for the difference in size between the 
 teeth of the deciduous and permanent dentures, and a forward one 
 to make room for the developing permanent molars. Hence we note 
 that the growth and development of the jaws takes place in three 
 directions, i. e., a vertical growth, which is downward in the upper 
 jaw and upward in the lower and is coincident with tooth eruption; 
 a lateral growth; a forward growth. This development continues until 
 all the teeth are in position and occlusion is established. 
 
CHAPTER III. 
 THE TEETH AS A MASTICATING MACHINE. 
 
 By CHARLES R. TURNER, M.D., D.D.S. 
 
 An analysis of the reasons for preserving the teeth gives first impor- 
 tance to their preservation that they may perform their fmictions as 
 a part of the human organism, and play their part in that sum total 
 of activities which go to make up the physical life of the human 
 animal. As so much attention is now being given to the matter of 
 tooth conservation it is proper to be informed as to the important 
 part taken by the teeth in one of the most essential of the distinctive 
 animal functions, indeed, one which is necessary to the preservation 
 of life itself. Furthermore, it is one of the dictums of physiology 
 that any part of the body which ceases to perform its functions atro- 
 phies, or the character of its tissues degenerates, and in course of 
 time is incapable of performing its function; and so the duties of the 
 teeth have a twofold interest for us. 
 
 In order then to present the case for the preservation of the teeth, as 
 it were, something must be said about their functions in the human 
 body, and in that connection as a machine, or as a part of a machine, 
 concerned in the preparation of the food for subsequent stages in the 
 digestive process. 
 
 To appreciate fully the part taken by the teeth in the activities of 
 the human organism, it might be interesting, and it will certainly 
 give a good background for the study of the human dental mechan- 
 ism, to take some account of the way the teeth have developed to 
 perform their present functions. 
 
 The basal functions of animal as distinguished from plant life, and 
 as fundamental to existence itself, are: 
 
 1. Alimentation. 
 
 2. Respiration and circulation. 
 
 3. Locomotion. 
 
 4. Reproduction. 
 
 Evolution of Tooth Forms. — ^In the simplest form of animal life, as 
 for example in a unicellular body, the ameba, we have the process of 
 alimentation, or the securing of nutrition, an extremely simple one. 
 The animal is afloat in the water and extracts its nutriment there- 
 from, the nutritive elements are absorbed through the cell wall and 
 nutrition is effected through a simple process of osmosis. 
 
 No one fact so impresses the student of zoology as the relation- 
 
EVOLUTION OF TOOTH FORMS 81 
 
 ship between the form and structure of the various parts of an animal 
 organism and the functions they are called upon to perform. It is 
 very interesting to note the adaptive moflification of the structures 
 to changes in these bodily functions, and to observe how they have 
 been modified during the various stages in the development from 
 the lowest organisms up to the highest forms. 
 
 As the scale of animal life is ascended and a multiplication of func- 
 tions occurs, differentiations of tissue appearing here and there are 
 found, which occur as a result of a certain function falling upon that 
 tissue. Certain cells are given over to the function of reproduction; 
 certain other cells or collections of cells are specialized for locomotion, 
 etc. 
 
 In some of the lower forms of animals, before the vertebrates, there 
 is a simple tube like a channel devoted to alimentation; the food goes 
 in one end and the excreta are ejected at the other. There is no 
 special collection of cells at the beginning of this tube to prepare the 
 food. In the ccBlenterata, for example, the alimentary canal is not 
 separate from the general body cavity, but in the annuloida and 
 annulosa it is a distinct tube. 
 
 A little higher in the scale, as in some of the insects, the crabs and 
 the crustaceans, there are, at the beginning of this alimentary tract, 
 cells which are concerned to some extent with the preparation of the 
 food for its passage through the canal. There is no real masticating 
 apparatus, however, even in many of the lowest of the vertebrate 
 animals, but the first thing that at all appears like it occurs in some 
 of the lower fishes, in the hag-fishes and in the lamprey eels. The 
 latter have a suctorial mouth which they attach to some object, 
 either the side of a larger fish or a stone covered with moss, and 
 obtain their nutrition from it by a process of suction. Inside of this 
 mouth are layers of cells which are rather horn-like in character. 
 They are for the purpose of imbedding themselves in the substance to 
 which the mouth is applied and of affording a firm hold so that the 
 animal may draw its sustenance. This is perhaps the very simplest 
 type of differentiation of tissue for this purpose. 
 
 In the vertebrate animals the cells constituting the tissues at the 
 entrance of the alimentary canal are specialized with a view to assist 
 ing in the process of either securing or preparing the animal's food. 
 The apparatus is simple in the less highly developed orders and 
 becomes a more complicated instrument as the scale is ascended. 
 The food convenient to the animal or required by it, and the food- 
 reducing mechanism are in constant correspondence. Out of this 
 necessity has developed teeth. The teeth have developed in accord 
 with and to meet the needs of the food which the animal utilizes. 
 They are corneal or horn-like in some of the lower orders and as we 
 go upward they become calcified. They are simple cones or they 
 are modified under certain conditions to forms which serve better 
 their functions. 
 
82 THE TEETH AS A MASTICATING MACHINE 
 
 Fishes are the lowest vertebrate type that have calcified teeth; 
 they are simply calcified cones arranged around the border of the 
 jaws and serve to hold the food. Some of the teeth are recm-ved 
 and serve like the barb of a fish-hook to prevent the escape of the 
 
 prey (Fig. 47). 
 
 A 
 
 
 
 j^-^I-^^^M 
 
 W^^' ' .X..MUH^» 
 
 3 
 
 wmm^Mmmm^ -4 
 
 -4as^ — ' 
 
 
 Fig. 47. — Teeth of the python, bull-frog, horned toad and water snake. 
 
 Of the amphibians some have no teeth, as the toad, while others, 
 such as the frog, have teeth not unlike those of fish, at least always 
 in the upper jaw for the bullfrog has no lower teeth. 
 
 Of the reptiles many have teeth. The lizards eat butterflies, worms, 
 insect larvae, etc., while snakes live on amphibians and their larvae 
 and fish, and the mperine snakes on small mammals. Crocodiles and 
 turtles eat fish, small amphibians and insects. The snakes do not 
 chew their prey but swallow it whole. The lower jaw is jointed in 
 the center and articulates with the skull through the quadrate bone, 
 thus allowing the mouth to open very wide, but the teeth serve only 
 for seizing and holding the prey. In the venomous snakes in the 
 upper jaw are found the "poison fangs" which have a channel leading 
 to the poison sac. The chelonidce or turtles have a horn-like covering 
 for the border of the jaw. 
 
 The birds, of course, have no teeth, the beak being a horny sheath- 
 ing of the ends of the jaw bones. In some the edge is serrated. In 
 no other class is found a greater variation in the food-preparing appa- 
 ratus, or greater adaptation to the food supply. The beak serves 
 largely to obtain the food. In the grain-eating birds the gizzard per- 
 forms mastication. Ducks have soft-edged beaks for sifting the food 
 out of the mud. The skulls of the hawk, heron, English sparrow, 
 crow and toucan shown give an idea of this variation. The crow sub- 
 sists largely on grain, and very often takes grain such as corn out 
 of the husk. It has rather a strong beak suited for this purpose 
 (Fig. 48). 
 
 The skull of the blue heron is also shown. These are aquatic birds 
 and their food comes from the bottom of the water, or in fact, down 
 in the mud w^here they go after little frogs and little fish, and various 
 
EVOLUTION OF TOOTH FORMS 
 
 S3 
 
 other inhabitants of the water. Also is shown jjasser domestwus or 
 English sparnnv, which subsists on very much the same type of food 
 as the crow, only it is a little more omnivorous, and the beak is very 
 much the same. We also have the skull of a South American bird, 
 the toucan, which is a fruit-eating bird. The serrations on the beak. 
 
 E 
 
 
 i 
 
 
 P^T^^> 
 
 1 
 
 ■"^ 
 
 
 1 
 
 ^Hm^-^ _^^^^^^^^^^^^^^^^^^^^H 
 
 Fig. 48. — Beaks of birds, showing functional modifications. 
 
 which are useful in cutting through the skin of fruit and in sifting out 
 the stones, will be noted as a rather interesting adaptation to the 
 needs of this bird. Lastly, we see the skull of the licnck, one of the 
 carnivorous birds. The beak of the hawk is verv strong, and is used 
 
 Fig. 49. — Skulls of three turtles. 
 
 for the purpose of killing the prey; smaller birds and mammals, in 
 the case of large hawks, and insects and food of that sort in case of 
 smaller hawks. 
 
 There is very much the same type of masticating apparatus, if it 
 may be so called, in the turtle. Fig. 49 shows the skull of a large 
 
84 THE TEETH AS A MASTICATING MACHINE 
 
 green turtle, the hawk-bill turtle and the snapping turtle, the beaks of 
 the last two mentioned covered with a very hard, dense membrane, 
 which is very horn-Uke in quahty, and is very much hke the beak 
 of birds, the purpose of it being purely to crush the food, and to 
 cut off a definitely sized amount of food in order that it may be swal- 
 lowed. Of course it is not possible for this animal to chew its food. 
 The first type of tooth that is of very great interest other than 
 merely as a fang, or something of that sort, is the molar of the ungu- 
 lates which are herbivorous and granivorous animals (Fig. 50). Her- 
 bivorous animals live on grain and on vegetable fiber, both of which 
 require considerable trituration in order to be successfully acted upon 
 by the digestive juices, solvents and ferments farther down in the 
 digestive tract. For example, corn and other grains will pass down 
 the alimentary tract of any of these animals, entirely untouched 
 unless the outer membrane is broken, therefore in order to be success- 
 fully digested they have to be well triturated. 
 
 Fig. 50. — Skull of a sheep. 
 
 The series of molar teeth of the horse is a real grinding machine. 
 The surface is raised into elevations alternating with depressions. 
 The elevations are the enamel, the depressions between, the cemen- 
 tum. The cementum is very much softer, and as the tooth wears 
 down the enamel which is harder and more resistant than the cemen- 
 tum wears much less rapidly, so that the surface is continually kept 
 rough for grinding purposes. 
 
 This animal has a great latitude in the side-to-side movement of 
 the jaw; or, to speak more technically, the lateral excursion of the 
 mandible of herbivorous animals is very marked. The jaw does not 
 move much backward and forward; in fact, it hardly moves in these 
 directions at all, but it moves from side to side. The result is that 
 
EVOLUTION OF TOOTH FORMS 
 
 85 
 
 these serrations run IVoni I'rojit to hack. This is exactly tiie reverse 
 of the form of the molars found in the rodents, in which a backward- 
 and-forward movement of the mandible is responsible for the grind- 
 ing, necessitating a different arrangement of the occlusal surface of 
 the teeth. 
 
 John Ryder, many years ago, pointed out the fact that from an 
 examination of the surfaces of the molar teeth of any animal, extinct 
 or living, he could without reference to the skull indicate the way in 
 which the mandible was accustomed to move. 
 
 Fig. 51. — Carnivorous and herbivorous skulls. 
 
 The front of the mouth of the horse is provided with incisor teeth 
 which bite and pinch off the grass and other foods which the animal 
 secures. The canine is quite rudimentary, and usually absent in 
 the mare. 
 
 Cows have incisors only in the lower jaw, and the biting is done 
 between the upper lip and the lower teeth. 
 
 Now passing over one or two important orders as not being espe- 
 cially interesting, next comes a very large family in the animal king- 
 dom, the carnivorous animals, which differ from the class just described 
 in the character of their teeth and also in the manner of the move- 
 ment of the mandible. In studying these dentures three funda- 
 mental elements and their relationship must be constantly borne 
 
S6 THE TEETH AS A MASTICATING MACHINE 
 
 in mind; the food supply, the teeth and the manner in which the 
 mandible is capable of moving. 
 
 For a comparison of dentures the skulls of a large western cat and 
 of an ordinary buck sheep are pictured together (Fig. 51). A vast 
 difference in the grinding teeth, as shown in their respective mandibles, 
 is noted. In one the teeth are narrow, in the other the teeth are wide. 
 Viewed from the side it is seen that the carnivorous molars have 
 sharp edges and are rather more like knives than the grinders of the 
 herbivorous series. In one there are very pronounced canines. 
 
 There is a very marked difference in the temporomandibular articu- 
 lation of these two animals. In the case of the herbivorous animals 
 there are broad, flat glenoid fossae to render possible the large range 
 of lateral excursion of the mandible. On the other hand, the car- 
 nivorous animals have no lateral excursion. The condyles fit into 
 
 Fig. 52.— Skull of a tiger. 
 
 the fossae so tightly as to make almost a hinge joint; and in some 
 instances the distal part of the eminentia articularis so far overhangs 
 its glenoid fossa that it cannot be seen. It is only with great difficulty 
 that the condyles can be gotten out of these fossae; indeed in some 
 instances they cannot be gotten out without breaking the skull. 
 
 In the skull of an Indian tiger, it may be noticed that the molar 
 teeth are of the type described (Fig. 52). They are very sharp and 
 there are tubercles on each side just before the cingulum is reached, 
 and in the closure of the mouth the teeth pass by each other very 
 much like the blades of a pair of shears. Besides the articulation of 
 the mandible which serves to keep it in line, the upper canines fit into 
 the spaces back of the lower canines and, locking the occlusion like 
 guide-pins, prevent lateral movement. 
 
 The carnivora have greater crushing power in their jaws in com- 
 parison to their size than any other animals. This is partly due to 
 
SOLUTION OF TOOTH F0Ri\4S 
 
 S7 
 
 the tremendous temporal muscles which are attached to the Ijroad 
 temporal ridges. 
 
 Fig. 53. — Skull of a black bear. 
 
 In the skull of a black bear is observed almost the same type of 
 dentition as that of the cats, only the canine teeth are a little less 
 powerful, and the carnassial teeth at the rear are not so strongly 
 marked (Fig. 53). 
 
 Fig. 54. — Skull of a coyote. 
 
 A typical carnivorous dentition is found in the canidoB or dog family 
 and in a skull of the canis latrans illustrated are shown the several 
 
88 THE TEETH AS A MASTICATING MACHINE 
 
 types of teeth definitely marked; the incisors, three on each side, the 
 canines, the premolars and the molars (Fig. 54). In the upper jaw 
 there are four premolars and two molars, whereas in the lower jaw 
 there are three molars and four premolars. The fourth upper pre- 
 molar and the first lower molar are known as the carnassial teeth and 
 they are the chief cutting teeth of these animals. 
 
 In the wolf and the American fox the dentition is precisely the 
 same. In some of the smaller carnivorous animals, the badger, the 
 otter and the raccoon, the dentition is very much the same. 
 
 The next family is the rodents, who have a highly developed type 
 of incisor. Thus far attention has been given chiefly to the molar 
 teeth. In the rodents the incisor teeth are of the greater importance. 
 In the skull of the beaver the upper incisor tooth has a chisel-like 
 beveled edge (Fig. 55). It has enamel only upon its labial surface. 
 
 Fig. 55. — Skulls of rodents. 
 
 which is supported by the dentin. There is no enamel on the back 
 of the tooth. As the dentin wears away the enamel is left standing 
 and chips away and thus always preserves a sharp edge. It is really 
 a self-sharpening tool. It has a persistent pulp and grows out as it is 
 worn off. 
 
 The rodents have practically no lateral motion to the mandible, 
 but great backward-and-forward movement. Their molars are 
 ridged, but the ridges run transversely, so that in the backward-and- 
 forward movement of the mandible they can do the same kind of 
 grinding as the herbivorous animals do in the lateral movement 
 (Fig. 56). 
 
 Approaching nearer to man in the scale of animal life, as for example 
 in the apes, dentures are found which are approximately like the 
 human one. Thus in the new world monkeys (Fig. 57) almost exactly 
 the same type of denture is observed as that of man, except that 
 
EVOLUTION OF TOOTH FORMS 
 
 89 
 
 there are three premolars instead of t\v(j. Tliere are two incisors, 
 a canine, three premolars and three molars on each side. 
 
 Fig. 56. — Skulls of rodents, showing transverse ridges in molar teeth. 
 
 Fig. 57. — Skull of a new world monkey. 
 
 The old world monkey is the first animal representing exactly the 
 dental formula of man (Fig. 58). The three molars, the two pre- 
 
00 THE fMfIt A^ A MAStlcATiNG MACHINE 
 
 molars, the canines and the incisors are the same. There is, however, 
 a space between the upper lateral incisor and the canine which is to 
 
 
 ^^^^IBB^^^^j^^^H 
 
 ^^^^^^^^^^^I^^^^B ^m''^ 
 
 .'^^,^^^^1 
 
 Hr 1^..,.^ . 
 
 
 ^|pf '^llMHIii^^^''^ 
 
 __^^^_ 
 
 ■•^ "^"T*'"T^jy( 
 
 ^^^^^1 
 
 
 ^^^H 
 
 ^^k ^^M^^^^B 
 
 ^^H 
 
 Fig. 58. — Skull of an old world monkey. 
 
 Fi.G. 59. — Skull of a chimpanzee, showing deciduous denture- 
 
^nCONbARY FUNCTIONS OF THE TEETH 
 
 01 
 
 admit the lower canine. These animals are largely frugivorous, and 
 their teeth are suitable for this diet. 
 
 The hahoon has very long teeth and exactly the same dentition as 
 has been seen before, that is, it has the same formula. The molar 
 teeth are very much the same in general form as the human niolars. 
 The chimpanzee has a deciduous denture which is even more like that 
 of man (Fig. 59). The gorilla has a very powerful mandible and the 
 canines are very strongly developed. 
 
 Fig. 60. — Architectural construction of skeletal portion of masticating apparatus: 
 the fixed base and movable arm. Columns, arches and buttresses of the fixed base; 
 frontonasal column, A B, zygomatic column, C M D, pterygoid column (only partly 
 visible), supra-orbital arch, B F D; infra-orbital arch, B I D; upper nasal half-arch, 
 B G; palatal arch (not shown) ; lower nasal arch, A H; large molar arch, A C; molar 
 buttresses (descending from M) ; pterygoid arches (not shown) . Columns and arches 
 of the movable arm; mental column, N K; coronoid column. P Q 0; and condyloid 
 column, / L; external oblique column, Q N. (From a photograph of specimen No. 
 4237, Wistar Institute of Anatomy.) (Turner.) 
 
 It is not such a very long step from the dentures of the anthropoid 
 apes to one of the lower types of human denture (Fig. 60). The 
 skull shown is not of the lowest aboriginal type, but the highly devel- 
 oped jaws will be noted while the skull case which contains the brain 
 is not highly developed. 
 
 Secondary Functions of the Teeth. — It might be interesting to dwell 
 for a moment upon certain secondary functions developed in connec- 
 tion with the teeth. Since secondary functions are performed by the 
 teeth of man, those we find in the animals may be briefly viewed. 
 
 They are used as weapons of offence, as in the poison fangs of the 
 snake, which is a very well-known example. The hypodermic needle 
 
92 
 
 THE TEETH AS A MASTICATING MACHINE 
 
 really had its origin in the poison fang of the viperine snakes, a tooth 
 with a tube extending through its center and leading to the poison 
 sac. Upon the contraction of the digastric muscle and opening of 
 the mouth the fang is erected, and when it is driven into the prey 
 the sac at its base is compressed and the poison injected. 
 
 The su'ord fish has a very dangerous projection which it uses to 
 open the abdomen of fish from beneath and thus kill them. The use 
 of teeth as weapons in warfare is well known, as in the rhinoceros and 
 even our domestic animal, the horse. The teeth are also used for 
 purposes of transportation and locomotion. The elephant uses his 
 tusks, which are very highly developed upper incisors, to uproot trees 
 and dig up tuberous roots. He is trained in India to use them for 
 the purpose of transporting lumber, etc. The walrus uses his upper 
 canine teeth to pull himself up on the ice, and also for digging in the 
 mud and uncovering small fish, shell fish, etc., which he consumes. 
 One of the most interesting of the secondary uses of the teeth is found 
 in one of the lemurs. The flying lemur (galeopithecus volans) has 
 curious incisor teeth, the lingual side of which is very much like the 
 teeth of a comb and this the animal uses to comb its fur. 
 
 Fig. 61. 
 
 -Upper and lower teeth in occlusion. (From photograph of specimen in 
 the Wistar Institute of Anatomy.) 
 
 The Human Dental Mechanism. — ^The human dental mechanism pri- 
 marily has to do with the preparation of the food for subsequent 
 stages in its digestion, and it is a very interesting apparatus viewed 
 as a machine, created for this purpose. To better understand it, 
 for purposes of study, it may be resolved into its various elements. 
 In the first place it consists of a fixed base and a movable arm (Fig. 
 61). The fixed base is the upper jaw, and the movable arm is the 
 
THE MANDIBLE 93 
 
 lower jaw. It has been likened to a hammer and anvil turned upside 
 down; but the metaphor of the fixed base and movable arm is a little 
 more expressive. These two elements are equipped with teeth, the 
 armament of the apparatus. Between these two elements extend 
 the muscles which elevate the mandible and constitute the motive 
 power of the machine. Ordinarily they are spoken of as the muscles 
 of mastication; the masseter, the temporal and the two jAerygoids; 
 and then at the front end of the mandible are muscles attached to 
 the genial tubercles to assist in lowering the mandible, the digastric 
 and the geniohyoid, and the muscle which forms the floor of the mouth, 
 the mylohyoid. The cheeks and the lips on the outside ser\'e as the 
 outer walls of the cavity which contains the food while it is being 
 masticated. The tongue on the inside is actively engaged in keeping 
 the food between the crushing surfaces, and assists the cheeks and lips 
 in that way. The last element of the apparatus is the salivary glands, 
 the secretions of which have both a mechanical and physiological 
 function. They lubricate the machine, soften and dissolve the food 
 and agglutinate it for deglutition, besides performing a digestive func- 
 tion in connection with the food. 
 
 The several portions of the apparatus will be taken up and discussed 
 a little more in detail. The fixed base, which is the two maxillse 
 united in the median line, is supported upon the skull by a number of 
 very strong columns or supports. It may be better seen if this base 
 is considered as if it were upside down. There are several of these 
 bony columns, one going inside the orbit and reaching the skull in 
 the median line (A B, Fig. 60). There is another one from above 
 the first or second molar going right up through the malar bones and 
 the outer border of the eye {CM D). When the skull is viewed from 
 below still another column is seen. This is the pterygoid, which 
 supports the distal end of the dental arch. 
 
 The Mandible. — ^The lower jaw is the movable element, the movable 
 arm. It has the general shape of the letter "U" and the ends of 
 the "U" are bent upward at the end and terminate in the condyloid 
 processes. There are several layers of soft tissues intervening at the 
 joint which are placed there to lessen the shock of mastication, and 
 permit the movement of the joint. Between this point and the 
 anterior end the muscles of mastication are attached. They move 
 the mandible as a lever, one end of which is fixed and constitutes the 
 fulcrum. The muscles are attached between this end and what is 
 the weight end of the lever, the forward portion which does the work. 
 Thus it is a lever of the third class. The fulcrum exists in the temporo- 
 mandibular joint which is interesting from a mechanical standpoint 
 because it has so much to do with the way in which the mandible 
 can move. The form of the glenoid fossa is a large factor in this. 
 The jaw cannot move backward but it can move forward and down- 
 ward until it is somewhere near the summit of the eminentia articu- 
 laris. It can also rotate about a horizontal axis, passing approxi- 
 
94 THE TEETH AS A MASTICATING MACHINE 
 
 mately through the condyles. In considering the manner of movement 
 of the mandible it will be seen how the joint renders these movements 
 possible. Its movement is, of course, limited by ligaments. There 
 is the ca'psular ligament which is thickened at the back into a very 
 thick band, which prevents the jaw from going too far forward. The 
 external and internal lateral ligaments are really nothing more or less 
 than still greater thickenings of the capsular ligament itself on the 
 outside and inside of the joint respectively which prevent the motion 
 of the jaw laterally. 
 
 The other ligaments, the stylomandibular and sphenomandihular, 
 which are largely thickenings of the cervical fascia, do not have very 
 much to do with the way with which the mandible can move. 
 
 Of the muscular apparatus it is quite unnecessary to speak exten- 
 sively. The masseter is the muscle most concerned in the elevation of 
 the jaw, and the temporal and internal pterygoid aid in this movement. 
 The function of the external pterygoid must be kept in mind in that 
 it is attached to the interarticidar fihrocartilage as well as to the neck 
 of the condyle, and serves to pull them both forward in the forward 
 movement of the jaw. 
 
 The direction in which the mandible can move may now be noted. 
 First, the simplest form of movement may be taken up, starting from 
 that position of the mandible in which the teeth are in occlusion. 
 This is the point toward which all the movements of mastication 
 ultimately tend. With the teeth in occlusion, what happens when 
 the mandible is depressed? The external pterygoid muscle on each 
 side contracts and pulls its condyle downward and forward. The 
 condyles slide down the walls of the glenoid fossae. The digastric 
 and geniohyoid muscles attached to the genial tubercles contract 
 and pull down the front end of the mandible. The effect of these 
 contractions is to carry the front end of the mandible down and 
 the distal ends forward. The mandible does not rotate about a 
 fixed axis, but the condyles are being carried forward at the same 
 time that rotation is taking place. In other words, there is a com- 
 bination of sliding and of rotation, When the mouth opens the 
 condyles slide forward and downward, and the front end of the mand- 
 ible is depressed. The mouth could not be opened if the condyles 
 remained in the back part of the fossse. 
 
 There is then a combination of rotation about a horizontal axis 
 passing through the condyles and a sliding motion. It so happens 
 that the front teeth describe what is approximately the arc of a circle 
 while they are sliding and rotating; but the center of that circle is 
 not in the condyles, but considerably back of them. 
 
 When the mandible is brought up again to the occlusal position 
 the reverse of this takes place, but Tomes and Dolamore have found 
 out by tracing a large number of jaws that the path of closing is 
 always a little bit in front of that of opening. Direct opening and 
 closing is a type of movement seen in the carnivora. The condyles 
 
A STUDY OF THE HUMAN DENTURE 95 
 
 do not slide forward. In the herbivorous animal there is a lateral 
 movement. In that lateral movement one cf)ndyle remains in the 
 fossa and the other one slides downward, forward and inward. This 
 type of movement is al o noted in the human jaw. One of the con- 
 dyles remains in its fossa, the other one being pulled downward and 
 forward by the contraction of the external jAerygoid muscle of the 
 side. Of course that means that the two pterygoid muscles are 
 capable of independent contraction. The mandible rotates approxi- 
 mately about the center of the stationary condyle. The same occurs 
 when the jaw moves to the other side, as it simply reverses the moving 
 and the stationary condyles. 
 
 If both external pterygoids contract, the jaw is carried forward or 
 protruded. If they contract independent of the muscles attached to 
 the front end of the mandible there is a protrusion of the mandible. 
 That is a type of movement characteristic to the rodents or the gnaw- 
 ing animals. There is then in the human jaw the possibility of these 
 three distinct types of movements. 
 
 Now that the fixed base and the movable arm and the motive power 
 of the apparatus, and the manner in which the mandible, or the 
 movable element may be actuated have been described, the teeth will 
 be discussed from the standpoint of their form and arrangement as 
 suitable to the working of the machine. 
 
 A Study of the Human Denture. — In the first place the forms of 
 human teeth are modified or fused cones, as are all animal teeth (Fig. 
 61). The incisors are cones with a flattened end and may be likened 
 to the form of a chisel. This type of a tooth is especially well devel- 
 oped in the rodents. The canine tooth is more nearly a cone of simple 
 form than any other, although not perfectly circular in cross-section. 
 It is similar in general form to the canine teeth in the carnivora, more 
 like them perhaps in a general way than that of any other animal 
 types, the canine in the herbivora being either lacking or very rudi- 
 mentary in character. 
 
 The bicuspids (the term being derived, of course, from their two- 
 cusped or two-coned character) are, as has been indicated, merely two 
 cones fused together. 
 
 The molars, on the other hand, have a number of cones fused 
 together, each cone represented by a cusp; in case of the lower first 
 molar normally five cusps, and the others only three or four. 
 
 The teeth are arranged in two arched series, consisting normally 
 of thirty-two teeth, sixteen in each series (Figs. 62 and 63). The 
 actual outline of this arch varies with individuals, but within certain 
 bounds this variation in form has no relationship whatever to its 
 functional efficiency. 
 
 The upper arch is larger and overhangs the lower. The upper teeth 
 constitute the fixed base in relation with which the lower teeth move, 
 therefore the upper arch would necessarily cover a larger area in 
 order to permit the movement of the lower over its surface. 
 
96 THE TEETH AS A MASTICATING MACHINE 
 
 On the inside of the teeth is the tongue, on the outside the lips and 
 cheeks. The overhang of the molar and bicuspid series in the rear, 
 and of the incisors in the front of the mouth not only serve the useful 
 purpose of providing a larger area over which the lower jaw may move, 
 but it serves to hold the lips and teeth out of the way and prevents 
 
 
 
 v^aT 
 
 
 
 -jH 
 
 -• ■- -; '^^T^ 
 
 l^H^^H 
 
 ^^Pl> 
 
 
 r « -'M 
 
 ^mt j^M 
 
 ^Li*- 
 
 
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 p^ 
 
 1^^ 
 
 
 
 P^l^,^ 
 
 ^^^*^ 
 
 iL 
 
 ^ 
 
 ^ 
 
 ^^ \^ s , ** :t^^M 
 
 Fig. 62. — Occlusal surfaces of the upper teeth. 
 
 their being caught between the crushing surfaces. On the inside 
 the fact that the lower teeth overlap and pass up the inner sides 
 of the upper teeth serves a similar purpose of keeping the tongue 
 out of the way. 
 
 Fig. 63. — Occlusal surfaces of the lower teeth. 
 
 One may realize how useful this provision is if one observes a set of 
 artificial teeth in which this overhang is not properly provided, when 
 the wearer will frequently complain that he bites his cheeks. Instances 
 of the same difficulty are seen in mouths with full sets of natural teeth, 
 the cusps of which have worn down, and in which the lower jaw has 
 moved forward to what is designated an edge-to-edge bite. There is 
 
OCCLUSION 97 
 
 no doubt of the authenticity of the reported case (^f a well-known man 
 who lost his life through cancer originating in the irritation of the 
 cheek from biting it when the cusps of his teeth had worn (jff until he 
 had an edge-to-edge bite. 
 
 The series of teeth normally present an unbroken surface from 
 one end around to the other; that is, there are no spaces between 
 them, as in some of the animals, particularly the carnivorous animals. 
 Man is the only animal not having diastemata, or spaces between 
 his teeth. This is provided for by the bell-like shape of the crowns 
 of the teeth which do not touch at their necks but at the point of 
 interproximal contact. This contact serves to protect the gum tissue 
 below from injury from the food such as meat and vegetable fibers. 
 If one has experienced what it is in one's own denture to have a flat 
 filling, or none at all, in consequence of w^hich food packs in and 
 produces the long train of uncomfortable results, one will understand 
 how wise is this provision of nature. 
 
 Occlusion. — The occlusion of the teeth, to attempt a very offhand 
 definition, is the relationship of their morsal surfaces when the man- 
 dible is in the position of the resting bite (Fig. 64). The phrase is 
 used to indicate the relationship of the upper and lower teeth w^hen 
 in such contact that there is a definite fitting together of their surfaces. 
 In the occlusal position the condyles of the mandible are in the most 
 distal part of the glenoid fossae. When the teeth are in occlusion the 
 muscles extending between the jaw^s are either in a state of tonic 
 contraction, simply holding the jaw up, or they may be actively con- 
 tracted, that is, pressing the lower teeth firmly upon the upper ones. 
 This is a rather fundamental position of the jaw. It is a position of 
 equilibrium. It is to this position and from this position that all 
 the various movements incident to mastication take place. In the 
 crushing of the food the jaw tends to return from its various excursions 
 to the occlusal position. 
 
 The occlusion of the teeth then means the definite relationship 
 existing between the occlusal or morsal surfaces of the teeth. This 
 must be carefully considered, for in order to understand the machine 
 in motion it must first be studied in repose. Perhaps simplicity will 
 be consulted by dividing the description of the occlusion into that of 
 the incisor teeth, and that of the molar and bicuspid teeth. 
 
 As to the incisors, which are flat and wedge-shaped, the upper 
 overhang the lower, the incisal edges of the lower resting normally 
 in contact with the lingual or inside surfaces of the upper teeth. This 
 normal overhang or overbite is approximately one-third of the length 
 of the lower teeth, although of course it is subject to slight variation. 
 The canine tooth is really intermediate in the character of its occlu- 
 sion between the incisor and the bicuspid series. It partakes of the 
 characteristics of the incisors in that it overhangs the lower teeth, 
 but it is like the bicuspids in having a sharp cusp exactly like the 
 buccal cusps of the bicuspids. 
 7 
 
98 THE TEETH AS A MASTICATING MACHINE 
 
 When the teeth have worn down either from having had a very 
 small overbite and short cusps originally, or from the use of coarse 
 food, so that there is an edge-to-edge bite, the machine is by no means 
 as effective as in the arrangement referred to as normal. In the latter 
 case the food is simply pinched off and not sheared off as when the 
 upper incisors overhang. 
 
 In the study of the occlusion of the molar and bicuspid series of 
 teeth the occlusal surfaces should be first considered (Figs. 62 and 
 63) . It will be noted that they exhibit two rows of cones with depres- 
 sions or fossae intervening between them. On this surface of the 
 bicuspids there is a cone on the inner and outer side. In studying 
 the molars there will be found two cones on the inner and outer sides, 
 except on the third molar where the distolingual cusp may be lacking. 
 
 There are then a row of inner and a row of outer cones, with fossse 
 or little pits intervening between them. There are transverse ridges 
 dividing one fossa from another. The same thing is true of the 
 occlusal surfaces of the lower series of teeth. They have a definite 
 arrangement, a row of outer and a row of inner cusps with fossae 
 between. However, there is a difference in the shape in these two 
 rows of cusps. The inner ones are rounded in the upper series of 
 teeth and are considerably larger than those in the outer row. Speak- 
 ing technically, the lingual are larger than the buccal cusps, which 
 are sharp and thin, while the reverse of this is true of the lower teeth. 
 The buccal cusps, or outer cones, are the large round ones; the inner 
 cusps are sharp and thin. The rounded cusps in both series are really 
 the functionating cusps. They are the ones which are received into 
 the fossae when the teeth are in the occlusal position. If an upper 
 set of teeth is superposed upon a lower, it will be found that the lower 
 buccal cusps occupy the fossae of the upper series and the rounded 
 lingual cusps of the upper fit into the fossae in the lower set of teeth. 
 
 It is not enough in the normal arrangement that any cusp should 
 fit into any fossa. In normal occlusion there is a definite fossa for 
 each cusp to occupy (Fig. 64) . Orthodontists have accepted a simple 
 method of determining when a denture is in normal occlusion. They 
 look to see if the mesiobuccal cusp of the first upper molar occupies 
 the buccal groove of the first lower molar and if so and the other 
 cusps fit into their fossae, and so on, then the occlusion is correct. If 
 this cusp is in front of or back of the buccal groove then it would 
 not be normal occlusion; there might be an interdigitation of the 
 cusps, but it would not be perfectly normal unless each cusp occupied 
 its own particular fossa. 
 
 In an inner view of the denture (Fig. 65), the overlapping of the 
 sharp and thin inner cusps of the lower teeth will be noted, each 
 fitting into a groove or space on the liiigual surfaces of the upper 
 teeth. This interdigitation has also another rather interesting advan- 
 tage, and this is that each tooth of both series, with two exceptions, 
 js opposed b^ two teeth in the opposite iaw. They do not meet en4 
 
OCCLUSION 
 
 99 
 
 Fig. 64. — Occlusion of the molar and bicuspid teeth, external view. (From photograph 
 of a specimen in possession of Dr. F. A. Peeso.) 
 
 Fig. 65. — Occlusion of the molar and bicuspid teeth, internal view. (From photograph 
 pf a specimen in possession of Dr. F. A. P^eso.^ 
 
100 
 
 THE TEETH AS A MASTICATING MACHINE 
 
 on end, but each tooth is in relation to two teeth. The exceptions 
 are the upper third molar and the lower central incisor which have 
 but one opponent each (Fig. 66). 
 
 Fig. 66. — Occlusion of the molar and bicuspid teeth, occlusal view. Lines are drawn 
 from the lingual cusps of the upper teeth and buccal cusps of the lower to the correspond- 
 ing depressions into which they fit. (From photograph of a specimen in possession of 
 Dr. F. A. Peeso.) 
 
 Now that the relationship of the morsal or occlusal surfaces of the 
 teeth in the position of occlusion has been described, it will often be 
 referred to as the occlusion of the teeth. 
 
 Fig. 67. — The " Curve of Spee." Line passing through anterior face of condyle, 
 a photograph of a specimen in the Wistar Institute of Anatomy.) 
 
 (From 
 
 There are certain other characteristics of the arrangement of the 
 occlusal surfaces of the teeth which are related to what shall be spoken 
 
OCCLUSION ^ 101 
 
 of as the articulating or active relations of the denture that will be 
 useful when the denture is in motion. One of these characteristics, 
 which is a very iniportant part in the so-called articulation of the 
 teeth, is as follows: If an imaginary line were drawn touching the 
 buccal cusps of the lower series of teeth in a perfect denture, it would 
 be found that they described approximately the arc of a circle, and 
 if it is continued backward under a perfectly typical arrangement, it 
 passes just anterior to the articulating face of the condyle (Fig. 67). 
 Sometimes this line may go a little in front of it, more frequently it 
 is back of the condyle; in a perfect arrangement it passes through 
 the anterior face of the condyle. The same thing is necessarily true 
 of the upper teeth. This is called the curve of Spee. It has been 
 named after von Spee who first called attention to it. This curved 
 arrangement of the occlusal surfaces of the molar and bicuspid teeth 
 has an important bearing on the movement of the mandible. 
 
 If two surfaces are to slide one upon the other without interrupting 
 their contact at any point, that is, without being separated at any 
 point, these must be either two perfectly flat surfaces like two panes 
 of plate glass, where one can slide upon the other without admitting 
 air underneath, or else two curved surfaces which are the arcs of the 
 same circle. If they were any other shape, as for example, a parabola 
 or hyperbola, or any irregular curve, they would separate at some 
 point. Now if it were desirable that in the forward-and-backward 
 movement of the mandible all of the lower teeth should slide upon all 
 of the upper at the same time, then these teeth would have to be 
 either in a perfectly plane surface, all absolutely level, or they would 
 have to be arranged around the arc of a circle. 
 
 In order to get a clearer understanding of this, it may be supposed 
 that there are no cusps upon the occlusal surfaces and that a curved 
 line represents the top surface of the lower teeth, and a similar curved 
 line represents the occlusal surfaces of the upper teeth. Now if these 
 surfaces are to slide upon each other, without breaking their contact, 
 in the case of the human jaw the mandibular condyles, which of 
 course slide upon the glenoid fossse, would have to slide in exactly 
 that same curve, otherwise the teeth would be separated at some 
 point. 
 
 Now this is the significance of this arrangement of the teeth, that 
 the so-called curve of Spee is always either continuous with the path 
 of the condyle, or it is concentric with it; at any rate they can both 
 move around the same center. This, it must be remembered, is 
 merely a very much simplified example taken to explain the principle 
 involved. These are not plane surfaces, but are cuspid surfaces, 
 and each one of these cusps fits into a fossa. However, it does not 
 take a very great stretch of imagination to see that, though they 
 have cuspid surfaces, the cusps may be arranged so that instead of 
 sliding upon a smooth surface they slide upon the walls of the fossae 
 into which they fit. That it is possible to have such an arrangement 
 
10^ 
 
 THE TEETH AS A MASTICATING MACHINE 
 
 may be conceived and this is the arrangement in the perfectly typical 
 and typal human denture. Of course the mandible has to be depressed 
 the least bit in order to enable each cusp to slide downward on the 
 front wall of the fossa into which it fits. The cusps slide forward on 
 the walls of the fossse and back again; and the advantage of this is 
 that every one of the cusps is functionating, is in contact at the same 
 time, not just hitting here or there. But it is possible for a denture 
 to functionate in this fashion only if the teeth are arranged in the 
 manner described. 
 
 It will presently be seen, however, that the lower teeth of a normal 
 typical denture cannot slide very far forward without the teeth sepa- 
 rating, because the lower incisors strike the lingual surfaces of the 
 
 Fig. 68. — Upper and lower bicuspid and molar teeth (side view), showing relative 
 height of buccal and lingual cusps of upper teeth. (From photograph of a specimen in 
 the Wistar Institute of Anatomy.) 
 
 upper incisors. After the cusps have moved perhaps half-way up the 
 walls of the fossse into which they fit, the lower front teeth strike the 
 upper incisors upon which they slide and the distal teeth are separated. 
 But in the return movement, when the lower teeth strike the lingual 
 surface of the upper and slide up until the distal teeth are in contact 
 and then slide back into the occlusal position, each one of the cusps 
 then slides back down the wall of its fossa into the position of the 
 occlusion. 
 
 There is another characteristic of the arrangement of the molar 
 and bicuspid teeth which is related to the lateral excursion of the 
 jaw. Taking a typically perfect set of teeth with the jaws slightly 
 apart, it will be seen that, starting from the first upper bicuspid and 
 going toward the rear, the buccal or outer cusps become relatively 
 
OCCLUSIOM ' lOr^ 
 
 a little bit shorter than the hngual cusps and, in the case of the lower 
 teeth, they become a little longer than the lingual cusps. Of the 
 second bicuspid in the upper jaw, the buccal and lingual cusps nor- 
 mally occupy the same horizontal plane. Just in front of it the first 
 bicuspid has a buccal cusp that is longer than the lingual. Return- 
 ing to the first molar, the buccal cusps are a little shorter than the 
 Hngual, and going back farther and farther, they get relatively shorter 
 than the lingual. In other words, the plane of the cusps, instead of 
 being level, gradually curves rootword and outward toward the rear 
 of the denture (Fig. 68). 
 
 1 
 
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 Fig. 69. — Lower bicuspid and molar teeth, front view, showing relative height of 
 buccal and lingual cusps. Same mandible as Fig. 68. (From photograph of a speci- 
 men in the Wistar Institute of Anatomy.) 
 
 This arrangement can be demonstrated in the mandible although 
 the first bicuspid has a rudimentary cusp or none at all and is atypical 
 in this particular; but farther back the buccal cusps are relatively 
 higher than the lingual until at the third molar they are considerably 
 higher (Fig. 69). 
 
 In looking at the upper teeth this characteristic may not be so well 
 illustrated as in the lower jaw, but a gradual tilting out of the long 
 axes of the teeth will be noted. This arrangement is due not only 
 to the height of the cusps, but to a change in the inclination of the 
 teeth. The second bicuspid occupies a perpendicular position; but 
 the teeth back of it gradually tilt outward. 
 
104 THE TEETH AS A MASTICATING MACHINE 
 
 Now what is the relationship of this arrangement to the lateral 
 excursion of the lower jaw? When the mandible is moved to one side 
 with the teeth in contact, if the teeth were arranged so that their 
 cusps occupied the same horizontal plane those on one side would be 
 separated while those on the other side would be in contact. The 
 reason for this is that when the mandible is carried to one side one 
 condyle remains stationary in its fossa while the other is pulled for- 
 ward and also downward as the surface of the glenoid fossa inclines 
 downward and this side of the jaw must be carried a little lower than 
 the side with the stationary condyle. 
 
 If it were not for this difference in the level of the buccal and lingual 
 cusps there would be a lack of contact on the side from which the 
 movement was taking place. In order to compensate for this lower- 
 ing of the mandible on the side from which the movement has taken 
 place, the two longest or most prominent cusps come into contact; 
 whereas on the other side, the side toward which the movement has 
 taken place, there is a short and long cusp in contact; and it is just 
 the difference between these two which compensate for the down- 
 ward movement of the jaw on the side from which the movement has 
 occurred (Fig. 70). 
 
 Fig. 70. — Diagram illustrating contact of cusps in lateral excursion of the mandible. 
 Section through jaws at position of second molar. O P, line touching lingual cusps of 
 upper molars ; L R, line touching buccal cusps of upper molars ; *S T, line touching buccal 
 cusps of lower molars, showing the downward movement of the mandible on the right 
 side necessary for contact of the cusps. 
 
 What is the advantage of this arrangement? It has exactly the 
 same functional advantage in the lateral excursion of the mandible 
 as the curve of Spee affords in the forward and backward excursion 
 of the jaw; that is to say, it enables both sides to be in contact at 
 the same time. This principle is taken advantage of in making 
 artificial dentures. If both sides of the plates were not in contact 
 at the same time, so that the patient was biting foods on one side 
 with the other side not touching at all, the plates would be thrown 
 down from their base. So it is desirable to imitate the human denture 
 in this particular because it prevents overstrain and provides a denture 
 that is more efficient mechanically. 
 
 There is one other detail of the occlusal surfaces of these teeth 
 relating to their function which must be mentioned and this is, that 
 
MASTICATION OF FOOD 105 
 
 clearance spaces are provided for the escape of fo(jd which lias been 
 masticated. The upper row of buccal cusps overhangs the lower, 
 and on the outer walls of all of these fossa% into which the lower 
 buccal cusps fit, are grooves leading downward and outward through 
 which the food is squeezed. Anyone operating a cutting or grinding 
 machine of any kind will realize the necessity of getting rid of the 
 waste or the chip, as the mechanical terminology is. That is, after 
 the substance has been crushed or ground, there must be an avenue 
 of escape for the waste, and so these grooves, which are not visible 
 on the side view, but which lead downward on the outside of the arch, 
 and upward on the inside, are provided. When the food is crushed 
 between these surfaces it is carried up above the tongue on the inside 
 and downward into the pocket of the cheek on the outside where it 
 may be pressed between the teeth when they are separated for the 
 next crushing motion. 
 
 Mastication of Food. — Having described the machine, its mode of 
 operation may now be considered. In the case of man the prepara- 
 tion of food in the mouth does not begin with prehension or gripping 
 of the food, as it does in most of the lower animals. Man has, of 
 course, developed very much beyond that point, and there is no neces- 
 sity for it. There is no provision for this in his denture therefore, 
 and he has no sharp teeth to prehend the food. The first act of the 
 human animal is to incise; but even incision or the cutting off of 
 appropriately sized particles of food is largely rudimentary in man, 
 since with the development of conventional methods of eating, bringing 
 into use the knife and fork, the incisor teeth are not much exercised. 
 The biting of certain articles of food only is permitted by the usages 
 of polite society. But when incision is indulged in it is rather an 
 interesting mechanical act. The lower jaw is depressed and carried 
 forward, the food is pressed between the lips and upon the incisal 
 edges of the upper teeth, when the lower jaw is carried upward. If 
 the food is very hard, the ends of the upper and lower teeth are almost 
 exactly opposite each other. This direct opposition is absolutely 
 necessary from a mechanical standpoint, in order to bite through 
 hard, resistant food. As soon, however, as the teeth come into 
 contact, or nearly into contact, the mandible is carried backward as 
 well as upward, and the lower incisors slide up the inner surface of 
 the upper, just like the blades of a pair of shears. Then the food is 
 carried back by the tongue to the distal part of the mouth. 
 
 In order to understand clearly just what is demanded during trit- 
 uration of the food, it will he wise to refer again to the importance 
 of a knowledge of the character of the food itself. Its chemical 
 nature is not of so much interest as its physical character viewed 
 purely from a mechanical standpoint. Man's food, broadly speak- 
 ing, consists of meat fiber, vegetable fiber, grain or cereals and foods 
 made from them and legumes, although the last is not of the same 
 importance as the others. The chief articles which must be pre- 
 
106 TUB TEETH AS A MASTICATING MACHINE 
 
 pared for digestion are vegetable and meat fibers, cereals or grain. 
 It is necessary to reduce this food to a condition suitable for passage 
 into the stomach. Its physical consistence must be reduced that it 
 can be acted upon by the digestive ferments and solvents. The 
 crushing of grain, the starchy element of man's food must be very 
 much more extensive than is necessary for the other elements. In 
 the first place, its outer covering has to be removed, or at least broken, 
 and the grains of starch themselves must be so ground up that they 
 can be acted upon by the enzyme of the mouth, and by those farther 
 down in the digestive tract. Mastication of cereals and foods made 
 from them is therefore really much more important than the mastica- 
 tion of other foods. 
 
 Baron Oefele has conducted some investigations to show the very 
 poor ability to digest cereals exhibited by people who do not have a 
 full complement of molar and bicuspid teeth. His results are very 
 interesting, but it is only necessary for our purpose to state the fact 
 that he has very conclusively shown the defective digestion of cereals 
 by those whose molar and bicuspid teeth are defective. 
 
 Vegetable fibers must be cut up into short lengths and crushed so 
 that they can be readily acted upon by the solvents and digestive 
 ferments. This is more important than the comminution of meat 
 fibers. Many carnivorous animals eat animal flesh in great masses; 
 carnivorous snakes always swallow their prey whole. Nevertheless 
 it is important that meats should be masticated by man in order 
 to break up the consistence of the fiber, and also it should be cut up 
 into small masses to facilitate its passage through the digestive tract 
 and that it may be readily acted upon by the enzymes and ferments 
 
 Dr. Black, who has investigated quite extensively the problem of 
 the mastication of the various kinds of foods, is authority for the 
 statement that the up-and-down movements of the jaw, very much 
 like those of the carnivorous animals, are chiefly concerned in the 
 mastication of meats, and that the lateral movements are chiefly 
 concerned in the mastication of cereals and foods made from them. 
 
 While it is not true that in the masticating of any type of food 
 one is limited to any particular type of movement, it is a fact that 
 the foods which require the greatest amount of crushing force are 
 masticated in the return from the lateral excursion of the mandible. 
 
 When the cereal food is brought into the mouth and carried back 
 to the molar and bicuspid teeth, mastication usually occurs on one 
 side at a time; and if the mouth is in a state of balance and perfect 
 health, it is very apt to occur first on one side and then on the other. 
 The mandible is carried to one side, the cusps are brought into con- 
 tact, some of the food being cut off on the outside and some on the 
 inside, but a mass remains which occupies the space between the 
 cusps and in the fossse and on the return to the position of occlusion 
 the cusps slide into the fossse with a sort of mortar-and-pestle effect. 
 In this movement the greatest crushing ability is exhibited. In 
 
MASTICATION OF FOOD 107 
 
 ordinary mastication this lateral movement is combined with direct 
 up-and-down movement. Mastication is not carried on in any precise 
 mechanical order, but all of the movements are combined at times. 
 
 Dr. Black has also made in this connection what is rather an inter- 
 esting table of the amount of force necessary to crush the various 
 foodstuffs. Dr. Joseph Head, of Philadelphia, has also produced 
 a similar table, though using a different method, and the two will 
 be presented together. Dr. Black's experiments were most interest- 
 ing. He had some brass castings made of the molar and bicuspid 
 series of teeth, upper and lower, and had them arranged in a machine 
 so that the lower could be brought up into contact with the upper 
 by the movement of a hand lever: This simply had the up-and-down 
 motion. He and a party of friends went at various times to restau- 
 rants in Chicago, and while they were dining themselves, they gave 
 this automatic chewing machine various tidbits, and registered on it, 
 as they could not on their own jaws, the amount of force necessary 
 to crush the various foodstuff's. 
 
 Dr. Head, realizing the value of the lateral excursion, and believing 
 that much less force was required in the crushing of food with this 
 type of movement, made experiments similar to those of Dr. Black, 
 except that he took a human skull with a fine set of teeth and turned 
 it upside down, bored a hole through the skull, and suspended weights 
 from the mandible by means of string or wire. He proved that to 
 accomplish the same amount of crusHing, less force was required in 
 this lateral sliding movement. Dr. Black's and Dr. Head's tables 
 are here given. 
 
 Dr. Head's Dr. Black's 
 
 results. results. 
 
 Raw cabbage 16 40-60 
 
 Raw onion 4 
 
 Head lettuce 8 25-30 
 
 Radish— whole 20-25 
 
 Radish— pieces 10-25 3&-40 
 
 Corned beef 18-20 30-35 
 
 Boiled beef 3 
 
 Tongue ' 1-2 3-5 
 
 Lamb chops 16-20 
 
 Roast lamb . 4 
 
 Roast lamb kidney 3 
 
 Tenderloin of beefsteak (very tender) .... 8-9 35-40 
 
 Sirloin steak . . . . : 10-20-43 
 
 Round of beefsteak (tough) 38-42 60-80 
 
 Roast beef 20-35 35-50 
 
 Boiled ham 10-14 40-60 
 
 Pork chops 10-13 
 
 Roast veal 16 35-40 
 
 Veal chops 12 
 
 Roast mutton ., 18-22 
 
 Very tough meats 90 
 
 Hard crusts 100 
 
 Hard candy 250 
 
 Dr. Black also experimented with a gnathodynamometer by means 
 of which he could measure the strength exerted by the human dental 
 
108 THE TEETH AS A MASTICATING MACHINE 
 
 mechanism, which for the average was from 150 to 175 pounds. He 
 reported one case in which 275 pounds were recorded on the instru- 
 ment. He also tried it with persons wearing full artificial dentures, 
 upper and lower, the result being that the average was from 35 to 40 
 pounds. One may see a vast difference in the amount of crushing 
 ability of natural and artificial teeth. 
 
 Mastication is, of course, a voluntary act (speaking physiologically), 
 that is, it begins voluntarily and is continued reflexly and automatic- 
 ally. The food is rolled from one side to the other by the tongue. 
 The teeth functionate first on one side and then on the other. The 
 teeth have exquisite sensibility. It is through them that sensations 
 are received that indicate the amount of chewing necessary to give 
 any given mouthful, and also through them in conjunction with the 
 tongue as to whether the food has been thoroughly triturated or not. 
 After it has been thoroughly masticated it is rolled up into a bolus on 
 the tongue, the tip of which is elevated, and by contraction of the 
 muscle of the floor of the mouth, the mylohyoid, the food is forced 
 back into the esophagus. 
 
 The secretion of the saliva, while constantly going on in the mouth, 
 is tremendously increased when any foreign substance, like food, is 
 put into the mouth. The working of the muscles moving the jaw 
 probably also increases the flow of saliva. The saliva serves to lubri- 
 cate the various portions of the apparatus which are in the mouth. 
 It contains a ferment^ ptyalin, which has some digestive usefulness. 
 The water in the saliva dissolves some of the food, and as it also 
 contains mucin, the latter helps to agglomerate the mass and to 
 lubricate it so that it is finally easily swallowed. 
 
 The teeth are equipped with means of resisting the wear incident 
 to the activity of this mechanism. The enamel is the outer envelope 
 of the crowns of the teeth and is the hardest structure in the human 
 body. It is of course necessary to have a very hard covering for the 
 teeth to enable them to resist the wear incident to their long use. 
 Under present conditions of civilization, where comparatively little 
 mastication is necessary, not a great deal of wear of the teeth occurs. 
 The teeth of prehistoric man, and, indeed, of our own aboriginal races, 
 wore very badly from the coarse character of the food. Any collec- 
 tion of skulls of North American Indians which one may happen to 
 see at once impresses one with the great amount of wear of these 
 teeth. Of course this is due, not only to the rough character of the 
 food, but also to the fact that Indian corn, a staple diet, being ground 
 in stone mortars had fine particles of stone or silica mixed with it, 
 which serve to grind the teeth down. 
 
 Anatomists have recognized several degrees of wear. No one 
 reaches the age of twenty-five without beginning to show some evi- 
 dence of wear of the teeth. A little later the second degree is reached, 
 where the enamel is worn through and the dentin exposed, and the 
 cusps are really beginning to wear down a little; or it may even, under 
 
SUPPLEMENTARY FUNCTIONS OF THE TEETH 
 
 109 
 
 conditions of our civilization, get to the third degree, where the cusps 
 are all worn away and the teeth are reduced in height. 
 
 Mastication has also a beneficial influence upon the teeth. The 
 friction of the food exerts a cleansing influence as regards colonies 
 of bacteria and deleterious food particles upon their surface. Disuse 
 of the teeth on the other hand, greatly increases the deposits of sali- 
 vary calculus and sordes upon the teeth. Often upon looking into 
 a mouth it is perfectly easy to judge upon which side a crippled tooth 
 exists, because when the chewing is done on the other side, exclu- 
 sively, deposits on the teeth of the crippled side identify it. 
 
 The use of the denture in mastication also exercises the peridental 
 membrane. As the teeth move up and down in their sockets, blood 
 
 T&D7b 
 
 K&a 
 
 Fig. 71. — 1, diagrammatic drawing, showing place of articulation of the consonant 
 sounds; 2, drawing showing contact of the tongue with molars and bicuspids in the 
 formation of certain consonants. 
 
 is pumped in and out of this tissue and thus it is kept in a healthy 
 condition and degeneration of the pericementum is deferred if not 
 prevented. 
 
 Supplementary Functions of the Teeth. — In conclusion, certain second- 
 ary functions of the teeth will be briefly considered. They participate 
 in the activity of the mechanism concerned in the production of 
 speech. The lips and tongue with the teeth and the contiguous 
 portions of the alveolar process are the most important factors in 
 the production of consonant sounds. Thus the "F" and "V" sounds, 
 for example, are pronounced by the sudden escape of air between 
 the lower lip and the upper front teeth. It is unnecessary to go into 
 this detail at length, but an allusion is made to it as an additional 
 reason for care in the preservation of the teeth (Fig. 71). 
 
no 
 
 THE TEETH AS A MASTICATIXG MACHIXE 
 
 §'&>' 
 
 J 
 
 Fig. ~1. — The facial muscles of expression. 
 
 Pjq 73 — Photograph, showing effect 
 of the loss of the teeth upon the mouth, 
 and wrinkles established thereby. 
 
 Fig. 74. — Photograph, showing the 
 effects of the loss of the teeth upon thg 
 profile. 
 
SUPPLEMENTARY FUNCTIONS OF THE TEETH 111 
 
 They are also passive elements in the mechanism concerned with the 
 facial movements of expression, which are movements of the facial 
 muscles that either supplement language or convey ideas or emotions 
 or states of mind. 
 
 The underlying structures in this mechanism are the skull and the 
 teeth, overlying which are soft tissues including the facial muscles of 
 expression. There is a large group of these centering around the 
 mouth which makes it one of the most expressive features of the 
 face. These muscles are superficial, converge toward the mouth and 
 terminate in one big muscle, the orbicularis oris, of which latter the 
 lips are chiefly composed. These are all supported beneath by the 
 teeth and the alveolar process, over which as a sort of base they are 
 moved by these various muscles. In some of these movements the 
 lips are parted so that the teeth are disclosed. Both pleasurable and 
 painful emotions may be so expressed (Fig. 72).* 
 
 Finally the teeth serve to support the lips and the cheeks and thus 
 take part in the maintenance of the fixed expression of the face. 
 Their loss is attended by a falling in of these tissues, an approxima- 
 tion of the jaws, and by a marked change in the appearance in the 
 face. To guard against this "last scene of all" is the final reason 
 for their preservation (Figs. 73 and 74). 
 
CHAPTER IV. 
 MALOCCLUSION OF THE TEETH. 
 
 By RODRIGUES OTTOLENGUI, M.D.S., D.D.S., LL.D. 
 
 If the mouth hygienist, besides preservmg the health of her charge, 
 would aim likewise to guard against the attacks of disease, it is evi- 
 dent that she should have knowledge of such diseases as may prove 
 a menace in her particularly field of work, and she should likewise 
 learn to recognize these diseases in their incipient stages that she 
 may refer the patient for treatment before the ravages prove serious. 
 
 Therefore, in presenting the subject of malocclusion, let us con- 
 sider for a moment how dental caries is aggravated by irregular or 
 malposed teeth, 
 
 DENTAL CARIES. 
 
 Areas of Susceptibility. — Students of the subject tell us that in the 
 vast majority of cases caries begins in certain definite localities. 
 Thus caries upon the masticating surfaces of bicuspids and molars 
 first appears in the sulci or fissures between the enamel plates. 
 Between the teeth or, as we say, on the approximal surfaces, caries 
 has its initiation at, or just gingival to, the approximal contact 
 points. While it may not be absolutely true that "a clean tooth 
 never decays," it is true than an unclean tooth is more vulnerable 
 than one that is clean. It follows, therefore, that the unclean or 
 uncleansable parts of a tooth are more likely to decay than the clean 
 or readily cleansable parts of a tooth, and this is in consonance with 
 the statements above made as to the locations where caries usually 
 begins, because the sulci of molars and bicuspids, and the approximal 
 contact points of all teeth, are the localities in which food debris is 
 most apt to lodge and most difficult to dislodge. Another region in 
 which caries often occurs is upon the labial and buccal surfaces of 
 teeth immediately near the gum line. Here the seepage of mucus 
 agglutinizes the food debris and the overhanging gum margins pro- 
 tect the accumulations from the natural cleansing agents. Still 
 another place is in the grooves on the buccal surfaces of the molars, 
 which are analogous with the sulci upon the masticating surfaces. 
 These, then, are to be counted the vulnerable places. 
 
 Areas of Immunity. — The lingual surfaces of all the teeth, swept as 
 they are by the tongue, constitute the most immune areas, though 
 occasionally we find pits or crevices in the upper incisors, which 
 because they are pits or crevices become susceptible points. The 
 
DENTAL CARIES 113 
 
 labial surfaces of all incisors and cuspids, except at or along the gum 
 margins, and the buccal surfaces of all bicuspids and molars, exept in 
 the molar buccal grooves and along the gum margins, are practically 
 immune to caries. 
 
 So we find that there are certain localities which are vulnerable 
 and other definite parts of the tooth which are practically immune 
 to caries. Also, that this immunity is closely related to the possi- 
 bility of cleansing these areas. 
 
 Between these vulnerable and immune locations are areas of com- 
 parative immunity, this comparative immunity increasing toward the 
 immune or most easily cleansed part, and decreasing as we approach 
 the vulnerable or less easily cleansed part. 
 
 Caries and Malocclusion. — ^Thus we arrive at the important relation 
 between malocclusion and caries. We have seen that certain parts 
 of the teeth are counted to be immune to caries, and that adjacent 
 to these areas are other parts which are comparatively immune. But 
 this is true only when all the teeth are in normal relationship one 
 with the other, which in effect means when all the teeth are in 
 normal occlusion. 
 
 Malocclusion may not perhaps often increase the vulnerability of 
 the occlusal surfaces of the teeth, though at times it may even have 
 this effect; but malposition of the teeth will frequently increase the 
 vulnerable approximal areas by increasing the contactual areas beyond 
 the normal; and it will likewise lessen the immunity of the immune 
 and comparatively immune areas, by rendering cleansing more difficult 
 and at times even impossible. 
 
 We will better comprehend this by the examination of a skull where 
 we may see the teeth and bones freed from the soft tissues. 
 
 Interproximal Spaces. — ^Fig. 75 affords a good example of normally 
 occluded teeth, one maxilla and one-half of the mandible with their 
 teeth being shown. Attention should be called first to the spaces 
 between the teeth known as interproximal spaces. Note that these 
 are, generally speaking, trangular in shape, the base of the triangle 
 being along the border of the alveolar bone, the sides of the triangle 
 being the approximal surfaces of the adjacent teeth, and the apex 
 at the point of contact of the two teeth. Select any approximal 
 space distal of the cuspids and note that the apex of the cusp of the 
 antagonizing tooth of the opposing jaw falls immediately opposite 
 the center of this interproximal space, the obvious tendency being to 
 force food between the teeth, and into this interproximal space. 
 Hence the need of the contact point. Passing from the study of these 
 bones and examining a living specimen, we would observe that this 
 interproximal space is filled with gum tissue, this particular part of 
 the gum being denominated the septum. This septum, filling as it 
 does a triangular space, is conical in shape and is thicker than other 
 parts of the gum. For this reason its outer surface is farther away 
 from its bony support and consequently it is more easily injured than 
 
114 
 
 MALOCCLUSION OF THE TEETH 
 
 the gum elsewhere. This is an added need for close contact of the 
 adjacent teeth, as a protection to this sensitive tissue from the impac- 
 tion of food and the retention of it, if forced into the interproximal 
 space. The student should note also that the gum septum, also 
 called the gingiva, even in the healthiest subject, does not entirely 
 fill the interproximal space, so that commonly there is a small but 
 actual space between the approximal contact points and the septum 
 or gingiva. It is because of this fact that approximal caries often 
 has its inception just gingivally of the contact point, since it is just 
 in this space which is protected from the natural cleansing agencies 
 that debris may collect and remain. 
 
 Fig. 75. — Occlusion of the molar and bicuspid teeth, external view. (From photograph 
 of a specimen in possession of Dr. F. A. Peeso.) 
 
 If we study the matter more closely still, we must see that wise 
 provision has been made for the exclusion of foodstuffs from the 
 interproximal spaces. True, the grinding cusps of the masticating 
 teeth, falling as they dp exactly opposite to the entrances to the 
 interproximal spaces, would seem to be advantageously situated for 
 the forcing of food into these spaces, yet this accident is well guarded 
 against. First we find that the cusps in typically formed teeth occlude 
 with the mesial and distal marginal ridges of the two teeth with 
 which each cusp normally antagonizes. These marginal ridges have 
 
DENTAL CARIES 115 
 
 planes sloping toward the central portions of the masticating surfaces, 
 and hence away from the interproximal space. 
 
 Moreover we find sulci serving as sluiceways to lead the food, 
 during maceration, lingually and buccally away from the spaces 
 between the teeth, and consequently it should require more force to 
 crowd the food into the interproximal spaces than away from them 
 into and out of the sluiceways. Additional protection of the gingivae 
 is to be found in the form and position of the contacts, as well as in 
 the form of the septum itself. The contacts are closest occlusally 
 and triangular in shape so that the width of the contacts increase 
 slightly toward the gingiva, while the approximal surfaces of the 
 teeth, curving rapidly apart, afford ample opportunity for the escape 
 of food, especially as the septum itself is conical and full enough 
 bucco-lingually to extend somewhat beyond the actual interproximal 
 space and thus aid in receiving and carrying the food away from, 
 rather than into, the space. 
 
 All this may seem somewhat complex, whereas in reality when once 
 fully comprehended, it will be seen to be quite simple and as admirable 
 an arrangement as it is a simple one. Yet its efficiency depends entirely 
 upon and is proportional with its typical normality. Any aberration 
 from the typical in the formation of the teeth, and any departure from 
 the normal in the position of the teeth, must proportionately destroy 
 the balance between the several factors which, when present and 
 working in unison, will afford ample protection to even this vulnerable 
 locality. 
 
 Contact Point in Normal Arrangement. — Glancing again at Fig. 75, 
 the student is asked to note that the teeth being in normal arrange- 
 ment, the contacts are at a minimum, while yet being sufficient to 
 afford protection. Since caries starts at these points of contact, it 
 must be manifest that any malposition of the teeth which will bring 
 into contact a greater area than normally should be in contact, not 
 only increases the actual area of the vulnerable region, but by altering 
 the protective form of the contact points, must necessarily add also 
 to the vulnerability. In Fig. 75 note also that as each tooth is in its 
 normal pose the greater portion of its exposed surface is brought into 
 symmetrical alignment with its neighbors, so that any cleansing agency 
 sweeping around the arch would come into touch with and conse- 
 quently would cleanse the greatest width of such surface. Thus, 
 where teeth are normally placed, a brush passing around the arch 
 would cleanse nearly all the labial an4 buccal enamel, while a brush 
 passed vertically over these surfaces would cleanse them entirely. An 
 examination of the lingual surfaces (Fig. 76) discloses the fact that 
 the truly normal arrangement again brings beneath the influence of 
 a cleansing agent the widest expanse of surface. 
 
 It is equally evident that any malposition of even a single tooth 
 must interfere with this cleansing effort. If a tooth be turned upon 
 its axis, then a smaller part of its labial or buccal surface can be 
 
116 
 
 MALOCCLUSION OF THE TEETH 
 
 swept by the brush when the brush is used upon that part, and the 
 same would be true when brushing the Ungual surfaces. If a tooth 
 extends beyond its neighbors, either buccally or lingually, not only 
 will it become more difficult to cleanse that particular tooth, but its 
 position must interfere more or less with the cleansing of its neighbors. 
 It is seen then that any aberration from the normal in the inter- 
 relation of the teeth renders them more difficult to keep clean, but it 
 must be understood that aside from the artificial cleansing which is 
 to be accomplished with brushes, powders, etc., the typical forms and 
 arrangement of the teeth are such that the normal use of these organs 
 leaves them moderately clean, so that the teeth in ideal normal occlu- 
 
 FiG. 76.— Occlusion of the molar and bicuspid teeth, internal view. (From photograph 
 of a specimen in possession of Dr. F. A. Peeso.) 
 
 sion are said to be "self-cleansing," this cleansing being accomplished 
 by the lips, the tongue, and by the food passing over the surfaces of 
 the teeth. 
 
 Terms Defined. — Occlusion: The relation between the upper and 
 lower teeth when the jaws are closed. 
 
 Arch: A term used to designate the upper or lower teeth collectively. 
 
 Inclined Plane: The sloping surface of a cusp. 
 
 Mesial, Dvital: Position is considered in relation to the median 
 line or center of the dental arches. Hence, "mesial" means toward or 
 nearest to the median line, and "distal ' means away from or farthest 
 from the median line. 
 
A STUDY OF NORMAL OdCLUHION 117 
 
 Model: A reproduction of the dental arch or arches made in plaster 
 of Paris. 
 
 Labial: Toward the Hps. 
 
 Buccal: Toward the cheek. 
 
 Limjval: Toward the tongue. This term is used to describe the 
 upper as well as the lower teeth. 
 
 Protruding: The tipping of the axis of a tooth so that the crown 
 projects labially to normal. 
 
 Retrudmg: The tipping of the axis of a tooth so that the crown 
 slants lingually to normal. 
 
 A STUDY OF NORMAL OCCLUSION. 
 
 Before the student can comprehend any description of malocclusion 
 he must acquire a knowledge of normal occlusion. He should be able 
 mentally to visualize a set of teeth in normal occlusion, as a standard 
 picture with which to compare any set of teeth under examination, 
 in order instantly to detect deviations from the normal. 
 
 Definition. — Normal occlusion is the normal relation of the occlusal 
 inclined planes of the teeth when the jaws are closed (Angle). 
 
 As occlusion means the relation between the upper and lower teeth 
 when the jaws are closed, it follows that normal occlusion means that 
 all the teeth in both arches are so situated that they may best perform 
 their functions, and that their interrelation shall be typical and 
 therefore normal. 
 
 In a set of teeth in normal occlusion the teeth themselves are arranged 
 in symmetrical parabolic curves, commonly called arches. This means 
 that if a line be drawn across either arch, so as to touch the distal sur- 
 faces of the last molars, and a second line be drawn at right angles 
 thereto and through the median space, or between the central incisors, 
 then any two similar teeth on opposite sides of the arch (as for example 
 the first bicuspids) will be equidistant from this central line. 
 
 Perhaps the next most noteworthy fact is that the upper arch is 
 slightly larger than the lower, and that the outer cutting edges and 
 cusps of the upper teeth droop over and consequently hide in part the 
 similar portions of the lower teeth when the jaws are closed (Fig. 
 75). This latter condition is called the "overbite." 
 
 In full denture there are thirty-two teeth. In the illustration which 
 depicts one-half of an upper and lower jaw we should see sixteen teeth; 
 but, as a matter of fact, the artist in endeavoring to expose the full 
 surface of the upper central incisor has so turned the subject that in 
 the lower arch we see an extra tooth, the lower central incisor of the 
 opposite side. Mentally eliminating this extra tooth, by studying 
 the illustration we observe that the smallest incisor is the central 
 incisor in the lower arch, while the smallest molar is the last or third 
 molar in the upper arch. It is in accordance with Nature's wonderful 
 design, which aims to produce the highest efficiency in the use of the 
 
118 MALOCCLUSION OP THE TEETH 
 
 teeth collectively as a masticating apparatus, that this is true, for by 
 this means every other tooth except these four occludes with two 
 others. Again glancing at the illustration we see that the lower 
 lateral incisor is in contact with the upper central and lateral; the 
 upper central touches the low^er central and lateral; the upper lateral 
 antagonizes the lower lateral and cuspid, and so on around the arch, 
 each tooth of either upper or lower jaw occluding with two teeth in 
 the opposing jaw. The most important usefulness of this arrangement 
 is seen when we consider those teeth which have cusps. For example, 
 observe the first upper bicuspid, occluding with the cuspid and bicuspid 
 of the lower arch. Any food caught in this locality is triturated 
 between three powerful cusps, a much more effective plan than were 
 each tooth to strike only one antagonist, as sometimes occurs where 
 malocclusion is present. 
 
 This at once brings us to one diagnostic point. It being a fact that 
 in normal occlusion all the teeth except the lower central incisors and 
 upper third molars occlude so that each tooth antagonizes two, we 
 note that the only place in the entire denture where the interproximal 
 spaces coincide is at the median line. Two facts then may be remem- 
 bered. Whenever any interproximal spaces above and below coincide 
 (except these at the median line), malocclusion exists. Conversely, 
 whenever the spaces at the median line do not coincide, malocclusion 
 is present. 
 
 We should next consider those teeth which are supplied with cusps, 
 viz., the cuspids, the bicuspids and the molars. In regard to the cus- 
 pids and bicuspids, when in normal occlusion the crest or extreme 
 angle of the cusp should be exactly in line with the interproximal 
 space between the two teeth with which it occludes. Or to phrase it 
 differently, a line drawn through the central axis of a cuspid or bicus- 
 pid should pass between the two antagonizing teeth. 
 
 In all the teeth which have cusps, including the molars, each cusp 
 has four slanting surfaces called inclined planes; note that of these the 
 mesial inclined planes of the cusps of the upper teeth occlude with the 
 distal inclined planes of the cusps of the lower teeth; and of course 
 the distal inclined planes of the upper cusps touch the mesial inclined 
 planes of the lower teeth. 
 
 As will be seen presently, however, a point of extreme significance, 
 because used so often as a basis of diagnosis, is the occlusal relation 
 of the upper and lower first molars. The student therefore should 
 become thoroughly familiar with this cusp relation (Fig. 75). The 
 upper molar has two buccal cusps, known as the mesio-buccal cusp 
 and the disto-buccal cusp. In normal occlusion the mesio-buccal cusp 
 of the upper first molar occludes between the mesio-buccal and buccal 
 cusps of the lower first molar, in such a manner that the crest or 
 extreme point of the cusp coincides with a groove in the buccal surface 
 of the lower tooth, known as the buccal groove. It is well also to 
 observe that the mesio-buccal cusp of the lower molar occludes in 
 
MALOCCLUSION 110 
 
 part with the similar cusp of the upper molar and in part with the 
 upper second bicuspid; also that the extreme mesial surface of the 
 lower molar is on a line with the central axis of the upper second 
 bicuspid. Attention is called to this fact here, as it will be again 
 elsewhere, because while in the normal relation the lower first molar 
 is slightly mesial of the upper first molar, it should not be farther 
 forward than the median axis of the upper second bicuspid. 
 
 A study of the same set of teeth from the lingual aspect (Fig. 76) 
 shows similar interlocking of the teeth and the general appearance is 
 the same except that here it is the cusps and incisal ends of the upper 
 teeth that are slightly hidden in consequence of the overbite, the 
 converse of what is true of the buccal view (Fig. 75). 
 
 Summary. — 1. Where teeth are in normal occlusion they are arranged 
 in symmetrical parabolic curves and any two similar teeth on opposite 
 sides of an arch will be equidistant from the central line, or axis. 
 
 2. The upper arch is larger than the lower and the cusps of the upper 
 teeth droop over the lower. This is denominated the overbite. 
 
 3. With the exception of the two lower central incisors and the 
 two upper third molars, each tooth in each arch antagonizes with two 
 teeth of the opposite arch when in occlusion. 
 
 4. The interproximal space at the median line above and below 
 should coincide. When they do not, or when any other interproximal 
 spaces do coincide, a malrelation of the arches is present. 
 
 5. A line drawn vertically through the median axis of any cuspid 
 or bicuspid should pass between the antagonizing teeth. 
 
 6. The mesial inclined plane of any cusp occludes against the distal 
 inclined plane of the opposing cusp; the converse therefore is likewise 
 true. 
 
 7. In normal occlusion the mesio-buccal cusp of the upper first molar 
 occludes between the mesio-buccal and buccal cusps of the lower first 
 molar. 
 
 MALOCCLUSION. 
 
 Definition. — ^Any deviation of the teeth or arches from normal 
 relation is termed malocclusion. 
 
 Malocclusion of Individual Teeth. — A tooth may occupy any one of 
 seven malpositions, and it is even possible for it to be malposed in 
 four ways. 
 
 These malpositions have been named as follows (Angle) : (1) Labial 
 or buccal occlusion; (2) lingual occlusion; (3) mesial occlusion; (4) 
 distal occlusion; (5) supra-occlusion; (6) infra-occlusion; (7) torso- 
 occlusion. 
 
 1. Labial or buccal occlusion means that a tooth crown is so mal- 
 posed that it, is labial or buccal of its true normal position. 
 
 2. Lingual occlusion means that a tooth crown is so malposed that 
 it is lingual of its true normal position. 
 
120 MALOCCLUSION OP THE TEETH 
 
 3. Mesial occlusion means that a tooth crown is mesial of the posi- 
 tion which it should normally occupy. 
 
 4. Distal occlusion means that a tooth crown is distal of the position 
 which it should normally occupy, 
 
 5. Supra-occlusion means that a tooth has erupted to an abnormal 
 height in its socket. 
 
 6. Infra-occlusion means that a tooth has not erupted to a normal 
 height in its socket. 
 
 7. Torso-occlusion means that a tooth is turned in its socket so 
 that it does not occupy its normal place in the arch alignment. 
 
 In explanation of the statement that a single tooth may be in four 
 positions of malocclusion at one and the same time, I would cite the 
 following example: A molar tooth may be in torso-occlusion; in 
 buccal or lingual occlusion; in mesial or distal occlusion; in supra- or 
 infra-occlusion. 
 
 Classification of Malocclusion. — It is manifest, therefore, that there 
 are endless varieties of malocclusion when viewed in the light of 
 single or multiple malpositions of the individual teeth. It remained 
 for Angle, however, to discover the possibility of formulating a classi- 
 fication for malocclusion, independent of these individual malposi- 
 tions but based upon the relations of the two arches considered as 
 units. Other writers have endeavored to erect classifications which 
 do depend upon the individual malpositions, but in none of these is 
 the line of demarcation between the described classes so well drawn 
 that it may serve as an absolute division between the multiplicity of 
 conditions that arise. The result is that often cases are found which 
 might fall into either of two such classes or even into both. For 
 example, we have had classes for "outstanding cuspids" — cases where 
 the cuspids have erupted labially of normal. Again, classes of "open 
 bite," meaning an infra-occlusion or lack of antagonization of the 
 incisors. What are we to do then with a case where we have "out- 
 standing cuspids" complicated with "open bite?" In the Angle 
 classification no such confusion can occur. His lines of demarcation 
 are so distinct, that there can be no lapping of boundaries. 
 
 Of his classification Angle writes:^ "These classes are based on 
 the mesio-distal relations of the teeth, dental arches and jaws, which 
 depend primarily upon the positions mesio-distally assumed by the 
 first permanent molars on their erupting and locking. Hence, in 
 diagnosing cases of malocclusion we must consider first, the mesio- 
 distal relations of the jaws and dental arches, as indicated by the 
 relation of the lower first molars with the upper first molars, the keys 
 to occlusion; and second, the position of the individual teeth, care- 
 fully noting their relations with the line of occlusion." 
 
 Angle then has divided all malocclusion into three great classes 
 dependent upon the mesio-distal relations of the arches considered 
 
 1 Angle, Seventh edition, p. 35. 
 
MALOCCLUSION 121 
 
 as units. It is evident, then, that to make a diagnosis, we must 
 always begin with a picture of normal molar occlusion in the mind, 
 and with the question, "Is the mesio-distal relation of the molars 
 normal on both sides?" The answer to this mental question will 
 invariably classify the case. 
 
 To have such a mental picture w^e must carefully study normal 
 molar relations, as shown in Fig. 75, noting that the mesio-buccal cusp 
 of the upper first molar occludes with the lower first molar in such a 
 way that a line drawn through the apex of this cusp will fall directly 
 into the buccal groove of the lower molar. Or to phrase it differently, 
 the mesio-buccal cusp of the upper first molar occludes between the 
 mesio-buccal and buccal cusps of the lower first molar, whereas the 
 mesio-buccal cusp of the lower first molar occludes between the mesio- 
 buccal cusp of the upper molar and the buccal cusp of the upper 
 second bicuspid. Thus we see that the mesial surface of the lower 
 first molar is normally slightly mesial to the corresponding surface 
 of the upper first molar. Hence, in studying mesial occlusion of the 
 lower first molar, it is important to recognize the limitations of the 
 normal mesial position of this surface in relation with that of its 
 antagonists. When the cusps are not mutilated by caries or bad 
 fillings, however, we may confine ourselves to an examination of the 
 cusp relations. 
 
 The Angle Classification. — In studying a case, if we find that the 
 mesio-distal relations of the upper and lower first molars on both sides 
 are normal, the malocclusion belongs in Class I. 
 
 If the lower first molar on one or both sides is found to be distal to 
 normal in relation wdth the upper first molar, it is said to be in distal 
 occlusion, and the malocclusion falls into Class 11. 
 
 If the lower first molar on one or both sides is found to be mesial to 
 normal in relation with the upper first molar, it is said to be in mesial 
 occlusion, and the malocclusion falls into Class III. 
 
 The distinctions, therefore, between Classes I, II and III are very 
 definite and should be readily comprehended. Some confusion has 
 been caused in the minds of beginners by the fact that there are 
 divisions and subdivisions, but these likewise may be so plainly 
 described that there should be no difficulty whatever. Once having 
 learned to distinguish between Classes I, II and III, we next learn 
 that there are no divisions in Class I nor in Class III. But Class II 
 is separated into two divisions: Division 1, wherein the upper inci- 
 sors protrude, and Division 2, wherein the upper incisors retrude. These 
 are the sole factors by which the divisions of Class 11 are determined, 
 and there remains no more to learn except the subdivisions. A sub- 
 division is any case of malocclusion where the mesiodistal relations 
 of the upper and lower first molars is normal on one side and abnormal 
 on the other. If the abnormality be a distal occlusion, the case must 
 be a subdivision of Class II, because all cases of distal occlusion are 
 in Class II. If the abnormality be a mesial occlusion the malocclu- 
 
m 
 
 MALOCCLUSION OF THE TEST It 
 
 sion must belong to Class III because all mesial occlusions are in 
 Class III. 
 
 The following recapitulation of the classification is copied from 
 Angle, omitting his references to etiological factors with which we 
 are not at the moment interested: 
 
 Class I. Arches in normal mesio-distal relation. 
 Class II. Lower arch distal to normal in its relation to the upper 
 arch. 
 Division 1. Bilaterally distal, protruding upper incisors. 
 Subdivision. Unilaterally distal, protruding upper incisors. 
 Division 2. Bilaterally distal, retruding upper incisors. 
 Subdivision. Unilaterally distal, retruding upper incisors. 
 Class III. Lower arch mesial to normal in its relation to the upper 
 arch. 
 Subdivision. Unilaterally mesial. 
 
 Fig. 77. — Models of a case of malocclusion, Class I. 
 
 To fix the differentiations of this classification more firmly in the 
 mind let us examine the illustrations of a few typical cases. In Fig. 
 77, an examination of the first molars discloses that on each side the 
 mesio-distal occlusal relations are normal. On each side the mesio- 
 buccal cusp of the upper first molar occludes between the cusps of the 
 lower first molar, and a line drawn through the central axis of the 
 mesio-buccal cusp of the upper molar, strikes the buccal grove of^ the 
 lower first molar. This, then, discloses a bilateral normal mesio-distal 
 occlusion of the arches, and the malocclusion consequently falls into 
 Class I. For this illustration a case where the upper incisors protrude 
 has been selected, that by comparison the student may better grasp 
 the difference in the significance of protruding incisors in Class I and 
 Class II, Division 1. 
 
 In Fig. 77, the normal mesio-distal relations of the first molars 
 definitely fixes the case in Class I. Hence the protrusion of the 
 upper incisors has no significance in connection with the classification 
 of the case. 
 
MAL0C(^LlISlOM 
 
 m 
 
 In Fig. 78, an examination of the molars shows that the lower molar 
 on each side is in distal occlusion. The mesio-buccal cusp of the upper 
 first molar does not coincide with the buccal groove of the lower first 
 molar, but on the contrary falls between the mesio-buccal cusp of the 
 lower molar and the buccal cusp of the second bicuspid. The case 
 
 Fig. 78. — Malocclusion: Class II, Division 1. 
 
 therefore falls into Class II, and since the upper incisors protrude, \t 
 must be in the first division of that class. Being bilaterally distal, tnth 
 the upper incisors protruding, it belongs to Class II, Division 1. 
 
 In Fig. 79, we see a case quite like the last, and superficially like 
 Fig. 77, but a study of the molars shows a distal occlusion on one 
 side and normal mesio-distal relations on the other. And as the upper 
 incisors protrude, it is placed in Class II, Division 1, Subdivision. 
 
 Class II, Division 1, Subdivision. 
 
 It is in Class II, because there is a distal occlusion; it is m Division 
 1, because the upper incisors protrude. It is a Subdivision because 
 the distal occlusion is confined to one side. It is therefore unilaterally 
 distal with protruding upper incisors. i , • rru 
 
 In Fig. 80, we find both lower first molars in distal occlusion, ihe 
 
124 
 
 MALOCCLUSION OF THE TEETH 
 
 case therefore belongs to Class II, which includes all distal occlusions. 
 We note that the upper central incisors retrude, for which reason the 
 case belongs to Division 2. It is therefore a case belonging to Class II, 
 Division 2, because it is bilaterally distal with upper incisors retruding. 
 In Fig. 81, we see a case strikingly like the last, except that on close 
 examination we find that the distal occlusion is confined to one side. 
 
 Malocclusion: Class II, Division 2. 
 
 for which reason it must be a subdivision case. It belongs, therefore, 
 to Class II, Division 2, Subdivision, being unilaterally distal with 
 retruding upper incisors. 
 
 In Fig. 82, we find the lower first molars mesial to normal. Indeed, 
 they are so far mesial that they have lost all occlusal contact with the 
 upper first molars, so that the classification is very simple. The case 
 
 Fig. 81. — Malocclusion: Class II, Division 2, Subdi^dsion. 
 
 must belong to Class III, which includes all mesial occlusions. An 
 extreme case has been selected for this illustration, but the actual 
 normal mesio-distal relations must always be in the mind as a mental 
 picture with which the case in hand may be compared, and in the 
 presence of the full complement of permanent teeth, if the lower 
 molar is found to be mesial to normal, the case belongs to Class III. 
 
MALOCCLUSION 
 
 125 
 
 Observe, however, the qualification " in the presence of the full com- 
 plement of the permanent teeth." The premature loss of a temporary 
 molar, or the extraction of a bicuspid may permit a lower first molar 
 to drift abnormally forward, presenting a confusing picture. It is 
 always to be remembered, therefore, that this entire classification is 
 
 Fig. 82. — Malocclusion: Class III. 
 
 dependent upon the presence, or space for the eruption of, all the per- 
 manent teeth, and the drifting of teeth due to extractions or loss of 
 temporary teeth is always a matter for separate consideration. 
 
 In Fig. 83, we find a mesial occlusion on one side, and a normal 
 mesiodistal relation on the other, for which reason the case belongs 
 to Class III, subdivision. 
 
 Fig. 83. — Malocclusion: Class III, Subdivision. 
 
 So much then for the classification or diagnosis of cases in which 
 the first permanent molars are present. It is more than likely, how- 
 ever, that many cases will be seen before these molars are erupted or 
 after they have been badly mutilated or even lost through the ravages 
 of decay. For this reason it is well to note that the occlusion of 
 
126 MALOCCLUSION OF THE TEETH 
 
 the second deciduous molars closely simulates that of the first per- 
 manent molars and consequently these teeth may be used as guides 
 for classification. It has also been mentioned that the permanent 
 cuspids are quite staple landmarks and are useful as guides to the 
 occlusal conditions. At times the bicuspids may be all the individual 
 has to offer from which to classify an abnormality. Hence the student 
 can clearly see that an intimate knowledge of the normal relation of 
 every tooth is absolutely necessary if an intelligent grasp of the 
 abnormal is to be expected. 
 
 Etiology of Malocclusion. — One might write at great length upon 
 the etiology of malocclusion without at all exhausting the subject. 
 In this particular work it does not seem essential to discuss all the 
 theories of all the theorists. The aim will be rather to disclose those 
 facts, the knowledge of which will enable the hygienist to fulfill her 
 avowed purpose of calling attention to, and so far as possible abating, 
 those acts or causes which might bring about or aggravate malocclu- 
 sion. 
 
 The factors involved as causative agents of malocclusion may be 
 divided into the proved and the unproved. As examples of the 
 unproved theories in relation to the causes of malocclusion, enlarge- 
 ment of the tonsils, nasal obstruction, mouth-breathing and adenoids 
 may be mentioned. Whether these maladies do or do not contribute 
 toward malocclusion, they are evidences of a reduced vitality, and as 
 diseased conditions, should promptly be corrected. 
 
 We are told that mouth-breathing causes malocclusions, and that 
 adenoids cause mouth-breathing. Conversely, however, certain good 
 rhinologists hold that mouth-breathing induces adenoids, due to the 
 fact that the inhaled air, normally passing through the nares pro- 
 duces a tonic effect upon the upper pharynx, whereas when taken 
 through the mouth and thus more directly into the lungs, the area 
 usually occupied by the adenoid vegetations misses this tonicity sup- 
 plied by the air, and the hypertrophies are induced. An ordinary 
 rhinitis, or head cold, especially during early infancy, by occluding 
 the nasal air passages, forces the child to breathe through the mouth. 
 If the rhinitis be long neglected, the mouth-breathing, which begins 
 as a temporary necessity, may become a permanent habit. The 
 theory at least sounds plausible enough. Consequently a hygienist 
 who notices any conditions of this character, where her charges may be 
 suffering with a head cold of long standing, should at once warn the 
 parent or guardians of the possible ill-results. Far better would it 
 be for the child to lose a few days' schooling while being kept in bed to 
 cure a cold, than that the habit of mouth-breathing should become 
 fixed. 
 
 Among the proved causes of malocclusion we may enumerate: 
 
 (a) The premature loss of deciduous teeth. 
 
 (b) Extraction of permanent teeth, 
 
 (c) Pernicious habits, and 
 
 (d) Lack of use. 
 
MALOCCLUSION 127 
 
 There are other known causes which may be found in text-books, 
 but those mentioned are of special interest to the hygienist. 
 
 (a) The Premature Loss of TJecidtious Teeth. — The loss or extraction 
 of a deciduous tooth, especially of the cuspids or any one of the buccal 
 teeth, will almost inevitably produce a pernicious effect upon the per- 
 manent teeth. The space made by the loss of the temporary tooth 
 almost invariably closes, in part or entirely, so that the opening 
 needed for the oncoming teeth in that locality is reduced in proportion. 
 
 Why the Sjjace Closes. — In the examination of a three-year-old arch, 
 one wonders where the three large permanent molars will find space 
 for eruption. This space, of course, must be provided by a growth 
 of the maxilla and mandible distal to the deciduous teeth, distal 
 therefore to the last deciduous molar. This growth is coincident with 
 (if not actually caused by) the development and eruption of the per- 
 manent molars. The result is a forward or horizontal movement of 
 the whole temporary arch. Let us study it in detail. To make room 
 for the arriving first permanent molar, the temporary second molar 
 must move forward. To accommodate this movement the first tem- 
 porary molar must move forward, and so on around the arch, each 
 tooth giving way as the tooth behind it advances. Let us suppose, 
 however, that one of the temporary molars has been lost. A space is 
 thus produced so that the first permanent molar may erupt without 
 influencing the forward movement of any of the teeth anterior to the 
 tooth extracted. Indeed, through lip pressure the space may even 
 allow the anterior teeth to be forced backward. In this way, by 
 closing of the space while the underlying bicuspid is yet deep in the 
 bone, the bicuspid may be completely shut out of the arch, so that it 
 either remains impacted, or else must erupt buccally or lingually of 
 normal. 
 
 (6) Extraction of Permanent Teeth. — ^The loss of any permanent 
 tooth breaks up the continuity of the arch and destroys the occlusion. 
 It directly effects no less than five teeth. The two adjacent teeth 
 losing the support of the extracted member, are often forced to drift 
 or tip toward one another. This tipping and drifting is more likely 
 to be extensive when the extraction occurs prior to the eruption of 
 the second molars, as the eruption of these distal teeth induces a 
 disarrangement of the teeth distal to such spaces. This tipping of 
 the teeth interferes with the normal cusp interdigitation of these two 
 teeth with the three antagonists of the opposite jaw. Thus, as has 
 been said, the loss of one permanent tooth may directly spoil the 
 occlusion of five others. Hence, of course, all permanent teeth which 
 can be kept in a state of health, should be preserved when in normal 
 position, and when out of position should be brought to normal 
 occlusion, if possible. 
 
 (c) Pernicious Habits. — In regard to habits, perhaps the most com- 
 mon is sucking the thumb. This phrase, "sucking the thumb," is 
 met throughout the entire literature, and is particularly supposed to 
 
128 MALOCCLUSION OF THE TEETH 
 
 induce protrusion of the upper anterior teeth. But the thumb is not 
 always in the mouth in such a way as to produce this effect, nor is it 
 always the thumb which the child introduces into the mouth. 
 Recently a casual glance into the mouth of a baby girl patient of four, 
 disclosed what seemed to be a protrusion of the upper incisors. The 
 mother was asked, "Does this child suck her thumb?" Like a flash 
 the child replied, "No, I suck two fingers; want to see me?" and she 
 proceeded to give a demonstration. She placed just two fingers of 
 her right hand in her mouth, the finger-tips curled downward under 
 her tongue. In this manner it would seem that the weight of her arm 
 had held the mandible downward and backward, so that a marked 
 example of Class II, Division 1, had been produced, although none 
 of the temporary teeth had yet been shed. The apparent protru- 
 sion of the upper teeth was no real protrusion at all. As the child 
 was not a sufferer from adenoids, had no nasal obstruction of any sort, 
 had never been a mouth-breather, and was the picture of health, it 
 is reasonable to attribute the deformity of the jaws in her case to this 
 peculiar method of sucking the fingers. The thumb is also sometimes 
 introduced into the mouth in the same manner, and not always with 
 the ball of the thumb against the upper teeth. 
 
 Other baneful habits are sucking the lips or the tongue, or habit- 
 ually resting the tongue between the incisors, not forgetting the 
 abominable practice of nursemaids, and some mothers, of giving the 
 baby a "pacifier" or "comforter." 
 
 These habits are particularly mentioned here because it seems prob- 
 able that in the near future the sphere of the dental hygienist will be so 
 broadened that she will enter the homes of many children long before 
 they arrive at the school age, in which case an important part of her 
 duty would be to look for, and warn mothers against, these habits. 
 
 {d) Lack of Use. — ^This brings us to a consideration of a lack of 
 use. It is a commonly accepted physiological law that the use of 
 any organ, or part of the body, contributes toward its development. 
 Normal use results in normal development, where not hindered by 
 other agencies. Abnormal or immoderate use may cause an over- 
 growth, as we see in the muscles of athletes; while disuse results in 
 underdevelopment or even atrophy. 
 
 The Growth of the Jaws. — If we examine the normal child denture 
 at the age of three or four, we observe twenty teeth symmetrically 
 arranged about the arches and completely filling them. When we 
 remember that these twenty deciduous teeth will be succeeded by 
 twenty permanent teeth considerably larger in size, we recognize that 
 if the latter are to erupt in normal occlusion, the bones of the arches 
 must become enlarged, or in other words, there must be a growth 
 increasing the circumference of the arches. Since the growth of the 
 temporary teeth themselves is aheady complete, a growth of their 
 bony supports must result in producing spaces between these teeth. 
 We see this beautifully shown in Fig. 84, which illustrates the upper. 
 
MALOCCLUSION 129 
 
 and lower arches of a boy of four and a half years of age. We have but 
 to glance at such a set of deciduous teeth to see how admirably Nature, 
 when unhindered, will provide for all emergencies. We easily compre- 
 hend that, by growth, space is being provided against the advent of 
 a set of larger teeth. 
 
 But what shall we think of such a set of teeth as is shown in Fig. 
 85? This child was five years of age, six months the senior of the 
 
 Normal growth of dental arches. Aged four and a half years. 
 
 other child, yet we find no spaces between the teeth and consequently 
 no growth of the alveolar bone. We must wonder then, "Where will 
 the permanent teeth erupt?" They certainly cannot appear in proper 
 alignment with such a lack of space. These two models then illustrate 
 well the contrast in appearance of a normally developing deciduous 
 denture with one that is failing to take on proper growth. 
 
 It is but natural to believe that this development of the bones 
 about the deciduous teeth is largely dependent upon the extent and 
 nature of the use or disuse of the teeth. 
 
 
 s 
 
 ^H 
 
 
 5 
 
 9H 
 
 
 1 
 
 p^^^^l 
 
 
 
 ^^B^ ' 't^^^^H 
 
 ^r^P 
 
 B? 
 
 ' ^^1 
 
 r 1 
 
 1 
 
 jl 
 
 
 Fig. 85. — Undeveloped dental arches. Aged five years. 
 
 The normal use of the teeth would necessitate the thorough masti- 
 cation of food; food thus masticated would be properly insalivated, 
 and hence properly prepared for its reception by the stomach. With 
 all the organs of digestion in a state of health, the result would be the 
 thorough assimilation of the food, a correct metabolism, and hence 
 a proper share of the nourishment would finally reach the jaw bones. 
 
130 MALOCCLUSION OF THE TEETH 
 
 so that the thoroughness of the work done by the dental organs would 
 bring its own repayment in the normal share of pabulum brought to 
 the alveolar environments of the teeth. In this manner a normal 
 physiological cycle would be established, and of course any disuse of 
 the teeth would proportionately cause a disarrangement of this cycle. 
 
 While it is well to bear these facts in mind, yet there is another 
 aspect of use and disuse of the dental organs to which attention must 
 here be called. Entirely aside from any interference with the proper 
 nourishing of the body and of the jaw bones, the use or disuse of the 
 teeth directly affects the growth and development of the maxilla and 
 mandible, through the muscular and mechanical forces of mastication. 
 Indeed it is claimed that not only the bones of the jaws, but the 
 entire cranium may be thus affected. To emphasize this fact, a lib- 
 eral quotation is made from an article by Dr. Lawrence W. Baker, 
 published in Items of Interest, February, 1911. 
 
 "Among the first voluntary coordinate muscular actions of a human 
 being after coming into the world is that made with the muscles of 
 mastication in taking food to sustain life. Long before the infant 
 can hold up its head, or has gained control over those useful organs, 
 the hands, the muscles of mastication are highly developed and are 
 used with great vigor. 
 
 "During the act of nursing, the action of this set of muscles is so 
 vigorous that it demands an increased blood supply, to the extent 
 that the heart's action is greatly increased; the excessive flow of blood 
 to these parts is indicated by a reddening of the whole head, and the 
 fontanelles themselves are caused to pulsate so that the untrained 
 observers comment on their movement. 
 
 "Later, with the advent of the dental equipment, this group of 
 muscles is given more leverage, and its action becomes consequently 
 more powerful; in fact, the force exerted on the bones of the head 
 from the pull of these muscles during life is tremendous and amounts 
 to many hundreds of thousands of tons of force. I have long been 
 convinced that this great force on the skull, and the great flow of 
 arterial blood to the head caused by this muscular activity, is a pow- 
 erful influence in the development of the bones of the head and the 
 important organs incased therein. 
 
 "It occurred to me that if the hypothesis regarding the influence 
 of the dental equipment on the formation of the bones of the head were 
 correct, interference with the laws of occlusion in the lower animals 
 would show consequent effect in the formation of the bones of the 
 skull; and if variation occurred it might throw some light on the 
 most complex problem of the development of the human head. 
 
 "To test the theory the following experiment was performed: A 
 litter of four rabbits was selected at the age of weaning. Two of the 
 animals were operated on by grinding down all the teeth on the right 
 side of the lower jaw and the superior right central incisor. As the 
 teeth elongated, repeated grinding rendered them useless, so that 
 
MALOCCLUSION 
 
 131 
 
 all the mastication was performed on the left side. The fourth rabbit 
 was kept in the normal state for a standard of comparison. 
 
 "After seven months, the skeleton of one of the rabbits was pro- 
 cured and the skull was found to vary as shown in Fig. 86, which is a 
 photograph of its upper aspect. It will be noted by the drawn lines 
 that there is a deviation of the bones to the left. (Right and left in 
 this description refers to the right and left side of the animal.) The 
 suture between the parietal and frontal bones does not run strictly 
 at right angles to the longitudinal axis of the skull; the right frontal 
 bone projects farther forward than the left one. It will also be 
 observed that the left zygomatic space is longer and more advanced 
 than the right space. The most noticeable deviation is in the nasal 
 bones, both bones being twisted to the left. 
 
 Fig. 86. — The upper aspect of the 
 skull of a rabbit operated on. Observe 
 the unequal development of each 
 lateral half of the skull. 
 
 Fig. 87. — Lower aspect of Fig 
 
 "On the lower aspect of the skull. Fig. 87, it will be seen that the 
 deviation extends throughout the entire skull. The most remarkable 
 deviation is that the anterior root of the right zygomatic arch (the 
 zygomatic process of the maxillary bone) is retreated while the body 
 of the right maxillary bone itself with the teeth that it contained is 
 greatly advanced. 
 
 "The results of this experiment seem remarkable to me. 
 
 "Who would have thought that by interfering with the laws of 
 occlusion the skull would have decreased in weight, and that every 
 
132 
 
 MALOCCLUSION OF THE TEETH 
 
 suture and every bone in the head would have varied as we have seen? 
 This experiment strongly indicates how important is the masticatory 
 equipment of man to the development of the head, and it also brings 
 fresh illustrations of the importance of the sadly neglected temporary 
 dentition which serves during the important developmental period 
 of childhood." 
 
 The previous quotation gives in full the details of Dr. Baker's 
 experiment, and his findings in one case. His examination of the 
 second rabbit upon which he experimented disclosed exactly similar 
 variations from the normal, whereas the control animal was practi- 
 cally symmetrical.^ Until future experimenters prove these deductions 
 to be erroneous, we may agree with Dr. Baker that the disuse of the 
 teeth may result in extreme interference with the development, not 
 alone of the jaws, but of contiguous parts of the cranium. 
 
 Caries of teeth causing voluntary disuse of the teeth. 
 
 Reasons for Lack of Use. — Disuse of the dental organs may be either 
 involuntary or voluntary. It is involuntary when the habits of masti- 
 cation are hasty, or where the food used is of such a character that 
 heavy mastication is not necessary. "What an injustice, then, is done 
 to children who are fed upon gruels, sloppy food and other articles of 
 diet which require little or no masticatory effort to reduce them to a 
 consistency readily swallowed? 
 
 The voluntary disuse of the teeth is the direct result of caries which 
 renders the chewing of food so difficult, or so painful, that the child 
 elects either to swallow its food unchewed, or else to select food that 
 needs no masticatory effort. 
 
 In Fig. 88, we see the right and left sides of the occluded models of 
 a child four years of age. On the left side of the mouth caries has 
 
 1 Dr. Baker has continued his experiments, and has had exactly similar results with 
 animals other than rabbits. See his report thereon, Dental Items of Interest, July, 
 1916. 
 
MALOCCLUSION 133 
 
 destroyed the little molars and cuspids almost to the gum line. We 
 cannot look upon this picture without thinking of the rabbits, whose 
 teeth Dr. Baker filed or ground away to prevent mastication on one 
 side. When we recall the results of the experiment with the rabbits, 
 we begin to appreciate the seriousness of such conditions in a human 
 young one, during the most stressful periods of development. The 
 word stressful is used because, whereas an adult needs only to restore 
 the tissues of his body which are lost by use, a child must likewise do 
 this and at the same time obtain and assimilate sufficient food with 
 which to increase his weight and stature. How can he do this handi- 
 capped with a masticating apparatus so destroyed? In the experi- 
 ment with the rabbit, Dr. Baker left the little animal with one side of 
 his masticating apparatus perfect, so that perhaps he might properly 
 masticate sufficient food for the proper nourishment of his body. 
 It is this fact that made Dr. Baker's results so significant. There is 
 every reason to believe that the rabbits operated upon ate just as 
 much food as the control animal, so that the divergencies from normal 
 found in the skulls were not attributable to lack of nourishment, but 
 to lack of use of one side of the jaws. 
 
 Fig. 89. — Same case as Fig. 88, occlusal view. - 
 
 The child whose models are shown fared not so well as Dr. Baker's 
 rabbits, because on both sides occlusion was extensively interfered 
 with. The cavities in the teeth are so large that a considerable por- 
 tion of their occlusal areas has been lost, and the approximal con- 
 tacts likewise having been destroyed, the protection of the interprox- 
 imal septa has disappeared, so that food readily packs upon these 
 easily injured and sensitive tissues, with the result that mastication 
 becomes painful, and the child voluntarily declines to use his teeth. 
 
 Fig. 89 shows the occlusal view of these two jaws, and the extent 
 to which caries has destroyed the occlusal contactual area is disclosed. 
 Comparing these models with those shown in Fig. 84 we note the 
 lack of development. 
 
 At this point it may be well to consider again the models shown in 
 Fig. 85. These likewise show lack of development of the arches, yet 
 the teeth themselves are not affected by caries, so the child could 
 
134 MALOCCLUSION OF THE TEETH 
 
 have used them perfectly; therefore it is not to be claimed that disuse 
 is the sole cause of lack of development. It may be the chief cause 
 in some instances and only one of several factors in others. In the 
 case of the child whose models are shown in Fig. 85, the physical 
 history is not known. It will suffice for present purposes to consider 
 two possible hypotheses. While this child cannot have suffered from 
 
 Fig. 90. — Malocclusion due to lack of use. 
 
 voluntary disuse of the dental organs, since the teeth are all sound 
 there may have been involuntary disuse due to the soft nature of his 
 food. Again, considering the perfectness of the teeth, this may not 
 be a case of lack of development at all. There is no definite age at 
 which a particular development of the jaws must occur. We cannot 
 say certainly that the first permanent molars will erupt at a stated 
 
 Same case as Fig. 90, occlusal view. 
 
 age, the incisors at another, the cuspids at another. The writer has 
 seen a complete denture of thirty-two teeth at the age of fourteen, 
 and in another case, the upper cuspids arriving as late as the nine- 
 teenth year, in which case all the previously erupted teeth had likewise 
 appeared long after what is supposed to be the normal time of erup- 
 tion. Looking at a child denture prior to the eruption of the first 
 
M A LOCCL USION 1 35 
 
 permanent molars, if we note growth spaces, as seen in Fig. 84, we 
 may say that normal development is present, but in the absence of 
 such growth spaces, as in Fig. 85, we cannot positively decide. It 
 may be a case of lack of development (as a mere illustration of which 
 the models are used), or it may be a case of slow or tardy development. 
 As examples of a period slightly later than that shown in Ings. 88 
 and 89, Figs. 90 and 91 are introduced. This child's mouth was 
 first examined prior to the appearance of the permanent molars. Not 
 a tooth in the two arches was free from caries. The upper incisors were 
 barely showing above the gum line, and all four were abscessed, for 
 which reason they were extracted, as were three or four others. Com- 
 plete lack of occlusion existed. The child was undersized, anemic and 
 of a generally degenerate appearance. Her father was a physician, 
 however, and after removal of the abscessed teeth he w^as advised to 
 feed the child on food that would yield as much nourishment as possible. 
 It was impossible to obtain models of her mouth; it would have been 
 cruel to try. When next she was seen, two years later, the models here 
 illustrated were made. Even with the eruption of the first molars, the 
 masticating possibilities have not been greatly improved, as they 
 decayed almost as fast as they appeared, so it was said. However 
 that may be, we have here a marked case of prolonged lack of use and 
 malnutrition and cannot be surprised at the resultant malocclusion. 
 On one side we note that the lower molar is in distal occlusion. On 
 the other side the occlusion of the molars is apparently normal, but 
 there is little reason to doubt that the low^r molar has drifted forward 
 because of the premature loss of the two temporary teeth. In any 
 event it is a marked example of malocclusion due to lack of use follow- 
 ing the ravages of caries in the temporary set, so that from this case 
 alone we may gain some cognizance of the possible evils of dental 
 disease which might have been prevented to a great degree by proper 
 attention to mouth hygiene. 
 
CHAPTER V. 
 INFLAMMATION. 
 
 By LeROY M. S. MINER, M.D., D.M.D. 
 
 Inflammation may well be called the cornerstone of Pathology, 
 for an accurate conception of the principles involved in the phenomena 
 of inflammation is necessary in order to have a foundation upon which 
 to build a knowledge of general pathology. 
 
 Inflammation in its various forms is so exceedingly common that 
 without a knowledge of the changes that take place one cannot hope 
 to understand the manifestations which occur in diseased conditions. 
 
 Definition. — Inflammation may be described, in a word, as a response 
 or reaction to an irritation or injury. Its yurpose is twofold: 
 1.. To counteract or neutralize the agent causing the injury. 
 2. To repair the injury produced. 
 
 Thus it is seen that inflammation is intended to be a building up pro- 
 cess; a beneficial effort of Nature to repair damage. Unfortunately 
 it not infrequently happens that under unfavorable conditions it 
 becomes distinctly destructive instead of reparative. 
 
 Classification. — The many types of inflammation have been classi- 
 fied in various ways. The terms most frequently used, however, are 
 (1) acute and (2) chronic. 
 
 It may also be classified according to the location. Catarrhal 
 inflammation affects the epithelial structures, especially the mucous 
 membranes; inflammation is said to be Interstitial, when the connec- 
 tive or supporting tissues are involved; or Parenchymatous, when 
 the functionating cells of an organ are attacked. 
 
 Inflammation has also been described as Ulcerative, when there is 
 loss of tissue by necrosis or gangrene; Exudative, when the process 
 is characterized by unusual exudates as in pleuritic effusion; Sup- 
 purative, when the inflammation ends in suppuration or the formation 
 of pus. 
 
 While these classifications help to describe the location or the type 
 of inflammation, and while the clinical aspects may vary somewhat, 
 it must be firmly borne in mind that the phenomena of the reactions 
 which take place are essentially the same in all forms. The location 
 of the injury will determine to a considerable extent the effect, but 
 the reaction is fundamentally the same. 
 
 Inasmuch as the circulation of both blood and lymph plays a very 
 important role in the phenomena of inflammation, it is necessary 
 to have some knowledge of the normal circulation and also some 
 
TtlE CONSTITUENTS OF THE NORMAL BLOOD 137 
 
 idea of the simpler tissues which may be affected before studying the 
 process itself. 
 
 The Normal Circulation. — The circulation of blood differs in each 
 of the three types of vessels. 
 
 In the arteries, which carry the fresh red blood, the flow is inter- 
 mittent, the red blood corpuscles flow in the center of the vessel 
 (axial core), while between them and the vessel wall is a colorless 
 zone called the plasma zone. The white blood corpuscles travel in 
 this zone and travel much more slowly than the red corpuscles. 
 
 In the capillaries, or the intermediate vessels, the blood flow is 
 slow and continuous. There is no plasma zone. 
 
 The flow in the veins is continuous and slower than in the arteries. 
 The plasma zone is present, but less sharply defined than in the 
 arteries. 
 
 The Constituents of the Normal Blood.— The chief constituents of 
 the normal blood are eight in number, as follows: 
 I. Red blood corpuscles, erythrocytes. 
 II. Blood platelets. 
 
 III. Polymorphonuclear leukocytes (leukocytes with many nuclei). 
 
 IV. Endothelial leukocytes. 
 V. Lymphocytes. 
 
 VI. Eosinophiles. 
 VII. Mast cells. 
 
 VIII. Blood plasma. 
 
 Groups III to VII are various types of white blood cells. 
 
 The red blood corpuscles are bell- or cup-shaped masses of cytoplasm 
 containing no nucleus. One cubic millimeter of blood under normal 
 conditions contains 4,500,000 to 5,000,000 red corpuscles and at birth 
 about 6,000,000. These corpuscles are not permanent cells, but are 
 short-lived. Their function is the carrying of oxygen, which forms a 
 loose combination with hemoglobin, which is the most important 
 constituent found in the protoplasm of these cells. The red blood 
 corpuscles are derived from the erythroblasts of the bone-marrow. 
 
 The blood platelets are round or oval disks about one-half the size 
 of the red blood corpuscles. One cubic millimeter contains 250,000 
 to 500,000 platelets. 
 
 The white corpuscles grouped together are present in much smaller 
 numbers than the red blood corpuscles, there being only 8000 per 
 cubic millimeter on the average. There are about 600 red to 1 white 
 corpuscle. 
 
 The polymorphonuclear leukocytes are the most frequently found 
 white corpuscles and form 70 to 72 per cent, of the total number. 
 They are larger than the red blood corpuscles. Under the microscope 
 the nucleus of this cell attracts attention. The nucleus is irregular 
 and has rounded lobules. The cell membrane is sharply defined. 
 These cells are formed in the bone-marrow also. 
 
138 ■ INFLAMMATION 
 
 Endothelial leucocytes or mononuclear leukocytes are larger even 
 than the polymorphonuclear cells, being two or three times as large 
 as the red blood corpuscles. In number they make up only 2 to 4 per 
 cent, of all the white cells. Ihey are derived from the endothelial 
 cells lining the bloodvessels. 
 
 The lympJwcytes are found most frequently next to the polynuclear 
 cells. They form 22 to 25 per cent, of all the white corpuscles. They 
 are about the size of the red corpuscles. The appearance is charac- 
 teristic. The cells are round and they take the stain well, especially 
 the periphery. Lymphocytes are produced in lymphoid tissue and 
 especially in the lymph nodes. 
 
 Eosinophiles make up 2 to 4 per cent, of the total leukocytes. The 
 nucleus is frequently shaped like a horseshoe, and the cell itself may 
 be larger than the polynuclear leukocytes. It derives its name from 
 the intense staining with eosin. They are derived from bone-mlarrow. 
 
 The mast cells make up but five-tenths of 1 per cent. They are 
 also derived from bone-marrow. 
 
 Blood plasma is the fluid part of the blood and contains fibrin, 
 which plays an active part in the phenomena of coagulation. With 
 the fibrin removed the plasma is called serum. 
 
 In addition to this brief study of the blood and its circulation it 
 may be well to mention some of the basic histological structures which 
 are concerned in the study of the inflammatory process. They are 
 as follows: 
 
 I. Connective tissue (fibroblasts). 
 II. Endothelial cells. 
 
 III. Nerves. 
 
 IV. Lymph vessels and spaces. 
 V. Bloodvessels. 
 
 Connective Tissue. — The function of this tissue, as the name sug- 
 gests, is to bind or support other tissue. The cell of which it is formed 
 is called the fibroblast. These cells, as a rule, are flat, elongated cells 
 with oval nuclei. The fibroblast frequently plays an important part 
 in inflammatory processes. 
 
 Endothelial Cells. — ^These cells line the blood and lymph vessels. 
 In form they are flattened and have an oval nucleus. 
 The inflammatory process may be divided into three parts: 
 I. The injurious agent or the cause. 
 11. The injury done to the tissues. 
 
 III. The resulting reaction to the injurious agent and to the injury. 
 The Injurious Agent or Cause. — Some writers have classified the 
 causes of inflammation under two headings: 
 
 1. The predisposing cause. 
 
 2. The exciting cause. 
 
 As a predisposing cause of inflammation age may be mentioned. 
 In growing children, the nutritional and developmental changes pre- 
 dispose to inflammation of the mucous membranes. The frequency 
 
PLATE IV 
 
 The Elements of Normal Blood. (Simon.) 
 
 a, red cells in rouleaux; h, crenated red cells; c, finely granular (neutrophilic) leuko- 
 cytes; d, coarsely granular (eosinophilic) leukocytes; e, small, and/, large mononuclear 
 leukocytes; g, plaques. 
 
TUK INJflU/OllS A(1I<:NT ()]i CAUSE V.'>\) 
 
 of stomatitis in cliildren i« an exaiiii)ic. In old aj^e the loweriiiK of 
 the resistance i>re(Hsp()ses to the infianiniations of bacterial orif^in. 
 Bronchitis is an example. Fatigue and worry are said to be predis- 
 posing causes. Any condition that lowers the natural resistance may 
 be regarded as a predisposing cause. 
 
 The exciting cavse, or the active injurious agents may be di\'ided 
 into three groups: 
 
 I. Mechanical: cuts, blows, foreign bodies. 
 II. Physical: heat, cold, sunlight (sunburn), electricity, .r-ray, 
 
 radium. 
 III. Chemical: 
 
 (a) Inorganic compounds: acids, alkalies, poisons. 
 
 (b) Organic: microorganisms, bacteria and their toxins. 
 This last group, especially the bacteria, form the chief cause of 
 
 inflammation. In fact, so commonly is bacterial invasion the cause 
 that it has been incorrectly assumed that inflammation was dependent 
 upon bacteria or their products. As a matter of fact the lesions pro- 
 duced by the injurious agents other than bacteria are identical to 
 those of bacterial origin. 
 
 It is not necessary to go into great detail regarding the bacteriology 
 of inflammation, but some of the more common bacteria may be briefly 
 described. The three most common organisms are the Staphylo- 
 coccus pyogenes aureus, Streptococcus pyogenes and the pneumo- 
 coccus. 
 
 The staphylococcus is found on the skin, or in the mouth, and is 
 very common. It may possess little or no virulence, or it may become 
 extremely pathogenic when abnormal conditions exist. It is the most 
 frequent organism found in pus. It is a small, round cell and tends 
 to form in groups or clusters. When grown artificially it produces 
 a distinctly yellowish color in the medium. 
 
 The streptococcus is a more dangerous organism, but it is not so 
 common as the staphylococcus. It is not infrequently found in the 
 mouth and nose. It is often found in suppurative conditions with 
 the staphylococcus. It is a spherical organism which has the char- 
 acteristic of growing in chains. 
 
 The pneumococcus is found frequently in inflammatory conditions. 
 It is said to be a normal inhabitant of the mouth. Morphologically 
 these organisms appear like elongated cocci and tend to grow in pairs 
 or short chains. Under some conditions a well-defined capsule is seen. 
 This organism has been found very frequently in the inflammatory 
 conditions of the alveolar process, commonly known as pyorrhea 
 alveolaris. The Bacillus pyocyaneus, typhoid bacfllus, colon bacillus 
 and tubercle bacillus are other notable examples of pathogenic bacteria 
 which produce their more or less characteristic inflammations. 
 
 The action of an injurious agent may be severe or slight, brief or 
 prolonged. The eft'ect varies accordingly. Some agents produce a 
 lesion very quickly, others only after acting over a long period of 
 
140 INFLAMMATION 
 
 time. The action may be local or general: local, as in the case of a 
 blow; general, as in the case of diphtheria toxin. 
 
 The Injury. — Definitions. — Injury is the term applied to the changes 
 produced in tissues and organs by harmful agents. 
 
 Lesion is the term applied to any structural change in tissues and 
 organs, no matter how produced. 
 
 Necrosis means death and may be used to indicate death of any 
 tissue, or of a single cell. 
 
 It is possible for injury to have been done without being able to 
 demonstrate it. In tetanus and rabies it may be impossible to demon- 
 strate any morphological change, even though the reaction is most 
 violent. Thus it is seen that inflammation is not necessarily a local 
 reaction. 
 
 The Reaction. — ^The reaction to an injurious agent is the most inter- 
 esting. This reaction naturally varies very considerably, and this 
 depends on the amount and nature of the injurious agent and on the 
 severity of the injury. It may be evidenced in three ways: 
 
 I. By chemical changes, as alteration in secretion or excretion. 
 II. By morphological changes, as the presence of serum, fibrin and 
 
 proliferated cells. 
 
 III. Physiologically, by alteration in functional activity. 
 
 As already stated, the object of the reaction is to get (a) rid of the 
 injurious agent, if it is still present; (b) to neutralize its action; and 
 (c) to repair the injury which has taken place. 
 
 The chemical and physiological changes are usually less prominent 
 than the morphological changes. The changes in the blood following 
 poisoning by illuminating gas is a good example of the chemical change. 
 The convulsions produced in poisoning by strychnine illustrate the 
 physiological changes. 
 
 Inasmuch as the morphological changes are most frequently seen 
 and have been the most thoroughly studied, this phase of the subject 
 can be studied to advantage. 
 
 The morphological changes (which are partly chemical) which take 
 place in tissues following an injury are as follows: 
 I. Circulatory disturbances. 
 
 II. Inflammatory exudation. 
 
 The Circulatory Disturbances. — ^These occur in the following order: 
 
 1. A momentary spasm in the bloodvessels, when the irritant 
 flrst acts. 
 
 2. Dilatation of the vessels with a more rapid flow. 
 
 3. The vessels still further dilate and become engorged, but the 
 flow decreases, and may even stop in some of the capillaries and veins. 
 The leukocytes become attached to the walls of the veins. 
 
 4. The transmigration of the leukocytes. 
 
 These cells, especially the polynuclear form, have been called the 
 soldiers of the blood, for they rush to the seat of injury and slowly 
 but surely pass through the vessel wall into the tissues (ameboid move- 
 
PLATE V 
 
 a b b' 
 
 • 
 
 • ' • 
 
 '■m^' 
 
 f 
 
 f 
 
 a, macrolymphoblast ; b, microlymphocyte; b', older form; b", monocytoid form ; 
 c, macrolymphoidocytes ; c', monocytoid forms; d, microlymphoidocytes; e, Rieder 
 forms of macrolymphoidocytes;/, large monocytes. (Simon.) 
 
SYMPTOMS OF INFLAMMATION 141 
 
 ment) and invade the masses of bacteria, or surround the irritant if 
 non-bacterial and attempt to destroy them. These cells themselves 
 are killed in great numbers by the actions of the product of the bacteria, 
 namely, the toxins. 
 
 The endothelial leukocytes appear later in the inflammatory proc- 
 ess, when the polynuclear forms are diminishing in number, acting 
 as a sort of reserve guard. They accumulate to counteract the toxins 
 of the bacteria and to attend to foreign bodies, carbon and free fat. 
 These cells destroy certain forms of bacteria by enveloping them in 
 the cell structure. Phagocyiosis is the term used. 
 
 The lymphocytes are seen most abundantly after the inflammation 
 has existed for some time, and are quite characteristic in what we 
 know as chronic inflammation. 
 
 Symptoms of Inflammation.— While these changes are taking place 
 in the tissues, certain symptoms of the inflammatory process have 
 appeared, of which the patient is very conscious. These symptoms 
 are four, to which a fifth is sometimes added. They have been called 
 the cardinal signs of inflammation and are classic. These are : Rubor; 
 calor; tumor; dolor; the fifth, functio l^sa; translated these are: red- 
 ness; heat; swelling; pain, and impaired function. _ _ 
 
 1. The redness is due to the increased flow of blood. Hyperemia is 
 the term that is sometimes used to distinguish the early stage of 
 inflammation. As the flow begins to decrease, the color begms to 
 become bluish in appearance. 
 
 2. The local heat at the site of the inflammation never exceeds the 
 temperature of the internal organs, although it may be above the 
 normal temperature of the part. No heat is produced in the affected 
 area. The increased temperature is due to the increased rapidity of 
 circulation and to the increased volume of blood. 
 
 3. The swelling is produced by the exudation from the blood- 
 vessels. 
 
 4. The -pain is due to pressure on the nerves by the exudates. It 
 is often possible to count the heart beat by the exacerbations of 
 pain. The pain is most severe in dense structures, especially when 
 the inflammation is confined in bony walls, as in the pulp of a tooth. 
 This pain is sometimes referred to a point distant from the seat of 
 trouble, as for example, earache in case of pulpitis. 
 
 5. The disturbance of function is especially seen m the eftect on 
 secretions, which many times are prevented or suppressed Also 
 movement may be limited, as seen in stiffness in a joint that is inflamed. 
 
 The Inflammatory Exudate.— Associated with or foflowmg closely 
 after the transmigration of the white cells, there is an exudation of 
 lymph from the lymph vessels, the purpose of which is to neutralize 
 or to reduce the chemical activity of toxins given oft* by bacteria or 
 other products present in the tissues. The exudation of lymph is 
 seen, as an illustration, in a mosquito bite. We have here a chemical 
 poisoii, and we get all the changes incidental to inflammation, ihat 
 
142 INFLAMMATION 
 
 is, the change in the circulation; the increase in rapidity, then the slow- 
 ing down of the blood stream, the transmigration of the leukocytes, 
 and finally the throwing out of lymph. This is a small inflammation, 
 but it has all the phenomena of a more extensive one. 
 
 If at this point, the most important purpose of the inflammatory 
 reaction has been accomplished, namely, to counteract or neutralize 
 the agent causing the injury, the inflammation subsides, the early 
 products of the inflammatory process are absorbed and the tissues 
 soon return to a normal condition. 
 
 Unfortunately, however, especially where bacteria are concerned. 
 Nature is not always successful, and other phenomena appear. Further 
 exudates are thrown out; the exudation becomes more complicated, 
 and other substances besides the lymph are thrown out. These 
 exudates vary under different conditions. 
 
 Types of Exudation.- — I. Serous exudation is watery in consistency, 
 and is quite similar to lymph; in fact, it resembles it very closely, and 
 some writers simply regard the serous type as an unusually free 
 exudation of lymph. In this form the lymph spaces are particularly 
 involved and the swelling is known clinically as edema. This is seen 
 sometimes in a sprain. Pressure with the thumb or finger over the 
 swollen area will usually leave an indentation, where the serum has 
 been forced out of the tissues by the pressure. This identation 
 gradually disappears as the pressure is removed and as the serum 
 flows in again. 
 
 Another example of this serous type of exudate is a blister from an 
 ordinary burn, or from irritation, or friction. 
 
 II. Fibrinous exudation consists of leukocytes and the formation 
 of fibrin and occurs most characteristically in the form of a membrane. 
 A good illustration of this is the membrane formed in diphtheria. 
 
 These membraneous exudates vary in their characteristics. Some 
 are firmly adherent to the underlying tissues, while others may be 
 readily peeled off, leaving sometimes a bleeding and sometimes a 
 smooth surface. 
 
 III. Suiypurative exudation is the most frequent and most impor- 
 tant form, and is characterized by the formation of yus. This is the 
 most common ending of acute inflammation, especially when bacteria 
 are acting as the injurious agent. 
 
 In the discussion of inflammation caused by bacteria, it was shown 
 that leukocytes were clustered together and the lymph had been thrown 
 out. What is the next phenomenon to appear? It is briefly that the 
 large number of leukocytes which gather in the tissue form an impair- 
 ment of the nutrition of the tissue in which they are located; and we 
 are so made up economicafly, so far as our tissues are concerned, that 
 the nutriment supplied to the tissue is not sufficient to nourish the 
 tissue itself and also these leukocytes, with the result that the tissue 
 cells themselves lose their vitality; and then, also, the leukocytes in 
 giving battle to the bacteria are destroyed in large numbers, either 
 
PLATE VI 
 
 
 
 
 •.•:'y.v>!. 
 
 ^•iSim:, 
 
 
 
 ^mm 
 
 a, typical leukoblast; b, old form; c, monocytoid form; d, neutrophilic myelocytes; 
 e, neutrophilic metamyelocytes;/, polymorphonuclear neutrophiles. (Simon.) 
 
SYMPTOMS OF INFLAMMATION 143 
 
 by the bacteria or their toxins. This lack of nutrition, this dying of 
 the tissue cells in which the inflammation is located, and the death of 
 the leukocytes themselves, cause a dissolution of the tissue, and as a 
 consequence there is a cavity filled with dead leukocytes, dead tissue 
 cells, lymph and dead and living bacteria, which forms a creamy 
 fluid called pus. Clinically this is known as an abscess. 
 
 The formation of an abscess marks the end of the inflammation, 
 so far as the tissues themselves are concerned; that is, the inflamma- 
 tory process has been limited and localized. 
 
 The leukocytes which transmigrate into the tissues entirely surround 
 the seat of injury and /on?? a protectimj wall against further invasion. 
 
 If it were not for this action of the leukocytes in forming this wall 
 between the general circulation and the injurious agent in the form of 
 bacteria, each time we received an injury infectious in its nature, 
 that is, of bacterial origin, we would either have a general blood 
 poisoning because injurious products would be taken up by the circu- 
 lation, or the inflammation would extend indefinitely out into the 
 tissues until our bodies were wholly consumed by the inflammation. 
 Therefore this formation of an abscess, while disagreeable, painful 
 and uncomfortable, in itself is an excellent thing, because it prevents 
 the disturbance from becoming a general one of very serious conse- 
 quences. 
 
 Occasionally the leukocytes are unable to control the local action, 
 or perhaps the infection began in the circulation, and in that case 
 general blood poisoning or septicemia results. This is a very serious 
 condition. But, fortunately, the leukocytes generally form an actual 
 resisting force, or limiting membrane, through which the bacteria are 
 unable to pass and inside of which is this pus cavity. 
 
 The next question that naturally arises is, what becomes of the pus 
 and this wall of leukocytes? The tendency of all abscesses is to 
 evacuate themselves; that is, to throw off their contents, and get rid of 
 the secretion that exists. The method of doing this is as follows: 
 The fluid elements of the abscess cavity, or the pus, increases in 
 amount, and the increase in quantity increases the pressure around 
 the tissues, and as this fluid element continues to increase, the pressure 
 becomes greater and greater, and as the pressure becomes greater 
 the tissue before it gradually yields, and the pus finds its way in what 
 has been classically called the path of least resistance. This act of 
 Nature in endeavoring to throw off the pus has been called the bur- 
 rowing of pus. It tries hard to get through to the surface of the 
 body, or to a cavity, and burrows its way through the tissues in the 
 path of least resistance. When the pus has finally approximated the 
 surface, we have what is known as pointing. This term is well known. 
 Years ago it was customary to poultice any inflammatory condition 
 to bring, as they said, the trouble to the surface, and this poulticing 
 was intended to hasten the action of the pus burrowing, to hasten 
 the pointing of the abscess so that the contents could be evacuated. 
 
144 INFLAMMATION 
 
 If an abscess is not surgically opened and the pus discharged, the 
 tissues will spontaneously rupture and the pus will escape, either on 
 the surface of the body somewhere, or else into one of the cavities of 
 the body, as has been suggested. For instance, if an abscess on the 
 lower jaw results from an inflamed tooth, the path of least resistance 
 may be downward and a large swelling occurs under the jaw. As 
 the pus comes closer and closer to the surface it either is opened and 
 evacuated surgically, or else it may point and discharge underneath 
 the chin. If there is an abscess, for instance, in the appendix, and it 
 is allowed to go uncared for until it ruptures, it ruptures into the 
 abdominal cavity and peritonitis results. The pus, in other words, 
 tries to escape from the tissue and come out freely, and thus relieve 
 the pressure on the tissues in which the abscess has formed. 
 
 The channel through which the pus passes is called a sinus, and the 
 opening on the surface is called a fistula. These two terms are very 
 common, especially in inflammatory conditions connected with the 
 mouth and teeth. We speak of a sinus, for instance, when a chronic 
 abscess discharges into the mouth over a tooth on the gum. The 
 canal or channel through which the pus escapes to the surface is the 
 sinus, and the opening on the gum out of which the pus comes is 
 the fistula. 
 
 If the abscess is a very superficial one, it is merely a simple abscess 
 of the skin. When the pus comes through the surface the layers of 
 the skin may be destroyed, leaving more or less of an open wound 
 of a very superficial nature. This condition is known as an ulcer. 
 
 Chronic tiflammation. — Before discussing repair or what takes place 
 after the pus is evacuated, chronic inflammation may be briefly 
 described. Chronic inflammation is the result of a continued irrita- 
 tion. It may follow acute inflammation, or it may start as inflamma- 
 tion of a chronic form. Chronic inflammation is a very different 
 process from the acute form, and some writers have gone so far as 
 to say that chronic inflammation is not a true inflammation at all. 
 The essential feature of chronic inflammation is the formation of new 
 connective tissue, a proliferation of the fibroblast, or connective-tissue 
 cell. The term fibrosis has sometimes been applied to this form of 
 tissue change, because it describes the condition better than the term 
 chronic inflammation. 
 
 In this chronic inflammatory process, hyperemia, or change in the 
 bloodvessels, that is, the bringing of additional blood to the part, 
 edema, the throwing out of the lymph and suppuration, the formation 
 of pus, are absent. Instead there is this proliferation, as it is called, 
 of the connective-tissue cell, and the throwing out of some of the white 
 cells of the blood, particularly the lymphocytes. The chief character- 
 istics, then, are the formation of connective tissue, the fibroblastic 
 proliferation and the lymphocytic infiltration or throwing out of these 
 lymphocytes. No pus is found nor other symptoms of the inflam- 
 matory changes. 
 
SYMPTOMS OF INFLAMMATION 145 
 
 Repair.— Repair is the general term used to describe the processes 
 taking place after injury and exudation caused by harmful agents. 
 The repair of tissue or the repair of the injury is a very complicated 
 subject but it includes three divisions which will be briefly described: 
 
 First, repair includes removal of foreign bodies of all sorts; and by 
 foreign bodies is meant dead cells of all kinds: (I) Tissue cells that 
 have died as the result of the process, (2) leukocytes of the polynuclear 
 form, (3) endothelial leukocytes, (4) bacteria dead and alive. 
 
 The absorption and removal of foreign bodies such as sutures should 
 also be included. There may be an operation and stitches are taken 
 deep in the body. These stitches are allowed to stay there, and they 
 are removed as foreign bodies, and this is part of the function of repair. 
 In addition, secretions from bacteriological products, the toxins, and 
 in some cases the lime salts which are formed as the result of the 
 various conditions are included; in fact, the removal of anything that 
 is foreign, or is not of service in the tissue is one of the functions of 
 repair. 
 
 Second, the organization of fibrin. 
 
 Third, the regeneration of cells to restore the part which has been 
 destroyed. 
 
 I. How does the removal of the foreign bodies take place? In 
 a word, the leukocytes, or white cells, change somewhat their function, 
 and they become active in carrying off the foreign bodies. 
 
 These dead tissue cells are destroyed and removed in part, a little 
 at a time. The bacteria may be actually digested by the leukocytes 
 after being taken up by these cells. Very frequently under the 
 microscope these endothelial cells may be seen with several bacteria 
 in their protoplasm. The endothelial leukocyte is especially active 
 in this part of the process. The phenomenon is called phagocytosis. 
 
 II. The fibrinous exudate is taken care of by the connective- 
 tissue cells, the fibroblasts, which form and grow into the fibrin and 
 gradually replace it. 
 
 III. The regeneration of cells is the growth of new cells, and is 
 brought about by what we know as cellular division, or mitosis. 
 Under stimulation, the cells in the vicinity of the wound will gradu- 
 ally begin to multiply and fill in the vacancy that is caused by the 
 destruction of the tissue, and gradually this cavity or the injury due 
 to loss of tissue is replaced by new cells, which have divided and 
 redivided and divided again. 
 
 Clinically speaking, repair or the healing of wounds takes place in 
 two ways: {1} By primary heahng, as we know it, called healing by 
 first intention; and (2) by secondary healing, or healing by second 
 intention, or healing by granulation tissue. 
 
 Healing by First Intention. — To illustrate the healing by first inten- 
 tion, let us assume we have an incised wound. After the bleeding 
 is stopped the wound, which is the result of a cut remains filled with 
 blood, and this blood coagulates and forms a sort of plug in the 
 wound. This plug or coagulated blood retracts and tends to hold 
 
146 INFLAMMATION 
 
 the edges of the wound together, and over the surface a crust is 
 formed, which is nothing more than dried secretion, dried lymph 
 plus a few cells, and this is commonly spoken of as scab. The healing 
 process begins at once. Of course, the various stages of inflammation, 
 the changes in circulation, and throwing out of the leukocytes must 
 occur, but all of the cardinal symptoms of a true inflammation may 
 not be present. In addition to the throwing out of the leukocytes, 
 the connective-tissue cells become active; and this blood-clot, which 
 has been mentioned above, acts as a sort of scaffolding, upon which 
 the connective tissue builds, sending out little prolongations of tissue. 
 This connective tissue gradually replaces the blood-clot and the edges 
 of the wound are held firmly together. Then if the wound is on the 
 surface, the epithelial coverings will send out prolongations and heal 
 it over with no evidence of scar. If the edges of the wound after a 
 cut are held firmly together, for instance, with plaster or a bandage, 
 very little connective tissue is formed. It takes very little new 
 tissue to repair the wound; but if it is a gaping wound, more material 
 is needed to repair it; and where a portion of the surface of the skin 
 is lost and it becomes impossible for the epithelial cells to span the 
 breach, the connective tissue fills it in, and the result is known as a 
 cicatrix. The tissue which forms is called cicatricial tissue, or scar 
 tissue. This has a very great tendency to contract. As these new 
 cells become older they contract somewhat, and the contraction of 
 scar tissue is well known. The scar tissue that results where the 
 epithelium is not completely restored, for instance, on the hand, is 
 not original skin tissue, but it is made up of connective tissue. 
 
 Healing by Second Intention. — It has been shown that healing by first 
 intention has nothing to do with infection; that is, bacteria have 
 been absent in the changes that have taken place. In repair, by 
 second intention, however, the suppurative process, and all the phe- 
 nomena of inflammation with the formation of pus and the evacuation 
 or throwing out of pus cells, and the products of exudation must occur 
 before the actual healing. When this takes place, the cavity which 
 results from the pus is filled in gradually by granulation tissue and 
 connective tissue in much the same way as in healing by first inten- 
 tion; but there is much more tissue to be restored, and the healing 
 process may be slow, particularly if the cavity is large. It is often 
 possible, after the pus has spent itself and the acute symptoms have 
 subsided, to bring the edges of a wound together and have it heal by 
 first intention, but that is not customary. If instead, in this type 
 of wound the opening is packed with gauze, and allowed to fill in, as 
 we say, from the bottom, the granulation tissue fills up gradually, and 
 each day less gauze is used in the packing until the cavity is filled in 
 solidly with this connective tissue. This healing by granulation becomes 
 very important under some conditions, because the contraction is 
 sometimes excessive. If there is a severe inflammation or a bad 
 abscess of the cheek, for instance, or the cheek muscle and the wound 
 has to be repaired by second intention, or by granulation healing, 
 
PLATE VII 
 
 ■.-W" o 
 
 /© 
 
 • 
 
 • 
 
 Granulocytes. (Simon.) 
 
 a, polynuclear neutrophilic leukocytes; b, polynuclear eosinophilic leukocytes; c, mast 
 cells; d, eosinophilic myelocytes; e, neutrophilic myelocytes (the smaller myelocytes 
 represent the micro-, the larger ones the macro-type) ; /, the nucleus here has just under- 
 gone division; the clear space is a vacuole. 
 
INFLAMMATION OF BONE 147 
 
 after a while this contraction of the cicatricial tissue may be so great 
 that the person is unable to extend the lower jaw or open the mouth, 
 and thus a very serious condition may be developed. Fortunately 
 this is not common. 
 
 Repair then in general is the effort of Nature to restore the tissues 
 to a normal condition after an inflammation; and when the repair is 
 complete, especially if it is by first intention, the parts have been 
 restored to function and the cells resume their normal relations. 
 
 INFLAMMATION AND REPAIR OF BONE. 
 
 Introduction. — We ordinarily regard the bones as more or less station- 
 ary in the structure during life, but they are in fact the site of constant 
 cellular activity and are subjett to continual alterations in size, shape, 
 strength, density and composition. All bones possess ridges or 
 processes that have a definite anatomical or physiological reason for 
 existence but which begin to disappear at once when their function is 
 fulfilled. The most conspicuous example of this is the alveolar proc- 
 ess of the jaw which is especially designed to support the teeth. 
 These alveolar processes maintain their integrity under normal con- 
 ditions when the teeth are present, but are absorbed in a comparatively 
 short time when the teeth are lost. The cells that serve to maintain 
 the integrity of bone or to remove unnecessary portions, as the case 
 may be, are the osteoblasts or bone formers, and the osteoclasts or 
 bone destroyers. These cells are also active in repair of bone. 
 
 INFLAMMATION OF BONE. 
 
 Inflammation may occur in the covering membrane or periosteum 
 of bone and is called periostitis. Ostitis is an inflammation of the 
 marrow, and osteomyelitis is the term used when all parts of the bone 
 are affected. Clinically it is quite difficult, especially in the bones 
 of the face, to differentiate the two latter forms and the general term 
 osteomyelitis is commonly used. 
 
 Etiology. — Causes of inflammation of bones are similar to causes of 
 inflammation of other tissues. Traumatism and infection are the 
 most common factors. 
 
 Periostitis. — Inflammation of the periosteum, or osteogenetic mem- 
 brane, may be acute or chronic. In the acute cases the periosteum 
 becomes swollen and exquisitely tender and the accompanying pain is 
 usually quite severe. This condition is occasionally seen in the jaw 
 after the injection of novocain under the periosteum, particularly 
 when care has not been taken. If infection occurs, a subperiosteal 
 abscess may result. The pericemental abscess so frequently seen 
 along the root of a tooth or its socket is a good example of a modified 
 periostitis. 
 
 Osteomyelitis. — The term used to describe inflammation of the bony 
 structure itself. This may occur from a previously exciting peri- 
 ostitis or may be the direct result of accident or infection. This 
 
148 INFLAMMATION 
 
 condition is quite disposed to go on to formation of pus which tends 
 to collect in cavities of the bone made by the destruction of the bone 
 .cells. 
 
 Necrosis of Bone. — The end-result of many cases of osteomyelitis. 
 This takes place when the nutrition of the bone has been interfered 
 with. The bone, as a result, loses its vitality and death or necrosis 
 sets in. 
 
 The extent of the necrosis depends on the severity of the case. 
 The portion of the bone that becomes necrotic is called the seques- 
 trum. In the larger bones this sequestrum may occupy a central 
 position, that is in the marrow cavity, and rarely this may be 
 observed in the lower jaw, or the sequestrum may be a superficial 
 or subperiosteal one. 
 
 Repair of Bone. — The repair of bone is similar in many respects to 
 repair of soft tissue, but differs from it in several important points. 
 Any dead or necrotic bone is much more resistant than soft tissue 
 and the polymorphonuclear and endothelial leukocytes find it much 
 harder to remove and absorb. As a result the necrotic bone persists 
 for a much longer time in the lesion; acts as a real foreign body and 
 interferes with repair so long as it is not removed either naturally or 
 surgically. It may be dissolved very gradually by the action of 
 endothelial leukocytes, many of which become fused to form the 
 foreign body giant cells that appear so characteristically in this process. 
 These are sometimes called osteoclasts because of the function they 
 perform. 
 
 New bone is not found in a solid mass but in narrow trabeculse with 
 connective tissue richly supplied with blood between them. An excess 
 of tissue is found during the process of repair which occupies more 
 space than the healed bone will eventually occupy. Later these 
 trabeculse fuse more or less completely together and the parts not 
 required are absorbed by the osteoblasts. In repair of a fracture of 
 bone, osteoid material is found around the ends of the fragments at 
 point of fracture in a sort of tumor mass which acts as a kind of splint. 
 This formation is called callus. Later the excess tissue is removed so 
 that the size of the bone at point of fracture is nearly the same as 
 normal. 
 
 There is considerable difference of opinion regarding what tissue 
 furnishes material for new bone growth. It is very well accepted that 
 periosteum and endosteum function in this capacity and furnish 
 fibroblasts that produce osteoid material which forms the basis for 
 new bone. It was formerly thought that bone cells themselves cannot 
 do this and many still hold to this belief. It is the opinion of compe- 
 tent observers, however, that new bone growth does not come entirely 
 from the periosteum and endosteum but does come from the bone 
 cells themselves. 
 
 Note. — In this discussion liberal use has been made of the masterly 
 exposition of the subject by Prof. E. B. Mallory, to whom the author 
 is deeply indebted. 
 
CHAPTER Vi. 
 
 DEPOSITS AND ACCRETIONS UPON THE TEETH. 
 
 By EDWARD C. KIRK, D.D.S., Sc.D., LL.D. 
 
 The factors involved in the composition and mode of produc- 
 tion of deposits and accretions upon the teeth are those which are 
 intimately connected with the chemistry, physiology and pathology 
 of the saliva, the study of which is perhaps one of the most important 
 considerations both in its scientific and practical aspects, that is 
 engaging the attention of the dental profession, for it is through the 
 study of saliva that we hope to ultimately solve some of the most 
 important problems with which we have to deal in dental practice. 
 
 It has been mainly through the study of the saliva that we have 
 arrived at some very definite ideas as to the causation of dental caries, 
 and through the study of saliva we have also learned something of 
 various other diseases to which the teeth and soft tissues of the mouth 
 are subject, and it is through the study of the saliva we learn most 
 about the deposits or accretions that are commonly spoken of as 
 tartar and its mode of formation. After all, there is no phase of 
 dental study that is of more immediate importance to those who are 
 pursuing this course than that concerning the causes which lead to 
 the formation of these deposits upon the teeth. 
 
 As for the word "tartar," some years ago in one of the popular 
 magazines there appeared an article by a physician who stated that 
 the tartar on the teeth was called "tartar" because it consisted of 
 tartrate of lime. An eminent professor of chemistry once said to his 
 class dm-ing a lecture that he never had understood why the sulphate 
 of iron was popularly called copperas. He said he imagined it must 
 have been called copper by the Dutch, because it had no copper in 
 it. By the same mode of reasoning, it is probable that this medical 
 man called these deposits tartar because there is no tartaric acid in 
 them. 
 
 The term tartar was applied by the alchemist Basil Valentine to 
 the deposits called argols in wine casks consisting essentially of potas- 
 sium tartrate, and the acid derived therefrom was called tartaric acid 
 or the acid of tartaros. Paracelsus applied the term much more widely 
 to include earthy deposits from animal fluids such as calculus from the 
 saliva. Tartar consists essentially of calcium phosphate or phosphate 
 of lime and some carbonate of lime and corresponding magnesia salts 
 held together by a binding material that we call mucin, a substance 
 derived from the mucus of the saliva; that and some organic matter 
 
150 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 such as food particles, and the bodies of dead bacteria, make up the 
 bulk of what we call "tartar." 
 
 In order to understand the formation and deposition of tartar we 
 must first know something about the saliva. By saliva we mean that 
 mucoid fluid which we find in our mouths most of the time. It is 
 is not always flowing, but our mouths and our food are lubricated 
 and moistened by it. This saliva is manufactured by three pairs of 
 glandular structures situated in the region of the mouth which pour 
 their secretions into the oral cavity. The secretions of these several 
 pairs of glands, which we speak of as the salivary glands, differ in 
 their composition. Neither do all of these glands pour their secretion 
 into the mouth at the same time, but under different circumstances 
 and in response to different kinds of stimuli, namely, the stimulus of 
 food or the stimulus of the thought of food or the stimulus of pain. 
 
 You are all familiar with the common expression that if we think of 
 this or that kind of food it makes our "mouths water." This is 
 literally true. Under the psychic stimulus of the thought of food, 
 especially of food which is sapid or tasty, the salivary glands are 
 encouraged to pour their secretions into the mouth, but it is interesting 
 to note that different kinds of foods excite the secretion of different 
 glands. For example, the physiological chemist Pavlow, of Petro- 
 grad, found that when a piece of fresh meat was offered to a dog the 
 flow of saliva from the sublingual and submaxillary glands was stimu- 
 lated, but not that from the parotid, which is a large gland situated in 
 front of the ear. 
 
 When dry food, like powdered meat, was offered to the dog, the 
 parotid salivary secretion was stimulated. So under different stimuli 
 we find a response from different glands, and the response seems to 
 stand in very close relationship to the character of the food that exerts 
 the stimulus. This is an important relationship too, because dry 
 foods, for example, need a great deal of moisture for two reasons: 
 
 (1) For converting the food into a bolus so that it may be swallowed; 
 
 (2) for furnishing sufficient water to the food in order to dissolve 
 its soluble elements and to develop its taste. Tasty things stimulate 
 the flow of saliva, and the watery secretion of the parotid gland is 
 necessary in order to dissolve what is soluble in the food in order 
 to bring out its taste. We cannot taste anything unless it is soluble, 
 no more can we smell something unless it gives off a vapor of some 
 sort. So that gratification of the sense of taste is secured by the 
 solvent action of the parotid saliva, mainly, upon the foods that we 
 take into the mouth and gratification of the sense of taste plays an 
 important role in the cycle of activities that are related to normal 
 bodily nutrition. 
 
 Besides the secretion of the salivary glands, the secretion of innumer- 
 able mucous glands that are imbedded throughout the whole oral or 
 buccal mucous membrane, the lining membrane of the mouth, is added 
 to the mixed saliva, and it is the secretion of these mucous glands 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 151 
 
 that gives to the saliva its slimy or slippery quality, owing to the sub- 
 stance mucin contained therein. 
 
 Mucin is a very important constituent of the saliva, among other 
 things it has a very direct bearing upon tartar formation, but its 
 main function seems to be that of a lubricant. Perhaps you all know 
 of the peculiar technic of reptiles when they feed. A boa constrictor 
 for instance, kills its prey, which may be a half -grown pig, and covers 
 it with a slimy coating so as to lubricate this relatively enormous 
 mouthful, and to render its passage into his interior as easy as possible. 
 In a minor degree, the same function is performed by the lubricating 
 exudate of the mucous glands of the mouth upon the bolus of food in 
 the mouth of the human being. 
 
 Beside this important substance, mucin, the saliva contains also a 
 peculiar ferment known as ptyalin, the function of which is to begin the 
 digestion of starchy substances in the mouth. Starch as such is not 
 utilizable as food by the body, therefore the ptyalin acts upon it, con- 
 verting it by degrees into a kind of sugar, maltose. This predigestion 
 of starch, or preparation for intestinal digestion, takes place in the 
 mouth, hence the very great importance of thorough mastication of 
 starches, which is doubtless the main justification for the fad of 
 super-chewing that has spread over the country under the name of 
 Fletcher ism. 
 
 Another constituent of the saliva, though perhaps it is not of very 
 great importance, has been exciting a great deal of comment in the 
 past four or five years; that substance is known as potassium sul- 
 phocyanate, ordinarily spoken of as sulphocyanate. It may be 
 questioned that it is a potassium sulphocyanate, but some kind of 
 sulphocyante is present which is possibly a sodium or ammonium 
 sulphocyanate. It has the peculiar property that when to a small 
 quantity of saliva a drop or two of a test solution of perchloride of 
 iron is added, if the sulphocyanate is present it causes a red or reddish 
 coloration of the saliva. This reaction is rather dramatic, and has 
 caused a great deal of discussion and debate as to its significance 
 which thus far appears to be unimportant. 
 
 Sulphocyanate was at one time supposed to have a very important 
 bearing upon caries causation, or of the prevention of carious action 
 in the mouth, but recently it has been pretty definitely shown that 
 sulphocyanate is an incidental constituent of the saliva, and that it 
 has no significance except as a waste product of nutrition related to 
 some other chemical activities in the body. 
 
 In addition to the constituents mentioned, saliva collected in a 
 receptacle will show certain sediments, solid matter, if it stands for 
 a short time. Just as the scarf-skin, or outer layer of the cuticle, 
 separates from time to time, so does the mucous membrane of the 
 mouth shed its epithelial coating into the saliva, and we find mixed 
 with the saliva these epithelial scales from the buccal mucous mem- 
 brane which when a specimen of saliva is allowed to stand for a time 
 separate as sediment. 
 
152 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 We find also as corpuscular elements, the leukocytes, or white 
 blood corpuscles, which gain their way into the saliva. They have 
 been spoken of as salivary corpuscles, but they are really white blood 
 cells which have undergone certain changes of form. 
 
 As to the further chemistry of the saliva, if we take a measured 
 quantity, and evaporate it to dryness, we find a small residue of solid 
 matter. This residue consists of two kinds of substances, certain 
 mineral salts which we speak of as the inorganic constituents of the 
 saliva, and another kind of solid matter which is organic in character. 
 
 The total solids of saliva vary considerably in amount. It is difficult 
 to say what represents the total quantity of solids in the saliva, but 
 it is extremely small in amount, from about half of 1 per cent, to 
 possibly 1 per cent, of the total saliva. These are only approximate 
 figures, because the composition of the saliva varies constantly, 
 depending upon the time of day when the sample is taken, how closely 
 to a meal, whether after vigoroys prolonged chewing, after drinking 
 large quantities of water, or after abstaining from water for some time. 
 Saliva becomes more concentrated the less water we drink, and it 
 becomes more dilute in accordance with the quantity of water drunk. 
 
 The normal saliva in the ideally healthy individual, who has no 
 caries of the teeth, no deposits upon the teeth and in whom the various 
 functions are properly performed, the individual who is living up to 
 the highest state of physical efficiency, in such a normal human being 
 we can safely say the saliva is colorless, odorless and tasteless. 
 
 If the saliva develops either an odor or a characteristic taste, or a 
 color, something is wrong; it is not a normal, but a pathological saliva; 
 something has gone wrong with the individual; the chemistry of his 
 body is not working properly. 
 
 When studying the physical appearance of a quarter- or a half- 
 ounce of saliva collected in a test-tube, we find that in addition to its 
 limpidity, its clearness or opalescence, a slight slimy quality due to 
 the mucin and the presence of sediment, there is a covering of froth 
 upon the top in which air is entangled. Besides which the saliva 
 contains dissolved within . itself a certain quantity of carbon dioxid. 
 As we give off carbon dioxid from the lungs, so carbon dioxid is present 
 to some extent in the saliva, and it gradually escapes on standing; 
 hence the saliva in the test-tube soon loses its froth,, the sediment 
 settles to the bottom, and we have a column of this clear, odorless, 
 tasteless substance above a layer of whitish sediment. 
 
 Any variation from these general conditions indicates ill health of 
 some sort, or some error in nutrition, and the saliva is so sensitive, 
 chemically, it reflects the variations in composition of the blood stream 
 so accurately that we can utilize it for the study of the nutritional 
 condition of the individual at the time when the specimen is taken. 
 
 It is a familiar fact that physicians have for years been studying 
 the urine and the blood, as means for determining the condition of 
 bodily nutrition, but investigation has brought forth the fact that the 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 153 
 
 saliva is almost as important an index of the condition of nutrition for 
 the time being as either of these other fluids mentioned. 
 
 When the saliva is poured from the glands into the mouth it comes 
 into an entirely new environment, that is to say, as it issues from the 
 gland it is, comparatively speaking, sterile; it is not infected with bac- 
 terial elements, we do not find the bacteria in the saliva as it issues 
 from the glands, but it issues into a cavity that is infected on all 
 surfaces; in fact, it is poured into that portion of the human anatomy 
 which is the portal of entry, for nearly all of the bacterial organisms 
 that enter the body, and the saliva is necessarily subjected to the 
 influence of these microorganisms. 
 
 The organisms that infect the mouth are not only myriad in number, 
 but they are of an infinite variety and they produce different effects 
 upon the saliva. Let us consider a little more closely the nature of 
 that action in general. It is a familiar fact that if a quantity of milk, 
 for example, is exposed to the atmosphere for a sufficient length of 
 time, especially on a reasonably warm day, the milk in the course 
 of time undergoes changes and becomes sour, as we say. First, it 
 develops a sour taste, then becomes curdled, and if it is left to stand 
 still longer the sourness disappears and it becomes putrid, developing 
 a very disagreeable odor, as it undergoes decomposition. Modern 
 bacteriology has settled the nature of these processes. They are 
 processes of decomposition or of tearing apart of the various complex 
 compounds that we find in milk into simpler substances. 
 
 Milk contains sugar, nitrogenous or proteid matter in the form of 
 cheese, or casein, it contains water and fats. Each one of these sub- 
 stances seems to have a selective quality for certain kinds of bacteria, 
 some of which attack the sugar, for example; others will only attack 
 the caseous portion, the curd of the milk; other germs attack the fat. 
 Butter, for example, when it becomes rancid, forms a particular kind 
 of acid, butyric acid, as it is called. As the sugar element in the milk 
 undergoes decomposition, it becomes sour just as the sugar in cider 
 is converted into vinegar, or alcohol, as the case may be, through the 
 agency of bacterial action. 
 
 Upon the same principle these various substances in the saliva, 
 mucin, animal matter and sometimes sugar, which is formed by the 
 action of the ptyalin upon starchy matter in the mouth are decomposed 
 by the activity of certain special kinds of bacteria and produce what 
 are designated in chemistry as typical or characteristic kinds of end- 
 products, for example, acid substances; or they may produce ill- 
 smelling substances, hydrogen or ammonium sulphide due to putre- 
 faction or substances like ptomains or toxins which have a specific 
 poisonous action upon the tissues with which they come in contact. 
 
 Incidentally caries or decay of the teetjh is produced the same way. 
 Thus we see the importance of the study of the saliva in relation to 
 the manner in which it is decomposed through the agency of bacteria. 
 From all this we may also deduce the immense importance of a clean 
 
154 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 mouth, not only as regards the integrity of the teeth and the tissues 
 about the teeth and the mouth itself, but as related to the general 
 health of the individual. The question of a clean mouth is not a matter 
 of sentiment alone, or a matter of aesthetics, but it is fundamentally 
 a question of health. 
 
 Since decomposition of the saliva is brought about through the 
 agency of a large variety of bacterial forms constantly inhabiting the 
 mouth, and since the end-products of this bacterial action are so varied, 
 and in most instances either poisonous, or capable of exerting corrosive 
 action upon the tooth structure, it is evident that the best time to get 
 rid of the conditions which result from these fermentative and putre- 
 factive processes that take place in the mouth, is at the beginning, and 
 that by doing so we can successfully prevent not only diseases of the 
 teeth, but many diseases which affect the entire body. 
 
 In connection with the processes of decomposition through the 
 agency of bacteria, a number of phenomena manifest themselves. 
 In the first place, under certain conditions there is the production of 
 a peculiar kind of deposit upon the teeth which has been spoken of 
 as the bacterial plaque. The bacterial plaque is very important in 
 many ways. In the first place, it represents the first step in the process 
 of that disintegration of tooth structure which we call dental caries or 
 tooth decay. Broadly speaking, we cannot have dental caries excepting 
 through the agency of the bacterial plaque. Viewed simply from a 
 physical point of view, a bacterial plaque is a deposit upon a tooth 
 surface which localizes the process of decay. The function which the 
 bacterial plaque performs in localizing the process of tooth decay at 
 certain points is the factor which determines the principal character- 
 istic of tooth decay, namely, that of cavity formation. 
 
 Let us for a moment examine the nature of this deposit called the 
 bacterial plaque. Recall for the purpose of this argument the fact 
 that the saliva contains first of all mucin in solution. In order to have 
 a solution of mucin in the saliva we must have an alkaline reaction of 
 the saliva, because mucin is not soluble in an acid fluid. If we take a 
 specimen of saliva and add a drop of any kind of acid to it, acetic 
 acid, lactic acid, sulphuric acid, citric acid, etc., we shall immediately 
 see what we call a precipitate which looks as if something in the 
 saliva had been cooked, as in the cooking of the white of an egg. 
 That happens instantly when mucin comes in contact with any acid. 
 
 One of the acids which is most prompt to cause the precipitation 
 of mucin is lactic acid, the acid that is produced when milk sours. 
 Lactic acid is instantly produced in the mouth by the action of cer- 
 tain forms of bacteria upon sugars found in or taken into the mouth. 
 
 Sugars, as we know, are produced in the mouth by the action of the 
 ptyalin of the saliva which converts the starch into sugar. As long 
 as sugar is thus formed certain classes of bacteria act upon it and split 
 it up into lactic acid. These lactic-acid-producing organisms being 
 constantly present, fermentation goes on and lactic acid is produced 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 155 
 
 as long as there is something for the organisms to Uve upon. Just the 
 moment that a point (considering a bacterium as a point) of acid 
 production is set up in the saHva there occurs a precipitation around 
 that point of insoluble mucin, and when the action is started by the 
 lodgement of lactic-acid-producing organisms upon a tooth surface 
 where they may develop and multiply undisturbed in protected loca- 
 tions the process continues until what we call a bacterial plaque is 
 formed. These plaques are localized upon all tooth surfaces that are 
 protected from the friction of food or of the tongue or lips, and in 
 places that are not kept thoroughly polished and clean, especially in 
 the class of mouths that are susceptible to dental caries. 
 
 It will be readily understood that the acid which is manufactured 
 at the point localized by the bacterial plaque is constantly disinte- 
 grating the tooth structure upon which it has formed and breaking it 
 down. Thus we have a deposit produced from the saliva and from 
 conditions existing in the saliva which is the first step in the process 
 that we speak of as dental caries. 
 
 The plaques are not ordinarily visible to the naked eye, but there 
 has been introduced^ what is denominated a "disclosing solution" 
 containing iodin, which renders them visible. By applying tincture 
 of iodin to mucin we secure a color reaction, that is to say, it pro- 
 duces a brownish or reddish-brown tint deeper than that of the iodin, 
 especially if certain of the sugars, maltose, for example, be present. 
 If we paint the tooth with iodin or spray it with a solution of iodin, 
 in the course of time we will find that the iodin has stained certain 
 portions of the tooth to a darker tint than others, owing to the fact 
 that the plaques have taken up the iodin, combined with it and formed 
 a dark brownish stain. The formula of Skinner's disclosing solution 
 is as follows: 
 
 Iodin crystals 50 grs. 
 
 Potassium iodid 15 grs. 
 
 Zinc iodid 15 grs. 
 
 Glycerin ... 4 dr. 
 
 Water ' 4 dr. — M. 
 
 As an adjuvant to the disclosing solution, however, another step or 
 stage has been suggested by H. C. Ferris, and that is, the spraying of 
 the surface, after it has been treated with the iodin solution, with a 
 boiled starch solution. It should be remembered, however, that starch 
 and iodin, no matter how they are put together, produce a very dense 
 blue color, and unless one is careful in making this test, the starch may 
 apparently disclose plaques where they do not exist. Hence the 
 tooth should be rinsed thoroughly before the application of the second 
 member of the disclosing solution is made in order to remove excess of 
 iodin. As a matter of fact, a plaque is disclosed with sufficient clear- 
 
 ' F. H. Skinner, Dental Cosmos/ 1912, p. 43. 
 
156 DEPOSITS AND A CCRETIONS UPON THE TEETH 
 
 ness by the use of the ordinary official tincture of iodin, 7 per cent., 
 without subsequent appHcation of starch solution. 
 
 There may be other sources of plaque formation, but the explana- 
 tion given indicates the general principle which accounts for these 
 soft, slimy, fairly adhesive deposits upon the teeth, which can be 
 readily rubbed off by the application of fine pumice on an orange- 
 wood stick, if the rubbing and polishing is thoroughly and carefully 
 done. It does not require the instrumentation that we speak of as 
 "scaling'^ to remove deposits of this class. 
 
 In the precipitation of mucin by lactic acid we have the general 
 principle involved in practically all of the deposits of that character. 
 These may be localized or there may be a general precipitation of 
 mucin upon the teeth, carrying with it particles of food or debris of 
 various sorts, which, if not removed, condenses, grows harder, more 
 tenacious and more difficult to remove, though when first deposited 
 it is very soft in character. 
 
 We come now to a consideration of an entirely different class of 
 deposits which are of the true tartar type, namely, the mineral deposits 
 upon the teeth. The formation of tartar is a most complicated process 
 and constitutes one of the puzzles of the chemistry of the mouth. What 
 we do know about it is this : Chemical analysis of these hard deposits 
 called tartar shows them to consist mainly of calcium phosphate, 
 some calcium carbonate, the bodies of dead bacteria, debris of food, 
 food particles, all bound together by mucin. 
 
 An English investigator, Mr. Rainey, about fifty years ago, under- 
 took a study of the mode of formation of shells of various sorts, and 
 he was led into some experimentation with reference to the changes 
 that take place in certain kinds of earthy precipitates like carbonate 
 of lime under varying conditions, as for example, when these earthy 
 substances were precipitated in a solution which contained a material 
 like gelatin, gum arable or egg albumen, or what is termed in chem- 
 istry, colloidal substances. He found that the carbonate of lime 
 was precipitated from a watery solution in a more or less crystalline 
 character, but if the smallest quantity of glue, albumin, gelatin or 
 other glue-like substance, was added to the water in which the pre- 
 cipitation took place the deposit instead of being of a crystalline 
 character was made up of little spherical bodies that were more or 
 less translucent. The precipitate formed very slowly and this investi- 
 gator found that these minute globular masses side by side tended to 
 increase in size by additions to their exterior, this increase in size 
 continuing until two of these bodies would come together and coa- 
 lesce; then another one would grow up to this mass and they would 
 coalesce, so that gradually it assumed the appearance of a mass of 
 marbles glued together or, of a mulberry mass. 
 
 This investigation led others to continue the observations and 
 finally it was shown that the process of precipitation and molecular 
 coalescence is at the bottom of a number of very important processes 
 
DEPOSITS' AND ACCRETIONS UPON THE TEETH 157 
 
 not only in the human body, but in the mode of growth of the shells of 
 mollusks and the pearl formation in the oyster, for example. On 
 further investigation it was found that the pathological conditions 
 that involve stone-like concretions in the kidney or the bladder, con- 
 cretions of a calcareous character that are found sometimes in the 
 ear and various parts of the body, or in old abscesses that have under- 
 gone repair, all arose after the same principle of coalescence of the 
 precipitate of an earthy salt in combination or in contact with a 
 colloidal or glue-like basis which acted as a binding material. 
 
 Precipitations of the earthy salts, phosphates and carbonates, that 
 were held in solution in the saliva, when they take place in the human 
 mouth, combine with the glue-like substance in the saliva which we 
 have spoken of as mucin, and are bound together by the mucin to 
 form the mass called tartar which deposits itself upon the teeth. 
 Tartar varies in a great many ways; it varies in the rapidity with 
 which it forms, it varies in the position in which it is deposited, and 
 above all it varies in its density, the tenacity with which it adheres 
 to the tooth surface and its toughness. 
 
 Fig. 92. — Specimens of parotid tartar; actual size. 
 
 Certain classes of tartar undergo very rapid formation and enor- 
 mous development. Masses of tartar weighing as much as from two 
 hundred and fifty to three hundred grains are reported. It seems 
 incredible that any human being could tolerate in his mouth a mass 
 of tartar larger than a pigeon's egg attached to the buccal surface of 
 the molar teeth, yet such instances are by no means infrequent. Tar- 
 tar which is formed rapidly and in large masses is usually relatively soft 
 and friable and can be readily removed by proper instrumentation. 
 
 Every dentist has had patients with the idea in their minds that 
 tartar was protective to the teeth and for that reason they objected 
 to having it removed. It is true to a great extent that teeth upon 
 which that kind of tartar is deposited rarely decay, not because the 
 tartar is protective, but because conditions that cause the deposition 
 of the tartar are precisely the opposite of those that favor caries of 
 
158 
 
 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 the teeth. When such enormous accumulations are removed from the 
 teeth the patients are often surprised that the teeth do not come out 
 with the removal of the deposit. 
 
 Fig. 93. — Sublingual tartar on a 
 lower incisor. 
 
 Fig. 94. — Sublingual tartar on a 
 lower canine. 
 
 This kind of tartar will form upon artificial dentures just as readily 
 as upon the surfaces of the natural teeth, and it is usuallv found at 
 
 Fig. 95. — Partial denture clasped to first and second molars, which have been lost by 
 deposition of parotid tartar. 
 
 positions opposite the orifices of the ducts of the salivary glands. 
 For the same reason we find these enormous masses ordinarily upon 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 159 
 
 the buccal surfaces of the molars and upon the lingual surfaces of 
 the lower teeth occupying positions almost opposite the openings of 
 the salivary ducts (see Fig. 95). 
 
 The question of why this is so is the chemical problem that we 
 are confronting. This is what we know: that calcium phosphate as it 
 exists in tartar is not the same kind of calcium phosphate that exists 
 in solution in the saliva; that is to say, after it reaches the mouth 
 it undergoes some chemical change, the nature of which may be illus- 
 trated as follows: One of the popular drinks advertised at the soda 
 fountains is "Acid Phosphate." Calcium phosphate or lime phos- 
 phate, chemically speaking, is a term applied to a group of compounds 
 of which there are two distinct kinds. One contains more lime in 
 proportion to the phosphoric acid than does the other. The one which 
 contains less lime in proportion to the phosphoric acid is designated 
 as acid phosphate, which is soluble in water, and has acid properties; 
 whereas the other phosphate which is designated as basic phosphate 
 contains a larger proportion of lime and is insoluble in water. 
 
 If we add to the acid phosphate a little more lime, we convert it 
 into basic phosphate; and because of its relative insolubility it would 
 fall out of solution as a sediment or precipitate. A similar process 
 occurs in the deposition of this phosphate as tartar in the mouth. 
 It is in a state of acid combination in the saliva. Possibly it is the 
 content of carbonic acid in the saliva which holds the phosphate in 
 solution, and when the carbonic acid escapes from the saliva, the 
 phosphate, having nothing to hold it in solution, falls down as a 
 precipitate. 
 
 Mucin acts as a glue-like binding material to the small earthy 
 particles of phosphate and fastens them together and when the pro- 
 portion of mucin to the calcium phosphate is in certain ratio the mass 
 may be so dense and adhesive that it is almost impossible to cut it 
 with a steel instrument or scrape it from the tooth surface. 
 
 The escape of carbonic acid is one of the means by which we think 
 the earthy materials of the saliva are precipitated. If we take any 
 alkaline substance into the mouth, thereby adding free alkali to the 
 saliva, we are likely to cause a precipitation of the lime salts. 
 
 There is always a certain amount of ammonia, produced by the 
 chemistry of nutrition, that issues from the lungs with the expired air, 
 and if there is enough ammonia produced in a given case to impart a 
 definite free alkalinity to the saliva, then precipitation of the lime 
 salts takes place or ammonia may be produced in the mouth by putre- 
 faction, decomposition of animal substances causing tartar formation 
 in unclean mouths. 
 
 There is another suggested mode of tartar formation. Dr. H. H. 
 Burchard found that when fermentation is going on in the mouth 
 with production of lactic acid in small quantities the mucin is precipi- 
 tated and the coagulated mass of mucin tends to gather within itself 
 these earthy salts, just as a net drawn through a stream would gather 
 
160 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 up fish; this mass is deposited upon the teeth, and condenses more 
 and more, forming tartar. 
 
 Tartar has been thus produced artificially out of the mouth, by 
 taking saliva rich in calcium salts and adding small quantities of 
 dilute lactic acid, causing precipitation when a hard material of a 
 dark greenish shade is produced, physically similar to the deposits 
 that we find upon the teeth. 
 
 One of the most interesting examples of tartar formation is that 
 observed upon the teeth of the natives of Indo-China and the Malay 
 Archipelago. They are habituated to the chewing of the betel nut. 
 This use of the betel nut as a masticatory is very prevalent throughout 
 Indo-China and the Malay Archipelago. 
 
 Habitual chewing of the betel nut, in the course of a short time, 
 causes the teeth to become stained to a very dark reddish brown of 
 about the color of the exterior of a chestnut, and enormous deposits 
 of tartar quickly aggregate, so that the teeth become distorted in 
 appearance and position and are very quickly lost from their sockets. 
 It is not infrequent that young people not over twenty-five years 
 of age are rendered completely toothless by the habit of betel-nut- 
 chewing. 
 
 The shavings of betel nut are wrapped up in pieces of the leaf of a 
 certain kind of plant called Penang pepper, along with some aromatic 
 spices such as catechu or cloves, or cardamom seed, according to the 
 taste of the betel-nut-chewer, to give it an aromatic flavor. Then 
 about the quantity of half a small spoonful of lime, made by burning 
 oyster shells, is sprinkled all over this mass to develop the flavor. 
 This morsel, rolled up in the green pepper leaf, is very carefully tucked 
 away in the cheek. It causes a free flow of saliva tinged with a red 
 color. The addition of the lime, which develops the flavor, is what 
 causes the trouble. The acid or soluble phosphate of lime in the saliva 
 upon the addition of this extra lime, is converted into the insoluble 
 form of phosphate and precipitated on the teeth (Figs. 96, 97 and 98). 
 
 The foregoing is an example of the formation of tartar due to change 
 in the chemical composition of the lime salts of the saliva from a 
 soluble form into an insoluble form. 
 
 The hardness of the tartar depends upon the amount of its lime 
 constituent as related to the mucin constituent. The hardest forma- 
 tions of tartar contain more of the glue-like or mucinous element than 
 do the more friable and easily broken-down forms. The hardest 
 tartar formed is found just under the gum margin. The large masses 
 that are attached to the free surfaces of the teeth opposite the ducts 
 of the glands are usually soft and easily removed regardless of size, 
 but the rings of tartar underneath the gum margin, the hard scales 
 of tartar, are the most difficult of removal. It is this kind of tartar 
 that contains the largest proportion of organic binding material, 
 because the deposit of tartar at that point sets up an irritation of the 
 gum tissue and causes the weeping out from the gum tissue of the 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 161 
 
 albuminous, serous portion of the blood which combines with this 
 deposit and forms a very hard, tenacious mass. 
 
 Fig. 96. — Lower incisor almost completely 
 encrusted with betel tartar. 
 
 Fig. 97. — Lower canine covered with 
 betel tartar. 
 
 Fig. 98.— Lower incisors lost from deposit of betel tartar. As they gradually loosened 
 trom the encroachment of the tartar they were bound together with fine brass wire by a 
 native dentist, to give them firmness by mutual support 
 11 
 
162 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 Farther down upon the roots of the teeth we frequently find deposits 
 of another form of tartar, which is probably not salivary in origin. 
 It is spoken of as serumal tartar and is derived from the serum of the 
 blood. From a chemical standpoint it is practically a formation of 
 the same character but it originates differently. So far as we know, 
 this serumal tartar which is situated deep down upon the roots of the 
 teeth and not connected with saliva in its origin, is the result of some 
 primary inflammatory conditions upon the tooth root. It is not neces- 
 sary to go into the causes of such preceding inflammatory conditions 
 which, instead of breaking out as abscesses, have healed spontaneously 
 by what we call the process of resolution, by which is meant that the 
 bacteria which set up the inflammation have died. They have been 
 killed by the resisting forces of the body itself and the inflammatory 
 process has stopped, and the tissues have undergone repair, but the 
 dead bacteria and the broken-down tissue constituting pus has grad- 
 ually become dehydrated, and there is left a cheesy mass which later 
 on has become saturated with lime salts derived from the blood 
 stream itself. These lime salts combine with this cheesy mass result- 
 ing in a tartar-like formation in which the cheesy mass of colloidal 
 organic matter takes the place of the mucin in saliva as the binding 
 material. 
 
 Tartar formed in that way is a mechanical irritant to the surrounding 
 tissues, making them subject to subsequent infections. The tartar 
 acts as a foreign body in the tissue setting up irritation, infection fol- 
 lows and the process is repeated with continued growth of tartar, or 
 the abscess may break at the gum margin and a pyorrheal pocket 
 may thus be formed. The pus pockets in pyorrhea may be formed 
 from the root to the gum margin or from the gum margin rootward. 
 
 Two other phases of this subject are of importance : one is the color 
 of the tartar, the other is the solubility of the tartar. Tartar we find 
 to be of different colors. The tartar which forms rapidly is soft and 
 friable, salivary in origin and more nearly colorless than any of the 
 other varieties. It is nearer in chemical composition to a simple 
 precipitation of phosphate of lime. But when it forms slowly and 
 under the margin of the gum we usually find it highly colored. It 
 must always be remembered that tartar precipitated around the necks 
 of the teeth is a mechanical irritant to the soft tissues of the gum 
 margin. This irritation predisposes to bacterial infection, which leads 
 to an inflammatory process and, as the inflammation proceeds, more 
 or less blood weeps out from the irritated tissue in contact with the 
 tartar. The tartar is then colored by what we call the hemoglobin 
 or the coloring matter of the red blood corpuscles. In other words, 
 the color of the darker varieties of tartar is derived from the coloring 
 matter of the blood which undergoes a variety of changes in color 
 when it is subjected to the processes that lead to its decomposition. 
 
 It is a familiar fact that a black eye, or any black-and-blue pigmen- 
 tation of the skin surface due to a bruise is at first red, then grows 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 163 
 
 a little darker because the coloring matter from the blood has wept 
 out into the surrounding tissues; then it undergoes chemical decompo- 
 sition, with a variety of color changes, until it becomes very dark. 
 In the same way when blood oozes out from the gum margin and 
 comes in contact with the tartar this coloring matter is absorbed by 
 the tartar, becomes part of its binding material and undergoes color 
 changes which are quite analogous to those observed in a bruise, 
 that is, from a reddish or brown tint through a variety of color changes 
 down through brown and blue to a final grayish or greenish, almost 
 black, appearance. 
 
 Tartar may be pigmented from other causes. It may be pigmented 
 through the activities of certain bacteria that are color-producing, or 
 it may be pigmented by the character of the food or other material 
 that is taken into the mouth as in the case of the betel-nut-chewer, 
 or as in the case of tobacco-chewers or smokers. 
 
 The solubility of tartar is an important consideration from a prac- 
 tical point of view. We have had to depend thus far almost altogether 
 upon mechanical instrumentation for the- removal of these deposits, 
 for the reason that we have had no proper solvent for this material, 
 something that will disintegrate it without endangering the texture of 
 the teeth. The enamel of the teeth is composed of the same mineral 
 ingredients as tartar, namely, calcium phosphate and a little carbonate. 
 Therefore, generally speaking, a solvent of tartar will necessarily also 
 be a solvent of enamel, and it is a very difficult proposition to apply 
 a solvent to the tartar without damaging the teeth. 
 
 There are instances, of course, where the importance of the removal 
 of tartar in certain positions may warrant that risk, if the solvent is 
 applied intelligently and quickly neutralized if it tends to affect the 
 teeth detrimentally. But, broadly speaking, the chemical problem is 
 to find something that will dissolve tartar, but will not dissolve the 
 tooth structure. We would be safer if we could find some chemical 
 solvent that would dissolve, not the calciimi phosphate, but the 
 binding material that holds the calcium phosphate together, i. e., the 
 mucin; but the calcium phosphate is soluble in acid, while the mucin 
 is not. Mucin is soluble in alkali while calcium phosphate is not 
 soluble in alkali, at least in any such strength as can be borne in the 
 mouth. So we are confronting a very delicate problem. It is like 
 trying to use a germicide strong enough to kill bacteria without killing 
 the individual that is infected by them; to find an agent selective in 
 its action, so that it will damage the germ and not damage the host 
 of the germ. 
 
 Certain substances have been used as tartar solvents with a fair 
 degree of success. Lactic acid has the property of dissolving the cal- 
 cium phosphate and of forming soluble salts of calcium phosphate and 
 may be applied as a tartar solvent. It is not a vicious acid in attack- 
 ing the tooth structure, and may be applied to remove the last par- 
 ticles of tartar after the bulk has been removed mechanically by 
 
164 DEPOSITS AND ACCRETIONS UPON THE TEETH 
 
 instrumentation. Solvents should not be used for the removal of 
 the bulk of tartar deposits; they are indicated only for the removal of 
 the last remnants. It should never be forgotten that all the other 
 pieces of tartar are of minor, even negligible importance as compared 
 with the last piece. A man may walk one hundred miles and take 
 many thousands of steps through storm and weather to reach his 
 home, but if he does not take the last step over the doorway, he is 
 not home yet. He may die before he lifts the latch. He has not 
 reached his destination. All his previous steps count for nothing. 
 
 It is quite the same with reference to the removal of deposits. It 
 is the last one that counts, and when that is removed the work is 
 done. The last fragment of tartar sometimes even the most delicate 
 tactile sense may fail to detect, especially if it is situated down toward 
 the end of the root of a tooth, or in a pocket which has been thor- 
 oughly gone over with the instrument, yet one is not sure whether a 
 small particle has not been left. It is in such a place that we may have 
 recourse to the use of a solvent such as lactic acid. 
 
 A word should also be said about the solubility of the bacterial 
 plaque. As this plaque is produced mainly by precipitation of mucin 
 by acids, it is perfectly soluble in alkalies. The alkali that is a natural 
 solvent of mucin precipitated by acid is calcium hydroxide, the solu- 
 tion of which we ordinarily speak of as lime water. A solution of 
 three parts of lime water with one part of hydrogen dioxid has greater 
 efficiency than lime water as a means of removing the bacterial plaque. 
 The lime water renders the mucin soluble so that it can be washed 
 off the teeth, and the hydrogen dioxid disintegrates the plaque, so 
 that this solution has a doubly favorable action. It should be used 
 habitually as a dentifrice by all patients who are known to be con- 
 stitutionally susceptible to caries. 
 
 The sources of the discoloration of tartar to which I referred are 
 also the sources of the discolorations that we find on teeth, especially 
 in children, which are spoken of as green stain or brown stain. There 
 are two sources. The coloring matter of the blood is the proteid sub- 
 stance called hemoglobin. When in solution in the course of a short 
 time, this color undergoes a change, becoming bluish or more purplish 
 in color as the hemoglobin decomposes. In the course of further 
 decomposition it assumes a greenish tint. This color change can be 
 effected much more quickly by adding hydrogen sulphide to the blood. 
 Hydrogen sulphide is produced by decomposition of albuminous 
 matter, as in the decomposition of an egg, which then gives off that 
 peculiar odor of hydrogen sulphide, which is due to the decomposition 
 of the sulphur elements in the albumin, and it is the hydrogen sulphide 
 arising from decomposition of the albuminous or proteid elements of 
 the blood acting on the hemoglobin that changes its color to a dirty 
 greenish tint. 
 
 In cases of irritation of the gum margin, a little of the coloring 
 matter of the blood weeps out, chemical changes go on through the 
 
DEPOSITS AND ACCRETIONS UPON THE TEETH 165 
 
 agency of mouth bacteria, the albuminous portion of the saliva and 
 the blood putrefies. Hydrogen sulphide is given off, the sulphur 
 compounds unite with the coloring matter of the blood and produce 
 the green or greenish-brown stain observed on children's teeth and 
 the teeth of those having irritated and bleeding gums in uncleanly 
 mouths. The chemical make-up of the pigment of that stain is the 
 decomposition product called sulphomethemoglobin. The children's 
 teeth upon which it is observed are not properly kept clean. They 
 have a history of lack of practical acquaintance with the toothbrush 
 and the technic of the ordinary dental toilet. 
 
 Another of these green stains is in all probability due to pigmenta- 
 tions of the normal covering of the enamel of the young tooth, which 
 we speak of as Nasmyth's membrane, b}' certain color-producing or 
 chromogenic bacteria bringing about that characteristic color. 
 
 By treating the young tooth with very dilute acids w^e can isolate 
 Nasmyth's membrane and examine it under the microscope, when we 
 find it permeated with what looks like the result of bacterial activity. 
 
 Both these types of green stain upon the tooth surface are readily 
 removable by the application of iodin, and the subsequent use of polish- 
 ing powders or pumice applied on an orange-wood stick. Iodin is not 
 only an antiseptic, but also a bleaching agent. That sounds very 
 peculiar, because it stains of itself, but we can stain the surface struc- 
 ture of a tooth to a deep tint with iodin and simply let it alone, and 
 when the patient returns the next day that tooth wdll be much lighter 
 in color, due to the bleaching action of the iodin. We need never be 
 afraid of permanently tinting a tooth with iodin, unless w^e apply it 
 with a steel instrument, when iodid of iron is formed and a permanent 
 stain will be produced. Iodin itself nlay be used with perfect freedom 
 upon tooth surfaces free from metallic fillings for the reason that it is 
 ultimately a bleaching agent. 
 
CHAPTER VII. 
 PYORRHEA ALVEOLARIS 
 
 By ARTHUR H. MERRITT, D.D.S. 
 
 Definition and History. — Pyorrhea alveolaris is a disease affecting the 
 teeth and their investing tissues. It may be defined as a progressive 
 resorption of the alveolar process and pericementum with a coincident 
 shrinkage and recession of the gums, accompanied by increasing loosen- 
 ing of the teeth. It is a disease as old as civilization and may be older. 
 There is abundant evidence that it existed among the early Egyptians, 
 Greeks, Etruscans, Phoenicians, Romans and Chinese. Frequent men- 
 tion is made in their literature of " loose teeth," " bleeding gums," etc., 
 with their discharge of "corruption." Some attempt at treatment w^as 
 made, usually in the form of absurd mouth washes, despite the fact 
 that it was generally regarded as incurable. In this country about 
 1845, John M. Riggs of Hartford, Conn., was the first to publicly call 
 attention to the disease and to assert that it was a curable disease, 
 and that by proper surgical treatment 90 per cent, of all cases could be 
 cured. He achieved a considerable reputation in his generation and 
 was quoted at home and abroad as an authority on the subject. As a 
 result, the disease came to be known as "Riggs' Disease" though this 
 name was not given to it by Riggs himself. Prior to this it had been 
 referred to as loose tooth, spongy gums, scurvy, etc. In 1877 F. H. 
 Rehwinkel gave to it the name of pyorrhea alveolaris, in a paper which 
 he read before the American Dental Association. This name, which 
 was not original with Rehwinkel, having been borrowed by him from 
 European writers, has never been wholly acceptable, having been 
 severely criticised since its introduction. It means, literally, a flow of 
 pus from the alveolus, and is therefore descriptive of one phase only 
 in its pathology. Many attempts have since been made to give it a 
 more appropriate name, but without complete success; it still remains 
 the name by which it is most generally known. For that reason it is 
 used here, notwithstanding the fact that the name of periodontoclasia, 
 given to it by the American Academy of Periodontology, is more in 
 harmony with its pathology in its various manifestations. 
 
 Pathology .^ — Pyorrhea alveolaris is a disease which begins, as a rule, 
 at the gingival border, and progresses slowly toward the apex of the 
 root, resulting in a complete destruction of the alveolar process and 
 pericementum with eventual loss of the teeth unless arrested by treat- 
 ment. Some of the phenomenon attending its progress are gingival 
 inflammation, solution of continuity in the floor of the gingival crevice, 
 
PATHOLOGY 167 
 
 absorption of the alveolar process, pocket formation, suppurative 
 infection, sensitiveness to thermal changes, separation, elongation and 
 loosening of teeth. Of these, the first to manifest itself is gingival 
 inflammation induced by various causes, the most common of which is 
 uncleanliness of the mouth. Irritation of the gingiva from any cause, 
 if long enough continued, results in inflammation which in time may be 
 conveyed through the gingival group of pericemental fibers to the 
 pericementum, eventually causing a break in the floor of the gingival 
 crevice. Coincident with this break, the cementum, pericementum 
 and alveolar process are exposed to the destructive forces of irritation 
 and infection. A phenomenon known as halisteresis is set up in the 
 alveolar process, by which it is slowly absorbed. The rapidity with 
 which these changes occur will depend upon several factors — the thick- 
 ness of the bone, the resistance of the patient," the cleanliness or unclean- 
 liness of the mouth, etc. As a rule its progress is slow, often many 
 years elapsing between the initial gingival irritation and final loss of 
 the teeth. 
 
 Pyorrhea alveolaris manifests itself in a succession of sjonptoms. 
 Usually beginning as a mild gingival irritation which may exist for 
 years without further changes, it finally involves the subjacent tissues, 
 slowly destroying the pericemental attachment at the gingivo-enamel 
 junction, absorbing the alveolar crest and slowly advancing toward the 
 apex of the root, destroying the alveolar process and pericementmn 
 as it progresses. This may occur symmetrically aroimd the root, or, 
 as more often happens, along one side only. The destruction of the 
 alveolar process and pericementum is followed by shrinkage and reces- 
 sion of the gums, though this recession never keeps pace with the bone 
 resorption. The result is the formation of a pocket, bounded at one 
 point by the extreme limits of bone necrosis, and at the other by the 
 margin of the gum. The depth of this pocket will depend upon the 
 amount of bone loss and gum recession. Laterally they are bounded 
 on the one hand by the surrounding vascular tissues and on the other 
 by the cementum with its investment of necrotic pericementum and 
 calculary deposit. Into these pockets, even in their earliest beginnings, 
 the bacterial flora of the mouth finds its way. These organisms are 
 secondary invaders only, having no direct etiological relationship to 
 the disease. Comparative studies of the bacterial flora of these 
 pockets show that they do not differ qualitatively from that of the 
 normal mouth. There is, however, great quantitative difference, this 
 being explained by the fact that these conditions are more favorable 
 to bacterial growth than are those of the healthy mouth. This flora is 
 a mixed infection of great complexity. There is no evidence that any 
 of these organisms sustain a direct causal relationship to the disease. 
 They are, however, responsible for one of its characteristic symptoms of 
 pus discharge. These bacteria may also give rise to secondary infec- 
 tions of a serious nature, in many instances contributing to the ill 
 health and inefficiency of the patient, and not infrequently are the 
 
168 
 
 PYORRHEA ALVEOLARIS 
 
 Figs. 
 
 -1. iuo. ad and 100. — Panoramic radiographic view of a normal denture, to show espe- 
 cially the height of the bony alveolar septi between the teeth, for comparison with other 
 radiographs in which destruction of the bone has occurred. 
 
 Figs. 101 and 102. — ^Panoramic radiographic view of the upper and lower jaw in a 
 case of pyorrhea of long standing. Note the amount of bone that has been destroyed 
 by the progress of the disease. 
 
PLATE VIII 
 
 Fig. 1 
 
 Fig. 2 
 
 Fig. 3 
 
 Fig. 4 
 
 Fig. 5 
 
 Fig. 6 
 
 Cases of Gingivitis and Incipient Pyorrhea. 
 
 Note defective contact points, loss of septal gingiva and recession of gums; also aijscess 
 due to pyorrhea in Fig. 5. All caused by irritation from food impaction. 
 
PREVENTION 169 
 
 indirect cause of death. About one thing there can be no doubt, 
 namely, their potentiality for evil is an inherent quality, dependent 
 only for its exercise upon the virulence of the organisms and the 
 resistance of the patient. 
 
 Etiology. — Pyorrhea alveolaris has a variety of causes, most of which 
 have their origin within the mouth. They have one characteristic 
 which is common to them all in that they are irritative in their nature. 
 These causes may be divided into two classes^those which begin at 
 the gingiva and by slow progression involve the entire supporting 
 tissues of the teeth, and secondly those which affect primarily the peri- 
 cementum and alveolar process. Of these the more obvious, and also 
 the more common, are those begining at the gingival margin of the gimis. 
 Anything which irritates the gingiva must be regarded as a potential 
 cause of pyorrhea. Uncleanliness of the mouth, food impaction as a 
 result of defective contact points, overhanging edges of fillings, ill- 
 fitting crowns, bridges, etc., are all causes of gingival irritation. Of 
 these the most common and potentially the most dangerous, is unclean- 
 liness of the mouth. 
 
 The second form of irritation, that which affects primarily the deeper 
 periodontal tissues, is traumatic occlusion. This may be defined as a 
 lack of harmony between the inclined planes of opposing teeth when 
 brought into occlusion in the act of mastication, as a result of which 
 the teeth are driven outside their normal limits of motion, and subjected 
 to a lateral strain, which if long enough continued, causes definite 
 changes in the pericementum and alveolar process with coincident 
 loosening of the teeth. This may exist in teeth with normal occlusion 
 in the usual meaning of the word, that is, straight teeth, and is a very 
 common cause of pyorrhea; it and bad hygiene being the chief causes. 
 
 It is also possible that under certain conditions heredity, diet, con- 
 stitutional diatheses, etc., may predispose to pyorrhea, or may unfavor- 
 ably influence prognosis. These conditions, however, are not common 
 as shown by the fact that most cases yield promptly to local treatment 
 when properly employed. 
 
 Prevention. — There are probably no diseases of a chronic nature 
 occurring in the mouth more easily prevented than is pyorrhea alveo- 
 laris, or none where prevention is of more value. Its treatment in 
 advanced cases is always difficult, and the prognosis often doubtful. 
 All such cases begin as a simple lesion, which with all its unfortunate 
 consequences might have been prevented had proper care been observed. 
 As stated, this lesion usually, if not always, begins at the gingiva, caused 
 by some irritation of this organ, the most common of which is uncleanli- 
 ness of the mouth as expressed in food accumulations, tartar, debris, 
 bacteria, filth, etc. 
 
 If a careful examination be made of the free gingivae, it will be found 
 that they project themselves above the alveolar crests often to the 
 extent of several millimeters. Between the free gingiva and the 
 cervical enamel is the gingival crevice, bounded at the cemento-enamel 
 
170 PYORRHEA ALVEOLARIS 
 
 junction by the attachment of the gingival group of pericemental fibers. 
 In health the free gingivae terminate in a thin edge which hugs the 
 cervical enamel in such a way as to protect this pericemental attach- 
 ment against injury. If, as a result of irritation, this knife-like edge, 
 so admirably adapted to its purpose, becomes inflamed, its protective 
 property is more or less seriously impaired. It no longer permits food 
 to glide over it without injury in the act of mastication, but a certain 
 portion of it is forced into the gingival crevice, thereby adding to 
 the already existing inflammation. Wherever inflammation of the 
 gingivae exists, the quantity of the serum normally secreted into the 
 gingival crevice is increased, and if it contains calcoglobulin, serumal 
 calculus may be deposited. This deposit, so often found in the gingival 
 crevice, is not the cause, but the efi^ect of gingival irritation, though it 
 may in its turn act as an irritant. The importance, therefore, of pro- 
 tecting the gingivae against irritation must be obvious. They stand 
 as protective barriers to the subjacent tissues of the teeth, including 
 that most vulnerable point, the pericemental attachment. Their 
 preservation in health is essential to the proper function of the teeth; 
 to conserve and protect them against injury is of the first importance. 
 This is the work to which the dental hygienist is called, and there 
 is none more worth while in the whole field of dental practice. It is a 
 service of far more value to the patient than any restorative measures 
 which may be employed to replace these teeth after they have been 
 lost, just as preventive treatment is always of more value than curative. 
 She has within her power the prevention of two of the most common 
 diseases which afflict mankind — dental caries and pyorrhea alveolaris, 
 diseases so nearly universal as to affect all races and all ages. The first 
 of these can be reduced to a minimum by oral hygiene; the second can 
 be almost completely prevented by the same measures. To accomplish 
 this the gingivae must be maintained in health; nothing must be allowed 
 to irritate them. Each gingiva should be carefully examined and the 
 slightest abnormality in form or color noted, and its cause sought out 
 and removed. This cause will be found to be something which irri- 
 tates — usually something acting from without, such as an unclean 
 mouth, defective contact points, which permit of food impaction, 
 overhanging edges of fillings, crowns, bridges, etc. Certain chemical 
 poisons acting from within, of which mercury and potassium iodide 
 are examples, may also irritate and inflame the gingivae, as may cer- 
 tain poisons which result from nutritional disturbances, but these are 
 uncommon and almost negligible factors. The really important thing 
 is that they be protected against external irritants, which is best 
 accomplished by thorough and painstaking cleansing of the teeth. 
 This involves more than a perfunctory polishing of the enamel surfaces. 
 Every gingival crevice should be explored and its contents removed. 
 In those cases in which solution of continuity has taken place in the 
 floor of the gingival crevice, and the subjacent tissues have become 
 involved in disease, treatment by the dentist is required. The more 
 
SUMMARY 171 
 
 valuable service of prevention falls within the pro\'ince of the dental 
 hygienist. 
 
 Treatment — Pyorrhea alveolaris is a curable disease, though it may 
 reach an incurable stage if long enough neglected. Its treatment 
 belongs exclusively to the dentist. The dental hygienist, however, 
 should be familiar with the approved method of treatment and able 
 to express an intelligent opinion on the subject. She can be of great 
 assistance to the dentist in helping to maintain a high degree of oral 
 cleanliness, always a prerequisite to the best results. Its treatment 
 is essentially surgical, a fact first announced by Riggs more than three 
 quarters of a century ago. This consists in the complete removal from 
 the denuded cementum of all calcareous deposits, including also the 
 necrotic pericementum. In some instances, curettage of the affected 
 alveolar process may be necessary. When traumatic occlusion is 
 present, as is often the case, this must be corrected by judicious grind- 
 ing of the occlusal surfaces of such teeth. Treatment in advanced 
 cases requires an exacting and painstaking technic. The absolute 
 necessity of cleansing the involved cementum of all foreign and necrotic 
 material, makes the operation an exceedingly difficult one. Failure 
 in this respect means unsatisfactory results, which explains why it is 
 that so many are unsuccessful, and explains also why so many are 
 pessimistic regarding its prognosis and treatment. 
 
 When, however, proper methods of treatment have been employed, 
 the most gratifying results are achieved. Health is reestablished in 
 the involved tissues, the teeth tighten in their sockets, the gums resume 
 their normal color and become firm about the teeth, in some instances 
 reattaching themselves to the roots, thereby completely obliterating 
 the pockets. This, however, does not occur about non-vital teeth 
 that have become septic, nor about vital teeth upon which poor root 
 surgery has been practised. 
 
 Postoperative treatment requires the maintenance of a high degree 
 of mouth cleanliness. The patient must be instructed in correct 
 habits of tooth brushing and provided with proper tooth brushes, 
 dentifrices, waxed silk tape, etc. This should be supplemented by 
 periodic cleansing by the dentist or hygienist, the frequency of which 
 will depend large;ly upon the efficiency of the care given by the patient; 
 three to six months' intervals will be sufiicient in most cases. Mouth 
 washes, drugs, vaccines, etc., have very little place in the prevention 
 and treatment of pyorrhea. Dependence must be placed upon normal 
 occlusion and mouth hygiene, not forgetting that anything which 
 irritates the gingiva is a potential cause of disease in these tissues. 
 
 Summary. — If now a summary be made of present-day knowledge 
 regarding pyorrhea and its treatment, certain facts stand out clearly. 
 Pyorrhea is not, as it is believed by some to be, a disease of modern 
 life, but is as old as civilization itself. It expresses itself in many 
 forms, beginning, as a rule, at the gingival margin, and by extension, 
 
172 PYORRHEA ALVEOLARIS 
 
 slowly involving all of the supporting tissues of the teeth, and thereby 
 causing their final loss. 
 
 Its causes are usually found within the mouth itself, and may be 
 anything which irritates the gingivae, the most common of which is 
 uncleanliness of the mouth. It is a disease which in most instances 
 can be prevented when proper care is observed by both patient and 
 dentist. To achieve this it is essential that the gingivae be kept from 
 irritation. Oral hygiene in its broadest sense is the best means to that 
 end. Pyorrhea is a curable disease if taken in time. Its treatment 
 is surgical and depends for success upon the thoroughness and skill 
 with which the operation is performed. As a rule, its treatment is 
 not painful. Mouth washes and drugs have no place in treatment. 
 This applies to the hypodermic use of vaccines, emetin, etc. Reliance 
 must always be placed upon oral hygiene in both the prevention and 
 treatment of pyorrhea alveolaris. 
 
CHAPTER VIII. 
 DENTAL CARIES. 
 
 By EDWARD C. KIRK, Sc.D., D.D.S., LL.D. 
 
 Dental caries, or as it is commonly designated, tooth decay, is a dis- 
 ease which, in so far as humanity is concerned, is practically universal 
 in its distribution. It affects all civilized peoples, some uncivilized 
 tribes and, under certain conditions, even some of the lower animals. 
 No disorder that afflicts the human race is more common, as it has been 
 shown by abundant statistics that from 85 to 95 per cent, of civilized 
 human beings are more or less the victims of dental caries or have 
 suffered from its ravages at some period of their lives. Dental caries 
 is essentially a disease of childhood and adolescence, the developing 
 individual appears to be peculiarly susceptible to its invasion, whereas 
 when adult life is reached the tendency to tooth decay is noticeably 
 lessened as in the majority of cases when the individual has reached 
 full maturity the progress of tooth decay appears to be markedly 
 arrested. So manifest are these differences in the activity of dental 
 caries as related to the age and development of the individual that the 
 phenomena of susceptibility and immunity to the disorder are accepted 
 as characteristic of its activity. As further evidence of the same 
 characteristic a small proportion of individuals are found to be quite 
 free from any evidences of tooth decay, never having suffered from its 
 invasion at any time or in any degree, these are regarded as being 
 naturally immune. 
 
 The period of childhood and adolescence being the period of greatest 
 susceptibility to dental caries makes its relationship to the health 
 of children of school age one of vital importance, not only from the 
 hygienic point of view but upon educational and economic grounds 
 as well. 
 
 Comparatively recent studies of the question furnish abundant evi- 
 dence of the fact that the prevalence of dental caries among children 
 of school age is the fruitful primary cause of mental backwardness, 
 interrupted brain development, nervous disorders, errors of vision 
 and of hearing, bodily malnutrition and a host of evils which not 
 only retard or interfere with the educational process but impair to a 
 serious degree the physical and mental efficiency of these developing 
 citizens of the future generation. Hence the importance of not 
 only a proper understanding of the nature of this important disorder 
 but a clear appreciation of its gravity as a menace to human health 
 and efficiency. 
 
174 
 
 DENTAL CARIES 
 
 For purposes of anatomical description a tooth is viewed as having 
 a crown (corona) which is all that part of the tooth exposed beyond 
 the gum, and a root (radix) or radicular portion which is all that part 
 of the tooth embedded in the bony socket or alveolus beneath the 
 gum. The portion at the gum line between the crown and the root 
 is designated as the neck (cervix) of the tooth. 
 
 Fig. 103. — Vertical section of a tooth in situ (15 diameters), c is placed in the pulp 
 cavity, opposite the cervix or neck of the tooth; the part above is the crown, that 
 below is the root (fang) ; 1, enamel with radial and concentric markings; 2, dentin with 
 tubules and incermental lines; 3, cementum, or crusta petrosa, with bone corpuscles; 
 4, pericemental membrane; 5, bone of mandible. 
 
 Dental caries is' a destructive process affecting the hard dental 
 tissues; these are three in number: (1) The enamel which is the 
 hard outer protective covering of the underlying dentin of the tooth 
 crown and (2) the cementum or crusta petrosa covering the dentin 
 
DENTAL CARIES 
 
 175 
 
 of the root; and (3) the dentin which forms the principal body of the 
 tooth. Within the body of the dentin in the central cavity of the 
 tooth is located the tooth pulp, a soft, highly sensitive and vascular 
 organ, commonly but incorrectly called the "nerve." From a group 
 of specialized cells upon the surface of the dental pulp there radiate 
 through the dentin innumerable fibers of living matter, richly endowed 
 with sensation, which with their lateral processes ramify throughcmt 
 the dentin structure. These are termed the dentinal fibers or fibrilke, 
 and it is through their agency that we perceive the painful impres- 
 sions arising from irritation of the dentin by cutting, by heat, cold, 
 sweets, etc. 
 
 Fig. 104. 
 
 -Longitudinal section of^dentin, showing distribution of dentinal fibers and 
 stratum granulosum. (Miller.) 
 
 Dental caries always has its inception upon the external or exposed 
 surface of a tooth; it never arises from within the tooth. For a long 
 period it was held by many students of the subject that tooth decay 
 was an inflammatory process similar in certain respects to necrosis of 
 bone, and those who accepted that view also held that caries originated 
 within the tooth structure and gradually progressed outwardly toward 
 the free enamel surface. This theory was maintained by some until 
 quite recent times, but its fallaciousness was finally completely demon- 
 strated by the researches of the late Prof. Dr. W. D. Miller, published 
 about 1880, which finally gave to the world the true explanation of the 
 process of tooth decay. 
 
 Briefly stated, Miller, as the result of a long and exhaustive experi- 
 mental study of the subject, found that the destruction of the hard 
 structures of the tooth by dental caries was accomplished through 
 
176 DENTAL CARIES 
 
 the agency of a certain class of microorganisms which had the charac- 
 teristic function of fermenting certain of the sugars and converting 
 these sugars into lactic acid, which acid in its turn attacked the solid 
 structure wherever it came into contact with it, dissolving out its 
 mineral matter which caused the structure to disintegrate, forming 
 a cavity which gradually enlarged until it eventually included the 
 entire crown; indeed, if unchecked, the whole tooth may in this manner 
 become disintegrated and lost. 
 
 A tooth, however, is not wholly composed of mineral matter soluble 
 in lactic acid. If we immerse a tooth for a sufficient length of time 
 in an acid, for example, dilute nitric or hydrochloric acid, it will be 
 found to have lost all of its enamel covering and the remaining dentin 
 and cement structures while still possessing the general conformation 
 of the original tooth will be found to have lost their hardness to such 
 a degree that the structure may then be easily cut with a knife into 
 chips or slices like a piece of cartilage which the structure now closely 
 resembles. We say of a tooth so treated that it has been decalcified, 
 that is to say, the calcium or lime salts which gave to the tooth 
 structure its characteristic hardness have been removed or dissolved 
 out by the acid and what remains is an organic substance or animal 
 tissue called the organic matrix or basis substance of the dentin and 
 cementum. 
 
 The relative proportions of calcium salts or mineral matter and 
 organic matrix or tooth cartilage in the dentin and enamel structures 
 are shown in the following analyses: 
 
 Dentin (Von Bibra). 
 
 Tooth cartilage 27.61 \^ 
 
 ■p^^ 40 ) '^^^^^^ matter 
 
 Calcium phosphate and fluoride 66.72) 
 
 Calcium carbonate 3.36 I t 
 
 Magnesium phosphate ^ ^S Inorganic matter 
 
 Other salts 0.83] 
 
 Enamel (Von Bibra). 
 
 Cartilage 3.39\r> • ^^ 
 
 Fat . . : (J 20 / °'^''''''= ""^"^^ 
 
 Calcium phosphate and fluoride 89.82 
 
 Calcium carbonate 4.37 
 
 Magnesium phosphate 1 . 34 
 
 Other salts ■ 0.20 
 
 Inorganic matter 
 
 Enamel (Kuehn). Dentin (Kuehn). 
 
 CaO 53.75 CaO ^ 53.42 
 
 MgO 0.84 MgO 2.41 
 
 P2O6 -37.21 P2O6 39.46 
 
 Fl 0.29 Fl 0.25 
 
 Organic matter and H2O . 8.48 Organic matter and H2O . 32.10 
 
 Miller showed that the first phase of the carious process was a 
 dissolving out of the mineral substances or decalcification of the tooth 
 structure by lactic acid produced by the ferment action of certain 
 microorganisms on sugars. He further showed that when decalcifica- 
 
DENTAL CARIES 111 
 
 tion had taken place, infection of the exposed organic matrix of the 
 tooth structure by a different type or class of microorganisms occurred, 
 these latter known as proteolytic bacteria, had the power to liquefy 
 and bring about putrefaction of the organic matrix and to destroy 
 it in the same manner that a dead animal body is destroyed and disin- 
 tegrated by putrefactive changes. These two phases of the carious 
 process are essentially the same in principle, dependent upon the 
 vital activities of microorganisms of two distinct groups, each having 
 the power to decompose certain compounds which enter into the 
 formation of tooth structure and to produce by their action certain 
 characteristic physical phenomena and certain end or decomposition 
 products equally characteristic. Thus in a cavity of decay the presence 
 of acid may be easily demonstrated by bringing into contact with the 
 decaying mass a strip of blue litmus paper which will at once turn 
 red where the decaying mass touches it. The characteristic odor of 
 putrefaction is readily recognizable, indeed, offensively so, in the 
 breath of those suffering actively from tooth decay. This odor of 
 putrefaction arises in large part from the decomposition of the organic 
 matter of the dentin matrix through the agency of the proteolytic 
 bacteria. 
 
 The human mouth is not only the portal of entry for many disease- 
 producing microorganisms, but because many of these microscopic 
 vegetable organisms thrive, flourish and rapidly reproduce themselves 
 under the conditions of moisture, temperature and food supply that 
 they find in the mouth cavity many species continue to inhabit the 
 mouth and those which are possessed of disease-producing charac- 
 teristics become the agency of infection by which a variety of bodily 
 diseases are produced. An unclean mouth is therefore a constant 
 menace to bodily health as well as the ordinary source of tooth decay. 
 Fig. 105 shows a mixed infection of various bacteria from a tooth 
 surface. 
 
 But though a great variety and an almost infinite number of micro- 
 organisms are constant inhabitants of the mouth, and though the 
 lactic-acid-producing bacteria which cause tooth decay are found in 
 nearly all human mouths, it is well known that many teeth do not 
 decay, and even where the decay process is active not all surfaces of 
 the teeth are equally vulnerable to the process of decay. 
 
 It has long been noticed that certain locations or areas upon the 
 tooth surfaces are more liable to be the seat of decay than are certain 
 other surface areas. In general, it may be said that those surfaces of 
 the teeth that are subjected to the cleansing action of friction by the 
 tongue, the lining mucous membrane of the lips and cheek surfaces 
 or teeth surfaces which are kept free of bacterial invasion by the 
 friction of rough or fibrous food materials, are less liable to decay; 
 whereas, those surfaces of the teeth not subject to the self-cleansing 
 action of the foregoing causes are most likely to be the seat of decay, 
 as shown in Fig. 106. 
 12 
 
17S 
 
 DENTAL CARIES 
 
 Locations where food particles infected by mouth bacteria can find 
 an undisturbed lodgement, such as the natural pits and depressions in 
 
 Fig. 105. — Mixed infection from tooth surface. (Williams.) 
 
 Fig. 106. — Caries localized above the "contact point" on the approximating surfaces of 
 contiguous molar teeth. (Williams.) 
 
 the masticating surfaces of the molars and premolars, the sulci between 
 the cusps, and especially the approximating surfaces of the teeth which 
 by their mutual relations of contact afford protected areas for the 
 
DENTAL CARIES 
 
 179 
 
 lodgement of food particles and its undisturbed decomposition by 
 lactic-acid-producing bacteria are areas which in a susceptible individ- 
 ual are the selected locations of the carious process (Figs. 107 and 108). 
 
 Fig. 107.- 
 
 -Beginning caries in sulci and enamel defects of morsal surface of a molar, 
 also showing transparent zone of Tomes. (Miller.) 
 
 Fig. 108. — Beginning caries on approximal surface. (Miller.) 
 
 The determination of the location of tooth decay is in large degree 
 a result of the form of the individual tooth and of the relations of the 
 teeth to each other in the dental arches. 
 
180 DENTAL CARIES 
 
 The structure of the tooth itself, that is to say, whether it be hard 
 and dense or whether it be relatively soft and imperfectly calcified, 
 does not in the slightest degree influence the liability of teeth to decay 
 or otherwise. Any tooth will decay in a mouth where the conditions 
 causing decay are active and no tooth will decay whatever its structure 
 may be in a mouth where the conditions causing decay are not active. 
 Or, as stated by the late Prof. G. V. Black, "decay of the teeth is a 
 factor of the environment of the teeth. It is not due to the structure 
 of the teeth in so far as their structure is characterized by density, 
 hardness, softness, etc. These factors may influence the rate of decay 
 but they do not determine the liability to decay." 
 
 When starchy food particles, sugars or any form of fermentable 
 carbohydrate food material is lodged in contact with a protected area 
 of tooth surface it becomes subject to the action of lactic-acid-produc- 
 ing microorganisms and undergoes fermentation resulting in its decom- 
 position with the production of lactic acid. A familiar example of this 
 process is the souring of milk when left exposed for a time to the air 
 at a warm room temperature. Milk contains a considerable quantity 
 of a characteristic sugar called sugar of milk and chemically desig- 
 nated lactose, having the formula C6H12O6. Bacteria from the air 
 fall into the milk and set up a fermentation of the milk sugar decom- 
 posing it or splitting it into lactic acid which when it accumulates 
 sufficiently, gives the milk an acid reaction and a sour taste. The 
 acid thus formed breaks up the combination of the casein with the 
 base with which it was in chemical union and precipitates the casein 
 as a curd so that the milk becomes thickened and when separated from 
 its watery whey, this curd is the material from which cheese is made. 
 
 The casein or cheesy portion of the milk will also undergo putre- 
 factive changes through the agency of proteolytic and other forms of 
 bacteria which have the property of decomposing this type of organic 
 matter so that the process of fermentation and subsequent putre- 
 faction of milk is, in principle at least, quite analogous to the process 
 of tooth decay. 
 
 The conversion of sugar into lactic acid by the fermentative agency 
 of bacteria is represented by a chemical formula as follows : 
 
 Glucose. Lactic acid. 
 
 C6H12O6 + the enzyme of B. acidi lactici = 2C3H6O3 
 
 that is to say, a molecule of the monosaccharid glucose is, under the 
 action of the enzyme of the B. acidi lactici, split up into two molecules 
 of lactic acid. Starches, cane sugar and the more complex carbohy- 
 drates must first undergo changes in the mouth into the simpler forms 
 like glucose before they can be split into lactic acid and these pre- 
 liminary changes are brought about by other enzymes, and particu- 
 larly by ptyalin, the characteristic ferment of the saliva which pos- 
 sesses marked amylolytic properties or the power to convert starches 
 into sugars that may be subsequently split into lactic acid by the 
 agency of the proper bacterial enzyme. 
 
DENTAL CARIES 181 
 
 These chemical alterations as the result of the action of digestive 
 ferments and bacterial enzymes upon the debris of food substances 
 are constantly going on in mouths which are not kept clean and free 
 from food remnants either by habitual use of the usual tooth-cleansing 
 devices of brush and dentifices, unless we may exclude those excep- 
 tional cases which are naturally self-cleansing and therefore immune. 
 It is this constant fermentative activity that initiates dental caries 
 wherever on a localized area of tooth structure it is permitted to con- 
 tinue undisturbed. 
 
 It should be borne in mind that dental caries is a distinctly localized 
 process in its inception. The disease may appear in one or many 
 places in the same mouth, at the same time, but it is localized in the 
 sense that it does not attack all surfaces of the teeth simultaneously, 
 nor with equal impartiality. Many who in the beginning of their 
 study of the pathology of dental caries have clearly grasped the fact 
 that lactic acid is the agent which initiates the disorder by dissolving 
 out the lime salts of a localized area of tooth structure, and that the 
 first stage of cavity formation is thus explained, not infrequently 
 jump to the erroneous conclusion that lactic acid alone is the cause 
 of tooth decay and cavity formation. 
 
 As a matter of fact, a generally acid saliva, even if the acidity be 
 due to lactic acid, will not give rise to tooth decay. An acid saliva is 
 destructive of tooth structure by bringing about a general decalcifica- 
 tion of the teeth which is manifested more intensely in certain locations 
 than in others, but this type of destruction of tooth structure is not 
 dental caries but what is called chemical erosion of the teeth, a disorder 
 not necessarily dependent upon bacterial activity, as it may be pro- 
 duced by any free acid formed in the mouth, exuded into the mouth, 
 or taken into the mouth. 
 
 Dental caries is a characteristic disease with a well-marked and 
 definite group of symptoms and within certain limits it has a known 
 causation, which is the localized destruction of the hard tissues of the 
 tooth by the solvent action of lactic acid generated at the point of 
 decay by the agency of bacteria acting upon carbohydrate foodstuff. 
 
 While localization of the decay process is to a large degree deter- 
 mined by the forms of the teeth and their relations to each other, 
 as already explained, there is another and somewhat complicated 
 method by which fixation of lactic-acid-producing bacteria to a tooth 
 surface is brought about, a method which because of its importance 
 in relation to oral hygiene as well as to the causation of decay should 
 be clearly understood and that is the localization of decay-producing 
 bacteria upon the tooth surfaces by the precipitation of mucic acid 
 from the mucin of the saliva by the lactic acid set free by the activity 
 of the bacteria themselves. 
 
 The precipitation of the mucic acid upon tooth surfaces is dis- 
 cussed in detail in the chapter on Deposits Upon the Teeth, as it is 
 a result of bacterial activity responsible to a considerable degree 
 
1S2 DENTAL CARIES 
 
 for the formation of those adhesive deposits upon the teeth to which 
 the general designation of tartar is applied; it is important to recapitu- 
 late its main features here in so far as they are concerned in localizing 
 the process of dental caries. 
 
 In mouths where caries is in active progress the saliva is ordinarily 
 rich in mucin which when present in appreciable quantities, is recog- 
 nizable by the glairy or ropy, adhesive character of the fluid. The 
 saliva has the property of viscosity; it has a certain cohesiveness and 
 may be drawn out into threads of greater or less length according to 
 the quantity of mucin that it holds in solution. Such saliva is nearly 
 neutral or faintly alkaline in reaction. If to a small quantity of such 
 a saliva gathered in a test-tube a drop of lactic acid, or, indeed, any 
 acid is added, there will be formed at the point of contact an opales- 
 cent precipitate which is the mucic acid set free from the alkaline base 
 with which it was previously in chemical combination in the saliva 
 as mucin. 
 
 If the test-tube is allowed to stand undisturbed for some minutes 
 the precipitate will settle to the bottom of the glass. The precipitated 
 mucic acid is adhesive and insoluble except in an alkaline or saline 
 solution. If now we apply these data to our study of what takes 
 place in the mouth, we shall find that they throw much light upon 
 the mode of localization of the carious process. 
 
 Assuming that in a susceptible mouth the saliva is rich in mucin 
 held in solution by the alkaline salts of the saliva and that the mouth 
 contains carbohydrate food material in the form of soluble sugars, 
 produced by the amylolytic action of the salivary ferment ptyalin 
 upon starchy food debris, then, in such a mouth infected by lactic- 
 acid-producing bacteria, one or more of these organisms falling upon 
 a tooth and temporarily lodged in some irregularity of the enamel 
 surface, immediately sets up a fermentative action in the soluble 
 sugar of its salivary environment setting free lactic acid in the imme- 
 diate vicinity of the bacterium. The liberated acid at once decomposes 
 the dissolved mucin of the saliva throwing down the adhesive mucic 
 acid in contact with the body of the microorganism, cementing it, as it 
 were, to its position upon the enamel surface. Multiplication of the 
 bacteria proceeds rapidly and the process of acid production and mucic 
 acid precipitation proceeds in harmony with the bacterial multiplica- 
 tion. The mass of bacteria thus organized and cemented to the tooth 
 surface constitutes what is known as a bacterial plaque, the essential 
 factor in the localization of tooth decay and the most important charac- 
 teristic in the causation of the disease. (See Fig. 109.) 
 
 The bacterial plaque presents a variety of physical appearances 
 under the microscope. It may exist as a small glistening semitrans- 
 parent mass occupying only a small spot of the enamel surface or it 
 may present the appearance of a film extending over a considerable 
 area, in fact, over all surfaces of the tooth not subject to friction by 
 food or the tongue and buccal mucous surfaces. The microorganisms 
 
DEl^TAL CARIES 
 
 m 
 
 found in the plaque are never a pure culture of lactic-acid producers 
 but while these are presumably always present, the organisms are 
 usually those constituting the mixed infection usually found in the 
 unclean mouth (Fig. 105). 
 
 It has been shown that tooth decay is brought about in the first 
 place by the decalcifying action of lactic acid produced by the ferment 
 action of bacteria upon carbohydrate food debris. This is, however, 
 a general statement of fact that requires somewhat closer analysis in 
 order that the exact nature of the process may be more clearly under- 
 stood. All carbohydrate material is not directly fermentable into 
 lactic acid, thus cane sugar and starches, two important nutritive 
 substances, must undergo certain chemical changes in the mouth 
 by which they are converted into simple forms of sugar, the mono- 
 
 FiG. 109. — Bacterial plaque, detached from enamel sxirface of the tooth in making the 
 preparation. (Williams.) 
 
 saccharids having the general formula CeHiaOe, before the bacteria of 
 tooth decay can convert them into lactic acid, this preliminary change 
 called hydration or hydrolysis, is brought about in the case of starches 
 by the ferment ptyalin, an enzyme produced by the salivary glands 
 and which is therefore a normal constituent of the saliva. Its func- 
 tion is to prepare the starches and possibly some of the more complex 
 sugars for later assimilation by the cells of the body in the process 
 of nutrition. 
 
 The physiological chemist Claude Bernard showed by experiment 
 that cane sugar as such is not assimilated by the human organism when 
 injected into the veins, but when taken into the mouth is later acted 
 upon by a special amylolytic enzyme called invertase in the intestinal 
 canal and thereby converted into a monosaccharid assimilable sugar 
 suitable for the nutrient purposes of the organism. 
 
184 - DENTAL CARIES 
 
 The typical conversion of starch and of cane sugar respectively into 
 lactic acid may be shown chemically as follows : 
 
 Cane sugar. : 
 
 Cl2H?20ll "l" H2O 
 
 becomes hydrolyzed through the action of invertase to 
 
 Glucose. 
 
 Cl2H240l2 = 2C6Hl206 
 
 which through the enzyme action of B. acidi lactici is split into 
 
 Lactic acid. 
 4C3H6O3 
 
 and 
 
 Starch. 
 C12H20O10 -\- 2H2O 
 
 becomes hydrolyzed and starch through the action of diastase, or 
 ptyalin, to 
 
 Glucose. 
 C12H24O12 = 2C6H12O6 
 
 which through the enzyme action of B. lactici is likewise split into 
 
 Lactic acid 
 4C3H6O3 
 
 From the foregoing it will be seen that the mother substance from 
 which mouth bacteria produce lactic acid is a simple form of sugar 
 belonging to the monosaccharid group of sugars called the hexoses 
 from their chemical constitution, all having the formula C6H12O6, a 
 compound which readily splits into two molecules of lactic acid having 
 the formula 2C3H6O3. The sugars being soluble substances readily 
 diffuse into or are capable of absorption by the bacterial plaque so 
 that the bacteria thus fixed and localized upon a protected tooth sur- 
 face are nourished by a food supply of soluble sugar directly convert- 
 ible into lactic acid which being produced continually in these localized 
 areas of bacterial fixation exerts its solvent and decalcifying action 
 upon the enamel without interference. 
 
 The manner in which enamel disintegrates under the solvent action 
 of lactic acid is both interesting and important. The enamel covering 
 of a tooth crown is made up of innumerable prismatic rods or prisms 
 irregularly hexagonal in section and densely calcified. These enamel 
 prisms stand endwise to the dentin and pursue a radiating and some- 
 times wavy course to the periphery or free enamel surface. The prisms 
 are bound together by a material of much the same chemical nature 
 as that constituting the prisms themselves, but it differs therefrom 
 in the physical sense that it is more readily soluble in acids. If we 
 take a thinly ground section of enamel and place it on a slide and 
 while examining it under the microscope allow a drop or two of dilute 
 acid to act upon the free edge of the specimen, we will see that the 
 acid dissolves out the interprismatic cementing substance much more 
 rapidly than it affects the structure of the prisms themselves; hence 
 
DENTAL CARIES 
 
 185 
 
 the acid, because of this greater solubility of the interprismatic cement- 
 ing substance, tends to penetrate between the prisms separating them 
 from each other and causing them to fall apart as shown in Fig. 110. 
 It is precisely this effect that we see in the opaque chalky white 
 spots that make their appearance upon susceptible tooth areas and 
 which the intelligent operator recognizes as the beginning of dental 
 decay. The opacity and chalky appearance of these spots is due to 
 the fact that the interprismatic cementing substance that formerly 
 gave the appearance of homogeneity to the enamel structure has been 
 dissolved out leaving air or fluid in its place having a different refrac- 
 tive index than the enamel (Fig. 111). As the process proceeds the 
 area enlarges and the enamel rods having lost the means of mutual 
 support, fall apart and are lost, leaving an open cavity in their former 
 location. 
 
 Fig. 110. — Section of enamel subjected to the action of dilute acid, showing solvent 
 effect on the interprismatic cementing substance and penetration of the acid between 
 the enamel rods. (Williams.) 
 
 The irritative effect of the gradual penetration of acid through the 
 enamel in the process of tooth decay is manifest at a very early stage. 
 Even before an actual cavity has been formed or the acid penetration 
 has reached the junction of the enamel with the dentin, the latter 
 tissue will have manifested its reaction to the irritation by recording 
 certain characteristic changes in its structure. In a section of a tooth 
 attacked by slowly advancing caries there will be noticed in the 
 structure of the dentin lying subjacent to the line of invasion a cone- 
 shaped area between the dentino-enamel border and the pulp cavity 
 with the apex of the cone toward the pulp and the base toward the 
 disintegrating enamel. This cone-shaped area of dentin is more trans- 
 parent than the surrounding dentin structure and from its peculiar 
 transparency has been called the transparent zone of Tomes, from Sir 
 John Tomes, who first described it. Various theories as to the cause 
 of this alteration in the character of the dentin structure have been 
 
1S6 DENTAL CARIES 
 
 advanced, and such authorities as Tomes, Magitot, Miller and Walkhoff 
 regard it as being an overcalcification of the dentin structure as a result 
 of the irritation of the living matter of the dentin. Certain it is that it 
 is the expression of a vital reaction upon the part of the dentin, for it 
 does not occur in dead (i. e., pulpless) teeth and it always does occur 
 from long-continued slight irritation to the dentin from whatever 
 cause. Its main importance in connection with the study of dental 
 caries is that it records indisputably the fact that dental caries in 
 its progress sets up irritation which is felt and recorded by the vital 
 elements of the tooth, even in the earliest stages of the disease and 
 before the integrity of the enamel surface has as yet been seriously 
 disturbed (see Fig. 107, a). 
 
 CARIES OF DENTIN. 
 
 When the enamel has been penetrated and a cavity has thus been 
 formed, invasion of the dentin rapidly follows. Caries of the dentin 
 differs from caries of enamel in two important particulars arising out 
 of the differences in structure and composition of the dentin as com- 
 pared with that of the enamel. 
 
 The dentin contains a relatively larger amount of organic matter than 
 the enamel; the earthy salts entering into the composition of the dentin 
 are deposited in a cartilaginous substance having the general form of 
 the tooth and known as the organic matrix or basis substance of the 
 dentin. The organic matrix which in the formed tooth is fully calcified 
 is everywhere permeated by fibrils of sensitive living matter encased 
 in tubules which radiate from the surface of the pulp through the 
 dentin structure. It is these fibrils of living matter that endow the 
 dentin with sensation and which give rise to pain when the dentin 
 is cut as in the preparation of a cavity of decay preparatory to the 
 filling operation or when sweets, acids or other irritating substances 
 are brought into contact with the walls of a carious cavity. 
 
 The distribution of living matter in the dentin may be seen from 
 Fig. 104, which is reproduced from a photograph of a section of the 
 dentin cut in the plane of the long axis of the tubules in which the 
 fibrillse run. 
 
 As soon as loss of enamel exposes the ends of the dentinal fibrillse 
 invasion of the tubules by the bacteria of decay promptly takes 
 place and the tendency of the carious process is to follow the direction 
 of the tubules toward the dental pulp. 
 
 Within the dentinal tubule the bacteria of decay elaborate their 
 characteristic lactic acid which dissolves the sides of the tubule enlarg- 
 ing its diameter, the increased space being promptly packed with 
 organisms reproduced from the parent pioneers of the invasion the 
 dissolution of the tubular walls continuing until the area of decalcifica- 
 tion involves adjacent tubules which have been undergoing a similar 
 process of enlargement until coalescence of a number of tubes takes 
 
CARIES OF DENTIN 
 
 187 
 
 place (Figs. 112 and 113). Coincidently, as decalcification proceeds 
 and exposure of the organic nnatrix occurs, that structure is attacked by 
 
 Fig. 111. — Section of tooth, showing localized solution of interprismatic cement 
 substance with enamel rods standing, constituting the "opaque spot" of beginning 
 decay. (Miller.) 
 
 Fig. 112. — Longitudinal section of carious dentin, showing enlarged tubules packed with 
 
 bacteria. (Miller.) 
 
 a group of bacteria known as proteolytic organisms which have the 
 property of elaborating an enzyme that brings about liquefaction of 
 
188 
 
 DENTAL CARIES 
 
 the cartilaginous proteid material constituting the organic matrix. 
 Decomposition and putrefaction of the decalcified basis substance of 
 
 Fig. 113. — Cross-section of carious dentin, showing enlarged tubules. (Miller.) 
 
 Fig. 114. — Liquefaction foci in carious dentin. (Miller.) 
 
 the dentin thus takes place with the formation of so-called liquefac- 
 tion foci in the dentin which liquefaction foci by their extension and 
 coalescence ultimately produce what is commonly known as a cavity 
 
CARIES OF DENTIN 189 
 
 of tooth decay, the process continuing until the pulp is reached or, 
 if the process is not arrested, until the tooth is destroyed (Fig. 114). 
 
 It has already been noted that invasion of the dentin by the bac- 
 teria of caries is by way of the dentinal tubules which these organisms, 
 generally speaking, follow toward the pulp and various considerations 
 seem to indicate that this mode of invasion of the dentin is largely 
 determined by the fact that the source of food upon which the organ- 
 isms feed is found in the substance of the dentinal fibril or the juices 
 of the fibril itself. 
 
 It has been clearly demonstrated by the researches of Miller, 
 already referred to and confirmed by other able and trustworthy 
 investigators, that dental caries can be, and is, due to decomposition 
 of carbohydrate food particles in unclean mouths, fro;m which we have 
 drawn the conclusion that tooth decay is a filth disease, that if proper 
 care as to oral hygiene is instituted and maintained dental caries may 
 be eradicated; in short, we have come to regard it as an accepted 
 fact that "clean teeth will not decay.'' This conclusion is probably 
 too hastily drawn and without full consideration of all the factors 
 involved, which tend to limit its general application. 
 
 Experience shows that teeth decay more rapidly in early than in 
 adult life, that the teeth of some individuals decay more rapidly than 
 others, that the teeth of some never decay, that many who give scrupu- 
 lous attention to their teeth are extremely susceptible to decay of the 
 teeth, while others whose mouths never receive any attention appear 
 to be immune. 
 
 The problems of susceptibility and immunity to dental caries are 
 as yet unsolved; there are, however, many indications that give color 
 to the hypothesis that there are certain nutritional factors that have 
 much to do with the susceptibility to dental caries or with immunity 
 therefrom. Those who live upon an excessive carbohydrate diet are, 
 as a rule, found to be more prone to carious invasion than those whose 
 diet is largely of a proteid character. Probably under an excessive 
 carbohydrate diet the percentage of sugar in the blood, normally about 
 0.001, is increased and if the salivary fluids and the juices of the dentinal 
 fibrils derived from the blood reflect this increase in carbohydrate 
 above the physiological normal would readily invite the invasion of 
 decay-producing bacteria. In 1881 Milles and Underwood expressed 
 the opinion that the bacteria feed upon the juices of the dentinal 
 fibrillse in dental caries as follows : " The organic fibrils upon which the 
 organisms feed and in which they multiply are the scene of the manu- 
 facture of their characteristic acids, which in turn decalcify the matrix 
 and discolor the whole mass."^ 
 
 If, then, susceptibility to tooth decay is in considerable degree 
 dependent upon a constitutional predisposition, oral hygiene alone and 
 unaided cannot wholly prevent it, although it can undoubtedly greatly 
 
 1 Trans. Seventh International Congress of Medicine, London, 1881. 
 
190 DENTAL CARIES 
 
 diminish its ravages. It is highly probable from our present knowl- 
 edge of the subject that complete control of this universal disorder 
 can never be attained by local measures alone. The fundamentally 
 important question of dietetics, of food habit, must be studied for 
 what light it can throw on the solution of the problem, for even now the 
 evidence is almost overwhelming that the inordinate and increasing 
 habitual use of sweets by civilized children is a custom pernicious 
 alike to the integrity of their dentures and to their general health. 
 
 Until the deeper underlying factors of the causation of dental caries 
 are discovered we must rely upon the means at our command in 
 the principles and art of oral hygiene to protect humanity as best we 
 may from the scourge of dental caries and its consequent damage to 
 health and life. 
 
CHAPTER IX. 
 ODONTALGIA AND NEURALGIA. 
 
 By ARTHUR HOPEWELL-SMITH, Sc.D., L.R.C.P., M.R.C.S., L.D.S. 
 
 Introductory. — The word odontalgia is a pure Greek derivative, 
 meaning literally "tooth pain." It is popularly spoken of as "tooth- 
 ache." But the latter term possesses another and more significant 
 meaning which the popular imagination and experience cannot dis- 
 tinguish from pain in a tooth; it includes also neuralgia, the English 
 form of two Greek words which indicate " nerve pain." It thus happens 
 that odontalgia and neuralgia are frequenth' mistaken for each other. 
 Further, it frequently happens clinically, that both occur simultane- 
 ously, thus rendering the pathological conditions which induce them 
 obscure and difficult to determine. 
 
 It is the purpose of this chapter to set forth in a simple fashion 
 an account of the two chief types of pain associated with the dental 
 organs of man. 
 
 ODONTALGIA. 
 
 Odontalgia is not a disease, but a symptom or sign of a disease or 
 diseases. Neuralgia, similarly, except for the very specific condition 
 called epileptiform neuralgia, is a sjonptom. Pain itself cannot be a 
 morbid state of the body. It is an indicator — a beneficent indicator 
 of a diseased condition of an organ, due to a disturbance of the sensory 
 nervous mechanism of that organ. A tissue or organ devoid of sensory 
 nerves is incapable of feeling pain locally, as exemplified, for instance, 
 in the liver. On the other hand, an organ freely supplied with sense 
 filaments is exceedingly subject to pain, as exemplified in the dental 
 pulp where the nerve fibers are partly sensory and partly sympathetic 
 —that is, distributed to and thus control the blood vascular system. 
 
 It therefore follows that odontalgia is a common, special, important, 
 and distressing symptom of certain diseases of the dental pulp; while 
 neuralgia, generally associated with morbid affections of the nerves 
 which are distributed to the teeth, may and does occur in connection 
 with any sensory nerve of any part of the body remote from or near 
 to the head and neck. 
 
 Definitions.- — The two words odontalgia and neuralgia may thus be 
 defined : odontalgia is pain in or around a tooth or teeth ; neuralgia 
 is pain in the course or the peripheral distribution of a sensory nerve 
 or nerves. 
 
 For the proper comprehension of the meaning of the word "pain" 
 it is necessary to define and note the causes and laws of sensations. 
 
192 ODONTALGIA AND NEURALGIA 
 
 "Pain" can shortly be translated "a disagreeable sensation." It is 
 not easily described, but for present purposes this definition will 
 suffice. 
 
 Definition of Sensatio7i. — A sensation is a means by which a person 
 is made aware of the events occurring in the outside world — the means 
 by which his environment acts upon him. It is the "consciousness 
 of an impression made upon the mind through the medium of a nerve 
 or one of the organs of sense." (Starling.) 
 
 Causes of Sensations. — Sensations are caused by some movement of 
 molecules or masses occurring in the outside world which act upon the 
 sense organs and convert them into nerve impulses which are carried 
 either to the brain or spinal cord. In the case of the former, impulses 
 give rise to some kind of so-called reflex action which may be either 
 conscious or unconscious. If it is conscious, the person becomes aware 
 of a sensation. 
 
 The five senses — touch, taste, smell, sight and hearing — do not 
 complete the number of different sensations experienced by the human 
 body. There are really eight, all told, for to the list can be added the 
 sensations of temperature changes (heat, cold ^nd their variations), 
 the muscular sense, and, finally, pain. 
 
 Laws Governing Sensations. — All sensations are governed by two laws: 
 First, the law of specific irritability, which states that every sensory 
 nerve reacts only to one form of stimulus and gives rise to one form 
 of sensation. In other words, every sensory nerve minds its own 
 business. The second law — the law of proportionality — establishes 
 the fact: "The increase of stimulus which is required to produce 
 distinct increase of sensation always bears the same ratio to the whole 
 stimulus." With regard to the muscular sense the proportion is one 
 in forty, in the tactile or pressure sense one in thirty. 
 
 Pain a Distinct Sense. — Pain is, as has already been observed, an 
 uneasy or disagreeable sensation, due to overexcitation or undue 
 stimulation of a sensory nerve, no matter what the nature of the 
 stimulus. Thus, if the elbow be placed in a dish of iced water the trunk 
 of the ulnar nerve is stimulated, and pain is referred to the third and 
 fourth fingers by virtue of their muscles being supplied by the super- 
 ficial palmar branch of this nerve. If the so-called "crazy-bone" 
 sustains a blow sensations are conducted also to the same digits. 
 
 Pain is a distinct sense. It is not an exaggerated tactile or tempera- 
 ture sensation, but promoted by a distinct set of special nerve fibers, 
 although indistinguishable under the microscope from motor, sensory 
 or sympathetic nerves. It is a well known clinical fact that many 
 patients are insensitive to pain, yet they are able to respond immediately 
 to touch. Many patients in whom the tactile sense is deficient or 
 absent, suffer from an exaltation of the pain sense. Further, certain 
 areas of the skin afford examples of the existence of pain "spots" 
 which are similar to the "heat and cold spots" found, for instance, on 
 the palm of the hand. 
 
ODONTALGIA 193 
 
 In certain regions of the body only one sensation is experienced, by 
 whatever means induced. The cornea is capable of feeling only pain- 
 ful sensations; all kinds of stimulation are converted into the one 
 sensation. The presence of foreign substances on its surface, such as 
 a piece of grit, a stray eyelash, a chemical irritant, induces pain. 
 
 And it is thus with the teeth. 
 
 In normal circumstances teeth do not feel anything. When they 
 are occluded in the ordinary way no impression is recognized by the 
 brain; but when they are brought into contact by a conscious act, the 
 tactile or pressure sense is established and the brain becomes aware of 
 what has taken place. The act of placing a finger on the surface of a 
 tooth sets up weak tactile sensations, and the brain takes cognizance 
 of the fact because it is done consciously. The same argument applies 
 to the exercise of walking, where, ordinarily, tactile impressions on the 
 soles of the feet are not felt unless the act is being accomplished 
 consciously. 
 
 It is therefore obvious that as the dental pulp and the periodontal 
 membrane are abundantly supplied with sensory nerves, and are from 
 this viewpoint special sense organs, unable to differentiate between 
 the several kinds of stimulations, these two tissues, like the cornea, 
 are incapable of interpreting the various kinds of stimulations in any 
 other term than the one of pain. Irritation of the dental tissues, 
 whether it be set up by heat, cold, sweet, sour, bitter or acid substances, 
 electrical, mechanical or bacteriological disturbances, is translated by 
 the dental pulp and periodontal membrane into pain. 
 
 Anatomical and Physiological Considerations. — ^The exact method of 
 conduction of impulses from outside sources to the pulp is still a matter 
 of controversy. The limits of this article do not allow of a discussion 
 of the subject; but it may be stated generally that the enamel of the 
 teeth, being merely an inorganic substance — a secretion which has 
 undergone calcification, transmits and does not generate sensations. 
 It conducts any of the above mentioned stimulations to the dentine 
 beneath. The latter tissue, probably by irritation of the dentinal 
 fibrils, contained in its manifold canals, in its turn transmits impulses 
 to the pulp, and the brain responds through the direct paths of the 
 nervous mechanism of the latter. 
 
 The reaction time in man differs according to the physical condition 
 of the subject of the experiment, the length of the so-called "dilemma," 
 and other circumstances, but may be considered as varying from 0.15 
 to 0.2 second. Generally speaking, it may be said that it is quicker 
 than an ordinary electrical current. 
 
 Varieties of Pain. — Pain varies in character and type. It may be 
 (1) direct or local; (2) indirect or reflex. 
 
 1. The direct form occurs after a local injury, e. g., extraction of a 
 tooth at the place in the mouth where removal of the tooth has been 
 effected. 
 
 2. The indirect form occurs at a distance from the injury or disease, 
 
 13 
 
194 ODONTALGIA AND NEURALGIA 
 
 e. g., some functional disturbances or pathological conditions of the 
 liver set up pain under the left scapula, others in the epigastrium. 
 Some form of reflex action in another organ or organs may -be referred 
 to the teeth; thus, the phenomenon commonly called "setting the 
 teeth on edge" may be produced by reflex sensations from the nerves 
 of hearing, touch or sight. A friend of the writer once told him that 
 his teeth had been set on edge, when in India, by observing children 
 in certain parts of the country sucking sugar cane. Contact with the 
 velvety surface of the skin of a peach, the creaking of a wheel, may also 
 be cited. 
 
 Pain varies in type. It may be sharp or dull, agonizing, lancinating, 
 aching, continuous, intermittent, localized or diffuse. The nature 
 depends on the cause and on the anatomical peculiarities of the tissue 
 affected. 
 
 In making the diagnosis of the cause of pain great attention must 
 be paid to the foregoing types. This is usually an easy matter, but 
 at times extremely difficult on account of complications. 
 
 Causes of Odontalgia.^ — It has been indicated that the two dental 
 tissues in which pain may originate are the pulp and the alveolo- 
 dental periosteum. 
 
 Three varieties may be noted: (a) Local odontalgia; (6) referred 
 odontalgia, and (c) obscure odontalgia. 
 
 (a) Local odontalgia is a symptom of (1) acute or chronic hyperemia 
 and inflammation of the pulp, or (2) acute or chronic hyperemia and 
 inflammation of the periodontal membrane; (6) referred odontalgia 
 is a symptom of any condition which gives rise to irritation of the 
 peripheral branches of the fifth pair of nerves and their connections; 
 (c) obscure odontalgia occurs in teeth without any obvious visible 
 lesion. 
 
 Local Odontalgia.^ — When a warm solution is takenr into the mouth 
 and induces slight odontalgia it indicates that the vessels of the pulp 
 are congested. If the condition remains unrelieved inflammation 
 follows. 
 
 Pain in acute pulpitis is symptomatic of the disease. Its intense 
 character is due to the fact that as a result of the enlargement of the 
 bloodvessels, the exudation of inflammatory cells and products, the 
 inflammation of the nerves themselves, and the increase in the amount 
 of perivascular material taking place in a soft, highly vascular tissue, 
 incapable — owing to its enclosure in dense, unyielding walls of dentine 
 — of expansion, great tension is brought to bear on the already inflamed 
 sensory nerves distributed throughout. 
 
 The phenomenon is somewhat different in the case of the periodontal 
 membrane. It is here modified to some extent by the swelling of the 
 membrane consequent on the inflammatory changes going on within, 
 being compensated by a slight elevation of the tooth in its alveolar 
 socket. 
 
 In the early stages of acute periodontitis pressure on the offending 
 
ODONTALGIA 
 
 195 
 
 tooth brings immediate relief; for blood is pressed out of the enlarged 
 vessels, which thus momentarily return to their normal diameter and 
 capacity. In later stages, however, the walls of the bloodvessels do 
 not regain their elasticity, nor the blood current its equilibrium. They 
 remain, therefore, more or less permanently dilated; hence pressure 
 increases instead of diminishes or abolishes pain. 
 
 It frequently happens that both pulp and periodontal membrane 
 are affected. The types of pain above indicated then become complex 
 and the diagnosis involved. 
 
 The following differences in types of pain in uncomplicated cases 
 will be found useful : 
 
 Differential Diagnosis of Acute Inflammation of: 
 
 The Dental Pulp. 
 
 1. Pain: Sharp, shooting, intermittent, 
 
 throbbing, reflected. 
 
 2. Temperature: (a) Cold may give 
 
 rehef in early stages; (b) heat in- 
 tensifies pain. 
 
 3. Inspection: Tooth normal height. 
 
 4. Palpation: Tooth firm. 
 
 5. Percussion: Negative. 
 
 6. Pressure: Negative- 
 
 7. Cavity: Generally present. 
 
 8. Pain: Increased on assuming recum- 
 
 bent position. 
 
 The Periodontal Membrane. 
 
 1. Dull, gnawing, aching, continuous, 
 
 localized. 
 
 2. (a) Cold generally gives rehef; (b) 
 
 heat does not alter character of 
 pain. 
 
 3. Tooth raised in socket in later stages. 
 
 4. Tooth loose in later stages. 
 
 5. Induces pain. 
 
 6. At first relieves pain; in later stages 
 
 intensifies it. 
 
 7. No ca\aty. 
 
 8. Not increased. 
 
 In view of the fact that odontalgia is the chief sjniptom of acute and 
 chronic pulpitis and periodontitis and their complications, the causes 
 of these conditions are identical with that sjTiiptom. They may be 
 enumerated as follows: 
 
 (A) Acute Pulpitis, Including Hyperemia. — (1) The toxins of caries- 
 producing organisms of dental caries; (2) injury to the dentine; (3) 
 extension of inflammation from the periodontal membrane; (4) cold; 
 (5) rheumatism and allied constitutional disorders; (6) abuse of 
 mercury, taken internally; (7) fillings, inducing thermal conductions. 
 
 (Bi) Acute Local Periodontitis, Including Hyperemia. — I. Septic 
 conditions set up by (i) extension from the septic pulp; (ii) dento- 
 alveolar abscess arising in a neighboring tooth; (iii) "pyorrhea" 
 pocket. II. Traumatic disturbances set up by (i) irritation produced 
 by the presence of tartar, edge of badly-fitting crown or denture; (ii) 
 malocclusion; (iii) improper application of rubber dam clamp; (iv) 
 blow on a tooth; (v) too rapid separation of teeth before filling a cavity; 
 (vi) too rapid movement during regulation; (vii) perforation of dentine 
 of root through the side; (viii) passage of instruments through the apex; 
 and (ix) occasionally, passage of root filling through the apex; III. 
 Chemical causes set up by the use of various drugs. 
 
 (B2) Chronic Local Periodontitis induced by: (i) Septic infection 
 fropa root canal; (ii) Traumatism, such 9,s a blow on a tooth, edge of 
 
196 ODONTALGIA AND NEURALGIA 
 
 tartar, rough edge of filling, carious cavity at gingival margiti retaining 
 food debris, malocclusion, imperfectly contoured filling, and delayed 
 eruption of teeth. 
 
 (B^) General Periodontitis due to gout, diabetes, rheumatism, syphi- 
 litic stomatitis, abuse of mercury, insufficiency of mastication, etc. 
 
 Referred Odontalgia.— The commonest form of referred odontalgia 
 is expressed in the pulp of a tooth which is not in itself the seat of the 
 pain. A maxillary molar may refer its pain to the mandibular molar 
 on the same side; a mandibular third molar may refer its pain to a 
 mandibular premolar. Pressure on the supra-orbital branch of the 
 frontal division of the ophthalmic nei-ve as it emerges from the supra- 
 orbital foramen may induce odontalgia in the maxillary canine of the 
 same side. The pain never crosses the mid-line of the face. 
 
 Fig. 115. — Diagram of a reflex act. The sensory nerves in (T) the tongue and (C) 
 cheek send stimuH to (B) the brain, which transmits them to (P) the dental pulp. Thus 
 exceedingly sweet substances on the tongue will, at times produce odontalgia. 
 
 Obscure Odontalgia. — Odontalgia may occur in teeth unaffected by 
 dental caries. It is then due to one of the following causes: (1) 
 Increased or diminished blood-pressure in the pulp; (2) pulp nodules; 
 (3) altered chemical constituents of the blood; (4) intra-oral electrical 
 impulses; (5) reflex from tongue; (6) lesions of Vth nerve; (7) general 
 neurasthenia and debility. 
 
 The physiological and pathological conditions during which obscure 
 odontalgia may arise as a symptom are associated with: (1) The period 
 of puberty in boys and girls, and during the plethoric habit in men, 
 in menstruation or menopause in women; (2) rheumatism and allied 
 blood diseases; (3) lack or deficiency of lime salts in the blood; (4) slight 
 impulses producing weak voltaic currents generated during operations 
 about the mouth, as the contact of dissimilar metals when the saliva 
 
NEURALGIA 197 
 
 happens to be sufficiently ionized (Fig. 110); (5) on taking very sweet 
 substances into the mouth under certain emotional or nervous cir- 
 cumstances (Fig. 115); (6) inflammation, injury, tumors, and (7) 
 periods of mental depression following overanxiety or overwork. 
 
 In all of these there is no visible pathological lesion of the teeth, 
 excepting under (4), where carious cavities have been filled with gold 
 or amalgam and occupy a large area of the tooth surface. 
 
 Fig. 116. — Diagram of a reflex act. An electrical impulse may set up momentary 
 odontalgia when two dissimilar metals, such as those of the edge of a hand mirror (M) 
 and (F) of metallic filling, meet, and the circuit is completed by (C) the mucous mem- 
 brane of the cheek, the saliva acting as the electrolyte. 
 
 NEURALGIA. 
 
 Definition. — Neuralgia is pain in the course of a sensory nerve, or 
 within its area of distribution. 
 
 Neuralgia is an extremely general symptom of some of the phases 
 of many nervous disturbances occurring in any part of the body. 
 Commonest when affecting the head and neck, and associated chiefly 
 with the trigeminal nerve, this symptom of disease may become the 
 most terrible affliction to which man is subject. It may be regarded 
 as a serious sign, for the accumulated results of long-continued pain 
 may lead to severe mental and constitutional conditions which are very 
 difficult to treat successfully. 
 
 Nature and Type. — ^The character of the pain varies considerably. 
 It is, however, well differentiated from odontalgia. Thus, it may 
 be sudden .and violent with decided remissions and intermissions; it 
 may be recurrent, alternating and periodic; it may be shooting, piercing 
 and penetrating. It generally commences quite suddenly, spasmodi- 
 cally, and without warning, and increases gradually to a climax of 
 intense exacerbation, th^en slowly or rapidly subsides. The attacks 
 may last for minutes, or hours, or days. The writer recalls a case 
 where the most agonizing pain lasted for fifteen minutes at a time, then 
 passed away for a short period, only to return again with increased 
 vehemence. Slight exciting causes may induce neuralgia, such as a 
 sudden noise, like the banging of a door, a draft of air. Pressure on 
 the trunk of the affected nerve may occasion, or relieve, or intensify 
 
198 ODONTALGIA AND NEURALGIA 
 
 the pain. The parts in the neighborhood of the nerve may become 
 affected; muscles may become spasmodically contracted; the skin 
 hyperemic and swollen, and the secretions from the sweat-glands 
 excessive in amount. Skin eruptions, such as herpes of the lip may 
 occur, and the temporomandibular joint become tender, and a kind 
 of trismus produced. 
 
 Causes. — The general and local constitutional disorders of which 
 neuralgia is a s^Tuptom may be difficult to determine. Among them 
 hysteria, mental depression, migraine, neurasthenia, general debility, 
 malaria, anemia, inffuenza, difficult dentition and unerupted teeth in 
 children, may be suspected; while tumors of the brain, injuries to nerve 
 trunks, various forms of neuritis, and tumors of the nerves may also be 
 enumerated. 
 
 Edentulous persons, in whom much atrophy of the alveolar processes 
 of the jaws has occurred as a result of premature loss of the teeth, 
 frequently experience neuralgia through pressure set up by wearing a 
 denture. In this way the mandibular nerve, though unexposed in the 
 mandibular canal, is often affected. 
 
 Varieties. ^ Four true types of neuralgia have been described: 
 (1) Neuralgia Qiiinti Major — the tic douloureux of some authors; (2) 
 Neuralgia Quinti Minor; (3) neuralgia secondary to disease of, or injury 
 to, or pressure upon a cranial nerve, as a tumor of the trunk of the 
 trigeminal, and (4) neuralgia secondary to general disease such as 
 anemia, etc. 
 
 Neuralgia Quinti Major may begin either in the Gasserian ganglion 
 or in the peripheral distribution arising, as Sir Victor Horsley first 
 described, from an ascending neuritis due to chronic osteitis of the 
 sockets of the teeth. 
 
 Neuralgia Quinti Minor is a visceral referred pain due to chronic 
 pulpitis, chronic periodontitis and their complications. It may be 
 explained thus: "When impulses pass up sensory nerves from a 
 tooth which is diseased, they set up a disturbance in that segment of 
 the nervous system to which they are conducted. Any second sensory 
 impulse from another part, e. g., from the surface of the face, which 
 happens to pass into that segment will be profoundly altered in charac- 
 ter, for it no longer falls into a normal but into an actively disturbed 
 segment of the nervous system. The resulting stimulus therefore 
 becomes more exaggerated in character." 
 
 On the face these areas represent the segmental origin of the nerves 
 that give rise to heat, cold and pain. 
 
 This part of the subject has been thoroughly investigated by Valleix 
 and Prof. Henry Head, who has mapped out on the skin certain well- 
 defined regions which are under the influence of the individual teeth. 
 
 The accompanying illustrations (Figs. 117 to 124) demonstrate 
 graphically these areas, and need not be fully described. The reader 
 is referred to the writer's "Dental Anatomy and Physiology," or 
 the original article in Brain, Part III, 1894. 
 
NEURALGIA 
 
 199 
 
 Bordering upon the line between physiological and pathological 
 pain, if one may use such a term, is an unusual ali'ection or disturbance, 
 
 f 
 
 Fig. 117. — The frontonasal area (maxil- 
 lary incisors) . In this and the succeeding 
 figures, the "maximum spots" of intensity 
 of pain are indicated by a round white dot. 
 
 Fig. 118. — The nasolabial area. (Maxil- 
 lary canine and first premolar.) 
 
 ¥ 
 
 Fig. 119. — The temporal area, 
 gecond premolar.) 
 
 (Maxillary 
 
 i 
 
 Fig. 120. — The maxillary area. 
 (Maxillary second premolar or first 
 molar) . 
 
 not a disease, of the trigeminal nerve, similar perhaps in origin to a 
 hemicrania when due to hyperemia of the vessels of the cerebrum. 
 
200 
 
 ODONTALGIA AND NEURALGIA 
 
 Hughlings Jackson says one form is due to digestive derangements. 
 Here changes in the feeding customs of an individual — digestive changes 
 or altered constructive metabolism due to a newly acquired fasting or 
 
 Fig. 121. — The mandibular area. (Maxillary 
 second and third molars.) 
 
 Fig. 122. — The mental area. 
 (Mandibular incisors, canine and 
 first premolar.) 
 
 Fig. 123. — The hyoid area. (Mandibular 
 second premolar, and first and second 
 molars.) 
 
 Fig. 124. — The superior laryngeal area. 
 (Mandibular third molar.) 
 
NEURALGIA 201 
 
 semi-fasting habit — may and do often set up odontalgia and neuralgia, 
 very diflficult of diagnosis by dentist and physician. Located and 
 limited to one side of the face, it is always the same side or alternate, 
 sides of the face which are afi'ected, as if one of the pairs of the Vth 
 nerve was more susceptible for some reason to these changes, and as if 
 the brain was content in indicating the presence of a deep-seated 
 disturbance only by one, and not by two routes. It spreads over a 
 large area and does not involve the mastoid region or concha of the 
 ear. It is increased on deep pressure outside of the jaw, over the root 
 of the tongue. 
 
 The pain is heavy, dull, sporitaneous, persistent, deeply planted, 
 apparently in the body of the mandible, maxilla or cheek. The soft 
 palate, tongue and tonsils are unaffected. It may last for a haK hour 
 or less and then disappear. No maximum spots of intensity are 
 noticed. Digital pressure increases it; hot and cold objects have no 
 effect, though cold may at times relieve it. Pressure as from a soft 
 substance, like a cushion or pillow, produces an exacerbation. 
 
 The teeth are very sensitive. A cold finger gently passed over their 
 crowns increases the pain; pressure and percussion do not. Occlusion 
 of the opposing teeth does not. 
 
 Excluding migraine, the cause of the trouble appears to be anemia 
 or metabolic disturbances of the sjTiipathetic nervous system, due to 
 slight temporary gastric disturbance set up by malnutrition or influenza. 
 
 A full, easily digested meal will usually relieve the pain, while the 
 exhibition of drugs, such as acetophenetidin, in 5-grain doses, is also 
 indicated. Tonics and general attention to health should also be 
 advised. 
 
 Treatment. — ^Little need be here said about the therapeutic measures 
 which are available for the relief of odontalgia and neuralgia, for it is 
 obvious that the treatment of the symptom and not the cause of the 
 symptom is unscientific and incorrect. Odontalgia can be, and is, 
 treated with much success by a skilful dentist, but neuralgic conditions 
 should be treated by common sense cooperation with the physician 
 and surgeon. It is therefore the duty of the dentist to call in a medical 
 man in consultation in cases needing his help for the relief, if not the 
 cure of the disorders which have led to the production of the above 
 distressing symptoms. 
 
 Conclusion. — It may be stated in general terms that if reasonably 
 hot and cold foods and drinks can be taken into the mouth without 
 inducing odontalgia or neuralgia the dental pulps of the teeth are 
 in good condition; and that if no obvious cause for odontalgia is present, 
 such as a carious cavity, such symptoms must be looked for elsewhere. 
 Hyperemia of the pulp is indicated and may be diagnosed if pain is 
 experienced at a localized situation on holding warm fluids in the 
 mouth, especially if a breach of enamel or dentine is associated with it. 
 
 If this examination fails and the pain still persists, the tongue may 
 next be suspected and thoroughly inspected and tested for nerve 
 
202 ODONfALGlA AND NEURALGIA 
 
 reflexes; then general constitutional causes — vascular disturbances 
 due to puberty, menstruation, pregnancy, the climacteric, etc., 
 conjectured, and finally, degenerative conditions of the dental pulp 
 may be diagnosed. 
 
 The prompt recognition of these latter changes will be convincing 
 alike to patient and dentist, and the solution of some of the problems 
 of odontalgia and neuralgia satisfactorily determined. 
 
CHAPTER X. 
 
 THE RELATION OF ORAL INFECTIONS TO GENERAL 
 HEALTH. 
 
 By KURT H. THOMA, D.M.D. 
 
 Infection in the jaws is not a modern disease. Centuries ago tooth 
 abscesses were common among the Egyptians of the predynastic 
 period, as well as of the Old and Middle Empires. In a study which 
 the writer made at the Peabody Museum of a large number of Egyptian 
 crania it was found that as far back as 4800 B.C. people suffered from 
 alveolar abscesses. This was evident from the bone destruction seen 
 around diseased teeth. The condition, however, arose then from a 
 source different from its origin today. Instead of decay leading to the 
 pulp infection, the primary cause was abrasion of the tooth surface, 
 
 Fig. 125 
 
 that is, wearing away of the tooth until the pulp became exposed 
 (Fig. 125, A). This abnormal wear on the teeth was caused by the 
 coarseness of the food, as well as by the grit present in their cornmeal 
 after its preparation in stone mortars. The infection, which gained 
 entrance in this way, proceeded through the opening in the root into 
 the surrounding bone, as it does today (Fig. 126). In those days, 
 however, the opening in the tooth was not sealed up by a root canal 
 filling and so there was a permanent outlet for accumulating pus. 
 
 In our time oral infections are so common that there are very few 
 people who have not at least one abscessed tooth. On account of the 
 chronic character of most of these infections, patients as a rule are 
 entirely unaware of their existence. The frequency of such lesions is 
 
204 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 well brought out by Dr. Black of Chicago, in statistics which he com- 
 piled from roentgen pictures of all the teeth of 300 people. These 
 examinations were not made because of any complaint, or indication of 
 treatment and, therefore, they represent as near an average of such 
 
 Fig. 126 
 
 conditions as can be obtained. The following tabulation gives the 
 result: 
 
 Number of patients 
 
 Age. 
 
 Percentage of 
 
 examined. 
 
 Years. 
 
 dental affections 
 
 86 
 
 . . . . Under 25 
 
 56 
 
 53 
 
 . . . . 25 to 29 
 
 72 
 
 68 . . . 
 
 . . . . 30 to 39 
 
 87 
 
 53 
 
 . . . . 40 to 49 
 
 89 
 
 40 
 
 .■ . . . Over 50 
 
 100 
 
 PERIAPICAL INFECTIONS. 
 
 The most important oral infections to be considered in connection 
 with the general health are those affecting the periapical tissues. 
 The infection nearly always enters through the root canal, but occa- 
 sionally it finds its way to the inside of the jaws through a pus pocket 
 along the side of the root of a tooth. Infection from the root canal 
 may result either from an acute or chronic pulpitis caused by decay, 
 from a necrotic pulp or an infected root canal which has not been 
 properly sterilized and filled, or from root canal instrumentation. 
 Fig. 127 shows a photomicrograph of a molar with a cavity from which 
 bacteria penetrated into the pulp through the dentinal canals, forming 
 a large abscess (A) in the pulp chamber. The nerves of the pulp have 
 been pressed to one side and surround the abscess. Fig. 128 shows 
 a roentgen picture of a tooth where the infection has started from a 
 
PERIAPICAL INFECTIONS 
 
 205 
 
 pocket (A) on the mesial side of a molar. When the apex of the 
 tooth was reached an abscess formed, which infected the pulp in this 
 otherwise healthy tooth. 
 
 Fig. 127 
 
 W^ ' 
 
 Fig. 128 
 
 Periapical infection may follow either of two distinct chains of 
 pathological changes. The first is of a destructive nature and begins 
 with a reaction causing all the symptoms of acute inflammation, while 
 
206 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 the other from the beginning is characterized by a mild and chronic 
 reaction, which starts and continues without giving any local symptoms. 
 
 Acute Periapical Infection. — This condition starts as acute peri- 
 odontitis and involves a violent inflammatory reaction of the tissue. 
 Purulent exudations soon accumulate, the cells of the peridental mem- 
 brane and the surrounding bone become destroyed and the condition 
 is then called an acute alveolar abscess. This may spread and cause 
 suppurating ostitis of greater extent, or the pus may soon find an outlet 
 to the surface via the Haversian canals, which penetrate the outer 
 cortical layer of bone. When the pus collects under the periosteum, a 
 reaction sets in at once, causing a widespread serous infiltration of 
 the soft parts, the cheek or neck. Finally the pus burrows a channel 
 through the soft tissue, forming a fistula into the mouth, nose, maxillary 
 sinus, or outside of the face. After this process of destruction has 
 reached its climax Nature makes an attempt at repair and the acute 
 symptoms disappear, but unless the cause (a diseased pulp or necrosed 
 root apex) is removed the condition becomes chronic. In this stage it 
 may last for an indefinite period with the fistula discharging pus if the 
 destructive process becomes more active, or closing up for a time if the 
 defensive system predominates, only to reopen with more or less marked 
 subacute symptoms when suppuration again becomes more active. 
 
 Blind Abscess or Dental Granuloma. — The difference between an 
 acute alveolar abscess and a blind abscess, or dental granuloma, should 
 be clearly understood. The former is a suppurative inflammation and 
 involves a process of destruction of the peridental tissues, dissolving 
 them into pus. The latter is a reaction to a mild infection, stimulating 
 inflammatory new growth and active suppuration does not occur at 
 first, but an exacerbation may change the pathological picture later 
 so as to simulate a typical acute alveolar abscess. The blind abscess, 
 or granuloma, begins and continues to grow without giving any symp- 
 toms. The defensive system of the body takes care of the slight 
 amount of pus formed, which is absorbed through the lymphatics, or 
 blood channels. Sometimes a dental granuloma is described as being 
 a tumor, but this is not correct, as it is distinctly of infectious origin 
 and histologically presents a picture of chronic inflammation. The 
 lesion of course increases at the expense of the bone. A picture of a 
 skull (Fig. 129) showing such a tooth will illustrate the condition. It 
 shows a bicuspid, the root canal of which has probably been treated. 
 The hole in the bone (A), with the many fine canals surrounding it, 
 represents the amount of destruction which has taken place. Another 
 picture (Fig. 130) shows a tooth with a chronic abscess, as seen under 
 the microscope. This abscess is what fills the hole in the bone. It 
 shows the end of a root (A), to which is attached a small sac (B). 
 This'has been stained with a connective tissue stain, so as to bring out 
 the fibrous nature of the capsule (C) surrounding the lesion. The 
 inner part shows three centers of broken down tissue and if examined 
 with a high power lens it would be found to contain many vessel^ 
 
PERIAPICAL INFECTIONS 
 
 207 
 
 surrounded by large numbers of lymphocytes, plasma cells and leuko- 
 cytes. These have special biological functions. The first two are 
 
 Fig. 129 
 
 Fxq. 130 
 
208 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 said to neutralize and eliminate toxins, while the latter are of phago- 
 cytic nature, destroying and fighting the invading bacteria. Pus is 
 continually formed in small quantities in the abscess. There is 
 generally no outlet, the original opening through the root canal and 
 cavity in the crown having been closed by the filling, so that the pus 
 is taken up by the blood stream and carried away. 
 
 Condition of the Tooth Apex. — Periapical infection, especially if it is of 
 long standing, causes changes in the cementum of the tooth. Nutri- 
 tion is usually disturbed, the cells of the apical part of the peridental 
 membrane may become destroyed and the cementum, which is very 
 
 Fig. 131 
 
 porous and easily absorbs the products of inflammation, becomes pus- 
 soaked and filled with bacteria. In this condition the tooth is an 
 obnoxious foreign body which Nature tries to eliminate by osteoclastic 
 absorption, starting on the surface of the cement, which then presents 
 a roughened appearance (Fig. 131, A). Marked indentations are formed 
 and the cement, and later the dentine also, dissolves. At times new 
 cement is deposited, due to stimulation of cementoblasts, which have 
 survived. This causes enlargements of the root end and often renders 
 extraction of the tooth extremely difficult. The reason why an abscess 
 of long standing is so stubborn and impossible to eliminate by any 
 means other than surgical treatment is on account of the infection of the 
 
EXTENSIVE LESIONS CAUSED BY PERIAPICAL INFECTION 209 
 
 apical part of the tooth root, which is a dead piece of bone and, like a 
 sequestrum, has to be removed before healing can take place. The 
 process of absorption indicates plainly that Nature wants to accom- 
 plish the elimination of the tooth. Fig. 132 illustrates a photomicro- 
 graph of a tooth with a blind abscess (A), showing absorption (B), 
 not only of the outer layer of cement, but the entire apex of the root. 
 
 Fig. 132 
 
 Exacerbations. — If more pus is formed than can be taken care of 
 and eliminated by means of absorption it may result in the formation 
 of a fistula. This is generally known as a gum-boil. Everyone knows 
 that a great deal of pus can be squeezed from a gum-boil several times 
 a day and this makes it easier to understand that such pus, when 
 drained into the system, must be injurious to the health. 
 
 MORE EXTENSIVE LESIONS CAUSED BY PERIAPICAL INFECTION. 
 
 If we consider the frequency of dental infections it is surprising how 
 rarely we find extensive bone infection and serious involvement of the 
 adjoining structures and the alveolar process. The reason for this is 
 probably to be found in the bountiful blood supply of the bone in the 
 immediate neighborhood of the roots of each tooth, from which a 
 defensive system is built up to prevent the spreading of infection, carry- 
 14 
 
210 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 ing away the products of bacterial activity so successfully that there 
 is seldom even an outlet, or fistula, formed to the face or gum. Peri- 
 dental infections sometimes result in extensive lesions of the jaw, as 
 well as radicular or periodontal cysts, which are also of the infectious 
 type. It is a deplorable fact that they are generally not recognized 
 for a long time and are often treated for months by means of root canal 
 medication without making an accurate diagnosis. 
 
 Fig. 133 
 
 Fig. 134 
 
 Ostitis. — This is a bone infection of a more extensive type, developing 
 often from periapical infections. It may be of the suppurative type, 
 accompanied by violent acute symptoms, but more often is of chronic 
 character, developing from chronic periapical infection. This type is 
 called granulating ostitis. It may involve large portions of the jaw 
 
EXTENSIVE LESIONS CAUSED BY PERIAPICAL INFECTION 211 
 
 and several teeth without causing much swelHng or pain. A roentgen 
 picture of granulating ostitis is shown in Fig. 134. Note the large, 
 dark area of irregular outline, marked A. Fig. 133 shows a picture of 
 an ordinary blind abscess (A) for comparison. 
 
 Diffuse Osteomyelitis. — This condition is, fortunately, very rare, 
 but when it occurs is a serious disease. It spreads, as a rule, from one 
 side of the jaw to the other and with the best of care it often takes 
 months for complete recovery. Fig. 135 shows such an infection, 
 which started from an abscessed tooth, improperly treated. When 
 the dentist finally extracted it the disease had already spread all over 
 the jaw, as indicated in the roentgen picture by the dark channels 
 extending throughout the jaw. 
 
 Fig. 135 
 
 Cysts. — Cysts are found quite frequently. The writer has seen a 
 large number during the last few years. They are caused by chronic 
 abscesses and as their secretions accumulate they increase to enormous 
 size. They form a large cavity in the bone, which sometimes reaches 
 the size of a hen's egg and always contains pus. The bone itself is not 
 infected, but is absorbed and becomes so thin sometimes that it can be 
 bent when pressed with the finger. In the upper jaw cysts may en- 
 croach on the nasal cavity or develop inside the maxillary sinus, some- 
 times filling it almost completely, a condition which is very difficult 
 to diagnose. In the lower jaw they are found in the body of the man- 
 dible, as well as in the ramus. Radicular cysts sometimes have appar- 
 ently no connection with a tooth root. In such cases the guilty tooth 
 may have been extracted, the cyst having escaped notice at the time, 
 or there may have been left in the jaw an epitheliated granuloma, which 
 developed into a cyst later. Fig. 136 shows such a case. A indicates 
 the cyst. 
 
 The diagnosis of a cyst is easily made by means of roentgen pictures. 
 
212 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 The examination should be made on large films or plates, as the small 
 ones seldom cover more than a part of the lesion. The cyst cavity 
 
 Fig. 136 
 
 appears as a black area on the negative because it decreases the resist- 
 ance which, in normal bone conditions, is put in the way of the rays. 
 
 Fig. 137 
 
 The bone immediately surrounding the cavity, however, is usually 
 cortical and dense and so we find the typical picture of a cyst showing 
 a light, but distinct, surrounding line {A),we\\ illustrated in Fig. 137. 
 
INFECTED TEETH AS A SOURCE OF SYSTEMIC DISEASE 213 
 
 Infection of the Maxillary Sinuses. — Maxillary sinusitis in both the 
 acute and chronic types is, in a large percentafi;e of cases, due to dental 
 infections. Abscesses on the upper bicuspids and molars are frequently 
 the cause of infection of the maxillary antra. Fig. 138 shows the 
 intimate relation of the tooth apices with the antrum {A). Only a 
 very thin layer of bone separates the tooth from the mucous membrane 
 of the sinus. Acute sinus infection may be caused by careless instru- 
 mentation or the pushing of an infected root into the antrum. Chronic 
 maxillary sinusitis with polypoid degeneration is a condition which 
 also often occurs without the patient's knowledge and may be dis- 
 covered only during a routine examination. If abscessed teeth are 
 found in the upper jaw the sinuses should always be investigated, and 
 in all cases of maxillary sinus disease the examining physician should 
 insist upon roentgen films of the teeth. 
 
 Fig. 138 
 
 Ludwig's Angina. — Ludwig's angina is also one of the consequences 
 of alveolar abscesses. Most cases observed by the waiter have followed 
 the extraction of teeth, the infection spreading rapidly and causing an 
 acute infiltration of the soft tissues of the floor of the mouth. The 
 board-like swelling presses the tongue upward and backward into the 
 pharynx, which causes the well-known symptoms, difficulty in breath- 
 ing and swallowing and great anxiety on the part of the patient. The 
 mortality from this infection is very great. Death may occur in from 
 ten to twenty days. 
 
 INFECTED TEETH AS A SOURCE OF SYSTEMIC DISEASE. 
 
 Since the days of Hippocrates it has been known that infections of 
 dental origin may be accompanied by serious systemic symptoms. 
 This celebrated writer, who was born four hundred and sixty years 
 before Christ, makes the following statement: "At the approach of 
 dentition pruritis of the gums occurs and fevers, convulsions and 
 
214 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 diarrhea, especially when cutting the canine teeth." The eruption of 
 the teeth, therefore, must have been frequently attended by acute 
 infection. This is the first writer who mentioned the effects of dental 
 infections upon the general system. 
 
 In any infection we have both local and general effects. The 
 general effects in acute infections come on suddenly and are well 
 marked, even alarming. This is principally due to the fact that the 
 cause is a strong injurious agent, such as very pyogenic organisms. In 
 chronic inflammation we have a reaction to a mild injurious agent and 
 the systemic effects come on slowly and may even be so slight that no 
 symptoms occur as long as the protective forces of the body are able to 
 take care of the condition. However, as soon as the general resistance 
 of the body is lowered by such things as debilitating disease, poor 
 physical condition or pregnancy, or if the local resistance of a part is 
 decreased by exposure or interference with nutrition, serious complica- 
 tions may gradually develop and frequently the patient is not aware of 
 the trouble until irreparable harm is done. The following observation 
 of two patients may serve as an illustration. The first, a woman with 
 a perfectly healthy heart. Hospital Case No. 225, and the other, a 
 patient with a weak heart. Hospital Case No. 211, both had the same 
 amount of vaccine injected. The first patient, a well developed and 
 well nourished woman, had been suffering from chronic arthritis for 
 twenty-one months. Lungs, normal; heart sounds regular and of 
 good quality. On February 20 vaccine treatment was begun. Injec- 
 tion of 75,000,000 typhoid bacteria with 100 c.c. of normal salt solution 
 was made at 3.30 p.m. into the median basilic vein. She had a definite 
 chill, which lasted twenty minutes, but otherwise there were no heart 
 symptoms. Temperature and pulse curve shown on chart (Fig. 139). 
 By 9.30 these were perfectly normal. A second vaccine treatment of 
 100,000,000 bacteria, given eight days later, produced a similar result. 
 
 The second patient, a woman 36 years old, was admitted for chronic 
 arthritis. Had had measles, diptheria and scarlet fever when a child; 
 at the age of twelve, "St. Vitus' dance," which lasted two years; two 
 attacks of pneumonia when fifteen years old and rheumatic fever seven 
 years ago. Her present illness began eighteen months ago, when she 
 noticed pain and stiffness in the knees. The joints of the fingers, 
 elbows and shoulders then became involved. Present examination 
 shows slight edema in ankles, teeth poor, glandular enlargement in 
 submaxillary region on both sides. There was a systolic murmur of 
 the heart, but no evidence of physiologic disease. On February 15 
 at 4.15 P.M. the patient received a vaccine injection of 75,000,000 
 bacteria intravenously. At 5 p.m. there were signs of reaction, chill, 
 typical spasmodic shaking, but no complaint of cold. Had marked 
 cardiac symptoms at 9 p.m. Patient was dyspneic, cyanotic and cough- 
 ing. Sputum was salmon colored. Distress, dyspnea and headache 
 lasted until about midnight and the next day there was still tender- 
 ness and palpitation over the precordia (Fig. 139, B), 
 
INFECTED TEETH AH A SOURCE OP' SYSTEMIC DISEASE ^15 
 
 These two cases illustrate the different effect on two patients of a 
 small and limited amount of toxin, the same in both cases. The healthy 
 patient, in this case the one with the strong heart, can easily take care 
 of a slight infection, while another patient not in perfect health may 
 suffer from a similar cause most severe effects. 
 
 Fig. 139 
 
 Systemic EfEects from Acute Dental Infections. — Constitutional 
 effects are nearly always present in acute infection. They are evidenc- 
 ed by fever; that is, raised temperature, quickening of the pulse and 
 respiration rates, headaches, flushing of the face, brightening or injec- 
 tion of the eyes, dry hot skin, constipation, highly colored urine and, 
 in serious cases, perhaps also delirium at night. 
 
 Leucocytosis is called forth in nearly all cases of acute infection as a 
 protective reaction by stimulation through the toxins of the bone 
 marrow and other places where leukocytes are formed. 
 
 Discharges are especially marked in the critical stage. They are 
 profuse sweating, sometimes hemorrhage from the mucous membranes 
 and often diarrhea. 
 
 All these constitutional s^Tuptoms may be slight or well marked, 
 according to the physical health of the patient, as well as to the viru- 
 lence of the infection. In serious cases the absorption by the blood 
 circulation may become so extensive that we speak of the condition as 
 a blood infection, or septicemia. While we generally get absorption 
 both of bacteria and their toxins we may distinguish various typical 
 conditions. 
 
216 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 Bacteremia. — Bacteremia is a condition in which the bacteria are 
 absorbed from the original seat of infection and circulate and grow in 
 the blood. If, however, the bacteria are very pyogenic and elaborate 
 toxins we employ usually the general term of septicemia. The symp- 
 toms are those already described. In addition, however, there is 
 usually a chilly sensation or actual chills. The pulse becomes more 
 rapid and progressively weaker and the temperature rises until death 
 occurs. (See Fig. 140.) 
 
 DAY OF 
 MONTH 
 
 9 
 
 
 10 
 
 
 
 11 
 
 
 
 
 12 
 
 
 
 107 
 106 
 
 .105 
 o: 
 
 2l04 
 H103 
 
 UJ ^ 
 
 |l02 
 
 101 
 
 100 
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 Fig. 140. — Puerperal septicemia; death. (Ashhurst, Episcopal Hospital.) 
 
 Pyemia.^ — This blood infection is generally due to a cluster of bacteria 
 or an infected blood clot entering the circulation. It then usually 
 lodges in a capillary and the bacteria produce suppuration in the new 
 location. Thus a new abscess forms, which is called a metastatic 
 abscess. This may be located in any part of the body and is fre- 
 quently found in the heart, lungs, liver or joints. Suppurative lesions 
 in the bone are most frequently the seat of the primary focus. Fig. 
 141 shows a temperature chart in a fatal case of pyemia. 
 
 Toxemia. — If the bacteria remain in the primary lesion and only the 
 toxins (both true, special toxins, and the poisons produced by the 
 biological activity of pyogenic bacteria) are absorbed the condition is 
 spoken of as toxemia. This should be differentiated from auto- 
 intoxication due to poisoning by non-bacterial substances such as 
 drugs and products of perverted metabolism. According to the amount 
 and quality of the toxins and the reaction of the individual we speak of 
 acute and chronic toxemia. The latter /ill be discussed under systemic 
 effects from chronic infections. Acute toxemia cannot very well be 
 distinguished from septicemia by symptoms, as these are almost the 
 same. It yields quickly to treatment, however, and if the cause 
 
tnPECTED TEETH AS A SOURCE OF SYSTEMIC DISEASE 21? 
 
 (the bacterial focus) is removed the symptoms usually disappear 
 promptly. If, however, the septic focus is not found it may terminate 
 in septicemia. 
 
 Fig. 141. — Temperature chart in pyemia; acute osteomyelitis of calcaneum; abscess of 
 brain; death. (Ashhurst, Episcopal Hospital.) 
 
 Sapremia. — Sometimes dead tissue, such as a dead pulp, remains 
 in the body without being infected by pyogenic bacteria. Saprophytic 
 bacteria may then develop and form ptomains which, when absorbed, 
 
 DAY OP 
 MONTH 
 
 25 
 
 26 
 
 
 2r 
 
 
 
 28 
 
 
 29 
 
 104° 
 .103 
 
 I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 99 
 
 98 
 
 97 
 
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 Fig. 142. — Sapremia; rapid fall of temperature after evacuation of retained secundines. 
 (Ashhurst, Episcopal Hospital.) 
 
 give symptoms similar to toxemia. As long as the dead tissue remains 
 there will be constitutional effects, but these disappear after removal 
 and there is usually a prompt restoration of health. Fig. 142 shows a 
 
218 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 temperature chart from a case of sapremia. The temperature fell 
 immediately after removal of the dead tissue. 
 
 Systemic Effects from Chronic Dental Infections. — In chronic 
 infections lesions such as have already been described often start and 
 persist for a long period without local symptoms and we rarely get 
 acute general manifestations, such as fever and other symptoms con- 
 nected with septicemia due to acute infection. It is now conceded, 
 however, by most pathologists of this country that a number of general 
 diseases are caused by the continued absorption of bacteria or their 
 poisonous products from such a chronic inflammatory focus. This 
 transportation of an infection from the primary lesion to another place 
 is spoken of as focal infection. 
 
 The Focus. — ^The focus is the name given to the primary infection, 
 from which bacteria or their toxins may be transported to other parts 
 of the body. It may be found in any part of the body, but the nose 
 or throat and adjacent sinuses, the oral cavity, the alimentary canal, 
 and the genito-urinary system are the parts in which foci are found most 
 frequently. Foci are not always apparent and are often only recog- 
 nizable after a most careful examination by the specialist. 
 
 Oral Foci. — It is a mistake to spread the impression that diseases 
 of the mouth and teeth always play a predominant part, as much as it is 
 a mistake to think that the teeth and their investing tissues are organs 
 apart from the rest of the body reacting, for some mysterious reason, 
 differently from the rest of the human organism. Various oral lesions 
 of infectious origin have already been described. The blind abscess or 
 dental granuloma among these is the most frequent cause of systemic 
 disease, but also pulp infection, pyorrhea and other bone infections 
 of the jaws which are of less frequent occurrence may play an important 
 part. The bacterial flora of the mouth includes not only a large number 
 of saprophytes which live on dead tissue, but also an extensive variety 
 of the pyogenic organisms, among which especially prominent are the 
 different types of streptococci, the staphylococci, pneumococci and 
 micrococcus catarrhalis. 
 
 Mode of Distribution of the Infection from Oral Foci. — Dental 
 abscesses with fistulse and pus pockets discharging into the mouth 
 furnish a continual supply of infectious organisms which may cause 
 diseases of the throat, lungs and mucosa of the alimentary canal. 
 From a deep-seated focus with no outlet infection may take place 
 through the lymph. There are two groups of lymph glands which 
 drain the jaws and teeth. The submental glands take care of the region 
 of the lower incisor teeth. The three submaxillary lymph glands on 
 each side drain the rest of the teeth and their investing tissue. All 
 are tributaries of the lymph nodes of the neck. These glands are hardly 
 noticeable when normal, but in acute infections they become enlarged 
 and very tender to touch. In chronic infections they may also become 
 enlarged, but are harder and not painful on palpation. The lymph 
 vessels may also become involved and in this case we speak of the 
 
INFECTED TEETH AS A SOURCE OF SYSTEMIC DISEASE 219 
 
 condition as lymphangitis. The lymph glands are more liable to be 
 enlarged in children, but l\Tnphatic infection is not at all rare in 
 adults. The most important path of absorption, however, is through 
 the circulation. Acute infections always cause more or less involve- 
 ment of the general system, but also in chronic infections the disease is 
 rarely entirely localized. Bacteria, or the toxins formed by bacterial 
 absorption, or both, are taken up by the blood stream in the focus, 
 which is always very rich in primitive vessels* causing a bacteremia or 
 chronic toxemia. The result, however, does not cause cross s,^^Ilptoms, 
 as in acute septicemia, but is of so mild a character that the patient's 
 health may be considerably undermined before any marked effect is 
 noticeable. 
 
 Secondary Lesions.^ — ^The bacteria or toxins taken up by the blood 
 may be carried to any part of the body by the circulation and produce 
 new disease, or secondary lesions. The type of secondary disease and 
 the part affected depend upon a great many factors. Predisposing 
 causes and debilitating diseases are very important, while traumatic 
 injury, exposure to fatigue, malnutrition, pregnancy and other con- 
 ditions which lower the resistance give opportunity for bacterial inva- 
 sion. The varieties of bacteria, of course, probably have tendencies 
 toward growth in certain tissues and according to Rosenau's latest 
 studies, members of the same type may develop affinities for certain 
 tissues. Streptococci taken from an infected heart muscle would, if 
 injected into the blood stream of another animal, again elect to invade 
 the tissues of the heart. 
 
 Secondary diseases are, however, also caused by absorption of bac- 
 terial toxins only. While these may not be of sufficient strength to 
 cause acute toxemia they can, in susceptible patients, cause serious 
 disturbances, both general and local. Especially delicate tissues are 
 affected so that physical discomfort and mental depression may result. 
 
 Establishing Proof of Systemic Infection. — Often it is difficult to 
 determine whether absorption takes place from suspicious teeth. 
 As a rule there is little doubt as to what should be done with infected 
 teeth, from a purely dental point of view, or even simply for the sake of 
 cleanliness. No one who has studied the tooth and bone pathology 
 of conditions caused by old pus-soaked teeth, or who has experienced 
 the odor of one which has been removed, will hesitate to recommend 
 extraction. There are, however, cases where we might recommend 
 more conservative treatment if we were sure that no absorption was 
 taking place. 
 
 Two tests are available to decide whether absorption of bacterial 
 poisons has occurred. One is a blood test, the other a skin test, such 
 as that used in testing for food poisoning. In conjunction with Dr. 
 Lawrence of Boston I have experimented with these tests. The 
 following is an example. 
 
 Mr. G., a chauffeur, had been unable to drive a car, on account of 
 pain in his back and shoulders. Roentgen pictures of his teeth (Figs. 
 
220 
 
 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 143 to 152) showed many devitalized teeth and several abscesses, (marked 
 A, B, C and D) ; also a pus pocket (marked E), and careful examination 
 
 Fig. 143 
 
 Fig. 144 
 
 revealed no other possible cause for his condition. The blood test, 
 known as the complement-fixation test, showed a reaction to two types 
 of streptococci, the toxins of which were being absorbed. The skin 
 
 Fig. 145 
 
 Fig. 146 
 
 test was positive to the same organisms. The abscessed teeth were 
 extracted, cultures were made from each, and again pure cultures of 
 the same organisms were obtained. The patient improved so much 
 
 Fig. 147 
 
 Fig. 148 
 
 after removal of the focus that he was soon able to go to work and 
 is now driving a truck. 
 
INFECTED TEETH AS A SOURCE OF. SYSTEMIC DISEASE 221 
 
 General and Special Diseases which may Originate from Oral Infections. 
 
 In the following list are enumerated some of the special and general 
 diseases which may have their origin in the oral cavity. It should be 
 clearly understood that all these conditions may arise from a focus in 
 any part of the body and that diseases of the teeth are not the only 
 etiologic factors, nor even the most important ones. In compiling 
 this list the writer has aimed to include only such diseases as are at 
 present generally conceded to be caused by focal infection. 
 
 * ^ ^ 
 
 Fig. 149 
 
 Fig. 150 
 
 Laryngology, Rhinology and Otology. — Maxillary sinusitis in its 
 various clinical forms is quite often caused by dental infections. 
 However, in cases which are clearly of nasal origin infected and devi- 
 talized teeth may become a contributary cause which, if not removed, 
 will prevent complete recovery. Tonsillitis and pharyngitis may occur 
 from pus discharged into the mouth. Ear infection, such as acute 
 otitis media or chronic purulent inflammation of the middle ear and 
 tympanum may be caused by direct invasion through the Eustachian 
 
 Fig. 151 
 
 Fig. 152 
 
 tube, or the infection may be transported by the circulation. Pain in 
 the ear, so-called otalgia dentalis, is frequently only a reflex pain 
 from some cause in or about the teeth. 
 
 Ophthalmology. — Disturbances in the eye may be brought about by 
 nerve irritation, or through hematogenous or direct infection. Infec- 
 tious conjunctivitis in children is often caused by rubbing the eyes 
 with the fingers, which have been put into the mouth to feel an aching 
 
222 RELATION OF ORAL INFECTIONS TO HEALTH 
 
 tooth, which discharges pus through a fistula. The pus may get on the 
 child's finger and be brought into direct contact with the eyes. Hema- 
 togenous infection may cause infection of other parts of the eye, such 
 as iritis and retrobulbar neuritis. 
 
 Pediatrics. — Children are frequently victims of focal infection caus- 
 ing grave and sometimes irremediable conditions, such as heart disease 
 (endocarditis), kidney disease (nephritis) and acute inflammation of 
 the joints. Acute or chronic l^TQphadenitis is also a common occur- 
 rence in children. 
 
 General Medicine. — Septicemia and pyemia may be caused by infec- 
 tions from the teeth, but are of comparatively rare occurrence. Tox- 
 emia, however, is more frequently observed. Many obscure troubles 
 are due to absorption of a small amount of toxin. Such symptoms 
 may be fatigue disproportionate to the slight exertion occasioning it, 
 inability to do the accustomed day's work, mentally or physically, 
 benumbed mental activity, requirement of an abnormal amount of rest, 
 loss of weight, grayish or sallow skin, and a rise in the temperature in 
 the afternoon or evening. A perfectly healthy person may be able to 
 eliminate a certain amount of infection, but sooner or later more serious 
 results are apt to occur. Lowering of the body temperature by 
 exposure to cold or wet may give rise to more or less vague rheumatic 
 conditions in the muscles, (myositis), joints, (arthritis), or nerves, 
 (neuritis) . Cases of acute multiple arthritis from dental infections are 
 not uncommon and usually improve rapidly after removal of the focus. 
 In chronic infections, especially arthritis of long standing, the results 
 are not so gratifying. The joints may present tissue changes which 
 are beyond repair from an anatomical point of view. The removal of 
 the focus, however, usually relieves symptoms of pain and swelling and 
 prevents reinfection from this cause. 
 
 Endocarditis and nephritis are also caused in the adult by transported 
 infection from a focus. In heart infections there is the additional 
 danger of damage due to absorption of toxins from any infectious 
 lesion, not necessarily the cause of the disease. 
 
 Gastro-intestinal disorders are frequently caused by pus from the 
 nasopharynx or mouth being swallowed into the stomach. According 
 to many writers the most common disturbances are septic gastritis, 
 appendicitis, colitis and gastric and intestinal ulcers. 
 
 CoNCLpsiON. — ^The lesson to be learned from these studies is the 
 importance of laying more stress than ever upon the preventive side 
 of dentistry. Preservation of the dental pulp and its sequel, preven- 
 tion of periapical infection, starts at an early age. Preventive dentistry 
 should begin with children and no treatment will further this object 
 more than the excellent work of the dental hygienist. 
 
CHAPTER XI. 
 DENTAL PROPHYLAXIS. 
 
 By ALFRED C. TONES, D.D.S. 
 
 THE CELL. 
 
 In order to appreciate health it is necessary to be familiar with 
 the facts concerning the individual cell, and the effect of various influ- 
 ences upon the unit must be studied before an understanding can be 
 had of the action and influence upon the cells in the aggregate. If 
 a drop of water is taken from the side or bottom of an aquariimi and 
 put in a glass under the microscope, a minute jelly-like mass may be 
 seen. Its outer circumference slowly changes its shape, while near the 
 center there is a very minute globule termed the nucleus. This is 
 the lowest and simplest form of animal life and is known as the ameba. 
 This simple cell has seven distinct properties. It may extend its 
 wall in projections like false feet, or protuberances, or may flatten 
 itself out in a long line, therefore it has the property of elongation. 
 When irritated by being brought into contact with dilute acid it will 
 contract into a round form; hence, it has the property of contraction. 
 These two properties give it its power of motion. It appreciates the 
 presence of irritants, of food and of thermal changes, therefore it has 
 the power of sensation. It can digest food and discard waste tissue, 
 therefore it must have the properties of secretion and elimination. 
 The cell and nucleus have the power of dividing themselves in two, 
 thereby forming two cells. It has the power of reproduction, and the 
 new cells have the property of growth. 
 
 When all of these functions or properties of this simple cell are work- 
 ing normally, the ameba is in a state of health or balance. Rob it 
 of one or more of its properties and it is diseased. Stimulate the cell 
 by applying certain agencies and its motions become more rapid, it 
 consumes its food more rapidly, it will subdivide and reproduce 
 itself more rapidly. A greater stimulant will cause a still greater activ- 
 ity, but if this is continued the cell soon becomes exhausted and par- 
 alyzed from exertion and the ultimate result will be death. The reverse 
 takes place under sedation produced by applying cold. The motions 
 become slower, also digestion and reproduction. If the temperature 
 is dropped too low, the cell dies. Pollute the water or rob it of its 
 oxygen and the cell dies. Cell life is maintained chiefly by a chemical 
 process of oxidation. It must have water and it must have a food sup- 
 ply to replace the lost substance which is gradually being utilized 
 
224 DENTAL PROPHYLAXIS 
 
 in performing its various properties and functions. It is therefore 
 apparent that cell life is dependent upon oxygen, water and food, 
 a proper temperature and removal of waste matter. 
 
 Nature, in the building of all matter, builds from the unit. Although 
 the atom is the smallest unit, the molecule of the mineral kingdom and 
 the cell of the animal and vegetable kingdoms are the general bases 
 for study. All earthly creations visible to us are formed on this one 
 plan. The trees, the flowers, the grass, the mountains, the beach, 
 the sea, all animal life, including man, each is made by the combining 
 of these units, all working with an intelligence and subject to chemical 
 laws far beyond our comprehension. 
 
 Why it is that the contents of the cell, which is called protoplasm 
 and which appears to be nothing but a jelly-like mass, has the property 
 of manifesting life and intelligence, is difficult to understand. This 
 substance can be analyzed and even the proportion of its elements 
 estimated, yet what unseen force imbues it with energy and intelli- 
 gence and what becomes of this life-giving power when the cell dies 
 and disintegrates, is not known. Cell action can be studied, and the 
 cell can be supplied with the essentials for growth and development. It 
 is a realized science that in animal life, certain factors properly applied 
 at the proper age can greatly develop its function and intelligence, 
 the same as in vegetable life, but it cannot be explained. It is known 
 that all manifestation of life and of intelligence is expressed through 
 this matter contained within the cell. 
 
 In the gradual evolution of these simple cells, like the ameba, com- 
 bining to form larger and more complex organisms, it is found that 
 the cells choose a specialty of two or three of these properties, and those 
 whose specialty is the same are grouped together. As animal life 
 develops into higher planes the cells become more proficient in their 
 specialties, until in man is found the greatest variety of highly special- 
 ized cells in animal life. While the ameba possesses a balance of seven 
 properties, some of the specialized cells of man concentrate on but one 
 function. It may now be seen how these cells of man that have under- 
 gone a slow evolution of millions of years to reach their present degree 
 of intelligence are reflected in this low and simple order of life — the 
 ameba. It has been stated that the ameba has seven properties. Its 
 power of contraction is exemplified in the muscle cells of the human 
 body, whose specialty is contraction. These cells are capable of 
 wonderful development and training. The finger touch on the piano 
 keys, the surgeon with his instruments, the dancer, the juggler, the 
 athlete, the artist, and the artisan, all demonstrate how these minute 
 individuals receive impressions from the brain and nerve centers and 
 interpret them with such wonderful intelligence. The nerve cells 
 specialize on the transmission of sensation and vibratory influences to 
 and from the brain. Digestion and elimination, being very much more 
 complicated in higher animal life, require innumerable cells which 
 perform separate functions — the passing on of food, the secretion of 
 
THE CELL 225 
 
 fluid for its solution and its preparation for absorption. In the 
 blood stream are cells floating along, each intent on its special duty. 
 The liver, with its cells actively engaged in preparing the waste prod- 
 ucts for elimination by the kidneys, the sweat glands, the lungs, 
 the brain (that wonderful terminal station, headquarters for all orders) 
 all are composed of these specialized units working together like so 
 many people in an immense city, each adding his mite in labor and 
 service for the common prosperity and health. 
 
 The intelligence displayed by the individual cells of the body is 
 the marvel of scientific investigators in physiology and pathology. 
 Much is yet wrapped in mystery and many years will pass before some 
 of the deep problems of nutrition and the hard-fought battles waged 
 against disease will be fully understood. 
 
 When the body is abused this abuse is imposed upon millions of 
 intelligent beings who do their utmost to offset ignorance and wilful 
 acts by patiently combating the impositions and trying to correct 
 and repair the damage wrought. In early youth the cells are in abun- 
 dance and the supporting structures are but partially formed. In 
 adult life the work of the cell is completed, and the intercellular struct- 
 ure is in predominance. The great period for structure building and 
 for the guidance of proper cell development, physically and intellect- 
 ually, by applying scientific factors to properly infiuence this result, 
 is from infancy to twelve years of age. 
 
 As a spider spins his web so do these minute cells create tissue 
 to aid them in their work. The individual refiects the composite 
 texture and make-up of the aggregate cells of the body, and the period 
 for molding, refining and advancing this cell development to its highest 
 plane is in early youth. 
 
 Factors for Cell Life. — ^The scientific factors for influence are numer- 
 ous, but there are a few that stand out conspicuously. First of all 
 comes pure air, for cell life is dependent upon constant oxidation. 
 Next comes a proper food supply. The character of food will eventu- 
 ally determine the character of the cell, and as the body is physically 
 composed of millions of cells, the food supply in a great measure 
 determines the character of the individual. This is exemplified in the 
 glutton, the drunkard or the savage. What is eaten, how much is eaten, 
 and the manner in which it is eaten, are some of the chief factors for 
 health balance. The question of food values, the quantity consumed 
 and the importance of thorough mastication and salivation should be 
 a study for all hygienists. 
 
 Next comes cleanliness, for if disease is to be prevented clean food, 
 clean water, clean mouths, clean bodies and clean environments are 
 necessary. Mental attitude is another powerful factor and should 
 have fourth place. Self-control, optimism, that mental poise that can 
 discard fear and worry, that holds an even balance under varying 
 circumstances and that can radiate good cheer and kindness through 
 their health-giving influences to every cell of the body, are elixirs 
 15 
 
226 DENTAL PROPHYLAXIS 
 
 unequaled in the building of the character as well as in regulating a 
 perfect balance and functioning of the entire system. 
 
 Although heredity, too, plays a strong part, yet the first four factors 
 named can greatly modify the inherited disposition of the cells if wisely 
 applied. When we speak of coarse natures, we speak of an unfortunate 
 inheritance of a type of cell life that might have been greatly softened 
 and modified in childhood. 
 
 Exercise is also exceedingly important, for rest means rust even in 
 animal tissue. 
 
 If man lived what is termed a "natural" existence, which means, 
 in other words, an outdoor and primitive life, with simple coarse 
 foods and work or exercise in the open air, which develop the animal 
 side, there would be but little need of the physician or the dentist. 
 The coarse food would mechanically clean and polish the teeth by 
 friction, and the out-of-door exercise or work would cause an enforced 
 breathing which would mean a greater intake of oxygen to burn up 
 the slag and waste products in the system. But this so-called natural 
 existence is not possible to 70 per cent, of the people of the present 
 day. Their very existence depends upon their work or artificial life 
 in the cities, and the yearly increase in numbers in the cities rather 
 proves the preference for the city over the country. Therefore this 
 health problem of city life must be solved. The factors which are 
 productive of health in the animal life must be substituted artificially. 
 The passing generation cries that children are being brought up too 
 much by the teaching of science and the book instead of in the good 
 old-fashioned way of letting nature look after them. Take, for 
 example, the wild rose of the field that depends upon sunshine and 
 shade, warmth and moisture and proper soil for its growth. Nature 
 does not and cannot always supply these in sufficient degree and in 
 proper balance, and although the flower is beautiful it cannot be com- 
 pared with the beautiful rose that the horticulturist can grow when 
 these essentials are scientifically and artificially supplied. In the hot- 
 house the correct temperature can be maintained, moisture in sufficient 
 quantity supplied, sunshine and shade regulated at will and fertilizers 
 essential to stimulate growth added to the soil. The work of Burbank 
 in scientifically handling vegetable life is well known and our modern 
 methods of agriculture and fruit raising. The wonderful feats of the 
 horse, hurdling, running and trotting are due in great measure to the 
 scientific training by man. Many instances can be given in which 
 nature far excels her natural state of environments if the essential 
 factors she needs are supplied artificially and scientifically in sufficie it 
 abundance and degree. 
 
 And so it is in the growth and development of the city child, and 
 even in that of the adult. If the proper factors for health can be scien- 
 tifically administered, it is possible to grow children as far superior to 
 those of the present-day average in the public schools, as the American 
 Beauty is superior to the wild rose. Man has had his progressive 
 period; woman is having hers. The coming one belongs to the children. 
 
THE ALIMENTARY TRACT 227 
 
 THE ALIMENTARY TRACT. 
 
 Before confining thought and attention chiefly to the teeth and their 
 surrounding tissues and considering how disease may be prevented, 
 a few simple thoughts regarding the body must be presented, that it 
 may be better understood how important a part the mouth plays for 
 health or for disease. There is no better way of doing this, perhaps, 
 than first to consider a country with its many people, and show the 
 factors upon which it is dependent for health, for a close analogy may 
 be drawn between the life of a simple cell, the individual and the nation 
 as a whole. Egypt is the best for illustrating this thought, for here is 
 found a strip of life running through a region of apparent death. 
 Suppose a piece of green cloth, six inches wide and a hundred feet in 
 length, was laid on the sands of the seashore, running straight up on 
 the beach from the water's edge. If in the center of this cloth was laid 
 a long white string to illustrate the river Nile, it would be a fair repre- 
 sentation of Egypt. The Nile runs through a desert and the water 
 with its life-giving power has created a living body close to its borders. 
 In this living body are millions of people who are dependent upon this 
 alimentary tract or river for their existence. Along the banks may be 
 seen the water buckets, operated by the natives to supply their' fields 
 and gardens. In the season of the overflow the soil is soaked with 
 moisture, the crops are plentiful and there is ample for those who will 
 work. Canals or arteries lead from the river bank across the fields 
 to supply life and growth to the soil that would be desert waste with- 
 out it. If it were possible to poison the source of the Nile so that its 
 waters carried their life-giving properties no longer, but contained 
 some chemicals that were destructive to plant life, or sufficient sewage 
 to poison the inhabitants, Egypt would soon cease to exist. Just in 
 proportion to the amount of poison carried down the river would the 
 country and people suffer from starvation and disease. The bodies 
 of all animal life are constructed around their alimentary tract. The 
 lowest forms of cell life when changing to a higher organism, find it 
 essential to develop first a mouth and digestive tract, for the intake 
 of food is of first importance with all material life. The body with 
 its millions of cells is dependent upon the flow of nourishment through 
 the alimentary tract and as the individual lives and feeds so will his 
 body thrive or deteriorate. The mouth is the vestibule or gateway to 
 the whole system. All the nourishment and food supply to the body 
 must pass through this one portal. The placing of the food in the 
 mouth is a voluntary action and it can be controlled as long as it 
 remains there, but the moment it is swallowed it is beypnd voluntary 
 control and is sent on the mysterious journey called digestion, absorp- 
 tion and assimilation. 
 
 Assuming, first, that the food eaten is clean and pure and above 
 criticism, and enters a clean mouth, is properly masticated and swal- 
 lowed, digestion take place normally, provided the mental 9,ttitude 
 
228 DENTAL PROPHYLAXIS 
 
 be one of tranquillity during this period. If the mind is excited or 
 irritated, it will send depressing messages throughout the body and 
 the process of digestion is retarded and disturbed. 
 
 Under such clean conditions the normal processes of digestion can 
 take place with a minimum amount of effort and energy being expended 
 by the tissues in their work, and the product after digestion is fit for 
 the blood stream to offer to the cells of the body the nourishment they 
 need to perform properly their respective functions. But the reverse 
 situation exists regarding the mouth. The food may be clean and pure 
 but the mouth unclean. 
 
 Decomposing Food Debris. — In discussing the harmful effects of 
 decomposing food in the mouth, the subject cannot be better presented 
 than by giving some of the thoughts of Dr. E. C. Kirk from a paper 
 read by him in Providence, R. I., October 16, 1900, and published in 
 the Dental Cosmos in May, 1901, entitled "Some Considerations 
 Relative to the Infant Mouth." 
 
 Regarding the artificial feeding of infants he refers to the training 
 of the nurse to sterilize the milk and feeding apparatus in order that 
 the milk shall be delivered to the child's stomach free from bacteria 
 "which when present in the food supply so alter its composition as to 
 reduce its nutritive value and, what is still more important, set up 
 decomposition processes within the alimentary tract of the infant 
 which are direct causes of irritation and disease to the infant organism." 
 
 Great care having been taken in preparing the food and in feeding, 
 no attention was paid to the film of milk left in the mouth after feeding. 
 It is apparent that if fresh milk is poured into a bottle that has con- 
 tained sour milk, infection of the fresh milk will immediately take 
 place. In the feeding process the sterile milk passing over the infected 
 surface caused by the residue of the last feeding at once infects the 
 milk. 
 
 Dr. Kirk says, "There can be but one result: fermentation of the 
 infected fluid begins in the stomach; putrefaction of the proteid ele- 
 ments may take place; quantities of gas are formed, distending the 
 walls of the stomach and intestines, causing pain and irritation, 
 further increased by the irritating effects of organic acids which are 
 end-products of this fermentative process. Digestion is interfered with 
 or arrested, the fermenting mass of food becomes a mechanical as 
 well as a toxic irritant; diarrhea sets in, the whole nutritional process is 
 interfered with and development is damaged in proportion to the 
 length and severity of the attack. 
 
 "The rational remedy for this state of affairs is clear when once the 
 conditions to be therapeutically met are understood. In the first 
 place, removal of the primal cause by thorough oral cleanliness and 
 sterilization in so far as that end may be obtainable. This may be 
 practically accomplished by wiping the mucous membrane with a 
 saturated solution of boric acid to which borax has been added in the 
 proportion of ten grains to the ounce, or with a very dilute solution 
 
THE ALIMENTARY TRACT 229 
 
 of phenol sodique, one-half dram to the ounce, applied on a cotton 
 swab or with a soft linen handkerchief wrapped around the finger 
 of the nurse." 
 
 Now apply the same principle to the growing child and to the adult. 
 The teeth of a child between the ages of six and twelve years will 
 present surfaces equal to twelve to sixteen square inches. In an adult 
 the surfaces will average about twenty-five square inches. This means 
 that if it were possible to peel the enamel off of each of the five sur- 
 faces of each tooth and place them side by side they would cover a 
 piece of glass three and one-half inches square in the case of the child, 
 and in that of the adult a piece about five inches square. This will 
 give a rough idea of the amount of surface presented in the mouth to 
 permit of the retention of a certain quantity of food that must decom- 
 pose unless it is removed. The more perfect the teeth regarding 
 form, occlusion and enamel surface, the more self-cleansing they are, 
 and proportionately, the amount of food so retained is comparatively 
 small. The mouths that present such ideal conditions are rare, espe- 
 cially among those who are born and live in the cities. Where the teeth 
 are irregular in shape and position, are decayed and broken down, the 
 amount of food that remains is considerable and the volume of decom- 
 posing material constantly being swept into the intestinal tract will 
 eventually breed illness. In a growing child such mouth conditions 
 are vicious. "Suppose," said a prominent educator in dentistry, 
 "that a prescription was given to a mother by a physician, to mix, 
 with each meal that the child ate, a half-spoonful of garbage. Would 
 she carry out such a prescription, and if she did and the child became 
 ill, would not the physician be liable for damages?" And yet in reality 
 that is what is taking place in the average mouth of the children in 
 our public schools and in the mouths of the great working classes. 
 This constant drain of poison into the intestinal tract in child life 
 causes an intestinal indigestion where bacterial products are absorbed 
 into the system and produce fevers, headaches, eye-strain, anemia, 
 malaise, constipation, and dizziness. Nature finally takes away the 
 child's appetite and forces it to bed until a good house-cleaning of the 
 body can be accomplished. 
 
 These poisons from the mouth are insidious and slow in action. 
 Many can and do withstand them for years, but as the constant drop- 
 ping of water will wear away the stone, so will the products of decom- 
 posing food in the mouth soon destroy good digestion and undermine 
 the system. 
 
 Vaughn and Novy, in their book entitled Cellular Toxins, say, 
 "The effect of a chemical compound upon the animal body depends 
 upon the conditions under which and the time during which it is admin- 
 istered. Thirty grains of quinine may be taken by a healthy man dur- 
 ing twenty-four hours without any appreciable ill-effect, yet few would 
 be willing to admit that the administration of this amount daily for 
 months would be wise or altogether free from injur\\ In the same 
 
230 DENTAL PROPHYLAXIS 
 
 manner the administration of a given quantity of a bacterial alkaloid 
 to a dog or a guinea-pig in a simple dose may do no harm, while the 
 daily production of the same substance in the intestine of a man and 
 its absorption, continued through weeks, and possibly years may be 
 of marked detriment to the health." 
 
 It must be borne in mind that the manifestation of sickness does 
 not come from the presence of bacteria, but from the poisons generated 
 by the bacteria. 
 
 ' Abbott in his book on The Principles of Bacteriology, quotes Roux 
 and Yersin who claim that the potencies of the poisons that have 
 been isolated from cultures of Bacillus diphtherise have been determined 
 by experiments upon animals, and it has been found that 0.4 milli- 
 gram is capable of killing eight guinea-pigs. Please remember that 
 four-tenths of a milligram represents but y-g-Q part of a grain. Aside 
 from the products of decocnposing food in unsanitary mouths we must 
 seriously consider how much of the bacterial poisons may be generated 
 in such mouths daily by the millions of microorganisms present, and 
 whether these poisons are not of sufficient quantity eventually to 
 weaken the organism and render the body susceptible to infection 
 from the pathological group of microorganisms. In the battle being 
 waged against tuberculosis, this feature will be given much impor- 
 tance, and the day is not far distant when some scientist will be able 
 to compute with a reasonable degree of accuracy how much bacterial 
 poison can be generated in twenty-four hours in a mouth containing 
 decayed teeth and food debris. 
 
 Bacterial Propagation. — In considering the products of decomposing 
 food with their detrimental action on the system, their action upon 
 the human mouth, than which there is no better breeding ground for 
 germ life, must also be considered. The mouth is an ideal incubator, 
 for here we find all of the essentials for the propagation and develop- 
 ment of these microorganisms. The right temperature, sufficient 
 moisture, air, darkness and a menu to choose from that would tempt 
 any member of this large family. Germ life is comparatively harmless 
 when robbed of a food supply, but give it a pabulum upon which to 
 feed, develop and multiply, and it becomes active and virulent. It 
 must be borne in mind that all mucus-lined tracts of the body have 
 their flora of microorganisms and that the individual must live among 
 them, that the few friendly ones are company, but that too many are 
 a crowd, and that in this crowd are our enemies who feed upon the 
 host if they but get a chance. 
 
 An unclean mouth means an increased number of bacteria, and 
 with increased numbers come increased dangers from infection. The 
 cavities of decayed teeth harbor millions of these mischief-makers, 
 as do also the food debris and calcareous deposits around the necks 
 of the teeth. They may enter the mouth in a very subdued state, 
 but under these favorable environments they soon multiply rapidly. 
 The usual order is to consider their activity and growth in unsani- 
 
THE ALIMENTARY TRACT 231 
 
 tary mouths, but this will be reversed and the medium upon which they 
 best are cultivated in the laboratories be first noted. The saprophytic 
 class are those which exist upon dead animal or vegetable matter. 
 The parasitic class prefers to gather its nourishment from the living 
 host. Many of both classes can live in either medium, as occasion 
 demands. 
 
 As the unorganized ferment of gastric or intestinal digestion has 
 the power of changing the food by rearranging its elements, usually 
 by a process of hydration, so do these microorganisms have the power 
 of breaking down tissue or decomposing food and liberating its ele- 
 ments in their search for carbon and nitrogen. The media chiefly 
 used in laboratories for cultures of microorganisms are bouillon with 
 agar-agar, gelatin, potato, sugar and blood serum. If these are kept 
 at the right temperature, at least to grow mixed cultures, the sapro- 
 phytic class is quite easily developed, for the extracts of beef, sugars 
 or starches form an attractive pabulum. Many of the parasitic variety 
 can also be grown in these substances, such as the t^'phoid bacillus, 
 anthrax and others, while the tubercle bacillus and the bacillus of 
 diphtheria are cultivated in the blood serum. These culture media 
 are all found in the average mouth, even to the blood serum. 
 
 When the teeth are decayed the amount of food retained in the 
 mouth is considerable, but especial attention should be called to con- 
 gested and bleeding gums. Here is an ideal medium for the propa- 
 gation of infectious germ life, and it is not only the cavities in the 
 teeth and the food debris, but also the pernicious condition of the gum 
 tissue in unsanitary mouths, especially in those of children, that is 
 of serious concern. The germs of tuberculosis or of diphtheria can 
 here find a pabulum for their propagation and development, and 
 undoubtedly the prevailing condition of the gingival borders of the 
 gums is one of the most important steps toward infection. The bleed- 
 ing and congested gums and the decomposing food is present, all that 
 is now necessary is the bacterium. 
 
 All observant practitioners will readily agree to the statement that 
 mouths that contain no congested areas on the gingival borders of 
 the gums are exceptions. The dark red surfaces will bleed upon the 
 slightest pressure, and in between the molars and bicuspids where 
 the food can lodge undisturbed in ill-kept mouths, even a slight suc- 
 tion will start a copious bleeding. It will be the privilege of the hygien- 
 ist to note in the treatment of each new patient how easily the gums 
 will bleed upon the slightest touch of instrument or porte polisher. The 
 oozing of serum and blood from these congested points is of equal 
 importance in the consideration of infectious diseases of children with 
 the decomposing of animal and vegetable matter found in the decayed 
 teeth or around their surfaces. To those who have thoroughly inves- 
 tigated the subject, the mouth is now conceded to be a most impor- 
 tant field for bacterial growth and systemic infection. 
 
232 DENTAL PROPHYLAXIS 
 
 Tuberculosis. — One of the greatest battles being waged in preventive 
 medicine is the fight against tuberculosis, and this fight can never be 
 won as long as the mouth conditions of the mass of people remain as 
 they are at present. 
 
 Scientific investigators are agreed that tubercular infection frequently 
 takes place through the tonsils and the intestinal tract. If this is true, 
 the bacilli must either be taken in with the food supply in sufficient 
 quantities to prove dangerous, or they must find lodgement in the 
 mouth in decayed teeth and congested gum surfaces. With unsanitary 
 or septic conditions existing in the buccal cavity, many bacteria in a 
 state of virulency are constantly drained over the tonsils and into the 
 stomach. Any physical depression that lowers the normal resistance 
 of the body might permit of the invasion of these pathogenic organisms. 
 
 The medical man must realize that the gingival borders of the gums 
 present an area eight times greater than that of the crypts of the 
 tonsils, and that in the average mouth the gums are congested and bleed 
 readily. This provides the ideal culture medium for the tubercle 
 bacilli. Add to this the lowered bodily resistance induced by the 
 absorption of the poisons generated by the immense numbers of 
 bacteria present in such mouths, and it makes a pathological combina- 
 tion that seriously hinders the medical profession from making any 
 further greater reduction in the mortality from this disease. 
 
 In our state sanitariums, where the tubercular patients are segre- 
 gated, the mouth conditions are deplorable. It is true that, with 
 plenty of fresh air, good food and rest, the body can and does neutralize 
 much of the poison. The resistive force is increased and the disease 
 pronounced arrested; the word cure is cautiously used. Could the 
 mouths of these patients be made sanitary at the beginning of the 
 treatment and rigid rules enforced regarding their daily care, a marked 
 benefit would surely be observed. When the mouth is clean and 
 wholesome the liability to this form of infection is greatlj' lessened . 
 
 Systemic Infection. — If syphilis and wounds of the surfaces of the 
 body are excluded there are but three ways, ordinarily, for bacteria to 
 gain entrance into the blood stream: (1) Through tooth passes, such 
 as root canals and diseased pericemental tissues; (2) through the tonsils 
 and (3) through the intestines. Infection through the tonsils or the 
 intestinal tract is dependent, in a great measure, upon mouth conditions. 
 
 In the consideration of the mouth as an avenue for systemic infection, 
 the attention must be centered upon the soft tissues: the gums, the 
 pericementum and the pulp, for these are the tissues chiefly involved in 
 permitting of the ingress of bacteria into the lymphatics. 
 
 Although there are other phases of dental pathology which may 
 produce a detrimental action, either locally or systemically, the follow- 
 ing three conditions are most prevalent and by far the most serious: 
 
 (1) Unsanitary mouths, with decayed teeth and decomposing food; 
 
 (2) diseased pericemental tissues; (3) devital and infected teeth. 
 The toxic influence of unclean mouths is especially noticeable in 
 
THE ALIMENTARY TRACT 233 
 
 children, frequently producing headache, malaise, dizziness, imperfect 
 vision, slight fevers, diarrhea, and a general condition of malnutrition. 
 And these minor ailments can only be considered as secondary to the 
 dangers of systemic infections which are frequently produced by the 
 actual penetration of the bacteria through the mucous membrane of 
 the tonsils, the pharynx and the intestines. 
 
 The next factor is that of the inflamed and diseased tissues support- 
 ing the teeth. For quite a number of years dental pathologists have 
 repeatedly called attention to the dangers of these pericemental infec- 
 tions as a probable cause of systemic disease, and since Professor Xoyes' 
 definite demonstration of the network of l^-mphatic vessels in the peri- 
 cemental tissues, even to the extreme borders of the gingiva, there can 
 be no doubt of the ingress of bacteria through these vessels into the 
 blood stream, and their subsequent localization in some of the other 
 tissues of the body. There is much scientific and clinical evidence to 
 prove that pyorrhea alveolaris is a cause of systemic infection which 
 may be produced in three ways : (1) By the constant exudation of pus 
 in the mouth and thence into the digestive tract; (2) the absorption, 
 by the lymphatics, of the bacteria and their toxins present in the 
 deeper areas of the infected tissues, (3) by the pumping action of loose 
 teeth in their sockets during mastication, forcing bacteria and their 
 toxins into the capillaries and thus into the blood stream itself. 
 
 The third phase for consideration is proving even more serious than 
 the first two, for the a;-ray has revealed to us infected areas within the 
 bone tissue at the apices of the roots of the teeth which we have hereto- 
 fore never suspected. These apical infections are found only upon teeth 
 with devital pulps, and have remained so long undiscovered because 
 the action of the streptococcus viridans is so subtle and usually produces 
 no local soreness, pain, inflammation or pus. 
 
 Our research workers have clearly demonstrated that, under certain 
 conditions, the streptococcus viridans in the apical infection becomes 
 aggressive and migrates, developing a selective action which varies in 
 affinity for different tissues of the body, and the work of Billings, 
 Rosenow, Hartzell, Thoma and others has proved scientifically that 
 they are the cause of many of the most serious systemic infections, 
 especially those involving the hearty the kidneys and the joints. 
 
 The death of the pulp is due chiefly to dental caries and dental caries 
 is so exceedingly common that it is difficult to find two school children 
 out of a hundred with perfectly sound teeth, and even in early child- 
 hood our school children average seven cavities per child. Consequently 
 there are few young people who escape a pulp involvement due to the 
 penetration of the bacteria through the tooth structure, destroying 
 this delicate and sensitive tissue. Pulpless teeth are, therefore, so 
 prevalent that it is the exception for an adult over thirty years of age 
 to present a mouth without one or more devital teeth which already 
 have, or which may develop an apical infection. The work of the 
 dental hygienist will be the most important step in the elimination of 
 
234 ' DENTAL PROPHYLAXIS 
 
 systemic infection from devital and infected teeth, for her field of 
 service incl*udes the prevention of dental caries and subsequent pulp 
 involvement. 
 
 THE PRINCIPLES OF DENTAL PROPHYLAXIS. 
 
 The initial cause of nearly all the pathological or disease con- 
 ditions of the tissues of the mouth is the combination of microorgan- 
 isms and food debris. Bacteria alone or food debris alone would be 
 quite harmless in the mouth. Nearly all germ life, in order to become 
 virulent, or its presence dangerous or even objectionable, must have 
 a pabulum upon which to thrive. It is therefore dependent upon 
 some attractive food supply in order to reproduce and multiply. It 
 is known that foods will "spoil" if allowed to remain in a warm tem- 
 perature for any length of time, and that in order to prevent this action 
 the germs are killed by boiling or heating the food, tightly sealing it 
 from the air in cans or jars that have just previously been boiled or 
 have had boiling water poured into them, and allowing them to stand 
 long enough for their surface to become sterilized. 
 
 Food may also be placed where it will be kept cold, as in an ice-box, 
 where the presence of the ice will so reduce the temperature that the 
 organisms are rendered sluggish and inert. 
 
 For years, many efl^orts have been made to find some drug or chemical 
 that could be used in the mouth to kill all bacteria and thus make the 
 mouth sterile, or at least to render them inert. The futility of even 
 hoping for a sterile condition of the mouth has long since been demon- 
 strated. It is impossible to sterilize the human mouth, and even if 
 it were possible, such a condition could be maintained but a very 
 short time. Therefore, if it is impossible to keep the mouth free from 
 bacterial life, and as the combination of food debris and bacteria is 
 the chief cause of dental diseases, is there not some way in which the 
 food debris can be thoroughly removed? It is upon this thought that 
 the principles of prophylaxis are based. 
 
 Dental prophylaxis is that scientific effort, either operative or thera- 
 peutic, which tends to prevent diseases of the teeth and their surrounding 
 tissues. Correcting and restoring to normal function all abnormal 
 or pathological conditions of the teeth, and maintaining that normal 
 condition, is a prophylactic procedure. This includes practically all 
 the operations in dentistry. The mere filling of a tooth cannot be 
 termed prophylactic unless the operation is performed with a knowl- 
 edge and skill that tends to prevent future decay at that point and 
 that will restore the surface of the tooth to normal contour and normal 
 function. Crowns and bridges, root-fillings, approximal fillings with 
 proper contact points, and smooth, flush margins, the correction of 
 malocclusion, the removal of all calcareous deposits, polishing, the 
 instruction in the home care of the mouth, may all be made prophylactic 
 if properly done. 
 
THE PRINCIPLES OF DENTAL PROPHYLAXIS 235 
 
 The Service of the Dental Hygienist. — The dental hygienist must 
 regard herself as the channel through which the knowledge of preventioji 
 that the dental profession has acquired is to be disseminated. The 
 greatest service she can perform is the slow and painstaking education 
 of the public in mouth hygiene and allied branches of general hygiene. 
 The education and training of dental hygienists does not aim to produce 
 mechanical operators. An unlimited field of educational and preven- 
 tive service is open to the dental hygienist who regards herself primarily 
 as a hygienist and educator, and secondarily as a prophylactic operator. 
 
 The dental prophylactic operation of the dental hygienist is chiefly 
 concerned with the exposed surfaces of the teeth, the necks of the teeth 
 directly under the free margin of the gums, and the gum tissue itself. 
 It must always be borne in mind that the aim of the dental hygienist 
 is to secure extreme cleanliness of the mouth in an effort to starve 
 bacteria and render them inert, and it is to this end that the cooperation 
 of the patient must be secured. 
 
 It will be found that the average mouth presents an unsanitary 
 condition that encourages the propagation of millions of microorgan- 
 isms, and is a menace to the health of the patient. It is the duty of 
 the hygienist to be kind in her criticism to such a patient, for in most 
 cases the individual is not responsible for this deplorable condition. 
 The ignorance of the patient regarding the proper care of the mouth, 
 and the careless operative work of many dentists is usually responsible. 
 It will be found that the great majority of patients are eager to learn 
 the correct care of the mouth, and follow instruction faithfully when 
 they are once enlightened. After these unsanitary mouths are seen to 
 develop into healthy ones under prophylactic skill and instruction, 
 the dental hygienist will realize that the service she may render to 
 humanity is a very important one. 
 
 The procedure which should be adopted with a new patient may be 
 divided into three parts: (1) The examination of the mouth; (2) the 
 dental prophylactic treatment, and (3) the instruction of the patient 
 in the home care of the mouth. 
 
 Examination of Adult Mouths. — The general condition of the teeth 
 should first be noted. It will be found that the enamel surfaces are 
 without luster and are covered with a pasty colorless film. The necks 
 of the teeth are stained; calcareous deposits are seen on the lingual 
 surfaces of the lower incisors and the buccal surfaces of the upper 
 molars. All of these conditions can be corrected by the hygienist, 
 but she is dependent upon the aid of the dentist to remedy the unsani- 
 tary construction of fillings, crowns and bridges. At this point all 
 conditions of the teeth which the hygienist believes require the atten- 
 tion and cooperation of the dentist should be recorded upon a chart. 
 This will include any decayed surfaces which she may note, as well as 
 cough fillings or margins of fillings that are extended beyond the tooth 
 surface and retain food debris. It will be necessary for the dentist to 
 carefully grind and polish all such fillings in order that the desired 
 
236 DENTAL PROPHYLAXIS 
 
 results may be obtained from the prophylactic treatments. A record 
 should be made of fillings in the approximal surfaces if there is sufficient 
 space to permit of food packing down between the teeth to injure or 
 inflame the gum tissue. New fillings with proper contact points are 
 frequently needed to remedy this condition. 
 
 If there are gold crowns or banded crowns that do not fit tightly to 
 the tooth or root and that will permit the end of the explorer to pass 
 between the root and the band or crown, it may be taken for granted 
 that such a space is filled with decomposing food and is an ideal haven 
 for bacteria. The odor arising from such crowns after their removal 
 makes one realize the necessity for tight-fitting bands and flush joint 
 operations. Hygienists will come to loathe the average gold crown and 
 will use their influence against their insertion. Many of them are 
 sources of systemic infection and nearly all will destroy the pericemen- 
 tum around the tooth, and result in the eventual loss of the tooth. 
 Such dentistry is a serious menace to public health and has undoubtedly 
 been the cause of many severe illnesses that have resulted even in death. 
 If an ill-fitting gold crown is placed over a tooth containing a live pulp, 
 it is but a question of time when the bacteria and the poisons generated 
 by the decomposing process of the food debris lodging in the space 
 under the crown where the cement has disintegrated and washed away, 
 will penetrate the dentin and infect and destroy the pulp. Apical 
 infections from teeth carrying gold crowns are common. It would be 
 far better for the patient who could not afford to have the work done 
 properly, to have such teeth extracted. Ill-fitting bridges so con- 
 structed that it is impossible to properly remove the food with the 
 brush and washes will badly hamper work for mouth hygiene. 
 
 It is not necessary to know the details of the work of construction 
 of crowns or bridges or of fillings, but it is necessary to know what 
 constitutes good dentistry and sanitary construction. A small pimple 
 on the gum, termed by the layman gum-boil, is in reality a fistula 
 opening from an alveolar abscess. The attention of the dentist should 
 be called to these fistulse. 
 
 The gum tissue should now be examined. The term congested gums 
 is applied to enlarged capillaries, engorged with blood and having 
 a sluggish circulation. External irritation from lack of use and func- 
 tion in the mastication of proper foods is usually the cause for this 
 congestion. The deep red color is due chiefly to the sluggish flow of 
 blood laden with carbon dioxid. Perfect metabolism is not taking 
 place in the cells of this tissue and the waste products are not being 
 carried away with sufficient rapidity. Any local irritant on the sur- 
 face or border of the gums will produce this congestion, and the mouths 
 are rare that do not contain a number of congested surfaces. 
 
 In the mouths of children this condition is also produced by the sharp 
 edges of decayed or broken-down teeth, temporary and permanent, 
 and sufficient blood and serum ooze from these blood-engorged areas 
 to form an excellent culture medium for pathogenic bacteria. 
 
THE PRINCIPLES OF DENTAL PROPHYLAXIS 237 
 
 Every organism has its vulnerable or vital area which if sufficiently 
 injured will eventually cause its death. The tooth is no exception to 
 this rule. Its vulnerable point is the border of the peridental mem- 
 brane directly beneath the gingival margin of the gum around the 
 neck of the tooth, and this must be carefully safeguarded. This 
 membrane forms the most vital part of the foundational structure of 
 the tooth. Upon its health and resistance depend the function and 
 life of the whole tooth. If it becomes injured, irritated or infected at 
 its border and the lesion or infection is neglected, the membrane dies 
 at this point, and in dying it causes the death and absorption of a 
 similar area of the alveolar process which was in apposition to the 
 affected membrane. This means a space or so-called pocket under 
 the margin of the gum where food debris can find lodgement and 
 where bacteria, well out of the currents of the saliva which flow freely 
 around the teeth, can hold a tenable position. 
 
 The rapidity of the progress of death and absorption is dependent 
 upon the resistant force contained within the cells of the membrane 
 and upon the virulency of the attacking microorganisms. In child- 
 hood this membrane is thick and highly vascular and can resist almost 
 any invasion of bacteria even when wounded, if not too seriously. 
 In adult life it gradually becomes thinner, its blood supply is lessened, 
 and as age advances the cells lose the high resistant force that they 
 possessed in youth; and if the person is in what we call a run-down 
 condition physically, from improper feeding of the body, unclean envi- 
 ronments, harmful habits, excesses, or from any cause that will disturb 
 the proper metabolism of the tissue by disturbing the nutritive or the 
 nervous systems, the resistant force is still further lowered and the peri- 
 dental membrane and the surrounding supporting tissues of the tooth 
 become easy prey to the invading bacterial host. Although it will 
 be possible to raise the resistance of this membrane again by prophy- 
 lactic treatment and training of the patient in the proper methods of 
 artificial stimulation, it can readily be seen that it is far more desirable 
 to prevent the original disturbance at the neck of the tooth and save 
 the patient the surgical treatment necessary in the hands of the den- 
 tist in order to get control of this much-dreaded and serious condition 
 of absorption and infection of the supporting tissues of the root of 
 the tooth. It must always be borne in mind that the most important 
 part of the tooth is the root and any irritation of the gingival border 
 of the gum, especially in adult life, is a menace to that tooth which is 
 in closest proximity to the point of irritation. 
 
 Before operating in the mouth of a new patient the hygienist should 
 make sure that the patient has removed all of the food debris from the 
 teeth that it is possible to remove with the tooth-brush, floss silk and 
 mouth wash. It is never the duty of the hygienist to operate in a 
 mouth that contains food debris. For her own self-respect and for 
 the dignity of her calling, she should make it an absolute rule never to 
 Start an operation of prophylaxis when the patient has failed to clean 
 
238 DENTAL PROPHYLAXIS 
 
 his teeth of food debris before coming to her department. It is never 
 her duty to remove food debris excepting the small quantities that 
 roughened surfaces have made it impossible for the patient to remove. 
 These cases will require some diplomacy on her part, for she must realize 
 that the patient has not intentionally insulted her by presenting such 
 an unclean mouth. It is merely that he has never been taught better. 
 For years dentists h^ve consented without remonstrance to operate 
 in the mouths from which the food has not been removed from between 
 the teeth, and it will be one of the missions of the hygienist toward the 
 uplift of the dental profession to teach patients that they must not 
 present themselves for any dental service whatsoever unless their 
 teeth have been thoroughly brushed and flossed. She should be kind 
 and considerate in the handling of such cases, and explain to the 
 patient that there is danger of infecting the gum tissues if the instru- 
 ments are used around the necks of the teeth where there is decompos- 
 ing food, and that, in order to obviate any such danger it will be neces- 
 sary for him to step to the bowl and thoroughly brush and rinse his 
 mouth before the operation. 
 
 A stock of tooth-brushes should be a part of the equipment of every 
 dental office and should be charged up against the expense of dental 
 supplies. The cost of the brushes if bought in quantities, amounts to 
 but little when we consider their absolute necessity for instruction, and 
 their use when needed under these conditions. 
 
 Patients soon learn the rules of an office and in a comparatively 
 short time it will be a rare thing to be obliged to send a patient to the 
 bowl to brush his teeth before the prophylactic treatment can be 
 started. Much of the soreness of the gums after these treatments in 
 the mouths of new patients is due to crowding some of this infected 
 material under the gum margin with the instrument, and it follows 
 that the cleaner the necks of the teeth are before instrumentation, the 
 quicker will be the recovery of the congested gums after treatment. 
 
 The Prophylactic Treatment. — ^In considering the practical work of 
 dental prophylaxis the operation in the mouth of the adult will be first 
 described. With a pledget of cotton soaked with peroxide of hydrogen, 
 the necks of the teeth and also the approximal surfaces should be bath- 
 ed. The boiling of the peroxide will mechanically aid in loosening 
 minute particles of food debris. After rinsing the mouth with warm 
 water the teeth should be thoroughly sprayed on all their surfaces with 
 compressed air and an atomizer. The air pressure should be at least 
 twenty-five pounds, so that it may have enough force to blow the spray 
 with sufficient force between the teeth to aid in this. mechanical cleans- 
 ing. It makes no difference what liquid is used in the atomizer if it is 
 harmless and has a pleasant taste. 
 
 Surfaces of the Teeth.— It must be remembered that in this work 
 hygienists are not to cross the border-line into surgery. The laws in 
 all states prohibit surgical or medicinal treatment by any but graduate 
 practitioners, Therefore the entire efforts of the hygienist are to be 
 
THE PRINCIPLES OF DENTAL PROPHYLAXIS 239 
 
 confined to the exposed surfaces of the teeth and the area directly under 
 the free margin of the gum. 
 
 The base of the crown of each tooth has four lines or boundaries. 
 This is the entire field for the use of the instruments unless a root sur- 
 face is exposed. It can be readily appreciated what a slow and pains- 
 taking piece of work it is to go over carefully each of these surfaces 
 and remove all of the deposits of tartar. In the first treatments of 
 neglected mouths the deposits are likely to be large and are usually 
 found on all the surfaces at the necks of the teeth. It is impossible 
 to remove all of these deposits at one sitting without subjecting the 
 patient to an unnecessary strain. The large deposits may be broken 
 down and scaled off and many of the smaller nodules can be removed, 
 but it is quite impossible to be really thorough in the first treatment. 
 Again, it is unwise to subject patients to a too strenuous session, for 
 if they are timid, they are apt to become discouraged by the long and 
 tedious sitting. It is far better to arrange two sittings of an hour and 
 a quarter to an hour and a half each than one of two hours and a half. 
 If the appointment is made for two hours, the balance of the time may 
 be spent in polishing and in instruction of the home care of the mouth. 
 
 The subject of calcareous deposits has been so thoroughly covered 
 by Dr. Kirk, that it is unnecessary to go into it very deeply, but 
 attention should be called to the irritating action they display in 
 their porousness in absorbing liquefied debris, therefore forming an 
 excellent retainer for bacteria. It is absolutely essential for the health 
 of the gums and the roots of the teeth that all such deposits be removed 
 at frequent periods! The time maj^ come when people may be induced 
 to eat the proper foods in proper quantities, then this deposit will be 
 greatly lessened, but until this goal of good sense is gradually reached, 
 artificial care of the mouth by prophylactic treatments will have to 
 be resorted to. 
 
 Much of the evil from the forming of serumal deposits in the subgin- 
 gival space can be obviated by eliminating the congested condition of 
 the capillary circulation found in the gum tissue of the mouth of the 
 average adult. But the mouths are indeed rare in which no new 
 deposits can be found under the gingival border after a period of two 
 months. 
 
 System for Instrumentation. — In order to perform a prophylactic 
 operation intelligently one must work by system, and the instru- 
 mentation as well as the polishing must have a definite starting-point 
 in the mouth and should always proceed in the same given direction 
 over the surfaces of the teeth in the case of every patient. This is 
 necessary for thoroughness and also in case of interruption, for if one 
 will but note mentally the last tooth being worked upon before leaving 
 the chair, the chain will remain unbroken upon resuming. It matters 
 little what system is finally adopted, but the one here suggested is 
 advocated because it has proved very practical, 
 
240 DENTAL PROPHYLAXIS 
 
 Lower Jaw. — Beginning on the lingual surface of the right lower last 
 molar at the gingival line, distolingual angle, instrumentation proceeds 
 mesially until the lingual border of the left lower central is reached. 
 The same direction is now followed but the line of operation becomes 
 distal on the left side, still keeping on the lingual surface until the 
 distolingual angle of the left lower last molar is reached. 
 
 Again starting on the distobuccal angle of the left lower last molar, 
 the instrumentation proceeds buccally and mesially until the left 
 lateral is reached, where from this point the operation continues on 
 the same surface to the distobuccal angle of the right lower last molar. 
 
 8 FINISH 1 START 
 
 ■,/P): 2 3 ((%^- 
 
 The following cuts are taken from Plate VI of the American System 
 of Dentistry, and will, by the dotted lines and arrows, better illus- 
 trate the directions followed as just described. Fig. 153 represents 
 the teeth of the lower jaw with crowns excised at the gingival border. 
 These cuts will illustrate the lines to be followed and field of operation 
 to be covered by the dental hygienist with the instruments. 
 
 As shown by the dotted lines in Fig. 153, this first use of the instru- 
 ments on the lower teeth covers only the lingual and buccal surfaces. 
 By working along on the same surfaces of the teeth on the same jaw, 
 considerable time may be saved by not having to change instru- 
 ments every moment or two, as one instrument frequently will adapt 
 itself to eight teeth before it will be found necessary to change. 
 
 After the deposits have been removed from the lingual and buccal 
 surfaces, attention is given to the distal surfaces. Once more begin- 
 ning on the distal surface of the right lower third molar, the distal 
 
THE PRINCIPLED OF DENTAL PROPHYLAXIS 
 
 241 
 
 surface of the right lower molars, bicuspids and cuspid are carefully 
 scraped. Next the distal surfaces of the left lower cuspid, bicuspids 
 and molars, as illustrated in Fig. 154. One instrument will usually 
 adapt itself to these surfaces. Next the mesial surfaces of the right 
 
 4 -^-4 
 
 -3 
 
 3 -.5)- 
 
 Fig. 154 
 
 lower molars, bicuspids and cuspid, then the mesial surfaces of the left 
 lower cuspid, bicuspids and molars. These surfaces, too, ma}- usually 
 be covered with one instrument. Lastly, the approximal surfaces of 
 the lower incisors, which may be covered with two instruments (Fig. 
 155). 
 
 4 
 
 R 
 
 
 L 
 
 Fig. 155 
 
 Upper Jaw.— On the upper jaw at the point corresponding with that 
 where work was first started on the lower jaw, the distolingual angle 
 of the right upper third molar, the lingual surfaces of the superior set 
 16 
 
242 
 
 DENTAL PROPHYLAXIS 
 
 are cleaned of all calcareous deposits, working mesially until the left 
 central is reached, then distally to the left third molar. Again start- 
 
 
 ing at the distobuccal angle of the left upper third molar the buccal 
 surfaces are gone over, working mesially to the right central then 
 
 Fig. 157 
 
 distally to the right third molar (Fig. 156). Now beginning at the 
 right third molar, the distal surfaces of the right molars, bicuspids and 
 
THE PRINCIPLES OF DENTAL PROPHYLAXIS 
 
 243 
 
 cuspids are scraped. Next the distal surfaces of the left cuspid, bicus- 
 pids and molars (Fig. 157). In the same order the mesial surfaces 
 are gone over, leaving the approximal surfaces of laterals and centrals 
 until the last (Fig. 158). 
 
 If this briefly outlined system is followed there will be but little 
 chance that the deposits may escape the play of the instruments. 
 
 There is nothing that instils a greater confidence in the operator, 
 in the mind of the patient, than the gentle touch of his hand and the 
 instruments. The very first requisite is to try to develop a firm yet 
 gentle touch. In handling the lips, the cheek, the tongue, the motions 
 should be slow enough and deliberate enough to insure gentleness. 
 Such precautions in self-training soon improve the technic in hand- 
 ling the instruments, and it is much the better fault to be over-gentle 
 and a little less thorough to begin with than to be heavy-handed, 
 
 5 6 , 
 
 #^ "Is 
 
 
 
 Fig. 158 
 
 rough and overstrenuous with the instnmients. There is no better 
 application of the golden rule than in dentistry, and the operator 
 who masters a fine sense of touch and constantly keeps in mind a 
 sympathetic consideration for his patient, has conquered much that 
 is productive of success. 
 
 One of the most perplexing and yet one of the most essential things 
 to master at the start is the proper handling and use of the mouth 
 mirror. The mouth mirror is especially essential in operating on the 
 lingual surfaces of the upper teeth and can also be used to advantage 
 in holding the tongue away from the lingual surfaces of the lower 
 teeth. 
 
 As the motion reflfected .in the mirror is reversed from that of direct 
 observation, it is puzzling at first to place the instrument properly, 
 but a little practice will soon obviate the difficulty. The Dunn cheek 
 
244 
 
 DENTAL PROPHYLAXIS 
 
 distender is used to expose the buccal surfaces of the teeth, both in 
 instrumentation and poHshing, and its use adds much to ease of vision 
 and access to these surfaces. 
 
 The Four Motions. — In instrumentation, as well as in polishing, there 
 are four distinct motions. These may be termed digital, wrist, rotary 
 or forearm and rigid arm. In acquiring these movements the fulcrum 
 point of the hand in relation to the hold of the instrument is the deter- 
 mining factor. If the digital motion is to be used, the instrument 
 or polisher is grasped as illustrated in Fig. 159. The end of the right 
 thumb is the fulcrum-point or rest. This position permits of a perfect 
 control of the instrument and allows a play of the instrument in 
 either a push or a pull stroke. This motion is used particularly on 
 the teeth of the upper jaw. It might be well to state here that no 
 instrument should be used in the mouth unless the hand is first braced 
 
 Fig. 159 
 
 by a suitable rest for one or more of the fingers of the hand holding 
 the instrument. No free-hand motion should be used. Such motions 
 would be almost sure to invite a slip of the instrument and result in 
 laceration of the gum tissue. The wrist motion is acquired by holding 
 the instrument as illustrated in Fig. 160, using the end of the second 
 or third fingers as a fulcrum. This motion may be used in various 
 parts of the mouth, especially on the lingual surfaces of the molars 
 and bicuspids, but it is not as effective for general use as the forearm 
 or rotary movements. The forearm or rotary motion is used on both 
 the upper and lower jaws and usually the end of the third finger 
 serves as a fulcrum, although that of the second finger can sometimes 
 be used. This motion is produced by holding the muscles quite rigid, 
 permitting the radius to rotate around the ulna bone in a limited area. 
 After a little practice this motion permits of a rapidity of work with the 
 
THE PRINCIPLE,^ OP DENTAL PROPHYLAXIS 
 
 245 
 
 instrument under perfect control, and to master this stroke is to master 
 much of the technic of instrumentation and polishing. 
 
 Fig. 160 
 
 Fig. 161 illustrates the position of the hand when using the rotary 
 motion. 
 
 Fig. 161 
 
 The rigid-arm motion is used for polishing nearly all of the labial 
 and buccal surfaces of the teeth, both upper and lower, and for the 
 lingual surfaces of the molars and bicuspids. The rest is usually found 
 
246 
 
 DENTAL PROPHYLAXIS 
 
 by using the side of the second joint of the right thumb on the chin or 
 the second joint of the third or fourth finger as ihustrated in Fig. 162. 
 
 The muscles of the whole arm are made fairlj- tense and the arm is 
 made to travel forward and backward in a short, limited area. All 
 of these motions should be practised over and over again on manikins 
 before being tried in the mouth. They are not easy to master and the 
 muscles must be trained by repeated practice. 
 
 In the removal of tartar around the necks of the teeth, there are 
 two strokes that may be utilized, a push stroke and a pull stroke. 
 Which to use is determined in a great measure upon the quantity or 
 bulk of the deposit and also upon the tenacity with which it may cling 
 to the tooth surface. In scaling off pieces of hard deposits, large or 
 small, the draw or pull stroke will be found most effective. The instru- 
 ment is carefully carried a little below the gingival border of the gum 
 and hooked securely over the shoulder of the deposit. Then with the 
 
 hand properly braced, the instrument is firmly drawn toward the masti- 
 cating surface or cutting edge of the tooth — a second digital motion 
 (Fig. 162). When the deposits are small and fairly soft, a short, 
 pushing stroke will be more effective. 
 
 Instraments. — Before the handling of the instruments is described 
 in detail a set of scalers will be considered that should be sufficient 
 for the beginner for all prophylactic work upon the necks and crowns 
 of the teeth. These include eleven instruments and may be described 
 as follows : 
 
 Fig. 163. The two small curved instruments with the spoon-like 
 ends are known as Nos 17 and 18 of the set of Darby-Perry excava- 
 tors. They are curved in opposite directions to each other and are 
 paired as rights and lefts. Dr. C. W. Strang, of Bridgeport, Ct., 
 suggested their use. Nos. 5 and 6 belong to the D. D. Smith set and 
 are made by J. W. Ivory, of Philadelphia. Fig. 164, Nos. 13 and 14, 
 
Ta^ PtttNClPLMS 6P DENTAL PROPHYLAXIS ^47 
 
 6 IS 
 
 Fig. 163 
 
 17 
 
 Fio. 164 
 
248 
 
 DENTAL PROPHYLAXIS 
 
 were designed by Dr. E. S. Gaylord, of New Haven, Ct., and are a 
 part of the Smith set, and are also made by J. W. Ivory, Nos. 3 
 and 4 are from the Harlan set of scalers made by the S. S. White 
 Company. 
 
 Fig. 165 illustrates the S. S. White scalers Nos. 33 and 34 and No. 3 
 sickle-sha,ped, which are all used for the removal of heavy deposits by 
 the pull or digital stroke. 
 
 The use of No. 3 sickle-shaped, and Nos. 33 and 34 is especially 
 indicated in the first treatment of mouths where the deposits have 
 accumulated for some time. For subsequent treatments the smaller 
 instruments mentioned should meet the requirements of the dental 
 
 Fig. 165 
 
 hygienist. At this point it must be distinctly understood that the 
 cleaning of teeth bears the same relationship to dental prophylaxis 
 as plowing does to agriculture. The plowing is essential before the 
 science of agriculture can be applied. The removal of the heavy 
 deposits, large accretions and accumulations of stains and plaques is 
 essential before the real science of prevention can be applied. A true 
 prophylactic treatment must be designed to aid in the prevention, not 
 only of dental caries, but of any of the departures from the normal 
 of the supporting tissues of the teeth. It must constitute, then, the 
 painstaking, frequent and systematic removal from the exposed 
 surfaces of every tooth the granular deposits, the accretions and 
 incipient plaques by instruments and hand polishers. 
 
INSTRUMENT A TION 
 
 249 
 
 INSTRUMENTATION. 
 
 Lower Jaw. — Assuming that the deposits are not unusual in quantity 
 and are reasonably easy to remove, the adaptation of these instru- 
 ments will be described, proceeding as in Fig. l.'jo. 
 
 Starting at the distolingual angle of the right lower last molar. 
 No, 18 of the Darby-Perry excavators is selected and held at the angle 
 shown in Fig. 166. The stroke used is a short downward push, and 
 a wrist motion is used with the blade held at nearly a right angle with 
 the tooth. On the downward stroke, the back of the blade with its 
 smooth, blunt surface will strike the gingival border of the gum and 
 
 Fig. 166 
 
 prevent the cutting edge of the instrument from traveling far enough 
 to injure the subgingival tissues. This short stroke is rapidly repeated, 
 the operator making a wave-like motion of the instrument, gradually 
 moving it forward, mesially, on the lingual surface of the molar until 
 the mesiolingual angle is turned, and using the mouth mirror with 
 the left hand to keep the tongue out of the way. The instrument is 
 now transferred to the next molar and the operation is repeated. This 
 is continued with the same instrument until the left lower central is 
 reached, from No. 1 to No. 2 in Fig. 153. The mate to this instrument, 
 No. 17, is now substituted and the operator, starting on the lingual 
 surface of the left central, Fig. 167, and using a rotary stroke, continues 
 until the distolingual angle of the left lower last molar is reached, 
 
250. 
 
 bmfAL PROPHYLAXIS 
 
 Fig. 168 or from No. 3 to No. 4 in Fig. 153. These small instruments 
 greatly magnify the sense of touch, so that each small deposit is readily 
 felt, whereas a larger instrument might pass it by. 
 
 Fig. 167 
 
 Fig. 168 
 
INSTRUMENTA TION 
 
 251 
 
 Fig. 169 
 
 
 ■ 
 
 l^^jJCX 
 
 ^^ 
 
 
 
 
 ft 
 
 K^'IHf^^iJ^I^^^^^^^^^^I 
 
 f 
 
 Fig. 170 
 
252 
 
 DENTAL PROPHYLAXIS 
 
 Again starting at the distobuccal angle of the left last molar with 
 instrument No. 18, Fig. 169, this short, pushing stroke with a wrist 
 motion is used until the left lateral is reached. From No. 5 to No. 6 
 in Fig. 153. Although the same instrument can be used effectively 
 on the labial surfaces of the incisors, it will be found advantageous 
 to change for its mate, No. 17, and, leaning slightly in front of the 
 patient, brace the hand by the third finger on the masticating surface 
 of the first bicuspid (Fig. 170), using a wrist motion which permits 
 of a careful handling of the festoons of the gums of the lower incisors. 
 After the labial surface of the left lateral is finished, the hand is moved 
 
 Fig. 171 
 
 forward to engage the next tooth. At the right cuspid the rotary stroke 
 is now adopted and continued to the last molar. Fig. 171 or from No. 
 7 to No. 8 in Fig. 153. The finger rests for the work just described are 
 found on the masticating surfaces of the bicuspids or on the cutting 
 edge of the cuspid or incisors. 
 
 The base of each tooth has four lines. Two of these lines have now 
 been covered, and there remains the approximal surfaces or the distal 
 and mesial lines. No. 13 is an instrument with the end bent at an 
 angle of forty-five degrees, having a long blade with a file-cut surface, 
 the numerous small blades of which are very effective in removing 
 
INSTRUMENT A TION 
 
 253 
 
 the small deposits. This instrument should be used chiefly with 
 a pull stroke, starting at No. 1, in Fig. 154, which is the distal sur- 
 
 FiG. 172 
 
 Fig. 173 
 
 face of the right lower last molar, as shown in Fig. 172. The distal 
 surface of the last molar being free, the blade is carefully passed 
 
254 
 
 DENTAL PROPHYLAXIS 
 
 down under the gum line until the sense of touch determines the bot- 
 tom of the subgingival space. The blade is then brought tight against 
 the tooth surface and pulled upward. An eighth to a quarter of an 
 inch play of the blade is sufficient to dislodge the deposits. This stroke 
 is rapidly repeated across the back of the tooth. In adapting this 
 instrument to the distal surface of the second molar the blade is inserted 
 sidewise from the buccal surface (Fig. 173), and with a short push-and- 
 pull stroke the instrument is worked between the teeth in order to 
 cover the entire distal line. If the teeth are so shaped and are so 
 close together that they will not permit the blade to pass between them, 
 then the instrument should be inserted also from the lingual surface, 
 and in this way that part of the distal line that was inaccessible from 
 
 Fig. 174 
 
 the buccal surface is covered. With the same instrument the distal sur- 
 faces of the teeth may be scaled to the incisors, or from No. 1 to No. 2, 
 in Fig. 154. Again, with the same instrument, the operator should start 
 on the distal surface of the left cuspid, and entering from the buccal 
 side, proceed on to the last molar, or from No. 3 to No. 4, in Fig. 154. 
 The procedure for the mesial surfaces is the same as described for the 
 distal, except that the instrument used is No. 14, and one position is 
 illustrated as in Fig. 174. Both push and pull strokes are employed. 
 The lower incisors are scaled on their approximal surfaces by the 
 bayonet-shaped Smith scalers, Nos. 5 and 6, from No. 5 to No. 6 of 
 Fig. 155, which shows this area. Fig. 175 illustrates the adaptation of 
 these instruments. 
 
INSTRUMENTATION 
 
 255 
 
 Upper Jaw. — On the upper jaw, at the right distolingual angle of the 
 last molar, instrument No." 17 is placed at nearly a right angle with the 
 tooth and, with the hand braced on the top of the left lower lateral 
 and cuspid teeth, using the third finger as fulcrum (Fig. 176), a wrist 
 
 Fig. 175 
 
 and digital motion is employed, the instrument being made to travel 
 forward with a short up-and-down, push-and-pull stroke combined, 
 perhaps better described as a waving stroke. The fulcrum-point is 
 maintained, the instrument being drawn in or shortened as the inci- 
 sors are approached. When the left central is reached (Fig. 156), 
 instrument No. 18 is substituted, the second finger used as a fulcrum 
 
 Fig. 176 
 
 on the cutting edge of the right upper cuspid (Fig. 177) and the lingual 
 surfaces of the upper teeth of the left side are gone over with a wrist 
 and digital motion. This fulcrum-point is maintained and the instru- 
 ment advanced in length with the thumb and first finger (Fig. 178). 
 
256 
 
 DENTAL PROPHYLAXIS 
 
 Again starting at the distobuccal angle of the left upper third molar, 
 the third finger is placed slightly back of the cutting edge of the right 
 upper lateral and central while the second finger rests on the cutting 
 edge of the left upper central (Fig. 179) . This position can be held until 
 the left lateral is reached, the motion being wrist and digital. Shifting 
 the fulcrum-point to the end of the third finger on the edge of the right 
 upper cuspid, the labial surfaces of the left central and lateral may be 
 scaled with the same instrument. With the hand resting against the 
 
 Fig. 177 
 
 chin just below the lower lip, and the third joint of the little finger 
 serving as a fulcrum, with instrument No. 18, the right central and 
 from there back to and including the third molar is scaled, using the 
 digital motion, as in Fig. 180. 
 
 The lingual as well as the labial and buccal surfaces, having been 
 covered, No. 13 is used for the distal surfaces (Fig. 157) of all the upper 
 teeth excepting the incisors. For the molars, bicuspids and cuspids of 
 the upper jaw the description of the use of this instrument for those 
 
INSTR UM EN TA TION 
 
 257 
 
 on the lower jaw may be applied, the hand rest being found chiefly 
 on the cutting edge of the lower incisors, the end' of the third finger 
 
 Fig. 178 
 
 17 
 
 Fig. 179 
 
258 
 
 DENTAL PROPHYLAXIS 
 
 serving for fulcrum. No. 14, Fig. 158, is used in a similar manner with 
 the hand rests the same as for No. 13. Nos. 5 and 6 are best adapted 
 
 Fig. 180 
 
 Fig. 181 
 
 for the approximal surfaces of the incisors, their use at this point being 
 too self-evident to need explanatiop, 
 
INSTRUMENTATION 259 
 
 Even with this detailed description, much will be found lacking to 
 the beginner, but after a little practice on the manikin the hand will 
 soon adjust itself to the proper rests to secure the greatest efficiency 
 and control of the instrument. 
 
 In removing the heavy deposits the sickle-shaped instrument, No. 3, 
 and scalers Nos. 33 and 34 will be found most useful. In skilful hands 
 it is possible to scale roughly nearly all the surfaces of all the teeth 
 with these instruments, the exception being the approximal surfaces. 
 No. 3 is used with a draw or pull stroke and has the advantage of not 
 being dangerous around the anterior teeth, for the point of the instru- 
 ment as well as the side of the blade is inserted under the deposit and 
 pulled directly upward on the lower teeth and downward on the upper 
 teeth. But in the back of the mouth where its adaptation necessitates 
 the drawing of the instrument forward under the border of the gingiva, 
 the point is likely to slip and travel too deep into the subgingival space 
 unless care is used. A firm hold on the instrument and a secure brace 
 of the hand is absolutely essential. This sickle-shaped instrument 
 is used almost entirely with a digital motion and the two principal 
 positions are illustrated in Figs. 182 and 183. It is very difficult to 
 scale the teeth thoroughly with this instrument, but the larger deposits 
 having been removed at the first sitting, Nos. 17 and 18 can be used to 
 advantage at the second and all subsequent treatments. 
 
 The Harlan instruments, Nos. 3 and 4, are also used with a draw 
 stroke and are helpful in removing th6 small, hard, tenacious deposits 
 under the free margin of the gums. They are adaptable in nearly all 
 sections of the mouth and their use is usually self-suggestive. When 
 these small deposits resist Nos. 17 and 18, especially on the bicuspids, 
 cuspids and incisors, these Harlan instruments will be found very 
 effective. 
 
 If uncertainty exists in the mind regarding the thorough removal 
 of all deposits, an instrument known as an explorer carefully passed 
 around the neck of the tooth under the gingivae will readily detect 
 any small deposits or uneven surfaces. The smaller the instrument, 
 the more greatly is the sense of touch magnified. It is for this reason 
 that the use of Nos. 17 and 18 is advised wherever practical. 
 
 There are two special features to be considered under instrumenta- 
 tion : First, the sensitiveness that is frequently found around the necks 
 of the teeth, and second, the bleeding of the gingival borders of the 
 gums. In adults where the lime deposits have been heavy, their re- 
 moval will frequently cause much sensitiveness for a week or two, 
 sometimes even longer, to heat and cold and to sweets and acids. The 
 deposits have caused an absorption of the border of the alveolar process, 
 the soft tissues and the cementum around the necks of the teeth, and 
 when they are removed the interglobular spaces on the border between 
 the dentin and the cementum are exposed, presenting an area that is 
 highly sensitive to the touch of the instrument or polisher. It. is fre- 
 (^uently wise to inform the patient that he maj^ expect the surfaces to 
 
260 
 
 DENTAL PROPHYLAXIS 
 
 Fig. 182 
 
 Fig. 183 
 
POLISHING 261 
 
 be responsive to heat and cold for a short time, in order to allay any 
 fears on his part. The deposits acting as a covering for these surfaces 
 have protected them from external irritation, and the patients are apt 
 to wonder why it is that their mouths are so much more sensitive than 
 they were before the deposits were removed. Acids are especially 
 irritating to these surfaces and the use of bicarbonate of soda, half a 
 teaspoonful to a third of a glass of warm water, used as a mouth wash 
 two or three times daily, will aid greatly in tiding over this short period 
 of discomfort. If the soda can be used clear by dipping the finger in 
 water, touching it to the soda and then rubbing it on these surfaces, it 
 will all the more quickly neutralize any acid that may be irritating 
 to this sensitive tissue. The thorough rubbing and polishing with 
 the stick and pumice and the extreme cleanliness from the faithful 
 use of the tooth-brush will soon bring these troublesome areas under 
 control. The application of a 10 per cent, solution of nitrate of silver is 
 sometimes advised, but if it is used, it should be followed by a thorough 
 polishing with the stick and pumice. 
 
 The second feature, which will be considered briefly, is the bleed- 
 ing of the gums during instrumentation. When the gums readily 
 bleed there is congestion of the capillaries, and the more blood allowed 
 to escape from the gingivae, the sooner the congestion will be relieved. 
 Instead of trying not to make the gums bleed, just the reverse course 
 should be followed, although of course this does not mean that they 
 should be lacerated or the tissue wounded. The bleeding process is 
 produced by using the back or smooth surface of the blade of the instru- 
 ment with pressure, and this is done while removing the lime deposits, 
 and if there is a copious flow of blood from some of the approximal 
 surfaces, it should be encouraged by rapid, gentle pressure strokes 
 directly on the gingivae. Healthy gums will not bleed during instru- 
 mentation, and when bleeding occurs enlarged and congested capilla- 
 ries are sure to be found. No fear of causing injury to the gum tissue 
 in causing a flow of blood need be felt as long as care is taken that 
 the blade of the instrument does not cut the tissue. Frequently after 
 such a treatment the gums will take on a color two shades lighter before 
 the patient leaves the chair, and after a few days of stimulation with 
 the tooth-brush it will be hard to recognize it as the deep red, congested 
 tissue that it was at first. 
 
 POLISHING. 
 
 It is impossible to obtain the same results in prophylaxis with the 
 use of the dental engine in polishing as may be secured with the hand 
 polishers. This belief is based upon personal experience in faithfully 
 trying out both methods, and is an accepted fact by all prophylactic 
 workers who have become proficient with the hand polishers. 
 
 The object of this polishing process is threefold : First, the removal 
 of stains, plaques and films or all soft accretions on the exposed sur- 
 faces of the teeth. Second, a polishing of the enamel surfaces and a 
 
262 
 
 DENTAL PROPHYLAXIS 
 
 stimulating effect that seems to be imparted to the living tissue of 
 the tooth itself by the vigorous massage. Third, the beneficial results 
 obtained on the gingival borders of the gums by the slight bumping 
 of the stick, causing light pressure and release which imparts a massage 
 effect and aids greatly in producing a perfect flow of blood through 
 the capillaries in the peripheral circulation. If a new case presents 
 itself in which the teeth are very badly stained, it is perfectly reason- 
 able, if desired, to use the dental engine for the first treatment to aid 
 in cleaning off these stains from the enamel surfaces, but all subsequent 
 treatments should be made with the hand polishers. An engine 
 revolving at six or eight hundred revolutions a minute, with the rubber 
 cup or buff charged with pumice, cuts too viciously and if used at each 
 
 Fig. 184 
 
 prophylactic treatment, will in time affect the enamel and tooth struc- 
 ture at the necks of the teeth. With the dental engine all sense of touch 
 is lost, and besides it is not as adaptable on the approximal surfaces 
 or on the surfaces of the molars as the stick held in the hand. The 
 gingival borders of the gums, in many mouths, have been badly 
 wounded or damaged by the revolving cups or buffs in the dental 
 engine, and if one hopes and expects to secure the best results in obtain- 
 ing ideal health conditions of these tissues, one must become proficient 
 with the hand polishers. Those who would advocate the dental engine 
 are those who have failed to make themselves proficient with the hand 
 polishers. There can be no choice if the latter is faithfully tried. 
 There are a number of different woods that may be used for polishing, 
 as cedar, maple, hard pine, etc., but the closest-grained wood and the 
 
POLISHING 
 
 263 
 
 one best adapted for this purpose is oranj^e wood. Tliere are two sizes 
 of sticks that may be had from the dental depots, known as large and 
 small. The large size is cut about three quarters of an inch in length 
 and one end is trimmed wedge-shaped. This stick is used on all the 
 broad surfaces of the teeth excepting the masticating surfaces. The 
 small stick is cut about the same length and one end is sharpened like 
 the point of a lead-pencil. The smaller stick is used on the approximal 
 surfaces and around the necks of the teeth where it is impossible to 
 adapt the larger stick. In order to work with facility, two holders 
 for the two sizes of sticks should be employed. Fig. 184 illustrates the 
 Jack porte polishers with sticks in position. 
 
 As a slight abrasive and polish to be used with the sticks, the finest 
 grade of pumice moistened with water will prove to be the most satisfac- 
 tory. x\lthough other polishing mediums are used with good results, it 
 is doubtful if there is anything superior to fine pumice for this special 
 
 Fig. 185 
 
 work. A scant spoonful placed in a small porcelain dish, and wet 
 sufficiently with water to be almost liquid, will make a mixture that 
 can readily be picked up on the point of the wet stick and used in the 
 mouth. 
 
 System for Polishing. — Just as a definite system is employed in going 
 over the teeth with the instruments, so should a system for reaching 
 all surfaces of the teeth with the polishers be followed. 
 
 The following system is very effective and its adoption is suggested, 
 at least for beginners : 
 
 Starting on the labial surface of the right upper central with the 
 large stick, the polishing progresses to the right lateral, then to the 
 right cuspid and so on until the right last molar is reached. From 
 this point start on the buccal surface of the right lower last molar 
 and progress forward around the buccal and labial surfaces of all the 
 lower teeth to the left lower last molar. Transferring the stick to the 
 
264 
 
 DENTAL PROPHYLAXIS 
 
 buccal surface of the left upper last molar, the polishing is continued 
 forward to the median line to and including the left upper central. 
 All the labial and buccal surfaces have now been polished with the use of 
 only the larger stick. Fig. 185 illustrates direction for polishing. Then 
 starting on the lingual surface of the right lower last molar with the 
 large stick, the polishing of the lingual surfaces proceeds forward to 
 the incisors, then backward, or distally, to the lingual surface of the 
 left lower last molar. Again beginning on the lingual surface of the 
 left upper last molar, all of the lingual surfaces are covered, ending on 
 the right upper last molar. 
 
 So far only the large stick has been used. Now with the pointed 
 stick the same course should be followed over the teeth as has just 
 been described, polishing in between the teeth as far as possible and 
 
 Fig. 186 
 
 rubbing the necks of the teeth under the free border of the gingivae, 
 keeping the edge of the stick sharp. When they become frayed or 
 brush-like, they should be trimmed off with a pair of scissors, or if, 
 after this, the edges are still too blunt, sharpened with a knife. 
 
 The polishing is confined almost entirely to two motions, the rigid- 
 arm and the forearm or rotary. The one exception is the digital that 
 should be used by beginners on the labial surfaces of the upper incisors. 
 
 In order to polish effectively pressure must be used. It is this one 
 point of being able to apply pressure on all the surfaces while polish- 
 ing that makes the operation difficult. This is noted especially in 
 polishing the lingual surfaces of the molars and bicuspids. The proper 
 hand rests are essential and also muscular practice of the motions 
 used for this work. 
 
 Beginning on the labial surface of the right upper central with the 
 
POLISHING 
 
 2Go 
 
 large stick, and using a digital motion, the stick is made to travel up 
 and down the full length. of the face of the tooth, rubbing the surface 
 with both up and down strokes. The stick is allowed to bump the 
 
 Fig. 187 
 
 Fig. 188 
 
 gum lightly but not hard enough to cause discomfort. Considerable 
 pressure is used and the motion is rapid. Fig. 186 illustrates the posi- 
 tion of the hand with the thumb rest on the cuspid for the digital 
 
m 
 
 MNfAL PROPHYLAXIS 
 
 motion. When the right cuspid is reached the rigid-arm motion is 
 employed, with the back of the second finger, between the second and 
 third joints, resting on the side of the chin and the two bicuspids are 
 rubbed and poUshed up and down or longitudinally, the right thumb 
 pressing on the polisher at the end of the stick (Fig. 187) . Now insert- 
 ing the Dunn cheek distender, the buccal surfaces of the molars are 
 rubbed crosswise, using the rotary motion and the same fulcrum posi- 
 tion that was used with the cuspid and bicuspid, but the porte polisher 
 is shifted in the hand and grasped as one would hold a pen-holder 
 (Fig. 188). The end of the stick may be made to travel up and 
 down part way on the approximal surfaces, but the principal motion 
 for polishing is crosswise. The polishing of the right lower molars 
 is the same as described for the upper molars. For the right lower 
 
 Fig. 189 
 
 cuspids and bicuspids, the same as for the upper. The first finger 
 of the left hand now is placed across the inside of the lip to depress 
 it and with the polisher grasped in the fist with right thumb resting 
 on the left forefinger (Fig. 189), the lower incisors are polished. For 
 the left cuspid and bicuspids the same position as for the right is used. 
 In polishing the left lower and upper molars the back of the third finger 
 becomes the fulcrum on the side of the chin and the polisher is grasped 
 pen-holder fashion, as in Fig. 190, using the rigid-arm motion. The 
 descriptions of the right cuspid and bicuspids, lateral and central, will 
 apply to the left. It will be noted that, with the exception of the 
 upper incisors and right molars, the motion used on all the outer sur- 
 faces of the teeth has been rigid-arm. That on the inner surfaces of 
 both lower and upper is forearm or rotary. The difficulty met with is 
 
POLTSftTNa 
 
 267 
 
 Fig. 190 
 
 Fig, 191 
 
268 
 
 DENTAL PROPHYLAXIS 
 
 that of producing pressure and at the same time retaining control and 
 length of stroke. With the mouth mirror in the left hand to hold the 
 tongue away, the backs of the third and fourth fingers are pressed against 
 
 Fig. 193 
 
POLISHING 
 
 269 
 
 the chin, and the polisher held as the pen-holder in a rigid grasp (Fig. 
 191), the stick is made to travel up and down on the inner surface of 
 
 Fig. 194 
 
 Fig. 195 
 
270 
 
 DENTAL PROPHYLAXIS 
 
 the right lower molars, the edge of the stick pointing up and down with 
 the long axis of the tooth. This polishing motion, it will be noted, 
 is just the reverse from that used on the buccal surfaces. By shorten- 
 
 FiG. 196 
 
 Fig. 197 
 
 ing the hold on the polisher the same position is used for polishing 
 the bicuspids and cuspids. 
 
 Other adaptations of the stick will be found that are advantageous 
 for these surfaces, such as using the side of the stick with an up-and- 
 ^oyoi stroke instead of its sharpened end, 
 
POLISHING 
 
 271 
 
 By leaning forward in front of the patient the second finger is placed 
 on the top of the left cuspid or bicuspid and with a rocking or rotary 
 motion of the arm and stick the lower incisors are polished (Fig. 192). 
 The left lower molars are polished with the same pen-holder grasp, using 
 the second finger as a fulcrum on the right lower cuspid or lateral 
 (Fig. 193). The mouth mirror can be used to good advantage while 
 polishing the lingual surfaces by having the patient low enough. 
 Starting on the lingual surface of the left upper last molar, the porte 
 polisher is held like the pen-holder and, with the end of the third 
 finger resting on the labial surface of the right lower cuspid (Fig. 194), 
 the molars are rubbed chiefly up and down with the edge of the stick. 
 Holding the same fulcrum-point, the grasp on the polisher is gradually 
 shortened and the incisors are polished as shown in Fig. 195. The 
 
 Fig. K 
 
 lingual surfaces of the right cuspid, bicuspids and molars are polished 
 with the same hold of the polisher, the rest being found on the chin, 
 using the back of the second joint of the third finger (Fig. 196). The 
 motion used is mostly forearm or rotary. 
 
 All of the positions and fulcrum-points described for the large stick 
 apply also to the small stick. 
 
 Where the gums between the teeth are congested, the side of the stick 
 is pressed against them with a fast, quick stroke to encourage the 
 bleeding. Care should be taken in the use of both sticks not to abrade 
 the gingivae, but the light pressure with the side of the stick against 
 the gum margin will prove very beneficial (Fig. 197) . When sensitive 
 surfaces are found at the necks of the teeth, the pointed stick freely 
 ch9,rged with pumice is applied with vigor and considerable pressure, 
 
272 
 
 DENTAL PROPHYLAXIS 
 
 A thorough polishing of their surfaces will greatly aid in reducing the 
 sensitiveness. 
 
 Floss Polishing. — After polishing with the sticks there still remain 
 the contact points and an area on the approximal surfaces that have 
 not been reached. By doubling a length of ligating silk, twisting it 
 and dipping it in water and then in pumice, these surfaces may be 
 polished quite effectually. When the teeth are very close together a 
 single strand will be found sufficient, as this silk is larger in size than 
 that sold for every-day flossing. Cutters' wide floss may also be used 
 to advantage where the space will permit. When using the floss for 
 polishing it should be passed between the contact points with care, 
 so that it will not snap on the gum, drawn back and forth on the distal 
 
 Fig. 199 
 
 surface of the tooth and then pressed backward rubbing the mesial, 
 surface of the adjoining tooth. Most of the decay takes place in these 
 surfaces and they must be given careful attention. If the ends of the 
 floss are wound around the first fingers as illustrated in Figs. 198 and 
 199, it can be easily manipulated. 
 
 Brush Wheel. — ^The masticating surfaces are so uneven that a stick 
 cannot be used on them very well, so it will be necessary to use a brush 
 wheel in the engine to reach down in the sulci to polish these surfaces. 
 With the wheel dipped in water and the edge of it touched to wet 
 pumice, the engine should be run at a moderate speed and the edge 
 of the wheel applied down in the sulci of the molars and bicuspids. 
 The Dunn cheek-distender should always be used. It is almost unnec- 
 
POLISHING 
 
 273 
 
 essary to state that the sticks, the pumice, the floss and the brush 
 wheel should not be used a second time. Figs. 200 and 201 show the 
 adaptation of this wheel. 
 
 Fig. 200 
 
 Fig. 201 
 
 Children. — In the prophylactic treatment of children it is seldom 
 necessary to use the instruments. As it is the roots of the teeth that 
 are most susceptible to disease in adults, so are the masticating and 
 approximal surfaces most susceptible in children. These surfaces should 
 be carefully polished with the floss and pumice, and the sulci in the 
 masticating surfaces with the brush wheel in the engine. The polish- 
 ing of all the surfaces of the teeth with the sticks should be done as 
 described for the adult. 
 18 
 
274 DENTAL PROPHYLAXIS 
 
 To assist in the removal of bacterial plaques and green stains on the 
 surfaces of the teeth, a small napkin should be used to dry the teeth, 
 then with a pledget of cotton Churchill's Compound Tincture of lodin 
 is applied and allowed to dry. The iodin assists chemically in the 
 removal of plaques and stains. The thoroughness of the polishing 
 operation may be tested by applying iodin to all the surfaces of the 
 teeth after the hygienist considers the operation finished. The mouth 
 is then rinsed with warm water and if the iodin has not adhered to 
 any surface of the teeth, it may be assumed that the plaques have 
 been thoroughly removed. 
 
 Attention is called to a preventive treatment of the fissures in the 
 first permanent molars of children that comes within the province of 
 the dental hygienist. 
 
 When these fissures are found to be exceptionally deep, likely to 
 retain food debris and thus susceptible to decay, a quick-setting, 
 hydraulic cement should be mixed, and with cotton rolls on each side 
 of the tooth, the fissures should be dried with warm air, and washed 
 with a pledget of cotton soaked with alcohol, again dried and then 
 with an explorer the soft cement worked down into the fissures. As 
 the cement begins to toughen and set, the end of the second finger is 
 dipped in a glass of water and with the ball of the finger the cement is 
 pressed firmly down into the fissures and held there for a moment or 
 two until it has become fairly hard. The surplus can easily be trimmed 
 away and the cement in the fisswes will last for some time, acting as 
 a protection to their surfaces. It takes but a short time to renew it 
 when it wears away, and will frequently save these teeth from decay 
 at the susceptible period of from six to twelve years of age. 
 
 Instructions for the Home Care of the Mouth. — Brushing. — A 
 remarkable condition of health and beauty of the gums, and a high 
 resistance and increased vitality of the pericementum may be developed 
 by the proper form of brushing. It may be well to first consider the 
 blood supply to the pericementum in relation to the circulation in the 
 gum tissue itself. The blood supply to the pericementum may be 
 described as follows; the small arteries entering the apical space break 
 up into branches, one or more of them enter the pulp canal through the 
 apex of the root and the others pass down through the fibers of the 
 pericementum. During their course through this tissue on their way 
 to the alveolar border and the gums, they both give off and receive 
 branches through the alveolus and connect with the plexus of small 
 bloodvessels and capillaries of the gmn tissue. It will thus be apparent 
 that the blood circulation in the gums is very intimately associated 
 with the circulation of the pericementum. It frequently happens that 
 when an alveolar abscess develops at the apex of the root of a tooth, 
 the bloodvessels in the apical space are destroyed yet the pericementum 
 does not suffer from lack of blood, for the branches coming to it from 
 the walls of the alveolus soon enlarge and produce a sufficient supply. 
 It must, therefore, be noted that in order to stimulate the blood supply 
 
POLISHING 275 
 
 of the pericementum it is merely necessary to stimulate the circulation 
 in the gum tissue. 
 
 Fibers of the pericementum radiate into the gum tissue and strong 
 bands of fibers which form the dental ligament blend into the periosteum 
 of the alveolar process. Some of these fibers are so close to the surface 
 in the gum tissue that it is not difficult to understand why an unusual 
 response to health may be obtained by surface stimulation. 
 
 In the process of masticating coarse foods, a natural massage takes 
 place in the following manner: The coarse foods sliding over the 
 surfaces of the teeth press upward on the upper gums and downward 
 on the lower gums creating a pressure and release on the bloodvessels 
 in the gum tissue which stimulates the circulation. 
 
 The teeth being occluded with considerable force are pressed down in 
 their sockets. The pericementum is thus compressed and the blood is 
 squeezed out of the small bloodvessels through the walls of the alveolus. 
 As the jaws open and release the pressure on the teeth, the pressure 
 upon the small bloodvessels is also released and the blood comes rushing 
 in again. This pressure and release is similar in its action to a massage 
 of the tissues on the surface of the body. Such a process always 
 produces a free flow of blood, and prevents congestion or stasis in the 
 capillary circulation. 
 
 Keratin. — In the basement layer of the skin, cells are constantly 
 being formed and forced slowly upward toward the surface of the body. 
 During their transit the cells slowK' change their shape, becoming long 
 and flat in appearance and finally form the pavement or squamous 
 type of epithelium on the surface of the skin. During this period, from 
 the time of formation to their arrival on the surface of the body, a 
 gradual metamorphosis or change takes place in the protoplasm of the 
 cell. The content of the cell gradually begins to toughen and this 
 process continues just in proportion to the needs of protection against 
 undue friction or exposure. The horny hands of the day laborer, or 
 the corns that form on the feet, are examples of the extreme expression 
 of the activity and change in these cells. The content of the cells 
 when so changed or toughened is known as keratin. 
 
 The mucous membrane of the mouth is but a continuation or an 
 infolding of the skin. Its epithelium is of the squamous type similar 
 to that of the skin, but the stratified cells which have the power of 
 forming keratin are found only on those portions of the mucous mem- 
 brane covering the gum tissue and the roof of the mouth. If the gum 
 tissue is artificially stimulated three or four times a day with the bristles 
 of the tooth-brush, a noticeable change takes place in the texture of the 
 mucous membrane. It soon loses that smooth, glassy or sleazy appear- 
 ance and under a magnifying glass shows a thickened or toughened 
 surface which seems to act as a protective armor for the underlying 
 tissues and makes the ingress of infection through the gum tissue, or 
 at the gingivae, extremely difficult. Inference should not be made 
 that there is produced a hornified mucous membrane, except in a 
 
276 DENTAL PROPHYLAXIS 
 
 modified sense, but a beneficial change takes place that is much to be 
 desired. A similar texture of membrane may be found in the mouths 
 of carnivorous animals. 
 
 The Gums. — In considering the health of these dental tissues the 
 gums found in the average mouth should first be noted. Aside from 
 the unsanitary aspect of the crowns of the teeth, the gums will be 
 found to be of a deep red color, the gingivae usually showing even a 
 deeper red. The blood is almost stagnant on some of the margins, 
 and the tissues will bleed upon the slightest touch. Waste products 
 are not being properly eliminated, oxidation is imperfect and blood 
 serum, which contains the lime salts for serumal deposits, oozes in 
 the subgingival spaces and forms an ideal medium for bacteria. These 
 are the average gums of adults, who eat food which requires but little 
 mastication and produces but little friction on the gums, and who 
 take scant care of their mouths. But how quickly all of these con- 
 ditions will change under artificial stimulation. The instant the gums 
 are brushed properly, the blood starts to flow more rapidly and a new 
 life and color make their appearance. After a thorough prophylactic 
 treatment and a lesson in gum brushing it is not unusual to see the 
 tissues lighten in color, possibly two or three shades in twenty-four 
 hours. At the end of a week or ten days they assume a still lighter 
 shade and after periods ranging from three to six months they become 
 a light coral pink, and hold this color as long as they are daily brushed 
 and stimulated. "^ 
 
 There is apparently a peculiar pink shade that practically every 
 individual may acquire if the brushing is faithfully followed. In fact 
 this color may be taken for so sure an index, that it is easy to tell at a 
 glance whether the patient has been brushing the teeth and gums four 
 times daily. Virtue, in this case, has its own reward, for the color 
 is always obtained when the brush has been used according to rule. 
 The gums should be of uniform color in all parts of the mouth, the 
 gingivae showing no difference in shade from that of the body of the 
 gum. 
 
 Tissue Stimulation. — If the following rules are honestly observed the 
 same results are assured in every mouth : 
 
 1. The form of brushing as described in this chapter. 
 
 2. Brushing long enough — not less than two minutes after meals. 
 
 3. Brushing four times a day. 
 
 Many cases have been baffling because they would not respond to 
 treatment, but when the patient gives a demonstration at the wash 
 bowl, it will show that he makes some omissions or uses an incor- 
 rect form of brushing which, when corrected, will bring results in a 
 short time. Sometimes patients will claim to have followed the rules 
 when, upon close investigation, it will be found that they have not 
 done so. 
 
 When the gum tissue will not assume this light pink shade in a few 
 months' time, and when the patient is expert with the tooth-brush and 
 
POLiSHlNG 277 
 
 claims to follow the rules faithfully, it may be suspected that in some 
 way the rules are not lived up to or that otherwise a very rare excep- 
 tion has been found. 
 
 Evidently this color that the gums assume under the daily brushing 
 is due to the fast flow of blood through the capillaries, the perfect 
 oxidation of the cells and thorough removal of their waste products, 
 as well as a thickening or toughening of the epithelial layer of cells on 
 the surface. The festoons become pink and tough, the surface of the 
 mucous membrane loses its thin, glassy appearance, and when dried 
 looks tough and firm. Also when the edges of the gum are dried they 
 do not weep. Little or no serum oozes now from this tissue and it 
 will be noted that the serumal deposits, found so plentifully under the 
 congested borders of the gums, almost entirely disappear at subsequent 
 treatments. It must not be assumed that the miraculous happens 
 under these unusual health conditions or that merely learning how to 
 brush the gums will eliminate all present and future disease of the 
 mouth. However, one cannot help being enthusiastic when viewing 
 the rapid return to health of the dental tissues under artificial stimula- 
 tion. The pericementum seems to acquire new life, and apparently 
 feels the stimulation in every fiber and cell. Loose and sore teeth 
 become tight and free from soreness, providing that too much of 
 their supporting tissue has not been lost. Chronic cases of perice- 
 mentitis disappear and even the pi^up itself maj' be relieved of conges- 
 tion if it is slight and has not progressed too far. There is no doubt 
 that the osteoblasts, under prophylaxis and this stimulation, do at 
 times replace small areas of lost alveolar process. Where roots have 
 been exposed on the labial or approximal surfaces, especially those of 
 the incisors and cuspids, it is not uncommon to see gum tissue creep 
 back over the exposed root to a considerable degree and oti approximal 
 surfaces there has been a filling in of the bony tissue to support the gum 
 which is undoubtedly a new deposit of process. When it is considered 
 that the osteoblasts are present in the peridental membrane throughout 
 life and slowly add to the alveolar wall of the socket, it is not unreason- 
 able to expect them to lend their aid when stimulated and the irritating 
 cause is removed. 
 
 It seems probable that it is not only possible to sterilize tissue by 
 this perfect circulation, artificially induced, but also that small serumal 
 deposits may be dissolved and disposed of by the blood or possibly 
 by the action of the cells in these tissues. This statement does 
 not mean that when the dentist treats surgically a case of pyorrhea 
 alveolaris, merely teaching the patient how to brush his gums will 
 cause the dissolution of the deposits and kill the infection. It is 
 exceedingly important that gum brushing should be taught and the 
 patient trained by repeated lessons until he acquires this art, for it 
 really is an art. With the additional aid of the gum brushing the pus 
 will soon cease, the pockets will contract and close, soreness will be 
 relieved and any small granular deposits that may be left will gradually 
 
278 DENTAL PROPHYLAXIS 
 
 disappear as the tissue hugs up tightly to the root. The tissues thus 
 artificially stimulated seem to possess five properties. The first may be 
 termed analgesic, or the relief from pain. This analgesic action is 
 the result of reducing the tension and pressure on nerve terminals from 
 enlarged and engorged bloodvessels. There is also a bactericidal 
 action or the destruction of the infection by increasing the flow of blood 
 to the parts. This sterilizing process induced in the cells of the body 
 by a perfect circulation is well known, and it is a subject of considerable 
 discussion as to whether the action is produced by phagocytosis or 
 opsonins. Under artificial stimulation the cells have also a solvent 
 power. That is, they are able to disintegrate irritating or foreign 
 substances. It is a well-known fact that a ligature of catgut in the 
 body is dissolved and disappears. Landois has shown that the blood 
 serum of every animal has the power of dissolving the blood corpuscles 
 from a different species. The origin of the solvent which disintegrates 
 granules of serumal deposits can only be conjectured, but it is a fact 
 that they do disappear as a result of perfect circulation. 
 
 The eliminative property is greatly facilitated and permits the 
 lymphatics to readily absorb and dispose of waste products and irritat- 
 ing substances. There is also the nutritive property which is self 
 evident, and is due chiefly to a perfect oxidizing process. There is 
 still much to learn concerning these artificial stimulants. If the 
 existence of human beings were mor.^ like that of animals, this condition 
 would be induced each time that the meal of coarse food was chewed. 
 Since the artificial rather than the animal life is preferred, and coarse 
 food is not attractive, why should not this condition of health be 
 produced artificially? 
 
 Tooth-brushes. — Opinions vary greatly concerning the size and shape 
 of the tooth-brush. One educator of the middle West states in a letter 
 that he did not recommend a hair-brush, a nail-brush or a shoe-brush 
 for brushing the teeth, but a tooth-hru^h. His position might have 
 received serious consideration if it were only the crowns of the teeth 
 that were involved, but as the brushing of the gums and the roof of the 
 mouth is of equal importance with brushing the teeth, a brush that will 
 adapt itself to all these surfaces is the one to use. In fact this process 
 may be better termed mouth-brushing. 
 
 If cross-wise brushing is indulged in or a slow twisting massage 
 or wiping motion is employed, the form and size of the brush may be 
 varied. Personally, the writer has not been able to secure as satis- 
 factory results with either of these forms of brushing. The cross-wise 
 brushing seems to irritate the festoons, at times create absorption, and 
 lacks the cleansing action upon the outside surfaces. The wiping 
 motion with the sides and ends of the bristles is more cleansing and 
 the gums take more kindly to this form of brushing, but this motion is 
 necessarily slow and lacks the stimulating effect produced by a fast 
 stroke. When it is considered that nature intended that the pressure 
 should be chiefly upward on the upper gums and downward on the 
 
roLiSHiNd 
 
 m 
 
 lower gums, such as is induced by food sliding over the surfaces of the 
 teeth in mastication, it can be seen that this process can be better 
 simulated by a circular stroke than by any other. The gums appear 
 to thrive under the circular stroke, a stimulus is imparted to the circu- 
 lation and a thorough cleansing effect is produced along the curved 
 lines of the festoons and upon a third of the approximal surfaces. A 
 slow, deliberate stroke is not as stimulating as a fast, light stroke. 
 The best way to bring blood to the surface of a tissue in a short space 
 of time is to use a light, rapid massage. 
 
 The results will justify the means, so a circular stroke for the buccal 
 and labial surfaces is advised. In order to secure the proper adaptation 
 of a brush to the surfaces of the gums and the teeth, the shape of the 
 bristle ends of the brush is important. Many of the popular brushes 
 on the market are nearly concave in shape, having a long toe and heel 
 with the shorter bristles near the center. Such a brush, placed squarely 
 across the front teeth, seems to fit when at rest, but if slowly moved 
 
 Fig. 202 
 
 about the mouth, it will be found to ride in many places on the toe 
 and heel alone or, if pressure is used, these long bristles ride sidewise 
 or any other way. Although the cranium is convex in shape, it has 
 never been deemed expedient to use a concave hair-brush. In fact, 
 a concave brush would not be as effective as a straight one, although it 
 might seem to fit better when at rest. A straight-cut tooth-brush with 
 a slight tuft on the end is best adapted to most of the surfaces in most 
 mouths. The bristles should be of sufficient length to be flexible yet 
 springy and stiff enough not to lose their life or spring after the first 
 two or three days' use. This necessitates using a brush with bristles 
 a trifle hard, for such a brush becomes softened after a few days' use. 
 Fig. 202 illustrates the two shapes of brushes just referred to. When 
 instructing a new patient in the art of brushing, a soft brush should be 
 recommended to start with, or the patient should be warned not to 
 be too strenuous with the stiff' brush until the gums have had a chance 
 to become tough and the mucous membrane thickened, otherwise 
 slight abrasions of the mucous membrane will be produced, and a sore 
 
280 
 
 DENTAL PROPHYLAXIS 
 
 and tender surface will result if the gums are brushed at first with too 
 much pressure and vigor and with a stiff brush. It is a well known fact 
 that in the use of a fairly large brush with three or four rows of straight- 
 cut bristles, set well apart, the pressure on any one point is consider- 
 ably reduced in proportion to that produced by a shorter and narrower 
 brush. For this reason the best results from mouth brushing in adults 
 may be obtained when it is possible to use a large brush. 
 
 Instructions for Brushing. — The process of the brushing of the mouth 
 may be divided into three parts: 
 
 First, the outside or buccal and labial surfaces of the teeth and 
 girnis. 
 
 Second, the inside or palatal and lingual surfaces. 
 
 Third, the occlusal or masticating surfaces of the teeth. 
 
 Fig. 203 
 
 The Buccal and Labial Surfaces. — ^With the brush held in the hand, as 
 in Fig. 203, and with the teeth nearly closed, the brush is placed inside 
 the cheek on the left side, so that the ends of the bristles are lightly 
 in contact with the gums over the upper molars. Now, with a fast, 
 circular motion the brush is swept backward and downward, reaching 
 as far down on the lower gums as the brush can travel in this posi- 
 tion, then forward and upward as high on the gums of the upper 
 teeth as possible (Fig. 204). 
 
 The brush should travel in a perfect circle, not in an oblong tract, 
 and in as large a circle as the vestibule of the cheek will permit. Very 
 little pressure should be used, for the stimulating as well as the cleansing 
 
POLISHINO 
 
 281 
 
 process is accomplished by the rapidity of the stroke and the direction 
 traveled by the ends of the bristles. Continuinjj; this fast, circular 
 
 AGE !7 
 
 Fig. 204 
 
 motion the brush should be made to travel very slowly forward until 
 the heel (the bristles nearest the hand are called the heel) engages the 
 
 Fig. 205 
 
 right cuspids. Pausing on the incisors to stimulate thoroughly the 
 gums on both jaws, start back again slowly to the region of the molars 
 (Fig. 205). 
 
^8^ 
 
 DENTAL PROPHYLAXIS 
 
 It will be understood that the brush is constantly in rapid motion, 
 travelling in a large circle with the ends of the bristles lightly touching 
 the gums and teeth. 
 
 Fr^.. 206 
 
 Fig. 206 illustrates the position of holding the brush for the right 
 side. On this side some persons find it easier to maintain a circular 
 
 Fig. 207 
 
 motion by reversing the stroke, or brushing from the lower gums back- 
 ward and upward. It makes no difference in which direction the brush 
 
POLISHING 
 
 283 
 
 travels as long as the circular stroke is adhered to. Assuming that one 
 is using the right hand for brushing, it will not be possible to brush 
 farther forward than the right cuspid teeth (Fig. 207). Directions for 
 brushing the left side are applicable to the right. 
 
 Lingual Surfaces. — 1. Upper. The brush should be held as shown 
 in Fig. 208. The roof of the mouth as well as the lingual surfaces of 
 the upper teeth are brushed with an in-and-out stroke, as in Fig. 209. 
 
 The festoons on the palatal and lingual surfaces cannot be properly 
 brushed with the circular stroke. It may be noted that they assume a 
 much straighter line than on the buccal and labial surfaces. Therefore 
 the bristles travelling in and out with this straight line reach all sur- 
 faces and are stimulating and non-irritating in their action. 
 
 Fig. 208 
 
 The ends of the bristles should be placed against the gums of the right 
 molar teeth, and the brush drawn straight forward until the heel wipes 
 the lingual surfaces of the right incisors and cuspids and protrudes 
 from the mouth for a short distance. The upper lip should be drawn 
 downward to prevent the moisture from being thrown outward by the 
 snap of the bristles passing over the edges of the incisors. The brush is 
 now pushed straight back again on the gums and this in-and-out stroke 
 is rapidly made and confined on this surface for a few seconds. This 
 fast in-and-out stroke of the brush is kept up and carried across the 
 roof of the mouth until all of the hard palate is covered and the gums 
 on the left side of the mouth are reached. Here the in-and-out stroke 
 is applied rapidly for a few seconds, as far back as the distal surfaces of 
 
284 
 
 DENTAL PROPHYLAXIS 
 
 the third molars. The same stroke should be used on the return, the 
 palate should be crossed to the right side again, and again back to 
 the left side. Special care should be used to reach the gums around 
 the last molars, as there is a tendency not to brush back far enough. 
 
 Fig. 203 
 
 2. Loicer Lingual Surfaces. — The lingual surfaces of the lower teeth 
 are the most difficult to brush and it requires quite a little practice before 
 
 Fig. 210 
 
 the gums, especially on the right side, can be deftly reached. Nineteen 
 out of twenty mouths will disclose a congested gingival border on 
 the lingual surfaces of the right lower molars, and in order that the wrist 
 
POLISHING 
 
 28: 
 
 may bend freely so that the toe of the brush may reach this surface, 
 it is suggested that the brush be held in the hand as in Fig. 210. 
 
 These gum surfaces are brushed almost entirely with the toe or tuft 
 of the brush, the motion being a fast in-anrl-out stroke, similar to that 
 
 Fig. 211 
 
 used on[the hard palate, as in Fig. 211. Starting on the right side with 
 the bristles of the tuft resting on the gum next to the last molar, the 
 brush is drawn forward. In this case the bristles at the heel do not 
 sweep the lower incisors as the handle of the brush is tipped slightly 
 upward. 
 
 Fig. 212 
 
 The brush is now forced backward in the same line, leaning slightly 
 toward the tongue, and the in-and-out stroke is applied rapidly to 
 this surface. Maintaining always this fast stroke, and slowly coming 
 forward, the handle of the brush is now raised to a sharp angle and the 
 gums below the incisors are brushed with an up-and-down stroke. 
 
286 DENTAL PROPHYLAXIS 
 
 going back and forth across them several times. Continuing the in- 
 and-out stroke the tuft is adapted to the gums of the left side and they 
 are brushed in a manner similar to that described for the right side, 
 again slowly returning to the right and repeating once more to the left 
 side. A slight gagging sensation will sometimes be felt in trying to 
 reach as far back as the brush should actually go, but with persistent 
 practice this can be greatly overcome in a short time. 
 
 Masticating Surfaces. — Lastly the masticating surfaces should be 
 brushed in order to remove any food debris in the fissures or sulci of 
 the molars and bicuspids. The tuft of the brush should also be carried 
 to the distal surfaces of the last molars on both the upper and lower 
 jaws and with a wiping or twisting motion these surfaces should be 
 cleansed. 
 
 The foregoing description of brushing gives but a stereotyped form. 
 The mouth should be gone over three or four times until the gums 
 begin to tingle and a slight sense of numbness is felt. 
 
 In the roof of the mouth are the posterior and anterior palatine 
 arteries which help to supply the gum tissue, hence the importance of 
 brushing the hard palate (Fig. 212). 
 
 It should be noted that the brush is Used with a full-arm motion 
 and that a fast but light stroke is essential to secure the desired results. 
 
 Number of Daily Brushings. — Not so very many years ago more than 
 one bathtub in a private houst^ was considered a luxury. Today it 
 is realized that frequent bathing is a necessity. 
 
 Some dentists advise their patients to brush their teeth before 
 retiring; some, night and morning; and the patient who followed this 
 last rule, thought himself virtuous indeed. The matter of brushing 
 the teeth is purely educational and resolves itself into a habit. Time 
 can always be found for any habit — it is merely a question of what 
 habits are acquired. 
 
 After each meal a certain amount of food is retained on the surfaces 
 of the teeth. In less than an hours' time this food begins to decom- 
 pose. If the teeth are brushed at night and in the morning before 
 breakfast, remnants of the breakfast remain on the teieth until bed- 
 time, joined through the day by those of lunch and dinner. There 
 may be some arguments in favor of not disturbing the decomposing 
 food in the mouth all day, but such arguments are usually based on 
 the statement that people do live with unbrushed teeth, so why handi- 
 cap them with an extra daily duty when they have so little time to 
 spare. Those who advance these arguments usually have a breath 
 far from pleasing. It cannot be shown scientifically that a mouth 
 containing decomposing food is as healthy and wholesome as one that 
 is free from it. 
 
 The teeth should be thoroughly cleaned after each meal with brush 
 and dentifrice, and given a vigorous brushing with clear water the 
 first thing in the morning. This means four brushings a day. Of 
 course it is not always possible to follow this rule to the letter, but where 
 one has access to a bowl and one's tooth-brush, the teeth should be 
 
POLISHING 287 
 
 cleaned. All children should be taught this habit, as there can be no 
 greater insurance for health and freedom from infectious diseases 
 than a mouth free from decomposing food. 
 
 Dentifrices. — The most important ingredient in a dentifrice is soap. 
 Next, a mild abrasive, such as a fine grade of precipitated chalk. 
 The rest ot the formula is of but little value and is used chiefly to dis- 
 guise the soap and impart a pleasant taste. The removal of grease is 
 a chemical action and soap is essential for thoroughly cleaning the 
 teeth. If fat is rubbed on the hands or on a slab of glass it will be 
 difficult to remove it with clear water and a brush. Although with 
 considerable effort it may be done, soap will remove it much more 
 quickly. A fine grade of powdered Castile soap is the best, but it is 
 seldom found in the preparations on the market, as it does not give 
 sufficient lather to suit either manufacturer or purchaser. The most 
 harmful constituent in a dentifrice is a gritty, coarse grade of chalk. 
 The teeth should be cleaned, not scoured, and the daily use of a gritty 
 dentifrice will eventually cause abrasion of the thjn enamel surfaces 
 at the necks of the teeth. In fact some preparations contain pumice 
 and in one foreign production, powdered oyster shells were found. 
 The grit may be readily detected by placing some of the paste or powder 
 between th:e teeth and biting on it. Finer tests may be made by putting 
 it between two glass surfaces, rubbing them together and examining 
 them with a magnifying glass, 
 
 A mild abrasive is helpful in the* removal of the slippery film of 
 mucin and viscid accretions on the surfaces of the teeth. Its daily use 
 is harmless providing the grit is fairly soluble and not coarse. When 
 one computes the number of occlusions that take place daily between 
 the masticating surfaces of the teeth during the three meals and notes 
 what little wear of the enamel cusps is exhibited at thirty-five or forty 
 years of age, it may be concluded that the use of a fine grade of precipi- 
 tated chalk as a base for a dentifrice is not a serious menace to the 
 enamel tissue. There is but little choice between powder and paste, 
 as regards efficiency. Powder has to be worked into a past-like 
 condition in the mouth with the brush, while paste quickly spreads 
 itself over the teeth for immediate action. The majority of people 
 find the paste much more pleasant to use. The difference in the f ormulse 
 of the two preparations consists in leaving out the saccharin in the 
 powder and mixing the powders and oils with glycerin to form paste. 
 
 A simple, cheap and effective power may be made by placing the 
 following ingredients, all of which may be bought at any drug-store, 
 in a quart Mason jar: 
 
 Finest grade English precipitated chalk h pound 
 
 Powdered Castile soap If ounces 
 
 Light carbonate of magnesia \ ounce 
 
 Oil of clove 46 drops 
 
 Oil ol wintergrecn 35 " 
 
 Oil of sassafras 35 " 
 
 Oil of peppermint ... 18 " 
 
 Saccharin — finely powdered 4 grains. 
 
288 
 
 DENTAL PROPHYLAXIS 
 
 The glass top should be securely fastened and the contents shaken 
 vigorously. The mixing process takes some time as it takes at least 
 twenty-four hours for the oils to permeate the powders, but the jar 
 may be picked up at varying intervals and its contents thoroughly 
 shaken. A larger bottle with the same quantity of powder will permit 
 of a more thorough mixing in a shorter time. 
 
 The brush should be very wet when the powder is placed upon it 
 and care should be taken not to inhale when introducing the brush into 
 the mouth. 
 
 A properly prepared tooth paste is a much more pleasant toilet article 
 to use and, as there are some on the market quite effective and harm- 
 less, one of these may be recommended to patients. 
 
 Fig. 213 
 
 Each tooth has five surfaces. Three of these can be cleaned with 
 the brush, but the two approximal surfaces, the most susceptible of 
 all, cannot be reached with it. In other words three-fifths of the sur- 
 faces of the teeth can be cleaned with the tooth-brush but not the 
 remaining two-fifths which most need it. It should then be apparent 
 that if all the food is to be cleaned off all the surface of all the teeth, 
 additional means of so doing must be employed. Up to the present 
 time nothing is known that will accomplish this more efficiently and 
 harmlessly than the floss silk and a mouth wash of lime water. 
 
 Floss Silk. — If the floss silk is skilfully and frequently used, the 
 approximal surfaces may be kept quite free from dental caries. To 
 induce patients to use the floss silk with regularity is a task, but by 
 being persistent in requesting and logical in the reason for its use, they 
 may be made gradually to acquire the floss habit. To insure the proper 
 use of the floss the fillings in the approximal surfaces should be smooth 
 
POLISHING 
 
 289 
 
 and polished, with just sufficient pressure at the contact points to allow 
 the floss to snap through without too much effort in forcing it. The 
 patient should be instructed not to allow the floss to snap through on 
 
 Fig. 214 
 
 the gum tissue hard enough to wound it. There is but little danger 
 of this after practice, especially af-^n the gums have become hard and 
 
 Fig. 215 
 
 tough from brushing. A reasonably small-sized waxed floss is the best 
 to use. For adults the piece should be fourteen or fifteen inches in 
 length. The end of the floss is taken between the thumb and first 
 19 
 
290 
 
 DENTAL PROPHYLAXIS 
 
 finger of the left hand and two wraps made around the end of the first 
 finger, and this act repeated with the other end of the floss on the 
 right forefinger. The floss is now held securely and will permit the 
 
 Fig. 217 
 
POLISHING 291 
 
 ends of the two thumbs or the two second fingers or a coml)ination of 
 a thumb of one hand and a second finger of the other, to guide the silk 
 into its position in the mouth and force it between the teeth. Fig. 
 213 shows adaptation of floss for right upper teeth. Fig. 214 shows 
 adaptation for left upper teeth. Fig. 215 shows adaptation for all 
 the lower teeth. After the floss has passed through the contact points 
 it should be rubbed back and forth against both approximal surfaces 
 to polish them mechanically. In withdrawing the floss, if the end held 
 opposite the lingual surface is brought over on the buccal surface and 
 the silk is pulled through the contact points in the form of a loop, it 
 will be more effective in polishing or cleaning these surfaces than if 
 merely snapped out (Figs. 216 and 217). The floss will not, however, 
 thoroughly remove all the food between the teeth, therefore we must 
 have recourse to a mouth wash. 
 
 Lime-water. — Practically all the mouth washes on the market are 
 formulated to accomplish two results: First, a neutralizing action, 
 either acid or alkaline, and second, a germicidal action. It will readily 
 be understood that the latter result cannot be obtained in the mouth, 
 while the former is immaterial. In order to secure immunity to decay, 
 the bacteria must be robbed of any pabulum upon which to feed and 
 any plaques or glue-like accumulations on the surfaces of the teeth 
 must be dissolved. 
 
 Acid mouth washes have been advocated because it has been found 
 that the lactic acid forming bacteria*4/e retarded in their growth and 
 activity in an acid medium. Alkaline washes have been prescribed 
 because of the belief that they will neutralize any lactic acid formed 
 that will induce caries. Both of these theories are based on partial 
 facts only, for it has been absolutely proved that the chemical action 
 of an acid or an alkali used as a mouth wash for neutralizing purposes 
 will not inhibit dental caries to any great degree. All of these washes 
 are supposed to contain germicides that will imimediately destroy the 
 microorganisms of the mouth. This is of course untrue, especially 
 when the short time they are retained in the mouth for this purpose is 
 considered. The peroxide of hydrogen is religiously used by many, 
 in the belief that the oxygen liberated is a germicide of sufficient power 
 to destroy all the bacteria. The mechanical action of the peroxide in 
 its boiling process, while it does liberate the oxygen, is more effective 
 in dislodging particles of food debris around the necks of the teeth than 
 in its germicidal action on the organisms in the mouth. In the study 
 of dental caries it must be concluded from the present knowledge of the 
 subject that in the main Professor Miller's theory still holds good, 
 namely, that the exciting cause is due to the production of lactic acid 
 by the action of microorganisms on carbohydrates, and that decay 
 takes place most readily on those surfaces least exposed to friction 
 during mastication, such as the fissures or pits, approximal surfaces, 
 and the necks of the teeth. Dr. J. Leon Williams was the first to point 
 out the fact that a thin gelatinous plaque was first formed on the 
 
292 DENTAL PROPHYLAXIS 
 
 surface of the enamel and under and in this thin film the bacteria 
 obtained a secure position that made their dislodgement difficult. 
 Their action in the production of acid was intensified when thus 
 protected. Other scientific investigators have corroborated Williams' 
 observations. Laying aside any theories regarding susceptibility and 
 immunity, it must be admitted that the battle just now should be the 
 thorough removal of all food debris and the removal of these plaques 
 and glue-like accretions. 
 
 The mucin, which is a product of the salivary and mucous glands, 
 plays an important part in the formation of these plaques, and it is 
 precipitated from the secretions in the mouth by the presence of an 
 acid. This precipitate forms on the surfaces of the teeth and becomes 
 the factor in incasing the bacteria with food debris and in forniing the 
 so-called plaques. Mucin thus precipitated is soluble in or may be 
 dissolved by an alkali. It has been found that the presence of fruit acids 
 in the mouth stimulates the salivary secretions in amount and alkalinity. 
 It is claimed by some investigators that the increased alkalinity of the 
 saliva has a solvent action on the precipitated mucin and a neutralizing 
 action on lactic acid and thus becomes a natural preventive of dental 
 caries. Other investigators have as yet been unable to find that the 
 alkalinity so produced is of sufficient strength to have this solvent 
 action. Again, it is claimed that the acids of fruits have a curdling 
 effect on the mucin, forming it into flakes which are easily removed 
 from the tooth surfaces. ^ 
 
 There is a serious question concerning the habitual use of these 
 acids for this purpose. Prinz states, as his opinion, that the correct- 
 ness of the use of acid mouth washes is not substantiated by clinical 
 experience, that the pharmacological principle evolved in the selection 
 of such solutions is erroneously applied, that constant forcible stimula- 
 tion of the salivary glands by acids is followed by an impairment of 
 glandular function and that the acidity of the solution kills the im- 
 portant salivary ferments. A reasonable amount of fruit is healthful 
 and desirable, but dentifrices and mouth washes containing fruit acids, 
 must be used with considerable judgment. 
 
 The most cleansing and the least harmful of all fruits is the apple. 
 This with its dense texture acts as a mechanical cleanser, and the malic 
 acid is comparatively harmless. Where it is impossible to have 
 access to a tooth-brush the eating of an apple will be found an excellent 
 substitute. 
 
 If it can be scientifically shown that dentifrices and mouth washes 
 containing fruit acids in certain proportions are harmless to the teeth 
 and the tissues of the mouth and are superior to any of the present-day 
 preparations as prophylactic agents for dental caries, it would prove 
 to be a valuable contribution to dental prophylaxis. 
 
 As it will take a number of years to demonstrate this as a fact it will 
 be necessary for the present to adhere to those agents that have proved 
 themselves to be harmless and efficient in the past. 
 
POLISHING 
 
 293 
 
 There is a harmless solvent for the mucin on the surfaces of the teeth 
 that is quite positive in its action. This solvent is lime-water, and is 
 made from the coarse calcium oxid or unslaked lime. Its preparation 
 is simple and cheap, and when its efficiency for the use and purpose 
 intended is considered, it will rank as an important agent for the pre- 
 vention of dental caries. 
 
 Some coarse lime, such as is used in making rough plaster, may be 
 secured from a paint store or from a mason. The refined product 
 found in the drug-stores apparently does not have the same effect. 
 The refining process robs it of some of its beneficial properties. It is 
 cream white in color. The lumps should be broken up into coarse 
 powder and a half-cupful put into a quart bottle. The bottle should 
 be nearly filled with cold water, room enough being left to permit of 
 
 Fig. 218 
 
 thorough shaking, shaken vigorously and set aside for three or four 
 hours to allow the lime to settle. Then as much of the clear water as 
 possible should be poured ofP, for this contains the washings of the 
 lime. It will be found impossible to pour off all the water without 
 losing some of the lime, but by pouring slowly nearly two-thirds 
 may be drawn off. The bottle can then be filled with cold water 
 and shaken thoroughly, when, after it has settled again, it will be 
 ready for use. A bottle of convenient size should be procured; one 
 holding ten or twelve ounces, and filled with the clear water from the 
 large bottle. This smaller bottle will be more convenient to use at 
 the bowl. The large bottle can be again filled with cold water, shaken 
 thoroughly and set aside to be used as needed (Fig. 218). This 
 operation may be repeated over and over again, for the original half- 
 cupful of lime will make five or six quarts of lime-water. If the first 
 
294 DENTAL PROPHYLAXIS 
 
 use of the wash proves that it is a little strong, it can be diluted in the 
 small bottle. With new patients and those having tender gums it may 
 have to be diluted, but as soon as possible it should be used undiluted. 
 When taken into the mouth it should be forced back and forth vigor- 
 ously between the teeth with the tongue and cheeks and the rinsing 
 continued until it breaks into a foam. Not that there is any particu- 
 larly beneficent action to the foaming," but if it is worked through the 
 teeth long enough to make the foam it will have been in contact with 
 the surfaces of the teeth long enough to have a disorganizing action 
 on the mucin and plaques. Afterward the mouth should be thor- 
 oughly rinsed with warm water to take away the taste of the lime- 
 water. It is the unpleasant taste of the lime that makes it difficult to 
 induce the patients to use it at the start, but after a short time the 
 cleansing effect is so pleasing that they soon forget about the taste. 
 It may be flavored with saccharin or any flavoring material, but this 
 will hardly be found necessary. The lime-water should be used after 
 the brushing and flossing, after each meal. 
 
 Diet. — The greater part of this chapter has been devoted to a detailed 
 description of the operative procedure for dental hygienists to follow 
 and the instructions for home care of the mouth which she is to teach. 
 
 It must not be assumed that the foregoing is, therefore, the most 
 important part of dental prophylaxis. On the contrary, the hygienist 
 will find by experience that, despite the most conscientious effort on 
 her part, there will be mouths ilf which dental caries is never under 
 control. In these cases it will be found that the diet is such as to 
 counteract the most painstaking care on the part of the patient and 
 hygienist. It may be truthfully stated that, aside from the influence 
 of heredity, the controlling factors in mouth health are diet and extreme 
 cleanliness. 
 
 The most important study of the dental hygienist should be that of 
 foods, and the influence which she can have on mothers and children 
 in this respect will be her most important educative service. The 
 subject of foods must be studied in great detail, and it is possible 
 in this chapter to mention only the most salient points regarding the 
 relation of the dietary to the teeth. 
 
 During infancy and childhood, the important single substance for the 
 growth of bones and teeth is calcium phosphate, and the amount of 
 calcium available for tooth formation regulates whether the enamel be 
 hard and dense or relatively soft and porous. The influence of diet 
 and its relation to the teeth must therefore begin with pregnancy. 
 Before birth and for some time thereafter, if the infant is nursed at the 
 breast, the high calcium requirement of infancy is supplied by the 
 mother. Her calcium requirements are consequently increased, and 
 unless extra lime is present in her diet, her teeth and skeleton may 
 suffer. Milk, which is a perfect food, contains all the necessities for 
 infant growth, but when milk ceases to be the sole article of food, 
 the new diet is most important. Especial emphasis should be placed 
 
POLISHING 295 
 
 on foods that are high in calcium content as soon as the temporary 
 teeth have erupted. Some of the most important of tiiese foods are 
 milk, buttermilk, cheese, celery, spinach, turnips, radishes, string beans, 
 parsnips, carrots, kidney beans, cabbage, cauliflower, onions, etc. 
 It is also present in the various whole grains and it is well to note 
 that the more highly refined the grain is, the less calcium it contains. 
 
 Alfred W. McCann, in his book This Famishing World, says: "The 
 unrefined grain of wheat as it comes from the field contains in organic 
 form the twelve mineral substances needed for the health, growth and 
 life of the body. White bread becomes white because from the ground 
 grain of wheat three-fourths of the mineral salts and colloids, including 
 the salts of calcium, phosphorus, iron, potassium, chlorine, fluorine, 
 sulphur, magnesium, manganese, etc., are removed. These mineral 
 substances are contained in the brown outer skin, the cells underneath 
 this skin and the germ of the wheat berry. They are sifted and bolted 
 out of the ground meal, leaving behind the white, starchy cells and the 
 refined gluten of the interior part of the berry." 
 
 All of our cereal foods, such as rice, corn and oats, are demineralized 
 during a refining process which should never be permitted. The 
 hygienist has a mosi important duty in educating people in the use of 
 natiu-al refined grains. 
 
 Inorganic calcium is present in drinking water and in lime-water 
 and can be absorbed from them ir^ mall quantities. It is interesting 
 to note, however, that a quart of milk contains more absorbable 
 calcium than a quart of clear saturated lime-water, and that milk 
 used freely as food in youth is the most practical means of insuring 
 an abundance of calcium in the dietary. The diet depends so much 
 upon the digestive capacity of the child, that in some cases calcium 
 is not utilized correctly because of some digestive disturbance. The 
 most common is that caused by the ingestion of too much sugar which 
 frequently causes digestive disturbances unfavorable to the absorption 
 of the necessary amounts of calcium. 
 
 McCann says: "Sugar and calcium possess a remarkable affinity 
 for each other. When refined sugar or glucose, both of which are 
 mineral-free and, therefore, like distilled water, mineral-hungry, are 
 consumed in generous quantities they attack the soluble calcium 
 of the tissues. The tissues retaliate in turn by sapping the calcium of 
 the blood. The blood, which demands a minimum calcium content, 
 with never relaxing energy, steals calcium from the teeth and bones. 
 The experiments of Voit and others prove this. Children will suffer 
 and prospective mothers decline as long as they consume an excess of 
 refined or denatured, mineral-free sugar, glucose and starch in their 
 diet or as long as food industries continue to remove the soluble mineral 
 elements from the chief sources of their food supply." 
 
 In fact when the diet of the average American child is considered, 
 it is not so astonishing to find that dental caries is a universal 
 malady. Originating as it does from carbohydrate fermentation upon 
 
296 DENTAL PROPHYLAXIS 
 
 the teeth, no other result could be expected among the children of 
 a nation averaging nearly one hundred pounds of sugar per capita 
 per year. The writer personally believes that in childhood, a well 
 balanced diet, with special emphasis upon the calcium content foods, 
 and the elimination of free sugar would result in practical immunity 
 from dental caries, even in the absence of a rigid system of mouth 
 cleanliness. The causes of susceptibility and immunity are still 
 under investigation, but it is reasonable to believe that suscep- 
 tibility is mainly in proportion to the consumption of free sugar, and 
 that immunity is acquired, in a great measure, by the absence of 
 free sugar in the dietary. When it is considered that dental caries 
 can only be produced from starch and sugar, and that the starch must 
 be reduced to dextrose before it can be converted into lactic acid, it is 
 quite truthful to make the statement that all dental decay is produced 
 by sugar. Clinical experience and general observation seem to show, 
 however, that the high consumption of starchy food, if unaccompanied 
 by free sugar does not result in dental decay. In fact the evidence is 
 all against the sugar. Among the peasant classes of Italy, Greece, 
 the Balkan States, Germany, and others where the diet consists mainly 
 of coarse foods, vegetables and fruits, but where free sugar is a luxury 
 and cannot be indulged in, decayed teeth are the exception and not 
 the rule. This is also true of the Esquimos, the African Negroes, the 
 American Indians, the Maoris of !)4^w Zealand, and many of the South 
 Sea Islanders. 
 
 Free sugar consumption in Italy averages but thirteen pounds 
 per capita per year — less than a teaspoonful a day. The American 
 mother would be inclined to question an average of about one hundred 
 pounds per capita per year in this country, but few realize the enormous 
 amount used weekly in the average home for cooking alone, not to 
 mention the quantity utilized in preserving fruits. 
 
 The medical profession is, to a great extent, responsible for this 
 situation, for the family physician has taught mothers to believe that 
 free sugar is an essential food for growing children. Under the existing 
 conditions what chance h,as an American child to have sound teeth? 
 If he is a modified milk baby, sugar is added to the milk, in the pro- 
 portion of one ounce in twenty, at only a few weeks after birth, and all 
 too frequently cane sugar takes the place of milk sugar. The taste 
 and craving for sweetened foods is developed at once and is steadily 
 encouraged as he progresses to cereals with sugar, puddings, jellies, 
 sweetened crackers, etc. To the normal sugar supply found in milk, 
 vegetables and fruits, and in the conversion of starchy foods, is added 
 an ever increasing amount of free sugar at meal time, augmented 
 between meals by sqda water, ice-cream and candy. The sugar con- 
 sumption is so excessive that the liver is overloaded with glycogen and 
 it is verypossible that herein lies the secret of the child's susceptibility; 
 not only in the fermentation of the sugar on the tooth, but also in the 
 action of osmotic forces through the enamel with the blood and body 
 
POLISHING 297 
 
 juices which are surcharged with glucose and the absorbed products of 
 fermented surplus glucose from the intestines. There can be but one 
 result; the deciduous teeth are attacked by dental caries, and at the 
 beginning of his school life the child presents a wrecked mouth and it is 
 only a matter of time before the permanent teeth are similarly affected. 
 
 And so the medical profession, by advocating free sugar as part of 
 the diet, is constantly creating a disease known as dental caries which 
 demands a specialty known as dentistry. Dentistry, in turn, has 
 filled, crowned and capped these decayed teeth in innocence and 
 ignorance of the bacterial colonies which exist on the ends of the roots 
 of pulpless teeth, causing secondary infections of the heart, kidneys, 
 joints and other organs and tissues of the body, thus returning the 
 compliment to the medical profession by creating thousands of cases 
 of systemic infection to be given over to its care and treatment — with 
 the public as the victim. Neither the medical nor the dental profession 
 has realized that this vicious circle existed, but no great reduction can 
 be made in dental caries and resultant systemic infections until this 
 circle is broken. 
 
 The dental hygienist must be the one to break this circle, by teaching 
 American mothers who have for generations been educated to look upon 
 free sugar as a food, that free sugar is the chief cause of dental decay 
 and that dental decay is the chief cause of many of the serious illnesses 
 of childhood and adult life. Until the time comes when these truths 
 are generally recognized, the effort must be made to counteract the 
 evil effects of a faulty diet by a rigid system of mouth cleanliness to 
 lessen the carbohydrate fermentation. The sugar consumption has 
 increased amazingly during the past forty years, and if dentistry, as a 
 science, had not advanced so rapidly during the same period, ruined 
 mouths would be even more prevalent. 
 
 The soft pappy foods, which very often constitute the bulk of the 
 diet of younger children, require so little mastication as to seriously 
 hamper the normal development of the jaws, face, and even the brain 
 case itself. It may also be well to mention the deleterious effect on 
 the enamel of the teeth, of skin diseases, especially if contracted during 
 early childhood. It is very important to instruct mothers that the 
 enamel is formed from cells similar to those of the skin and that any 
 eruption or rash of the skin is likely to produce a deleterious effect upon 
 the formation of the enamel, if it occurs during the formative period. 
 
 Every precaution should be taken to prevent a child from contracting 
 measles, chickenpox, scarlet fever, etc., especially from birth to about 
 fourteen years of age during which period the enamel of fifty-two teeth 
 is formed. 
 
 It is quite common to see teeth with an enamel surface that is pitted 
 or grooved, and in many cases as much as half of the crown of a tooth 
 will be minus any enamel due to some skin disturbance during its 
 formation. Enamel somewhat similar in appearance can also be pro- 
 duced by any severe nutritional disturbance. It is practically impos- 
 
298 DENTAL PROPHYLAXIS 
 
 sible to prevent the decay of this defective enamel, and any rash or 
 eruption should be avoided for this reason. 
 
 General Comments, — One prophylactic treatment does not con- 
 stitute prophylaxis. It is only by a systematic, continuous course of 
 treatment and home care of the mouth that ideal health conditions 
 can be secured. 
 
 Preventive dentistry can be had quite cheaply and is within the 
 reach, financially, of nearly everybody. Good operative dentistry is 
 expensive and always will be, as is surgery or the services of any 
 educated and skilful specialist. 
 
 Education and prevention is the only hope of solving the dental 
 problems for the masses and as time goes on this service will be found as 
 necessary a form of insurance for health as life insurance is for the 
 protection of those left after one dies. 
 
 When the public really becomes educated to the fact that for the 
 expenditure ot a very moderate sum of money and a little energy on its 
 part, the teeth may be retained throughout life quite free from pain and 
 disease, there will be a great demand for this form of service. Every 
 mouth would be greatly benefited if prophylactic treatments could be 
 administered every two months. Many mouths require monthly 
 treatments, especially those of children and adults who are susceptible 
 to caries. 
 
 In the search for some easy sob^tion of the problem of dental decay 
 many ideas are advanced for its ultimate control, and it is expected 
 that a simple method of doing away with this great disease-producing 
 disorder will be found. There may come a time when a lozenge will 
 produce immunity but that time is not in sight as yet. As long as 
 people live artificially, as most people do, eating the various concoc- 
 tions called ''food" that they feel free to eat at the present time, the 
 one hope of escape from the ill-effects of dental decay and its attending 
 serious effects on the body is through the present knowledge of extreme 
 cleanliness, or mouth hygiene. Until something can be presented more 
 definitely simple that will show equally beneficial results, it will be 
 necessary to adhere to the form of prophylaxis herein advocated. 
 
APPENDIX. 
 
 THE BROAD FIELD OF SERVICE OF THE DENTAL HYGIENIST. 
 
 The educational and preventive service of the dental hygienist has 
 been covered in detail under Dental Prophylaxis, and it remains to 
 state the broad field to which such service may be applied. 
 
 It has long been realized that the dental profession was unable to 
 cope with the universal need for mouth hygiene, the number of dentists 
 available at any one time being always insufficient to supply even the 
 need for good operative dentistry. With dental diseases and resultant 
 systemic infections almost universal maladies, trained workers for 
 maintaining mouth 'health can no longer be denied to a public sorely 
 in need of such service. The dental hygienist was created from the 
 realization that mouth hygiene was a necessity, that the average dental 
 practitioner could not give the necessary time to it, and that the tooth 
 brush alone would never produce it. 
 
 Fortunately it does not require a graduate dentist to perform a 
 prophylactic treatment of the teeth or to teach mouth brushing, food 
 habits, and general hygiene. The present need of the dental profession, 
 in solving the public health problem of mouth hygiene, is an immense 
 corps of women workers, educated and trained as dental hygienists, 
 and therefore competent to enter dental offices, infirmaries, public 
 clinics, sanatoriums, factories and other private corporations, to care for 
 the mouths of the millions of adults who need this educational service 
 so urgently. The need in every state is so great that every state must 
 provide its own training schools, and if the dental profession will not 
 meet the situation, the state health or educational authorities must do 
 it. This is the only sane and logical method by which any help can be 
 provided for the adult population, with the almost hopeless mouth 
 conditions which now prevail. The damage has already been done 
 and there are not enough dentists to restore the lost tooth structure in 
 one-fifth of these mouths. There is, however, a service that the dental 
 hygienist can give in correcting the uncleanliness and in educating for 
 the prevention of further disease. ~~ 
 
 THE DENTAL HYGIENIST IN PRIVATE PRACTICE. 
 
 The service of the dental hygienist in the private offices of graduate 
 dentists is quite apparent, and much of the detail given under Dental 
 Prophylaxis applied directly to this particular field of service. The 
 
300 . APPENDIX 
 
 following system is offered as one that has been found to be practical 
 and productive of splendid results. 
 
 A System for Prophylaxis in Private Dental Practice. — First, a new 
 patient is given two appointments, a week or ten days apart, with the 
 dental hygienist, for a thorough instrumentation and polishing of the 
 teeth. At the end of the first sitting he is supplied with a tooth brush, 
 dentifrice, floss silk and lime-water for a mouth wash, taken to a wash 
 bowl and taught how to properly brush teeth and gums, and given full 
 instructions in the home care of the mouths As it is now realized that 
 a visual examination of the mouth is very superficial an appointment 
 is reserved for the radiographing of the entire mouth. At the end of 
 the second sitting, one-half hour is reserved for him with the dentist 
 for a thorough chart examination of the mouth and diagnosis of the 
 radiographs. Appointments are then arranged, surgical instrumenta- 
 tion given if necessary, and the teeth restored to a sound condition. 
 At the end of the last appointment the dentist gives the patient another 
 thorough prophylactic treatment. 
 
 The patient is then put on a list and sent for each month for a treat- 
 ment by the dental hygienist. At the end of six months he again goes 
 into the hands of the dentist for an examination of the teeth and gums 
 and a surgical instrumentation if necessary.' If the condition of his 
 mouth warrants, the interval between the treatments is now lengthened 
 to six weeks. At the end of the next, six months he again goes through the 
 dentist's hands and if good moutlf health is attained his name is placed 
 on a two months' list and he is given treatments by the dental hygienist 
 at these intervals, going into the dentist's hand for every third treat- 
 ment, or once in six months. Patients whose teeth are very susceptible 
 to dental caries, such as children and young people, should be retained 
 on the monthly or six weeks' list. 
 
 When the patient's mouth has been put in order and his name placed 
 on one of the lists to be sent for at regular intervals, his name is also 
 entered in the appointment book against the date when his next 
 appointment for a prophylactic treatment falls due. A week previous 
 to this date the patient is notified of the appointment by means of a 
 return card system. This consists of an appointment card bearing the 
 name of the patient and date and hour of his appointment, a retu'rn 
 card bearing the same date, and a stamped return envelope. If the 
 date designated proves convenient, the patient signs the return card 
 and returns it in the enclosed envelope and the appointment is checked 
 in the appointment book. If not convenient, a new appointment is 
 made. The various lists of patients — monthly, six weeks, and two 
 months — are kept by means of a card index file. In the writer's 
 practice this system has been compulsory, and has shown very favorable 
 results in the prevention of dental caries and pyorrhea alveolaris. It 
 may also be mentioned that the system has proved to be a financial 
 saving of 60 per cent, to the patients. 
 
MUNICIPAL DENTAL CLINICS 301 
 
 HOSPITALS AND SANATORIUMS. 
 
 The relation of pathological mouth conditions to systemic diseases is 
 now so definitely known, that hospitals and sanatoriums will bie forced 
 to establish a dental division for the radiographing, diagnosing, and 
 sanitation of the mouths of all patients. The sanitation of the mouth 
 will necessitate the services of dental hygienists who can operate at the 
 bedside, if necessary. Such a procedure is already being followed in 
 some hospitals and sanatoriums with most gratifying results. 
 
 INDUSTRIAL DENTAL CLINICS. 
 
 One of the most important branches of dental hygiene is that which 
 may be provided for the great working classes who need sound teeth 
 for good health, but for whom, until the present time, there has been 
 no provision in dentistry. These are the people who constantly suffer 
 from systemic disturbances due to diseased teeth, yet scientific dental 
 operations are out of their reach. Fortunately preventive dentistry and 
 education for mouth health can be placed within the reach of all. The 
 economic value of educational, preventive and diagnostic dental clinics 
 in connection with large industries has been shown to be the most 
 fruitful form of welfare work for employees. 
 
 A working plan for the industrial clinic is suggested as follows : The 
 size of the corps is dependent upo:^^ the number of employees in the 
 industry.. A unit for one thousand employees should include one 
 dentist, two dental hygienists and a radiographer. The service is 
 limited to prophylactic treatments, instructions in the home care of 
 the mouth, visual and radiographic chart examinations of the entire 
 mouth, and the relief of pain. When the condition of the mouth is 
 charted, a copy is given the patient, and he is advised to visit his own 
 dentist for the elimination of mouth infection and for restoration of lost 
 tooth structure. 
 
 The serious illnesses of many valuable employees could thus be pre- 
 vented, and industries would find such a welfare clinic a very profitable 
 investment. 
 
 MUNICIPAL DENTAL CLINICS. 
 
 High grade professional service, whether it be medicine, dentistry 
 or law, must be considered as a luxury to the great mass of wage-earning 
 people in cities, and one which they cannot afford. This is especially 
 true of good dentistry. Cheap dentistry is apt to be more harmful 
 than beneficial, for if the operations on the teeth are performed hastily 
 and in an unscientific manner, serious complications may develop 
 within the body, due to bacteria gaining entrance through the roots of 
 the teeth or through the soft tissues which surround them. 
 
 There are hundreds of families in cities whose income is not suf- 
 ficiently large to aft'ord the services of a good dentist and ^^t they 
 
302 APPENDIX 
 
 would like to save their teeth if possible. Decayed and diseased teeth 
 produce much sickness and lower the efficiency and endurance of the 
 workers. This becomes a serious health problem and must be met in 
 a practical manner. Charity, which gives something of value for 
 nothing, is not conducive to character building or good citizenship, and 
 he who accepts it should be in desperate need of aid. 
 
 When the administrators of municipalities realize these facts they 
 will establish municipal dental clinics accessible to the wage-earner 
 and his family, especially the children. It would not be the intention 
 of such a clinic to give free dental service, except for the relief of pain 
 to those who are too poor to pay for it, but to establish a clinic where 
 first-class dentistry might be secured at a very moderate cost and be 
 within the means of all whose incomes are too small to enable them to 
 go or to send their children to a dentist in private practice, a movement 
 to help those who are willing and anxious to help themselves. 
 ^ The dental hygienist has her field of service in this type of relief 
 and repair clinic, where she may restore unsanitary mouths to a clean 
 and wholesome state by operative procedure as well as education in 
 home care. 
 
 EDUCATIONAL AND PREVENTIVE DENTAL CLINICS FOR 
 SCHOOL CHILDREN. 
 
 The efiiciency of dental hygieniits in carrying out educational and 
 preventive measures as a part of the scKool curriculum has been 
 demonstrated for six years in Bridgeport, Connecticut, and it is felt 
 that the results secured would be of sufiicient interest to warrant the 
 following detailed report of this work. 
 
 I 
 REPORT OF FIVE YEARS OF MOUTH HYGIENE IN THE PUBLIC 
 SCHOOLS OF BRIDGEPORT, CONN.^ 
 
 By Alfred C. Fones, D.D.S. 
 
 In presenting a report of the findings of a five-year demonstration of 
 an educational and preventive dental clinic in the first five grades of the 
 public schools of Bridgeport, Conn., it is interesting to review the 
 reasoning and deductions by which the plan was perfected. Previous 
 to the establishment of the clinic in 1914, a paper entitled "A Plan 
 that Solves the Fundamental Problem in School Hygiene," was read 
 by Dr. Alfred C. Fones, of Bridgeport, Conn., before the Fourth 
 International Congress on School Hygiene, in Buffalo, August 26, 
 1913. In it the author summed up in a short article the physical 
 status of the average school child and the problem of the unsanitary 
 condition of his mouth, and evolved a plan for its solution. At that 
 
 1 Read before the Convention of the Connecticut Dental Hygienists' Association, 
 Bridgeport, Conn., May^24, 1919. 
 
MOUTH HYGIENE IN PUBLIC SCHOOLS 303 
 
 period little was known of focal infections, which have proved to be 
 a greater evil than anything yet recognized as traceable to decayed 
 teeth. The paper makes a logical introduction to this report and is 
 presented in full as follows: 
 
 Dr. Fones' Plan Proposed in 1914. — "To analyze the subject of 
 hygiene for the upliit and betterment of the children in our public 
 schools, we must determine what are the main factors existing at 
 present that act as a detriment to proper development and also as the 
 chief cause of illness in child life. 
 
 " The large number of papers presented at this congress, covering so 
 many phases of the subject, merely proves that we must reach a con- 
 clusion, first as to where we should concentrate our energy, and then 
 one step at a time eliminate the most conspicuous evils that beset the 
 school children of our country. 
 
 "If our large steel plants and rolling mills were obliged to reroll from 
 twenty to thirty-five per cent, of their stock, it would not take them 
 very long to find out what was the matter. No business nowadays 
 could stand such a high percentage of loss in doing its work over again. 
 
 " In our public schools throughout the country it is a fair estimate 
 to say that the percentage of grammar school children who are review- 
 ing their grades will range between twenty and thirty-five per cent. In 
 a majority of the cities the average would be nearer the latter figure. 
 What is the matter? Is it our system of teaching, crowded schools, 
 poorly lighted or ill-ventilated buildj^ngs, or is the chief cause to be 
 found in the material itself — the child ? 
 
 "Let us examine the average boy of ten years of age and see what 
 we find. Face, ears and nose unclean, hair unkempt, hands grimy and 
 finger-nails dirty. Shoes splashed with dry or wet mud, clothes soiled, 
 and an odor percolating through the atmosphere to excite suspicion 
 that his little body has not been washed for some time. His eyesight 
 may be good and yet it may be defective. If his face is washed it may 
 disclose a color that is lacking in the bloom that a boy of ten should 
 have. 
 
 " If otherwise his body appears normal we ask him to open his mouth. 
 If his external appearance troubles us, his internal appearance would 
 shock us. Here we find teeth covered with green stain; temporary and 
 permanent teeth badly decayed, possibly fistulae on the gum surface 
 showing outlets for pus from an abscessed tooth or teeth, and decom- 
 posing food around and between the teeth. Why examine the child 
 any further ? Here at the gateway of the system is a source of infection 
 and poison that would contaminate every mouthful of food taken into 
 his body. With decomposition instead of digestion taking place in the 
 alimentary tract, it is no wonder that the child suft'ers from an auto- 
 intoxication which produces eye-strain, anemia, malaise, constipation, / 
 headaches, fevers and many other ailments. 
 
 "Such a mouth is an ideal breeding ground for germ life, and a 
 child with such a mouth is far more susceptible to infectious diseases 
 
304 APPENDIX 
 
 than one whose teeth are sound and kept free from food debris. Sup- 
 pose at the entrance of our cities such a rank condition existed. How 
 long would it be before disease and sickness would be swept in among 
 the inhabitants? This boy described is but duplicated in the girl of 
 ten. Decayed teeth constitute the most prevalent disease known. It 
 is difficult to find two children out of one hundred with perfectly sound 
 sets of teeth. In a thorough dental examination of five hundred and 
 fifty school children in the town of Stratford, Connecticut, but one child 
 was found to have a set of teeth free from decay. 
 
 " Look over the reports of the medical inspectors in the public schools 
 who have made but a glancing examination of the mouths, and you will 
 find that decayed teeth outrank all other physical defects combined. 
 
 " Therefore we must deduce from our analysis of school hygiene that 
 the most conspicuous defect of the child is the unsanitary condition of 
 his mouth. Like a pig pen or garbage drain, slowly seeping its poison 
 into the brook, which, flowing into the reservoir, contaminates the water 
 supply to a city, so do the products of abscessed and decayed teeth with 
 decomposing food slowly but surely poison the human system. Such 
 mouths and teeth breed disease. Such children cough and sneeze 
 millions of germs made virulent and active in an ideal feeding ground. 
 And then again the teeth as a crushing and masticating machine are fre- 
 quently ruined by the time the child has reached twelve or fourteen 
 years of age. It is true that they can limp through life with this dread- 
 ful handicap, the same as an autojnobile can climb a steep hill on three 
 cylinders, but you can rest assured that the child with a wrecked mouth 
 at fourteen is traveling on his second speed until he reaches thirty-five, 
 and from there he drops into his low gear to finish the journey in a 
 slow and uncertain state. It is true that many have lived to a ripe old 
 age with unclean mouths and wrecked teeth, not on account of such 
 conditions, but in spite of them. 
 
 "If it be conceded that the most unhygienic feature of child life is 
 its mouth we then come to the problem — how can we establish clean 
 mouths, sound teeth and the tooth-brush habit? To try and fill the teeth 
 of the children in our public schools is a noble charity, but an endless 
 chain. Like an immense flood, decayed teeth have spread over the civ- 
 ilized world to such an extent that hardly one- tenth of the population 
 of a country such as ours could find a sufficient number of dentists to 
 fill its teeth. I believe it to be a conservative estimate to say that the 
 children found in the first five grades in our public schools would aver- 
 age not less than six^ good-sized cavities in their teeth. If you will 
 but figure out how many children there are in your city in the first five 
 grades, you can roughly estimate the immense amount of work there 
 would be for a corps of dentists to cope with such a task as filling 
 their teeth. This would not mean merely plugging a hole in a piece of 
 ivory; it means the painstaking work of a dental operation on live tissue. 
 
 1 Later findings showecJ seven — plus. 
 
MOUTH HYGIENE IN PUBLIC SCHOOLS 305 
 
 "But let us assume that it is possible to fill these teeth and save them 
 for the time being, how are we to prevent a re-occurrenee of decay as 
 well as to check the flood with the children coming into the schools in 
 the primary grades each year? Surely every dentist knows that the 
 tooth brush alone will not stop it, and every dentist also knows, as well 
 as the parent, how difficult it is to induce children to properly brush 
 their teeth and take care of their mouths as they should. Would it not 
 be better to evolve a system for the prevention of dental decay and the 
 establishment of clean mouths than try to cope with the hopeless task of 
 filling the thousands of decayed teeth? I am heartily in sNiiipathy 
 with the scheme that every city should have a dental clinic for the school 
 children for the relief of pain, and I believe it is inhuman in this 
 twentieth century to allow the poorer class of children to suffer as they 
 do from toothache. But let us draw a line on the conditions as they 
 exist today, and I would present this plan, partly suggested by Dr. 
 Ottolengui, of New York, for your consideration. 
 
 "It is a clinical fact that fully eighty per cent, of dental decay can 
 be prevented, if monthly or even bi-monthly surface polishing of the 
 teeth with orange wood sticks and fine pumice can be systematically 
 followed. These treatments, of course, to be augmented by the faithful 
 and correct use of the tooth brush, floss silk and lime-water as a moi^th 
 wash. 
 
 "Suppose it were possible to start a year from this September and 
 place in our schools trained women who would confine their efforts the 
 first year to the children in the first grade. These w^omen to be trained 
 and educated as hygienists who would be competent to give each child 
 a surface treatment of the teeth once a month ; each woman to have the 
 supervision, to start with, of two hundred children; these children in 
 the first grade to be taught the proper use of the tooth brush, mouths 
 inspected daily for cleanliness, and no child permitted to enter the class 
 room who had not brushed his teeth. Hands and face to be clean 
 and hair combed. Bodily cleanliness also insisted upon and efforts 
 made to secure the cooperation of the parents. Talks in the class room 
 as well as the use of the stereopticon in the assembly room would greatly 
 aid in securing the desired results. These hygienists could also be of 
 great aid to the medical inspectors. At the end of the year they would 
 follow the children into the second grade and a new corps of hygienists 
 would enter the first grade with the new pupils; this to be repeated for 
 five years, until the first corps of women were caring for their children 
 in the fifth grade. It is doubtful if it would be necessary to carry this 
 work beyond th,e fifth grade, as the child would be cared for through 
 the most susceptible period for dental decay. 
 
 "Now what would such a system mean to the children? It would 
 m§an that from the first day that the child entered school it would be 
 taught cleanliness. That when the first permanent tooth entered the 
 mouth it woukl be under the supervision of the hygienist, who would 
 teach the child how to keep it clean and who would also aid with the 
 20 
 
306 APPENDIX 
 
 monthly polishing. It would mean that during the first five years of 
 school life habits of cleanliness would be established that would mold 
 these boys and girls into new types of men and women. Fully three- 
 quarters of the diseases incident to child life would be eliminated. With 
 an additional knowledge of food values and how to properly masticate 
 their food instead of bolting it, the main factors for hygiene would 
 be covered. 
 
 " Booker Washington once said : ' If I can teach the colored man the 
 gospel of the tooth brush, I feel that I can make a man of him.' Those 
 of you who see but little of children can hardly realize what an uplift 
 and different point of view there comes with a clean mouth and pol- 
 ished teeth. It is interesting to see a child whose teeth have been pol- 
 ished and a washbowl instruction given in the use of the tooth brush, 
 gradually change in general appearance regarding cleanliness. I have 
 known them in a few weeks to choose a new set of companions because 
 the old friends no longer looked attractive to them. No one ever saw 
 a rowdy with a clean mouth, for cleanliness breeds refinement. The 
 proper food supply to the body and cleanliness are the two main founda- 
 tion pillars for health, and these must be taught and practised before 
 we can hope to obtain satisfying results in the betterment of child life. 
 There is much in life worth while besides teeth, but I know of no one 
 factor that is more conducive to health than sound teeth and a clean 
 mouth. ^ 
 
 " The question may be asked : How are we to educate these women to 
 be dental hygienists? In every large city there are men in both the 
 medical and dental professions who are competent to establish a lecture 
 course for this purpose. The necessary training in the prophylactic 
 treatment of the teeth would, of course, be given by dentists. Both of 
 these professions are anxious to aid in any cause so worthy, and I believe 
 they would willingly give their time and knowledge to start such a 
 movement. It is impossible in this paper to give the details concerning 
 the education of these women and their full duties in the schools, but 
 enough has been stated to permit those in charge of our public school 
 systems to consider the proposition in a general way and determine if 
 this plan is a solution of the main problem regarding school hygiene." 
 
 Inception of the Bridgeport Experiment. — For four years previous to 
 1913, strenuous efforts had been made to interest the city officials of 
 Bridgeport to provide funds for an educational and preventive dental 
 clinic in the public schools. At last five thousand dollars was appor- 
 tioned to the Board of Health in order that a demonstration might be 
 made to prove the value of a mouth hygiene campaign conducted on an 
 educational and preventive plan. 
 
 With the possibility of this movement being a powerful aid in the 
 prevention of dental decay, infectious and communicable diseases, 
 eighteen prominent educators in the East agreed to come to Bridgeport 
 and give their services gratis to educate a corps of women to be known 
 
^&AJUvy^6MsA C^ Ui^^\ 
 
 MOUTH HYGIENE IN PUBLIC SCHOOLS 307 
 
 as dental hygienists. The course was started in the late fall of 1913, 
 and in June, 1914, the first class of dental hygienists was graduated. 
 
 Tfie'B^oardof Health appointed a committee of four dentists and one 
 member of the Health Board, a physician, to estaV^lish the system in 
 the schools. Eight dental hygienists and two supervisors were chosen, 
 and in vSeptember, 1914, the work was begun for the first and second 
 grade children. 
 
 First Hygienists at Work in Public Schools. — There were four distinct 
 parts to the system. First, the prophylactic treatment or the actual 
 cleaiiing and polishing of the children's teeth and chart examination of 
 the mouths. Second, tooth-brush drills and class-room talks. Third, 
 stereopticon lectures for children in the higher grades; and, fourth, 
 educational work in the homes by means of special literature for 
 parents. The prophylactic treatment consisted mainly in the thorough 
 cleaning, by means of orange wood sticks in hand polishers, of every 
 surface of every tooth. This meant that the dental hygienist would 
 remove all stains and accretions from the surfaces of the teeth, and 
 especially the mucilaginous films known as bacterial plaques, which 
 are the initial step of dental decay. The treatments were given in the 
 schools, the equipment being portable and adapted to almost any 
 location. Every child received the same treatment, regardless oi the 
 financial status of the parent; in short, this preventive system was 
 incorporated as part of the school f ^.rriculum. Some parents objected, 
 thinking the work was a charity, fmt with a better understanding of it 
 the objections were soon withdrawn. 
 
 The tooth-brush drills were given by the supervisors, and a method 
 of mouth brushing was taught for use in the home. No attempt was 
 made to use water and a dentifrice in the class room, as this would prove 
 to be too mussy. Class-room talks concerning foods, cleanliness, etc., 
 were part of the drill. The total number of children examined and 
 treated in the first and second grades the first year was 6768. On the 
 first examination less than ten per cent, were brushing their teeth daily. 
 About thirty per cent, claimed that they brushed their teeth occasion- 
 ally, while sixty per cent, were frank enough to state that they did not 
 use a tooth brush. Ten per cent, of the children were found to have 
 fistulse on the gums, showing the outlets of abscesses from the roots of 
 decayed teeth, and they averaged over seven cavities per child. It was 
 shocking to find the mouths of these children ranging from five to seven 
 years in this deplorable condition, and it was appalling to contemplate 
 the conditions that would exist in these mouths as the children grew up. 
 It presented very interesting material to work with. 
 
 It will take a long period of public education before the mouths of 
 the incoming children to our first grade will show any great degree of 
 improvement. From birth to five or six years of age they are entirely 
 under the home influence and are permitted to eat foods, especially 
 sweets, that are conducive to decay, and mouth cleanliness is not com- 
 pulsory. Slowly but surely the public school education will seep back 
 
308 APPENDIX 
 
 into the homes, and with the aid of the older children and pamphlets 
 it is our hope that eventually the mouths of these children will present 
 a much improved condition. 
 
 Corps of Hygienists Increased. In September, 1915, six additional 
 hygienists were added to the corps to advance the work to cover the 
 first three grades. This gave a sufficient number of workers until 
 1917 when six more were added, so that this care could be given to all 
 the children in the first five grades, numbering about 15,000. 
 
 In January, 1918, the parochial schools petitioned the Board of 
 Health and also the Board of Apportionment to have this system 
 extended to them as a health measure. This petition was granted and 
 in September six more hygienists were added to the corps for this 
 purpose, making twenty-six in all. At the present time these women 
 have under their care the mouths of nearly twenty thousand children 
 in the first five grades. 
 
 We have also employed three women dentists, who are filling the 
 small cavities in the first permanent molars for the children in the first 
 and second grades. Many of these children, on entering school, have 
 small cavities developing in these most important teeth, and in order 
 that all the children may start on an equal basis in the future preven- 
 tion of dental decay of the permanent teeth, all are eligible and are 
 encouraged to have these small cavities filled. 
 
 Examination of Fifth Grade Children. — In order to prove definitely 
 the value of education and preventibn, it was necessary to have data 
 of the condition of the mouths of children in a higher grade who had 
 never had the advantage of prophylactic treatments, tooth-brush drills, 
 and education in mouth hygiene. The children of the fifth grade were 
 chosen as the control class, and this report will present the comparison 
 of their mouth conditions with the present fifth graders, who have had 
 prophylactic treatments and education in mouth hygiene for the first 
 five years of their school life. They have had no repair work provided 
 for them and the educational side has been three-quarters of the work 
 of the dental hygiene corps. 
 
 In making this demonstration it was not our expectation to make a 
 startling reduction in the percentage of dental decay, the main object 
 being to show up the pernicious mouth conditions prevailing among 
 school children and to prove the value of prevention and education in 
 mouth hygiene for great numbers of children in preference to exten- 
 sive repair clinics, with no effort to eliminate the source of the trouble. 
 It would, of course, have been ideal to have had the two types of clinics 
 and to have put the children's mouths in sound condition, but funds 
 were not available for this purpose, and the excellent report shown is 
 merely the result of education and prevention. 
 
 For the purpose of securing this data a complete record chart has 
 been maintained of the condition of every child's mouth at each succes- 
 sive treatment, and the following figures were obtained by comparing 
 the average number of cavities per child in the fifth grade of a given 
 
MOUTH HYGIENE IN PUBLIC SCHOOLH 309 
 
 school with the average secured from the same grade of the same school 
 several years ago. The demonstration was conducted in thirty schools 
 and this year twenty thousand individual children received this treat- 
 ment and education. 
 
 Dental Caries. — Following is the percentage of reduction of cavities 
 in the permanent teeth of the fifth graders in these schools: 
 
 The highest was Barnum school, which showed a reduction of 67.5 
 per cent. ' 
 
 The following five schools were over 57 per cent. : Huntington Road, 
 Kossuth, Prospect, Grand and Sheridan. 
 
 Two schools, Maplewood and Franklin, showed over a 50 per jent. 
 reduction. 
 
 Three schools, Summerfield, Lincoln and Staples, were over 40 
 per cent. 
 
 Washington, Wheeler and Black Rock were over 30 per cent, 
 
 Newfield, Garfield, Hall, Jackson and Shelton were over 25 per cent. 
 
 Bryant, Elias Howe and Madison were over 20 per cent. 
 
 Those over 15 per cent, were Waltersville, Jefferson, Longfellow, 
 Columbus and Webster. 
 
 One school. Read, was below 10 per cent., and two schools, Whittier 
 and McKinley, showed a minus record. 
 
 The total average for all these schools amounts to 33.9 per cent.^ 
 
 Although the principals and teachers have given splendid cooperation 
 in many of the schools that have l(t'^; records, they had to contend with 
 a certain number of children whose home influence was not conducive 
 to any interest in mouth hygiene. 
 
 Difficulties Met With.^ — The two schools which showed a minus record 
 were unfortunate enough to have a number of children who were so 
 absolutely negligent in the care of their mouths that they dragged down 
 what would have been a reasonably good average by three-quarters 
 of the children. 
 
 Bridgeport has been one of the most difficult cities in which to carry 
 on a demonstration of this kind. We have a large foreign population 
 of which many parents do not speak English. Being a munition center 
 during the war period, the population increased many thousa^nds, over- 
 crowding the city and schools. The school records showed in the past 
 year that 58 per cent, of the children changed addresses and that the 
 population was constantly shifting. The principals and teachers were 
 occupied with many war duties, such as Junior Red Cross, thrift stamps, 
 Hoover programs, etc. In short, no period could have been more 
 unpropitious for a serious demonstration of this kind. 
 
 Aside from this, the value of education and prevention has, with 
 deliberate intent, been put to the hardest possible test. No effort has 
 been made to address or educate the teachers or to enforce cooperation 
 through the office of the superintendent of schools. The supervisors 
 and dental hygienists have been permitted to win their own way, so 
 
 / 1 Percentage of reduction was 49.6 for 1919-20. 
 
310 APPENDIX 
 
 that it might be demonstrated that what was accompHshed in Bridge- 
 port could be accompHshed in any city. 
 
 Reduction of Dental Caries. — ^We beUeve that from 70 per cent, to 
 
 |f80 per cent, of dental caries can be eliminated through the public 
 
 school system by the incorporation in the school curriculum of a definite 
 
 'health program, making hygiene one of the requisites for promotion. 
 
 This would insure the cooperation and interest of the child, teacher 
 
 and parent. 
 
 The elimination of dental decay is so dependent upon factors other 
 than cleanliness and education in mouth hygiene that it is surprising to 
 note the large reduction in many schools. The most important factor 
 is that ofjiiet, and cooperation in this. matter can be secured only after 
 many years of education. The correct feeding of a child from birth 
 to twelve years would in itself partially, if not wholly, eliminate dental 
 decay. The education of mothers regarding the feeding of children 
 after they reach an age when milk does not meet the requirements 
 of the body is very essential, but it is necessarily slow, and little 
 cooperation can be secured at this time. The most important factor 
 i^ould be the elimination of free sugar from the diet. This seems radical 
 to the vast majority of our people who consume ninety pounds of sugar 
 )er capita per year and look upon it as a food and a necessary part of 
 the diet. This is an erroneous idea, since nature has provided all the 
 sugar that the body requires in various common foods, as milk, fruits, 
 some of the vegetables, etc., besid^^ providing that all starchy foods, 
 such as potatoes, bread, macaroni, rice, etc., be changed into sugar in 
 the digestive process. 
 
 The excessive consumption of free sugar is undoubtedly the cause 
 of exceedingly poor teeth among the English, French and American 
 peoples. 
 
 It is not hard to imagine that a very large percentage of children 
 are constantly laboring under a handicap of faulty feeding which in 
 turn produces a long line of other handicaps, such as malformed jaws, 
 decayed teeth, underdevelopment, malnutrition, etc., while the most 
 normal conditions could be secured by correct diet and cleanliness. 
 
 Malocclusion. — Aside from deatal^decay, the most noticeable defect 
 
 in the mouths of the school children is lack of proper relationship 
 
 between the jaws and teeth, or malocclusion. The symmetrical devel- 
 
 fopment of the brain case and the bones of the face, as well as good 
 
 I digestion, is dependent upon a perfect masticating machine. It was 
 
 ^-ttstenishing to note that malocclusion was present in 98 per cent, of all 
 
 the children examined in the past five years. Xhlljde/plorable^ondition 
 
 could be remedied to a great degree by the feeding in early childhood 
 
 of the Hard, coarse foods requiring pressure to thoroughly masticate, 
 
 and by the prevention of any pernicious habits, such as thumb sucking, 
 
 the use of pacifiers, mouth breathing, etc. Undoubtedly adenoids 
 
 would be prevented to a marked degree if the roof of the mouth could 
 
 be broadened and lowered by such pressure exerted in chewing. This 
 
MOUTH HYGIENE IN I'lJIiLIC SCHOOLS 'M] 
 
 would permit of wide nasal cavities that would be conducive to nose 
 breathing and proper functioning of the nasal passages. 
 
 When but two per cent, of our school children have regular teet h it 
 adds to the difficulty of eliminating dental decay, since irregular teeth /" 
 offer the greatest opportunity for the formation of cavities and re nder ^ 
 the thorough cleansing of the mouth very difficult. 
 
 Retardation. — Our modern city school systems all have a smaller or 
 greater per cent, of retarded pupils. The test of the success of any city 
 school system at any given time is not whether there be at that time 
 a large percentage of retarded children, but whether a decided trend 
 can be traced toward an increase or decrease in percentage of such 
 retarded children. 
 
 Retardation is a serious matter from the standpoint of the p)upil, the 
 parent, the teacher, and the community. Retardation means reeduca- 
 tion, and this in turn means the application of public funds for repeating 
 the operation. In the figures given below the very liberal standard 
 adopted for retardation permits the child to be two years older than 
 his grade would warrant and still be classified as regular. Those who 
 are more than two years older than entering the first grade at the age 
 of five would indicate, are classified as retarded. 
 
 The statistics at hand in the office of the Board of Education are 
 not available year by year, but two general surveys have been made — 
 one during September, 1912, and the other in November, 1918. These 
 surveys, called the Age-Grade Repf)rt, immediately precede the open- 
 ing of our work and occur near the close of the first five-year periods 
 and so offer rather unusual opportunity for inference as to the effects 
 produced. Reduced to a percentage basis, the changes that have 
 taken place in the matter of retarded pupils in the grammar schools 
 are summarized in the following table : 
 
 PERCENTAGE OF RETARDED PUPILS. 
 
 September, 1912. November, 1918. Drop in 
 
 Grade. Per cent. Per cent. retardation. 
 
 I 16.5 8.1 51 
 
 II 37.0 15.3 58 
 
 III 53.0 24.7 53 
 
 IV 59.5 31.7 47 
 
 V 61.0 33.1 45 
 
 VI 54.0 30.4 44 
 
 VII 39.0 19.3 50 
 
 VIII 27.0 12.5 54 
 
 Average 40.0 20.1 50 
 
 This reduction of retardation by 50 per cent, is a really wonderful 
 change to be accomplished in any school system in a period of five or 
 six years. Few people have realized the cost in money — ^which is only 
 one of the evils of retardation — of the reeducation of our retarded 
 children. By actual figures the following statement holds true: 
 
 Cost for reeducation in Bridgeport, 1912, equals 42 per cent, of entire 
 budget. 
 

 I. 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 Sept., 1912 
 
 13 
 
 17 
 
 58 
 
 107 
 
 169 
 
 Nov., 1918 
 
 
 
 
 
 11 
 
 35 
 
 109 
 
 312 APPENDIX 
 
 Costs for reeducation in Bridgeport, 1918, equals 17 per cent, of 
 entire budget. 
 
 One has only to consider the financial side to recognize that any 
 reduction in retardation is an accomplishment devoutly to be sought 
 through all legitimate means. Bridgeport has been moving distinctly 
 forward in this matter. 
 
 That this change has been a vital one to the self-respect of the pupils 
 and in the advance of the moral conditions of the normal children is 
 easily realized when one stops to consider the change in the location 
 in our grades of the pupils fourteen years old and over that has come 
 about during this same 1912-1918 survey. 
 
 PUPILS FOURTEEN YEARS OLD OR OVER. 
 
 VI. Grades. 
 
 212 — 4.0 per cent, of elementary pupils. 
 
 155 — 1.5 per cent, of elementary pupils. 
 
 Nor does this tell the entire story. As a result of the 1912 survey 
 the following statement is made : " During the fifteen months ending 
 last December, 1356 children in Grades II to VI, all of the retarded class, 
 and over fourteen years of age, left school to go to work." Examina- 
 tion of the records of the State Examination Board reveals the fact 
 that during the same period of the last year less than 300 pupils, all ot 
 whom came from grades V and VI, received working certificates. 
 
 Another effective proof of the^reat forward movement that has 
 taken place in the lower grammar school grades is submitted in the 
 following form : 
 
 In 1912, 60 per cent, of all the children registered in the grammar 
 schools were below the fourth grade, while in 1918 but 50 per cent, 
 were below the fourth grade. Similarly, in 1912, 85 per cent, were 
 below the sixth grade, and in 1918 but 78 per cent, were below the 
 sixth grade. 
 
 Without taking into consideration the physical condition of the 
 children, educators claim that the three major factors producing 
 retardation are: 
 
 II . Overcrowded class rooms. 
 'p. Uninteresting and unsuitable courses of study. 
 f 3. Unqualified teachers. 
 "Regarding the first, the following situation is interesting to note: 
 Average pupils per teacher, 1912, 38. 
 Average pupils per teacher, 1918, 40. 
 The cause for reduction in retardation does not lie here. This has 
 been rather a hindrance to its reduction. 
 
 In regard to the course of study, a very effective reorganization of 
 the subject matter in arithmetic, geography, language and history has 
 been made within the past three years, and that, no doubt, has had a 
 large influence in the matter of producing an interest in their work 
 
MOUTH HYGIENE IN PUBLIC SCHOOLS 313 
 
 on the part of the pupils. This must have had a very potent influence 
 in reduction of retardation. 
 
 With respect to the matter of teachers, the personnel and chief source 
 of supply in Bridgeport remains about the same as in 1912. Our City 
 Normal School produces most of the additional teachers placed in the 
 grammar school grades. A well-arranged study program has been 
 introduced for teachers requiring application to approved courses for 
 advancement in salary, and this has probably resulted in a more wide- 
 awake teaching body than we had in 1912. 
 
 These changes, however, could hardly have effected on their own 
 account the phenomenal reduction in retardation that has occurred in 
 the period stated. The most sanguine advocate would hardly take the 
 ground that such a remarkable change had been effected simply by 
 the introduction, late in the period under discussion, of modified courses 
 of study. There must have been other contributing factors with a large 
 influence. 
 
 Our dental work has called attention to the necessity of taking into 
 account the child's well being. For the greater part of the period of 
 this demonstration this work stood practically alone in any progressive 
 health movement. During the latter part it has been aided by the City 
 Health Department w^th an enlarged force of nurses, and at the present 
 time the Superintendent of Public Schools is planning a Health Program 
 to be introduced into the grammar schools in September as a big, serious 
 effort in recognition of the fundanv^ntal physical basis for all education. 
 He says: "The dental clinic has been without question a great factor 
 in the health of the children, and, therefore, must have been one of the 
 factors in reducing the condition of retardation, which figures show have 
 been reduced 50 per cent, since November, 1912. Our promotions 
 now are better than normal." 
 
 With all these facts balanced it seems only fair to conclude that while 
 the work^of the Dental Division in the public schools is somewhat 
 intangible, it hasj^had a very marked effect upon a more normal promo- 
 tion of children, since the change cannot be explained by other factors. 
 
 Communicable Diseases. — The forms of communicable diseases 
 where mouth hygiene could play an important part for prevention are 
 those which involve the respiratory tract or find ingress to the body 
 through the mucous membrane lining the mouth, throat and nares. 
 The resistance to bacterial invasion may not be determined entirely 
 by the contents of the blood, but by the tone and resistance of the cells 
 of the individual tissues on which the bacteria may lodge temporarily. 
 One bacterium does not produce a disease. It is only when the 
 environment proves favorable for their propagation and the production 
 of large numbers that infection occurs. 
 
 Any continuous effprt that has for its object the removal of dead 
 animal and vegetable matter, such as food debris, from all the surfaces 
 of all the teeth, the stimulating and keeping up of the tone of the mem- 
 brane lining the mouth, and the reducing of the number of bacteria in 
 
314 APPENDIX 
 
 the mouth to a minimum, must act as a powerful preventive by aiding 
 the tonsils, the soft palate, and the pharynx to maintain a normal and 
 healthful condition. 
 
 Conversely, those mouths which are neglected and contain decayed 
 teeth with decomposing food, red and congested gums, enlarged tonsils 
 and a palate and pharynx covered by an irritated and partly congested 
 mucous membrane, present an ideal field for the lodgment and incuba- 
 tion of the pathogens. How much of the communicable diseases that 
 gain ingress through the mouth will finally be eliminated from child 
 life in our public school system by an enforced system of mouth hygiene 
 is still a question, but all evidence seems to show that a clean mouth 
 with sound teeth is the one most important factor for prevention. 
 
 Up to a short time ago we had no tangible records in the Depart- 
 ment of Health that pertained to communicable diseases in the children 
 of our public schools, whereby comparisons could be made from year to 
 year of an increase or decrease in the numbers of these diseases. It is, 
 therefore, impossible at the present time to show what obtained in the 
 schools four or five years ago in comparison with what obtains today. 
 
 Out of the death-rates from all causes in this city we have been able 
 to find records of three diseases which are so common among children, 
 namely, diphtheria, measles and scarlet fever. These are figured on a 
 basis of per 100,000 population, and show the following : 
 
 1914. 1918. 
 
 i Diphtheria ^ . . . . 36.6 18.7 
 
 i Measles 20.0 4.1 
 
 '■' Scarlet fever 14.1 0.5 
 
 From the death-rate tables the general inference must be that the 
 percentage of communicable diseases is gradually decreasing. 
 
 Influenza. — The record of Bridgeport during the great scourge of 
 influenza was an exceptionally good one. The deaths amounted to 
 5.2 per cent, per 1000 population. This is the lowest record we have 
 been able to find as yet in cities approaching the size of Bridgeport. 
 
 The City Health Officer took the stand that since influenza was 
 spread by the expelled secretions of the mouth and respiratory tract, 
 the greatest means of suppressing this disease would be the knowledge 
 of children and adults of the dangers of coughing, sneezing and spitting. 
 He inaugurated an intensive educational campaign in theaters, motion- 
 picture houses and at all public gatherings regarding the contraction 
 and spread of influenza. During this period he stated that an intelli- 
 gent background for this education had been prepared by the regular 
 work of the dental clinic in instructing children individually and in dis- 
 tributing thousands of hygiene pamphlets in the homes for the enlightr 
 enment of the parents, regarding common ways of spreading diseases 
 and the hygiene of prevention. Five years of such education in con- 
 junction with mouth hygiene, played an important part in giving our 
 citizens, as a whole, a more intelligent impression regarding contagious 
 
MOUTH HYGIENE IN l^UBIJC SCHOOLS 3lo 
 
 diseases, and the health officer and his co-workers had a more enhght- 
 ened public to work with. He states further that " the most important 
 side of this work is the educational opportunities afforded the h ygienist. 
 She is an important factor in raising the sanitary intelligence of the 
 community, which is, after all, the object for which modern health 
 workers are striving." 
 
 Summary. — To summarize : we have found that in schools or districts 
 where little or no attention has been given to mouth hygiene it is 
 difficult to find three children out of a hundred with teeth entirely free 
 from dentaLcarieSv— We have also found that, owing to this lack of 
 e'ducatTon and enlightenment, not more than 10 per cent, of the 
 children were using a tooth brush daily. That malocclusion, which 
 means that the teeth are out of their normal position in the mouth, 
 thus preventing their striking the teeth in opposition, as nature intended 
 they should strike, is as common as dental caries 
 
 That retardations are greatly influenced by the toxic effect pro- 
 duced by numerous bacteria in unclean mouths and in diseased and 
 pulpless teeth. 
 
 Although properly tabulated records of the Board of Health do not 
 date back far enough to show facts and figures regarding communicable 
 diseases, yet we have sufficient data which, on close observation, con- 
 vinced us that mouth hygiene is to be a very powerful factor in the 
 restriction of communicable and infectious diseases in childhood. 
 
 The Dangers from Focal Infection?..— For years the dental profession 
 has appreciated the toxic influence on the system of unsanitary mouths 
 and the dangers presented to the individual by such mouths incubating 
 hundreds of millions of bacteria. It has been apparent that among 
 adults infections of the system were taking place around the necks of 
 the teeth, through the inflamed and diseased tissues which support the 
 teeth, but it was not until the .r-ray revealed the infected areas at the 
 ends of the roots that dentistry appreciated to the utmost the serious- 
 ness of neglected mouths and pulpless teeth. These apical infections 
 are difficult for the layman to understand, because they produce no 
 soreness, no pain, no inflammation, no pus. They are caused by a type 
 of bacteria known as the streptococcus viridans, which is quite friendly 
 and harmless in the mouth, and which belongs to the saprophytic class. 
 When a pulp dies in a tooth these bacteria commonly gain ingress 
 through the root canal of a tooth to the apex, or out into that area 
 where the tissues are bathed with the body juices or serum. In this 
 new environment they gradually change their nature and instead of 
 securing their food from dead animal or vegetable matter, such as they 
 found in the mouth around the teeth, they are now enabled to obtain 
 their nourishment from the blood serum which surrounds them. 
 
 Action of the Bacterial Toxin. — Like all bacteria, they exude waste 
 matter from their bodies, which is a toxin; but these bacteria, being 
 of low virulency, do not create as vicious a toxin as many of the patho- 
 gens. However, the toxin is of sufficient irritation to cause the osteo- 
 
316 APPENDIX 
 
 ciasts to break down and absorb the bony wall around the end of a root 
 of a tooth, which destruction of bone may be readily seen in the .r-ray 
 picture. This toxin is absorbed by the lymphatic vessels and its 
 presence in the blood undoubtedly excites the production of an anti- 
 toxin which neutralizes this poison and may successfully control it for 
 years. As long as the individual maintains normal health and the 
 antitoxin is produced in sufficient abundance t6 act as a neutralizer 
 these infected areas remain harmless. 
 
 Action of the Bacteria. — ^The longer these bacteria live in this environ- 
 ment of serum, the more aggressive they become, and although they 
 do not seem to take on the virulency of a true pathogen, yet when the 
 bodily resistance becomes lowered they make the trip from the end of 
 the root of a tooth, through the lymphatics and into the blood stream. 
 These microorganisms vary in their affinity for certain tissues, some 
 finding the valves or the lining membrane of the heart the most favor- 
 able, others the kidneys, while still another class may locate in the 
 joints. In fact, there seems to be no limit to the organs or tissues in 
 which the various members of this family may find a congenial habitat. 
 Having once located in a favorable environment in the body, they again 
 form colonies, and, exuding their toxin, so poison and lower the activi- 
 ties of the cells of the tissues upon which they are located that these 
 cells eventually find it impossible to properly functionate and carry on 
 their individual work, and we have the beginning of a diseased tissue 
 or organ of the body. It is because the action of these saprophytes is 
 so slow and possesses such a low virulency that the medical and dental 
 professions at large have failed to grasp, as yet, what a terrible menace 
 these focal infections are to human life, and again the sad fact is that 
 they are so exceedingly common^Jor nearly every adult has one or more 
 pulpless teeth in his mouth, and nearly every adult will show under the 
 a;-ray affected areas above such pulpless teeth. If the resistance re- 
 mains high they may carry such infection for ten — ^yes, twenty— years, 
 but a colony of these bacteria living within bone tissue and exuding 
 their toxin into the blood stream will sooner or later create systemic 
 disturbance, which, if not taken in time, will mean the beginning of the 
 end. Recently the writer has been demonstrating for his own satis- 
 faction whether the streptococcus viridans found in these infections 
 had developed the nature of a pathogen. In a number of cases cultures 
 made from infected roots proved fatal within forty-eight hours after 
 their injection into mice. 
 
 With these thoughts in mind, it must, in the near future, be recog- 
 nized that a toothache is a calamity, for most toothache means that 
 decay has already reached the pulp, and a dead pulp means danger of 
 apical infection. The best root filling we know of is a live pulp. 
 Therefore, the effort must be made to prevent decay from penetrating 
 deep enough in a tooth to involve a pulp. 
 
 When these various pernicious mouth conditions are more fully 
 understood as the one greatest factor for producing disease, medicine 
 
MOUTH HYGIENE IN PUBLIC SCHOOLS 317 
 
 will then acknowledge dentistry as its greatest specialty. Also, from 
 a prophylactic standpoint, wi'l mouth hygiene be considered the most 
 important branch of general hygiene. 
 
 Importance of a Health Program in Public Schools. — It must soon be 
 apparent to educators in our public scho(jl system throughout the 
 country that a health program of considerable magnitude is essential 
 in these schools for the prevention and correction of remediable physical 
 defects among the children. These defects, if neglected, may e\'entu- 
 ally be the cause of the child's disability, and in later life can have a 
 detrimental action, morally, mentally and physically. Xo longer can 
 they specialize on mental development and leave the body of the child 
 entirely in charge of home influence. The findings of our draft boards 
 have conclusively shown us the fallacy of such procedure. If we study 
 the following table submitted by General March, of the U. S. Army, 
 compiled from the data collected by the draft boards, we will see that 
 there has been dire neglect in the supervision of the child's body: 
 
 " The effectives at ages twenty-one to thirty, for approximately ten 
 million men, in 1917 were: 
 
 Per cent. 
 
 21 years 46 
 
 22 " 43 
 
 23 " .' 39 
 
 24 " 35 
 
 25 " . . 32 
 
 26 " 29 
 
 27 " ^ 27 
 
 28 " 26 
 
 29 " , 23 
 
 30 " 22 
 
 The effectives at the ages thirty-two to thirty-six drop to less than 
 15 per cent." 
 
 Kention is called to the rapid accumulative effect of physical 
 er the adult passes thirty years of age. j 
 
 has stated that the diseases of which we die in adult life^^ 
 ich are contracted or made possible in early youth. 
 The figures in General March's table would seem to corroborate state- 
 ments repeatedly made by pathologists that after thirty years of age 
 physical resistance to disease is on the decline, and in the vast majority 
 of people can only be maintained in middle life by healthful habits and 
 freedom from physical defects that permit bacterial invasion into the 
 system. 
 
 This demonstration has provided sufficient data to convince us that 
 every community, sooner or later, must adopt some plan, preferably one 
 of prevention, to establish clean mouths and sound teeth for school 
 children. 
 
 We know of no one movement, from the health standpoint, that 
 would be more beneficial to the nation at large than a serious educa- 
 tional campaign to eliminate dental caries, as far as would be possible. 
 There is much in this work that cannot be measured in figures, especially 
 
318 APPENDIX 
 
 the moral uplift which comes to the individual when he is taught the 
 importance of cleanUness and a wholesome respect for his body. 
 
 The prevention of diseases such as syphilis, tuberculosis, dental 
 caries, etc., will come, not through any specific form of medication or 
 treatment, but chiefly through education and enlightenment. Books, 
 pamphlets, articles in magazines and newspapers, all are of great value 
 in disseminating knowledge; but for actual tangible results in eventually 
 reaching all members of a community, nothing will compare with 
 thoroughly spreading such knowledge among the children in our public 
 school system. 
 
 The results, as shown in this report, may be obtained in practically 
 any section of the country, if the hygienists and supervisors in charge of 
 the work are sufficiently educated in their specialty. It must be clearly 
 understood that although the dental corps has been guided in its work, 
 what has been accomplished has been mainly through its own intelligent 
 individual effort and not through any coercion of the teachers by the 
 educational authorities in charge of the school system. This demon- 
 stration was conducted along these lines under the least favorable cir- 
 cumstances purposely to prove the real efficacy of prevention. It is our 
 hope that from now on a definite health program will be introduced into 
 our school system in Bridgeport that will give the teachers a greater 
 appreciation of the importance of sound bodies for the children, thus 
 securing a complete cooperation and interest on their part in this most 
 important phase of child welfare. ' 
 
 SCHEDULE OF LESSONS ON MANIKINS. 
 
 POLISHING AND INSTRUMENTATION. 
 
 First. 
 
 Teaching the four motions — digital, wrist, rigid-arm and rotary. 
 
 Grasp of pohshers. 
 
 Direction of procedure for pohshing. 
 
 First three divisions of polishing. 
 Second. 
 
 Fourth, fifth, sixth, seventh and eighth divisions. 
 Third. 
 
 Ninth, tenth and eleventh divisions and review of entire labial and buccal surfaces 
 of teeth of both jaws. 
 Fourth. 
 
 Twelfth, thirteenth, fourteenth and fifteenth divisions. 
 Fifth. 
 
 Sixteenth and seventeenth divisions and review of entire lingual surfaces of teeth of 
 both jaws. 
 Sixth. 
 
 Beginning instrumentation. 
 
 First two divisions. 
 Seventh. 
 
 Third, fourth, fifth, sixth, seventh, eighth and ninth divisions. 
 Eighth. 
 
 Practical examination on polishing. 
 Ninth. 
 
 Theoretical- (half-hour) examination on polishing. 
 
 Review of instrumentation — removal of varnish and plaster from teeth of lower 
 jaw. 
 
 Divisions ten and eleven. 
 
SCHEDULE OF LESSONS ON MANIKINS 319 
 
 Tenth. 
 
 Twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth and eighteenth 
 divisions of instrumentation. 
 Eleventh. 
 
 Review instrumentation, removal of varnish and plaster from teeth of upper jaw. 
 
 Divisions nineteen and twenty. 
 
 Use of floss for polishing approximal surfaces and use of brush wheel jor occlusal 
 surfaces. 
 Twelfth. 
 
 Examination. Instrumentation (practical) and instrumentation (theoretical;. 
 
 SYSTEM FOR INSTRUMENTATION. 
 
 Division 1. Fig. 166. 
 
 Teeth. Right lower molars, bicuspds, cuspid, lateral and central. 
 
 Surface. Lingual. 
 
 Instrument. No. 18 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger between left lower cuspid and bicuspid on 
 
 occlusal surface. 
 Motion. Wrist or rotary. 
 
 Division 2. Figs. 167 and 168. 
 
 Teeth. Left lower central, lateral, cuspid, bicuspids and molars. 
 
 Surface. Lingual. 
 
 Instrument. No. 17 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second finger on cutting edge of right lower cuspid or 
 
 lateral for left lower central, lateral and cuspid. 
 End of third finger on cutting edge of lower centrals for bicuspids 
 
 and molars. 
 Motion. Rotary. 
 
 Division 3. Fig. 169. *\ 
 
 Teeth. Left lower molars, bicuspids and cuspid. 
 
 Surface. Buccal. 
 
 Instrument. No. 18 Darby-Perry. 
 
 Fulcrum-point. End of third fingers on labial surface of lower incisors. 
 
 Motion. Wrist or rotary. 
 
 Division 4- Figs. 170 and 171. 
 
 Teeth. Lower incisors, right lower cuspid, bicuspids and molars. 
 
 Surface. Labial and buccal. 
 
 Instrument. No. 17 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger between left lower cuspid and 
 bicuspid for lower incisors. 
 Advanced on incisors for cuspid, bicuspids and molars. 
 Motion. Rotary. 
 
 Divisions. Figs. 172 and 173. 
 
 Teeth. Right lower molars, bicuspids and cuspid. 
 
 Surface. Distal. 
 
 Instrument. No. 13 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger on cutting edge of lower incisors for distal 
 
 surface of last molar. 
 End of third finger on labial surface of right cuspid and incisors 
 
 for the balance. 
 Motion. Wrist and digital. 
 
 Division 6. Similar to Figs. 172 and 173. 
 
 Teeth" Left lower cuspids, bicuspids and molars. 
 
 Surface. Dietal. 
 
 Instrument. No. 13 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger on labial surface of lower incisors 
 
 Motion. Wrist and digital. 
 
320 APPENDIX 
 
 Division 7. Similar to Fig. 174. 
 
 Teeth Right lower molars, bicuspids and cuspid. 
 
 Surface. Mesial. 
 
 Instrument. No. 14 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger on labial surface of right cuspid and incisors. 
 
 Motion. Wrist and digital. 
 
 Division 8. Fig. 174. 
 
 Teeth. Left lower cuspid, bicuspids and molars. 
 
 Surface. Mesial. 
 
 Instrument. No. 14 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger on labial surface of lower incisors. 
 
 Motion. Wrist and digital. 
 
 Division 9. Fig. 175. 
 
 Teeth. Lower incisors. 
 
 Surface. Approximal. 
 
 Instrument. Nos. 5 and 6 Smith set. 
 
 Grasp. Pen-holder. 
 Fulcrum-point. Third finger on chin. 
 
 Motion. Wrist. 
 
 Division 10. Fig. 176. 
 
 Teeth. Right upper molars, bicuspids, cuspid, lateral and central. 
 
 Surface Lingual. 
 
 Instrumenl. No. 17 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of third finger on occlusal surface between left lower cuspid 
 
 and bicuspid. 
 Motion. Wrist. 
 
 Division 11. Figs. 177 and 178. yi. 
 
 Teeth. Left upper central, lateral, cuspid, bicuspids and molars. 
 
 Surface. Lingual. 
 
 Instrument. No. 18 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second finger on cutting edge of right upper cuspid. 
 
 Motion. Rotary. 
 
 Division 12. Fig. 179. 
 
 Teeth. Left upper molars, bicuspids, cuspid, lateral and central. 
 
 Surface. Buccal and labial. 
 
 Instrument. No. 17 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second finger on labial surface of left upper central and 
 lateral and end of third finger on lingual surface of right upper 
 central and lateral, for molars, bicuspids and cuspid. 
 End of third finger on cutting edge of right upper cuspid for 
 lateral and central. 
 
 Motion. Rotary. 
 
 Division IS. Fig. 180. 
 
 Teeth. Right upper central, lateral, cuspid, bicuspids and molars. 
 
 Surface. Labial and buccal. 
 
 Instrument. No. 18 Darby-Perry. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third and fourth finger on chin. 
 
 Motion. Rigid-arm and rotary. 
 
 Division 14. Fig. 181. 
 
 Teeth. Right upper molars, bicuspids and cuspid. 
 
 Surface. Distal. 
 
 Instrument. No. 13 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger on labial surface of lower incisors, j 
 
 Motion. Digital and wrist. 
 
SCHEDULE OF LESSONS ON MANIKINS 321 
 
 Division 15. Similar to Fig. 181. 
 
 Teeth. Left upper cuspid, bicuspids and molars. 
 
 Surface. Distal. 
 
 Instrument. No. 13 Smith set. 
 
 Grasp. Pen-holder. " 
 
 Fulcrum-point. End of second or third finger on labial surface of lower incisors. 
 
 Motion. Digital and wrist. 
 
 Division 16. Similar to Fig. 181. 
 
 Teeth. Right upper molars, bicuspids and cuspid. 
 
 Surface. Mesial. 
 
 Instrument. No. 14 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger on labial surface of lower incisors. 
 
 Motion. Digital and wrist. 
 
 Division 17. Similar to Fig. 181. 
 
 Teeth. Left upper cuspid, bicuspids and molars. 
 
 Surface. Mesial. 
 
 Instrument. No. 14 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger on labial surface of lower incisors. 
 
 Motion. Digital and wrist. 
 
 Division 18. Similar to Fig. 175. 
 
 Teeth. Upper incisors. 
 
 Surface. Approximal. 
 
 Instrument. Nos. 5 and 6 Smith set. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Wrist and digital. 
 
 Division 19. Fig. 182. 
 
 Teeth. Lower. 
 
 Surface. Buccal, labial and lingual. 
 
 Instrument. Sickle-shaped. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger on cutting edge of incisors. 
 
 Motion. Digital. Draw stroke. 
 
 Division 20. Fig. 183. 
 
 Teeth. Upper. 
 
 Surface. Buccal, labial and lingual. 
 
 Instrument. Sickie-shaped. 
 
 Grasp. Pen-holder. 
 
 ' Fulcrum-point. Back of third or fourth finger on chin; or fist grasp — end of 
 
 thumb on occlusal surface. 
 Motion. Digital. Draw stroke. 
 
 Division 21. 
 
 Instrument. Nos. 3 and 4 Harlan. 
 
 Use. For small, hard, tenacious deposits under gingival border. 
 
 Motion. Draw stroke. 
 
 SYSTEM FOR POLISHING— LARGE STICK. 
 
 Division 1. 
 
 Fig. 186 
 
 
 
 
 
 
 Teeth. 
 
 
 Upper right ce 
 
 intral and lateral 
 
 
 
 Surface. 
 
 
 Labial. 
 
 
 
 
 
 Grasp. 
 
 
 Porte polisher 
 
 held in fist. 
 
 
 
 
 Fulcrum-point. 
 
 End of thumb 
 
 on cutting 
 
 edge 
 
 of right 
 
 cuspid. 
 
 Motion. 
 
 
 Digital, 
 
 
 
 
 
 ?1 
 
 
 
 
 
 
 
322 APPENDIX 
 
 Division 2. Fig. 187. 
 
 Teeth. Upper right cuspid, first and second bicuspids. 
 
 Surface. Labial. 
 
 Grasp. Fist. 
 
 Fulcrum-point. Back of third finger on chin. 
 
 Motion. Rigid-arm. 
 
 Division 3., Fig. 188. 
 
 Teeth. Upper right molars. 
 
 Surface. Buccal. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rotary. 
 
 Division Jf.. Similar to Fig. 188. 
 
 Teeth. Lower right molars. 
 
 Surface. Buccal. 
 
 Grasp. Pen-holder. 
 
 Ftdcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rotary. 
 
 Division 5. Similar to Fig. 187. 
 
 Teeth. Lower right bicuspids and cuspid. 
 
 Surface. Buccal. 
 
 Grasp. Fist. 
 
 Fulcrum-point. Back of second finger on chin. 
 
 Motion. Rigid-arm. 
 
 Division 6. Fig. 189. 
 
 Teeth. Lower incisors. 
 
 Surface. Labial. w 
 
 Grasp. Fist. 
 
 Fulcrum-point. Thumb or first finger of left hand, depressing lips. 
 
 Motion. Rigid-arm. 
 
 Division 7. Similar to Fig. 187. 
 
 Teeth. Left lower cuspid and bicuspid. 
 
 Surface. Labial. 
 
 Grasp. Fist. 
 
 Fulcrum-point. Back of second finger on chin. 
 
 Motion. Rigid-arm. 
 
 Divisions. Similar to Fig. 190. 
 
 Teeth. Lower left molars. 
 
 Surface. Buccal. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rigid-arm. 
 
 Division 9. Fig. 190. 
 
 Teeth. Upper left molars. 
 
 Surface. Buccal. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rigid-arm. 
 
 Division 10. Similar to Fig. 187. 
 
 Teeth. Left upper bicuspids and cuspid. 
 
 Surface. Labial. 
 
 Grasp. Fist. 
 
 Fulcrum-point. Back of third finger on chin- 
 
 Motion- Rigid-arm, 
 
PROPOSED MODEL COURSE 323 
 
 Division 11. Similar to Fig. 186. 
 
 Teeth. Left upper lateral and central. 
 
 Surface. Labial. 
 
 Grasp. Fist. 
 
 Fulcrum-point. End of thumb on cutting edge of right central. 
 
 Motion. Digital. 
 
 Division 12. Fig. 191. 
 
 Teeth. Right lower molars and bicuspids. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rotary (or using side of stick with rigid-arm motion). 
 
 Division 13. Fig. 192. 
 
 Teeth. Right lower cuspids and incisors. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second or third finger from cutting edge of incisors to 
 
 first bicuspid. 
 Motion. Rotary. ^ — • 
 
 Division l^. Fig. 193. 
 
 Teeth. Left lower cuspid, bicuspids and molars. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. End of second finger on labial surface of lower incisors. 
 
 Motion. Both rigid-arm and rotary. 
 
 Division 15. Fig. 194. 
 
 Teeth. Left upper molars and bicuspids. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder , 
 
 Fulcrum-point. End of third finger c a. labial surface of right lower lateral or cuspid. 
 Motion. Rigid-arm (or third finger on masticating surface of right upper 
 
 bicuspid, rotary motion). 
 
 Division 16. Fig. 195. 
 
 Teeth. Left upper cuspid and upper incisors. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point! End of second or third finger on cutting edge of right upper cuspid. 
 
 Motion. Rotary. 
 
 Division 17. Fig. 196. 
 
 Teeth. Right upper cuspid, bicuspids and molars. 
 
 Surface. Lingual. 
 
 Grasp. Pen-holder. 
 
 Fulcrum-point. Back of third or fourth finger on chin. 
 
 Motion. Rotary. 
 
PROPOSED MODEL COURSE FOR THE EDUCATION AND 
 TRAINING OF THE DENTAL HYGIENIST. 
 
 At the request of several persons who are interested in the problem 
 of educating and training the dental hygienist, the writer has outlined 
 what he considers to be a model course for this purpose. 
 
 The curriculum is based upon the original conception of the service 
 for which the dental hygienist was created. The announcement of the 
 first course in September, 1913, is quoted as follows: 
 
 " In the last few years there has been a great demand for women 
 as hygienists and prophylactic operators in dental offices, for it is a 
 well-known fact that at least 80 per cent, of dental diseases can be 
 prevented by following a system of treatment and cleanliness. 
 
 There is now also developing a demand for these women in public 
 institutions such as schools, hospitals and sanitariums. The scientists 
 and learned professional men have no means of spreading their findings 
 and knowledge for the prevention of disease to the public except through 
 pamphlets, newspapers and magazine articles. Although these have 
 done good service they are not so efficient as teachers of hygiene and 
 dental prophylactic workers would be." 
 
 There is a noticeable tendency on the part of some training schools 
 to divert the dental hygienist from her true field of service by devoting 
 a portion of the course to training in chair assistance to dentists and oral 
 surgeons. Although tihfe need of dentists and oral surgeons for trained 
 assistants is very apparent, it must be definitely understood that this 
 assistant should not be the dental hygienist. Her field of service is 
 in no way analogous to that of the nurse or chair assistant. It is very 
 desirable that she should be competent and willing to cooperate in 
 any way to maintain the routine of an office or dispensary, but it is not 
 desirable that her efforts should be continually diverted into fields 
 of service which do not require her highly specialized training. The 
 dental hygienist, as the original announcement shows, was created to 
 be, primarily, an educator for hygiene and secondarily, a dental pro- 
 phylactic operator. 
 
 In the following outline the daily schedule is planned so that the 
 majority of the lectures occur in the morning periods when the mind 
 is alert and the student is most receptive. The afternoon work for 
 the greater part of the course is completed at three o'clock;, and at 
 no period is it continued after four o'clock. It is essential that' 
 the student shall have at least two hou;rs of daylight for outdoor 
 exercise and recreation before devoting the evening to study and 
 review. A very definite plan has been followed of having the practical 
 training advance only as the theory can be assimilated. The courses 
 in Physics, Elementary and Biologic Chemistry, Physiology, and 
 Dental Histology could be strengthened by the addition of some 
 practical laboratory work. 
 
 The lecture periods during March and April are devoted to training 
 the true teacher of hygiene. The month of May can be utilized for 
 broadening the clinical experience of the student. There should be an 
 opportunity during this month for the student to put into practice the 
 teaching of hygiene in conjunction with the dental prophylactic 
 treatment. Several periods have been reserved throughout the course 
 for lectures on special subjects of interest to the class, 
 
DENTAL HYGIENISTS' DAILY PROGRAM— COURSE OF STUDY. 
 Last Week of September. (First Semester.) 
 
 Sept. 
 
 Monday. 
 
 Tuesday. 
 
 Wednesday. 
 
 Thursday. 
 
 Friday. 
 
 Saturday. 
 
 9-10 
 
 Anatomy 
 
 and General 
 
 Histology 
 
 Physiology 
 
 Anatomy 
 
 and General 
 
 Histology 
 
 Physiology 
 
 Anatomy 
 
 and General 
 
 Histology 
 
 PhyBiology 
 
 10-11 
 
 
 Special 
 
 Anatomy 
 
 (Head, Teeth, 
 
 Jaws) 
 
 
 Special 
 
 Anatomy 
 
 (Head, Teeth, 
 
 Jawsj 
 
 
 
 2-3 
 
 Physics 
 
 
 Physics ■ 
 
 
 Physics 
 
 
 October. 
 
 9-10 
 
 Anatomy and 
 General 
 Histology 
 
 Physiology 
 
 Anatomy and 
 General 
 Histology 
 
 Physiology 
 
 Anatomy and 
 
 General 
 
 Histology 
 
 Physiology 
 
 10-11 
 
 Physics 
 
 Special 
 
 Anatomy 
 
 (Head, Teeth, 
 
 Jaws) 
 
 Tooth Carving 
 
 Special 
 
 Anatomy 
 
 (Head, Teeth, 
 
 Jaws) 
 
 Tooth Carving 
 
 Special 
 
 Anatomy 
 
 (Head, Teeth, 
 
 Jaws) 
 
 11- 
 12.30 
 
 Tooth Carving 
 
 Tooth Carving 
 
 Tooth Carving 
 
 Tooth Carving 
 
 2-3 
 
 Dental 
 Histology 
 
 Bacteriology 
 
 and 
 Sterilization 
 
 Dental 
 Histology 
 
 Bacteriology 
 
 and 
 Sterilization 
 
 Dental 
 Histology 
 
 
 
 
 
 November. 
 
 
 
 9-10 
 
 Anatomy and 
 General 
 Histology 
 
 Physiology 
 
 Manikin 
 Demonstration 
 
 Physiology 
 
 Anatomy and 
 
 General 
 
 Histology 
 
 
 10-11 
 
 Elementary 
 
 Biologic 
 Chemistry 
 
 Manikin 
 Practice 
 
 Special 
 
 Anatomy (Head, 
 
 Teeth, Jaws) 
 
 Elementary 
 
 Biologic 
 Chemistry 
 
 Manikin 
 Demonstration 
 
 11- 
 12.30 
 
 Manikin 
 Practice 
 
 Manikin 
 Practice 
 
 Manikin 
 Practice 
 
 
 2-3 
 
 Dental 
 Histology 
 
 Bacteriology 
 
 and 
 Sterilization 
 
 Comparative 
 
 Dental 
 
 Anatomy 
 
 Bacteriology 
 
 and 
 Sterilization 
 
 Comparative 
 
 Dental 
 
 Anatomy 
 
 
 
 
 December to Christmas Holidays. 
 
 
 
 9-10 
 
 Anatomy and 
 
 General 
 
 Histology 
 
 Physiology 
 
 Manikin 
 Demonstration 
 
 Physiology 
 
 Anatomy and 
 
 General 
 
 Histology 
 
 
 10-11 
 
 Deposits and 
 Accretions 
 upon Teeth 
 
 Manikin 
 Practice 
 
 Deposits and 
 Accretions 
 upon Teeth 
 
 Dento- 
 Chemistry 
 
 Manikin 
 Demonstration 
 
 11- 
 12.30 
 
 Manikin 
 Practice 
 
 Manikin 
 Practice 
 
 Manikin 
 Practice 
 
 
 2-3 
 
 Inflammation 
 
 Dental Caries 
 
 
 Dental Caries 
 
 
 
 January. 
 
 9-12 
 
 Practical Work Children. 
 
 2-3 
 
 Dental 
 Prophylaxis 
 
 Pyorrhea 
 Alveolaris 
 
 Special 
 
 Pyorrhea 
 Alveolaris 
 
 Dental 
 Prophylaxis 
 
 
 3-4 
 
 
 Malocclusion 
 
 
 Malocclusion 
 
 
 
 
 
 February. (Second Semester.) 
 
 
 
 9-12 
 
 Practical Work, Children 
 
 2-3 
 
 Dental 
 Prophylaxis 
 
 Alveolar 
 
 Abscess and 
 
 Focal Infection 
 
 
 Alveolar 
 
 Abscess and 
 
 Focal Infection 
 
 Dental 
 Prophylaxis 
 
 
 3-4 
 
 Mouth Mani- 
 festations of 
 Systemic 
 Disease 
 
 Communicable 
 Diseases 
 
 
 Odontalgia 
 
 Dermatology 
 
 
March. 
 
 
 Monday. 
 
 Tuesday. 
 
 Wednesday. 
 
 Thursday. 
 
 Friday. 
 
 Saturday. 
 
 9-12 
 
 Practical Work, Adults 
 
 2-3 
 
 Nutrition and 
 Dietetics 
 
 Radiography 
 
 Nutrition and 
 Dietetics 
 
 Radiography 
 
 Nutrition and 
 Dietetics 
 
 
 3-4 
 
 General 
 Hygiene 
 
 General 
 Hygiene 
 
 
 General 
 Hygiene 
 
 Prenatal 
 
 Hygiene and 
 
 Infant Feeding 
 
 
 April 
 
 9-12 
 
 Practical Work, Adults 
 
 2-3 
 
 Nutrition and 
 and Dietetics 
 
 Pedagogy 
 
 Personal 
 Hygiene 
 
 Pedagogy 
 
 Personal 
 Hygiene 
 
 
 3-4 
 
 School and 
 Child Hygiene 
 
 Industrial 
 Hygiene 
 
 
 School and 
 Child Hygiene 
 
 Public Health 
 Organization and 
 Administration 
 
 
 May 
 The entire month of May is spent on Practical Work. 
 
 SUMMARY— FIRST SEMESTER 
 
 Sept. 
 Hours. 
 
 Oct. 
 Hours. 
 
 Nov. 
 Hours. 
 
 Dec. 
 Hours. 
 
 Jan. 
 Hours. 
 
 Total hrs. 
 1st Sem. 
 
 Anatomy and General Histology . 
 
 Physiology 
 
 Physics 
 
 Elementary Biologic Chemistry 
 
 Dento-Chemistry 
 
 Special Anatomy of Head, Teeth, Jaws 
 
 Dental Histology 
 
 Bacteriology and Steriliza,tion . 
 Comparative Dental Anatomy 
 
 Dental Caries 
 
 Deposits and Accretions upon Teeth . 
 
 Inflammation 
 
 Dental Prophylaxis 
 
 Pyorrhea Alveolaris 
 
 Malocclusion 
 
 Total 
 
 12 
 12 
 
 11 
 
 60 
 
 48 
 
 32 
 
 30 
 
 30 
 
 7 
 
 8 
 
 3 
 
 18 
 
 16 
 
 16 
 
 8 
 
 6 
 
 6 
 
 3 
 
 6 
 169 
 
 Practical Work 
 
 Tooth 
 Carving 
 
 Manikin 
 Practice 
 
 Manikin 
 Practice 
 
 33 
 
 Practical 
 
 Work, 
 
 Children 
 
 54 
 
 Total 163 
 
 SUMMARY— SECOND SEMESTER 
 
 Feb. 
 Hours. 
 
 Mar. 
 Hours. 
 
 Apr. 
 Hours. 
 
 May 
 Hours. 
 
 Total hours. 
 
 Dental Prophylaxis . . . . . . ... 
 
 Alveolar Abscess and Focal Infection . 
 
 Odontalgia 
 
 Dermatology 
 
 Mouth Manifestations, Systemic Disease 
 
 Communicable Diseases 
 
 Nutrition and Dietetics 
 
 General Hygiene 
 
 Radiography ' . . . 
 
 Personal Hygiene 
 
 Pedagogy 
 
 Pub. Health, Organization, Administration . 
 
 School and Child Hygiene 
 
 Industrial Hygiene 
 
 Prenatal Hygiene and Infant Feeding . 
 
 Total 
 
 32 
 
 4 
 36 
 
 Practical 
 
 Work 
 Adult 72 
 
 Practical 
 Work 
 
 72 
 
 Practical 
 Work 
 
 72 
 
 Practical 
 Work 
 112 
 
 4 
 4 
 4 
 4 
 16 
 12 
 
 Total 328 
 
INDEX. 
 
 Abscess, blind, 206 
 
 Adenoids, 44 
 
 Air cells, anatomy of, 24 
 
 ethmoidal, 26 
 
 mastoid, 26 
 Alimentary tract in dental prophylaxis 
 
 Alveolar process, anatomyjof, 34, 47 
 
 histology of, 74 
 Anterior aspect of skull, 22 
 
 fossa of skull, 18 
 
 lacerated foramen, 19 
 
 naies, 23 
 
 palatine fossa, 22 
 Antra of Highmore, anatomy of, 24 
 Apical foramen of teeth, 46 
 Aqueous humor, 28, 29 
 Arch of teeth, definition of, 116 
 Artery, maxillary, internal, anatomy of 
 42 > J , 
 
 Arthritis, oral infection and, 222 
 Articulation, temporomaxillary, 36 
 Auditory canal, external, 29 
 meatus, external, 29 
 
 B 
 
 Baboon, teeth of, 91 
 Bacteremia, 216 
 
 Bacteria, propagation of, dental prophy- 
 laxis and, 230 t- f j 
 Base of skull, 19 
 Bicuspid teeth, occlusion of, 99 
 Bicuspids, anatomy of, 50 
 
 individual characteristics of 52 
 BUnd abscess, 206 
 Blood corpuscles, 137 
 
 normal, constituents of, 137 
 
 plasma, 138 
 
 platelets, 137 
 
 supply of dental tissues, 40 
 Bloodvessels of peridental membrane, 72 
 
 of pulp, 64 
 Bone, inflammation of, 147 
 etiology of, 147 
 
 repair of, 147, 148 
 Bones, maxillary, inferior, anatomy of, 34 
 superior, anatomy of, 33 
 
 palate, anatomy of, 34 
 
 Bony sinuses, anatomy of, 24 
 Brushing of teeth in prophylaxis, 274 
 Brush-wheel in pohshing of teeth, 272 
 Buccal surface of teeth, definition of 117 
 Bull-frog, teeth of, 82 
 
 Callus, definition of, 148 
 Capsular ligaments, 94 
 Capsule of Tenon, 26 
 Caries, dental, 112, 173, 186 
 Carnivorous animals, teeth of, 85 
 Catarrhal inflammation 136 
 Cell, 223 
 
 life, factors for, 225 
 Cells, air, anatomy of, 24 
 Cementoblasts of peridental membrane, 
 
 Cementum, anatomy of, 46 
 
 canahcuH of, 63 
 
 cells of, 63 
 
 function of, 64 
 
 histology of, 61 
 
 lacunae of, 63 
 
 lamellae of, 61 
 Cheeks, anatomy of, 37 
 Choanse, 23 
 
 Chordi tympani nerve, 42 
 Choroid, 28 
 CiUary body, 28 
 
 muscle, 28 
 
 processes, 28 
 Circulation, normal, 137 
 Circumvallate papilte, 39 
 Coats of eye, 27, 28 
 Cock's crest, 18 
 Condyle of jaw, 36 
 Conjunctiva, 26 
 
 Conjunctivitis, oral infection and, 221 
 Connective tissue, 138 
 Connective-tissue cells of pulp, 64 
 Coronal suture, 17 
 Coronoid process, 36 
 Corti, organ of, 32 
 Cranial nerves, anatomy of, 40 42 
 Cranium, anatomy of, 17 ' 
 
 Crista galli, 18 
 Crocodiles, teeth of, 82 
 CrystalUne lens, anatomy of, 29 
 Curve of Spee, 100 
 
 (327) 
 
328 
 
 INDEX 
 
 Cuspids, anatomy of, 49 
 
 distinguishing points between upper 
 and lower, 50 
 Cysts, 211 
 
 Deciduous teeth, premature loss of, 
 
 malocclusion and, 127 
 Dental caries, 112, 173 
 
 areas of immunity to, 112 
 
 of susceptibility to, 112 
 lactic acid in, 180 
 malocclusion and, 113 
 prophylaxis and, 233 
 saliva in, 182 
 clinics, educational and preventive, 
 for school children, 302 
 industrial, dental hygienist in, 
 
 301 
 municipal, dental hygienist in, 
 301 
 crypt, formation of, 76 
 folhcle, formation of, 76 
 foramen, inferior, 36 
 granuloma, 206 
 
 hygienist, broad field of service of, 
 299 
 in hospitals, 301 
 in industrial dental clinics, 301 
 in municipal dental cUnics, 301 
 in private practice, 299 
 proposed model course for 
 education and training of, 324 
 in public schools, first at work 
 
 in, 307 
 in sanatoriums, 301 
 infections, chronic, systemic effects 
 from, 218 
 focus of, 218 
 
 systemic effects from, 215 
 mechanism, human, 92 
 papilla, formation of, 75 
 prophylaxis, 223 
 
 alimentary tract in, 227 
 bacterial propagation in, 230 
 brushing in, 274 
 
 of buccal surfaces, 280 
 instructions for, 280 
 of labial surfaces, 280 
 of Ungual surfaces, 283 
 of masticating surfaces, 286 
 number of daily, 286 
 in children, 273 
 decomposing food debris in, 
 
 228 
 dental caries and, 233 
 dentifrices in, 287 
 diet in, 294 
 examination of adult mouth in, 
 
 235 
 floss silk in, 288 
 gums in, 276 
 
 Dental prophylaxis, home care of mouth 
 and, 274 
 hygienist in, 235 
 instrumentation in, 239, 249 
 
 four motions in, 244 
 instruments in, 246 
 keratin in, 275 
 lime-water in, 291 
 of lower jaw, instrumentation 
 
 in, 240, 249 
 polishing in, 261 
 
 brush-wheel in, 272 
 floss in, 272 
 system of, 263 
 principles of, 234 
 in private practice, system of, 
 
 30(0 
 pyorrhea alveolaris and, 232 
 surfaces of teeth in, 238 
 syphilis and, 232 
 systemic infection and, 232 
 tissue stimulation in, 276 
 tooth-brushes and, 278 
 treatment in, 238 
 tubercidosis and, 232 
 of upper jaw, instrumentation 
 in, 241, 255 
 pulp, inflammation of, differential 
 
 diagnosis of, 195 
 ridge, formation of, 75 
 tissues, blood supply of, 40 
 nerve supply of, 40 
 Dentin, anatomy of, 46 
 ^ caries of, 186 
 fibrils of, 61 
 function of, 61 . 
 histology of, 60 
 matrix of, 61 
 
 secondary, histology of, 66 
 tubules of, 61 
 Dentifrices in dpntal prophylaxis, 287 
 Denture, human, study of, 95 
 Diet in dental prophylaxis, 294 
 Diffuse osteomyelitis, 211 
 Digastric muscle, 93 
 Distal surf ace of teeth, definition of, 116 
 Dogs, teeth of, 87 
 
 E 
 
 Ear, anatomy of, 29 
 
 cochlea of, 32 
 
 drum of, 30 
 
 external, 29 
 
 internal, 31 
 
 labyrinth of, 31 
 
 middle, 29 
 
 ossicles of, 30 
 
 fvi^nction of, 31 
 
 vestibule of, 32 
 Elephant, teeth of, 92 
 Eminentia articularis, 36 
 Enamel, anatomy of, 46 
 
INDEX 
 
 329 
 
 Enamel, functions of, GO 
 
 histology of, 58 
 
 organ, formation of, 75 
 
 rods, histology of, 5,8 
 Endocarditis, oral infection and, 222 
 Endolymph, 31 
 Endothelial cells, 138 
 
 leukocytes, 138 
 Eosiaophiles, 138 
 Ethmoidal air cells, 26 
 Eustachian tube, anatomy of, 31 
 Evolution of tooth forms, 80 
 Exacferbations, 20,9 
 Expression, muscles of, 37 
 External auditory canal 29 
 
 meatus, 29 
 Extraction of permanent teeth, mal- 
 occlusion and, 127 
 Exudation, definition of, 14^ 
 Exudative in^ammation, 136 
 Eye, coats of, 27 
 
 fibrous, 27 
 nervous, 28 
 vascular, 27 
 Eyeball, interior of, anatomy of, 28 
 Eyes, anatomy of, 26 
 
 refracting media of, 29 
 
 yellow spot of, 28 
 
 Face, anatomy of, 22 
 
 Facial nerve, anatomy of, 42 
 
 Fauces, anatomy of, 44 
 
 Fibrinous exudation, definition of, 142 
 
 Fibroblasts of peridental. membrane, 71 
 
 Fibrous Goats of eye, 27 
 
 Fifth cranial nerve, anatomy of, 40 
 
 Fishes, teeth of, 82 
 
 Fissure, sphenoidal, 19 
 
 sphenomaxillary, 22 
 Fistula, definition of, 144 
 Floor of nose, anatomy of, 24 
 Floss silk in dental priophylaxis, 288 
 in polishing of teeth, 272 
 Fones's plan of mouth hygiene proposed 
 
 in 1914, 303 
 Food debris, decomposition of, dental 
 prophylaxis and, 228 
 mastication of, 105 
 Foramen, lacterated, anterior, 19 
 middle, 19 
 optic, 19 
 ovale, 19 
 rotundum, 19 
 Fossa, palatine, anterior, 22 
 posterior, 22 
 of skull, anterior, 18 
 middle, 19 
 posterior, 19 
 zygomatic, 22 
 Fossa;, glenoid, 22 
 nasal, 22 
 
 Fossae, sublingual, 36 
 Fovea centralis, 28 
 Freinum, 37 
 Frontal sinuses, anatomy of, 25 
 
 G 
 
 Gastritis, oral infection and, 222 
 Geniohyoid muscle,. 93 
 Glands, lachrymal, 29 
 
 parotid, 43 
 
 salivary, 43 
 
 sublingual, 36, 44 
 
 submaxillary, 36, 44 
 
 tear, 29 
 Glenoid fossse, 20 
 Gnarled enamel, 59 
 Granular layer of Tomes, 61 
 Granuloma, dental, 206 
 Gums in dental propjiylaxis, 276 
 
 histology of, 74 
 
 Hard palate, anatomy of, 37 
 Head, anatomy of, 17 
 Heahng by first intention, definition of, 
 145 
 by second intention, definition of, 
 146 
 Highmore, antra of, anatomy of, 24 
 Horse, teeth of, 92 
 Hospitals, dental hygienist in, 301 
 Human dental mechanism, 92 
 
 denture, study of, 95 
 Hygienist, dental, service of, in prophy- 
 laxis, 235 
 
 Incisors, anatomy of, 47 
 
 individual characteristics of, 49 
 Inclined plane of teeth, definition of, 116 
 Industrial dental cHnics, dental hy- 
 gienist in, 301 
 Inferior dental foramen, 36 
 
 maxillary bones, anatomy of, 34 
 Inflammation, 136 
 
 of bone, 147 
 
 etiology of, 147 
 
 causes of, 138 
 
 catarrhal, 136 
 
 chronic, definition of, 144 
 
 circulatory disturbances and, 140 
 
 classification of, 136 
 
 , definition of, 136 
 
 of dental pulp, differential diagnosis 
 of, 195 
 
 disturbance of function in, 141 
 
 exudative, 136 
 
 heat in, 141 
 
330 
 
 INDEX 
 
 Inflammation, hyperemia in, 141 
 
 injury in, 140 
 
 interstitial, 136 
 
 pain in, 141 
 
 parenchymatous, 136 
 
 of pteridental membrane, differential 
 diagnosis of, 195 
 
 redness in, definition of, 141 
 
 suppurative, 136 
 
 swelling in, 141 
 
 symptoms of, 141 
 
 ulcerative, 136 
 Instrumentation in dental prophylaxis", 
 
 239, 249 
 Internal maxillary artery, anatomy of, 42 
 Interproximal spaces, 113 
 Interstitial inflammation, 136 
 Intracellular substance of pialp, 66 
 Iris, 28 
 Iritis, oral infection and, 222 
 
 Jaw, condyle of, 36 
 
 lower, instrumentation of, in dental 
 
 prophylaxis, 240, 249 
 upper, instrumentation of, in dental 
 prophylaxis, 241, 255 
 Jaws, development of, 78 
 
 growth of, malocclusion of teeth and, 
 128 
 
 Kerahn in dental prophylaxis, 275 
 
 Labial surface of teeth, definition of, 117 
 Labyrinth of ear, 31 
 Lachrymal apparatus, 29 
 
 gland, 29 
 
 sac, 29 
 Lactic acid in dental caries, 180 
 Lambdoid suture, 17 
 Lamina, formation of, 75 
 Lateral aspect of skull, 22 
 Lemurs, teeth of, 92 
 Lesion, definition of, 140 
 Leukocytes, endothehal, 138 
 
 mondnuclear, 138 
 
 polymorphonuclear, 137 
 Ligaments, capsular, 94 
 
 sphenomandibular, 94 
 
 stylomandibular, 94 
 Lime-water in dental prophylaxis, 291 
 Lingual surface of teeth, definition of, 
 117 
 
 tonsil, 40, 44 
 Lips, anatomy of, 37 
 Lower teeth, occlusion of, 96 
 
 Ludwig's angina, 213 
 
 Lymphatics of mouth, anatomy of, 43 
 
 of peridental membrane, 72 
 
 of pulp, 65 
 Lymphocytes, 138 
 
 M 
 
 Macula lutea, 28 
 Malar process, 34 
 Malocclusion of teeth, 112 
 
 classification of, 120 
 
 Angle's, 121 
 definition of, 119 
 etiology of, 126 
 
 extraction of permanent 
 
 teeth and, 127 
 lack of use and, 128, 132 
 pernicious habits and, 127 
 premature loss of decidu- 
 ous teeth and, 127 
 growth of jaws in, 128 
 individual, 119 
 in school children, 310 
 Mandible, 93 
 
 anatomy of, 34 
 muscles moving, 36 
 Manikins, schedule of lessons on, 318 
 Masseter muscle, 93 
 Mast cells, 138 
 Mastication of food, 105 . 
 y muscles of, 37, 9,3 
 Mastoid air cells, 26 
 
 antrum, anatomy of, 31 
 Maxillary artery, internal, anatomy of, 
 42 
 bones, inferior, anatomy of, 34 
 
 superior, anatomy of, 33 
 sinuses, anatomy of, 24 
 infection of, 213 
 Meckel's ganglia, 32 
 Mental foramina, 35 
 Mesial surface of teeth, definition of, 116 
 Middle fossa of skuU, 19 
 
 lacerated foramen, 19 
 Molar teeth, occlusion of, 99 
 Molars, lower, anatomy of, 54 
 upper, anatomy of, 52 
 
 individual characteristics of, 54 
 Monkey, teeth of, 88 
 Mononuclear leukocytes, 138 
 Mouth, adult, examination of, in pro- 
 phylaxis, 235 
 anatomy of, 32 
 home care of, in dental prophylaxis, 
 
 274 
 hygiene, communicable diseases and, 
 313 
 in pubHc schools of Bridgeport, 
 Conn., report of five years of, 
 302 
 retardation of school children 
 and, 311 
 
INDEX 
 
 331 
 
 Mouth, lymphatics of, anatomy of, 43 
 
 mucous membrane of, anatomy of, 
 37 
 
 roof of, anatomy of, 24 
 Mouth-brushing, 278 
 Mucous membrane of mouth, anatomy 
 
 of, 37 
 Municipal dental clinics, dental hygienist 
 
 in, 301 
 Muscles, digastric, 93 
 
 of expression, 37 
 
 geniohyoid, 93 
 
 masseter, 93 
 
 of mastication, 37, 93 
 
 moving mandible, 36 
 
 mylohyoid, 93 
 
 pterygoid, 93 
 
 temporal, 93 
 Mylohyoid muscle, 93 
 
 ridge, 36 
 Myositis, oral infection and, 222 
 
 N 
 
 Nares, anterior, 23 
 
 posterior, 23 
 Nasal cavity, blood supply of, 24 
 nerve supply of, 24 
 
 duet, 29 
 
 fossae, anatomy of, 23 
 
 neives, 18 
 
 process, 34 
 
 septum, 23 
 Nasmyth's membrane, 59 
 Necrosis of bone, 148 
 
 definitioii of, 140 
 Nephritis, oral infection and, 222 
 Nerve supply of dental tissues, 40 
 
 of ears and teeth, interconnec- 
 tion of, 32 
 Nerves, cranial, ana;tomy of, 40, 42 
 
 nasal, 18 
 
 of peridental membrane, 72 
 
 of pulp, 65 
 Nervous coats of eye, 28 
 Neuman, sheaths of, 60 
 Neuralgia, 197 
 
 causes of, 1 98 
 
 definition of, 197 
 
 naturife of, 197 
 
 quinti major, 198 
 minor, 198 
 
 treatment of, 201 
 
 type of, 197 
 
 varieties of, 198 
 Neuritis, oral infection and, 222 
 Nose, floor of, anatomy of, 24 
 
 Occlusion of teeth, 45, 97 
 
 definition of, 116, 117 
 
 Odontalgia, 191 
 causes of, 194 
 definition of, 191 
 local, 194 
 obscure, 196 
 referred, 196 
 Odontoblasts, 64 
 Olfactory groove, 18 
 Optic disk, 28 
 
 foramen, 19 
 Oral foci, 218 
 
 distribution of infection from, 
 
 218 
 proof of systemic infection 
 
 from, 218 
 secondary lesions in, 219 
 infections, arthritis and, 222 
 conjunctivitis and, 221 
 endocarditis and, 222 
 gastritis and, 222 
 general and special diseases 
 
 originating from, 221 
 iritis and, 222 
 myositis and, 222 
 nephritis and, 222 
 neuritis and, 222 
 otitis media and, 221 
 pharyngitis and, 221 
 pyemia and, 222 
 relation of, to general health, 
 
 203 
 septicemia and, 222 
 / tonsillitis and, 221 
 
 toxemia and, 222 
 Orbits, anatomy of, 22 
 Organ of Corti, 32 
 Ossicles of ear, 30 
 
 function of, 31 
 Osteoblasts of peridental membrane, 71 
 Osteomyehtis, definition of, 147 
 
 diffuse, 211 
 Ostitis, 210 
 
 definition of, 147 
 Otic gangha, 32 
 
 Otitis media, oral infection and, 221 
 Otoliths, 32 
 
 Pain, definition of, 192 
 
 varieties of, 193 
 Palate bones, anatojny of, 34 
 
 hard, anatomy of, 37 
 
 process, 34 
 
 soft, anatomy of, 37 
 Palatine fossa, a,nterior, 22 
 
 posterior, 22 
 Papillae of tongue, 39 
 Parenchymatous inflammation, 136 
 Parotid glands, 43 
 "Path of least resistance," definition of, 
 
 143 
 Periapical infections, 204 
 acute, 206 
 
332 
 
 INDEX 
 
 Periapical infections, tooth apex in, 208 
 Peridental membrane, anatomy of, 47 
 bloodvessels of, 72 
 cells of, 71 
 cementoblasts of, 71 
 changes in, with age, 73 
 definition of, 67 
 epithelial elements of, 72 
 fibers of, 68 
 
 arrangement of, 68 
 fibroblasts of, 71 
 fuliction of, 72 
 histology of, 64, 67 
 inflammation of, differential 
 
 diagnosis of, 195 
 lymphatics of, 72 
 nerves of, 72 
 osteoblasts of, 71 
 white fibrous connective tissue 
 of, 68 
 Perilymph, 31 
 
 PQriodontitis, acute local, 195 
 chrojiic local, 195 
 general, 196 
 Periostitis, definition of, 147 
 Permanent teeth, extraction of, mal- 
 occlusion and, 127 
 Phagocytosis, definition of, 141 
 Pharyngeal topsil, 44 
 Pharyngitis, oral infection and, 221 
 Pointing, definition of, 143 
 PoUshing of teeth in prophylaxis, 261 
 brush-wheel in, 272 
 floss in, 272 
 system of, 263 
 Polymorphonuclear leukocytes, 137 
 Posterior fossa of skull, 19 
 nares, 23 
 palatine fossa, 22 
 Protruding teeth, definition of, 117 
 Pterygoid muscles, 93 
 Pulp, anatomy of, 46 
 laloodvessels of, 64 
 cavity, anatomy of, 46 
 chamber, anatomy of, 46 
 connective^tissue cells of, 64 
 function of , 66 
 histology of, 64 
 intercellular substance of, 64 
 lymplmtics of, 65 
 nerves of, 65 
 odontoblasts of, 64 
 Pulpitis, acute, 195 
 Pupil of eye, 28 
 Pyemia, 216 
 
 oral infection and, 222 
 Pyorrhea alveolaris, 166 
 definition of, 166 
 dental piopihylaxis and, 232 
 etiology of, 169 
 history of, 166 
 pathology of, 166 
 prevention of, 169 
 treatment of, 171 
 
 Refracting media of eye, 29 
 Repair of bone, 147 
 
 defiiiition of, 145 
 Retina, 28 
 
 Retruding teeth, definition of, 117 
 Rodents, teeth of, 88 
 Roof of mouth, anatomy of, 24 
 Root canals, anatomy of, 46 
 Rhinoceros, teeth of, 92 
 
 Sac, lachrymal, 29 
 Saccule, 32 
 Sagittal suture, 17 
 Saliva, constituents of, 150 
 decomposition of, 154 
 in dental caries, 182 
 Salivary glands, anatomy of, 43 
 Sanatoriums, dental hygienist in, 301 
 Sapremia, 217 
 Sella turcica, 19 
 
 Semicircular canals, anatomy of, 32 
 Sensation, causes of, 192 
 definition of, 192 
 laws governing, 192 
 Septicemia, definition of, 143 ^ 
 
 oral infection and, 222 
 Septum, nasal, 23 
 Serous exudation, definition of, 142 
 Seventh cranial nerve, anatomy of, 42 
 Sheaths of Newman, 61 
 Sinus, definition of, 144 
 
 sphenoidal, anatomy of, 25 
 SinuseSj frontal, anatomy of, 25 
 
 maxillary, anatomy of, 24 
 Skull, anatomy of, 17 
 
 anterior aspect of, 22 
 base of, 19 
 fossa of, anterior, 18 
 middle, 19 
 posterior, 19 
 lateral aspect of, 22 
 Snakes, teeth of, 82 
 Soft palate, anatomy of, 37 
 Spee, curve of, 10,0 
 Sphenoidal fissure, 19 
 
 sinus, anatomy of, 25 
 Sphenomandibular hgament, 94 
 Sphenomaxillary fissure, 22 
 Stylomandibular ligament, 94 
 Subungual fossse, 36 
 
 glands, 36, 44 
 Submaxillary glands, 36, 44 
 Superior maxillary bones, anatomy of, 33 
 Suppurative exudation, definition of, 142 
 
 inflammation, 136 
 Suspensory ligament of lens, 29 
 Sutures, coronal, 17 
 lambdoid, 17 
 sagittal, 17 
 
INDEX 
 
 333 
 
 Sword fish, teeth of, 92 
 Symphysis menti, 35 
 SyphiUs, dental prophylaxis and, 232 _ 
 Systemic infection, dental prophylaxis 
 and, 232 
 
 Tartar, chemistry of, 152 
 color of, 162 
 definition of, 149 
 development of, 157 
 formation of, 150 
 hardness of, 160 
 removal of, 160 
 solubihty of, 163 
 Tear gland, 29 
 Teeth, accretions on, 149 
 alveolar process of, 47 
 
 histology of, 74 
 anatomy of, 45, 47 
 apical foramen of, 46 
 arch of, definition of, 1 16 
 attachment of, 66 
 of baboon, 91 
 bicuspids, anatomy of, 50 
 
 occlusion of, 99 
 buccal surface of, definition of, 117 
 of bullfrog, 82 
 of carnivorous animals, 85 
 cementing substance of, 58 
 cementum of, anatomy of, 46 
 
 histology of, 61 
 of crocodiles, 82 
 cuspids, anatomy of, 49 
 deciduous, anatomy of, 56 
 
 premature loss of, malocclusion 
 and, 127 
 dentin of, anatomy of, 46 
 
 histology of, 60 
 
 secondary, histology of, 66 
 deposits on, 149 
 
 distal surface of, definition of, 116 
 of dogs, 87 
 of elephant, 92 
 enamel of, anatomy of, 46 
 
 histology of, 58 
 eruption of, approximate age for, 57 
 of fishes, 82 
 formation of, 75 
 forms of, evolution of, 80 
 functions of, secondary, 91 
 
 supplementary, 109 
 of horse, 92 
 histology of, 58 
 incisors, anatomy of, 47 
 inclined plane of, definition of, 116 
 infected, source of systemic disease, 
 
 213 
 labial surface ofj definition of, 117 
 of lemurs, 92 
 
 lingual surface of, definition of, 117 
 lower, occlusion of, 96 
 
 Teeth, malocclusion of, 112 
 classification of, 120 
 
 Angle's, 121 
 definition of, 119 
 etiology of, 126 
 
 extraction of permanent 
 
 teeth, 127 
 lack of use and, 128, 132 
 pernicious habits and, 127 
 premature loss of decidu- 
 ous teeth and, 127 
 growth of jaws in, 128 
 individual, 119 
 in school children, 310 
 as a masticating machine, 80 
 mesial surface of, definition of, 116 
 model of, definition of, 117 
 molars, lower, anatomy of, 54 
 occlusion of, 99 
 upper, anatomy of, 52 
 of monkey, 88 
 nomenclature of, 47 
 normal contacts in, 115 
 occlusion of, 45, 99 
 
 definition of, 116, 117 
 peridental membrane of, anatomy 
 of, 47 
 histology of, 64, 67 
 permanent, extraction of, mal- 
 occlusion and, 127 
 protruding, definition of, 117 
 pulp of, anatomy of, 46 
 cavity, anatomy of, 46 
 chamber, anatomy of, 46 
 histology of, 64 
 retruding, definition of, 117 
 of rhinoceros, 92 
 of rodents, 88 
 
 root canal of, anatomy of, 46 
 of snakes, 82 
 surfaces of, in dental prophylaxis, 
 
 238 
 of sword fish, 92 
 of turtles, 82 
 upper, occlusion of, 96 
 of walrus, 92 
 Temporal muscle, 93 
 Temporomaxillary articulation, 36 
 Tenon, capsiile of, 26 
 Tic douloureux, 198 
 Tissue stimulation in dental prophylaxis, 
 
 276 
 Tomes, granular layer of, 61 
 Tongue, anatomy of, 38 
 
 papillae of, 39 
 Tonsil, lingual, 40 
 Tonsillitis, oral infection and, 221 
 Tonsils, anatomy of, 44 
 Tooth germ, formation of, 75 
 Tooth-brushes, dental prophylaxis and, 
 
 278 _ 
 Toxemia, 216 
 
 oral infection and, 222 
 Trifacial nerve, anatomy of, 40 
 
334 
 
 INDEX 
 
 Tuberculosis, dental prophylaxis and, 
 
 232 
 Turkish saddle, 19 
 Turtles, teeth of, 82 
 Tympanic membrane, 30 
 
 U 
 
 Ulcer, definition of, 144 
 Ulcerative inflammationi 136 
 Upper teeth, occlusion of, 96 
 Utricle, 32 
 
 Vascular coats of eye, 27 
 Vitreous humor, 29 
 
 W 
 
 Walrus, teeth of, 92 
 Wharton's duct, 36 
 
 Zygomatic fossa, 22 
 
RK53 
 Fones 
 
 l2^ hygiene. 
 
 P73 
 1921 
 
 
 ^/, 
 
 > 
 
 )yi^ 
 
 
 JAN 2 1-1949 
 
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 ^^^ 
 
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