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Descriptive Anatomy 
 
 OF THE 
 
 Human Teeth. 
 
 FOURTH EDITION. i 
 
 BY 
 
 G. V. BLACK, M.D., D.D.S., ScD. 
 
 philadelphia, pa.: 
 
 The S. S. White Dental Manufacturing Co. 
 igo2. 
 
IS? 7 
 
 Copyright, 1S97, bv 
 
 The S. S. White Dental Manufacturing Co. 
 
 philadelphia. 
 
PREFACE TO THE FIRST EDITION. 
 
 BY my experience as a practitioner, as a teacher, and in my 
 intercourse with fellow-practitioners, I have become 
 convinced of a serious defect in the teaching of the 
 details of the anatomy of the teeth, and in the system- 
 atization of the terms used in their description. This defect 
 has been a constant drawback at the chair, in the laboratory, 
 and most of all, in' the college. The object of the present 
 volume is to remedy, in a measure, this defect. To this end I 
 have had constantly in view the needs of the dental student and 
 practitioner. 
 
 We have heretofore had excellent general descriptions in 
 human and comparative dental anatomy; but these have dealt 
 principally with the general forms of the dentitions of the 
 mammalia and other orders of animate beings, rather than with 
 specific descriptions of the forms of the various surfaces and 
 surface markings, making up the sum of the forms of the 
 individual teeth of man. Valuable as these works have been, 
 they. have left the acquirement of a knowledge of the details of 
 the specific forms of the humqn teeth mostly to individual 
 observation. By this means, many have attained to an excel- 
 lent perception of the various forms of the human teeth ; but it 
 is not reasonable to suppose the profession generally will do 
 this without some fixed guide. What the dental student wants 
 most in the college, and in the office, is a systematized nomen- 
 clature of the several parts of the teeth in detail ; and such a 
 description as will call his attention successively to every part 
 of each tooth, as Gray, in his Anatomy, has called attention to 
 every part of each bone, however apparently unimportant. It 
 should be remembered that anatomy is not to be learned from 
 books alone, but also by bringing the parts to be studied into 
 view, and closely examining them in connection with the 
 
IV PREFACE. 
 
 descriptions given. Anyone who may read the present vol- 
 ume without a reasonable number of human teeth of each 
 denomination before him for examination and comparison, 
 will be but partially benefited. 
 
 It has been my object to systematize the nomenclature 
 most in vogue with the profession, whenever practical, rather 
 than to introduce new terms. However, the reader will find 
 a few new terms, and possibly a few old ones that are used 
 differently from the former custom. The terms up and down, 
 to indicate direction or parts of teeth, are abandoned, because 
 of their ambiguity. In a few instances, new forms of old 
 words have been used, especially to avoid the terms inner, 
 outer, backward, forward, etc., which are so often misleading. 
 The words mesial, distal, labial, buccal, lingual, etc., are used 
 as adverbs of direction by adding ly, or the same thing is 
 accomplished by the use of the preposition to. It is as easy 
 to say of a cavity that it extends far beyond, beyond, to, nearly 
 to, or to the gingival line, as to say it extends up or down, etc., 
 and the meaning will not be mistaken; or to say that a cavity 
 extends distally, or to the distal, or lingually, or to the lingual, 
 instead of backward, or inward, either of which has different 
 meanings in different situations. The best rule is to use no 
 extraneous object in the designation of the parts of, or direc- 
 tion on, the surface of a tooth ; but to confine the phraseology 
 to the specific and well-defined terms applied to its several 
 parts. The back part of a molar would not mean the same 
 relative part as the back part of an incisor. In many such 
 ways the author has endeavored to systematize, and make 
 more definite, the phraseology applied to the teeth without 
 going to extremes, knowing well that forms of language once 
 in use can be improved more easily than they can be displaced 
 by new terms, though more exact. 
 
 The absence of a Bibliography may be noted. The plan 
 and object of this work has not seemed to call for many refer- 
 ences to authorities. This does not imply, however, that 
 authors who have preceded me, as Fox, Carabelli, Tomes, 
 
PREFACE. V 
 
 Wedl, Judd, Wortman, and many others, to whom we are 
 greatly indebted, have been either overlooked or ignored. 
 
 The illustrations have all been made by the author for the 
 purpose of illustration, rather than as works of art. After 
 experimenting with the various plans of the management of 
 light and shade, diffused light has been used because more 
 detail could be shown, especially in the difficult task of illus- 
 trating the occlusal surfaces of the teeth. Each picture of a 
 tooth, in all its details, is drawn from accurate measurements 
 of the particular tooth in hand. 
 
 Much of dental histology might properly find place in 
 this book; but that subject is well represented by others. Mal- 
 forms of the teeth, supernumerary teeth, and variations of 
 arrangement, belong to the subject of irregularities, which is 
 amply treated by several authors. My aim has been to confine 
 the book strictly to normal macroscopic anatomy. However, 
 a very serious difficulty, which has always met the dental 
 anatomist, has been the variations of form in teeth of the same 
 denomination. The endeavor has been to systematize these 
 under one, two or more typical forms of each tooth, or its 
 lobes, and point to the character of the changes which occur. 
 This has occasionally led to the mention of abnormal form.s. 
 
 The reader will find scattered through the work some 
 hints with regard to the practical bearing of anatomical points 
 on operative procedures, which, it is hoped, will be of value. 
 
PREFACE TO THE SECOND EDITION. 
 
 THE rapid sale of the first edition of this work has shown 
 an appreciation of a need for a more complete anatom- 
 ical description of the human teeth. In preparing the 
 work for a second edition, the aim has been to render 
 the original design more complete in its details, and to make 
 such verbal alterations as would better fit it for the text-book 
 for the college, and for reference by the practitioner. The 
 most notable changes are in the section on nomenclature ; and 
 these are confined to additional explanations of words and 
 phrases. For the convenience of students a brief glossary has 
 been added. 
 
 A number of the illustrations have been redrawn, and one 
 has been added. Some of the numbers of the illustrations have 
 been changed to render them consecutive ; but the numbering 
 of the paragraphs remains unchanged. Important words, espe- 
 cially the subjects of paragraphs and technical words the first 
 time used, have been printed in bold-faced type. This, it is 
 hoped, will be of advantage to the student and especially con- 
 venient for reference. 
 
 Valuable aid in the preparation of the work for reissue has 
 been rendered by Mr. I. W. Davenport, Drs. D. M, Cattell, 
 Edmund Noyes, and C. N. Johnson. G. V. B. 
 
 Jacksonville, III., July 15th, i8gi. 
 
PREFACE TO THE THIRD EDITION. 
 
 THE continued favor with which this work is received by 
 the profession has made another edition necessary. In 
 preparing this the endeavor has been to improve the 
 detail without changing the form. The principal changes 
 will be found in the nomenclature. The steady progress of 
 dental nomenclature toward more exact forms demands this. 
 It must now be recognized that we have two distinct forms of 
 dental nomenclature, the one used in comparative dental anat- 
 omy, the other in human dental anatomy for the purposes of 
 dentistry. The one is adapted to the description of the teeth of 
 the various animals, including the teeth of man when his teeth 
 are treated of in the comparative sense ; the other is suited to 
 the teeth of man when the more exact and detailed descriptions 
 necessary to operative dentistry are presented. These word- 
 forms necessarily become the basis of much of the nomencla- 
 ture of operative dentistry. An extended examination of dental 
 literature shows that up to a recent period, writers on operative 
 dentistry had named more than twice as many points on the 
 teeth than had writers on dental anatomy. This fact shows the 
 necessity that had existed for the more extended and systema- 
 tized presentation of the subject of dental anatomy, and the 
 closer systematization of its nomenclature. However, the 
 reader will find the changes introduced limited to one new word, 
 axial; two new word-forms, occlusal in place of occluding, 
 and incisal in compound forms, and the completion of the sys- 
 tematization of the names of the angles of the teeth. This 
 latter has required but few word changes in the text. 
 
 Improvement has also been made in some of the descrip- 
 tions, and a number of new illustrations have been added. 
 
 G. V. B. 
 
 Jacksonville, III., August 21st, 1894. 
 
PREFACE TO THE FOURTH EDITION. 
 
 ON account of the exhaustion of the very large third 
 edition of this work a fourth has become necessary. 
 The teacher and the student will find but few 
 changes. The author takes pride in referring to the 
 very general approval of the work as a text-book, and to the 
 fact that teachers who have used it in their classes since the 
 first edition have so few changes to suggest. 
 
 The changes in this edition consist in the introduction of 
 tables of the angles of teeth and the angles of surfaces of teeth, 
 intended to aid the student in fixing these in his mind, and in 
 the introduction of the word embrasure as an additional techni- 
 cal term. "^ 
 
 Those openings between the angles of the teeth formed by 
 the rounding of the proximate surfaces toward the buccal on 
 the one side of the proximate contact and toward the lingual 
 upon the other have never had a specific name, and the word 
 embrasure has been introduced to supply this need in nomen- 
 clature. The word, when traced to its derivation, means an 
 opening that widens, as in a wall, whether outward or inward. 
 It has been most used in connection with defensive works ; as 
 "embrasures for cannon" in the walls of forts ; though it fre- 
 quently occurs in descriptions of other structures. The gen- 
 eral progress of dental nomenclature toward exactness is very 
 gratifying, and it is hoped that the addition of this word will be 
 found advantageous. G. V. B. 
 
 Chicago, October gth. 1807 
 
GLOSSARY 
 
 Alveolus. (PI. Alveoli.) A socket: The cavity in the 
 process of the maxillary bone in which the root of a tooth is 
 fixed. 
 
 Alveolar process. The projection of the maxillary 
 bones which envelops the roots of the teeth and forms their 
 alveoli. 
 
 Angle. The line, or point, where two or more surfaces 
 of the teeth join. The mesial and buccal surfaces join in the 
 formation of the mesio-buccal angle. (See Par. 7.) 
 
 Apex. The terminal end of the root of a tooth. 
 
 Apical foramen. The minute opening of the pulp canal 
 at the apex of the root of a tooth. (See Par. 153.) 
 
 Apical space. The space between the bone, or wall of 
 the alveolus, and the apex of the root of a tooth. This space 
 is filled with the soft tissues of the peridental membrane, and is 
 the seat of alveolar abscess. 
 
 Axial angle. The line angles that are parallel with the 
 long axes of the teeth are called axial angles. They are the 
 mesio-buccal, and mesio-labial. disto-buccal, and disto-labial, 
 mesio-lingual and disto-lingual angles. 
 
 Axial surfaces. Those surfaces of the teeth that are 
 parallel with their long axes. They are labial, buccal, lingual, 
 mesial, and distal surfaces. 
 
 Axial walls. Of pulp chambers. Those walls that are 
 parallel with the long axes of the teeth ; the mesial, distal, buc- 
 cal, and lingual walls. 
 
 Bell-crowned. A tooth in which the mesio-distal diam- 
 eter of the crown is much greater than that of the neck. 
 
GLOSSARY. 
 
 Bicuspid. A tooth with two cusps. They are also called 
 pre-molars. There are eight bicuspids ; two on each side of the 
 upper jaw, and two on either side of the low^er jaw. They are 
 named right and left upper first and second, and right and left 
 lower first and second bicuspids. They are situated between 
 the cuspids and molars. 
 
 Border of the alveolar process. The thin edge of 
 the alveolar process surrounding the necks of the teeth. 
 
 Buccal. Pertaining to the cheek. Toward the cheek. 
 
 Buccal surface. The surface of a tooth next to the 
 cheek. 
 
 Buccal-gingival ridge. A prominent ridge near the 
 gingival line on the buccal surface of the deciduous molars. It 
 is especially prominent on the first deciduous molars. 
 
 Bucco-lingual. From the cheek toward the tongue; as 
 the bucco-lingual diameter of the crown of a lower first molar. 
 
 Canal. See Root Canal. 
 
 Cementum. A tissue resembling bone which forms the 
 outer surface of the roots of the teeth. 
 
 Contact point. The point on the proximate surface of 
 a tooth which touches a neighboring tooth. 
 
 Crown. That portion of a tooth which is covered with 
 enamel, and which projects from the tissues in which the root 
 is fixed. 
 
 Cutting edge. The edge formed by the junction of the 
 labial and lingual surfaces of the incisor and cuspid teeth. In 
 the cuspids the edge is raised to a point near its center. 
 
 Cusp. A pronounced elevation, or point, on the surface 
 of a tooth, more especially on the occlusal surface. 
 
 Cuspid. A tooth with one point, or cusp. There are 
 four cuspids: one on either side in each jaw, situated at the 
 corners of the mouth. 
 
 Deciduous teeth. The teeth of the child which are 
 shed to give place to the permanent teeth. They are also called 
 temporary teeth. 
 
 Dentine. The tissue of which the main body of a tooth 
 is formed. 
 
GLOSSARY. 
 
 Developmental grooves. Fine depressed lines in the 
 enamel of a tooth which mark the junction of its lobes. (See 
 Pars. 21 and 69.) 
 
 Developmental lines. See developmental grooves. 
 
 Distal. Away from the median line of the face follow- 
 ing the curve of the dental arch. The surface of a tooth most 
 distant from the median line. (See Par. 5.) 
 
 Distally. A direction away from the median line of the 
 face following the curve of the dental arch. 
 
 Distal angle. A contraction of disto-incisal angle. 
 Used, also, instead of disto-bucco-occlusal angle {q. v.). 
 
 Disto-buccal angle. The angle formed by the union 
 of the distal and buccal surfaces of the bicuspids and molars. 
 
 Disto-bucco-occlusal angle. The angle or corner of 
 a bicuspid or molar tooth formed by the junction of the angles 
 of its distal, buccal, and occlusal surfaces at a point. 
 
 Disto-incisal angle. The angle or corner of an incisor 
 or cuspid tooth formed by the jvmction of the distal surface and 
 cutting edge, or incisal surface. 
 
 Disto -labial angle. The angle formed by the union of 
 the distal and labial surfaces of the incisors and cuspids. 
 
 Disto-lingual angle. The angle formed by the union of 
 the distal and lingual surfaces of any of the teeth. 
 
 Disto-linguo-occlusal angle. The angle or corner of 
 a bicuspid or molar tooth formed by the junction of the angles 
 of its distal, lingual, and occlusal surfaces at a point. Rarely 
 used. 
 
 Disto-occlusal angle. The angle formed by the union 
 of the distal and occlusal surfaces of the bicuspids and molars. 
 
 Embrasure. An opening that widens outward or in- 
 ward ; as an opening in a wall for cannon. That portion of the 
 inter-proximate space that widens toward the buccal or labial, 
 or toward the lingual. 
 
 Enamel. A very hard tissue covering the crown of a 
 tooth. 
 
 Fissure. A fault in the surface of a tooth caused by 
 
GLOSSARY. 
 
 the imperfect joining of the enamel of the different lobes. 
 Fissures occur along the lines of the developmental grooves. 
 > / Fossa. (PI. Fossae.) A round or angular depression in 
 
 the surface of a tooth. Fossae occur mostly in the occlusal sur- 
 faces of the molars, and in the lingual surfaces of the incisors. 
 
 Gingiva. (PI. Gingivae.) The portion of gum tissue 
 enveloping the necks of the teeth crown-wise from the attach- 
 ment at the gingival line. The free margin of the giim. 
 
 Gingival. Pertaining to the gingival line; as the curva- 
 ture of the gingival line, gingival margin, etc. 
 
 Gingival curvature. The deviation of the gingival line 
 from the horizontal in its course around the neck of a tooth. 
 
 Gingival line. The line around the neck of a tooth at 
 which the gingiva is attached. The line of junction of the 
 enamel and cementum. 
 
 Gingival margin. The portion of the crown of a tooth 
 next to the gingival line. 
 
 Gingivally. A direction from any part of the crown 
 toward the gingival line of the tooth. 
 
 Groove. A long-shaped depression in the surface of a 
 tooth. (See Par. ii.) 
 
 Horn. A slender, or blunt pointed process of the pulp 
 of a tooth extending toward the point of a cusp. 
 
 Incisal. The cutting edges of the incisors and cuspids 
 are regarded as incisal surfaces. 
 
 Incisal margin. That margin of a surface of an incisor 
 or a cuspid tooth formed by the incisal surface or cutting edge ; 
 as the incisal margin of the labial surface of the central incisor. 
 
 Incisor. A tooth with a cutting edge. There are four 
 incisors in the upper jaw, and four in the'lower jaw. They are 
 called the upper and lower right and left central, and the upper 
 and lower right and left lateral, incisors. 
 
 Inclination. Of a tooth : The deviation of the long axis 
 of a tooth from the perpendicular line ; as the mesial inclination 
 
GLOSSARY. Xlir 
 
 of the incisors. (See Par. 191.) Of a surface: The deviation 
 of a portion of the surface of a tooth from the general plane of 
 that surface. 
 
 Incline. See Inclination. 
 
 Inter-proximate embrasure. That portion of the inter- 
 proximate space which widens toward the buccal or labial, or 
 toward the lingual. (See Par. 194.) 
 
 Inter-proximate space. The V-shaped space bounded 
 by the proximate surfaces of adjoining teeth, and the border of 
 the septum of the alveolar process between their necks. Nor- 
 mally this space is filled with gum tissue. (See Par. 193.) 
 
 Labial. Pertaining to the lips. Toward the lips. 
 
 Labial surface. The surface of a tooth next to the lips. 
 The incisors and cuspids have labial surfaces. 
 
 Labially. A direction toward the lips. 
 
 Labio-lingual. From the lips toward the tongue; as 
 the labio-lingual diameter of the central incisor. 
 
 Labio-lingually. A direction from the lips toward the 
 tongue. 
 
 Line angles. Of the teeth : Those angles formed by 
 the junction of two surfaces along a line; as the mesio-buccal 
 angle, disto-buccal angle, etc. 
 
 Lingual. Next to, or toward the tongue; as lingual 
 surface. 
 
 Lingually. A direction toward the tongue. 
 
 Lingual surface. A surface of a tooth next to the 
 tongue. All of the teeth have lingual surfaces. 
 
 Linguo-gingival fissure. A fissure occurring occa- 
 sionally in the lingual surface of the upper incisors. It usually 
 separates the lingual lobe from one of the marginal ridges and 
 extends into the cemehtum. (See Fig. 10.) 
 
 Linguo-gingival ridge. A ridge near the gum on the 
 lingual surface of the incisors and cuspids. It is on the lingual 
 lobe. (See Par. 21.) 
 
 Lobe. A division of a tooth formed from a separate 
 ^ point of the beginning of calcification. (See Pars. 21 and 69.) 
 
XIV GLOSSARY. 
 
 Mammelons. The three rounded prominences seen on 
 the cutting edges of the incisors when they first come through 
 the gums. (E. Magitot.) 
 
 Marginal ridge. The ridges, or elevations of enamel 
 on the margins of the occlusal surface of the bicuspids and 
 molars, and on the mesial and distal margins of the lingual 
 surface of the incisors and cuspids. 
 
 Median line. The antero-posterior perpendicular cen- 
 tral line of the body. 
 
 Mesial. Toward the median line. Those surfaces of the 
 teeth which, as they stand in the arch, and following its curve, 
 are toward the median line, are called mesial surfaces. 
 
 Mesial angle. A contraction of mesio-incisal angle, also 
 of mesio-bucco-occlusal angle {q. v.). 
 
 Mesially. Toward the median line. 
 
 Mesio-buccal angle. The angle formed by the union of 
 the mesial and buccal surfaces of the bicuspids and molars. 
 
 Mesio-bucco-occlusal angle. The angle or corner 
 formed by the junction at a point of the angles of the mesial, 
 buccal, and occlusal surfaces of the bicuspids and molars. 
 
 Mesio-distal. From mesial to distal; as, the mesio- 
 distal diameter of the lower first molar. 
 
 Mesio-incisal angle. The angle or corner formed by 
 the junction of the mesial surface and cutting edge, or incisal 
 surface, in the incisors and cuspids. 
 
 Mesio-labial angle. The angle formed by the union of 
 the mesial and labial surfaces of the incisors and cuspids. 
 
 Mesio-lingual angle. The angle formed by the union 
 of the mesial and lingual surfaces of the teeth. 
 
 Mesio-lingual groove. A developmental groove run- 
 ning from the mesial surface diagonally to the lingual surface 
 in upper first molars that have the fifth cusp. (See Par. 69.) 
 
 Mesio-linguo-occlusal angle. The angle or corner 
 formed by the junction of the angles of the mesial, lingual, and 
 occlusal surfaces of the bicuspids and molars. Rarely used. 
 
GLOSSARY. XV 
 
 Mesio-occlusal angle. The angle formed by the union 
 of the mesial and occlusal surfaces of the bicuspids and molars. 
 
 Neck. That portion of the tooth which forms the junc- 
 tion of the crown and root. 
 
 Oblique ridge. A ridge running obliquely across the 
 occlusal surface of the upper molars. It is formed by the 
 union of the triangular ridge of the disto-buccal cusp with the 
 distal portion of the ridge forming the mesio-lingual cusp. 
 
 'Occlude. To shut. To close. 
 
 Occlusal surface. That surface of a bicuspid or molar 
 tooth that makes contact with a tooth of the opposite jaw when 
 the mouth is closed. 
 
 Permanent teeth. The teeth of adult age as distin- 
 guished from the temporary, or deciduous teeth. 
 
 Pit. A sharp, pointed depression in the enamel. Pits 
 occur mostly where several developmental grooves join; as in 
 the occlusal surfaces of the molars, and at the endings of the 
 ^ buccal grooves on the buccal surfaces of the molars. 
 / ^ Point angles. Of the teeth : Those corners or angles 
 
 formed by the junction of the angles of three surfaces at a 
 point; as the disto-bucco-occlusal angle, the mesio-bucco- 
 occlusal angle, etc. 
 
 Point of proximate contact. The point at which the 
 proximate surface of a tooth touches the proximate surface of 
 a neighboring tooth. 
 
 Proximate contact. The contact, or touching-, of the 
 proximate surfaces of neighboring teeth. 
 
 Proximation. The near approach, or contact, of the 
 proximate surfaces of neighboring teeth. 
 
 Proximate surface. The surface of a tooth which lies 
 next to another tooth. (See Par. 5.) 
 
 Pulp. The soft tissue that fills the pulp chambers and 
 root canals of the teeth. 
 
 Ridge. A long-shaped elevation on the surface of a tooth. 
 
 Root. That portion of the tooth that is fixed in the bony 
 walls of the alveolus, or socket ; and is covered with cementum. 
 
XVI GLOSSARY. 
 
 Root canal. The opening through the center of the 
 long axis of the root of a tooth from the crown to the apex. 
 
 Rugae. A series of irregular ridges in the roof of the 
 mouth. 
 
 Septum. (PI. Septa.) A partition : That portion of ths 
 alveolar process which lies between the roots of the teeth sepa- 
 . rating their alveoli. 
 
 Succedaneous teeth. Those of the permanent teeth 
 which succeed, or take the places of, the temporary teeth. 
 
 Sulcate groove. A groove following the bottom of a 
 1/ sulcus. 
 
 Sulcus. (PI. Sulci.) A notable long-shaped depression 
 in the surface of a tooth the inclines of which meet at an angle. 
 A sulcus has a developmental groove at the junction of its 
 inclines. 
 
 Supplemental groove. "A shallow long-shaped depres- 
 sion in the surface of a tooth, generally with a smoothly 
 rounded bottom. Supplemental grooves differ from develop- 
 mental grooves in that they do not mark the junction of lobes. 
 
 Supplemental lobe. A lobe that does not belong to the 
 typical form of the tooth ; an additional lobe. 
 
 Supplemental ridge. A ridge on the surface of a tooth 
 that does not belong to the typical form of the tooth ; and addi- 
 tional ridge. 
 
 Temporary teeth. See deciduous teeth. 
 
 Thick-necked. A tooth in which the mesio-distal diam- 
 eter of the neck is nearly equal to that of the crown. (See bell- 
 crown. ) 
 
 Thirds. Division of a crown of a tooth; as to length, 
 into occlusal, or incisal third, middle third, and gingival third; 
 as to mesio-distal breadth, into mesial third, middle third, and 
 distal third. 
 
 Transverse ridge. A ridge formed of two triangular 
 ridges, which join to form a continuous ridge across the oc- 
 clusal surface of a tooth. 
 
GLOSSARY. Xvii 
 
 Triangular ridge. A ridge running from the point of a 
 cusp toward the central portion of the occlusal surface of a 
 tooth. 
 
 Tubercle. A slight rounded elevation on the surface of a 
 tooth. Tubercles occur frequently on the linguo-gingival ridge 
 of the incisors, and occasionally upon various parts of other 
 teeth. They are deviations from the typical tooth forms. 
 
DENTAL ANATOMY. 
 
 XOMENCLATURE. 
 
 1. Man's food is both animal and vegetable, and his 
 teeth are so formed as to enable him to readily masticate either 
 kind ; therefore, his teeth differ from those of both the carnivor- 
 ous and herbivorous animals, and form the type of the om- 
 nivora. They are formed for cutting, tearing, and comminut- 
 ing many kinds of food. The incisors, situated anteriorly, 
 have edges for cutting; the cuspids and bicuspids, at the an- 
 gles of the mouth, have fairly sharp, though not very long, 
 points or cusps, suited for tearing; while the molars, situated 
 in the posterior part of the mouth, have broad, tuberculated 
 surfaces, which serve well to grind or comminute the more 
 solid masses. The forms of the teeth of man indicate a design 
 that his food should be taken in rather small masses, consid- 
 ered -from the standpoint of the habits of animals in general, 
 and that it should be very thoroughly commingled with saliva 
 before being passed to the stomach. 
 
 2. The adult has thirty-two teeth : four incisors, two 
 cuspids, four bicuspids, and six molars in each jaw. Scientific 
 men express the denomination and number of the teeth of the 
 mammalia by formulae, in which the denomination is repre- 
 sented by the initial letter, followed by a horizontal line, with 
 the number of that kind of teeth on one side of the upper jaw 
 written above the line, and the number in the lower jaw written 
 below the line. The dental formula of man is written thus : 
 
 I I C i B f M I = 32. 
 
 This formula is read thus : Incisors, two upper and two lower ; 
 cuspids, one upper and one lower ; bicuspids, two upper and 
 
NOMENCLATURE. 
 
 two lower ; molars, three upper and three lower ; sixteen on 
 one side. As the opposite side has the same, the full number 
 is thirty-two. The teeth are composed of four tissues : Enamel, 
 which covers the crown ; dentine, which forms the body of 
 both crown and root; cementum, which covers the root and 
 joins with the enamel at the gingival line, or neck of the tooth; 
 and pulp tissue which fills the central cavity of the dentine. 
 
 3. Each tooth presents for description certain characters 
 common to all, such as crown, neck or gingival line, root, pulp- 
 chamber, canal, and surfaces of crown and root. The crown 
 of a tooth is that part which projects beyond the gum tissue, 
 and is covered with enamel; while the root, covered with ce- 
 mentum, is that portion fixed in the bony process of the jaw, 
 by which the whole tooth is held securely in position. The 
 root of a tooth may be single, as in the incisors and cuspids; 
 divided into two roots as in the lower molars ; or into three 
 roots, as in the upper molars ; or into a greater number, as in 
 exceptional examples. The root is divided into the body, or 
 main portion; the Apex, or terminal end of a root; and the 
 neck, which marks the junction of the root with the crown. 
 A tooth is also marked with a slight constriction at the neck, 
 and by the junction of the enamel with the cementum. The 
 latter, which forms a visible line encircling the tooth, is called 
 the gingival line. It is so curved in its course as to present 
 a convexity toward the crown on the proximate surfaces, to 
 correspond with the line of the gum as it passes over the alveo- 
 lar ridge from the labial to the lingual side of the arch. On 
 the anterior teeth, it is also so curved in passing the labial and 
 lingual surfaces as to present a concavity toward the crown. 
 These are called the curvatures of the gingival line, or the 
 gingival curvature. The neck of a tooth is common to all 
 of the roots, whatever the number, for the point of division into 
 two or more roots is always rootward from the neck. 
 
 4. The crowns of the incisors and cuspids present for 
 examination four surfaces and an edge ; and the crowns of the 
 
NOMENCLATURE. 
 
 bicuspids and molars, five surfaces. (Diagram A.) These 
 surfaces are named according to their position and use. Those 
 of the incisors and cuspids presenting toward the Hps, are 
 called labial surfaces ; those of the bicuspids and molars pre- 
 senting toward the cheek, buccal surfaces ; all presenting 
 toward the tongue, lingual surfaces, whether in the upper or 
 the lower jaw.* Those surfaces which come in contact with 
 the opposing teeth in closing the mouth are called occlusal 
 surfaces. These surfaces of the bicuspids and molars are also 
 called grinding surfaces. 
 
 5. The surfaces of the teeth that present toward, or lie 
 against, adjoining teeth are called proximate or proximal, 
 surfaces. The proximate surfaces are also more closely de- 
 fined by the terms mesial and distal. These terms have spe- 
 cial reference to the position of the surface relative to the cen- 
 tral or the median line of the face. This line is drawn along, 
 the suture uniting the superior maxillary bones, or perpendic- 
 ularly through the center of the face and mouth, and passes 
 between the central incisors of both the upper and lower jaws. 
 Those proximate surfaces which, as they are placed in the arch, 
 and follozving its curve, are toward the median line, are called 
 mesial surfaces ; and those most distant from the median 
 line are called distal surfaces. The mesial surfaces of the 
 central incisors, both upper and lower, proximate each other; 
 but in all other cases a mesial surface proximates a distal. 
 Also, a distal surface always proximates a mesial surface, 
 except those of the third molars, upper and lower, which have 
 no distal proximating teeth. The points at which the proxi- 
 mate surfaces touch each other as the teeth stand in the line of 
 the arch, are called the points of proximate contact, or sim- 
 ply contact points. 
 
 For convenience in designating the different parts of the 
 crowns of the teeth, they may be divided into thirds, in any 
 
 * Some authors use the term "palatine surfaces" for those of the 
 upper jaw, and "lingual" for those of the lower. This seems unneces- 
 sary. 
 
NOMENCLATURE. 
 
 one of .three directions : Inciso- or occluso-gingivally into incisal, 
 or occlusal third, middle third, and gingival third,'^mesio-dis- 
 tally into the mesial third, middle third, and distal third ; bucco- 
 lingually into the buccal third, middle third, and lingual third. 
 
 Each of the five surfaces may be divided into thirds in 
 either one of two directions. The labial, or buccal, and the 
 lingual surfaces are divided inciso- or occluso-gingivally, into 
 the incisal, or occlusal third, middle third, and gingival third ; 
 mesio-distally into the mesial third, middle third, and distal 
 third. Mesial and distal surfaces are divided inciso- or oc- 
 cluso-gingivally into the incisal, or occlusal third, middle third, 
 and gingival third ; bucco-lingually, into the buccal third, mid- 
 dle third, and lingual third. The occlusal surfaces are divided 
 'mesio-distally into the mesial third, middle third, and distal 
 third ; bucco-lingually, into the buccal third, middle third, and 
 lingual third. The cutting edges, or incisal surfaces of the 
 incisors and cuspids, are divided mesio-distally only. These 
 divisions are the mesial third, middle third, and distal third. 
 
 6. The incisors present a cutting edge by the junction 
 of the labial and lingual surfaces along a line. In the cuspids, 
 this joining of the surfaces to form an edge is raised to a point 
 near the center of its length, forming a cusp, hence the term 
 cuspid, a tooth with one point. The cutting edges of the in- 
 cisors, and the occlusal surfaces of the bicuspids and molars, 
 come in contact with the similar surfaces of the teeth of the 
 opposing jaw when the mouth is closed, as in the act of biting. 
 The incisors and cuspids of the upper jaw do not occlude ex- 
 actly on the cutting edges or cusps, but generally just back of 
 them ; though for convenience, the term occlusal may be ap- 
 plied to them as if they did, though they will generally be called 
 cutting edges, and the adjective form incisal will be used 
 in all compound words. The occlusal surfaces of the bicuspids 
 have two cusps, hence the term bicuspid, a tooth with two 
 points ; and the occlusal surfaces of the molars have four cusps 
 and sometimes more. 
 
NOMENCLATURE. 
 
 7. The angles of the teeth are of two kinds : Line 
 angles and point angles. The line angles are formed by the 
 junction of two surfaces along a line. The point angles are 
 formed by the junction of three surfaces forming a corner. The 
 incisors and cuspids have four, and the bicuspids and molars 
 have eight line angles. Angles are named by combining in a 
 compound word the names of the surfaces which join to form 
 the angle. The incisors and cuspids have mesio-labial angles, 
 which extend from the cutting edge to the gingival line along 
 the line of union of the mesial and labial surfaces. Also, 
 disto-labial angles, mesio-lingual angles, and disto-lingual 
 angles, formed similarly by the junction of the surfaces named 
 in these compound words. 
 
 The bicuspids and molars have mesio-buccal angles, 
 formed by the junction of the mesial and buccal surfaces along 
 a line from the occlusal surface to the gingival line. Also, 
 disto-buccal angles, mesio-lingual angles, and disto-lingual 
 angles, all of which are formed in the same manner as the 
 mesio-buccal. These are called the axial line angles because 
 they are parallel with the long axes of the teeth. 
 
 The bicuspids and molars have also four occlusal line an- 
 gles,' which are, however, more generally called marginal 
 ridges. The mesio-occlusal angles extend bucco-lingually 
 along the line of junction of the mesial and occlusal surfaces. 
 The disto-occlusal angles are similarly formed. The bucco- 
 occlusal angles and the linguo-occlusal angles extend mesio- 
 distally along the line of junction of the surfaces named in 
 these compound words. 
 
 The point angles of the bicuspids and molars are four 
 occlusal and four gingival. As these are formed by the junc- 
 tion of the angles of three surfaces forming a corner, their 
 names are compounds of the names of the three uniting sur- 
 faces. The mesio-bucco-occlusal angles are formed by the 
 junction of the angles of these three surfaces at a point. The 
 mesio-linguo-occlusal angles, the disto-bucco-occlusal 
 angles, and the disto-linguo-occlusal angles are formed in a 
 
NOMENCLATURE. 
 
 V 
 
 similar manner. These names of point angles are precisely the 
 same for all of the bicuspid and molar teeth. 
 
 The incisors and cuspids have, on account of their wedge- 
 like form, but two incisal point angles. These are the mesio- 
 incisal and disto-incisal angles, which form the corners at 
 the mesial and distal terminations of the incisal surface or cut- 
 ting edge. 
 
 The gingival point angles represent the corners of the 
 crowns of the teeth at their junction with the roots at the gingi- 
 val line, or the gingival termination of the axial line angles ; 
 and are named precisely as the axial line angles, with the addi- 
 tion of the word gingival. Thus, the incisors and cuspids 
 have mesio-labio-gingival angles, mesio-linguo-gingival an- 
 gles, disto-labio-gingival angles, and disto-linguo-gingival 
 angles. These angles are named in the same way for the bicus-. 
 pids and molars, except that the word buccal is substituted for 
 labial; thus, mesio-bucco-gingival angle, disto-bucco-gin- 
 gival angle, the angles on the lingual being named as in the 
 incisors. Up to the present time the gingival point angles have 
 not been used in descriptions of the teeth, and are given here 
 only for the sake of completeness. 
 
 When any individual surface of a tooth is considered alone 
 it is regarded as having margins and angles of its own, or be- 
 longing to it. Each margin is designated by the name of the 
 surface with which it is joined, except that toward the gingival 
 line, which takes the name gingival margin. The buccal sur- 
 face of a bicuspid or molar has a gingival margin, a mesial 
 margin, a distal margin, and an occlusal margin. The labial 
 surface of an incisor has a gingival margin, a mesial 
 margin, a distal margin, and an incisal margin. The margins 
 of the lingual surfaces of all of the teeth are named in precisely 
 the same terms as those of their buccal or labial surfaces. Also, 
 the margins of mesial and distal surfaces are named in the same 
 terms. A mesial or distal surface of a bicuspid or molar has a 
 gingival margin, a buccal margin, a lingual margin, and an 
 occlusal margin. The mesial and distal surfaces of the incisors 
 
NOMENCLATURE. 
 
 and cuspids have, on account of their triangular form, only- 
 three margins: the gingival, labial and lingual. 
 
 The angles of a surface of a tooth are named by com- 
 bining the names of the margins joining to form the angle. 
 Thus, the buccal surface of a molar has four angles, the mesio- 
 occlusal, disto-occlusal, mesio-gingival and disto-gingi- 
 val angles. All angles of the surfaces of the teeth are named 
 on this plan. The mesial and distal surfaces of the incisors and 
 cuspids having but three margins have but three angles: the 
 labio-gingival, linguo-gingival, and incisal angles.* (The 
 name incisal angle is an exception to the general rule for 
 naming angles of surfaces.) 
 
 8. A cusp is a pronounced elevation, more or less pointed 
 on the surface of a tooth, but more especially on the occlusal 
 surface. A slight elevation is often called a tubercle, as that 
 frequently seen near the gum on the lingual surface of the 
 upper incisors. These are generally deviations from the typi- 
 cal forms of the teeth. 
 
 9. Long-shaped elevations on the surfaces of teeth are 
 called ridges, and are named according to their location or 
 form; as buccal ridge, lingual ridge, and marginal ridge. The 
 marginal ridges are those elevations of the enamel which form 
 the margins of the occlusal surfaces of the bicuspids and mo- 
 lars, and the mesial and distal margins of the lingual surfaces of 
 the incisors and cuspids. Those ridges which descend from 
 the cusps of the molars and bicuspids toward the central part of 
 the occlusal surfaces are called triangular ridges. They are 
 so-called because the typical form of the ridges is usually that 
 
 * The student should note carefully the difiference between the 
 names of the angles of a tooth and the angles of a surface of a tooth. 
 To illustrate : The mesio-bucco-occlusal angle of a tooth is in effect 
 the bucco-occlusal angle of its mesial surface, the mesio-buccal angle 
 of its occlusal surface, or the mesio-occlusal angle of its buccal sur- 
 face. In this work the descriptions are mostly of individual surfaces, 
 hence the names of the angles of surfaces are much oftener used than 
 the names of the angles of the teeth. 
 
NOMENCLATURE. 
 
 The following tables of the angles of teeth and the angles of 
 surfaces of teeth, will assist the student in obtaining a clear under- 
 standing of them if studied in connection with the text and the illus- 
 trations.* 
 
 Angles of teeth < 
 
 Line angles 
 
 {Mesio-labial 
 Disto-labial 
 Mesio-lingual 
 Disto-lingual 
 
 Mesio-buccal 
 Disto-buccal 
 Mesio-lingual 
 Disto-lingual 
 
 Point angles 
 
 Bicuspids 
 ^ and molars 
 
 Incisors 
 and cuspids 
 
 Bicuspids 
 and molars 
 
 Mesio-occlusal 
 Disto-occlusal 
 Bucco-occlusal 
 Linguo-occlusal 
 
 Mesio-incisal 
 Disto-incisal 
 
 Mesio-bucco-occlusal 
 Disto-bucco-occlusal 
 Alesio-linguo-occlusal 
 Disto-linguo-occlusal 
 
 Angles of 
 the surfaces 
 of teeth 
 
 Incisors 
 and cuspids 
 
 Labial and lingual 
 surface angles 
 
 Mesial and distal 
 surface angles 
 
 Bicuspids 
 and molars 
 
 Mesio-incisal 
 Disto-incisal 
 Mesio-gingival 
 Disto-gingival 
 
 Labio-gingival 
 
 Linguo-gingival 
 
 Incisal 
 
 {Alesio-occlusal 
 Disto-occlusal 
 Mesio-gingival 
 Disto-gingival 
 
 r Mesio-buccal 
 J Disto-buccal 
 
 Occlusal 
 surface angles 
 
 I Mesio-lingual 
 I Disto-lingual 
 
 f Bucco-occlusal 
 Mesial and distal J Bucco-gingival 
 surface angles ] Lmguo-occlusal 
 L Linguo-gingival 
 
 * Suggested by Dr. Wm. E. Harper. 
 
Note. — In the naming of the surfaces and angles of the teeth the crowns are 
 regarded as representing cubes with the angles more or less rounded, though they 
 are named as if they were true cubes. For this reason the diagrams here given for 
 the explanation of these names are drawn as cubes. 
 
 Diagram A ("Parg \ find 5)- — The Surfaces of a Lower Molar, m, Mesial 
 surface; /, lingual surface; b, buccal surface; d, distal surface; 0, occlusal surface; 
 g, gingival line. This line passes entirely around the tooth at the junction of the 
 crown with the root. 
 
 Diagram B (Patv-7).— The Names and Positions of the Line Angles of a 
 Mola?. mb, Mesio-buccal angle; ml, mesio-lingual angle; db, disto-buccal angle; dl, 
 disto-lingual angle; mo, mesio-occlusal angle; do, disto-occlusal angle; bo, bucco- 
 occlusal angle; lo, linguo-occlusal angle. The names of the occlusal line angles 
 (the last four) are seldom used, as they are called also marginal ridges. 
 
 Diagram C (Eax.-?). — The Names and Positions of the Point Angles of 
 THE Teeth. It will be noticed that these angles are formed by the junction of three 
 surfaces forming' a corner or point, and that the names of three surfaces form the 
 name of the angle, mbo, mesio-buccal-occlusal angle; mlo, mesio-linguo-occlusal 
 angle; dbo, disto-bucco-occlusal angle; dio, disto-linguo-occlusal angle; mbg, mesio- 
 bucco-gingival angle; mig, mesio-linguo-gingival angle; dbg, disto-bucco-gingivnl 
 angle; dig, disto-linguo-gingival angle. 
 
NOMENCLATURE. 1 1 
 
 of a triangle. They are named after the cusps to which they 
 belong, as the triangular ridge of the mesio-buccal cusp of the 
 upper first molar, or simply, mesio-buccal triangular rid^. 
 When a buccal and a lingual triangular ridge join they form a 
 transverse ridge. In this way they often subdivide the cen- 
 tral fossa of the lower molars and form supplemental fossae. 
 
 10. A generally rounded or angular depression on the 
 surface of a tooth is called a fossa. Fossae occur mostly on the 
 occlusal surfaces of the molars. When a notable depression is 
 long-shaped it is called a sulcus. Some of these pass mesio- 
 distally entirely through the occlusal surface of a tooth, as in 
 the bicuspids. This term is often erroneously applied to the 
 grooves and fissures. 
 
 11. A shallow, long-shaped depression, in the form of a 
 line, on the surface of a tooth, is called a groove. When such / 
 a groove follows the bottom of a sulcus it is said to be sulcate. j 
 When such a groove sinks suddenly into the substance of a 
 tooth in the form of a fault it is called a fissure. The words 
 sulcus, groove, and fissure are often used as if they were syn- 
 onymous and interchangeable, which has given rise to much 
 confusion. It is necessary that the distinctions made in their use 
 in dental anatomy be well understood. A groove is a very fine 
 line in the form of a slight, sharp depression on the surface of 
 the tooth, (as represented in section in Diagram D, at a in a 
 section cut at the point where the mesial groove passes over the 
 marginal ridge of a bicuspid. Diagram E, from a cross section 
 of a bicuspid, very close to the occlusal surface grooves are 
 shown at a, a. j A very shallow depression with rounded bot- 
 tom is also called a groove, as those seen on the labial surfaces 
 of the incisors. A sulcate groove is one that follows a sulcus of 
 notable depth, the inclines of which approach each other at an 
 angle 'as represented in Diagram F, a, pointing out the groove, 
 and c, the inclines of the surface of the tooth which form the 
 aulc-us. A fissure is always a fault in the enamel, a point where 
 the margins of the plates of enamel fail to unite, as represented 
 at a, in Diagram G. These are distinctions of importance, and 
 
12 
 
 NOMENCLATURE. 
 
 there should be no confusion in the use of the words by which 
 we distinguish them. There are two varieties of grooves in the 
 teeth, differing essentially in their nature and formation. One 
 class mark the lines on which the parts of the enamel first 
 formed separately, are afterward joined, and are called the es- 
 sential or developmental grooves, or developmental lines. 
 
 D 
 
 In their relation to the development of the enamel, they are of 
 the same nature and resemble the sutures of the bones of the 
 skull, which mark the junction of the separately formed plates. 
 The parts, or divisions, of a tooth outlined by its developmental 
 grooves are called its lobes. Most human teeth have four 
 lobes ; but some have five and some only three. Hence, these 
 
NOMENCLATURE. I3 
 
 grooves form the key to much of descriptive dental anatomy ; 
 and when they can be traced, enable the anatomist to unravel 
 complex forms, and assign irregularly-formed teeth to the 
 groups to which they belong, to properly name their individual 
 parts, and identify any additional, accidental, or unusual forms 
 of parts that may have become intermingled in the accident of a 
 faulty formation. These developmental grooves, or lines, are 
 subject to fissures, which occur when, from any cause, there is 
 a failure of perfect union of the parts, leaving a fault. 
 
 12. The other class of grooves have no especial relation 
 to the developmental lines, and are called supplemental 
 grooves. These are aptly described as wrinkles in the enamel, 
 which, in fact, many of them are. But some are so constant in 
 their location and' form as to make up a portion of the typical 
 tooth-form. The supplemental grooves are usually shallow, with 
 well-rounded bottoms, and are not ordinarily subject to fissure. 
 
 13. In the mesio-distal direction all of the teeth are a 
 little broader at or near their occlusal surfaces than at their 
 necks; therefore, as they stand in the well- formed arch, their 
 proximate surfaces touch only at or near the occlusal margins 
 of their proximate surfaces, leaving V-shaped openings be- 
 tween their necks. These are called inter-proximate spaces. 
 Normally, the inter-proximate spaces are filled with gum tissue. 
 
 __ In the bucco-lingual direction the proximate surfaces 
 of the teeth are also more or less rounded, so that the proximate 
 contact is narrowed to a point leaving a space widening toward 
 the buccal and a space widening toward the lingual. These are 
 called the buccal and lingual inter-proximate embrasures. 
 
 14. The teeth of different individuals show considerable 
 variety of form. Some persons have teeth with very long 
 crowns, broad in the mesio-distal direction at their occlusal sur- 
 faces and narrow at their necks. These present large inter- 
 proximate spaces. They are known as bell-crowned teeth. 
 Again, some individuals have teeth that, in their mesio-distal 
 diameter, are nearlv as thick at their necks as at the occlusal 
 
14 MEASUREMENTS OF THE TEETH. 
 
 surfaces, making their inter-proximate spaces very narrow, the 
 teeth almost, or quite, touching along the whole length of the 
 crown. These are known as thick-necked teeth. The more 
 common form is midway between these two extremes. The 
 teeth of some individuals and families have very long cusps ; 
 those of others have very short cusps. Some are deeply marked 
 by grooves and sulci, and in those of others the grooves and 
 sulci are shallow. Thus, there is considerable variety of con- 
 tour without change of type. 
 
 MEASUREMENTS OF THE TEETH. 
 
 15. In the following tables the results of the measure- 
 ment of many teeth of each denomination are given. The num- 
 bers measured of the different varieties differed, but in all de- 
 nominations they were sufficient to insure reasonable accuracy 
 as to the average size. There are three measurements given, 
 the average, greatest, and least, in the several positions meas- 
 ured. With a greater number, both larger and smaller teeth 
 might be found, so that the tables must not be taken to represent 
 the greatest nor the least that might be obtained ; but the occur- 
 rence of larger, or longer teeth must be rare. 
 
 The lines of measurement are : 
 
 ist. "Length over all:" Length of the tooth from the 
 cutting edge, or buccal cusp, to the apex of the root. 
 
 2d. "Length of crown :" Length of the crown from the 
 cutting edge, or buccal cusp, to the gingival line on the labial 
 or buccal surface. 
 
 3d. "Length of root :" Length of root from the gingival 
 line on the buccal surface to the apex of the root. 
 
 4th. "Mesio-distal diameter of crown:" This is the ex- 
 tent from mesial to distal in the greatest diameter, or at the 
 points of proximate contact. 
 
 5th. "Mesio-distal diameter of neck:" This measurement 
 was made at the gingival line. 
 
'" MEASUREMENTS OF THE TEETH. I5 
 
 6th. "Labio- or bucco-lingual diameter:" This measure- 
 ment was taken at the greatest diameter of the crown in the 
 direction named. In the incisors it was on the gingival ridge. 
 In the bicuspids and molars it was generally mid-length of the 
 crown, but occasionally it was near the gingival line, especially 
 in the upper second and third molars. 
 
 7th. "Curvature of the gingival line :" This is the height 
 or extent of the curve of the gingival line toward the cutting 
 edge, or occlusal surface, as it passes from labial to lingual, 
 measured on the mesial surface. 
 
 Having these tables, the necessity for giving many meas- 
 urements in the text is avoided. 
 
i6 
 
 MEASUREMENTS OF THE TEETH. 
 
 UPPER TEETH. 
 
 Tablk of Measurements of the 
 Teeth of Man, Given in Mil- 
 limeters AND Tenths of Milli- 
 meters.* 
 
 "3 
 
 u 
 <u 
 
 c 
 
 V 
 
 
 
 w 
 
 
 
 
 "So 
 
 c 
 
 V 
 
 
 
 
 
 u 
 
 "0 
 
 V 
 
 « 2 
 
 ••So 
 .2 S 
 
 V V 
 
 "5 
 
 
 3 c 
 1 
 .2 S 
 
 •5 
 
 Si 
 
 -a 
 
 .2 1 
 •2 " 
 
 11 
 
 1— C 
 
 -^ 
 a — 
 
 3 _> 
 
 > C 
 
 UPPER TEETH. 
 
 
 
 ^ 1 Average. 
 Central Greatest. 
 I^"^"-^- Least. 
 
 22.5 
 27.0 
 18.0 
 
 lO.O 
 
 12.0 
 
 8.0 
 
 12.0 
 
 16.0 
 
 8.0 
 
 9.0 
 
 lO.O 
 
 8.0 
 
 6.3 
 
 7.0 
 
 5-5 
 
 7.0 
 8.0 
 7.0 
 
 3.0 
 4.0 
 
 2.0 
 
 Lateral GveltSt. 
 I'^^'^^'^- Least. 
 
 22.0 
 26.0 
 17.0 
 
 8.8 
 
 10.5 
 
 8.0 
 
 13.0 
 
 16.0 
 
 8.0 
 
 6.4 
 7.0 
 
 5-0 
 
 4.4 
 4.0 
 
 6.0 
 7.0 
 5-0 
 
 2.8 
 
 4.0 
 2.0 
 
 Average. 
 Cuspid. Greatest. 
 Least. 
 
 26.S 
 32.0 
 20.0 
 
 9-5 
 
 12.0 
 
 8.0 
 
 17-3 
 20.5 
 
 II.O 
 
 7.6 
 9.0 
 7.0 
 
 5-2 
 
 6.0 
 4.0 
 
 8.0 
 9.0 
 7.0 
 
 2.5 
 
 3-5 
 
 I.O 
 
 T-. , Average. 
 Fi«t Greatest. 
 Bicuspid. Least. 
 
 20.6 
 22.5 
 17.0 
 
 8.2 
 9.0 
 7.0 
 
 12.4 
 14.0 
 
 lO.O 
 
 7.2 
 8.0 
 7.0 
 
 4-9 
 6.0 
 4.0 
 
 9-1 
 
 lO.O 
 
 8.0 
 
 I.I 
 2.0 
 0.0 
 
 S"°°^ GrelSt 
 Bicuspid. Least. 
 
 21.5 
 27.0 
 16.0 
 
 7-5 
 9.0 
 7.0 
 
 14.0 
 19.0 
 
 lO.O 
 
 6.8 
 8.0 
 6.0 
 
 10.7 
 
 12.0 
 
 9.0 
 
 5-3 
 6.5 
 
 4-5 
 
 8.8 
 
 lO.O 
 
 7-5 
 
 0.8 
 
 1-5 
 0.0 
 
 Gr^e?: 
 M^l^'^- Least. 
 
 20.8 
 24.0 
 17.0 
 
 7-7 
 9.0 
 7.0 
 
 13.2 
 
 16.0 
 10. 
 
 7-5 
 8.0 
 7.0 
 
 II. 8 
 12.0 
 
 II.O 
 
 2.2 
 3-0 
 1.0 
 
 S«°°d , Gr7at?st 
 M°^"- Least. 
 
 20.0 
 24.0 
 
 i6.o 
 
 7.2 
 8.0 
 6.0 
 
 13.0 
 
 17.0 
 
 9.0 
 
 9.2 
 
 lO.O 
 
 7.0 
 
 6.7 
 8.0 
 6.0 
 
 11.5 
 12.5 
 
 lO.O 
 
 1.6 
 4.0 
 0.0 
 
 „, . , Average. 
 ^^''i, , Greatest. 
 ^°^^^- Least. 
 
 17.1 
 22.0 
 14.0 
 
 6.3 
 8.0 
 
 5-0 
 
 II. 4 
 15.0 
 8.0 
 
 8.6 
 
 II.O 
 
 7.0 
 
 6.1 
 8.0 
 5-0 
 
 10.6 
 
 14.5 
 8.0 
 
 0.7 
 
 2.5 
 0.0 
 
 ■ There are 25.4 millimeters to the inch. 
 
MEASUREMENTS OF THE TEETH. 
 
 17 
 
 LOWER TEETH. 
 
 Table of Measurements of the 
 Teeth of Man, Given in Mil- 
 limeters AND Tenths of Milli- 
 meters. 
 
 
 
 u 
 
 
 J3 
 B 
 
 
 
 
 u 
 
 
 M 
 
 B 
 V 
 
 tn 
 
 ^ 
 
 "3 
 
 1) 
 
 CJ 4-1 
 
 U 1> 
 
 3 S 
 
 ■« 
 
 V 
 
 •S oJ 
 (_ B 
 S 
 lU » 
 
 s .> 
 
 as '5) 
 
 °" 
 
 LOWER TEETH. 
 
 
 C^°\'^k cleaSst 
 I'^"^^^- Least. 
 
 20.7 
 24.0 
 16.0 
 
 8.8 
 
 10.5 
 
 7.0 
 
 II.8 
 
 16.0 
 
 9.0 
 
 5-4 
 6.0 
 5.0 
 
 3-5 
 5.0 
 
 2.5 
 
 6.0 
 
 6.5 
 
 5-5 
 
 2.5 
 3-0 
 1-5 
 
 1 ateral Average. 
 Lateral. Greatest. 
 
 1°"^°^- Least. 
 
 21. 1 
 
 27.0 
 18.0 
 
 9.6 
 
 12.0 
 
 7.0 
 
 12.7 
 17.0 
 II. 
 
 5-9 
 6.5 
 5° 
 
 3.8 
 3-0 
 
 6.4 
 
 7-5 
 6.0 
 
 2.5 
 3-5 
 2.0 
 
 Average. 
 Cuspid. Greatest. 
 Least. 
 
 25.6 
 
 32.5 
 20.0 
 
 10.3 
 
 12.0 
 
 8.0 
 
 15-3 
 21.0 
 II. 
 
 6.9 
 9.0 
 5.0 
 
 5-2 
 
 7.0 
 3-0 
 
 7-9 
 
 10. 
 
 6.0 
 
 2.9 
 4.0 
 2.0 
 
 F"^^^. ■ . , Grelte^t' 
 Bicuspid. Least. 
 
 21.6 
 
 26.0 
 18.0 
 
 7.8 
 9.0 
 6.5 
 
 14.0 
 18.0 
 II. 
 
 6.9 
 8.0 
 6.0 
 
 4.7 
 4.5 
 
 7-7 
 8.0 
 7.0 
 
 0.8 
 1-5 
 0.5 
 
 J Average. 
 S«^°?^«i ., Greatest. 
 Bicuspid. Least. 
 
 22.3 
 
 26.0 
 18.0 
 
 7-9 
 
 lo.o 
 
 6.0 
 
 14.4 
 17-5 
 II-5 
 
 7-1 
 
 8.0 
 6.5 
 
 4.8 
 
 6.5 
 4.0 
 
 8.0 
 9.0 
 7.0 
 
 0.6 
 2.0 
 0.0 
 
 _. ^ Average. 
 ^''% , Greatest. 
 ^°^^'- Least. 
 
 21.0 
 
 24.0 
 
 18.0 
 
 7-7 
 
 10. 
 
 7.0 
 
 13.2 
 15.0 
 II. 
 
 II. 2 
 
 12.0 
 II. 
 
 8.5 
 9-5 
 7-5 
 
 10.3 
 "•5 
 
 lO.O 
 
 I.I 
 
 2.0 
 0.0 
 
 c, , Average. 
 S^'^^^f , Greatest. 
 ^^°^^'- Least. 
 
 19.8 
 22.0 
 18.0 
 
 6.9 
 8.0 
 6.0 
 
 12.9 
 14.0 
 12.0 
 
 10.7 
 II. 
 
 lO.O 
 
 8.1 
 
 8.5 
 8.0 
 
 10. 1 
 
 10.5 
 
 9-5 
 
 0.2 
 
 I.O 
 
 0.0 
 
 ^rist. 
 ^°1"- Least. 
 
 18.5 
 
 20.0 
 16.0 
 
 6.7 
 8.0 
 6.0 
 
 11.8 
 
 17.0 
 
 8.0 
 
 10.7 
 
 12.0 
 
 8.0 
 
 8.3 
 9.5 
 
 5.0 
 
 9.8 
 
 10.5 
 
 9.0 
 
 0.2 
 
 1-5 
 0.0 
 
MEASUREMENTS OF THE TEETH. 
 
 UPPER AND LOWER TEETH. 
 
 Table of Measurements of the 
 Deciduous Teeth of Man, 
 Given in Millimeters and 
 Tenths of Millimeters. 
 
 > 
 
 
 Si 
 
 bi 
 
 n 
 
 
 
 u 
 
 
 
 M 
 
 c 
 
 D 
 ►J 
 
 
 £ 
 
 V 
 
 
 
 "^ ^ 
 
 TO tj 
 
 to -^ 
 
 ^ ° 
 
 6 S 
 
 || 
 
 -5 
 
 1 S 
 ^ "0 
 i s 
 
 S 2 
 
 .5 
 4; 
 
 « s 
 
 ►J rt 
 
 ■5 
 
 .— 
 01 v 
 a c 
 btu. 
 
 .B 
 
 T u 
 
 (U 
 
 IS ■£ 
 
 Averages Only. 
 
 •5 
 
 UPPER TEETH. 
 
 
 Central Incisor. 
 
 16.0 
 
 6.0 
 
 10. 
 
 6.5 
 
 4-5 
 
 5-0 
 
 4.0 
 
 Lateral Incisor. 
 
 15.8 
 
 5-6 
 
 II.4 
 
 51 
 
 3-7 
 
 4.8 
 
 3-7 
 
 Cuspid. 
 
 19.0 
 
 6.5 
 
 13-5 
 
 7.0 
 
 5-1 
 
 7.0 
 
 5-5 
 
 First Molar. 
 
 15-2 
 
 5.1 
 
 10.0 
 
 7-3 
 
 5-2 
 
 8.5 
 
 6.9 
 
 Second Molar. 
 
 17-5 
 
 5-7 
 
 II. 7 
 
 8.2 
 
 6.4 
 
 lO.O 
 
 8.3 
 
 LOWER TEETH. 
 
 
 
 
 
 
 
 
 Central Incisor. 
 
 14.0 
 
 S.o 
 
 9.0 
 
 4.2 
 
 3-0 
 
 4.0 
 
 3-5 
 
 Lateral Incisor. 15.0 
 
 5-2 
 
 lO.O 
 
 4.1 
 
 3-0 
 
 4.0 
 
 3-5 
 
 Cuspid. 17.0 
 
 6.0 
 
 1 
 
 "•5 
 
 50 
 
 3-7 
 
 4.8 
 
 4.0 
 
 First Molar. 
 
 15.8 
 
 6.0 
 
 9.8 
 
 7-7 
 
 6.5 
 
 7.0 
 
 5-3 
 
 Second Molar. 
 
 18.8 
 
 5-5 
 
 11.3 9.9 
 
 7-2 
 
 8.7 
 
 6.4 
 
MEASUREMENTS OF THE TEETH. 
 
 IQ 
 
 UPPER TEETH. 
 
 Table of Measurements of the 
 Teeth of Man, in Inches and 
 Hundredths of an Inch. 
 
 u 
 
 V 
 
 > 
 
 O 
 
 
 
 '0 
 
 oi 
 
 c 
 
 V 
 
 ►J 
 
 
 
 
 
 
 J3 
 M 
 
 C 
 D 
 
 J 
 
 ■3 2 
 
 V 
 1-. 
 
 CJ 1) 
 
 S 
 •5 
 
 1 ^ 
 1 
 
 .2 ^ 
 S E 
 
 ■5 
 
 si 
 
 6 g 
 ■2 *« 
 
 1* . 
 
 ■" a 
 '•^ 
 u •-; 
 3 > 
 
 UPPER TEETH. 
 
 U 
 
 Central. ^^S 
 I""^^'-- Least. 
 
 .88 
 i.o6 
 
 .72 
 
 •39 
 .41 
 •31 
 
 •49 
 •63 
 •31 
 
 •35 
 •39 
 •31 
 
 .24 
 
 •27 
 .21 
 
 •27 
 .31 
 •27 
 
 .11 
 
 •15 
 .07 
 
 Lateral Greatlt. 
 1°"^°'^- Least. 
 
 .86 
 
 1.02 
 
 .66 
 
 •34 
 .41 
 
 •31 
 
 •51 
 •63 
 ■31 
 
 •25 
 •27 
 .19 
 
 •17 
 ■ 19 
 •15 
 
 •23 
 •23 
 •19 
 
 .11 
 
 •15 
 
 .07 
 
 Average. 
 Cuspid. Greatest. 
 Least. 
 
 1.04 
 
 1.26 
 
 •79 
 
 •37 
 •47 
 •31 
 
 .68 
 .80 
 •43 
 
 .29 
 ■35 
 •27 
 
 .20 
 •23 
 •15 
 
 •31 
 
 •35 
 •27 
 
 .09 
 •13 
 •03 
 
 T7- ^ Average. 
 
 ^''%. ., Greatest. 
 
 Bicuspid. Least. 
 
 .81 
 .89 
 .66 
 
 •32 
 •35 
 
 .27 
 
 .48 
 •55 
 •39 
 
 .28 
 
 •31 
 
 .27 
 
 .19 
 •23 
 
 •15 
 
 •35 
 •39 
 •31 
 
 .04 
 .07 
 .00 
 
 ,, , Average. 
 ^«^°^^ ., Greatest. 
 Bicuspid. Least. 
 
 .84 
 
 1.06 
 
 .62 
 
 •29 
 .29 
 
 •27 
 
 .55 
 •55 
 •39 
 
 .26 
 •31 
 •23 
 
 .20 
 •25 
 .17 
 
 •34 
 •39 
 • 29 
 
 •03 
 •05 
 .00 
 
 First Average. 
 
 .81 
 
 •94 
 .66 
 
 •30 
 •35 
 •27 
 
 •51 
 
 .62 
 
 •39 
 
 .42 
 •47 
 •35 
 
 .29 
 •31 
 •27 
 
 .46 
 •47 
 •43 
 
 .08 
 .11 
 •03 
 
 Second ^^^-^fSt 
 Molar. f'-^^^^t- 
 Least. 
 
 .78 
 
 •94 
 .62 
 
 .28 
 •31 
 •23 
 
 •51 
 .66 
 
 •35 
 
 .36 
 •39 
 
 •27 
 
 .26 
 •31 
 •23 
 
 •45 
 •49 
 •39 
 
 ■05 
 •15 
 
 .00 
 
 Third ^^^'"fgt 
 Molar. Greaest. 
 Least. 
 
 .67 
 .86 
 
 .55 
 
 •24 
 •31 
 •19 
 
 •44 
 •59 
 •31 
 
 •33 
 
 •43 
 .27 
 
 •23 
 •31 
 •19 
 
 .41 
 •57 
 •31 
 
 .02 
 .09 
 .00 
 
20 
 
 MEASUREMENTS OF THE TEETH. 
 
 LOWER TEETH. 
 
 Table of Measurements of the 
 Teeth of Man, in Inches and 
 Hundredths of an Inch. 
 
 u 
 
 V 
 
 o 
 
 c 
 
 4) 
 
 
 
 u 
 
 "o 
 "S) 
 
 c 
 
 4> 
 
 
 
 
 
 5 
 
 ►J 
 
 c 
 5 2 
 
 in 
 
 n 
 
 in 1) 
 
 s 
 
 •5 
 
 — u 
 cd V 
 
 ■5 
 
 •2 i 
 
 S 4! 
 
 8 5 
 
 3-5 
 
 
 
 ■5 « 
 — 
 
 4> ^^ 
 
 u rt 
 3 > 
 
 rt 'So 
 > c 
 
 3 'So 
 
 LOWER TEETH. 
 
 U 
 
 ^°"^°'^- Least. 
 
 .80 
 .63 
 
 •34 
 .41 
 .27 
 
 •47 
 .62 
 
 •35 
 
 .22 
 .23 
 •19 
 
 •13 
 .19 
 .09 
 
 •23 
 .26 
 
 .21 
 
 .09 
 .11 
 
 •05 
 
 L^t^^l . GreatTt! 
 1°"^°^- Least. 
 
 .83 
 
 1.06 
 
 .70 
 
 •35 
 .46 
 .27 
 
 .50 
 .66 
 •43 
 
 •23 
 .26 
 
 • 19 
 
 •15 
 .19 
 .11 
 
 •25 
 •29 
 •25 
 
 .09 
 
 •13 
 
 .08 
 
 Average. 
 Cuspid. Greatest. 
 Least. 
 
 1. 01 
 1.28 
 
 .78 
 
 .40 
 .46 
 •32 
 
 .60 
 .82 
 •43 
 
 .27 
 •35 
 •23 
 
 .20 
 
 ■27 
 .11 
 
 •31 
 
 •39 
 
 .24 
 
 .11 
 .14 
 
 .08 
 
 First Average. 
 
 Bicuspid. £:r'- 
 
 .84 
 1.02 
 
 .30 
 • 35 
 •25 
 
 • 54 
 .70 
 
 .43 
 
 .27 
 •32 
 •23 
 
 .18 
 .20 
 .16 
 
 •30 
 •31 
 
 .27 
 
 •03 
 •05 
 .01 
 
 Second Average. 
 T>- -J Greatest. 
 Bicuspid. Least. 
 
 .87 
 1,02 
 
 •7» 
 
 •31 
 
 •43 
 •23 
 
 .56 
 •63 
 • 45 
 
 .28 
 .32 
 •25 
 
 .18 
 •25 
 •15 
 
 •31 
 
 •35 
 
 •27 
 
 .02 
 .07 
 .00 
 
 First ^^^"g^- 
 Molar. Greaest. 
 Least. 
 
 .78 
 •94 
 •71 
 
 •30 
 •39 
 •27 
 
 •52 
 •59 
 .43 
 
 •33 
 •37 
 .23 
 
 •33 
 •37 
 •29 
 
 .40 
 •45 
 •39 
 
 .04 
 .07 
 .00 
 
 Second i^^"f^^- 
 Molar. ^-■ 
 
 .78 
 .86 
 •71 
 
 •27 
 •31 
 •23 
 
 •50 
 •55 
 •47 
 
 •42 
 •43 
 •39 
 
 •32 
 .33 
 •31 
 
 •39 
 .41 
 •37 
 
 .00 
 .00 
 .00 
 
 Third Average. 
 .r , Greatest. 
 Molar. T 
 
 Least. 
 
 •72 
 .78 
 
 •63 
 
 .26 
 •32 
 ■23 
 
 •36 
 .66 
 
 •31 
 
 •42 
 •47 
 •31 
 
 •32 
 •37 
 .20 
 
 •38 
 
 .41 
 
 •35 
 
 .00 
 .04 
 .00 
 
MEASUREMENTS OF THE TEETH. 
 
 21 
 
 UPPER AND LOWER TEETH. 
 
 Table of Measurements of the 
 Deciduous Teeth of Man, Given 
 IN Inches and Hundredths of an 
 Inch. 
 
 > 
 o 
 .a 
 
 M 
 V 
 
 J 
 
 
 u 
 
 
 .a 
 "m 
 
 V 
 
 J 
 
 1 
 . 
 
 c 
 
 i 
 
 « g 
 
 ^ 
 
 u 
 'm ^^ 
 
 ■5 
 
 2. % 
 -■B 
 .2 fe 
 
 .2 
 •5 
 
 .E ° 
 
 s 
 
 •5 
 
 -lingual 
 r of neck. 
 
 Averases Only- 
 
 
 UPPER TEETH. 
 
 
 Central Incisor. 
 
 •63 
 
 1 
 
 •23 .39 1 -25 -18 
 
 .20 
 
 .16 
 
 Lateral Incisor. 
 
 .62 
 
 •25 
 
 •45 ; -20 ^ .14 
 
 •19 
 
 .14 
 
 Cuspid. 
 
 •74 
 
 •25 
 
 •53 -27 1 -20 
 
 •27 
 
 .21 
 
 First Molar. 
 
 •59 
 
 .20 
 
 •39 
 
 .28 
 
 .20 .33 
 
 •27 
 
 Second Molar. 
 
 .68 
 
 .22 
 
 •46 
 
 .32 
 
 •25 -39 
 
 •32 
 
 LOWER TEETH. 
 
 
 
 
 
 
 
 
 Central Incisor. 
 
 •55 
 
 •19 
 
 1 
 
 • 35 1 -15 
 
 1 
 
 .11 
 
 •15 
 
 •13 
 
 Lateral Incisor. 
 
 •59 
 
 .19 .39 -IS 
 
 1 1 
 
 •" j -15 
 
 1 
 
 ■13 
 
 Cuspid. 
 
 .66 
 
 •23 45 
 
 i 
 
 •19 
 
 .14 
 
 •17 
 
 •15 
 
 First Molar. 
 
 .62 
 
 24 .38 
 
 •30 
 
 •25 
 
 .27 
 
 .21 
 
 Second Molar. 
 
 .62 
 
 .21 .44 .38 
 
 i i 
 
 .28 
 
 •34 
 
 •25 
 
UPPER CENTRAL INCISORS. 
 
 UPPER CENTRAL INCISORS. 
 
 Note. — Usually, in the descriptions of the teeth, those of one side 
 only will be mentioned, without reference to which side in the text. 
 Accompanying the illustrations, the side to which the tooth belongs 
 will be given. The student will readily determine to which side a 
 given example belongs by comparing it with the text and correctly 
 naming its surfaces. Students should remember that the cuts are 
 representations of individual teeth, while the text describes the aver- 
 age forms, therefore the cuts will not always exactly correspond with 
 the text. 
 
 1 6. The right and left upper central incisors are situated 
 in the extreme anterior part of the dental arch, one on each 
 side of the median line, their mesial surfaces proximating each 
 other. The cro"wn presents four surfaces, four angles, and a 
 cutting edge, or incisal surface. The general contour of the 
 crown is similar to a wedge, with rounded angles, and merging 
 into a rounded form at the thick end, or the neck of the tooth. 
 It is slightly bent on its shorter diameter, so as to make the 
 flattened labial surface convex; while the other, the lingual, is 
 concave. The crown is also slightly bent in the mesio-distai 
 direction, so that the labial surface is convex and the lingual 
 concave in this direction. Therefore, there is a general con- 
 vexity of the labial", and a general concavity of the lingual sur- 
 face. 
 
 17. The labial surface of the crown of the upper central 
 incisor (Fig. i), in its general form, is an imperfect square, 
 with its gingival side rounded. The mesial margin is a little 
 longer than the distal, so that the cutting edge slopes away 
 toward the disto-incisal angle (Fig. i, h). Both the angles, 
 formed by the proximate surfaces and cutting edge, are slightly 
 rounded, the disto-incisal more than the mesio-incisal, after 
 which the proximate surfaces converge toward the long axis of 
 the tooth, making the crown a little narrower at the neck than 
 at the cutting edge. 
 
 18. The lingual surface of the crown (Fig. 2) is con- 
 cave in all directions, forming a fossa, bounded by the cutting 
 edge (a), the mesial and distal marginal ridges (n, m), and the 
 
Fie. 4. 
 
 Fig. 5. 
 
 Fig. I* (Par. 17). — Right Upper Central Incisor, Labial Surface, a, Cut- 
 ting edge; b, mesial surface; c, distal surface; d, labial surface; e, e, labial grooves; 
 g, mesio-incisal angle; /;, disto-incisal angle; i, body of root; k, apex of root. 
 
 Fig. 2* (Par. 18). — Right Upper Central Incisor, Lingual Surface, a. Cut- 
 ting edge; b, mesial surface; c, distal surface; d, linguo-gingival ridge, or cingu- 
 lum; /, gingival line; g, mesio-incisal angle; /;, disto-incisal angle; i, body of root; 
 k, apex of root; m, distal marginal ridge; n, mesial marginal ridge. 
 
 Fig. 3* (Par. 18). — Left Upper Central Incisor, Lingual Surface, showing 
 lingual pit. The cutting edge, a, is considerably worn. The mesial and distal mar- 
 ginal ridges, b, c, are prominent; d, linguo-gingival ridge; f, gingival line; ff, 
 mesio-incisal angle; /;, disto-incisal angle; j, body of root; k, apex of root; m, 
 lingual pit. 
 
 Fig. 4* (Par. 19). — Right Upper Central Incisor, Mesial Surface, a. Mesio- 
 incisal angle; d, linguo-gingival ridge; f, f, gingival line, showing its labio-lingual 
 curvature; i, body of root; k, apex of root. 
 
 Fig. s* (Par. 21). — Left Upper Central Incisor, Lingual Surface. Young, 
 unworn tooth. The developmental lines, or grooves, are made diagrammatically 
 prominent to show the form of the lobes, a, Middle lobe; b, mesial lobe; c, distal 
 lobe; d, lingual lobe; e, e, linguo-gingival groove; /, f, lingual developmental 
 grooves; g, mesio-incisal angle; h, disto-incisal angle. 
 
 'Illustration, lyi diameters. 
 
UPPER CENTRAL INCISORS. 
 
 linguo-gingival ridge, or cingulum (d). The marginal ridges 
 are strong elevations of the enamel, running from the mesio- 
 incisal and disto-incisal angles along the borders of this sur- 
 face to near the gingival line, where they join the linguo-gingi- 
 val ridge. The linguo-gingival ridge is a strong elevation of 
 the enamel forming the linguo-gingival border of the crown. 
 It is sometimes elevated into a tubercle. The lingual fossa is 
 usually smooth, and the ridges by which it is bounded are not 
 prominent. In many instances, however, there is a deep pit at 
 the junction of the linguo-gingival ridge with the lingual sur- 
 face proper; and in some a groove extends from the pit for a 
 short distance along the border of each marginal ridge (Fig. 
 3). These latter may, or may not, be fissured. In a few ex- 
 amples the enamel of this surface has irregular wrinkles, or 
 ridges and grooves, running from the linguo-gingival ridge 
 toward the cutting edge. In malformed teeth this surface is 
 often very imperfect. 
 
 19. The mesial and distal surfaces each present the 
 outline of the letter V, with its lines curved with the convexity 
 toward the lips, and the acute angle at the cutting edge (Fig. 
 4). The mesial surface is almost straight from the mesio- 
 incisal angle to the gingival line. It Is convex from labial to 
 lingual, but nearly flat toward the gingival line ; while in some 
 there is even a slight concavity, centrally at, or near, the gingi- 
 val line. In the labio-lingual direction, the distal surface is 
 rounded, as in the mesial. In the majority of examples it is 
 also convex in the direction of the long axis of the tooth, so 
 that it bellies out toward the lateral incisor. 
 
 20. At the gingival line, the tooth is a little constricted, 
 forming a slight furrow ; or rather, the root at the neck is a 
 little smaller than the crown, and the enamel slopes down to 
 the size of the root, giving the appearance of a continuous ridge 
 of enamel around the neck. This line does not run horizon- 
 tally around the neck of the tooth. On the proximate sides 
 it forms curves with the convexity toward the crown, that on 
 the mesial being a little the greater, and on the labial and lin- 
 
26 UPPER CENTRAL INCISORS. 
 
 gual surfaces it forms a curve with the concavity toward the 
 crown. This line marks the limit of the attachment of the peri- 
 dental membrane and gum tissue to the root of the tooth. 
 
 21. Developmental lines (Fig. 5). When any of the 
 incisors first appear through the gums there are three little emi- 
 nences, or tubercles, called mammelons, on the cutting edge 
 with grooves crossing from labial to lingual between them 
 (a, g, h). These grooves run some distance on the labial sur- 
 face, becoming broader and shallower till they disappear. In 
 many, these lines appear on the lingual surface between the 
 marginal ridges and the fossa (f, f). Occasionally, they are 
 seen as far as the linguo-gingival ridge. The mammelons are 
 soon removed from the edge by wear, leaving it straight, or 
 slightly curved. These lines divide this part of the crown of 
 the tooth into three labial lobes. Calcification begins in these 
 mammelons as separate pieces, or plates, and the grooves are 
 the marks of the after-confluence of these plates. This is com- 
 mon to the incisors and cuspids. These teeth are sometimes 
 fissured across the cutting edge, marking an imperfect conflu- 
 ence of the primary plates. The calcification of the linguo-gin- 
 gival ridge, or cingulum, is also begun as a separate plate, form- 
 ing the lingual lobe, but afterward it becomes united to the 
 other parts by confluence, leaving a groove, often very slight, 
 indeed, and soon obliterated by wear, marking the line of 
 union. This is the linguo-gingival groove (e, £?), (This 
 groove is properly three grooves corresponding with the mesial, 
 central, and distal grooves of the bicuspids, while the linguo- 
 gingival ridge corresponds to the lingual cusp. See Par. 41.) 
 In smooth regularly formed teeth it begins at the gingival line 
 just lingual of the summit of its labio-lingual curvature, and 
 runs across the marginal ridge at right angles with its length, 
 then runs almost horizontally across the lingual surface to the 
 distal marginal ridge. This ridge is now crossed at right angles, 
 and the gingival line reached. The length of the groove usually 
 includes from a quarter to a third of the circumference of the 
 tooth. When the linguo-gingival ridge is prominent, or rises 
 
r-A 
 
 Fig. 6* (Par. 24).— Right Upper Lateral Incisor, Labial Surface, o, Cut- 
 ting edge; c, distal surface; c, labial grooves; /, gingival line; g, mesio-incisal 
 angle; /;, disto-incisal angle. 
 
 Fig. 7* (Par. 25). — Right Upper Lateral Incisor, Mesial Surface, a, 
 Mesio-incisal angle; d, linguo-gingival ridge; /, f, gingival line; t, body of root; k, 
 apex of root. 
 
 Fig. 8* (Par. 26). — Right Upper Lateral Incisor, Lingual Surface, without 
 lingual pit; a, Cutting edge; b, mesial marginal ridge; c, distal marginal ridge; d, 
 linguo-gingival ridge; f, gingival line; g-, mesio-incisal angle; k, disto-incisal angle; 
 >', body of root; k, apex of root; m, lingual fossa. 
 
 Fig. 9* (Par. 26). — Right Upper Lateral Incisor, Lingual Surface, with 
 lingual pit. a, Cutting edge; b, mesial marginal ridge; c, distal marginal ridge, 
 with linguo-gingival groove crossing it; d, linguo-gingival ridge, or cingulum; /, 
 gingival line; g, mesio-incisal angle; /;, disto-incisal angle; 1, body of root; k, apex 
 of root; tn, lingual pit. 
 
 Fig. 10* (Par. 26). — Right Upper Lateral Incisor, showing a linguo-gingival 
 fissure, a. Cutting edge; b, linguo-gingival groove fissured; /j gingival line; g, 
 mesio-incisal angle; h, disto-incisal angle. 
 
 Fig. II* (Par. 27). — Upper Lateral Incisor, Mesial Surface. Very short 
 root, a, mesio-incisal angle; d, linguo-gingival ridge; f, gingival line. 
 
 'Illustration, ij^ diameters. 
 
UPPER LATERAL INCISOR. 29 
 
 in the form of a tubercle, this groove is subject to much varia- 
 tion in its course. Often, there is a deep pit in the center of its 
 length; i.e., centrally in the lingual surface, at the margin of 
 the linguo-gingival ridge (Fig. 3, m). From this, fissures 
 may extend laterally. Occasionally, especially in the lateral 
 incisors, a sulcus, or a fissure divides the linguo-gingival ridge 
 from one of the marginal ridges, and extends into the cemen- 
 tum (Fig. 10). This is the linguo-gingival fissure. 
 
 22. The root of the upper central incisor (Figs, i to 5) 
 is about one and a fourth, to one and a half times as long as 
 the crown. It is conical in form, tapering from the crown to 
 the apex; less rapidly near the neck, and more rapidly as the 
 apex is approached. Therefore, the body of the root seems a 
 little swollen. However, the root of this tooth presents great 
 variety of figure, as do the roots of teeth generally. The root 
 is nearly round at the neck. The curvature of the lingual sur- 
 face is the arc of a smaller circle than that of the labial. The 
 proximate surfaces are slightly flattened. The flattened por- 
 tion of the mesial surface is a little broader than the distal. 
 These two converge to the lingual, giving the form of a prism 
 with its angles rounded. 
 
 UPPER LATERAL INCISOR. 
 
 23. The description of the lateral incisor may be much 
 abridged, because of its resemblance to the central in its gen- 
 eral form and developmental lines. The tooth is a little 
 shorter, and from mesial to distal the crown is about a third 
 narrower. 
 
 24. The labial surface of the lateral incisor (Fig. 6) is 
 more rounded in the mesio-distal direction than in the central. 
 The mesio-incisal angle is acute, and the cutting edge slopes 
 away in a curve to a rounded and obtuse disto-incisal angle. 
 The cutting edge, at the time of eruption, presents three tuber- 
 cles, or mammelons, and the grooves crossing the edge between 
 these are projected on the labial surface as shallow labial 
 grooves. 
 
30 UPPER LATERAL INCISOR. 
 
 25. The mesial (Fig. 7) and distal surfaces present 
 the characteristic V-shape of all the incisors. From labial to 
 lingual the mesial surface is rounded near the cutting edge, but 
 much flattened near the gingival line./ Sometimes a slight con- 
 cavity exists at this point. Occasionally the mesio-labial angle 
 has a flattened or sunken point of enamel near the middle of its 
 length. This is sometimes broad and of notable depth, and in 
 this case is generally in the labial portion of the mesial surface. 
 In others, it is a small imperfection in the mesial margin of the 
 labiail surface. The distal surface is convex in all directions. 
 In its incisal third, it rounds out freely toward the cuspid, but 
 becomes more flattened toward the gingival line. 
 
 26. The lingual surface (Fig. 8) of lateral incisors is 
 very irregular in the extent of its concavity. Some are almost 
 flat, while others are deeply concave. The mesial and distal 
 marginal ridges are proportionately broader and stronger than 
 in the centrals. In the majority of examples the lingual sur- 
 face is the broadest part of the crown. The rounding of the 
 proximate surfaces is at the expense of the labial surface, so 
 that a moderately acute angle is formed by the junction of the 
 
 "proximate surfaces with the lingual. ' Generally, the lingual 
 surface is almost smooth, but in many, a pit, with or without 
 lateral fissures, will be found at the junction of the lingual sur- 
 face proper, with the linguo-gingival ridge (Fig. 9). In some 
 of these, the linguo-gingival ridge is unusually short, so that 
 the marginal ridges are folded in together at their gingival 
 ends, forming a deep sulcus between them, and there is a deep 
 pit at their junction. Again, some are found in which there is 
 a deep groove, which is often fissured dividing one marginal 
 ridge from the linguo-gingival ridge, and extending into the 
 cementum (Fig. 10). This is sometimes nearly central, giving 
 the appearance of a failure of the lingual lobe, or of a division 
 of the lobe centrally, or of the displacement of the lobe to one 
 side. This is the linguo-gingival fissure. 
 
 27. The root of the upper lateral incisor (Figs. 6 to 11) 
 
, Fig. 12. 
 
 FiR- 15- 
 
 Fig. 12* (Par. 29). — Left Lower Central Incisor, Labial Surface. Long 
 root, a. Cutting edge; e, labial grooves; /, gingival line; g, mesio-incisal angle; h, 
 disto-incisal angle. 
 
 Fig. 13* (Par. 29). — Left Lower Lateral Incisor, Labial Surface. Long 
 root, a, Cutting edge; e, labial grooves; /, gingival line; g, mesio-incisal angle; h, 
 disto-incisal angle; i, body of root; k, apex of root. 
 
 Fig. 14* (Par. 29). — Right Lower Lateral Incisor, Labial Surface. Short 
 root, a. Cutting edge; e, labial grooves; /, gingival line; g, mesio-incisal angle; h, 
 disto-incisal angle; i, body of root; k, apex of root. 
 
 Fig. 15* (Par. 30). — Lower Central Incisor, Lingual Surface, a, Cutting 
 edge; /;. mesial marginal ridge; c, distal marginal ridge; d, linguo-gingival ridge; g, 
 mesio-incisal angle; h, disto-incisal angle; m, lingual ridge. 
 
 Fig. 16* (Par. 30). — Lower Central Incisor, Distal Surface, a. Cutting 
 edge; the edge is worn away as represented by the line; d, linguo-gingival ridge; 
 f, f, gingival line; i, groove along the distal side of root; k, apex of root. 
 
 Fig. 17* (Par. 31). — Right Lower Lateral Incisor, Distal Surface, showing 
 root deeply grooved, a, Cutting edge; d, linguo-gingival ridge; f, gingival line; t" 
 deep groove in root; k, apex of root. 
 
 ^Illustration, ij^ diameters. 
 4 
 
THE LOWER INCISORS. 33 
 
 is conical, but considerably flattened on its mesial and distal 
 sides, which is generally maintained to the apex. The root is 
 generally straight, and about one and a half times as long as 
 the crown. In many specimens the apex is curved to the distal. 
 Occasionally the root is very crooked. 
 
 28. The upper lateral incisor presents much variety of 
 size and form. It is not uncommon to find narrow laterals as- 
 sociated with broad centrals. The lateral upper incisors are 
 more often wanting, or imperfectly developed, than the other 
 anterior teeth. In the latter, the crown of the tooth is fre- 
 quently conical, with a rounded, or even a moderately sharp, 
 point. 
 
 THE LOWER INCISORS. 
 
 29. The lower incisors have outlines similar to the 
 upper lateral, but are, in every way, more slender. Their de- 
 velopmental lines are the same, but the grooves are much less 
 
 -^marked, and generally cannot be seen except in unworn teeth. 
 The cutting edge of the lower central (Fig. 12) is very nearly 
 at right angles with the long axis of the tooth, and its mesio- 
 and disto-incisal angles are square and sharp. From mesial to 
 distal, the cutting edge is the widest part of the crown, and 
 from it the proximate surfaces converge equally to the gingival 
 line, reducing the mesio-distal diameter about a third. '; The 
 lower lateral differs from the central by the cutting edge slop- 
 ing away to the distal, the mesio-incisal angle being acute, and 
 the disto-incisal angle obtuse and rounded. The distal surface 
 is also convex from the disto-incisal angle to the gingival line, 
 bellying out toward the cuspid. 
 
 30. The lingual surface (Fig. 15) of the lower incisors 
 is concave from the cutting edge to the linguo-gingival ridge, 
 over which there is a convexity (Fig. 16). 'Near the cutting 
 edge this surface is generally nearly flat in the mesio-distal 
 direction, but is sometimes concave or slightly convex; it be- 
 comes convex progressively toward the linguo-gingival ridge. 
 In many there is a slight ridge on the center of this surface with 
 a shallow concavity on either side, which marks the junction of 
 
34 THE CUSPIDS. 
 
 the lobes, running from near the cutting-edge to the linguo- 
 gingival ridge (Fig. 15). The mesial' and distal surfaces 
 are convex near the cutting edges, but become flattened, and 
 sometimes slightl}^ concave, toward the gingival line. 
 
 31. The roots of the lower incisors are slender and much 
 flattened in their mesio-distal diameter, and not unfrequently 
 slightly grooved on the mesial and distal sides. While the flat- 
 tening of the crown of the lower central is generally at right 
 angles with the flattening of its root, the distal portion of the 
 crown of the lower lateral is directed more to the lingual, so as 
 to appear slightly twisted on its root in most examples. The 
 labial surface of the crown and root, in its length, forms nearly 
 the arc of a circle (Fig. 17), though the curve of the surface 
 of the crown is usually a little greater than that of the root 
 (Fig. 16). The lingual surface of the root is almost straight, 
 but in the apical third it is conv^ex, sloping away to form the 
 apex. The roots of these teeth are generally straight, but occa- 
 sionally the apex is curved to the distal. 
 
 THE CUSPIDS. 
 
 32. We have four cuspids, one on each side in the upper, 
 and one on each side in the lower jaw. They are sometimes 
 called canine teeth, or eyeteeth. They are situated at the an- 
 gles of the mouth, between the lateral incisors and the first bi- 
 cuspids. They are third from the median line, and are large, 
 and strong teeth of simple form, firmly implanted in the alve- 
 olar process by a long, strong root. 
 
 THE UPPER CUSPIDS. 
 
 33. The labial surface of the crown of the upper cuspid 
 (Fig. 18) is a little narrower in the mesio-distal direction than 
 in the central incisor, with nearly equal length from the point 
 of the cusp to the gingival line. Instead of a straight, or only 
 slightly curved cutting edge, as in the incisors, the central por- 
 tion of the crown is extended nito a well-formed point (a), 
 

 Fig. 21. 
 
 Fig;. 22. Fig. 23. Fig. 24. 
 
 Fig. 18* (Par. 33). — Right Upper Cuspid, Labial Surface, a, Point of cusp; 
 d, labial ridge; e, labial grooves; /, gingival line; g, mesio-incisal angle; h, disto- 
 incisal angle; ;, body of root; k, apex of root. 
 
 Fig. 19* (Par. 34).— Right Upper Cuspid, Lingual Surface. The more com- 
 mon form. a. Point of cusp; d, linguo-gingival-ridge; e, c, lingual grooves; f, 
 gingival line; g, mesio-incisal angle; /;, disto-incisal angle; i, body of root; k, apex 
 of root; 7!!, lingual ridge. 
 
 Fig. 20* (Par. 34). — Right Upper Cuspid, Lingual Surface of irregular form. 
 
 a. Point of cusp; d, linguo-gingival ridge; e, e, lingual grooves; /, gingival line; g, 
 mesio-incisal angle; h, disto-incisal angle; m, prominent lingual ridge; n, two small 
 tubercles on linguo-gingival ridge. 
 
 Fig. 21* (Par. 35).— Right Upper Cuspid, Mesial Surface, a. Point of cusp; 
 
 b, mesial marginal ridge; c, point of slight concavity of mesial surface; d, linguo- 
 gingival ridge; e, labial groove; f, f, gingival line; g, mesio-incisal angle; 1, body 
 of root; k, apex of root. 
 
 Fig. 2?* (Par. 37). — Left Upper Cuspid, with a very long and crooked root. 
 Fig. 23* (Par. 37). — Right Upper Cuspid, with a peculiarly crooked root. 
 Fig. 24* (Par. 3j). — Left Upper Cuspid, with a very small and short root. 
 
 *Illustration, i^ diameters. 
 
THE UPPER CUSPID. 37 
 
 with cutting edges sloping away to the mesio-incisal and disto- 
 incisal angles (g^ h). Of these cutting edges, the distal is a 
 little the longer, and from the disto-incisal angle to the gingival 
 line, the distal surface is a little shorter than the mesial. In 
 unworn teeth, the angle formed by the union of the cutting edges 
 to form the cusp is usually about ninety degrees, or a square. 
 The point is a little rounded at first, but is soon much rounded 
 or flattened by wear." Both the mesial and distal margins of the 
 labial surface of the crown, from the mesio- and disto-incisal 
 angles to the gingival line, slope toward the central axis of the 
 tooth — the distal slope being the greater. This narrows the 
 crown at the neck nearly one-third from the width of its widest 
 point. The curvature of the gingival line on this surface, 
 marking the termination of the crown, is about a quarter circle. 
 
 -^T'he surface is convex in all directions, and is much more 
 rounded in the mesio-distal direction than in the incisors. In 
 the direction of its length, the convexity is about the same as in 
 the incisors. The greater convexity mesio-distally is caused by 
 a strong labial ridge {d) running from the point of the cusp 
 to the gingival line. This ridge occupies so much of the sur- 
 face of the tooth that its margins are imperfectly defined. It 
 belongs to the middle lobe, developed from the middle plate, 
 which, in the incisors, is the smallest of the three, but in this 
 tooth is much the largest. There are two labial furrows {e), 
 or a flattening of the convexity between the central line of the 
 ridge and each angle, marking the junction of the lobes. These 
 furrows are usually lost by becoming shallower before reaching 
 the center of the length of the crown. In well-formed teeth, 
 this surface presents a uniform enamel, free from pits or sulci. 
 
 -' 34. The lingual surface (Fig. 19) presents the same 
 general marginal configuration as the labial, though it is some- 
 what narrower toward the gingival line.; This is caused by the 
 arc of convexity of the lingual surface of the neck of the tooth 
 being of a smaller circle than that of the labial, and by the flat- 
 
38 THE UPPER CUSPID. 
 
 tening of the proximate surfaces on lines which converge rap- 
 idly to the lingual. This surface is usually almost straight 
 from the cusp to the linguo-gingival ridge, or cingulum, but is 
 sometimes slightly concave. The linguo-gingival ridge is 
 sharply convex and longer from the gingival line to the point 
 of convexity than in the incisors. (Fig. 21, d.) Mesio-distally 
 this surface is slightly convex in its central part on account of 
 the lingual ridge which runs from the point of the cusp nearly, 
 or quite, to the cingulum. On each side of this, and between it 
 and the marginal ridges, there is a slight, but well-defined con- 
 cavity and furrow, marking the confluence of the lobes. The 
 marginal ridges arise from the mesio- and disto-incisal angles 
 and unite with the linguo-gingival ridge or cingulum. These 
 ridges are usually large near the angles, and much less pro- 
 nounced toward the linguo-gingival ridge. The latter is promi- 
 nent, and is often raised into a tubercle, or slight cusp. Occa- 
 sionally this part of the enamel is thrown into irregular folds, 
 with grooves between, which are sometimes fissured. ; More 
 rarely the small cusp may be divided by a groove (Fig. 20, n). 
 The linguo-gingival groove is often pronounced in unworn 
 teeth. 
 
 35. The mesial surface, near the incisal angle (Fig. 
 21), is convex in all directions, but becomes flattened, and occa- 
 sionally slightly concave, near the gingival line (c). 
 
 36. The distal surface is similar to the mesial, but is 
 more convex, usually being well rounded in the lablo-lingual 
 direction to the gingival line./ But in the direction of the long 
 axis of the tooth this surface, on account of its distal projection 
 is first convex, and further toward the gingival line is concave, 
 especially near and at the neck of the tooth. The labio-lingual 
 curvature of the gingival line is about 2.5 m.m., varying from 
 i.o m.m. to 3.5 m.m. on the mesial surface, and a little less on 
 the distal. 
 
 37. The root of the upper cuspid is the longest in the 
 human mouth, averaging, according to my measurements, 17.5 
 
Fig. 29. 
 
 Fig. 25* (Par. 38). — Left Lower Cuspid, Labial Surface, a. Point of cusp; 
 
 b, mesial surface; c, distal surface; d, labial ridge; e, distal labial groove; /, gingi- 
 val line; g, mesio-incisal angle; /;, disto-incisal angle; t, body of root; k, apex of 
 root. 
 
 Fig. 26* (Par. 38). — Left Lower Cuspid, Mesial Surface, a, Point of cusp; 
 d, linguo-gingival ridge; f, gingival line; g, mesio-incisal angle; i, body of root, 
 which is distinctly flattened; k, apex of root. 
 
 Fig. 27* (Par. 38). — Left Lower Cuspid, Distal Surface, a, Point of cusp; 
 
 c, labial groove; d, linguo-gingival ridge; e, concavity of the distal cutting edge 
 where the groove passes over it; /, gingival line; h, disto-incisal angle; i, body of 
 root; k, apex of root. 
 
 Fig. 28* (Par. 39). — Left Lower Cuspid, Lingual Surface, a. Point of cusp; 
 
 d, linguo-gingival ridge; c, lingual grooves; /, gingival line; g, mesio-incisal angle; 
 h, disto-incisal angle j i, body of root; k, apex of root; /, distal marginal ridge; m, 
 lingual or triangular ridge; n, mesial marginal ridge. 
 
 Fig. 29* (Par. 40). — Right Lower Cuspid, Mesial Surface, a, Point of cusp; 
 d, linguo-gingival ridge; /, gingival line; g, mesio-incisal angle. The root is short 
 and thick. 
 
 *IIlustration, lYz diameters. 
 
THE LOWER CUSPIDS. 4I 
 
 m.m., and varying from ii.o to 21.0 from the apex to the gin- 
 gival line at the labial surface. It is irregularly conical in 
 form, tapering from the neck to the apex. Its labio-lingual 
 diameter is a little greater than its mesio-distal, which gives 
 the root a flattened appearance, but it is seldom entirely flat on 
 either the mesial or distal surface. In most examples the body 
 of the root is straight, and tapers to a slender point, which is 
 often curved to the labial and distal, though the form of this 
 root presents great variations. Frequently, it is very crooked, 
 perhaps, because, when it is taking its place in the arch, it is 
 often crowded by the teeth mesial and distal to it, so that its 
 growth in a right line is interrupted. (See Figs. 22, 23, 
 and 24.) 
 
 THE LOWER CUSPIDS. 
 
 38. In their general figure, the lower cuspids so closely 
 resemble the upper, a description of their differences will be 
 sufficient. They are slightly smaller than the upper cuspids, 
 and the crowns are a little longer, which make them appear 
 more slender. The mesial surface of these teeth is usually 
 nearly straight the entire length of the root and crown (Figs. 
 25 and 26) ; so that the increased width of the crown over the 
 root is mainly on the distal. This causes a marked prominence 
 of the disto-incisal angle. In many examples this gives the 
 tooth the appearance of being bent, with a considerable con- 
 cavity on the distal side in the cervical region: ; In young, un- 
 worn teeth, the cusp is rather more prominent and pointed than 
 in the upper cuspid, and the distal cutting edge is proportion- 
 ately longer; but, as the point of the cusp comes directly in 
 occlusion with the upper teeth, it is soon worn to a blunt point, 
 or a flat surface, inclining to the labial and sloping away to the 
 distal. 
 
 39. The lingual surface (Fig. 28) is very smooth, and 
 the ridges are less prominent than in the upper cuspid. A 
 tubercle on the linguo-gingival ridge is rare. The develop- 
 mental lines, or grooves, are the same as those of the upper 
 
42 THE BICUSPIDS. 
 
 cuspids, but less prominent. Yet, generally, they can be seen 
 in unworn teeth. Fissures are seldom seen in any part of this 
 tooth. 
 
 40. The root of the lower cuspid (Figs. 25 to 29) is 
 shorter than the upper, and generally more flattened in the me- 
 sio-distal diameter, often presenting deep furrows. In rare in- 
 stances, there is a division of the root near the extremity. The 
 root is nearly straight, and in many examples the lingual sur- 
 face of the root is nearly a straight line, while the labial sur- 
 face, root, and crown, present a nearly regular convexity. The 
 root is not so often abnormally crooked as that of the upper 
 cuspid, though, like the upper, it is much inclined to end in a 
 slender apex, which is often slightly bent in the labial direction! 
 
 THE BICUSPIDS. 
 
 41. There are eight bicuspids, or premolars, two on each 
 side in the upper jaw, and two on each side in the lower jaw. 
 Hence they are called the first and second bicuspids. They 
 are situated between the cuspids and first molars, and are the 
 fourth and fifth teeth from the median line. The bicuspids, 
 though unlike the incisors and cuspids in the contour of their 
 crowns, have the same number, and a similar distribution of 
 primary parts, or lobes. They are, indeed, formed on the 
 same general plan. The change of form is the result of a 
 different relative development of the parts, by which the cingu- 
 lum, or linguo-gingival ridge, is elevated into a powerful 
 lingual cusp, which, in the upper bicuspids, is almost or quite 
 as 'high as the buccal cusp, but in the lower bicuspids, espe- 
 cially in the" first, is less prominent. The middle lobe also forms 
 a relatively larger part of the buccal portion of the crown than 
 in the incisors and cuspids ; while the mesial and distal lobes 
 are relatively smaller. By the development of the lingual cusp 
 of the upper bicuspids, the linguo-gingival grooves of the in- 
 cisors and cuspids {q.v.21) are carried to the central part of the 
 crown, which they traverse from mesial tadistal in a deep sulcus 
 (Fig. 30). It is naturally divided, by the mesial and distal pits 
 
Fig. 30- 
 
 Fig- 33- 
 
 /> 
 
 Fig. 34- 
 
 Fig. 30* (Par. 42). — Left Upper First Bicuspid, Occlusal Surface. a. 
 Point of buccal cusp; 6, lingual cusp; c, buccal ridge; d, mesial marginal ridge; e, 
 distal marginal ridge; f, triangular ridge of the buccal cusp; g, disto-bucco-occlusal 
 angle; h, mesio-buccal occlusal angle; i, triangular ridge of the lingual cusp; /, cen- 
 tral groove; 0, mesial groove; p, distal groove; ", m, triangular grooves; r, s, 
 buccal grooves. 
 
 Fig. 31* (Par. 46).— Left Upper First Bicuspid, Buccal Surface, o. Buccal 
 cusp; c, buccal ridge; e, e, buccal grooves; f, gingival line; g, mesio-bucco-occlusal 
 angle; h, disto-bucco-occkisal angle; /, buccal root; k, lingual root. 
 
 Fig. 32* (Par. 48). — Right Upper First Bicuspid, Mesial Surface, a, Buccal 
 cusp; b, lingual cusp; c, mesio-buccal-occlusal angle; d, mesial surface and point 
 where there is often a concavity; /, /, gingival line; e, lingual root; g, buccal root. 
 
 , Fig. 33* (Par. 50).— Upper First Bicuspid, with three roots. Mesio-buccal 
 angle. 
 
 Fig. 34* (Par. 50). — Upper First Bicuspid, with three short roots and of a 
 peculiar form. 
 
 Fig. 35* (Par. 5c). — Upper First Bicuspid, with a single, very long, crooked 
 root. 
 
 Illustration, i>4 diameters. 
 
UPPER FIRST BICUSPID. 45 
 
 found at its junction with the triangular grooves, into three 
 parts: mesial (o), central (/), and distal (p). In the lower 
 bicuspids the lingual lobe is often very small and the course of 
 the grooves irregular. 
 
 UPPER FIRST BICUSPID. 
 
 42. The outline of the occlusal surface of the upper 
 first bicuspid (Fig. 30), when seen in a line with the long axis 
 of the tooth, is irregularly quadrilateral or trapezoidal, in form. 
 The bucco-lingual diameter is about two-ninths greater than 
 the mesio-distal. The flattened proximate surfaces converge 
 toward the lingual, so that the mesio-distal measurement of 
 the buccal portion is a little greater than the lingual. The 
 buccal and lingual margins are convex. The buccal convexity 
 forms an arc of about a quarter circle, and merges into the 
 proximate surfaces by obtuse, but well-defined, angles (h, g). 
 The lingual margin forms an arc of nearly half a circle, and 
 merges into the proximate margins without any angular 
 prominence. 
 
 43. The occlusal surface has two prominent cusps — the 
 buccal (a) and the lingual (b) — and is transversed from mesial 
 to distal by a deep sulcus. The buccal cusp is the larger, 
 and forms the terminal point of the buccal surface. From the 
 point of this cusp, four ridges lead away at right angles. Two 
 of these form cutting edges, which slope away mesially and 
 distally to the mesio-bucco-occlusal (h) and disto-bucco-occlu- 
 sal angles (g), where they join the mesial and distal marginal 
 ridges. The central buccal ridge (c) leads away centrally on 
 the buccal surface toward the gingival line, forming the con- 
 vexity of this surface. The triangular ridge (f) slopes down 
 to the central part of the crown and joins a similar ridge from 
 the lingual cusp (i) to form the transverse ridge, or ends in a 
 central sulcate groove (/). The lingual cusp (&) is in the 
 form of a crescent ; its convexity forms the occlusal margin of 
 the lingual surface. Instead of a well-defined point it usually 
 presents a blunt edge, which runs around its elevated central 
 
46 UPPER FIRST BICUSPID. 
 
 "portion, and joins with the marginal ridges at both angles. The 
 lingual triangular ridge (i) leads down from the central point 
 of the cusp to the central groove, to join its fellow from the 
 buccal cusp in the formation of the transverse ridge, or is 
 divided from it by a deep central sulcate groove. This ridge 
 is seldom prominent. Very frequently the central incline of 
 the lingual cusp is a plain surface. 
 
 44. The mesial (d) and the distal (e) marginal ridges 
 are strong ridges of enamel which rise in the mesial and distal 
 terminations of the cutting edges of the buccal cusp, and form 
 the mesial and distal margins of the occlusal surface. They 
 join with the ridge forming the lingual cusp, or they are usu- 
 ally divided from the latter by the mesial and distal grooves, 
 though these grooves are often indistinct, especially in teeth 
 that have been somewhat worn. 
 
 45. The occlusal surface of the bicuspids has five de- 
 velopmental grooves — the central (/), mesial (0), distal (p), 
 mesial triangular (;n), and distal triangular (n). The cen- 
 tral groove is deeply sulcate, and divides the triangular ridges, 
 or passes over their junction as a shallow line, and sinks into 
 a triangular pit at either end. The mesial and distal grooves 
 are really continuations of the central, which pass over the 
 marginal ridges as very fine lines, or as more definite grooves, 
 and mark the boundary of the lingual lobe. They are rarely 
 fissured, while the central groove is frequently fissured through- 
 out its course. The triangular grooves, mesial (w) and distal 
 (w),run from the mesial and distal pits toward the mesio-buccal 
 and disto-buccal angles, dividing the marginal ridges from the 
 triangular. They are occasionally sulcate in the first part of 
 their course, and are generally lost toward the mesio- and disto- 
 buccal angles by becoming shallower; but in young, unworn 
 teeth they can often be followed as a fine line running over the 
 cutting edges of the buccal cusp near the angles, and leading 
 into the buccal grooves (r, s). These are the marks of con- 
 fluence of the mesial and distal lobes with the middle lobe. In 
 the central incline of the lingual cusp, supplemental grooves 
 are often seen meeting the triangular grooves of the buccal 
 
Fig. 36. 
 
 ^ 
 
 Fig. 39. 
 
 Fig. 41. 
 
 Fig. 2(>* (Par. 51). — Right Upper Second Bicuspid, Occlusal Surface, a, 
 
 oint of buccal cusp; b, lingtial cusp; c, buccal ridge; e, mesial marginal ridge; d, 
 
 distal marginal ridge ; /, triangular ridge of the buccal cusp ; g, mesio-bucco-occlu- 
 
 sal angle; /;, disto-bucco-occlusal angle; i, triangular ridge of the lingual cusp; /, 
 
 central groove; m, n, triangular grooves; 0, p, buccal grooves. 
 
 Fig. 37* (Par. 52). — Right Upper Second Bicuspid, Buccal Surface. a, 
 Point of buccal cusp; c, buccal ridge; e, e, buccal grooves; f, gingival line; g, 
 mesio-bucco-occlusal angle; h, disto-bucco-occlusal angle; i, body of root; k, apex 
 of root. 
 
 Fig. 3S* (Par. 52). — Right Upper Second Bicuspid, Mesial Surface, a. 
 Buccal cusp; b, lingual cusp; /, gingival line; i, groove in the mesial side of the 
 root. 
 
 Fig. 39* (Par. 52). — Right Upper Second Bicuspid, Distal Surface, a. 
 Buccal cusp; b, lingual cusp; c, carious cavity near the proximate contact point; /, 
 gingival line; i, groove in distal side of root. 
 
 Fig. 40* (Par 53). — Upper Second Bicuspid, with a very crooked root. 
 
 Fig. 41* (Par. 53). — Upper Second Bicuspid, with a very short crook of the 
 root. 
 
 *Illustration, lYz diameters. 
 
 5 
 
UPPER FIRST BICUSPID. 49 
 
 side. The triangular grooves are occasionally fissured for a 
 short distance from their junction with the central. 
 
 46. The buccal surface of the upper first bicuspid 
 (Fig. 31) is similar to the labial surface of the cuspid (g. e^. 33). 
 The cusp is usually nearer the center of the crown, and gen- 
 erally somewhat to the distal ; therefore, the cutting edges 
 which run from the summit of the cusp to either angle may be 
 of about equal length. In some examples the distal edge is 
 the longer ; but usually the mesial edge is the longer. In the 
 gingival half of its length this surface is smoothly convex from 
 mesial to distal ; but further toward the occlusal margin, the 
 buccal ridge, which terminates in the cusp, becomes more 
 prominent, and a shallow buccal groove {e, e) appears at both 
 sides of the ridge, or between it and the angles. This surface 
 is also considerably narrowed toward the gingival margin, al- 
 most equally on the mesial and distal, so that the crown seems 
 much broader near the occlusal margin. 
 
 47. The lingual surface is regularly convex from me- 
 sial to distal. From the gingival margin to the summit of the 
 lingual cusp it is often a straight line ; but more generally it is 
 slightly convex, in many examples almost as convex as the 
 buccal surface. 
 
 48. The mesial surface (Fig. 32) is jnuch flattened 
 from buccal to lingual, but is generally slightly coriv^x over its 
 whole extent ; yet in many examples there is a slight co ncavity 
 nearJh£^.ging|yaJJirie, In the direction from the gingival lTne~ 
 to the occlusal margin, this surface is sliglitly convex through 
 its whole length, but not equally so through its buccal and 
 lingual half. The lingual portion is progressively njii^e 
 roijnded toward the occlusaT~surface ; while the buccal portion 
 Ts^nearly^straight to the bucco-occlusal angle.* 
 
 * The form of the proximate surfaces is especially important in 
 making contour fillings, for any concavity increases the difficulty of 
 forming good, clean margins at the gingival border. The unequal 
 convexity of the buccal and lingual halves is important, and requires 
 a special adaptation of instruments to make a perfect contour and 
 good, clean margins. 
 
50 UPPER SECOND BICUSPID. 
 
 49. The form of the distal surface agrees substantially 
 with the mesial, but is rather more conve x in a ll directions and 
 aiivcon^avit y isj;are^ 
 
 50. The root of the upper first bicuspid is usually either 
 much flattened and grooved on its mesial and distal sides, or 
 separated into two divisions, one-third to two-thirds of its 
 length, making one buccal and one lingual root. More than 
 half have their roots thus divided. When separated, the roots 
 taper regularly to slender apexes. When not divided, the 
 apex is apt to be obtuse. Occasionally this tooth presents 
 three divisions of the root, two buccal and one lingual (Figs. 
 33, 34). In some instances the root of this tooth is very 
 crooked or otherwise distorted (Fig. 35). 
 
 UPPER SECOND BICUSPID. 
 
 51. The upper second bicuspid so nearly resembles the 
 upper first, just described, that a notice of its differences will 
 be sufficient. It is a little smaller, and in every way more 
 slender.* The general form of the occlusal surface (Fig. 
 36) is similar to the first bicuspid. It presents a buccal and a 
 lingual cusp, and similar sulcus, ridges, grooves, and pits. 
 The average height of the cusps is considerably less than in the 
 first bicuspid. The marginal ridges are proportionally broader, 
 the mesial and distal pits closer to each other, and the central 
 groove shorter. The triangular grooves join the central 
 groove nearer the mesio-distal center of the tooth, making the 
 buccal triangular ridge narrower and more nearly pointed. In 
 many examples the enamel of the occlusal surface is thrown 
 into several shallow wrinkles, or sugpkmental grooves and 
 ridges, which radiate from the central groove, which occurs 
 but rarely in the first bicuspid. The buccal cusp is a little 
 nearer the mesio-buccal than the disto-buccal angle, so that the 
 distal edge is slightly the longer. 
 
 52. From mesial to distal, the buccal surface (Fig. 37) 
 is not so broad at the occlusal surface, and is a little broader 
 
 *The popular opinion is that the second bicuspid is the larger. 
 
Fig. 42. 
 
 Fig. 45- 
 
 Fig. 46. 
 
 Fig. 47- 
 
 Fig. 42* (Par. 54). — Right Lower First Bicuspid, Occlusal Surface, c, 
 Point of buccal cusp; b, lingual cusp or ridge; c, buccal ridge; d, mesial marginal 
 ridge; c, distal marginal ridge; /, triangular ridge of buccal cusp or buccal triangu- 
 lar ridge; g, mesio-bucco-occlusal angle; h, disto-bucco-occlusal angle; i, central 
 groove crossing the transverse ridge; /, mesial pit; 0, p, buccal grooves. 
 
 Fig. 43* (Par. 54). — Lower First Bicuspid, Occlusal Surface, a, Point of 
 buccal cusp; b, lingual cusp or ridge; c, triangular ridge of buccal cusp deflected to 
 one side; d, triangular groove with fissure; c, mesial marginal ridge; /, distal mar- 
 ginal ridge. 
 
 Fig. 44* (Par. 57). — Right Lower First Bicuspid, Buccal Surface, a, Buc- 
 cal cusp; d, buccal ridge; e, e, buccal grooves; /, gingival line; g, disto-bucco- 
 occlusal angle; h, mesio-bucco-occlusal angle; t, body of root; k, apex of root. 
 
 Fig. 45* (Par. 58). — Left Lower First Bicuspid, Mesial Surface, a, Buc- 
 cal cusp; b, lingual cusp or ridge; c, distal marginal ridge; d, triangular ridge of 
 buccal cusp; e, mesial marginal ridge; /, gingival line. 
 
 , ^ Fig. 46* (Par. 59). — Left Lower First Bicuspid, Lingual Surface. a, 
 Buccal cusp; b, lingual cusp or ridge; c, distal marginal ridge; d, triangular ridge 
 of buccal cusp; e, mesial marginal ridge; f, gingival line. 
 
 Fig. 47* (Par. 59). — Right Lower First Bicuspid, Lingual Surface, a, Buc- 
 cal cusp; b, lingual cusp or ridge; d, triangular ridge or buccal cusp; e, e, mar- 
 ginal ridges; /, gingival line. 
 
 "■Illustration, i^ diameters. 
 
LOWER FIRST BICUSPID. 53 
 
 at the neck, so that it has not so much of the bell-crown ap- 
 pearance as the first bicuspid. Otherwise, this surface has the 
 same, but less definitely defined outlines and markings. The 
 mesial and distal surfaces (Figs. 38 and 39) are generally 
 slightly more convex, and the crown more smoothly rounded. 
 The mesial surface seldom shows a concavity. The lingual 
 surface is usually a little more rounded toward the cutting 
 edge or crest of the cusp. Generally, the distal side of the 
 lingual cusp is rounded to such an extent as to bring the sum- 
 mit of the cusp to the mesial of the central line of the tooth. 
 The gingival line, in its course round the neck of the tooth, 
 makes but a slight bucco-lingual curvature on the mesial sur- 
 face. Generally there is no curvature on the distal surface. 
 
 53. The root of the upper second bicuspid is a little 
 longer than the first, while the crown is slightly shorter, 
 which makes the proportionate increase of length appear 
 considerable. The root is rarely divided in any part of its 
 length, but is much flattened from the neck to the apex. 
 The mesial side is often deeply grooved in the apical third 
 of its length; the distal side is less frequently grooved. The 
 root tapers very gradually, remaining broad in the bucco- 
 lingual diameter, and ends in a blunt apex. A few have a 
 root that tapers rapidly, becomes more rounded, and ends in 
 a slender apex. Crooked roots are more frequent in this than 
 in the other bicuspids. (Figs. 40 and 41.) 
 
 LOWER FIRST BICUSPID. 
 
 54. This tooth is the smallest of the bicuspids. The 
 occlusal surface differs much from the upper first bicuspid. 
 Indeed, the lingual cusp is so nearly wanting, it would hardly 
 be called a bicuspid except for its association. The buccal 
 cusp is large and prominent, and so much is the buccal surface 
 inclined lingually, that, when seen in a line with the long axis 
 of the tooth, its point occupies a position about one-third 
 distant from the buccal toward the lingual outline of the 
 crown (Figs, 42 and 43). The buccal cusp presents the same 
 
54 LOWER FIRST BICUSPID. 
 
 ridges leading from its summit as described for the upper 
 first bicuspid (Par. 43), but the pair which form the cutting 
 edges usually form a curve with its convexity to the buccal, 
 and merge into the marginal ridges by more rounded angles. 
 The buccal triangular ridge is narrow and prominent (/), and 
 joins the elevated lingual ridge, or cusp (b), forming a com- 
 plete transverse ridge. In many instances this is deflected 
 to the mesial or distal. In young teeth, the central groove 
 often crosses the transverse ridge as a fine line, which soon 
 disappears by wear. However, in many examples the trans- 
 verse ridge is divided by a deeply sulcate groove. There is a 
 deep pit at the mesial and the distal ends of the central groove, 
 or on either side of the transverse ridge (c, d) from which the 
 triangular grooves, which divide the marginal ridges from 
 the triangular, or transverse ridge, run toward the mesio- and 
 disto-buccal angles. These are often sulcate in the first part 
 of their course. In many young teeth these grooves may be 
 traced over the cutting edges onto the buccal surface, marking 
 the confluence of the central with the mesial and distal buccal 
 lobes. 
 
 55. The lingual lobe varies much in its size and out- 
 line. It is divided from the three buccal lobes by the mesial, 
 distal, and central grooves ; and often occupies but a small 
 portion of the lingual margin of the occlusal surface. The 
 grooves which mark its outlines are often indistinct, and often 
 obliterated by wear. The lobe may form a ridge of even 
 height, and join the marginal ridges, or it may be elevated 
 into one or more tubercles. It may, also, be raised into a 
 small cusp, located centrally, or to either side of the central 
 line of the tooth. 
 
 56. The marginal ridges are occasionally quite small, 
 but in most examples they are well developed, and cause the 
 mesial and distal surfaces to stand out prominently, giving 
 the tooth a strong, bell-crowned appearance. The length of 
 the marginal ridges varies with the size of the lingual lobe. 
 
 57. The buccal surface (Fig. 44) is convex in all direc- 
 
LOWER FIRST BICUSPID. 55 
 
 tions. The cusp is to the distal of the perpendicular line and 
 its figure similar to the upper first bicuspid, except that its 
 surface is more convex. As the occlusion is directly on the 
 point of the cusp, as with the anterior lower teeth generally, 
 it is soon so worn down that its prominence is lost. 
 
 58. The mesial and distal surfaces are convex from 
 buccal to lingual. In the direction from the occlusal margin 
 to the gingival line, they are generally concave, after passing 
 the convexity of the immediate occlusal margin. This latter 
 stands out boldly to both mesial and distal, giving a marked 
 bell-crowned form. The concavity of the mesial and distal 
 surfaces is not so well seen from the buccal view as from the 
 lingual. The greater over-hang of the crown (over the root), 
 and the greater concavity, are toward the lingual portion. 
 
 59. The lingual surface (Figs. 46 and 47) is smoothly 
 rounded from mesial to distal, and slightly convex in the 
 direction of the length of the tooth. It is only about half 
 as long as the buccal surface (in unworn teeth), and when 
 viewed at right angles with the long axis of the tooth, all of 
 the occlusal surface on the lingual side of the buccal cusp is 
 seen except the pits and sulci. 
 
 60. The neck of the tooth is much constricted, and has 
 a deep gingival line. This makes the proper adjustment of 
 a band for an artificial crown particularly difficult. The 
 curvature of the gingival line is much less than in the upper 
 first bicuspid, the average being less than one millimeter (g. v. 
 table of measurements). 
 
 61. The root of this tooth is somewhat flattened at the 
 neck, on lines that converge rapidly toward the lingual, and 
 often grooved on its mesial and distal sides, and sometimes 
 the root is bifurcated. It tapers regularly, with a tendency 
 to a more nearly round form at the apex, and generally ends 
 in a slender point. The root is generally straight, or the 
 lingual surface is straight, and the buccal surface convex. 
 This convexity extends from the apex of the root to the point 
 of the crown, which gives that characteristic appearance so 
 peculiar to the anterior lower teeth. 
 
56 LOWER SECOND BICUSPID. 
 
 LOWER SECOND BICUSPID. 
 
 62. The lower second bicuspid is a little longer than 
 the lower first, and of much the same figure, except that the 
 lingual cusp is proportionately higher and more nearly, but 
 never quite, on a level with the buccal, but the lingual surface 
 is about equal to the buccal in mesio-distal breadth. These 
 teeth are regular in general contour, but the grooves of the 
 occlusal surface are much diversified. / These differences may 
 be classified under three forms: ist. The central groove 
 joins the triangular grooves in such a way as to form a half 
 circle with the convexity to the lingual, with or without a 
 transverse ridge crossing its line. In these, when the trans- 
 verse ridge is high, only a deep pit appears on either side 
 (Fig. 48). 2d. The lingual cusp is divided by a sulcate 
 groove, which runs over centrally, or nearly so, to the lingual 
 surface, making a three-cusped tooth (Fig. 49), The central 
 groove forms an angle at the junction with the lingual, or is 
 crescentic in form. It joins with the triangular grooves in 
 such a way that the point of junction cannot be told except 
 by finding the mesial and distal grooves, which are often very 
 indistinct. 3d. The central groove is straight, and generally 
 sulcate, with a deep pit at each end. In many examples 
 these pits are crossed by the triangular grooves almost at 
 right angles with the central (Fig. 50). By tracing the fine 
 mesial and distal grooves carefully in young unworn teeth, 
 it will be found that the lingual lobe is much larger than in 
 the lower first bicuspid, and almost as large as in the upper 
 bicuspids. In the three-cusped forms the two lingual lobes 
 are usually a little broader from mesial to distal than the 
 buccal portion of the tooth. 
 
 63. The buccal surface (Fig. 51) of the lower second 
 bicuspid does not differ from the other bicuspids, except in 
 being shorter, the cusp lower. The lingual surface (Fig. 52) 
 is broader and smoothly convex; in the three-cusped forms 
 it is often somewhat flattened and grooved in its occlusal 
 third, giving the crown a squarish appearance, or even trian- 
 gular when the lingual lobes are large. 
 
Fig. 4S. 
 
 Fig. 49. 
 
 Fig. 50. 
 
 ^.t 
 
 Fig. 51. 
 
 Fig. 52. 
 
 Fig. 53- 
 
 ■^ 
 
 Fig. 48* (Par. 62).— Left Lower Second Bicuspid, Occlusal Surface, a. 
 Buccal cusp; b, lingual cusp or ridge; c:, c, marginal ridges; d, f, pits; g, h, tri- 
 angular grooves. 
 
 Fig. 49* (Par. 62). — Right Lower Second Bicuspid, Occlusal Surface, with 
 three cusps, a, Buccal cusp; b, mesio-lingual cusp; c, disto-lingual cusp; d, lingual 
 groove; e, c, mesial and distal grooves. 
 
 Fig. 50* (Par. £2). — Right Lower Second Bicuspid, Occlusal Surface, with 
 straight central groove, a. Buccal cusp; b, lingual cusp; c, e, marginal ridges; d, 
 triangular ridge of the buccal cusp; f, central groove; g, h, triangular grooves. 
 
 Fig. si* (Par. €3). — Left Lower Second Bicuspid, Buccal Surface, a, Buc- 
 cal cusp; d, buccal ridge; e, e, buccal grooves; /, gingival line; g, mesio-bucco- 
 occlusal angle; /;, disto-bucco-occlusal angle; i, body of root; k, apex of root. 
 
 Fig. 52* (Par. 63). — Left Lower Second Bicuspid, Lingual Surface, a, 
 Buccal "cusp; b, lingual cusp; c, distal marginal ridge; d, triangular ridge of the 
 buccal cusp; e, mesial marginal ridge; /, gingival line. 
 
 Fig. S3* (Par. 64). — Left Lower Second Bicuspid, Mesial Surface, a. Buc- 
 cal cusp; /;, lingual cusp; rf. triangular ridge; e, mesial marginal ridge; /, gingival 
 line; i, groove in mesial side of the root. 
 
 "■Illustration, ij^ diameters. 
 
THE MOLAR TEETH THE UPPER MOLARS. 59 
 
 64. The mesial and distal surfaces in these bicuspids 
 are a little flattened, but remain convex from buccal to lingual. 
 From the occlusal margin to the gingival line, they are nearly- 
 straight, though some are convex and some in part concave. 
 ^ 65. The root of the lower second bicuspid is larger and 
 longer than that of the first bicuspid. It is flattened on the 
 mesial and distal surfaces on nearly parallel lines, and in some 
 examples concave or grooved. In rare instances the root of 
 this tooth is deeply grooved on the buccal and lingual sides, 
 with a tendency to a division into a mesial and distal prong. 
 In the greater number it tapers regularly to a 'slender apex, 
 but in many the apex is large and obtuse. The root is gen- 
 erally straight, but occasionally very crooked. 
 
 THE MOLAR TEETH. 
 
 66. The molar teeth are very different in form and plan 
 of construction from those previously described. They are 
 particularly designed for grinding or comminuting food; for 
 this purpose they have broad occlusal surfaces, broken by 
 ridges, grooves, and fossae. The ridges are raised at inter- 
 vals into powerful cusps, which fit with more or less accuracy 
 into the sulci and fossse of the opposing teeth. There are 
 twelve molars, three on each side of the upper jaw and three 
 on each side of the lower jaw. They are the sixth, seventh 
 and eighth teeth from the median line, and are commonly 
 named the first, second and third molars, upper and lower. 
 The last is also called the wisdom tooth, or Dens Sapientia. 
 The upper and lower molars are much alike in size and gen- 
 eral contour, but in the detail of the arrangement of their 
 lobes, cusps, fossse and grooves, they are different. / It will, 
 therefore, be necessary to describe the upper and lower molars 
 separately. 
 
 THE UPPER MOLARS. 
 
 6^. The three upper molars are similar, but present 
 minor differences of detail, consisting mostly in a less pro- 
 nounced, or typical development of certain parts, or lobes, of 
 the second and third molars (Fig. 62). The upper first molar 
 
6o UPPER FIRST MOLAR. 
 
 being the typical form, will be described first, and afterward 
 the deviations from this type that occur in the second and 
 third molars. 
 
 UPPER FIRST MOLAR. 
 
 68. The occlusal surface of the upper first molar (Fig. 
 54), when seen in a line with the long axis of the tooth, pre- 
 sents an outline of irregular rhombic form, with the mesio- 
 buccal and disto-lingual as acute angles. The angles are 
 rounded, with more or less convexity of the marginal lines. 
 This surface presents two principal fossae, and four develop- 
 mental grooves. These grooves divide the crown into four 
 lobes, or primary developmental parts, each of which is sur- 
 mounted by a strong cusp. These lobes, or cusps, are the 
 mesio-buccal (Fig. 54, a), disto-buccal (b), mesio-lingual (c), 
 and disto-lingual (d). Of the grooves which outline these 
 parts, three rise from the central pit of the central fossa : 
 The mesial (h), which runs to the mesial margin; the buccal 
 (i), which runs in a deep sulcus to the buccal margin, and 
 over it onto the buccal surface; and the distal (j)^ which 
 runs distally, and lingually, over the oblique ridge and ends 
 in the distal fossa (k). The remaining groove — the disto- 
 lingual (k^ k) — begins a little to the buccal of the central part 
 of the distal margin, and runs diagonally in a straight line, 
 or in a curve with the concavity toward the disto-lingual 
 angle, to the lingual margin, and over it onto the lingual 
 surface, to become the lingual groove. Except that part 
 crossing the distal marginal ridge, this groove is usually 
 deeply sulcate. 
 
 69. In their origin, each lobe begins its calcification as 
 a separate piece, plate, or cusp, and moves apart from the 
 others as growth proceeds, till the proper dimensions of the 
 occlusal surface are attained ; then the plates coalesce on the 
 lines marked by the grooves named above, and thus complete 
 the occlusal surface. When the union has been completed, 
 nothing but fine lines remain, which, on any plain parts, are 
 often quickly obliterated by wear. But on parts meeting at 
 
t X'^^i { 
 
 Fig. 58. 
 
 Fig. 54* (Par. 68).— Right Upper First Molar, Occlusal Surface, with four 
 cusps, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto- 
 lingual cusp; /, mesial m'arginal ridge; g, distal marginal ridge; h, mesial groove; 
 i, buccal groove; /, distal groove k, k, disto-lingual groove; m, mesio-buccal tri- 
 angular groove; n, disto-buccal triangular ridge; this unites with the distal ridge 
 from the lingual cusp to form the oblique ridge; 0, disto-buccal triangular groove; 
 p, mesio-buccal triangular ridge; q, central pit. 
 
 Fig. 55* (Par. 70). — Right Upper First Molar, Occlusal Surface, with five 
 cusps, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, .disto- 
 lingual cusp; c, fifth cusp; f, mesial marginal ridge; g, distal 'marginal ridge; /;, 
 mesial groove; i, buccal groove; /, distal groove; k, k, disto-lingual groove; /, k, 
 mesio-lingual groove; the lingual cusps are faceted by wear; m, mesio-buccal tri- 
 angular groove; n, disto-buccal triangular ridge. 
 
 — Fig. 56* (Par. 78). — Right Upper First Molar, Buccal Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual cusp; e, 
 buccal ridge; /, gingival line; g, mesio-bucco-occlusal angle; h, disto-bucco-occlusal 
 angle; i, buccal groove; k, mesial root; /, distal root; m, lingual root. 
 
 Fis. 57* (Par. 79). — Right Upper First Molar, Lingual Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual cusp; e, 
 fifth cusp; /, gingival line; g, disto-lingual groove; It, mesio-lingual groove; t, 
 lingual groove; k, mesial root; /, distal root; m, lingual root. 
 
 Fig. 58* (Par. So). — Right Upper First Molar, Mesial Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual cusp; e, 
 fifth cusp; f, f, gingival line; h, mesio-lingual groove; k, mesial root; /, distal root; 
 m, lingual root. 
 
 *Illustration, ij4 diameters. 
 
UPPER FIRST MOLAR. 63 
 
 an angle, forming a sulcus, as in the buccal and disto-lingual 
 grooves, there is usually a sharp groove, and at any point 
 where the union has been imperfect, there is a fissure.* 
 Fissures are most frequent at the ends of the grooves, near 
 the central pit, or where they are deeply sulcate; and in the 
 central portion of the disto-lingual groove ; but they may occur 
 in any part of these lines. 
 
 70. In many examples of the upper first molars, but in 
 no others, there is a small fifth lobe or cusp (Fig. 55, e). 
 This is situated on the lingual side of the mesio-lingual lobe, 
 from which it is divided by a fifth groove, the mesio-lingual 
 {I, ^), which runs from the lingual portion of the mesial margin 
 diagonally to the lingual margin, and joins the lingual groove. 
 This cusp, when it occurs, is always bilateral, i. e., on both the 
 right and left upper first molars. It is hereditary, appearing 
 regularly in the teeth of children when present in the teeth of 
 both parents. It occurs also, in a modified form, when present 
 in but one parent. Therefore, the cusp will be found in all 
 possible varieties of development, from its largest size, as repre- 
 sented in Fig. 55, to the merest line marking its position on the 
 lingual side of the mesio-lingual cusp. 
 
 - 71. The occlusal surface of the upper first molar has four 
 marginal ridges, broken by the grooves described (Par. 68), 
 so as to form four principal eminences or cusps. These are 
 the buccal, lingual, mesial, and distal marginal ridges. Of 
 these, the mesial and distal marginal ridges are close upon the 
 margins of the surface. But the buccal and lingual are carried 
 toward the central line of the tooth by the inclination of the 
 buccal and lingual surfaces. In the upper molars the central 
 inclination of the lingual surface is much greater than that of 
 the buccal ; while in the lower molars the central inclination of 
 the buccal surface is the greater. The buccal marginal 
 
 * In large strong teeth it seems that the growth of the dentine pulp 
 is often too great for the enamel cap, so that the enamel-forming cells 
 are drawn apart, preventing a union of the enamel plates; hence fis- 
 sures are more frequent in large teeth. 
 
 6 
 
64 UPPER FIRST MOLAR. 
 
 ridge begins at the mesio-buccal angle, in the form of a blunt 
 cutting edge, and rises in a curved line to the summit of the 
 mesio-buccal cusp (Fig. 54, a), from which it descends dis- 
 tally to the buccal groove (i). From the summit of this cusp 
 the mesio-buccal triangular ridge (p) descends to the mesial 
 side of the central pit (q). This ridge is divided from the 
 mesio marginal ridge by the mesio-buccal supplemental 
 groove (m), which is sometimes deep, but generally shallow, 
 and occasionally absent. From the buccal groove the mar- 
 ginal ridge rises rapidly to the summit of the disto-buccal cusp 
 (b), then descends in a curve to the disto-buccal angle, to join 
 the distal marginal ridge (g). From the point of this cusp the 
 disto-buccal triangular ridge (or triangular ridge of the disto- 
 buccal cusp, 11), runs down to the distal side of the central pit, 
 where it joins a ridge from the mesio-lingual cusp to form the 
 oblique ridge, or is divided from this ridge by a sulcate dis- 
 tal groove. 
 
 72. The lingual marginal ridge begins at the mesio- 
 lingual angle as a rounded edge, and rises in a curve to the 
 summit of the mesio-lingual cusp (c), and descends, continu- 
 ing its curve, into a ridge, meeting the triangular ridge of the 
 disto-buccal cusp to form the oblique ridge. However, in a 
 less pronounced form, this marginal ridge descends from the 
 summit of the mesio-lingual cusp to the distal, where it is 
 deeply broken by the disto-lingual groove. On the distal side 
 of this groove it rises abruptly to the summit of the disto-lin- 
 gual cusp (d), from which it slopes away in a curve to join the 
 distal marginal ridge. 
 
 73. The mesial marginal ridge (/) is a strong band of 
 enamel running from the mesio-buccal to the mesio-lingual 
 angle of the occlusal surface. It forms the mesial boundary 
 of the occlusal surface, and the angle of junction of the mesial 
 and occlusal surfaces, or the mesio-occlusal angle. It is low 
 in the center of its length, and rises toward both angles. It 
 is crossed near its center by the mesial groove, usually as a 
 fine line, which is often obliterated by wear early in life. 
 
UPPER FIRST MOLAR. 65 
 
 Occasionally one or more small tubercles appear in the central 
 portion of this ridge, inclosed in what seems to be a division 
 of the mesial groove. 
 
 74. The distal marginal ridge (g) is a band of enamel 
 forming the distal boundary of the occlusal surface, from angle 
 to angle, and forms the angle of junction between the occlusal 
 and the distal surfaces, or the disto-occlusal angle. It is low 
 in the center of its course, and is crossed by the distal end of 
 the disto-lingual groove as a fine line, usually a little to the 
 buccal of the central point. 
 
 75. The central fossa is irregularly circular, and is 
 formed by the central inclines of the mesial marginal ridge, 
 mesio-buccal cusp, disto-buccal cusp, mesio-lingual cusp, and 
 oblique ridge. It is made irregular, and sometimes angular, 
 by the depth of the several sulcate grooves, or by the promi- 
 nence of the triangular ridges, especially that from the mesio- 
 buccal cusp. The central incline of the mesio-lingual cusp is 
 generally a plane surface, but is sometimes slightly concave, 
 and in about a fourth of its examples there is a low, triangular 
 ridge running from its apex directly to the central pit. The 
 oblique ridge is occasionally cut through by a deep and wide 
 distal sulcus, thus connecting the central with the distal fossa. 
 In a few examples two supplemental grooves or wrinkles arise 
 from the mesial groove at about the center of its length, and 
 run, one toward the mesio-buccal and the other toward the 
 mesio-lingual angle of the occlusal surface. These are often 
 of such depth and width as to form a small supplemental mesial 
 fossa. Of these grooves, the mesio-lingual is generally absent, 
 and the mesio-buccal (m) is generally present, though often 
 very shallow. 
 
 76. The distal fossa is formed by the distal incline of 
 the disto-buccal and mesio-lingual cusps and oblique ridge, 
 which meet the central incline of the disto-lingual cusp and 
 distal marginal ridge. It is traversed by the disto-lingual 
 groove, which is generally sulcate, and deepens into a pit at 
 the point where it receives the distal groove. From the buccal 
 
66 UPPER FIRST MOLAR. 
 
 portion a supplemental groove, the disto-buccal, runs well up 
 toward the summit of the disto-buccal cusp, dividing its trian- 
 gular ridge from the distal marginal ridge. 
 
 yy. In some molars many supplemental grooves or 
 wrinkles radiate from the centers of these fossae on the inclines 
 of the ridges and cusps, and in some poorly developed teeth 
 these are deeply fissured. The growth of enamel seems to 
 have reached ouf toward the line of junction in the form of 
 spiculse, and to have failed to fill out the space. 
 
 78. The buccal surface of the upper first molar (Fig. 
 56) is irregularly convex. Its length is about equal to the 
 mesio-distal breadth at the gingival line, while the width at 
 the widest point, near the occlusal margin, is about three- 
 tenths greater. Therefore, the mesial and distal margins con- 
 verge toward the neck. The mesial margin is almost straight, 
 after the rounding of its mesio-occlusal angle, but the distal is 
 convex. The occlusal margin is surmounted by the buccal 
 cusps {a, b), between which there is a deep notch, through 
 which the buccal groove passes from the occlusal to the buccal 
 surface. This groove passes centrally toward the gingival line 
 about half the length of this surface, dividing the occlusal por- 
 tion into a mesial and distal buccal ridge. In some examples 
 the groove continues across the gingival line to the bifurcation 
 of the roots. There is a bucco-gingival ridge of enamel (e) 
 near the gingival line which the buccal groove generally does 
 not cross. The mesio-distal convexity is greatest on this 
 ridge, and diminishes toward the occlusal margin. The sum- 
 mit of this convexity is on the mesial half, in a line with the 
 mesial root, and the surface falls away rapidly toward the 
 disto-buccal angle of the tooth. 
 
 79. The lingual surface (Fig. 57) is divided in a line 
 with the long axis of the tooth into a mesial and distal lobe 
 by the lingual groove (i). Both lobes are smoothly convex 
 from mesial to distal, and in a less degree from the gingival 
 line (/) to the occlusal margin. The gingival line is nearly 
 horizontal, and so sunken as to give the appearance of a gin- 
 
Fig- 59' 
 
 Fig. 60. 
 
 Fig. 6r. 
 
 
 Fig. 59* (Par. 8i). — Right Upper First Molar, Distal Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; d, disto-lingual cusp; f, f, gingival line; k, 
 mesial root; /, distal root; m, lingual root; 0, concavity of the distal surface. 
 
 Fig. 60* (Par. 82). — Left Upper First Molar, Buccal Surface. A bell- 
 crowned tooth. 
 
 Fig. 61* (Par. 85). — Upper First Molar showing the mesial and distal roots 
 united at their apexes. 
 
 Fig. 62* (Par. 86). — The Right Upper Molars showing the progressive dimi- 
 nution of the disto-lingttal cusp from the first to the third molar. 
 
 'Illustration, i5<^ diameters. 
 
UPPER FIRST MOLAR. 69 
 
 gival enamel ridge. The occlusal margin is surmounted by 
 the mesio- and disto-lingual cusps (c, d), of which the mesial 
 is usually the larger. In the five-cusped molar the fifth cusp 
 {e) is seen on the mesio-lingual lobe. The mesial and distal 
 margins are convex, converging rapidly toward the lingual 
 root. In the few examples in which the lingual groove is not 
 apparent, the lingual surface is smoothly convex from mesial 
 to distal. 
 
 80. The mesial surface (Fig 58) is nearly flat in all 
 directions, and its margins are rounded to the buccal and lin- 
 gual surfaces. Toward the occluso-buccal angle, the flat sur- 
 face is continued well up to the occlusal surface, which it meets 
 in a fairly sharp angle ; but as it approaches the linguo-occlusal 
 portion it is progressively rounded toward the occlusal surface. 
 In many molars, near the gingival line, half-way from buccal to 
 lingual, this surface is a little concave. 
 
 81. The distal surface (Fig. 59), in its lingual half, is 
 convex in all directions, but in its buccal half there is often 
 a concavity formed by a considerable distal protrusion of the 
 disto-lingual lobe. This is a shallow, but marked, depression 
 (0), running from the bifurcation of the distal and the lingual 
 roots toward the disto-buccal cusp. It crosses the gingival 
 line at a point about one-third distant from the buccal toward 
 the lingual margin. In many examples this depression is more 
 central and receives the distal termination of the disto-lingual 
 groove, which may often be traced as a fine line nearly or 
 quite to the gingival border of the enamel. This complication 
 of the surface makes the finishing of fillings, and the fitting of 
 bands for crowns, specially difficult. This depression falls short 
 of forming a concavity in about one-fourth of the first molars. 
 
 82. The root of the upper first molar (Figs. 56 to 61) 
 is divided into three prongs or roots* — the mesial, or mesio- 
 
 * The divisions of the root of a tooth are usually called "the roots," 
 and the upper molars are said to have three roots. The neck of the 
 tooth is, however, common to all, and, more strictly, there is one root 
 divided into several prongs, or fangs. Some authors follow this form 
 of expression. For instance. Prof. Judd says: "The root of a molar 
 is divided into three fangs." I see no good reason, however, for not 
 calling them roots, the term generally in use by the dental profession. 
 
70 UPPER SECOND MOLAR. 
 
 buccal (k), the distal or disfo-buccal (/), and the lingual (m). 
 These are usually quite widely separated, giving the tooth a 
 firm seat in its alveolus. The lingual root is the largest ; it 
 diverges boldly to the lingual, and is straight, or slightly 
 curved, with the convexity to the lingual. It is conical, and 
 tapers regularly to an obtuse rounded apex. In most molars 
 it has a groove, a continuation of the lingual, on its lingual 
 side, running nearly, or quite, its whole length. In rare ex- 
 amples this root bifurcates. 
 
 83. The mesial root (k) is larger than the distal; broad 
 from buccal to lingual, and thin from mesial to distal, with 
 the lingual portion the thinner, and grooved on its flattened 
 sides. It diverges first to the mesial and buccal, and then 
 curves to the distal. It tapers mostly at the expense of the 
 lingual thin edge, and ends in a flattened or rounded apex. 
 
 84. The distal root (/) is the smallest of the three. It 
 --diverges to the distal and buccal, and is straight, or slightly 
 
 curved, sometimes to the distal, sometimes to the mesial, so 
 that its apex approaches the mesial root. It is flattened on 
 its mesial and distal sides, but less than the mesial root, and 
 tapers to a more rounded form, ending in a slender point. 
 
 85. The roots of the first molar are, perhaps, more regu- 
 lar in form than those of any other of the molar teeth ; but even 
 in these, considerable deviation from the forms described will 
 occasionally be observed (Figs. 60 and 61). 
 
 UPPER SECOND MOLAR. 
 
 86. The most constant difference between the occlusal 
 surfaces of the upper first and second molars is that the lat- 
 ter tooth is smaller, and has an almost constant tendency to a 
 relatively smaller size of the disto-lingual lobe.| This ten- 
 dency is well seen in Fig. 62, in which the upper molars of a 
 very well formed denture are drawn from the cast. This shows 
 the disto-lingual lobe progressively diminished, so that in the 
 third molar it is very small. When a large number of second 
 molars are examined, it is found that the central fossse are not 
 
Fig. 64. 
 
 Fig. 65. 
 
 ^ 
 
 Fig. 66. 
 
 Fig. 67. 
 
 ^FiG. 63* (Par. 86). — Right Upper Second Molar, Occlusal Surface, with 
 
 three of the cusps faceted by wear. Tooth large and especially well developed, a, 
 Mesio-buccal cusp; 6, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual 
 cusp; /, mesial marginal ridge; g, distal marginal ridge; h, mesial groove; i, buc- 
 cal groo\'e; /, distal groove; k, disto-lingual groove; /, distal fossa; m, mesio-buccal 
 triangular groove; n, central pit; o, mesio-buccal triangular ridge; p, disto-buccal 
 triangular ridge; r, mesio-lingual triangular ridge. 
 
 Fig. 64* (Par. 86). — Right Upper Second Molar, Occlusal Surface, Tooth 
 of medium size and imperfect form, o, Mesio-buccal cusp ; b, disto-buccal cusp ; c, 
 mesio-lingual cusp; d, disto-lingual cusp; /, mesial marginal ridge; g, distal mar- 
 ginal ridge; h, mesial groove; t, buccal groove; /, distal fossa. The disto-lingual 
 groove is imperfect; tn, mesio-buccal triangular groove; o, mesio-buccal tri- 
 angular ridge; p, disto-buccal triangular ridge, which unites with the ridge from 
 the rriesio-lingual cusp to form the oblique ridge. 
 
 Fig. 65* (Par. 87). — Right Upper Second Molar showing a form of deformity 
 peculiar to this tooth that is not very common. 
 
 Fig. 66* (Par. 89).— Right Upper Second Molar with the roots inclined to 
 the distal. 
 
 Fig. 67* (Par. 90).— Right Upper Second Molar, Distal Surface, with the 
 three roots compressed into one. 
 
 Fig. 68* (Par. 90). — Right Upper Second Molar, showing the distal and lin- 
 gual roots united. 
 
 'Illustration, ij^^ diameters. 
 
UPPER SECOND MOLAR. 73 
 
 SO regularly formed as in the first, being often small, even in 
 large, well-developed teeth (Fig. 63), and the cusps compara- 
 tively low, with a relatively greater inclination of the lingual 
 surface toward the summit of the mesio-lingual cusp. In 
 many examples the distal fossa is reduced to a mere pit (Fig. 
 64), and the lingual marginal ridge is continued from the sum- 
 mit of the mesio-lingual cusp distally to the disto-lingual angle, 
 where it joins the distal marginal ridge, as in Fig. 64, making 
 practically a three-cusped tooth. In many of these, after the 
 tooth is a little worn, the disto-lingual groove cannot be traced 
 across the lingual marginal ridge, nor on the lingual surface; 
 but a fine line is generally seen crossing the distal marginal 
 ridge. 
 
 87. The upper second molar is Hable to a peculiar 
 deformity, which I have not seen in any other tooth. The 
 crown is greatly flattened from mesial to distal, occasionally 
 to such an extent as to present none of its usual lines. In 
 the extreme cases (Fig. 65) there is one central, long-shaped 
 sulcus running from buccal to lingual, formed by the central 
 inclines of a ridge encircling the occlusal surface. This ridge 
 may be broken at intervals by shallow grooves crossing it. 
 Usually, much of the central inclination of this ridge is wrin- 
 kled, and often there are many small fissures. The mesial sur- 
 face is commonl}^ deeply concave, and the distal convex. 
 
 88. In well-developed second molars, the form of the 
 buccal, lingual, mesial, and distal surfaces is much the 
 same as in the first molar, though rather more convex, and 
 concavities in the mesial and distal surfaces are not so frequent. 
 However, in teeth with large disto-lingual cusps, the concavity 
 of the distal surface is about the same as in the first molar (Par. 
 81). The lingual groove is generally not sulcate, though it is 
 usually seen as a fine line in unworn teeth. It is often near the 
 disto-lingual angle, and, when sulcate, it generally disappears 
 by becoming shallower about half-way toward the gingival 
 line ; rarely it runs across the gingival line, and in that case the 
 lingual root is grooved, as in the first molars. 
 
74 UPPER THIRD MOLAR. 
 
 89. The neck of the tooth is less regular in its outline 
 than in the first molar. In the average, it is more flattened 
 from mesial to distal, and on lines that converge more to the 
 lingual. On the buccal surface, the mesio-buccal ridge is 
 relatively more prominent, and at the neck the surface slopes 
 away more toward the distal, so that in many examiples, the 
 distal roof seems compressed between the mesial and lingual 
 roots. 
 
 90. The roots of this tooth are the same in number and 
 general form as in the first molar, but they spread less, and 
 are curved more to the distal /(Fig. 66). There is also much 
 more variety of the comparative size of the root and crown 
 than in the first molar. In many the root is single, with the 
 outlines of the division marked by grooves of variable depth 
 (Fig. 67) ; or two of the roots may be connected, while the third 
 is free. Sometimes this union is the lingual with the distal 
 (Fig. 68) ; but oftener it is the lingual with the mesial root. 
 
 UPPER THIRD MOLAR. 
 
 91. The upper third molar deviates from the typical form 
 of the first more than does the second. Yet, in dentures of the 
 best form, it presents the same developmental lines, fossse, 
 and cusps (Fig. 69). The disto-lingual lobe is very much 
 smaller, and in many examples is entirely wanting. / Of the 
 examples in my possession, about twenty-one per cent, show a 
 diminutive disto-lingual cusp ; thirty-two per cent, show a pit 
 in the position of the distal fossa, and some portion of the disto- 
 lingual groove, but no depressed groove over the lingual mar- 
 ginal ridge; it is similar to that shown in Fig. 64. The re- 
 mainder, or about forty-seven per cent., have no disto-lingual 
 lobe. Of the latter, three-fourths are properly three-cusped 
 teeth in which the oblique ridge becomes the distal marginal 
 ridge, and the distal groove runs over to the distal surface (Fig. 
 70). In the remainder, there is only an irregular ridge (Fig. 
 71), forming a central fossa, so marked with wrinkles or sup- 
 plemental grooves that the developmental lines are not satis- 
 
o^_£_L^ 
 
 Fig. 71. 
 
 Fig. 
 
 Fig. 73- 
 
 ^^—'9tg. 69* (Par. 91). — Right Upper Third Molar, Occlusal Surface, of typical 
 form, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto- 
 lingual cusp; e, mesial marginal ridge; /, distal marginal ridge; g, mesio-buccal 
 triangular ridge; h, disto-buccal triangular ridge; i, mesial groove; k, buccal 
 groove; /, distal groove; m, disto-lingual groove; n, central pit; 0, mesio-buccal 
 triangular groove. 
 
 Fig. 70* (Par. 91). — Right Upper Third Molar, Occlusal Surface, three 
 cusped, a, Mesio-buccal cusp; b, disto-bticcal cusp; c, lingual cusp; e, mesial mar- 
 ginal ridge; h, distal marginal ridge; /, mesial groove; k, buccal groove; /, distal 
 groove; 0, mesio-buccal triangular groove. 
 
 Fig. 71* (Par. 91). — Right Upper Third Molar, Occlusal Surface. Young, 
 unworn tooth of imperfect form, a, Mesio-buccal cusp; b, disto-buccal cusp; c, lin- 
 gual cusp; e, mesial marginal ridge; /, distal marginal ridge; g, mesial groove; h, 
 buccal groove; i, distal groove. Several supplemental grooves are seen radiating 
 from the central pit. 
 
 Fig. 72* (Par. 94). — Right Upper Third Molar, Buccal Surface. The roots 
 are not quite complete, and show the funnel-shaped openings at the apex. 
 
 Fig. 73* (Par. 94). — Left Upper Third Molar with five roots. 
 
 'Illustration, 1J-2 diameters. 
 
UPPER THIRD MOLAR. 77 
 
 factorily made out. Many examples of the three-cusped teeth 
 show much relative diminution of the disto-buccal lobe. 
 
 92. The upper third molar is the smallest of the mo- 
 lars,* and is more irregular in its size and conformation than 
 the first or second molar. On account of the small size of 
 the disto-lingual lobe, the distal portion of the tooth is much 
 
 s smailerutlian . th£_ mesi^ [and in the three-cusped teeth the 
 
 crown becomes triangular, with its angles well rounded. (Fig. 
 70.) 
 
 93. The mesial surface resembles that in the upper 
 first and second molars, but is more rounded, so that a con- 
 cave portion is less frequent, and the distal surface is well 
 rounded. The lingual and buccal surfaces are more 
 rounded than the same surfaces in the other upper molars. 
 The gingival line is usually horizontal in its course around the 
 neck of the tooth, except that, in a few examples, there is a 
 slight curvature on the mesial surface. Many upper third 
 
 _ molars are much flattened from mesial to distal. These gener- 
 ally have a considerable concavity on the mesial surface. Oc- 
 casionally teeth are found that are also abnormally small and 
 have the appearance of supernumeraries. More rarely this 
 tooth fails to develop, and is wanting entirely, 
 
 94. The root of the upper third molar has, in the more 
 regular forms, the three divisions common to the upper mo- 
 lars, though relatively smaller and not so widely separated as 
 those of the first and second molars ; and often end in slender 
 conical points; many have but a single root; but in most of 
 these the three roots are outlined by grooves of more or less 
 depth. A considerable number have more than three roots, 
 which are irregular in size or form (Fig. 73). Four, five, six, 
 and even seven or eight divisions are sometimes met. The 
 neck is then generally broad from buccal to lingual, and the 
 
 „,^ occlusal surface of the crown irregularly formed. / Many of the 
 
 three-cusped teetli have the root without divisions. 
 
 * Forty upper first molars balanced sixty upper third molars. 
 
78 THE LOWER MOLARS THE LOWER FIRST MOLAR. 
 
 THE LOWER MOLARS. 
 
 95. The lower molars differ so much from each other, 
 especially the first and second, that each must be separately 
 described. 
 
 THE LOWER FIRST MOLAR. 
 
 96. The lower first molar is the sixth tooth from the 
 median line in the lower jaw. It proximates the lower second 
 bicuspid with its mesial surface, and the lower second molar 
 with its distal. Next to the upper first molar, it is the largest 
 tooth in the denture.* The outline of the occlusal surface 
 (Figs. 74 and 75), when seen in a line with the long axis of the 
 ■tooth, is trapezoidal, with the buccal marginal line the longest, _ 
 The buccal angles are about equally acute, while the lingual 
 angles are equally obtuse, and all are more or less rounded. 
 The buccal margin is convex, but made irregular by two buc- 
 cal grooves. The lingual margin is nearly straight, but some- 
 times slightly concave, or notched in the center of its length, 
 by the lingual groove ; but more generally it is slightly convex. 
 The mesial and the distal margins are nearly straight in the 
 best formed teeth ; though the distal is sometimes considerably 
 convex, as the fifth, or disto-lingual cusp is more or less promi- 
 nent. All of these margins vary as to their convexity ; the rule 
 being that, in teeth of large size and symmetrical development, 
 they approach nearer to straight lines. 
 
 97. Each of these marginal portions is surmounted by 
 the mesial, buccal, lingual, and distal marginal ridges, which 
 form a continuous elevation of irregular height around the 
 margins of the occlusal surface, and on which there are five 
 cusps. The central inclinations of these ridges form the 
 central fossa. On the mesial, lingual, and distal, the sum- 
 mits of these ridges are close on the margins of the surface; 
 but on the buccal, there is an inclination of the buccal surface ; 
 that carries the summit of the ridge considerably toward the 
 central axis of the tooth. 
 
 * Forty-two upper first molars balanced forty-six lower first molars. 
 
Fig. 76. 
 
 Fig. 77- 
 
 Fig. 74* (Par. 96).— Left Lower First Molar, Occlusal Surface, of typical 
 form, a, Mesio-buccal ctisp; h, disto-buccal cusp; c, mesio-lingual cusp; d, disto- 
 lingual cusp; e, distal cusp; f, mesial marginal ridge; g, distal marginal ridge; h, 
 mesio-bticcal triangular ridge; i, disto-buccal triangular ridge; k, disto-Iingual tri- 
 angular ridge; /, mesio-lingual triangular ridge; m, distal triangular ridge; ;;, 
 mesial groove; 0, buccal groove; p, disto-buccal groove; r, distal groove; s, lingual 
 groove. 
 
 Fig. 7S* (Par. 96).— Right Lower First Molar, Occlusal Surface, a, 
 Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual 
 cusp; e, distal cusp; f, mesial marginal ridge; g, distal marginal ridge; h, mesial 
 triangular ridge; i, disto-buccal triangular ridge; k, mesio-lingual triangular ridge; 
 /, disto-lingual triangular ridge; ;;, mesial groove; 0, buccal groove; p, disto-buccal 
 groove; r, distal groove; s, lingual groove; t, mesio-buccal triangular groove. 
 
 Pig. 76* (Par. i04).^LErT Lower First Molar, Buccal Surface, a, ]Mesio- 
 buccal cusp; b, disto-buccal cusp; c, distal cusp; d, bucco-gingival ridge; e, buccal 
 pit, /, gingival line; ^, mesial root ; /;, distal root; /, buccal groove; k, disto-buccal 
 groove. 
 
 Fig. yy* (Par. 104). — Left Lower First Molar, Buccal Surface, with 
 prominent cusps. Reference the same as for Fig. 76. 
 
 *IIlustration, i>^ diameters. 
 7 
 
THE LOWER FIRST MOLAR. 8 1 
 
 98. The occlusal surface has five developmental 
 grooves (Figs. 74 and 75) — the mesial, buccal, disto-buccal, 
 lingual, and distal — which divide it into five developmental 
 parts, or lobes. These are the mesio-buccal (a), disto-buccal 
 (b), mesio-lingual (c), disto-lingual (d), and distal (^) lobes; 
 each bearing a cusp of the same name. ^The mesial groove 
 ~Xn)' runs from the central fossa over the mesial marginal ridge 
 to the mesial surface. On the mesial marginal ridge it is usu- 
 ally a fine line which is soon obliterated by wear. Occasion- 
 ally, this is divided into two branches, with a small tubercle on 
 the mesial marginal ridge between them (Fig. 74, /). In many 
 examples there is a supplemental groove which rises from the 
 mesial groove at about the center of its length, and runs toward 
 the mesio-buccal angle. This is the mesio-buccal triangular 
 groove (Fig. 75, i^). It divides the mesial marginal ridge from 
 the triangular ridge of the mesio-buccal cusp. More rarely 
 there is also a similar groove running toward the mesio-lingual 
 cusp. When these are deep, they form a mesial supplemental 
 fossa (Fig. 75, t). The buccal groove (0) runs in a deep 
 sulcus from the central pit to, and over, the buccal marginal 
 ridge to the buccal surface, and divides the mesio-buccal from 
 the disto-buccal cusp. The disto-buccal groove (p) also 
 runs bucco-distally from the central pit over the buccal ridge, 
 more or less near the distal angle, as the distal cusp is large or 
 small. It divides the disto-buccal lobe from the distal. The 
 lingual groove (s) runs from the central pit in a deep sulcus 
 to, and over, the lingual marginal ridge onto the lingual sur- 
 face, and divides the two lingual lobes. The distal groove 
 (r) runs distally over the distal marginal ridge, and divides the 
 disto-lingual lobe from the distal. Frequently this groove can 
 be traced some distance toward the gingival line on the distal 
 surface. The mesial and distal grooves form a line traversing 
 the whole extent of the occlusal surface, from mesial to distal, 
 in the center of which a V-shaped deflection is formed with its 
 point to the lingual, the base receiving the point of the triangu- 
 lar ridge (i) of the disto-buccal cusp. 
 
82 THE LOWER FIRST MOLAR. 
 
 99. In most examples the central fossa occupies all 
 the occlusal surface within the circle of the summit of the mar- 
 ginal ridges, though, occasionally, one or more supplemental 
 fossae are divided from it by high triangular ridges running 
 down from the cusps (Fig. 75, h, k). The surface of the fossa 
 is made irregular in most of these teeth by deep sulci on the 
 lines of the grooves, separating the cusps and triangular ridges. 
 
 100. The occlusal surface of the lower first molar has 
 five cusps, one on each side of the five lobes or three on the 
 buccal marginal, and two on the lingual marginal ridge.* 
 These cusps are formed by the grooves previously described 
 (Par. 98), which pass over the ridges in depressions of variable 
 depth, thus subdividing the crests of the ridges into obtuse ele- 
 vations. Usually, these are not so high and prominent as the 
 cusps of the upper molars. The mesio-buccal (Figs. 74 and 
 75, a) is the largest and strongest of the buccal cusps, and oc- 
 cupies rather more than one-third of the buccal marginal ridge. 
 From its crest a triangular ridge {h) runs down centrally to the 
 junction of the mesial and buccal grooves, and is divided from 
 a similar triangular ridge from the mesio-lingual cusp, by the 
 mesial groove. When these two ridges are high, they form, in 
 conjunction with triangular grooves between them and the 
 mesio-marginal ridge, a mesial supplemental fossa. The disto- 
 buccal cusp {b) is of less extent from mesial to distal, but has 
 a longer triangular ridge, though not so high, which ends in 
 the point of the V-shaped deflection of the mesial and distal 
 grooves, or at their junction. 
 
 loi. The lingual cusps {c, d) are about equal in size 
 and height (perhaps the mesial is a little the higher on the 
 average). They have strong triangular ridges {k, I) which 
 terminate in the angles formed by the junction of the lingual 
 groove with the mesial and distal grooves in the central pit. 
 
 102. The distal cusp {e) occupies the distal portion of 
 the buccal ridge, and forms the disto-buccal angle of the 
 
 * In some rare cases lower first molars have but four cusps, and 
 then the tooth is like the lower second molar. (Pars. 109, no.) 
 
THE LOWER FIRST MOLAR. 83 
 
 occlusal surface.! It is the distinguishing mark of the lower 
 first molar, being but very rarely absent in that tooth, and 
 never present in the lower second molar. It is the smallest 
 of the five cusps, and varies most in its^ relative size. 1 In some 
 examples it is almost or quite as large as the ciisto-buccal 
 cusp. In others, especially in small and poorly developed 
 teeth, it may be reduced to a mere tubercle, occupying the 
 buccal portion of the distal marginal ridge and the immediate 
 disto-buccal angle. The central incline of this cusp is com- 
 monly nearly flat, but occasionally has a rounded crest. It 
 ends in a point at the junction of the distal and disto-buccal 
 grooves. 
 
 103. In this tooth there is often a deep pit at the junc- 
 tion of the mesial, distal, and lingual grooves. Less fre- 
 quently there is also a pit at the junction of the mesial and 
 buccal grooves, and at the junction of the distal and disto- 
 buccal grooves. The grooves are often fissured for a short 
 distance from the pits, especially in the deeply sulcate lingual 
 groove. In some very poorly developed teeth fissures may 
 be found in any part of the grooves. 
 
 104. The buccal surface of the lower first molar (Figs. 
 76 and ']'/^, when seen at right angles with the long axis of the 
 tooth, is irregularly trapezoidal in form, with the occlusal 
 margin about two-sevenths- longer than the gingival. The 
 mesial and distal margins converge toward the gingival, and 
 the angles with the occlusal surface are about equally acute. 
 The occlusal margin is broken into three elevations, or cusps, 
 by the buccal and disto-buccal grooves. The gingival line is 
 straight, or slightly curved, with the concavity toward the 
 occlusal surface. The mesial and the distal lines are slightly 
 convex. The buccal surface is convex in all directions ; but 
 the line of convexity from mesial to distal is broken toward 
 the occlusal margin by the buccal and disto-buccal grooves, 
 which pass over from the occlusal surface^^The buccal 
 groove (i) is usually a little to the mesial of the central line 
 of the surface, and often ends in a deep pit ((?), about half-way 
 
84 THE LOWER FIRST MOLAR. 
 
 from the occlusal to the gingival margin. Exceptionally, this 
 groove is continued to the bifurcation of the root. / The disto- 
 buccal groove (k) is near the disto-buccal angle, and its 
 course is toward the gingival line, with a distal inclination. 
 It is usually lost to sight by becoming shallower, but in some 
 examples it may be traced to the gingival line. The enamel 
 terminates in a marked inclination toward the gingival line, 
 fonning the bucco-gingival ridge. 
 
 105. The lingual surface of this tooth (Figs. 78 and 79) 
 is slightly convex in all directions. It forms a fairly sharp 
 angle with the occlusal surface, but is rounded away toward 
 the mesial and distal surfaces. On account of the lingual 
 convergence of the mesial and distal surfaces, the lingual 
 surface is much shorter mesio-distally than the buccal. The 
 occlusal margin is deeply notched by the passage of the lingual 
 groove (i), which usually terminates near the center of the 
 surface by becoming shallower. 
 
 106. The mesial surface (Fig. 80) is very irregular in 
 outline, and often the occlusal margin is deeply concave. 
 The gingival curvature is generally marked, and the buccal 
 and lingual marginal lines convex. The buccal margin of 
 this surface is more convex than the lingual, and its curva- 
 ture is at such an incline as to render the gingival marginal 
 line much longer than the occlusal. The surface is slightly 
 convex, though almost flat ; but, in the central portion, near 
 the gingival line, it is sometimes slightly concave from buccal 
 to lingual. It is rounded away toward the mesio-buccal and 
 mesio-lingual angles. With the occlusal surface it forms a 
 sharp angle in the central portion, but this is rounded in its 
 buccal and lingual portions. In the direction of the long 
 axis of the tooth, there is usually a concavity at the junction 
 of the enamel and cementum. 
 
 107. The distal surface (Fig. 81) is smoothly convex 
 from buccal to lingual. From the occlusal surface to the 
 gingival line it is straight or slightly convex, but forms a 
 considerable concavity at the junction of the crown with the 
 
Fig. 78. 
 
 Fig. 79. 
 
 Fig. 80. 
 
 Fig. 82. 
 
 Fig. 78* (Par. 105). — Left Lower First Molar, Lingual Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; c, distal cusp; d, mesio-Iingual cusp; e, disto- 
 lingual cusp; /, /, gingival line; g, mesial root; h, distal root; the roots are 
 spread wide apart; i, lingual groove. 
 
 Fig. 79* (Par. 105). — Left Lower First Molar, Lingual Surface. This tooth 
 has prominent cusps, and the roots are straight and close together. References the 
 same as for Fig. 78. 
 
 Fig. 80* (Par. 106). — Left Lower First Molar, Mesial Surface, c, Mesio- 
 buccal cusp; d, mesio-lingual cusp; e, mesial surface, point of concavity; /, f, 
 gingival line ; g, mesial root with broad groove. 
 
 Fig. 81* (PsiY. 107). — Left Lower First Molar, Distal Surface. The cusps 
 are very prominent, a, Mesio-buccal cusp; b, disto-buccal cusp; c, distal cusp; d, 
 mesio-lingual cusp; e, disto-lingual cusp; /, gingival line; g, mesial root; h, distal 
 root. 
 
 Fig. 82* (Par. 108). — Lower First Molar, with three roots. 
 
 *IIlustration, ij^ diameters. 
 
THE LOWER SECOND MOLAR. S? 
 
 root, which occasionally forms a sharp angle, but generally 
 is well rounded. The occlusal margin is often deeply notched 
 by the distal groove. In a few examples the disto-buccal 
 groove is deep after passing over the marginal ridge, and in 
 its distal inclination forms a slight concavity near the disto- 
 buccal angle. 
 
 io8. The root of the lower first molar is divided into 
 two prongs (Figs. 76 to 82), and this division is usually close 
 to the crown, closer than in any other tooth in the mouth. 
 The mesial root (g) inclines first to the mesial, and then 
 curves regularly toward the distal. It is broad from buccal 
 to lingual, and is much thinned from mesial to distal, s o that 
 ift~er0s«-"seetions it measures double as much one way as the 
 other, yit is usually slightly concave on both mesial and distal 
 surfaces, and tapers regularly, but not rapidly, from the bifur- 
 cation to the apex, and ends in a flattened but well-rounded 
 point. The distal root (h) inclines to the distal at first, and 
 afterward is nearly or quite straight. In some examples the 
 apical half curves to the distal, but more often toward the 
 mesial, so that the apexes of the two roots are inclined toward 
 each other. It is narrower from buccal to lingual than the 
 mesial root, and more nearly round, being but rarely concave 
 or grooved on either mesial or distal surface. It tapers quite 
 regularly, and more nearly to a point than the mesial root, 
 though the apex is generally well rounded. The form of the 
 root is regular, rarely deviating much from its type. Occa- 
 sionally, however, the division of the root is incomplete. | The 
 mesial root is occasionally divided, giving the tooth three 
 roots (Fig. 82) ; and I have seen a few in which the distal root 
 was divided also, giving four roots. 
 
 THE LOWER SECOND MOLAR. 
 
 109. The most characteristic difference between the 
 lower first and second molars is the absence of the fifth lobe 
 in the second,* and the general change of form which this 
 absence implies ; the other parts of the tooth being similar. 
 
 * Since the publication of the third edition of this work three cases 
 have been reported to me, two of which were accompanied by plaster 
 casts in which di^al lobes with cusps were observed upon the lower 
 second molars. In all of them the cusps were small, though fairly 
 well formed. These are certainly very rare cases. 
 
THE LOWER SECOND MOLAR. 
 
 iio. When the occlusal surface is seen in a Hne with 
 the long axis of the tooth (Fig. 83), the outline of the crown 
 is nearly a parallelogram, with angles rounded and the lines 
 slightly convex, the buccal most. The summits of the mar- 
 ginal ridges are close to the mesial, distal, and lingual mar- 
 gins, while the buccal is carried over toward the lingual by 
 the inclination of the buccal surface. The central inclines of 
 the marginal ridges form a deep central fossa, in the center 
 of which there is usually a deep pit. 
 
 111, There are four developmental grooves, all aris- 
 ing from the central pit. The mesial groove (/) runs to the 
 mesial margin and crosses the mesial marginal ridge as a fine 
 line, which is often obliterated by wear. The distal groove 
 (0) runs in a similar way to the distal surface. These two 
 grooves divide the occlusal surface from mesial to distal, and 
 centrally, between the summits of the buccal and lingual 
 marginal ridges. The buccal groove (m) runs from the cen- 
 tral pit to the buccal margin, and over it to the buccal surface, 
 dividing the buccal ridge into two buccal cusps, while the 
 lingual groove (n) runs to and over the lingual marginal 
 ridge, dividing it also into two lingual cusps. The two divide 
 the tooth from buccal to lingual, into nearly equal parts. The 
 mesial portion is usually slightly the larger. The four grooves 
 form a cross through the occlusal surface, dividing it into 
 four lobes, or developmental parts, on each of which there 
 is a cusp and a triangular ridge, j In some examples the 
 
 "grooveT^do^nor exactly meet at the central pit. The lingual 
 may rise to the mesial of the buccal, or vice versa; or, a similar 
 variation may occur in the central ends of the mesial and distal, 
 causing irregularity of the contour of the central fossa. Occa- 
 sionally, the lobes are of unequal size, or the cusps are 
 unequally developed, giving rise to imperfect forms (Fig. 84). 
 
 112. On the average, the cusps of the lower second 
 molar are higher and more pointed, and the triangular ridges 
 are more prominent than in the first molar. The mesio-buccal 
 
Fig. 87. 
 
 
 Fig-. 86. 
 
 Fig. 89. 
 
 /Sr— 
 
 Fig. 83* (Par. iio).^Right Lower Second Molar, Occlusal Surface, of 
 typical form, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; rf, 
 disto-lingual cusp; e, mesial marginal ridge; /, distal marginal ridge; g, mesio- 
 buccal triangular ridge; h, disto-buccal triangular ridge; /, mesio-lingual triangular 
 ridge; k, disto-lingual triangular ridge; /, mesial groove; m, buccal groove; n, 
 lingual groove; 0, distal groove. 
 
 Fig. 84* (Par. 113). — Right Lower Second Molar, Occlusal Surface, of im- 
 perfect form, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; li, 
 disto-lingual cusp; e, mesial marginal ridge; f, distal rnarginal ridge; g,_ mesio- 
 buccal triangular ridge; h, disto-buccal triangular ridge; i, mesio-lingual triangular 
 ridge; k, disto-lingual triangular ridge; /, mesial groove; m, buccal groove; n, 
 lingual groove; 0, distal groove. 
 
 Fig. 85* (Par. 115). — Left Lower Second Molar, Buccal Surface, a, Mesio- 
 buccal cusp; b, disto-buccal cusp; c, buccal groove; d, buccal pit; /, gingival line; 
 g, mesial root; h, distal root. 
 
 Fig. 86* (Par. 116). — Left Lower Second Molar, Lingual Surface, a, 
 Mesio-buccal cusp; b, disto-buccal cusp; c. mesio-lingual cusp; d, disto-lingual 
 cusp-; e, lingual groove; /, gingival line; c, mesial root; h, distal root. 
 
 Fig. 87* (Par. 117). — Left Lower Second Molar, Mesial Surface, a, Mesio- 
 buccal cusp; c, mesio-lingual-cusp; d, point of proximal contact of mesial surface; 
 /, gingival line; g, mesial root. 
 
 Fig. 88* (Par. 118). — Left Lower Second Molar, Distal Surface, a, Mesio- 
 buccal cusp; h, disto-buccal cusp; c, mesio-lingual cusp; d, disto-lingual cusp; e, 
 point of proximate contact of the distal surface; /, gingival line; h, distal root. 
 
 Fig. 89* (Par. ii9).^Right Lower Second Molar, Lingual Surface. The 
 roots are curved very much to the distal. 
 
 •Illustration, iJ/< diameters. 
 
THE LOWER SECOND MOLAR. QI 
 
 ^ and mesio-lingual cusps are generally a little larger than the 
 disto-buccal and disto-lingual ; also, the mesio-buccal and 
 mesio-lingual triangular ridges (Fig. 83, g, i) are usually more 
 prominent. The crests of these ridges do not run directly 
 toward the central pit, but the two mesial ones meet mesially 
 of the central pit, while the two distal meet distally of it. 
 When they are high, they form transverse ridges by their 
 junction, which separate a mesial and a distal supplemental 
 fossa from the central fossa. When this occurs, there are 
 usually triangular supplemental grooves deflected from the 
 mesial and distal grooves, to the mesial and distal of the trian- 
 gular ridges, which run toward the angles of the tooth and 
 separate the triangular from the marginal ridges, widening 
 and deepening the supplemental fossae. A deep pit is often 
 found at the point where these triangular grooves arise from 
 the principal grooves. Supplemental fossse occur much more 
 frequently, or are more pronounced, in the mesial than in the 
 distal portion of the tooth, but in many examples the trian- 
 gular ridges are so widely divided by sulcate, mesial and distal 
 grooves that no supplemental fossae are seen. 
 
 113. In some examples the lower second molar presents 
 dififerences in the comparative size of its lobes, and the 
 grooves may be deflected from their normal course. Occa- 
 sionally, the distal groove is divided, and passes over the distal 
 marginal ridge in two divisions, with a small tubercle between 
 them. In poorly developed teeth there may be many supple- 
 mental grooves, or wrinkles, running from the developmental 
 grooves up onto the central inclines of the ridges and cusps. 
 
 114. Fissures occur oftenest near the central ends of 
 
 the grooves ; though they may appear in any part of their 
 length; and in poorly developed teeth the supplemental 
 grooves may be deeply fissured. 
 
 115. The buccal surface of the lower second molar 
 (Fig. 85) is convex in all directions, except that it is partially 
 divided into two sections, or ridges, by the buccal groove (c), 
 which runs over onto it from the occlusal surface. In many, 
 
92 
 
 THE LOWER THIRD MOLAR. 
 
 this groove ends near the center of the surface in a deep buccal 
 pit (d). This tooth has no disto-buccal groove. The mesial 
 and distal margins converge less toward the gingival line than 
 they do in the lower first molar. The gingival line is nearly 
 straight, and there is a strong inclination of the border of the 
 enamel toward it, giving the appearance of a gingival enamel 
 ridge. 
 
 ii6. The lingual surface (Fig. 86) is similar in all 
 points to that of the lower first molar {q. v., Par. 105) ; but, on 
 account of a much less convergence of the mesial and distal 
 surfaces toward the lingual, this surface is nearly as large as 
 the buccal surface. 
 
 117. The mesial surface (Fig. 87) of the lower second 
 molar is generally a little more convex than in the lower first 
 (q. v., Par. 106) ; but in other respects they are similar. 
 
 118. The distal surface (Fig. 88) differs from that of 
 the lower first molar in not having the distal protuberance 
 due to the fifth cusp. Its proximating point with the tooth 
 distal to it is usually central, or toward the lingual, instead of 
 the buccal margin, as in the lower first molar. This surface 
 is usually quite regularly and smoothly convex, and its gingival 
 line seldom shows any bucco-lingual curvature. 
 
 119. The roots of the lower second molar (Figs. 85 to 
 89) are similar to those of the first molar; but the divisions 
 are much less spread and less grooved on the mesial and distal 
 sides. In many examples there is but a single root, which is 
 deeply grooved on its buccal and lingual sides, marking out the 
 divisions. The root is much more irregular in form than in the 
 lower first molar, and is often much curved distally (Fig. 89) 
 or otherwise distorted. 
 
 THE LOWER THIRD MOLAR. 
 
 120. The lower third molar, called also the wisdom 
 tooth, or Dens Sapientia, is the eighth from the median line, 
 and the last tooth in the arch. It proximates the lower 
 second molar by its mesial surface. The tooth has two typi- 
 
THE LOWER THIRD MOLAR. 93 
 
 xal forms; the one is a four-cusped tooth, similar to the lower 
 second molar (Fig. 83) ; the other a five-cusped tooth, similar 
 to the lower first molar (Fig. 75) ; but there are great varia- 
 tions from both of these. ] Indeed, within the observation of 
 
 "the author the form of this tooth is oftener distorted than any 
 other. 
 
 121. The four-lobed tooth is the more common form, 
 and, when well developed, the occlusal surface is similar to 
 that of the lower second molar. A supplemental fossa is often 
 seen, formed by the prominence of the mesio-buccal and 
 mesio-lingual triangular ridges ; but in the distal portion of 
 the crown such a fossa rarely appears. Indeed, in the four- 
 cusped lower third molars, the distal lobes are generally much 
 smaller than the mesial lobes. 
 
 122. The course of the grooves is often much distorted, 
 so that their central ends fail to proximate, as in Fig -.-90,-ai^ 
 othef^wise. This renders the form of the central fossa ex- 
 tremely irregular. Or the principal grooves may be so con- 
 fused among a number of supplemental grooves that the real 
 dividing lines of the lobes can scarcely be made out /(Fig. 91). 
 In many of these, some "oTfhe' supplemental grooves run over 
 the. marginal ridges, corrugating them, or dividing them into 
 several imperfect cusps. Occasionally the Vnargirial ridges 
 are nearly equal in height all around the margin of thte central 
 fossa, and the enamel surface of the latter r^ covered with 
 small wrinkles, some of which may be deeply fissured. 
 
 123. In some instances the lower third molar is very 
 
 large, and in these the ridges may be subdivided into six, 
 seven, or eight cusps, and as many fairly distinct lobes ; or, 
 one or more supplemental ridges may appear within the 
 limits of the central fossa surrounded by grooves, which divide 
 t'hem from other parts of the crown fEig\_92). Such teeth 
 are usually poorly fonned, and the grooves deeply fissured. 
 
 124. The five-lobed lower third molars are very large 
 teeth, larger than the second molars, and very regularly 
 formed. The distal lobe is placed further to the distal and 
 
94 THE DECIDUOUS TEETH. 
 
 lingual, and the buccal surface is more rounded than in the 
 first molars. This form is bilateral and hereditary. 
 
 125. The buccal surface of the lower third molar (Figs. 
 )3> 94' 95) is usually more convex than in the other lower 
 
 molars, but otherwise of the same form. If four-lobed this 
 tooth has the same grooves and pits as the lower second ; if 
 five-lobed, it has the markings of the lower first molars. 
 
 126. The mesial, lingual, and distal surfaces corre- 
 spond with those of the other lower molars, only rather more 
 rounded ; especially the distal, which is often nearly a true 
 circle from buccal to lingual. 
 
 127. The root of the lower third molar (Figs. 93, 94, 
 95), as compared with its crown, is usually much smaller 
 than in the other lower molars. It may be single, or divided 
 into two or more prongs, the tendency being to the forma- 
 tion of two roots, the same as in the other lower molars ; and 
 much the greater number have the root in this form, though 
 the single root is common, and three roots (the mesial being 
 divided) are not rare. The root, or roots, of this tooth usually 
 curve distally, sometimes very much, and are otherwise dis- 
 torted. In extracting, this inclination of the roots should be 
 kept in mind. 
 
 THE DECIDUOUS TEETH. 
 
 128. These are the teeth of early childhood, and serve 
 for mastication till the maxillary bones are sufficiently devel- 
 oped to accommodate the permanent, the larger teeth of adult 
 age. They are then removed by absorption of their roots, 
 which allows their crowns to fall away. Hence they are often 
 called temporary teeth. The shedding process begins about 
 the seventh year, and is completed at from the twelfth to the 
 fourteenth, the succedaneous teeth taking the places of the 
 deciduous. There are twenty deciduous teeth, ten in each 
 jaw, namely: two central incisors, two lateral incisors, 
 two cuspids, and four molars. This may be expressed by 
 the following formula : 
 
 1 1 C i M I- = 20 
 
Fig. 91. 
 
 FiST- 93- 
 
 Fig. 94. 
 
 
 Fig- 95- 
 
 Y. 
 
 Fig. 90* (Par. 122).— Left Lower Third Molar, Occlusal Surface, imperfect 
 form, a, Mesio-buccal cusp; b. disto-buccal cusp; c, mesio-lingual cusp; d, disto- 
 lingual cusp; e, mesial marginal ridge; /, distal marginal ridge; g, mesial groove, 
 h, buccal groove; i, lingual groove; /;, distal groove. The buccal and lingual 
 grooves do not meet in the central fossa as in regular forms. 
 
 Fig. 91* (Par. 122). — Lower Third Molar, Occlusal Surface, very imperfect 
 form, a, Mesio-buccal cusp; b, disto-buccal cusp; c, mesio-lingual cusp; d, disto- 
 lingual cusp; e, mesial marginal ridge; /, distal marginal ridge; g, mesial groove; 
 h, buccal groove; j, lingual groove; k, distal groove. Several of the grooves are 
 fissured and are irregular in form. 
 
 Fig. 92* (Par. 123). — Right Lower Third Molar, Occlusal Surface, very 
 large and irregular in form, a, Mesio-buccal cusp ; b, a very imperfect disto-buccal 
 cusp; c, mesio-lingual cusp, with a sharp triangular ridge, running very much to 
 the distal; d, disto-lingual cusp, standing very much to the mesial of its proper 
 position; e, f, a large supplemental ridge, occupying the middle portion of the cen- 
 tral fossa; g, mesial marginal ridge; /;, distal marginal ridge; i, mesial groove, 
 deeply fissured and with supplemental grooves, also fissured, extending to the 
 labial and lingual, forming a supplemental mesial fossa; k, buccal groove; /, lingual 
 groove; m, n, deep fissure on either side of the supplemental ridge. There are a 
 number of deep wrinkles running over the distal marginal ridges. 
 
 Fig. 93* (Par. 125).— Right Lower Third Molar, Buccal Surface, with five 
 cusps, a, Mesio-buccal cusp; b, disto-buccal cusp; c, buccal groove; d, buccal pit; 
 e, disto-buccal groove; /, distal cusp; g, gingival line; h, mesial root; 1, distal root. 
 In this tooth the distal root is the larger, and the two come together at their 
 apexes, each of which is unusual. 
 
 Fig. 94* (Par. 127). — Right Lower Third Molar, with the roots curved very 
 much to the distal. 
 
 Fig. 95* (Par. 127). — Left Lower Third Molar, Buccal Surface; three roots. 
 a, Mesio-buccal cusp; b, disto-buccal cusp; c, distal cusp; d, buccal groove; f, 
 gingival line; g, mesial root; /;, distal root; i, supernumerary root. 
 
 Illustration, ij.-^ diameters. 
 8 
 
THE DECIDUOUS TEETH. 97 
 
 There are no bicuspids in the diciduous set, and therefore 
 the deciduous first molars proximate directly with the decid- 
 uous cuspids. The bicuspids of the permanent set are sue- 
 cedaneous to the deciduous molars. 
 
 129. The incisors and cuspids of the deciduous set are 
 (Eigs,-96-1:o TOi) similar in form and lobal construction with 
 their succedaneous teeth, but the deciduous molars give place 
 to the permanent bicuspids, which are of very dissimilar 
 pattern. The deciduous second molars (Figs. 103, 105^, 
 both upper and lower, are of the same form and lobal con- 
 struction as the permanent first molars. The deciduous first 
 molars, upper and lower, have no similar teeth in the perma- 
 nent set. Their form and the arrangement of their lobes are 
 peculiar to themselves ; therefore, the crowns of these will be 
 separately described. (Pars,^x34-tCLj:.5o.) 
 
 130. Though the crowns of the temporary teeth are, 
 with the exceptions mentioned, of similar form and lobal con- 
 struction as the permanent, there are certain minor differences 
 which distinguish them. They are considerably smaller than 
 the corresponding permanent teeth. This reduction in size 
 includes the whole tooth, and is such that it leaves the general 
 proportions unchanged, except that the roots are proportion- 
 ally longer. 
 
 131. The deciduous teeth are, however, marked with a 
 much greater constriction at their necks. The enamel, 
 instead of thinning away to the gingival border as in the per- 
 manent teeth, retains its thickness almost to the gingival line 
 and terminates abruptly, leaving a sudden constriction of the 
 neck of the tooth. This varies in degree, but is common to 
 all of the deciduous teeth, and distinguishes them from the 
 permanent teeth. 
 
 132. The buccal and lingual surfaces of the deciduous 
 "molars are inclined toward the occlusal surface much more 
 
 than those of the permanent, so that the immediate occlusal 
 surface is narrow in proportion to the greatest bucco-Iingual 
 thickness of the crown. This gives the crown as seen in the 
 
98 UPPER FIRST DECIDUOUS MOLAR. 
 
 mouth the appearance of being very long from mesial to distal ; 
 though this characteristic is less marked in the upper than in 
 the lower deciduous molars (see Figs. 106 and 107). 
 
 133. The enamel of the deciduous teeth is usually 
 whiter than that of the permanent teeth, and they are probably 
 of coarser texture. The difference in color is often strongly 
 contrasted when some of the permanent teeth, as the central 
 incisors, have taken their places by the side of the remaining 
 temporary teeth. 
 
 UPPER FIRST DECIDUOUS MOLAR. 
 
 134. The occlusal surface of the upper first decidu- 
 ous molar (Fig. 107), when seen in the line of the long axis of 
 the tooth, presents an irregular quadrangular form in which 
 the buccal marginal line is the longest. I The— mesio-buccal 
 angle is acute, the mesio-lingual is obtuse, and both distal 
 angles are nearly right angles. The buccal margin is irregu- 
 larly convex, and the lingual margin regularly rounded. Both 
 the buccal and lingual surfaces are much inclined centrally, 
 or toward the occlusal surface. 
 
 135. This tooth has three lobes, divided by three 
 grooves. The mesial (a) and distal (&) grooves run from the 
 mesial to the distal margin in a deep sulcus, and divide the 
 lingual from the buccal lobes. Their junction is in a pit in 
 the central fossa. The buccal groove (c) rises from the same 
 pit, at the junction of the mesial and distal grooves, and runs 
 over the buccal marginal ridge to the buccal surface. This 
 groove is generally without a sulcus ; or, at most, there is but 
 a slight furrow. 
 
 136. The buccal marginal ridge is a high cutting edge 
 which rounds up from the mesio-buccal angle of the occlusal 
 surface and runs to the distal and buccal till it reaches the 
 point of the mesio-buccal cusp (d). Its direction is then to 
 the distal, descending slightly to the buccal groove, then hori- 
 zontally to the disto-buccal angle to join the distal marginal 
 ridge, the latter portion forming a small disto-buccal cusp (e). 
 
Fig. 96. 
 
 Fig- 97- 
 
 Fig:.< 
 
 Fig. 103. 
 
 Fig. 99. 
 
 Fig. 100. 
 
 Fig loi. 
 
 Fig. 104. 
 
 Fig. 105. 
 
 Fig. 106. 
 
 Fig. 107. 
 
 Fig. 96* (Par. 129).— Deciduous Upper Central Incisor. 
 
 Fig. 97* (Par. 129). — Deciduous Upper Lateral Incisor. 
 
 Fig. 98* (Par. 129). — Deciduous Upper Cuspid. 
 
 Fig. 99* (Par. 129).— Deciduous Lower Lateral Incisor. 
 
 Fig. 100* (Par. 129). — Deciduous Lower Lateral Incisor. 
 
 Fig. ioi* (Par. 129). — -Deciduous Lower Cuspid. 
 
 Fig. 102* (Par. 138).— Left Upper First Deciduous Molar, Buccal Surface 
 a, Bucco-gingival ridge; b, mesio-buccal cusp; c, disto-buccal cusp; d, buccal 
 ridge ; e, buccal groove. 
 
 Fig. 103* (Par. 129).— Left Upper Second Deciduous Molar. 
 
 Fig. 104* (Par. 148).— Left Lower First Deciduous Molar, Buccal Surface. 
 a, Bucco-gingival ridge; b, mesio-buccal cusp; c, disto-buccal cusp; d, buccal ridge; 
 e, buccal groove. 
 
 Fig. 105* (Par. 129).— Left Lower Second Deciduous Molar, Buccal Sur- 
 face. 
 
 Fig. 106* (Par. 141). — Lower First and Second Deciduous Molar, Oc- 
 clusal Surfaces. The lobes and grooves of the lower second deciduous molar are 
 the same as those of the permanent lower first molar, Fig. 75. The lower decidu- 
 ous first molar has four lobes, a, Mesial groove; b, buccal groove; c, lingual 
 groove; d, distal groove; e, mesio-buccal cusp; /, disto-buccal cusp; g, mesio- 
 lingual cusp; li, disto-lingual cusp; i, mesial fossa. 
 
 Fig. 107* (Par. 134). — Left Upper First and Second Deciduous Molars. 
 The second deciduous molar has its grooves and lobes in the same form as those 
 of the first permanent molar. Fig. 54. The upper first deciduous molar has but 
 three cusps, a, Mesial groove; b, distal groove; c, buccal groove; d, mesio-buccal 
 cusp; e, disto-buccal cusp; f, lingual cusp. 
 
 *Illustration, lyi diameters. 
 
>r- 
 
 LOWER FIRST DECIDUOUS MOLAR. lOI 
 
 In unworn teeth, the buccal groove causes a marked, but 
 slight, depression where it crosses the ridge, breaking it into 
 two cusps ; the mesial being the larger and more pointed. This 
 division is generally defaced very early by wear, so that the 
 ridge presents an almost straight rounded edge. 
 
 137. The lingual cusp (/) is in the form of an elevated 
 crescentic edge with its convexity to the lingual, which runs 
 from the mesial termination of the mesial groove (o) to the 
 distal termination of the distal groove (b). The central and 
 the lingual inclines of this cusp are nearly equal slopes, while 
 the buccal incline toward the buccal marginal ridge is less 
 abrupt than the central. The mesial and distal marginal 
 ridges are not marked by more than a very slight thickening 
 of the enamel, and are cut through by the mesial and distal 
 grooves. 
 
 "^ 138. The buccal surface (Fig. 102) is remarkable for its 
 bucco-gingival ridge (a), which stands boldly out from the 
 gingival line (from one to three millimeters and extends from 
 the mesio-buccal to the disto-buccal angle of the tooth. At 
 the mesio-buccal angle it terminates abruptly in a marked 
 prominence, and diminishes gradually as it passes to the disto- 
 buccal angle. 
 
 139. From the summit of the bucco-gingival ridge to 
 the summit of the buccal marginal ridge, or the mesio-buccal 
 cusp, is nearly a flat surface, except a slight depression along 
 the buccal groove. In many examples there is a slight con- 
 cavity extending from mesial to distal along the occlusal mar- 
 gin of the bucco-gingival ridge, and from the point of the 
 mesio-buccal cusp a strong ridge runs to the mesio-buccal 
 prominence of the bucco-gingival ridge. 
 
 140. The mesial and distal surfaces are quite smoothly 
 flattened. The lingual surface is convex. The neck presents 
 the characteristic constriction common to deciduous teeth. 
 
 LOWER FIRST DECIDUOUS MOLAR. 
 
 t2^i. The occlusal surface of the lower first deciduous 
 
I02 LOWER FIRST DECIDUOUS MOLAR. 
 
 molar (Fig. io6), when viewed in a line with the long axis of 
 the tooth, presents the outline of a parallelogram, modified by 
 the rounding of its angles and more or less convexity of its 
 lines. In many, the distal portion is broader than the mesial, 
 giving the tooth an ovoid outline. There are two fossae. 
 The principal fossa occupies nearly three-fourths of the distal 
 portion of the surface, while the small mesial fossa occupies the 
 immediate mesial portion. 
 
 142. The tooth has four lobes of irregular form, divided 
 by four grooves. These grooves all run from the principal 
 fossa. The mesial groove (a, a) rises from the central pit 
 and runs to the mesial, passing over the transverse ridge into 
 the mesial fossa, where it is deflected sharply to the lingual, 
 passing over the marginal ridge near the mesio-linguo-occlusal 
 angle. This groove varies considerably in its course in dif- 
 ferent examples. In the principle fossa it usually inclines to 
 the buccal and then toward the lingual, but there is generally 
 an angle at the origin of the buccal groove. The buccal 
 groove (b) rises from the mesial groove, some distance to the 
 mesial of the pit, and runs over the buccal ridge on to the buc- 
 cal surface, in a slight sulcus, dividing the buccal marginal 
 ridge into two cusps, the mesio- and disto-buccal. Its position 
 determines the relative size of the buccal lobes. The lingual 
 groove (c) runs from the central pit over the lingual marginal 
 ridge on to the lingual surface, and is deeply sulcate on the cen- 
 tral incline of the ridge. The distal groove (d) arises from 
 the central pit and runs over the distal marginal ridge nearly 
 centrally, to the distal surface. It is often deflected to the 
 buccal in the first part of its course by the point of the disto- 
 lingual triangular ridge. 
 
 143. This tooth has four cusps corresponding with the 
 four lobes. The mesio-buccal lobe (e) is very irregular in its 
 outline. It forms the entire mesial marginal ridge, and from 
 one-third to three-fourths of the slopes of the mesial fossa. 
 The mesial marginal ridge is usually high in young, un- 
 worn, teeth. It is curved, and from the mesio-bucco-occlusal 
 
LOWER FIRST DECIDUOUS MOLAR. 103 
 
 angle of the tooth it becomes the buccal marginal ridge, and 
 rises to the distal to form the point of the mesio-buccal cusp 
 (e). From the point of the cusp it falls away to the distal and 
 buccal to the buccal groove. A prominent triangular ridge 
 descends from this cusp to the lingual and distal, and joins a 
 similar triangular ridge from the mesio-lingual cusp (g) to 
 form the transverse ridge, thus dividing the mesial from the 
 principal fossa. Exceptionally, a deep sulcus divides these 
 triangular ridges and connects the fossae. From the buccal 
 groove, the buccal marginal ridge passes almost directly to the 
 disto-bucco-occlusal angle where it joins the distal marginal 
 ridge. In the central portion it rises* slightly to form the low 
 disto-buccal cusp (/). The triangular ridge from this cusp is 
 usually low, or wanting. 
 
 144. The lingual marginal ridge, (g, h) rises ab- 
 ruptly from the mesial groove to the summit of the mesio-lin- 
 gual cusp (o-),and then falls away toward the distal and lingual 
 to the lingual groove. In most specimens, in unworn teeth, 
 the mesio-lingual cusp is sharp, and its point is carried by the 
 lingual incline far toward the central line of the tooth, so much 
 so as to be in marked contrast with the general form of the 
 lingual cusps of the lower molars. From its apex a triangular 
 ridge descends to join that from the mesio-buccal cusp in 
 forming the transverse ridge. From the lingual groove, the 
 lingual marginal ridge rises to the point of the disto-lingual 
 cusp {h) and then falls away in a curve to form the distal mar- 
 ginal ridge. This cusp is generally rather low, but varies 
 much in these teeth. In some cases there is a sharp triangular 
 ridge descending into the central fossa, but more generally this 
 ridge is slight. 
 
 145. The distal marginal ridge is usually made to ap- 
 pear prominent by the depth of the principal fossa. It is 
 crossed near its center by the distal groove. 
 
 146. The principal fossa is generally deep and well 
 rounded. The distal triangular ridges, the only ones descend- 
 ing into this fossa, are generally not prominent, but occasion- 
 
I04 LOWER FIRST DECIDUOUS MOLAR. 
 
 ally they are sufficiently so to render the fossa very angular. 
 I have observed many in which the enamel in this fossa was 
 very imperfect and the bottom of the fossa broad and rough. 
 
 147. The mesial fossa (^) is usually sharp and deep, 
 with smooth inclines, and has a central pit that is frequently the 
 seat of caries. 
 
 148. The buccal surface of the lower first deciduous 
 molar (Fig. 104) is remarkable for its prominent bucco-gin- 
 gival ridge (a), which runs from the mesial to the distal mar- 
 gin and stands out prominently over the junction of the crown 
 with the root. From mesial to distal, this ridge slopes toward 
 the occlusal surface, making the crown longer at the mesio- 
 buccal angle than at the disto-buccal. From this ridge the 
 surface slopes rapidly toward the occlusal margin, and more 
 rapidly at the mesial than the distal portion. From the mesio- 
 buccal cusp a strong ridge of enamel runs to the more promi- 
 nent portion of the bucco-gingival ridge near the mesio-buccal 
 angle of the tooth. Otherwise this surface is nearly flat. The 
 lingual surface is usually well rounded, but is broken toward 
 the occlusal surface by the prominence of the mesio-lingual 
 cusp, and the sulcus of the lingual groove. 
 
 149. The mesial and distal surfaces are slightly 
 rounded. The disto-buccal and disto-lingual angles of the 
 tooth are about equal in prominence, but the mesio-buccal and 
 mesio-lingual angles are very unequal. The mesial surface 
 slopes rapidly to the lingual, making the lingual surface^, much 
 shorter, mesio-distally, than the buccal. The mesio-buccal 
 angle is acute and prominent, while the mesio-lingual is very 
 obtuse and rounded. 
 
 150. The root of this molar is divided into two prongs, 
 which are spread widely apart. They are thin from mesial to 
 distal, and slightly grooved ; and, from buccal to lingual, broad. 
 They taper regularly to broad, flat apexes, which are occasion- 
 ally bifurcated a short distance. 
 
 151. The roots of the deciduous teeth are the same in 
 number and greneral characteristics as in the teeth of the same 
 
THE PULP CHAMBER. IO5 
 
 denomination in the permanent set, except that those of the 
 molars are more divergent. This spreading of the roots ac- 
 commodates the crowns of the permanent bicuspids, which are 
 developed between the roots of the deciduous molars. ^ Those 
 of the Tower jaw are thin from mesial to distal, broad from 
 buccal to lingual, and grooved along their flattened sides. The 
 mesial and distal roots of the upper deciduous molars are also 
 thin, grooved, and widely divergent. The lingual root stands 
 boldly to the lingual, forming a wide space between the three, 
 for the crowns of the upper bicuspids. In many examples the 
 lingual and distal roots are joined by broad thin connections 
 for the greater part of their length. 
 
 THE PULP CHAMBER. 
 
 _. 152. Every tooth has a cavity in the center of the 
 crown^ and one or more canals extending through the long 
 axis of the root, or roots, to the apex. This cavity contains a 
 tissue composed of cellular elements imbedded in a semi- 
 gelatinous matrix, filling every part of the space, and is richly 
 supplied with blood-vessels and nerves. This is known as the 
 pulp of the tooth.* 
 
 153. The central cavity in the tooth is usually divided 
 into a crown, or coronal portion, and a root portion. Its parts 
 are familiarly known as the pulp chamber (crown cavity), 
 and root canal, or root canals. The pulp chamber is com- 
 paratively large, and the root canals are small, tapering from 
 the pulp chamber to a minute opening at the apex of the root, 
 known as the apical foramen. In those teeth that have 
 prominent cusps, as the bicuspids and molars, there is a pro- 
 longation of the pulp toward the point of each cusp. These 
 are known as the horns of the pulp ; and the prolongations of 
 the chamber are designated the horns of the pulp chamber. 
 
 154. The size of the pulp chamber and of the root 
 
 *As the form of the pulp chamber gives the exact form of the pulp, 
 no separate description of the pulp will be given. It is not my pur- 
 pose to give any histological descriptions in this work. 
 
I06 THE PULP CHAMBER. 
 
 canals varies greatly in teeth of different denominations ; an 
 also in different teeth of the same denomination. In the early 
 formative stages of the teeth it is very large, and diminishes in 
 size as growth proceeds, until the tooth is fully formed. 
 Afterward this diminution goes on slowly, until, in old age, it 
 is often nearly obliterated. In the formative stage, i.e., during 
 the growth of the root of the tooth, the root canal is large and 
 funnel-shaped, with the open end of the funnel toward the 
 apex of the root (Fig. 72). As growth proceeds, and the root 
 approaches completion, this diminishes rapidly till the root is 
 fully formed, when it is contracted to a small foramen. This, 
 however, continues to diminish slowly. Therefore, the size 
 of the pulp chamber, the root canals, and the apical foramen, 
 are greater in youth than in old age. However, after adult age 
 is reached, the diminution in size is usually not great. During 
 this time, the horns of the pulp chamber are shortened by the 
 same process of formation of dentine on their surface that is 
 going on in all parts of the pulp chamber and root canal. 
 Therefore, the horns of the pulp become shorter, or recede, as 
 age advances. Indeed, the whole pulp, very slowly, becomes 
 smaller. 
 
 155. Certain processes, when present, also serve to 
 diminish the size of the pulp chamber more rapidly ; especially 
 abrasion of the teeth, a matter that seems to depend largely 
 upon the character of the occlusion. When the occlusion is 
 such that there is much rubbing, or sliding motion, of the 
 teeth against each other, wear goes on rapidly. This seems 
 to induce depositions of dentine on the walls of the pulp 
 chamber, which reduces its size ; and, especially, causes the 
 recession of the horns of the pulp. In this way, exposure of 
 the pulp from the wearing away of the dentine is delayed or 
 prevented. In many instances the pulp chamber is almost ob- 
 literated in the molars and bicuspids, and recedes rootwise of 
 the gingival line in the incisors and cuspids. Slowly progres- 
 sive caries or erosion of the teeth often induce similar deposits. 
 
 156. In the incisors and cuspids, the pulp chamber and 
 
THE PULP CHAMBERS OF THE UPPER INCISORS. lO/ 
 
 THe root canal are not sharply differentiated. The latter tapers, 
 gradually, from the full size of the largest crown portion to a 
 small foramen at the apex of the root. In teeth with more 
 than one root, the transition from pulp chamber to root canal 
 is usually sharply defined, the former being very large as com- 
 pared with the pulpal end of the latter. Indeed, the general 
 form of the pulp is a diminished counterpart of the form of the 
 surface of the tooth, except that it is in every way more slender. 
 
 157. Our studies thus far have been of the outer surfaces 
 of the teeth. The pulp chambers are within, and, therefore, 
 in the study of them, dissections must be made to expose them 
 to view. It is often necessary for the dentist to enter the pulp 
 chambers of the teeth of his patients, and there perform deli- 
 cate operations with a precision which demands the most ac- 
 curate knovv^ledge of these cavities. Therefore this work of 
 exposure, and examination, of the pulp chambers of teeth 
 should be thorough, as a preparation for operations in the 
 mouth. The form of dissection necessary will be given in con- 
 nection with the teeth as they are individually described. 
 
 THE PULP CHAMBERS OF THE UPPER INCISORS. 
 
 158. The pulp chambers and root canals of the upper 
 centra! and lateral incisors are so similar, the description of 
 one will do for all. 
 
 Dissection. — ist. Saw the tooth through on the gingival 
 line, at the labial surface, at right angles with the long axis. 
 
 2d. Saw the tooth from labial to lingual, along the cen- 
 tral line of the long axis from end to end. 
 
 3d. Saw the tooth from mesial to distal, along the cen- 
 tral line of the long axis from end to end. 
 
 159. A very thin saw in a strong frame should be used, 
 otherwise the lengthwise dissections should be made to one 
 side of the central line in their first instance, and afterward the 
 whole length of the pulp chamber exposed by grinding on a 
 stone ; or the lengthwise exposure may be made by catching 
 the tooth in the vise and removing one-half with the file, or by 
 
I08 THE PULP CHAMBERS OF THE UPPER INCISORS. 
 
 grinding on an emery wheel. After the pulp chamber is ex- 
 posed so that half of its concavity remains in the half of the 
 tooth, and has been ground smooth and flat, it should be inked 
 on an inked pad (such as is used for the rubber stamps for 
 printing) , and a print made from it. This will give the form of 
 the tooth and pulp chamber in silhouettes similar to the accom- 
 panying illustrations. The printing is facilitated by sticking 
 the tooth to a piece of hard wax for convenience in handling. 
 Ordinary modeling compound, or sealing wax, is convenient 
 and effective.* The printing is usually better done by laying 
 ordinary writing paper on a sheet of semi-soft rubber, about 
 one-eighth inch in thickness. This is specially useful when the 
 ground surface cannot be perfectly flat, as in curved roots. 
 
 i6o. In the upper central and lateral incisors (Figs. 
 1 08 and 109) there is no distinct division of the pulp cavity into 
 pulp chamber and root canal ; but there is one straight canal, 
 from the interior of the body of the crown -to the apex of the 
 root, of which the crown portion is the larger. In young teeth, 
 this has very distinctly the form of the surface of the tooth and 
 root, except that it is much more slender. The largest diame- 
 ter of the cavity is about level with the gingival line on the 
 labial surface. From this point, the pulp chamber, or canal, 
 extends toward the cutting edge of the tooth, about two-thirds 
 the length of the crown, sometimes a little more, often less, 
 and ends in a thin edge, broad from mesial to distal. In young 
 teeth this edge has three short horns (Fig. 108, a, b), or pro- 
 longations, extending -toward the three small cusps, or mam- 
 melons, seen on the edge of unworn incisors (21). 
 
 161. From the level of the gingival line toward the apex 
 of the root it tapers very gradually and regularly to a narrow 
 canal. Just within the apex of the root, almost at the end, 
 there is usually a sudden contraction of the diameter of the 
 canal, lessening it from one-third to one-half. This is the 
 
 * Dr. Cattell has found that in teaching it is very convenient to 
 have a sufficient number of small pine blocks (^ x ^ x i inch) to 
 which he has pupils cement the teeth with sealing wax. 
 
an 
 
 Fig. io8. 
 
 Fig. 109. 
 
 Fig. no. 
 
 Fig. 108* (Par. 160).— The Pulp Chamber of the Upper Central Incisor. 
 a, b, Mesio-distal sections of young teeth, showing the three short horns of the 
 pulp; c, mesio-distal section of a tooth from an adult; d, e, labio-lingual sections. 
 
 Fig. 109* (Par. 160).— Pulp Chamber of the Upper Lateral Incisor, a, b, 
 Mesio-distal sections; c, labio-lingual sections; d, labio-lingual section of a very- 
 long lateral incisor. 
 
 Fig. no* (Par. 163).— Pulp Chamber of the Upper Cuspids, a, b, Mesio- 
 distal sections; c, d, labio-lingual sections. 
 
 *Illustration, actual size. 
 
UPPER CUSPID PULP CHAMBER OF THE LOWER INCISORS. Ill 
 
 apical foramen ; but this contraction of the canal is not 
 usually present for one or two years, or more, after the tooth 
 has taken its place in the arch (q. v. Par. 154). 
 
 162. The canal becomes smaller from youth to old age. 
 In incisors just taking their places in the arch, I have found 
 the diameter of the canal at the gingival line to be from one- 
 fourth to one-'third the diameter of the neck of the tooth. In 
 early adult age, the canal may be said to average about a fourth 
 the diameter of the neck of the tooth, ranging down as age 
 advances to one-fifth, or sixth, and even to one-tenth. In the 
 lateral incisor, the chamber and canal are a little smaller than 
 in the central, but larger in proportion to the size of the tooth. 
 
 THE UPPER CUSPID. 
 
 163. The pulp chamber and root canal of the upper 
 cuspid (Fig. no) is about the same in form as that of the 
 central and lateral incisors, except that the coronal extremity 
 has the central horn much extended toward the apex of the 
 cusp of the tooth, and the mesial and lateral horns are prac- 
 tically absent. The canal is proportionately somewhat smaller. 
 However, this tooth is often somewhat flattened at the neck, 
 the long diameter being from labial to lingual. In this case 
 the pulp canal at the neck, and from thence toward the apex 
 of the root, is also much flattened in the same direction, but 
 is progressively rounded as the apex is approached. In some 
 examples, the labio-lingual diameter of the canal is double the 
 mesio-distal. As age advances, and the canal becomes smaller, 
 the opening is occasionally reduced to a mere slit. 
 
 PULP CHAMBER OF THE LOWER INCISORS. 
 
 164. (Fig. III.) The coronal portions of the pulp 
 chamber of the lower incisors is much flattened. At the 
 level of the gingival line, the long diameter is from labial to 
 lingual. The chamber extends toward the cutting edge of the 
 tooth, about two-thirds the length of the crown, and in 
 this extension its diameter is progressively diminished from 
 labial to lingual, and extended from mesial to distal, follow- 
 
 9 
 
112 PULP CHAMBER OF THE LOWER CUSPID. 
 
 ing the contour of the surface of the tooth, and ends in a thin 
 edge. In young teeth this has three short projections toward 
 the mammelons on the cutting edges of the young, unworn 
 teeth. The root has usually a narrow slit-like opening for 
 the greater portion of its length {d, g), corresponding with tire 
 form of the flattened roots. In many instances, however, the 
 root canal is divided into two portions, or canals, for a part 
 of its length {e, f). In the adult these canals are usually very 
 small. The point of separation into two canals is irregular, 
 but is usually slightly root-wise from the level of the gingival 
 line. It may occur at about the level of the gingival line, or 
 the canal may remain single for half the length of the root, 
 and then be divided for a space, the two uniting again before 
 reaching the apex. Generally, there is but one apical foramen. 
 Instances occur in which there are two, each canal remaining 
 distinct to the end. As age advances, the canals of the lower 
 incisors often become very minute. 
 
 PULP CHAMBER OF THE LOWER CUSPID. 
 
 165. The pulp chamber and the root canal of the lo^ve^ 
 cuspid (Fig. 112) are variable in size and form. At the neck 
 of the tooth the chamber is usually irregularly flattened, with 
 the longer diameter from labial to lingual, and the labial por- 
 tion wider than the lingual. The coronal portion extends 
 about two-thirds of the length of the crown toward the point 
 of the cusp, ending in a point, or horn, which is often very 
 slender. The form of the root portion of the canal depends 
 on the form of the root. It is sometimes nearly round, but 
 more frequently it is sharply flattened for the greater portion 
 of its length, becoming more rounded toward the apex. Occa- 
 sionally, this canal is divided for a part of the length of the 
 root. Also, the root is sometimes divided, a very small prong 
 appearing on its lingual side. In this there is usually a very 
 small canal that is difficult to enter with a broach. In some 
 lower cuspids the canal is very small (a), in others very large 
 (6). In a few instances I have seen it more than one-third the 
 
Fig. 112. 
 
 Fig. Ill* (Par. 164). — Pulp Chamber of the Lower Central and Lateral 
 Incisors, a, b, c, Labio-lingual sections, showing differences of form of the pulp 
 chamber; d, mesio-distal section; e, f, labio-lingual sections, showing the more 
 usual forms of the pulp chamber; g, mesio-distal section, showing large pulp 
 chamber. 
 
 Fig. 112* (Par. 165). — Pulp Chamber of the Lower Cuspids, a, Labio-lingual 
 section, showing a small chamber; b, labio-lingual section, showing a very 
 large pulp chamber; c, mesio-distal section. 
 
 'Illustration, actual size. 
 
PULP CHAMBER OF THE UPPER FIRST BICUSPID. II5 
 
 diameter of the root in the adult. In this case the diameter 
 of the canal is greater than the thickness of the walls of den- 
 tine and cementum by which it is inclosed. This renders the 
 pulp very liable to exposure in excavating carious cavities. 
 
 PULP CHAMBERS OF THE BICUSPIDS. 
 
 166. Dissections. — ist. Divide the crown from the root 
 on the gingival line with a fine saw. 
 
 2d. Divide the tooth from buccal to lingual through its 
 length with a fine saw, or remove the distal half of the tooth 
 with the file or stone. These two dissections will usually 
 exhibit the pulp chamber and root canals sufficiently, though 
 in the single-rooted teeth with two canals it is better to divide 
 the root crosswise at the middle of its length, or at several 
 points. 
 
 PULP CHAMBER OF THE UPPER FIRST BICUSPID. 
 
 167. The pulp chamber and root canals of this tooth 
 differ from those of the incisors and cuspids by having the 
 coronal chamber distinguished sharply from the root 
 canals (Fig. 113, d, e). The chamber is centrally located in 
 the long axis of the crown of the tooth, the axial walls being 
 about equal in thickness. The center of the pulp chamber is 
 about level with the gingival line, or a little toward the occlusal 
 surface. The occlusal walls are thicker than the axial, and 
 vary in thickness from one-third to two-thirds of the length 
 of the crown of the tooth. The form of the pulp corresponds 
 closely with the form of the tooth. A horn extends from 
 the coronal portion toward the apex of each cusp. The 
 buccal horn rises from the extreme buccal part of the pulp, 
 while the lingual horn rises from the extreme lingual por- 
 tion. Sometimes, especially in teeth with long cusps, they are 
 very long and slender, extending far toward the points of the 
 cusps, and in rare cases almost, or even quite, to the enamel. 
 As age advances, they become shorter, and in old age have 
 almost disappeared. In thick-necked teeth with short cusps 
 
Il6 PULP CHAMBER OF THE UPPER SECOND BICUSPID. 
 
 the horns of the pulp chamber are short, and the occlusal wall 
 is usually very thick. 
 
 The root canals in upper first bicuspids that have two 
 roots pass from the pulp chamber through the center of each 
 root to its apex, and are known as the buccal and lingual 
 root canals (e). The buccal canal arises from the extreme 
 buccal side of the pulp chamber, and the lingual canal from 
 the extreme lingual side, and their course is almost parallel 
 with the walls of these two portions of the pulp chamber. The 
 floor of the chamber is rounded over in an arch from one canal 
 to the other. Each canal begins in a funnel-shaped opening 
 leading into a narrow round canal, which tapers gradually to 
 the apical foramen. Many of the upper first bicuspids have 
 only one root ; but they generally have two root canals almost 
 exactly similar to those with two roots. Occasionally, how- 
 ever, these come together and end in one apical foramen, or 
 there may be a communication between the two canals in some 
 part of their course (d). More rarely, the upper first bicuspid 
 has one broad (from buccal to lingual), flat canal passing 
 through the whole length of its single root. Sometimes this 
 is divided near the apex (b). 
 
 PULP CHAMBER OF THE UPPER SECOND BICUSPID. 
 
 i68. The pulp chamber of the upper second bicuspid 
 (Fig. 114) is similar to that of the first {q. v., Par. 167), but 
 the horns of the pulp are usually shorter. In this tooth there is 
 generally but a single root canal {e, f). This is approached 
 by an opening that is broad bucco-lingually, and tapers grad- 
 ually toward the apex of the root, ending in a narrow apical 
 foramen. The canal is often quite large, and the demarkation 
 of the pulp chamber, as distinguished from the root canal, 
 very indistinct, or entirely absent. Examples are not infre- 
 quent, however, in which there are two root canals in the 
 single root {d). They are then similar to those of the first 
 bicuspid ; but, sometimes, the two canals end in a common 
 apical foramen (a). 
 
Fig. 115. 
 
 Fig. 116. 
 
 Fig. 113* (Par. 167). — Pulp Chamber and Root Canals of the Upper First 
 Bicuspids, b, Bucco-lingual section of single-rooted tooth, witli single canal di- 
 vided near the apex of the root; a, cross-section of the same, mid-length of the ' 
 root; d, bucco-lingual section of a single-rooted tooth with two canals, which con- 
 nect at one point; c, cross-section of the same, a little rootwise from the pulp 
 cham.ber; e, bucco-lingual section of double-rooted tooth, showing the more usual 
 form of the chambers and canals. 
 
 Fig. 114* (Par. 168). — Pulp Chamber and Root Canals of the Upper Second 
 Bicuspid. a, Bucco-lingual section, showing chamber with long, slender horn, 
 also two canals, which unite in the apical third of the root; b, cross-section of a 
 root with two canals; c, cross-section of a root with a single large canal; d, bucco- 
 lingual section of a single root with two canals; e, f, bucco-lingual sections, show- 
 ing the more usual form of the pulp chamber and root canal of this tooth. 
 
 Fig. 115* (Par. 169). — Pulp Chamber and Root Canals of the Dower First 
 Bicuspid, a, Bucco-lingual section, showing the more usual form; b, bucco-lingual 
 section, showing a peculiar and very unusual division of the root canal; c, cross- 
 section in the body of the root. 
 
 Fig. 116* (Par. 169). — Pulp Chamber and Root Canal of the Lower Second 
 Bicuspid, a, b, Bucco-lingual sections, showing the more usual forms of the 
 chamber and canal in this tooth. 
 
 "Illustration, actual size. 
 
PULP CHAMBERS LOWER BICUSPIDS UPPER MOLARS. 1 19 
 
 PULP CHAMBERS OF THE LOWER BICUSPIDS. 
 
 169. The pulp chambers of the lower bicuspids (Figs. 
 115 and 116) seldom show a marked distinction from the root 
 canals. There is, however, usually a coronal bulbous portion 
 which connects with the pulp canal proper by an extended 
 funnel-shaped constriction (a, b). In the lower first bicus- 
 pid, the coronal extremity ends in a horn, which extends 
 toward the point of the buccal cusp. This horn may be short 
 and obtuse, or long and pointed. There is, generally, a well- 
 marked protrusion toward the lingual cusp, but no extended 
 horn. It is rather an enlargement of the bulb in that direc- 
 tion. In the lower second bicuspid this protrusion is more 
 considerable, and in some examples it is elongated into a 
 slender point, especially in young teeth (Fig. ii6, h). In the 
 three-cusped lower second bicuspids (Par. 62, Fig. 49) there 
 are two of these on the lingual side, spreading toward the 
 mesial and distal. They are generally short, but by their 
 protrusion are brought rather nearer the surface of the tooth 
 than other horns of the pulp, and are; therefore, more liable 
 to be opened into when excavating proximate cavities. 
 
 170. The root canals of the lower bicuspids are usually 
 large in the first half, tapering to a fine canal in the apical 
 third, of their length. The canal of the lower first bicuspid 
 is usually nearly round, and that of the second is considerably 
 flattened ; and in both they are usually straight. Bifurca- 
 tions of these canals are rare, but occur occasionally. In the 
 illustrations (Fig. 115, b) one is shown dividing in such a 
 way that the division would not be likely to be detected by a 
 broach. 
 
 PULP CHAMBERS OF THE UPPER MOLARS. 
 
 171. Dissections. — ist. With a fine saw, separate the 
 crown from the root level with the gingival line. 
 
 2d. Cut away the mesial surface of the crown and the 
 mesial surface of the mesial and lingual roots with the file 
 or a corundum stone, till the canals in each are fully exposed. 
 
I20 PULP CHAMBERS OF THE UPPER MOLARS. 
 
 As the mesial root is generally curved, some care is required 
 to fully expose the full length of the canal without cutting 
 too far in the central portion of its length. If the curved sur- 
 face is made smooth, good prints can generally be made by 
 using a piece of semi-soft rubber under the paper, and, while 
 pressing it to the paper, rolling the tooth so as to bring all of 
 the length of the curved surface in contact. 
 
 3d. Cut away the buccal surface so as to expose the 
 pulp chamber and canals of the two buccal roots, observing 
 the same precautions as in the second dissection. 
 
 In the first dissection both crown and root should be 
 examined. First, clean the portion of the chamber in the 
 crown, to study carefully its horns and its general shape or 
 contour with relation to the outer surface of the tooth. The 
 root canals should be cleaned with the broach, and their size 
 and direction carefully studied; also, the position of the open- 
 ings leading from the pulp chamber should be studied with 
 regard to their relation to the several points of the surface of 
 the crown. This latter is especially important. Several dis- 
 sections should be made of each of the upper molars. 
 
 4th. Grind away the root portion of the first dissection, 
 printing occasionally till the bifurcation of the roots is reached. 
 
 172. The pulp chamber of the upper molars is very 
 distinct from the pulp canals, the latter often leaving the 
 former by very small openings (Fig. 117). The average diam- 
 eter of the pulp chamber is about equal to the thickness of 
 the axial wall by which it is surrounded, sometimes more, 
 sometimes less. The occlusal wall is usually considerably 
 thicker. The form of the pulp chamber is generally similar 
 to that of the crown of the tooth ; but the horns in the young 
 tooth are often quite slender as compared with the cusps, and 
 penetrate far toward the enamel. The length of these dimin- 
 ishes as age advances. In teeth much flattened mesio-distally, 
 as often occurs in the upper first molars, and especially with 
 the second, the equal thickness of the axial walls is usually 
 maintained pretty closely, so that the flattening of the pulp 
 chamber seems out of proportion to the form of the tooth. 
 
PULP CHAMBERS OF THE UPPER MOLARS. 121 
 
 173. The floor of the pulp chamber is rounded or 
 arched in the center, and falls away toward the mouths of the 
 canals. The latter are situated in the position of the angles 
 of a triangle (the molar triangle. Figs. ii8 and 119), the 
 mesial line of which is the longest, the buccal the shortest, 
 and the distal the intermediate length. For the upper first 
 molar, this triangle is well shown in the illustrations repre- 
 senting sections a little rootwise from the floor of the pulp 
 chamber (c). This is best seen in the specimen itself; and the 
 position and the direction of the canals, with relation to the 
 walls of the pulp chamber and the main points of the surface 
 of the crown, should be carefully studied. 
 
 174. The opening into the lingual root (Fig. 117, b) is 
 the simplest and most direct. Generally, it begins in a funnel- 
 shaped opening inclining to the lingual, which quickly narrows 
 to the dimensions of a moderately small canal, and continues 
 to taper to the apical foramen. It is usually straight, or but 
 slightly curved. 
 
 175. The opening into the mesial canal is under the 
 mesio-buccal cusp, close against the mesio-buccal angle of 
 the pulp chamber. It often happens that this canal begins 
 in a groove in the angle of the chamber (Fig. 119, b), making 
 this the thinnest point in the dentinal walls surrounding it, 
 In young teeth, the mouth of the canal is of a flattened funnel- 
 shape, which is quickly contracted into a very fine canal; but 
 in the adult, it often begins as a fine canal. Its course at first 
 is to the buccal and mesial, and then curves to the distal. It 
 is usually distinctly flattened, and often has a thin edge to the 
 lingual. It is often a very difficult canal to clean with a 
 broach. To find this canal the point of the broach should 
 be directed into the mesio-buccal angle of the pulp chamber; 
 and, while held against the wall within this angle, it is slid 
 toward the root. It will rarely fail to glide into the canal. 
 
 176. The distal canal usually begins abruptly as a fine 
 opening (Fig. 117, a^ c), situated at the disto-buccal angle of 
 the floor of the pulp chamber (Figs. 118 and 119) ; so that a 
 
122 PULP CHAMBERS OF THE UPPER MOLARS. 
 
 broach pressed into that angle will easily glide into it. But 
 in some instances, especially in the upper second molars, the 
 opening is in the floor of the pulp chamber at a little distance 
 from the immediate angle toward the center of the floor, and 
 then, in positions which limit the use of the eye, it is often 
 difficult to find. In teeth much flattened at the neck, the 
 opening of this canal may begin very close to the mouth of 
 the mesial canal (Fig. 120, a), or close against the distal wall 
 of the chamber, half-way from the buccal to the lingual wall, 
 or anywhere between this point and the disto-buccal angle. 
 The first direction of the canal will vary according to its posi- 
 tion. If it is found in a fairly well-defined disto-buccal angle 
 of the chamber, its direction will be a little inclined to the 
 distal, and the broach will penetrate it easily ; if in the floor 
 of the chamber, it will sometimes be straight, as in the former 
 case ; but more generally the first direction will be to the distal 
 and buccal, with considerable curve afterward. If found close 
 to the mesial canal, its course is usually first sharply to the 
 distal, when it curves rather abruptly toward the apex of root. 
 If found along a smooth or curved distal wall, the course will 
 generally be to the distal and buccal, with but little curve. 
 This canal is usually very fine from its beginning, and almost 
 or quite round. 
 
 177. While the canals are similar in all of the upper 
 molars, there are differences in the form of the floor of the 
 pulp chamber that may be briefly generalized. The pulp 
 chamber of the upper second molar (Fig. 120) is usually much 
 more flattened from mesial to distal than in the first molar. 
 This changes the relation of the mouths of the canals some- 
 what, rendering the distal angle of the triangle formed by 
 them more obtuse, and brings the mouth of the distal canal 
 nearer the mesial line of the triangle, so that it seems to be 
 found along the distal wall of the narrowed chamber. In 
 others, it is found in the extreme buccal portion crowded close 
 against the mouth of the mesial canal. 
 
 178. The position of the openings of the canals in the 
 
Hfcf 
 
 Fig. 117. 
 
 dftftood 
 
 a b e 
 
 Fig. 118. 
 
 a t> 
 
 Fig. 119. 
 
 H a 
 
 Fig. 120. 
 
 Fig. 121. 
 
 Fig. 117* (Par. 172). — Pulp Chamber and Root Canals. of the Upper First 
 Molar, a, c, Mesio-distal sections, showing the pulp chamber and the canals in 
 the mesial and distal roots; b, bucco-lingual section, showing the pulp chamber 
 and the canals in the mesial and lingual roots; d, bucco-lingual section, showing 
 the chamber and the canals in the distal and lingual roots. 
 
 Figs. 118,* 119* (Par. 173). — Pulp Chamber and Root Canals of the Upper 
 First Molars, cross sections, a, Centrally through the pulp chamber; b, section 
 just at the floor of the pulp chamber; c, section a little rootwise from the pulp 
 chamber, showing the canals and the form of the molar triangle. 
 
 Fig. 120* (Par. 177). — Pulp Chamber and Root Canals of the Upper Sec- 
 ond Molar, a, Mesio-distal section, showing pulp chamber and the canals in the 
 mesial and distal roots; b, bucco-lingual section, showing the chamber and the 
 canals in the distal and lingual roots. 
 
 Fig. 121* (Par. 178). — Pulp Chamber and Root Canals in the Upper Third 
 Molar, a, Bucco-lingual section, showing pulp chamber and the canals in the 
 mesial and lingual roots; b, mesio-distal section of a single rooted tooth, showing 
 the form of the pulp chamber and the mesial and distal root canals. 
 
 *Illustration, actual size. 
 
I'ULl' CHAMBERS OF THE LOWER MOLARS. I25 
 
 upper third molar (Fig. 121) is usually much the same as in 
 the first and second, varying so as to resemble either. Occa- 
 sionally there is more than the usual number, and others with 
 only one or two. When there is but one, it is commonly quite 
 large. Four, five, or even seven or eight, are sometimes 
 found. 
 
 PULP CHAMBERS OF THE LOWER MOLARS. 
 
 179. Dissections. — ist. Saw the tooth through the gin- 
 gival line dividing the crown from the root. This cut will 
 pass through the body of the pulp chamber and give a good 
 view of the roof and floor, and a good idea of the general form. 
 The root canals should be cleaned and examined with the 
 broach. 
 
 2d. Saw the tooth through from end to end centrally 
 from mesial to distal, or grind or file away the buccal side till 
 the pulp chamber and the root canals are exposed. As there 
 are usually two canals in the mesial root, an exact central cut 
 from mesial to distal will generally fail to expose the canals, 
 and the cut will be better made at a slight angle, so as to ex- 
 pose either the buccal or lingual canal of the mesial root. 
 
 3d. Grind or file away the mesial surface of the 
 crown and root till the pulp chamber and the whole length of 
 the canals in the mesial root are exposed. As this root is usu- 
 ally curved, the cutting must be done with care, and the curve 
 followed. 
 
 4th. Cross-sections of the roots should be made at 
 intervals. An excellent study is to begin grinding at the apex 
 of the roots, printing occasionally, and continuing the grinding 
 until the pulp chamber is reached. This will display cross-sec- 
 tions, at intervals, of the entire root canals. Enough of these 
 dissections should be made of each of the lower molars to make 
 the student familiar with each class. 
 
 180. The pulp chambers of the lower molars (Figs. 
 122, 123, 124) has the same general form as the surface of the 
 crown, but is generally rather more angular. The wall of the 
 
126 PULP CHAMBERS OF THE LOWER MOLARS. 
 
 chamber toward the occlusal surface is convex toward the 
 pulp ; the horns extend from the extreme angles toward the 
 apex of each cusp. The floor through the central portion is 
 arched or convexed mesio-distally, and concave bucco-lingu- 
 ally. The mesial wall of the cavity is flat, and longer than the 
 distal. The mesio-buccal and mesio-lingual angles are sharp 
 and projecting, while the distal angles are rounded (Fig. 123, 
 d, g). The size of the chamber varies much. In youth its 
 diameter is often as much as two-fifths of the crown and sel- 
 dom less than one-third. This diminishes as age advances, 
 and in old age it is often very small, or, especially where there 
 has been considerable abrasion of the teeth, the pulp chamber 
 may be almost obliterated. 
 
 181. The root canals of the lower molars proceed from 
 the mesial and distal portions of the pulp chamber (Fig. 122, 
 a, b) . The mesial canal, at its mouth, is usually about as 
 broad from buccal to lingual as the whole breadth of the cham- 
 ber, including its angular projections. Either at, or a little 
 rootwise from the floor of the pulp chamber, it is usually di- 
 vided into two very small canals which diverge at first, and ap- 
 proach each other afterward, but usually remain distinct, each 
 ending in its own apical foramen (Fig. 122, c). Occasionally, 
 however, they are united in the apical third of the root, and 
 end in a common apical foramen. Again, there may be a com- 
 munication between them in the apical portion of the root, 
 each canal remaining otherwise complete in itself. A few have 
 one broad flattened canal (Fig. 123, d, e, f). These canals are 
 usually minute, and very difficult to thoroughly clean with the 
 broach, though the mesio-buccal canal is usually easily found, 
 if the pulp chamber is thoroughly opened. By placing the 
 point of the broach in the mesio-buccal angle of the cham- 
 ber and pushing it gently on, it will generally glide into the 
 canal. The first direction inclines to the mesial and buccal, 
 after which it curves to the distal and lingual (Fig. 122, c). 
 Generally, these curves are easy, without short bends. The 
 broach easily glides into the mesio-lingual canal In- placing 
 
Fig. 122. 
 
 g h 
 
 Fig. 123. 
 
 9 
 
 Fig. 124. 
 
 Fig. 125. 
 
 Fig. 122* (Par. i8o).— Pulp Chamber and Root Canals of the Lower First 
 Molar, a, b, Mesio-distal sections, showing the form of the pulp chamber and 
 root canals; c, bucco-Iingual section, showing the canals in the mesial root. 
 
 Fig. 123* (Par. 180).— Cross-sections through the Crown and Root of the 
 Lower First Molar, showing the pnlp chamber and root canals, rf, g, Sec- 
 tions through the pulp chamber; e, h, sections a little rootwise from the pulp 
 chamber; /, i, sections near apex of root. 
 
 Fig. 124* (Par. 180).— Pulp Chamber and Root Canals of the Lower Sec- 
 ond Molar. , a, c, Mesio-distal sections, showing the form of the pulp chamber 
 and root canals; b, bucco-lingual section of the distal root and crown; d, bucco- 
 lingual section through the mesial root and crown, showing two canals with com- 
 munication in the apical third of the root. This cornmunication is not very com- 
 mon. 
 
 Fig. 125* (Par. 182).— Pulp Chamber and Root Canals of the Lower Third 
 Molar, a, c. In double-rooted teeth; b, single-rooted teeth. 
 
 'Illustration, actual size. 
 10 
 
VARIATIONS OF THE FORM OF PULP CHAMBERS. I29 
 
 the point in the mesio-lingual angle of the pulp chamber 
 and sliding it toward the root. The first inclination is to the 
 mesial, but occasionally to the lingual, after which it curves 
 to the distal and buccal. 
 
 182. The distal canal is approached by a funnel-shaped 
 opening, of which the central part of the distal wall of the 
 pulp chamber becomes a portion. Its direction is a little to 
 the distal, and is generally very nearly straight to the apex. 
 At first, it is flattened, with the long diameter from buccal to 
 lingual, and progressively becomes rounded, and tapers regu- 
 larly to the apical foramen. It is generally much larger than 
 the canals of the mesial root, and is easily cleaned with the 
 broach. If the mouth is wide open, and the handle of the 
 broach brought against the upper central incisors with the 
 point directed against the posterior wall of the pulp chamber, 
 it will easily glide into the canal, and pass to the apical fora- 
 men. This particular position for easily entering the distal 
 canal is important for all the lower molars. Occasionally, the 
 lower third molar has but one root canal (Fig. 125, b) , which 
 is then generally very large. More rarely, only a single canal 
 will be found in the lower second molar, but generally the 
 canals of the second and third lower molars are similar to 
 those of the first. The pulp chambers ars usually smaller, and 
 oftener irregular in outline. The lower third molar has, occa- 
 sionally, a very large pulp chamber. 
 
 VARIATIONS OF THE FORM OF PULP CHAMBERS. 
 
 183. Many variations of form occur in the pulp cham- 
 bers and root canals. The roots of the teeth may be abnor- 
 mally crooked; and then the canals will be abnormally 
 crooked. In many instances, the pulp chamber will have in it 
 secondary formations, called nodules, which may be ad- 
 herent to the walls, or block the mouths of the canals and 
 prevent a broach gliding into them. These also occur, occa- 
 sionally, within the canals, partially blocking the way of the 
 broach. Sometimes the pulp chamber will be filled with 
 
130 PULP CHAMBERS OF THE DECIDUOUS TEETH. 
 
 nodular deposits so completely that there seems to be no room 
 for the tissues of the pulp. These deposits will have to be re- 
 moved before the root canals can be reached and entered, 
 after which the canals will generally be found open. These de- 
 posits occur within the pulp chambers of any of the teeth ; but 
 they cause annoyance more frequently in the molars. 
 
 184. Occasionally lateral openings occur from the 
 root canals to the surface of the root. I have seen more of 
 these from the canals of the lower molars than from those of 
 any other teeth. Generally, they follow the course of the den- 
 tal tubules, and open on the side of the root. They may di- 
 verge to one side and curve toward the apex of the root. 
 These cannot often be detected, except in dissections of the 
 root, and occur so rarely they may be ignored in practice. 
 
 185. Sometimes the horns of the pulp approach ab- 
 normally near the points of the cusps of some of the teeth, as 
 in the upper first bicuspids and in the mesio-buccal cusp of the 
 upper first molar. Then the pulp is more liable to exposure 
 in excavating carious cavities. 
 
 PULP CHAMBERS OF THE DECIDUOUS TEETH. 
 
 186. The pulp chambers of the deciduous teeth are 
 proportionately larger, and the thickness of their walls less, 
 than those of the corresponding permanent teeth. The pulps 
 are, in consequence, exposed with much less penetration of 
 tooth substance, and, therefore, more liable to exposure from 
 caries, or in the use of cutting instruments. The root canals 
 are generally larger than in the permanent teeth of the same 
 denomination, but are of the same general form. Also, the 
 same rules for finding the root canals in the permanent molars 
 apply to the deciduous. 
 
 ARRANGEMENT OF THE TEETH. 
 
 187. The upper teeth are arranged in the form of a 
 semi-ellipse, the long axis passing between the central inci- 
 sors (Figs. 126 and 127). In this curve the cuspids stand a 
 
ARRANGEMENT OF THE TEETH. 131 
 
 little prominent, giving a fullness to the corners of the mouth. 
 In different persons there is much variation of the form of the 
 arch within the limits of the normal. Occasionally the bicus- 
 pids and molars form a straight line, instead of a curve, and 
 frequently the third molars are a little outside the line of the 
 ellipse. In the examination of casts of the most perfect den- 
 tures it is found that the two sides do not perfectly correspond, 
 and that certain teeth deviate slightly from the perfect line. 
 The incisors are arranged with their cutting edges forming a 
 continuous curved line from cuspid to cuspid, and this line is 
 continued over the cusps of the cuspids and the buccal cusps 
 of the bicuspids and molars to the distal surface of the third 
 molars. From the first bicuspid to the third molar the lingual 
 cusps of these teeth form a second line of elevations. Between 
 these two, the lingual and buccal cusps, there is a continuous, 
 but irregular, valley or sulcus. 
 
 188. The lower teeth are arranged similarly (Fig. 185), 
 but on a slightly smaller curve, so that the line of the ellipse, 
 which falls on the buccal cusps of the upper bicuspids and 
 molars, will fall upon the buccal surfaces near the gum on the 
 lower teeth (Fig. 126). Therefore, in occlusion, the upper teeth 
 project a little to the labial and buccal of the lower at all points 
 of the arch (Fig. 131). The incisors and cuspids occlude so 
 that the cutting edges of the lower incisors and cusps of the 
 cuspids make contact with the lingual surfaces of the similar 
 teeth of the upper jaw near their cutting edges (Fig. 128). In 
 this, however, there is much variety within the limits of a 
 normal occlusion. Sometimes the lower incisors strike the 
 lingual surfaces of the upper near the linguo-gingival ridge, 
 and may strike at any point between that and the cutting 
 edges. In abnormal occlusions the lower incisors may 
 miss the upper, striking the gums posterior to them, or they 
 may occlude anterior to the upper incisors. The broad- 
 cusped occlusal surfaces of the bicuspids and molars of the 
 opposing dentures rest on each other in such a way that 
 the lingual cusps of the upper teeth fit with more or less 
 
132 ARRANGEMENT OF THE TEETH. 
 
 accuracy into the general sulcus formed between the buccal 
 and lingual cusps of the lower teeth The buccal row of cusps 
 of the lower teeth, in a similar way, are fitted into the sulcus 
 formed between the buccal and lingual cusps of the upper teeth 
 (Figs. 129 and 130). This arrangement is such that when the 
 teeth are in occlusion, it leaves the buccal inclines of the buccal 
 'cusps of the upper teeth outside the buccal surface of the lower 
 teeth (a), and, also, leaves a ledge formed by the abrupt lin- 
 gual inclines of the lingual cusps of the lower teeth along the 
 lingual line of the occlusion (b). This brings the occlusal sur- 
 faces of the teeth in the best form of apposition for the pur- 
 poses of mastication. The forms presented to the cheek and 
 to the tongue hold these soft tissues a little apart from the 
 actual contact-points of the occlusion, and thus prevent thera 
 from being caught and pinched, or crushed, between the teeth 
 in the act of mastication. In youth, while the permanent teeth 
 are taking their places, and before the cusps are properly fitted 
 to the sulci, we often find the cheeks or tongue wounded by 
 being caught between falsely occluded points. With the after 
 movements of the teeth, by which they are more perfectly 
 arranged, this difficulty disappears. 
 
 189. The line from before backward on which the oc- 
 clusion occurs is not quite a plane; in the lower jaw it pre- 
 sents a slight curve, or concavity, and in the upper jaw a con- 
 vexity (Fig. 131, c to d). This concavity of the line of the 
 occlusal surfaces of the lower teeth is a little greater than the 
 convexity of the upper, so that the cutting edges of the lower 
 incisors pass a little beyond, and to the lingual of the cutting 
 edges of the upper incisors. 
 
 190. In the occlusion the relative mesio-distal position 
 of the particular teeth of the upper jaw to the lower is im- 
 portant (Fig. 131). At their cutting edges, the upper central 
 incisors are about one-third wider mesio-distally than the 
 lower centrals. The upper central, therefore, occludes with 
 the lower central, and also with from one-third to one-half 
 of the lower lateral incisor. The upper lateral occludes with 
 
Fig. 126. 
 
 Fig. 126 (Par. 187).— The Elliptical Form of the Arch. The crowns of the 
 teeth of both upper and lower jaws, drawn from the casts of a very regularly 
 formed arch, and the line of a true ellipse (in dots) placed over them, showing the 
 comparative size of the upper and lower arch, and the deviations from perfect 
 regularity. 
 
ARRANGEMENT OF THE TEETH. 1 35 
 
 the remaining portion of the lower lateral and the mesial 
 portion of the lower cuspid. The upper cuspid is usually 
 rather broader mesio-distally than the lower, and in occlu- 
 sion covers its distal two-thirds and about half of the lower 
 first bicuspid, so that its lingual, or triangular ridge, is be- 
 tween the cusp of the lower cuspid and the buccal cusp of 
 the lower first bicuspid, the point of its cusp overlapping 
 the lower teeth. The buccal cusp of the lower first bicuspid 
 occludes in the space between the upper cuspid and upper 
 first bicuspid. This order is now maintained between the 
 bicuspids. The buccal cusp of the upper first bicuspid over- 
 laps (to the buccal) the space between the two lower bicus- 
 pids, and its lingual cusp occludes in the sulcus between them, 
 while the buccal cusp of the lower second bicuspid occludes 
 in the sulcus between the two upper bicuspids. The cusps 
 of the upper second bicuspid occlude between the lower 
 second bicuspid and lower first molar. The broad surfaces 
 of the molars come together, so that the mesial two-thirds of 
 the upper first molar covers the distal two-thirds of the lower 
 first molar, and the distal third of the upper first molar covers 
 the mesial third of the lower second molar. This brings the 
 oblique ridge of the upper molar between these two lower 
 teeth. This order is continued between the remaining molars, 
 but less perfectly as the teeth are more irregularly formed. 
 The upper third molar is usually smaller than the lower third 
 molar, yet it generally extends over its distal surface. 
 
 191. The inclination of the teeth is the deviation of 
 their long axes from the perpendicular line. The direction 
 of the inclination is expressed by some accompanying word. 
 The upper incisors and cuspids are so arranged that their 
 'crowns are inclined more or less forward, or toward the lip, 
 and slightly toward the median line. The mesial inclination 
 is continued in the bicuspids and molars, diminishing from 
 before backward, and is usually lost at the second or third 
 molar. As a rule, the bicuspids and molars of the upper jaw 
 are also slightly inclined toward the cheek, but in many den- 
 
136 ARRANGEMENT OF THE TEETH. 
 
 tures this inclination is slight, or wanting in the bicuspids and 
 first molars to reappear in the second and third molars, though 
 it may be absent even in these without necessary malforma- 
 tion. 
 
 192. The lower incisors and cuspids are also inclined 
 with their crowns toward the lip, but in less degree than the 
 upper. And even the perpendicular position of these is not 
 inconsistent with a normal arrangement. They have, how- 
 ever, a mesial inclination, but usually much less than the 
 corresponding upper teeth. The lower bicuspids, within 
 the limits of the normal arrangement, vary considerably in 
 their inclinations. Sometimes they have a strong mesial 
 inclination, and at other times they are nearly or quite per- 
 pendicular. In many dentures, they also have a lingual inclina- 
 tion, but may be perpendicular or even have a slight buccal 
 inclination. The lower molars usually have a slight mesial 
 and lingual inclination (Fig. 135). In many examples, how- 
 ever, the mesial inclination is wanting, especially in the second 
 and third molars. 
 
 193. All the teeth are a little broader mesio-distally at 
 or near the occlusal surfaces than at their necks. Therefore, 
 when arranged in the arch with their proximate surfaces in 
 contact, there is a considerable space between their necks 
 (Fig. 131). These are known as the inter-proximate or V- 
 shaped spaces. The sharp angle or apex of the V-form is 
 toward the occlusal surface, or at the contact-point of the 
 proximation, and the open end or base is at the crest of the 
 alveolar process (Figs. 134, 135, 136). In normal conditions, 
 this space is filled by the soft tissues, or gums (141). The 
 average arch measures about 127 millimeters (5 inches) from 
 the distal surface of the right third molar to the distal surface 
 of the left third molar, following the curve of the arch, on the 
 line of the contact-points of the teeth. This represents the 
 average mesio-distal measurement of the crowns of the teeth 
 of the upper jaw taken collectively. The average measure- 
 ment of the teeth at their necks is about 89 millimeters (3.5 
 

 Fig. 127. 
 
 Fig. 128. 
 
 Fig. 127*- (Par. 1S7).— Arrangement of the Teeth in the Arch. Tlie arch of 
 the . upper jaw. 
 
 (Par. 210).— The Teeth and the Gums and the Rug^ of the Roof of the 
 Mouth. 
 
 Fig. 128 (Par. 1S8).— Labio-Lingual Position of the Incisors in Occlusion. 
 
 Fig. 129 (Par. 18S).— Bucco-Lingual Position of the Bicuspids in Occlu- 
 sion. 
 
 Fig. 130 (Par. 188).— Bucco-Lingual Position of the Molars in Occlusion. 
 
 'Illustration, actual size. 
 
ARRANGEMENT OF THE TEETH. I39 
 
 inches). The remaining 38 millimeters (1.5 inches) represent 
 the average sum of the inter-proximate spaces taken col- 
 lectively. 
 
 194. On account of differences in the conformation of 
 the crowns and the inclination of the teeth the inter- 
 proximate spaces vary much in width in different dentures. 
 They are much wider between bell-crowned teeth than be- 
 tween thick-necked teeth; but some inter-proximate space 
 exists in every normal denture. When the crowns of the 
 incisors and cuspids are much inclined toward the lip, the 
 necks of the teeth form a smaller circle than the line of the 
 contact-points of the proximation, and in this way the inter- 
 proximate spaces may be considerably narrowed. Generally, 
 the inter-proximate space is wide between the necks of the 
 central incisors. The suture joining the maxillary bones 
 passes between the roots of these teeth, and they are somewhat 
 farther apart than the roots of the central and lateral incisors, 
 or those of the lateral incisor and the cuspid. Therefore, in 
 these latter, the inter-proximate spaces are of less width (Fig. 
 134). Between the bicuspids the inter-proximate spaces are 
 wider at the necks of the teeth than between the anterior 
 teeth, on account of the greater breadth of the crowns as 
 compared with the roots (Fig. 135, b). The widest inter- 
 proximate spaces are usually between the necks of the molars 
 (Figs. 135 and 136, c). 
 
 When the proximate surfaces of the teeth are carefully 
 examined it is found that at the level of the contact-point they 
 are more or less rounded from buccal to lingual, and in this 
 rounding the mesio-distal diameter of the bicuspids and 
 molars is narrowed more toward the lingual than toward the 
 buccal. This gives rise to spaces between the angles of the 
 teeth, which begin at the point of proximate contact and widen 
 toward the buccal on the one side and. toward the lingual upon 
 the other. These are the buccal and lingual inter-proximate 
 embrasures (see Figs. 132 and 133). The depth of these 
 embrasures and their width vary greatly in different den- 
 tures. Usually between bell-crowned teeth they are deep. 
 
140 ARRANGEMENT OF THE TEETH. 
 
 while between thick-necked teeth they are shallower. The 
 lingual embrasures are generally much deeper than the buccal 
 between the angles of the bicuspids and molars, while the 
 labial embrasures are deeper than the lingual between the 
 angles of the incisors. 
 
 The form of these inter-proximate embrasures seems to 
 be important with reference to cleanliness of the inter-proxi- 
 mate spaces ; for when they are deep, food, in its excursions 
 over the teeth and gums during mastication, is directed into 
 them, and is caused to glide out to the lingual and to the 
 buccal, rubbing through the embrasures and over the gum 
 septum and carrying away all debris that may have found 
 lodgment about the inter-proximate spaces. 
 
 195. The points of proximate contact in the best- 
 formed arches are near the occlusal surfaces of the teeth. In 
 imperfectly developed teeth, in which the crowns are much 
 rounded toward the occlusal surfaces, the contact points are 
 more toward the gingival. In the incisors and cuspids they 
 are in direct line with the cutting edges (Fig. 132, a). In the 
 bicuspids the contact is near the mesio- and disto-bucco- 
 occlusal angles and nearly in line with buccal cusps (Fig. 
 132, b). The mesial and distal Battened surfaces of these teeth 
 converge to the lingual to such an extent that, though they are 
 arranged in arch form the contact-points remain close to the 
 buccal-point angles. In many excellent dentures there is a 
 decided interproximate embrasure opening to the lingual 
 but in thick-necked teeth and those of a more rounded con- 
 tour, the contact-points are often more toward the lingual, and 
 there is but a slight lingual embrasure. In thfe molars the 
 contact-points, as a rule, are removed rather more to the 
 lingual, but still in the best-formed dentures they will be found 
 nearly in line with the buccal cusps (Fig. 132, c). Between 
 the upper first and second molars the contact-point is often 
 extended toward the lingual by the prominent disto-lingual 
 cusp of the first molar ; and, even when otherwise, the general 
 rounding of the distal surfaces of the upper molars often 
 

 i--i---:- 
 
 ...v 
 
 ma 
 
 
 
 
 \ 
 
 Fig. 131. — Actual size. 
 
 Fig. 131 (Par. 188). — Arrangement of the Teeth. Labial and buccal aspect of 
 the upper and lower teeth as arranged in the arch. 
 
 (Par. 197). — The Alveolar Process of the Upper and Lower Jaws, with 
 THE Teeth in Position. 
 
ARRANGEMENT OF THE TEETH. I43 
 
 brings the contact-point near the middle line of the teeth. 
 In lower first molars the large distal cusp brings the contact- 
 point with the second molar close to the buccal side, with a 
 considerable lingual inter-proximate embrasure (Fig. 133, c). 
 If the distal cusp is small, the contact-point is usually extended 
 toward the lingual, often as far as half the bucco-lingual 
 breadth of the teeth. Between the second and third molars 
 the contact-point is most frequently near the central line of 
 the teeth (Fig 133, d). In the best-formed dentures the 
 form of the proximate contact is such as to prevent food 
 from being crowded between the teeth in mastication, and 
 therefore, such as to keep these spaces clean and the inter- 
 proximate gingivae in health. But many faulty forms are 
 met with which allow food to leak through into the inter- 
 proximate space and crowd the gum away, forming a pocket 
 for the lodgment of debris, giving opportunity for decom- 
 position, and resulting in caries of the proximate surfaces, or 
 disease of the gum and peridental membrane. A close study 
 of the forms of proximate contact in the best-formed dentures 
 demonstrate that the immediate contact-point is on rounded 
 prominences of the proximate surfaces. The rounding of the 
 surfaces bucco-lingually and the form of the buccal and lingual 
 inter-proximate embrasures are well shown in Figs. 132, 133, 
 which were made by removing the occlusal surfaces of the 
 teeth by grinding until the contact-points were reached, and 
 then accurately drawing the outlines to show the form of the 
 contact-points. In Figs. 134, 135, and 136 the outlines of the 
 teeth are carefully drawn, so as to illustrate the form of the 
 contact occluso-gingivally, from which it will be seen tha-t 
 they are sharply rounded in this direction also. Therefore 
 the proximate contact of the teeth is such as would be made 
 by the contact of two marbles, or at a single small point. 
 These points of proximate contact also slide slightly upon 
 each other in the act of chewing food, the peridental mem- 
 branes allowing the teeth a slight motion, so that any sub- 
 stance forced between them easily glides out in one way or 
 
 II 
 
144 '^HE ALVEOLAR PROCESS AND ALVEOLI. 
 
 the Other. Furthermore, the form of the inter-proximate 
 gum tissue, the gum septum, is that of an arch with its con- 
 vex side toward the point of contact or occlusal surfaces of 
 the teeth. Therefore, food-material forced past the rounded 
 point of contact, and lying loosely in the inter-proximate 
 space, and upon this rounded and tolerably firm gum septum, 
 is caught and carried away by the gliding motion of food 
 over the axial surfaces of the teeth and over the gum tissue 
 in the act of chewing. This is facilitated greatly by wide 
 buccal and lingual inter-proximate embrasures, which allow 
 the food to glide through them during mastication. In this 
 way the proximate surfaces of normally well-formed teeth are 
 kept free from lodgments as long as the gum septum retains 
 its normal form and firmness. In many individuals of middle, 
 or advanced age, the points of proximate contact become 
 much worn and flattened by rubbing on each other during 
 mastication. From this cause they often become so broad as 
 to hold food-material firmly between them, which is gradually 
 forced against the gum septum, causing its absorption, and 
 forming a pocket for the lodgment of debris, and thus gives 
 rise to serious difficulties. Facets formed by inter-proximate 
 wear may be found in any collection of teeth. Exceptionally 
 cases are met with in which the teeth stand so widely apart 
 that they are self-cleaning. The form of the inter-proximate 
 space is very variable. The forms best suited to the mainte- 
 nance of the health of the teeth and gums are so important to 
 the student of operative dentistry that they should be very 
 closely studied. It is best studied in skulls in which the teeth 
 are all present, by careful selection and arrangement of teeth 
 with their roots in wax, gutta-percha, or plaster, to hold them 
 in normal relation to each other, and by careful consideration 
 of the forms of the proximate surfaces of the teeth together 
 with their relative positions. 
 
 THE ALVEOLAR PROCESS AND ALVEOLL 
 
 ■ — 196. The alveolar process is the projecting portion 
 of the maxillarv bones within which the roots of the teeth 
 
ngm^BUM 
 
 Fig. 135. Fig. 136. 
 
 Fig. 132 (Pars. 19.1, 195). — The Form of the Inter-Pkoximate Contact from 
 Buccal to Lingual of the Upper Teeth. The occlusal surfaces of the teeth are 
 ground away vmtil the contact-points are reached, and then the outlines are accu- 
 rately drawn in silhouette, a, Incisors; b, bicuspids; c, molars. 
 
 Fig. 133 (Pars. 194, 195).— The Form, Bucco-Lingually of the Inter-Proxi- 
 mate Contact of the Lower Molars and Bicuspids. The occlusal surfaces of 
 the teeth are ground away until the contact-points were reached and the outlines 
 accurately drawn in silhouette, a, Contact of th^ bicuspids; b, contact of the sec- 
 ond bicuspid and first molar; c, contact of the first and second molars; d, contact 
 of the second and third molars. 
 
 Fig. 134 (Pars. 194, 19s). — The Form, Occluso-Gingivally, of the Inter- 
 Proximate Contact and of the Inter-proximate Spaces between the Upper 
 Incisors, a, Alveolar process. 
 
 Fig. 135 (Pars. 194, 195). — The Form, Occluso-Gingivally, of the Inter- 
 Proximate Contact and of the Inter-proximate Spaces between the Bicus- 
 pids and Molars of the Upper Jaw. a, Alveolar process; b, bicuspids; r, 
 molars. 
 
 Fig. 136 (Pars. 194, 195).— The Form, Occluso-Gingivally, of the Inter- 
 Proximate Contact and of the Inter-proximate Spaces between the Lower 
 Bicuspids and Molars, a. Alveolar process; b, bicuspids; r, molars. 
 
THE ALVEOLAR PROCESS AND ALVEOLI. 147 
 
 are lodged in alveoli, or sockets, accurately fitted to their 
 surfaces (Figs. 137 and 138). The form of the alveolar 
 process seems to depend on the teeth, the conformation of 
 their roots, and their arrangement in the arch. If any teeth 
 are misplaced, or from any cause stand out of the regular and 
 normal line, the alveolar process is formed about their roots in 
 this irregular position. Also, when teeth are lost, the alveolar 
 process mostly disappears by absorption, and the remaining 
 portions of the alveoli are filled with bone. 
 
 197. Normally, the alveolar process envelopes the roots 
 of the teeth to within a short distance of the gingival line 
 (Figs. 131 and 139), varying from one to three millimeters in 
 the young adult. This distance increases somewhat with in- 
 creasing age. The borders of the alveolar process are reduced 
 to a thin edge about the necks of the teeth on both the labial 
 and lingual sides of the incisors and cuspids of the upper jaw. 
 About the lingual sides of the necks of the bicuspids and mo- 
 lars the borders are also reduced to a thin edge, becoming 
 slightly thickened about the second and third molars, especi- 
 ally the latter. On the buccal sides of these, a thickening of 
 the immediate borders of the alveolar process, in the form of a 
 marked ridge, begins about the first or second bicuspid, more 
 commonly between these two, and extends to the distal of the 
 third molar (Fig. 131, a). This ridge varies in different exam- 
 ples, from a very slight thickening of the immediate border to 
 a thickness of two or three millimeters. It forms a border 
 standing squarely out from the necks of the teeth. The alveo- 
 lar process then thins away so that, in many instances, the buc- 
 cal roots of the teeth, especially the mesial root of the first 
 molar, have but a thin covering of bone. 
 
 198. Anteriorly, the bony covering of the roots of the 
 upper incisors presents much variety. In some examples, the 
 middle portion of the roots has but a slight covering of bone, 
 but more generally it is progressively thickened from the neck 
 to the apex. The roots of the cuspids are prominent toward 
 the lip, and, for most of their length, have only a thin bony 
 
148 THE ALVEOLAR PROCESS AND ALVEOLI. 
 
 covering, and this forms a ridge along the hne of the root, 
 which mav easily be traced with the finger through the soft 
 tissues of both the gum and lip. In many instances, the bony 
 covering is entirely wanting for a little space near the middle 
 of the length of the root of the cuspid, the buccal root of the 
 first bicuspid, the mesial root of the first molar, and, occasion- 
 ally, of other teeth. 
 
 199. On the lingual side of the upper teeth (Fig. 139) 
 the progressive thickening of the alveolar process, from the 
 border toward the apex of the root, is much greater, so that 
 the roots of the teeth seem to lie toward the labial and buccal 
 side of the alveolar process (Fig. 137). Even the large lingual 
 root of the upper first molar, diverging strongly to the lingual, 
 seldom forms a ridge or prominence of the process covering 
 its lingual surface. 
 
 200. The anterior palatine foramen is in the median 
 line just behind the central incisors (Fig. 139). It is funnel- 
 shaped, with a broad opening to the palatine surface of the 
 bone. The bone is often quite thin between this and the roots 
 of the central incisors. The posterior palatine artery runs 
 in a deep groove in the surface of the bone, very close to the 
 apex of the lingual roots of the upper third and the upper 
 second molar. This artery is occasionally wounded, or cut, 
 in efforts to extract the roots of these teeth. 
 
 201. In the lower jaw the immediate borders of the 
 alveolar process, on the labial sides of the incisors, are rather 
 thicker than in the upper jaw, often amounting to a decided 
 ridge. This, however, thins away rapidly, so that the middle 
 portion of the root has but a thin covering of bone. At the 
 cuspid the border of the alveolar process is very thin, but a 
 gingival ridge, corresponding with that of the upper jaw, 
 though not so prominent, begins at about the first or second 
 bicuspid and runs to the second molar. This thins away over 
 the middle of the length of the roots of the bicuspids and first 
 molar. At the second lower molar, the rising of the external 
 oblique ridge for the formation of the anterior border of the 
 
Fig. 137- 
 
 Fig. 138. 
 
 Fig. 139. 
 
 Fig. 137* (Par. 196).— Horizontal Section of the Alveolar Process and 
 Roots of the Teeth of the Upper Jaw, showing the roots of the teeth in posi- 
 tion. 
 
 Fig. 138* (Par. 196). — Horizontal Section of the Alveolar Process and 
 Roots of the Teeth of the Lower Jaw, showing the roots of the teeth in posi- 
 tion. 
 
 Fig. 139* (Par. 197). ^The Teeth and Lingual Portion of the Alveolar 
 Process of the Upper Jaw, and the Bones of the Roof of the Mouth. 
 
 ^Illustration, actual size. 
 
THE ALVEOLAR PROCESS AND ALVEOLI. 15T 
 
 coronoid process (Fig. 131, b) causes a thickening of the buc- 
 cal bony covering of the root, while at the third molar this 
 ridge rises to a level with the border of the alveolar process, 
 making the bony covering on the buccal side of the root about 
 one-fourth of an inch thick (Fig. 138). This is of importance 
 with reference to the extraction of the roots of this tooth. In- 
 deed, the second and third molars of the lower jaw are fixed in 
 alveoli, hollowed out in the lingual side of the body of the 
 bone rather than in a process or ridge on the bone, as with 
 the teeth anterior. 
 
 202. On the lingual side of the lower anterior teeth 
 the border of the alveolar process is a smooth, thin edge, and 
 the covering of bone over the roots progressivelv thickens 
 toward their apexes. In this portion the process is high, and 
 the labio-lingual thickness is only sufficient to envelope the 
 roots of the teeth and give them support (Figs. 140 and 142). 
 From the first bicuspid backward the height of the alveolar 
 process diminishes rapidly, and the line of the dental arch and 
 of the alveoli of the teeth passes diagonally across the line of 
 the curve of the body of the bone, from the buccal side at the 
 first bicuspid to the lingual side at the third molar, and sinks 
 into the body of the bone (Figs. 140 and 142). The border of 
 the alveolar process remains thin as far as the first or second 
 molar, but the bony covering of the roots is rapidly thickened 
 toward their apexes. 
 
 203. This is caused largely by the thickening of the body 
 of the bone, produced by the rise of the mylohyoid ridge 
 (Fig. 142, a), which begins in front below the apexes of the 
 roots and rises progressively backward nearly to the border of 
 the alveolar process at the third molar. The greatest thickness 
 is oyer the lingual side of the apical half of the roots of the sec- 
 ond molar, and of the crossing of the lingual side of the 
 coronal half of the roots of the third molar. At the third molar 
 this ridge is thinner, and at the distal angle often very slight, 
 while the lingual covering of the roots of the tooth may be 
 verv thin below this ridge. Therefore, it is usually easy, when 
 
152 THE PERIDENTAL MEMBRANE. 
 
 necessary in extracting, to force the roots of the lower third 
 molar to the lingual and distal with a level suitably arranged 
 against the crown of the second molar, as with the Physic's 
 forceps, or an elevator. 
 
 204. The borders of the septa of the alveoli of the roots 
 of the anterior teeth are rounded, or arched labio-lingually, 
 but this diminishes rapidly from the cuspid backward. Be- 
 tween the molars it is a straight line, or presents but a slight 
 concavity, so that the highest points of the border of the 
 alveolar process are on the buccal and lingual surfaces, or at 
 the angles, of the necks of these teeth, which is important in 
 fitting bands of crowns or any similar processes. 
 
 205. The alveolar process is composed of an outer and 
 an inner plate of moderately compact bone, and between 
 these, very open cancellous or spongy bone ; so that in young 
 persons it may be forced more or less to one side, or bent out 
 of position, without definite fracture. The outer compact plate 
 forms the outer surface of the bone, and the inner plates line 
 the alveoli of the teeth. These latter are very thin, and sup- 
 ported on all sides by the cancellous structure. In the lower 
 jaw the substance of the bone is more compact and stronger, 
 than in the upper, especially about the molar teeth, where the 
 alveoli are in the substance of the body of the bone. 
 
 THE PERIDENTAL MEMBRANE. 
 
 206. The peridental membrane invests the roots of 
 the teeth from the gingival line to the apexes of the roots like 
 a sack. It lines every part of the alveoli, and, passing over the 
 gingival margins, is continuous with the periosteum and gums 
 covering the outer plate of the alveolar process. It is one 
 membrane, attached on one side to the root of the tooth, and 
 on the other to the inner wall of the alveolus. It is composed 
 of connective tissue which supports an abundant supply of 
 blood-vessels, nerves and lymphatics. With these are inter- 
 mingled strong fibres of white fibrous tissue which pass from 
 the cementum of the root of the tooth to the bony walls of the 
 
Fig. 140. — Actual size. 
 
 Fig. 141. — Actual size. 
 
 Fig. 140 (Par. 202).^Lower Teeth and Maxilla, as seen from above. 
 Fig. 141 (Par. 210). — The Labial and Buccal Aspect of the Teeth and 
 Gums of the Upper Jaw. 
 
THE GUMS. ' 155 
 
 ■ alveolus. The ends of these are built firmly into each, forming 
 a strong attachment of the root to its alveolus. In childhood 
 and youth, this membrane is comparatively thick, and allows 
 considerable motion of the tooth in its socket. As age ad- 
 vances, it becomes thinner and the motions of the teeth are 
 more restricted. A bundle of nerves and one or more arteries 
 enter the alveolus near the apex of the root (the apical space), 
 and, subdividing, several arterial twigs and nerve bundles pass 
 toward the gingiva, while others enter the apical foramen and 
 pass to the pulp of the tooth. Also, the cancellous portion of 
 the bone forming the alveolar process is richly supplied with 
 blood-vessels and nerves, and these enter the alveolus and peri- 
 dental membrane from all sides. This gives the peridental 
 membrane a very rich collateral circulation. At the gingivae, 
 the blood-vessels become continuous with those of the perios- 
 teum and gums.* 
 
 THE GUMS. 
 
 207. The gums are the soft tissues covering the alveolar 
 -processes and investing the necks of the teeth. They are com- 
 posed of connective tissue containing many white fibres 
 intermingled, forming a firm membranous mass, continuous 
 with the periosteum beneath, and with the peridental mem- 
 brane at the necks of the teeth. They are covered with a 
 strong outer coat of squamous epithelium. They are richly 
 supplied with blood-vessels and nerves ; under normal con- 
 ditions they are not very sensitive to pressure or moderate 
 violence, but in pathological conditions they may become very 
 sensitive. 
 
 208. On the labial and buccal side of the alveolar pro- 
 cess the gums (Fig. 136) are thin and firm near the necks of 
 
 the teeth and strongly attached to the periosteum. As they 
 pass from the necks of the teeth toward the base of the alveolar 
 ridge they become softer, lose their close attachment to the 
 
 * For the details of this subject the student is referred to the 
 author's treatise on "The Histological Characters of the Periosteum 
 and Peridental Membrane." 
 
156 THE GUMS. 
 
 periosteum, and become merged into the mucous membrane of 
 the Hps and cheeks. In the passage from the gums to these 
 mucous surfaces several loose folds are formed, the most no- 
 table being the frenum labium of the upper jaw at the 
 median line, passing from near the inter-proximate space of 
 the central incisors to the median line of the upper lip. A 
 similar, though less prominent fold connects the median line 
 of the lower lip with the gums. Occasionally, folds of less 
 prominence are seen in the neighborhood of the bicuspids and 
 first molars. 
 
 209. On the lingual side of the arch, in the lower jaw, 
 the conditions are much the same. The gums are firmly ad- 
 herent to the periosteum near the teeth, but lower down are 
 merged into the mucous membrane of the floor of the mouth. 
 The median line of the tongue is connected with the median 
 line of the gums by a strong fold, known as the frenum lin- 
 guae. As an abnormal congenital condition this is sometimes 
 connected so near the tip of the tongue as to prevent its pro- 
 trusion over the teeth, constituting the condition known as 
 tongue-tied. This is generally corrected by the muscular 
 efforts of the tongue, which stretch the membrane sufficiently 
 to accommodate its motions. 
 
 210. On the lingual side, in the upper jaw, the gums 
 (Fig. 127) are usually of greater extent and thicker. They 
 cover the entire roof of the mouth, to the conjunction of the 
 hard and soft palate, as a hard dense layer. In the anterior 
 portion, a series of irregular ridges, known as the rugae, radi- 
 ate from the median line toward both sides, stopping short of 
 the gingivae. In a large collection of examples almost innu- 
 merable forms of these rugae may be noted. 
 
 211. The gingiva, or gingivae, is that portion of the 
 gum tissue investing the neck of the tooth crownwise from the 
 attachment of the peridental membrane at the gingival line 
 (Fig. 143). It is also termed the free margin of the gum^ 
 The length of the gingivae, from the line of attachment to the 
 neck of the tooth, varies in different teeth in the same mouth, 
 
Fig. 142. — Actual size. 
 
 Fig. 143- 
 
 Fig. 142 (Par. 202). — Lingual Surface of the Left Half of the Lower 
 Maxilla and Teeth, a, Myloiiyoid ridge; b, inferior dental foramen. 
 
 Fig. 143 (Par. 211). — Outlines of a Section of a Central Incisor, cut 
 Lengthwise Labio-Lingually, with its alveolus and appendages showing the re- 
 lation of the different parts, a, Crown of the tooth; b, root; c, c, bone; d, d, 
 alveolar process; e, c, peridental membrane; f, f, gums; g, g, gingivae, or free 
 margin of the gums; /;, gingival line; the portions of the crown included within the 
 dotted lines i shows the portion of the proximate surfaces covered by the inter- 
 proximate gingivae in normal conditions. 
 
THE GUMS. 159 
 
 and in different adults, from about one to about four millime- 
 ters. It is often much greater in young persons, but the length 
 usually diminishes as age advances. The free margin fits 
 around the neck of the tooth closely, but a thin, flat instrument 
 is easily passed between it and the tooth to the attachment at 
 the gingival line. As the gingival line of the tooth is at the 
 border of the enamel, or at the junction of the enamel and 
 cementum, it follows that the gingivae inclose the immediate 
 gingival border of the enamel, and cover this part of the crown 
 of the tooth. In young persons, we often see one-half of the 
 length of the crowns of the teeth buried in the gingivae even 
 after the teeth are regarded as fully in place. As age advances, 
 the gingivae become shorter, showing more of the crown, and 
 finally recede to very near the gingival line. 
 
 212. The gingivae also fill the inter-proximate spaces 
 in the form of septa passing between the teeth from labial, 
 or buccal, to lingual. This portion of the gingivae is much 
 longer than that on the labial and lingual surfaces of the 
 teeth (Figs. 136 and 143). In normal conditions it reaches 
 from the gingival line to the contact-point between the teeth, 
 completely filling the space and preventing accumulations of 
 debris. The form presented by the gingivae on the labial and 
 buccal surfaces is a, series of imperfect semi-circles with the 
 concavity toward the occlusal surfaces of the teeth, and with 
 the points of junction of these extending into and filling the 
 inter-proximate spaces (Fig. 141). On the lingual side of the 
 arch, the conditions are much the same, but the points of the 
 gingivae between the teeth are less prominent (Fig. 27). As 
 age advances and the gingivae recede toward, or even to the 
 gingival line, the septa of soft tissue fail to fill the inter-proxi- 
 mate spaces. This may induce pathological conditions by 
 affording space for lodgment of debris in pockets, which 
 favors fermentation. A like condition is also induced fre- 
 quently by a faulty form of proximate contact, or through the 
 flattening of the contact points by wear, which allows food to 
 be forced into the inter-proximate space, and break down the 
 gum septum by its pressure. 
 
 12 
 
INDKX. 
 
 'the numbers refer to the paragraphs. 
 
 Alveolar process 196 
 
 " " — at the buccal side of the lower third molar. . 201 
 
 " " — bone forming the 205 
 
 " " — borders of 197 
 
 " " — buccal ridge 197 
 
 " " — lower labial portion 201 
 
 " " " lingual portion 202 
 
 " " — relation of the mylohyoid ridge. , 203 
 
 " " " " oblique ridge 201 
 
 " " — septa of the 204 
 
 " " — upper labial portion 198 
 
 " " " lingual portion 199 
 
 Alveoli • • 196 
 
 " — relation of the roots of the teeth 197 
 
 Angles — of the teeth, how named 7 
 
 " " surfaces of the teeth, how named 7 
 
 Apical foramen 153 
 
 Apex of the root defined 3 
 
 Arrangement of the teeth 187 
 
 Bell-crowned teeth 14 
 
 " " " — inter-proximate spaces 194 
 
 Bicuspids 41 
 
 " — buccal surface of the lower first 57 
 
 " "' " " " second 63 
 
 " " " " upper first 46 
 
 " " " " " second 52 
 
 " — distal surface of the lower first 58 
 
 " " " '"' " second 64 
 
 " " " " upper first 49 
 
 " "■ '■' " " second 52 
 
 " ^grooves of lower first ^ . . . 54. 55 
 
 . " " " '■ second 62 
 
 " " '■' upper first 45 
 
 " "■ " " second 51 
 
 " — lingual surface of the lower first 59 
 
 '■ • " "■ '■ " second 63 
 
 " " " " upper first 47 
 
 " '•■ " " " second 52 
 
 161 
 
I 62 INDEX. 
 
 Bicuspids — mesial surface of the lower first 58 
 
 " " " " second 64 
 
 " " '■ upper first 48 
 
 " " " " second 52 
 
 — occlusal surface of lower first 54 
 
 " ■' " '■ second 62 
 
 " " " upper first 42 
 
 " " " " second Si 
 
 — plan of the formation 41 
 
 — root of lower first 61 
 
 " " " second 65 
 
 " " upper first 50 
 
 " " " second 53 
 
 — ridges of lower first 54, 55, 56 
 
 " " " second 62 
 
 " " upper first 43, 44 
 
 " " second 51 
 
 — lower first 54 
 
 " second 62 
 
 - — upper first 42 
 
 " second Si 
 
 Characteristics common to all of the teeth 3 
 
 Cingulum 18 
 
 Color of the deciduous teeth 133 
 
 Contact, proximate 19S 
 
 Crown surfaces 3 
 
 Crowns of the teeth 3 
 
 " " lower incisors 6 
 
 " " deciduous teeth 130 
 
 Cutting edge of the incisors 6 
 
 Curvature of the gingival line 3 
 
 Cusp defined 8 
 
 Cuspid, lower 38 
 
 " " — ridges 39 
 
 " " — similarity to the upper 38 
 
 " " — surfaces ^,8, 39 
 
 " " — root 40 
 
 upper 33 
 
 " '■ — distal surface 36 
 
 " " — labial surface 33 
 
 " " " ridge 33 
 
 " " — lingual surface 34 
 
 " " — mesial surface 35 
 
 " " — ridges 34 
 
INDEX. 
 
 163 
 
 upper 
 
 Cuspid, upper — root 37 
 
 Deciduous first molars a distinct class 129 
 
 " second molars 129 
 
 teeth 128 
 
 " " — by what teeth succeeded 129 
 
 " " — buccal surfaces ^32 
 
 " " — color "^^2 
 
 " " — lingual surfaces 132 
 
 " " — crowns ^30 
 
 " •' — necks 131 
 
 " " — number ^^^ 
 
 " " — roots ^51 
 
 " molars — lower first buccal surface 148 
 
 " " " " bucco-gingival ridge 148 
 
 " " " " cusps 148 
 
 " " " " distal surface I49 
 
 " " " " fossae 141 
 
 "■ " '' " grooves 142 
 
 " " " '' lingual surface I49 
 
 " '■' " " lobes 142 
 
 " " " " mesial fossa I47 
 
 " " " " " surface i49 
 
 " " " '' occlusal surface 141 
 
 " " " " principal fossa 146 
 
 " " " " ridges I43 
 
 buccal surface 138 
 
 bucco-gingival ridge 138 
 
 " cusps 136 
 
 " " " " distal surface 140 
 
 " " " " grooves I35 
 
 " " " " lobes 13s 
 
 " " " " lingual surface 140 
 
 " " " " mesial surface 140 
 
 " " " " occlusal surface I34 
 
 " " " " ridges 13" 
 
 Dental arch •• 187 
 
 " formulae ^ 
 
 Developmental grooves defined n 
 
 " " of the incisors and cuspids 21 
 
 " " " molars 98 
 
 " lines defined 11 
 
 " " of the incisors and cuspids 21 
 
 " " " first upper molar 98 
 
 Dissections ^58 
 
164 INDEX. 
 
 Dissections — instruments necessary for 158 
 
 " of the bicuspids 166 
 
 " " incisors 159 
 
 " " lower molars 179 
 
 " " upper molars 171 
 
 Fissure defined 1 1 
 
 Fissures, how formed 21 
 
 Foramen, apical I53 
 
 Formulas, dental i 
 
 Fossa defined 10 
 
 Frenum labium 208 
 
 lingua: 209 
 
 Gingivse 21 r 
 
 " — inter-proximate spaces 212 
 
 Gingival groove and fissure of the upper lateral incisor 26 
 
 " line, curvature of the 3 
 
 " " defined 3 
 
 " " of the upper central incisor 20 
 
 Groove defined 11 
 
 '' " developmental 11 
 
 " " sulcate II 
 
 "' " supplemental 12 
 
 Gums 207 
 
 " labial and buccal 208 
 
 " lingual of lower jaw 209 
 
 " " " upper jaw 210 
 
 " of what composed 207 
 
 Incisors, lower 29 
 
 " " — developmental lines 30 
 
 " " — difiference between central and lateral 29 
 
 " " — distal surface 30 
 
 " " — form of crown 29 
 
 " " — labial surface 29 
 
 " ■' — lingual surface 30 
 
 " " — linguo-gingival ridge 30 
 
 *' " — mesial surface 30 
 
 " " — roots 31 
 
 " upper central 16 
 
 " " " — distal surface 19 
 
 " " " — developmental lines or grooves 21 
 
 " " " — fissures 21 
 
 " " " — form of crown 16 
 
 " " " — gingival line 20 
 
 " " " — labial surface 17 
 
INDEX. 165 
 
 Incisors, upper central — lingual fossa lo 
 
 pit 21 
 
 " " " " surface 18 
 
 " " " — linguo-gingival fissure 21 
 
 " " " " " ridge 18 
 
 " " " — lobes of crown 21 
 
 " " " — marginal ridges i<^ 
 
 '• " " — mesial surface i9 
 
 " " — root ^- 
 
 lateral ^3 
 
 " " " — distal surface 25 
 
 " " " — division of lingual lobe 26 
 
 " " " — failure of lingual lobe 26 
 
 " " " — general form of crown ^3 
 
 " " — how different from the central 23 
 
 " " " — labial surface 24 
 
 " " " — lingual pit 26 
 
 " " " " surface 26 
 
 " " " — linguo-gingival fissure 26 
 
 " " " — mesial surface 25 
 
 " '■■ " — marginal ridges 26 
 
 " " " — root ^7 
 
 Inclination defined ^9i 
 
 " mesial — of the lower teeth 192 
 
 " " " upper teeth ^91 
 
 Inter-proximate embrasures defined i3> 
 
 " spaces 
 
 " " defined ^3 
 
 " " — relation to the forms of the teeth... i94 
 
 Introduction • • ^ 
 
 Lines — developmental ^ ^ 
 
 " " — of the incisors 21 
 
 Lobes defined -^ 
 
 " of the incisors ^ ^ 
 
 Lingual pit of the lateral incisor 26 
 
 .Linguo-gingival ridge of the incisors 18, 21 
 
 " " " " cuspids 34 
 
 " " groove -^^ 
 
 Long-cusped teeth ^4 
 
 Lobes of the incisors 21 
 
 Man's diet ^ 
 
 Marginal ridges 9 
 
 Mesial surface defined 5 
 
 Measurements of the teeth ^5 
 
 " " " — tables of IS 
 
 194 
 193 
 
1 66 
 
 INDEX. 
 
 Mesial 
 
 Molar, lower first 
 
 inclination of the lower teeth 191, 192 
 
 " upper " 191, 192 
 
 96 
 
 104 
 
 104 
 
 104 
 
 —buccal pit 
 
 groove 
 
 " surface 
 
 — central fossa 
 
 — cusps 100, lOI, 
 
 — developmental grooves 
 
 — distal surface 
 
 — fissures 
 
 — grooves 
 
 — lingual surface 
 
 — mesial surface 
 
 supplemental fosscC 
 
 — pits 
 
 — triangular ridges 
 — root 
 
 nd 
 
 — buccal surface 
 
 — cusps 
 
 — developmental grooves 
 
 — distal surface 
 
 — fissures 
 
 — lingual surface 
 
 — lobes 
 
 — mesial surface 
 
 — occlusal surface 
 
 — pits 
 
 — root 
 
 — supplemental fossae . . . . 
 " grooves . 
 
 — transverse ridges 
 
 — triangular ridges 
 
 — variations of form . . . . 
 
 third 
 
 — buccal surface . . 
 — distal surface . . . 
 
 — five-lobed 
 
 — four-lobed 
 
 — grooves 
 
 — lingual surface. . 
 — marginal ridges 
 
 108 
 102 
 108 
 109 
 
 115 
 112 
 III 
 118 
 114 
 116 
 III 
 117 
 no 
 
 112 
 119 
 112 
 112 
 112 
 112 
 
 113 
 120 
 
 125 
 126 
 124 
 121 
 122 
 126 
 122 
 
INDEX. 167 
 
 Molar, lower third — mesial surface 126 
 
 " —root 127 
 
 " " '■■ — supernumerary cusps 123 
 
 " " " — supplemental fossae 121 
 
 Molar triangle, typical forms '^73 
 
 Molars 66 
 
 — number and names 66 
 
 '' — .upper 67 
 
 Molar, upper first 68 
 
 " " ■' ^buccal surface 78 
 
 '• '■ " — calcifications of lobes 69 
 
 "—cusps 71,72,73.74 
 
 " " " — distal surface 81 
 
 " —fifth lobe 70 
 
 '• " " — fossse 68 
 
 '•' " ■' — grooves 68 
 
 " " " — lingual surface 79 
 
 " " " — lobes 68 
 
 " " " — mesial surface 80 
 
 " " '■ — occlusal surface 68 
 
 '•■ " " — oblique ridge 75 
 
 '• —ridges 7i, 72, 73 
 
 '■ " second 86 
 
 " " " — abnormal forms 87 
 
 " " " — buccal surface 88 
 
 '■ " '■ — central fossa 86 
 
 '.' " " — distal fossa 86 
 
 " " " " surface 88 
 
 " " " — form of neck 89 
 
 " " " — lingual surface 88 
 
 '• " '■' — mesio-buccal ridge 89 
 
 " " " — mesial surface 88 
 
 '■ " — occlusal surface 86 
 
 " " " —roots 90 
 
 '' "' " — three-cusped 86 
 
 " " '• — variations of the disto-lingual lobe 86 
 
 " third 91 
 
 '' " " — buccal surface 93 
 
 " '■■ ■' — distal surface 93 
 
 " " '• — disto-lingual cusp 9i 
 
 " " '■ — irregular forms 9i 
 
 " '■ " — lingual surface 93 
 
 " " " — mesial surface 93 
 
 " " " — multiple roots 94 
 
105 INDEX. 
 
 Molar, upper third — occlusal surface > 91 
 
 " " " — root 94 
 
 " " " — three-cusped 91 
 
 " " " — variations of form 91 
 
 Neck of a tooth defined 3 
 
 Nomenclature • • i 
 
 Number of teeth of man 2 
 
 Occlusal surface defined 4 
 
 Occlusal line 189 
 
 " — relation of the lower and upper teeth 188 
 
 " — relative mesio-distal position of the teeth 190 
 
 Peridental membrane 206 
 
 Proximate contact 195 
 
 " " defined 5 
 
 " surfaces defined 5 
 
 Pulp chamber 152 
 
 " — abnormally long horns 185 
 
 " — conditions which cause diminished size 155 
 
 " — diminished size of, in the adult 154 
 
 " — dissections necessary to show 157 
 
 " — divisions IS3 
 
 " — early formative stages i54 
 
 " — forms 153 
 
 " — in single-rooted teeth 156 
 
 " — lateral openings 184 
 
 " of the upper incisors 160 
 
 " " lower incisors 164 
 
 ■' " upper cuspids 163 
 
 " " lower cuspids 165 
 
 " " upper first bicuspid 167 
 
 " " " second bicuspid 168 
 
 " " lower bicuspids 169 
 
 " " upper molars 172 
 
 " " lower molars 180 
 
 " " deciduous teeth 186 
 
 " — secondary formations 183 
 
 " — shortening of the horns 154 
 
 " — variations in the form 183 
 
 Ridges defined 9 
 
 " — how named 9 
 
 " — marginal 9 
 
 " — transverse 9 
 
 " ■ — triangular 9 
 
 Roots of the teeth defined 3 
 
INDEX. 169 
 
 Roots of the teeth — divisions 3 
 
 Root canal I53 
 
 " "■ — distal, of the lower molars 182 
 
 " " " " upper molars 176 
 
 " " — lateral openings 184 
 
 " " — lingual, of the upper molars I74 
 
 " "■ — mesial, of the upper molars I75 
 
 " " of the bicuspids, lower 170 
 
 " " " " upper first 167 
 
 second 168 
 
 " " " cuspids, lower 165 
 
 " " " " upper 163 
 
 " " " incisors, lower 164 
 
 " " " " upper 161 
 
 " *' " molars, lower 181 
 
 upper 173 
 
 " " — size of, in the incisors 162 
 
 " " — position of, in the upper molars I73 
 
 " "' — upper first molar I73 
 
 " " " second molar I77 
 
 " third molar 178 
 
 " " — variations of the, in the upper molars I77 
 
 Short-cusped teeth 14 
 
 Spaces, inter-proximate I93 
 
 " " defined 13 
 
 Sulcate groove defined ". 11 
 
 Sulcus defined 10 
 
 Supplemental grooves defined 12 
 
 Surfaces, mesial and distal, defined 5 
 
 " occlusal, defined 7 
 
 " of the crown, named 4 
 
 " proximate, defined 5 
 
 Tables of measurements of the teeth 15 
 
 Teeth — arrangement • • 187 
 
 " — number 2 
 
 Thick-necked teeth 14 
 
 Thirds — division of crown into 5 
 
 Tissues of the teeth 2 
 
 Tongue-tied 209 
 
 Transverse ridges defined 9 
 
 Triangular ridges defined 9 
 
 Tubercle defined 9 
 
 Wrinkles defined 12 
 
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