THE TECHNICAL PROCEDURES FILLING TEETH. BY G. V. BLACK, M.D., D.D.S., Sc.D., LL.D. Professor of Operative Dentistry IN Northwestern University Dental School, AND Dean of the Faculty. CHICAGO : THE HENRY O. SHEPARD CO., PRINTERS AND BINDERS. 1899. e Entered, according to Act of Congress, in the year 1899, by Greene V. Black, Chicago, III., In the Office of the Librarian of Congress, at Washington, D. C. PREFACE This book is printed for the students of Northwestern Uni- versity Dental School, and is intended to fill an immediate and pressing want in the particular field to which it is devoted — the technical procedures in filling teeth. It consists of a revision of my lectures of last year on that subject. The reprinting of these was not thought of until after the beginning of the school term of this year and the need of it had become especially manifest. The revision has, therefore, been done very hastily. The book is intended to answer a temporary purpose only; or until a more complete work can be prepared. The absence of illustrations in the book is well supplied in the school work by drawings, blackboard illustrations and lantern slides. Without these much of the matter would be difficult to understand by those unfamiliar with the methods of instruction employed in the school ; but with them, as employed, the need of them in the book is reduced to the minimum. The book is intended for the students of the school, not for the general profession. G. V. B. THE TECHNICAL PROCEDURES IN FILLING TEETH. Introduction. Under the term Operative Dentistry we include all those operations upon the natural teeth and soft parts immediately connected with them that are usually performed by the dentist. But for convenience in teaching, and by common consent, cer- tain operations are consigned to other departments. The extraction of teeth belongs to Oral Surgery ; the preparation of natural teeth, or their roots, for crowns and bridges, belongs to crown and bridge work ; the regulation of irregular teeth to Orthodontia, etc., until today operative dentistry is pretty strictly confined to those operations upon the natural teeth and soft parts immediately connected with them for the repair of damage inflicted by caries, to prevent further caries, and the treatment of diseases resulting from exposure or death of the pulps of the teeth. To this is added that group of diseases of the peridental membrane beginning at the gingival border. The subject matter in this book will be confined to a brief presentation of the technical procedures in filling teeth. No study of pathological conditions will be undertaken ; not even of dental caries, further than a study of the position and forms of cavities, and such observations as may be necessary in the explanation of technical procedures in the preparation of cavities and in filling teeth. The nomenclature relating to cavities and cavity preparation, instruments and instrumentation, will be fully presented. Nomenclature. Nomenclature treats of the system of naming things. Dental nomenclature treats of the terms, or names, used in dentistry. The subject is of first importance, for if we do not know the names by which we call things we will be unable to understand each other in speaking of them. Every profession, business or trade has its special system of naming things pertaining to it. 6 THE TECHNICAL PROCEDURES IN FILLING TEETH. t^. and this nomenclature must be understood before the student can become proficient. In operative dentistry this system of nomenclature is very simple, and comprises but few words. However, these words are used in a fairly wide range of combi- nations that will be very perplexing to the student who has not a good knowledge of them. Every student who has arrived in the senior class should know them perfectly in their whole range of application. He should understand them when spoken by others, and be able to use them freely and correctly in his ordi- nary speech. Otherwise he will be unable to understand his professors or fellow-students as accurately as he should, and thus find his studies more difficult than they otherwise would be. For the most part the words are the same as those used in Dental Anatomy, with which the student should be already familiar. But they are applied differently, and to different subjects. This new application becomes a subject of study. Cavity Preparation. Cavity preparation includes all those operations required in the removal of carious material from cavities formed in the teeth by decay, forming the cavities for the reception of fillings, and such extensions and preparations as will best fit the affected sur- faces of the teeth to resist decay in future. Cavity Nomenclature. Rule : Cavities in the teeth take the names of the surfaces of the teeth in which they occur. We group cavities together according as the decayed sur- faces are similarly situated. A further grouping may also be made into classes, each class including those cavities that require similar treatment. Cavities which occur in the occlusal surfaces of the teeth are called occlusal cavities, and occur in the molars and bicuspids, constituting a group. Cavities occurring in the buccal surfaces of the bicuspids and molars are called buccal cavities, and constitute a group. Cavities occurring in the lingual surfaces of the bicuspids and molars are called lingual cavities. They are not frequent. Cavities occurring in the pr03^imate, or proximal, surfaces of the teeth are called proximate, oKproximal, cavities. These J^OMENCLATURE. 7 are divided into two groups, those occurring in the bicuspids and molars forming one group, and those occurring in the incisors and cuspids forming a separate group ; the forms of the surfaces of these two groups of teeth being so different as to require dif- ferences in consideration and treatment. Each of these groups are again subdivided into mesial cavities and distal cavities. Mesial cavities are those that are in surfaces of the teeth toward the median line as we follow the curve of the arch. Distal cavities are those that are in the surfaces of the teeth furthest from the median line, following the curve of the arch. Cavities occurring in the lingual surfaces of the upper incisors are considered as a separate group, incisor lingual cavities. Cavities occurring in the labial surfaces of the incisors and cus- pids are called labial cavities. In addition to these terms, all cavities which occur in the axial surfaces of the teeth are called axial^ surface cavities. In each of these localities decay has peculiarities in its mode of attack, or there are differences of approach and of instrumen- tation in their preparation for filling that render differences in their consideration necessary. Cavities are also divided into two groups, pit and fissure cavities forming one group, and smooth-surface cavities forming a second group. This constitutes a most important division of cavities of decay, calling for a radical distinction in consideration and treatment. The pit and fissure cavities have their beginning in minute faults in the enamel of the teeth known as pits, formed where three .or more lobes of the teeth join, making imperfect closure of the enamel plates, as upon occlusal surfaces of the bicuspids and molars and the lingual surfaces of the incisors, or at the endings of grooves, as upon the buccal surfaces of the molars. Fissure cavities begin in points of imperfect closure of the enamel plates along the lines of the grooves. These latter may occur along the lines of the grooves of any of the teeth, but are seen mostly in the occlusal surfaces of the bicuspids and molars. Among the groups of cavities all of the occlusal cavities in the bicuspids and molars are, in their beginning, pit or fissure cavities. A part of the buccal cavities in the molars are pit or fissure cavities occurring in the buccal pits or fissured grooves, and part are smooth-surface cavities, occurring in the smooth 8 THE TECHNICAL PROCEDURES IN FILLING TEETH. portion of the enamel of this surface to the gingival of the pit, or in the gingival third. All buccal cavities in the bicuspids are smooth-surface cavities. All labial cavities in the incisors and cuspids are smooth-surface cavities. All lingual cavities in the upper incisors are pit or fissure cavities, and a few fissure cavities occur in the occlusal half of the lingual surfaces of the molars. All proximate, or mesial and distal cavities, whether in the molars, bicuspids or incisors, are smooth-surface cavities. Lin- gual cavities in the gingival half of the molars are also smooth- surface cavities. Pit and fissure cavities occur in surfaces of the teeth that are habitually clean, except as the imperfections of the enamel — pits and fissures — afford places for the lodgment and fermentation of d6bris, which causes the beginning of decay. Therefore, in their preparation for filling they require no extension for preven- tion of recurrence of decay, further than a sufficient opening of the cavity to completely uncover the^ carious area and to find margins sufficiently level and smooth to allow of a good finish of the margins of the filling. Smooth-surface cavities occur in positions in which the surface of the enamel is habitually unclean, and usually begin in the central portion of the unclean area. The injury to the enamel surface tends to spread super- ficially from the central area of first beginning toward the margins of the unclean area. Therefore, such cavities require such extension in their preparation for filling as will include the habitually unclean area within their outline in order to prevent the recurrence of caries. Classification of Cavities. In a classification of cavities it is the intention to group together in classes cavities of decay that require a similar line of treatment in order that these may be more closely asso- ciated. Class I. — Cavities beginning in structural defects in the teeth, as pits and fissures. Class 2. — Cavities in the gingival third — not pit cavities — of the labial, buccal or lingual surfaces of the teeth. Class 3. — Cavities in the proximate surfaces of the incisors and cuspids which do not involve the removal and restoration of the mesial or distal angle. NOMENCLATURE. 9 Class 4. — Cavities in the proximate surfaces of the incisors and cuspids which do require the removal and restoration of the mesial or distal angle. Class 5. — Cavities in the proximate surfaces of the bicuspids and molars. Class i. — Pit and fissure cavities. These cavities are located in the occlusal surfaces of the bicuspids and molars, in the occlusal two-thirds of the buccal surfaces of the molars, in the lingual surfaces of the upper incisors, and occasionally in the lingual surfaces of the upper molars. They are all pit or fissure cavities. They occur in surfaces of the teeth that are habitually clean, except as imperfections of the enamel in the form of pits or fissures afford an opportunity for the lodgment and fermenta- tion of debris which causes the beginning of decay. Therefore, the enamel surface immediately about the cavity being habitually clean, none of them require extension for the prevention of the recurrence of decay in their preparation for filling. All that is required is to remove sufficient enamel to completely uncover the carious area and to obtain margins sufficiently level and smooth to give opportunity for a perfect finish of the filling. Classes 2, 3, 4 and 5 are all smooth-surface cavities. They all occur in positions in which the surfaces of the teeth are unclean habitually, and usually have their beginnings in the central por- tion of the unclean area, with a tendency of the carious action to spread superficially upon the enamel surface. They, therefore, all agree in requiring extension for the prevention of the recur- rence of decay in such a way as to include within the lines of the enamel margins of the prepared cavity all of that portion of the surface especially liable to decay. With respect to manipulative procedures, each of these classes has its especial peculiarities. For instance. Class 2, which includes all buccal, labial and lingual cavities, requires in most cases the use of the Hatch clamp to extend the rubber dam sufficiently to the gingival, and the method of instrumenta- tion in their preparation is peculiar to them. Classes 3, 4 and 5 all agree in requiring the use of the separator to give room for finishing, because all are proximate cavities, but each of these classes presents especial peculiarities in manipulative procedure which will receive attention later. 10 THE TECHNICAL PROCEDURES IN FILLING TEETH. Nomenclature of the Int crna1-f*ar ts of Cavities. In chiving the nomenclature of the internal parts of cavities, the rules, and illustrations of each rule, will be given. Students should not burden themselves with memorizing these illustra- tions, or lists, for if they know the rules and their application they can make complete lists at any time. This should be prac- ticed until the walls and angles of any cavity can be named at sight without hesitation. Rule : The surrounding walls of a cavity take the names of those surfaces of the teeth adjoining the surface decayed toward w^hich they are placed. Illustration : Occlusal cavities have — A mesial wall, A buccal wall, A distal wall, A lingual wall, And — A fifth wall, which is called the pulpal wall, or floor of the cavity. Rule : That wall of a cavity which is to the occlusal of the pulp and in a plane at right angles to the long axis of the tooth, is called the pulpal wall or floor. In case the"^pulp of the tooth is removed and the cavity thus extended to the floor of the pulp chamber it is called the sub-pulpal wall. Illustration : Buccal and lingual cavities have — A mesial wall, An occlusal wall, A distal wall, A gingival wall. And — A fifth wall, called the axial wall. Rule : That wall of a cavity in an axial surface of a tooth that covers the pulp is called the axial wall. If the pulp of the tooth is removed the cavity is extended to include the pulp chamber and the wall takes the name of the w^all of the pulp chamber. Simple mesial or distal cavities (proximate cavities), in the bicuspids and molars, have — NOMENCLATURE. 11 A lingual wall, A buccal wall, A gingival wall, An occlusal wall, And — An axial wall. But as mesial and distal cavities are usually prepared they become mesio-occlusal (or disto-occlusal) cavities (complex cavities), the occlusal wall is missing and a step is cut in the occlusal surface. Rule : When one of the surrounding walls of a cav- ity is missing by reason of extension of decay, or by extension by cutting in the preparation for filling, so as to involve another surface, a complex cavity is formed and the remaining walls extend to the new surface involved. Therefore, when a mesial or a distal cavity in a bicuspid or molar has involved the occlusal surface, the buccal and the lin- gual walls will terminate at the occlusal enamel margin. The axial wall will also extend to the occlusal enamel margin if no step has been formed, and the occlusal wall will be missing. When a step has been formed its walls will be named as in a simple occlusal cavity, except that that wall toward the cavity from which the step is formed will be missing. Therefore, mesio-occlusal (or disto-occlusal J cavities in the bicuspids and molars have in the proximate portion (mesial or distal) — A gingival wall, A buccal wall, A lingual wall. And — An axial wall. In the step portion — A mesial Tor distal) wall, A buccal wall, A lingual wall. And — A pulpal wall. Notice here that in mesial cavities the mesial wall of the step portion will be missing, and in distal cavities the distal wall of the' step portion will be missing. 12 THE TECHNICAL PROCEDURES IN FILLING TEETH. In a mesio- or disto-occlusal cavity in a molar or bicuspid in which the pulp is removed, the pulpal and axial walls are removed. The floor of the pulp chamber becomes the sub- pulpal wall of the cavity. This is usually distinct from the gingival wall, because it is on a different level. Therefore, a mesio- or disto-occlusal cavity in a molar or bicuspid with pulp removed has — A buccal wall, A lingual wall, A gingival wall, A distal (or mesial) wall. And — A sub-pulpal wall. Also some portions of the mesial (or distal) wall of the pulp chamber will remain next to the gingival wall as a mesial (or distal) wall. In a bicuspid or molar with a single broad pulp canal the pulp chamber has no floor, and of course there will be no sub-pulpal wall. Proximate cavities in the incisors and cuspids, on account of the wedge-like or triangular form of these surfaces, have but three surrounding walls — A labial wall, A lingual wall, A gingival wall, And — An axial wall. When in incisor or cuspid proximate cavities the incisal angle becomes involved so that its removal is required, a complex cavity is formed by cutting an incisal step. There is in this case no change in the naming of the walls of the proximate portion of the cavity, as no one of the walls named has been completely removed. But the step portion will have — A lingual wall, A labial wall, A mesial (or a distal) wall. And — A pulpal wall. Labial and lingual cavities in the incisors and cuspids have — A mesial wall, A distal wall, NOMENCLATURE. 13 A gingival wall, and An incisal wall. Angles of Cavities. In naming cavity walls and angles the typical idea of the cavity is that of a cuboid space or the form of a box. And no matter how irregular the actual form of the cavity, its walls and angles are named as if the form were regular. Each simple cavity has two sets of line angles, and one set of point angles. Rule : All line angles are formed by the junction of two walls along a line, and are named by combining the names of the walls joining to form the angle. They are, therefore, named in two terms. Rule : All point angles are formed by the junction of three walls at a point, and are named by joining the names of the walls forming the angle. They are, there- fore, named in three terms. In simple cavities one set of line angles are formed by the junction of the four surrounding walls with each other, and form lines which run from the enamel margin to the floor or pulpal wall in occlusal cavities, or to the axial wall in axial cavities. A second set of line angles are formed by the junction of the sur- rounding walls with the floor, or pulpal wall in occlusal cavities, or with the axial wall in cavities in the axial surfaces of the teeth. These are called the pulpal line angles, and the axial line angles, respectively. The point angles are formed in those corners where the one set of line angles meet the other set at the corners of the cavity. The broader rule for naming angles to which there is but a single exception, is : Rule : All angles of cavities are named by combin- ing the names of the walls joining to form the angle. Illustrations : (Each angle named is formed by the junction of the walls, the names of which enter into tlie name of the angle. ) Occlusal cavities have — A mesio-buccal angle ^ A mesio-lingual angle I , , . . ,. , , r ; ist set. )■ Line angles. A disto-buccal angle j ' A disto-lingual angle 14 THE TECHNICAL PROCEDURES IN FILLING TEETH. A bueco-pulpal angle -i A lins^uo-pulpal angle I , , ^^ , , A • 1 1 1 Md set ^ Pulpal line angles. A mesio-pulpal angle j if s A disto-pulpal angle J A mesio-bucco-pulpal angle ^ A disto-bucco-pulpal angle I A mesio-linguo-pulpal angle f ^'^^^'^ angles. A disto-linguo-pulpal angle J In case the pulp is removed the pulpal wall is removed, and the floor of the pulp chamber becomes the sub-pulpal wall of the cavity, and the pulpal angles become sub-pulpal angles. A buccal or a lingual cavity in molars or bicuspids has — A mesio-gingival angle ^ A disto-gingival angle I A mesio-occlusal angle j ^^^ set of line angles. A disto-occlusal angle J And — An axio-gingival angle ^ An axio-mesial angle I 2d set of line angles, or axial An axio-occlusal angle j line angles. An axio-distal angle J An axio-mesio-gingival angle ^ An axio-mesio-occlusal angle 1 An axio-disto-occlusal angle [ ^^^^^ angles. An axio-disto-gingival angle J A simple mesial or distal cavity in bicuspids or molars has — A linguo-gingival angle ^ A bucco-gingival angle j A linguo-occlusal angle \ ^^^ ^^^ ^^ ^^^^ ^"g^^s. A bucco-occlusal angle J An axio-lingual angle -, An axio-occlusal angle j 2d set of line angles or axial An axio-buccal angle f Hne angles. An axio-gingival angle J An axio-linguo-gingival angle ^ An axio-bucco-gingival angle | An axio-linguo-occlusal angle j' ^°^^^ angles. An axio-bucco-occlusal angle J But in mesial and distal cavities in the bicuspids and molars as prepared for filling, the occlusal wall is generally cut away and a NOMENXLATURE. 15 Step formed in the occlusal surface, forming a complex cavity. In this case the occlusal wall is missing and all of the angles formed by the junction of this wall with others are also missing. Then the step in the occlusal surface has its angles the same as in a simple occlusal cavity, except that the angles pertaining to the missing wall, mesial or distal, are also missing. This is a universal rule with complex cavities. Hence a mesio or disto-occlusal cavity has in its mesial or distal portion — A bucco-gingival angle ) ^^^ ^^^ ^^ ^^^ ^^^j^^^ A linguo-gingival angle An axio-buccal angle An axio-lingual angle j. 2d set of line angles. An axio-gingival angle j An axio-bucco-gingival angle ~i ^^ . . . ,. ^ .^ . , ^ , [ Pomt angles. An axio-lmguo-gmgival angle -• And in the step portion — A mesio- (or disto-) buccal angle "t A mesio- (or disto-) lingual angle * ist set of line angles. A mesio- (or disto-) pulpal angle 1 A linguo-pulpal angle l A bucco-pulpal angle J ^d set of line angles. A mesio- (or disto-) bucco-pulpal angle ] A mesio- (or disto-) linguo-pulpal angle j ^^^"^ angles. And a pulpo-axial angle formed by the junction of the pulpal wall of the step with the axial wall of the mesial or distal cavity. The rule illustrated in the above is universal. A buccal cavity united with an occlusal cavity would also have its pulpo- axial angle. The angles belonging to the occlusal wall of the buccal cavity would be missing, and the angles belonging to the buccal wall of the occlusal cavity would also be missing. This, however, makes no difference whatever with the naming of the remaining angles. If, however, the pulp of the tooth is removed, removing the axial and pulpal walls, the angles with these walls are also removed and the angles of the pulp chamber (sub-pulpal angles) substituted. Labial or lingual cavities in the incisors and cuspids have — A mesio-gingival angle A disto-gingival angle . ,. . .... , I ist set of Ime angles. A mesio-mcisal angle ^ A disto-inclsal angle 16 THE TECHNICAL PROCEDURES IN FILLING TEETH. 2d set of line angles. An axio-gingival angle An axio-mesial angle An axio-distal angle An axio-incisal angle An axio-mesio-gingival angle An axio-disto-ginofival angfle • ^ . . . . ° "^ , ? ^ Point angles. An axio-mesio-incisal angle ; An axio-disto-incisal angle J Mesial and distal cavities in the incisors and cuspids have, on account of their triangular form, but three angles instead of four. They have : A labio-gingival angle -\ A linguo-gingival angle C ist set of line angles. *An incisal angle J An axio-labial angle ^ An axio-lingual angle y 2d set of line angles. An axio-gingival angle 3 An axio-labio-gingival angle "\ An axio-linguo-gingival angle [- Point angles. An axio-incisal angle ) In mesial and distal cavities in the incisors and cuspids involving the loss of the incisal angle, or corner of the tooth, the incisal angle and the axio-incisal angle will be missing and the incisal step when formed will have its set of angles. These are — A pulpo-distal (or mesial) angle ^ A pulpo-lingual angle A pulpo-labial angle A pulpo-axial angle J A mesio- (or disto-) labial angle) , ^ ,. , ^ ,. /,. 1 , ^ 2d set of Ime angles. A mesio- (or disto-) Imgual angle j A mesio- (or disto-) labio-pulpal angle > ist set of line angles. 1- N 1- 11 1 /■ Point angles. A mesio- (or disto-) linguo-pulpal angle j While all angles are theoretically and actually present as named, and according to the rules given and illustrated, these incisal steps are so narrow that it would rarely be desirable to *NoTE. — The incisal angle given here is the one exception to the rule of naming cavity angles. If the rule were followed strictly it would be the labio-lingual angle, for it is formed by the junction of these two walls. However, the name, incisal angle, can not be mistaken. NOME\XLATURE. 17 name the point angles in any directions for cavity preparation or in cavity description. These Hsts of cavity angles may seem long and tedious, but it must be remembered that in any directions for the preparation of cavities, or in cavity descriptions, very few of them need to be mentioned. However, the student should be able to under- stand just what is meant when any one of them is mentioned, or be able to name any of them in any cavity. This he will not do by memorizing lists that are given, but by so learning the appli- cation of the rules as to be able to name at once any angle of any cavity. Nomenclature of Enamel Margins. The enamel margin includes the whole outline of the cavity and is equivalent to the marginal lines of the cavity. In this sense the enamel margin marks the oudines of the cavity. The Cavo-surface angle of a cavity, or of the enamel, is the angle formed by the juhction of the wall of the cavity with the surface of the tooth. The cavo-surface angle of a cavity will ordinarily be of enamel ; under some unusual conditions it may be of dentin ; or in buccal and labial cavities that extend beyond the gingival line the cavo-surface angle will be of cementum. The term cavo-surface angle is used especially when it is desired to indicate the form to be given this angle in any particular portion of the enamel margin, or oudine of a cavity ; as, the buccal cavo-surface angle was beveled. The dento-enamel junction is the line of junction of the dentin and enamel as it appears in the walls of cavities. The enamel wall is that portion of the wall of a cavity which consists of enamel. It includes the thickness of the enamel from the dento-enamel junction to the cavo-surface angle. The dentin wall is that portion of the wall of a cavity which consists of dentin. The Planes of the Teeth and the Inclination of Cavity Walls. The teeth have three planes which may frequently be used to advantage in cavity description, and especially in speaking of the inclination of cavity walls. 2 18 THE TECHNICAL PROCEDURES IN FILLING TEETH. The horizontal plane is at right angles to the long axis of the tooth, and may be supposed to cut through the crown at any point in its length. The axio-mesio-distal plane, or the mesio-distal plane, passes through the tooth mesio-distally parallel with its long axis. The axio-bucco-lingual plane, or the bucco-lingual plane, passes through the tooth bucco-lingually parallel with its long axis. In the incisors and cuspids this is the labio-lingual plane. The inclination at which walls of cavities are cut, or of the dentin wall and the enamel wall, when each is specifically mentioned, is reckoned from these planes of the teeth. When great accuracy of statement is desired the inclination may be given in centigrades. More generally the term outward inclination, or inclined outward, is used, with some word expressing degree, as slightly, strongly, etc. In this use of words the wall of the cavity mentioned is always inclined away from the plane of the tooth in passing from within outward. The bevel of the cavo-surface angle is always reckoned from the plane of the enamel wall. The Use of Divisions of the Surfaces of the Teeth in Cavity Description. Whenever we wish to indicate in words the portion of a sur- face of a tooth involved in decay, or the extent of a cavity, we may conveniently do so by an imaginary division of the surface decayed into thirds, fourths or fifths. This division may be mesio-distally upon a buccal, lingual, or occlusal surface, or occluso-gingivally upon a buccal, lingual, mesial, or distal sur- face, or it may be bucco-lingually upon an occlusal, mesial, or distal surface. In other words, the divisions may be made upon any one of the planes of the tooth. For instance, of a cavity in a buccal surface we may say it involves the middle third mesio-distally and the gingival third occluso-gingivally. Or if the cavity is broader we may say it involves the middle three-fifths mesio-distally and the gingival half of the surface occluso-gingivally. In this use of words it must be borne in mind that when the adverbial form is used, it indicates direction. Mesio-distally CAVITY PREPARATION. 19 means from mesial to the distal. Bucco-lingually means from the cheek toward the tongue, etc. This use of words is so sim- ple that it should only require mention to be perfectly under- stood. Surgeons continually use this plan in speaking of the location of fractures of the bones. As, for instance, the hum- erus was broken at the junction of the middle and upper third, or the radius was broken in the middle of the lower third, etc. There is no need of any specific rules for this use of words in dividing the surfaces of the teeth in cavity descriptions, as any divisions intelligently made will be readily understood, and the portions of the surface involved quite accurately described. If it is said that a cavity in the mesial surface of a first lower molar extends from the occlusal surface to the junction of the gingival and middle third, and bucco-lingually from the mesio-buccal angle to the junction of the middle and lingual third, it should be understood. The same conception of the cavity should be obtained if it is said that it occupies the buccal two-thirds bucco- lingually, or that it occupies the buccal and middle third. There is scarcely any limit to the use that may be made in cavity descriptions of these divisions of the surfaces of the teeth. Cavity Preparation. GENERAL PRINCIPLES, There are certain fimdamental principles that are general to the e.xcavation of carious cavities in the teeth, the observance of which will simplify and facilitate these operations. Order of Procedure. Obtain, first, the required outline form. Obtain, second, the required resistance form. Obtain, third, the required retention form. Obtain, fourth, the recjuired convenience form. Fifth, remove any remaining decayed dentin. Sixth, correct the form of, and smooth the enamel wall, bevel the cavo-surface angle, and make the toilet of the cavity. The careful observance of this order of procedure by the student will greatly facilitate his operations, lead to more careful consideration of the requirements in individual cases, and will guide him to the use of the approjiriate instrument for the differ- ent parts of the operation. 20 THE TECHNICAL PROCEDURES IN FILLING TEETH. Outline Form is the form of the area of the tooth surface to be included within the outline, or enamel margins, of the fin- ished cavity; the laying out of and cutting to these lines should be the first thing considered and accomplished. In all pit cavi- ties the outline of the cavity will be found by cutting away all enamel overhanging the decayed area, completely uncovering it, and following out any sharp grooves connecting with the cavity to such points as will enable a perfect finish to be given to the margins of the filling when placed. This should always be done before there is any attempt made to remove the decay from the deeper parts of the cavity. As these cavities occur in surfaces of the teeth that are habitually clean, except for lodgments in the pits or fissures in which the decay begins, no further exten- sion for prevention is required. In this class of cavities this work is done generally with chisels and the enamel hatchets. However, in the first opening of pits in which but little decay has occurred, and in following out fissures and grooves, the bur is often the best instrument. In smooth surface cavities, that is, in proximate cavities, and buccal and lingual cavities, which do not begin in pits or fissures, but which occur in the central por- tion of an area of uncleanliness that is habitual, in which the superficial injury to the enamel tends to spread, the laying out of the outline form of cavities is done upon a different princi- ple. In these it is not simply cutting away overhanging enamel for the exposure of the dentin already decayed, but the object should be to include within the outline of the cavity such por- tions of the surface as are especially liable to decay in the future. As decay is liable to occur upon surfaces habitually unclean, and only upon the unclean areas, the whole of the habitually unclean area should be included within the outline of the cavity. This requires a careful study of the conditions surrounding each smooth surface cavity and the extension of the cavity outlines to include the area of the surface that may have suffered superficial injury, or is in danger of decay in the future. This will often require that sound enamel and dentin be cut away to obtain the correct outline form, and is known as extension for the pre- vention of the recurrence of the decay. The study of the case should be made, the outline determined upon, and the cav- ity cut to the outline form required as the first procedure. Resistance Form is that shape given to a cavity intended CAVITY PREPARATION. 21 to afford such a seat for the fiUing as will best enable it to with- stand the stress brought upon it in mastication. Its importance stands in direct relation to the degree of the exposure of the filling to the occlusion and to the strength of the closure of the teeth. It is necessary to provide for a force of from one to two hundred pounds, and in some cases more. The resistance form consists in a flat seat for the filling, cut at right angles with the direction of the stress of mastication, or usually at right angles with the long axis of the tooth. In occlusal cavities, for example, the floor or pulpal wall is to be cut flat and all of the surrounding walls should be cut to definite angles with the pulpal wall. In proximo-occlusal cavities, in which the greatest possible support is needed, the gingival wall of the proximate portion is cut flat, and in the horizontal plane of the tooth, and extended from buccal to lingual into fairly definite corners or angles. The step is also given a flat horizontal seat. Generally this is easily attained by the same instruments and by the same modes of cutting used in gaining the outline form, if the two objects are held strictly in view. Retention Form is the provision for preventing the filling from being displaced. A large part of this is provided for by the resistance form. But it is further required that provision be made that will prevent the filling from being thrown out of the cavity by such lateral or tipping force as may be brought against it. All cavities should be provided with ample retention form, but this provision is required in its more perfect form in mesio or disto-occlusal cavities in the bicuspids and molars. In these the provision is made in the form of a step cut into the occlusal surface, which is more or less dovetailed. In most cavities the retention form is made by so shaping certain of the opposing walls that they will be strictly parallel or slightly undercut in order that when the filling material is thoroughly packed between them it will be securely held in place. This is done variously in different situations. It is to be looked to especially when the outline and resistance form of the cavity has been developed. F"ormerly pits and grooves were much depended upon for this purpose, but have proved delusive, so that latterly it has been required that the form of the walls be such as to perform this function. Convenience Form, though secondary to other points in 22 THE TECHNICAL PROCEDURES IN FILLING TEETH. the formation of cavities, should not be neglected. When the general form of the cavity has been developed, modifications are to be made that will render the form more convenient for packing the filling material. Often by cutting a wall away to a certain inclination the plugger point will reach some portion of the cavity better, or at a more available angle, enabling the operator to pack gold more certainly and more securely in certain impor- tant parts of the cavity. Also such cutting may render the filling so much more convenient as to save time and much wear and tear upon both patient and operator. A second order of convenience form is slight undercuts situ- ated in angles or other parts of the cavity as starting points in packing gold, or that will hold the first portions of the filling material while other portions are being packed, or until the true retention form of the cavity has been filled. The study of the use of these conveniences and the wise placing of them is espe- cially important, as it assists in starting the filling and securing the first portions. These pits and grooves are usually placed in the axio-linguo- gingival and axio-bucco-gingival angles of proximate cavities, and in similar positions in other cavities. Removal of Remaining Carious Dentin. — Generally when the cavity has been cut to form, no carious dentin will remain. But in the larger decays it will often be a question whether or not the pulp will be exposed when all decayed den- tin overlaying it is removed. It is especially an object that we do not cut toward the pulp until the cavity is otherwise well pre- pared, for the reason that if a pulp exposure is found the cavity shall be fully cleaned and ready for the immediate treatment of the pulp in any way indicated. Then when this stage in cavity preparation has been reached, the remaining softened dentin is carefully and completely removed with broad spoon excavators, usually with the 20-9-12. It will often be required that the pulp of a tooth be exposed for the purpose of making an application to destroy it. In all of these cases the overhanging enamel should be removed and the walls of the cavity completely cleaned and so formed as to safely hold the temporary filling, before cut- ting toward the pulp. When all of this has been done and after the rubber dam is securely in place, lift off the remaining decay CAVITY PREPARATION. 23 with spoon excavator 20-9-12, laying the pulp bare. If this is properly done very little pain is induced. Finishing the enamel ^vall and beveling the cavo-sur- face angle of the enamel is the last cutting done in the prepara- tion of a cavity. This should always be done with the rubber dam in place and with all provisions made for the immediate placing of the filling material. The cavo-surface angle of the cavity in every part of its outline should receive especial attention. The plane of the enamel wall should be as nearly as practicable in the line of the length of the enamel rods, or such as will certainly cut more from the outer than the inner ends of the rods, and should be made smooth by a light planing motion of a sharp chisel or enamel hatchet, the motion being in line with the length of the margin. When this has been satisfactorily accomplished the cavo-surface angle of the enamel should be cut to a distinct bevel outward, also by a planing motion of the chisel, enamel hatchet or the gingival margin trimmer, used very lightly. The depth of this bevel should generally not include more than one-fourth the thickness of the enamel wall. The angle of the bevel should be from six to ten centigrades from the plane of the enamel wall. The object is, first, to cut away any loose ends of enamel rods that might afterward fall away and render the margin imperfect ; and, secondly, to strengthen the cavo-surface angle of the enamel as a safeguard against possible checking in packing the filling material. In this last work, two things should be held closely in view. The cavo-surface angle of the enamel is friable and readily broken by violence, and beveling will materially lessen this liability. But the marginal angle of the filling material which covers the bevel must not be made too thin by too great a be\el of the cavo-surfiice angle of the enamel. If so, it will have no strength and will tend to roughen and in this way render the margin imperfect. Therefore, the bevel of the cavo-surface angle of the enamel must not be too great. Finally, the toilet of the cavity is to be made. This con- sists in freeing all of its surfaces from the chips and dust that have accumulated during the excavation. The bulk of this is done, of course, with the chip blower during the progress of the excavating. But there will remain some fine dust upon the 24 THE TECHNICAL PROCEDURES IN FILLING TEETH. walls and margins that can not be removed in this way. It is not well to wash this with any known liquid, for even with the use of pure alcohol, and after drying with the air syringe, some- thing will be left coating the walls which injures them for the purposes intended. The best thing yet devised is thorough wiping, or sweeping, of all parts of the cavity with absorbent cotton or with bits of punk held in the pliers. This should be well done and then the cavity is ready for filling. Rule : No moisture of any kind whatever should enter a cavity after the last of the cutting is done, and if by any accident a portion of the cavity should become w^et, it should be dried thoroughly and then that portion that has been damp should be freshened by cutting away the surface. Instruments and Instrumentation. The cutting instruments required for preparing cavities have been adopted after long and careful study of the needs of stu- dents in school work. The set has been arranged especially with reference to teaching methods of preparing cavities, and for facilitating the actual work. It is such as will be best in learning to do these difficult operations, and it is to this end that they are adopted. Each of the names we apply to instruments has a definite meaning. They are descriptive of the uses, as excavator, plug- ger, separator, or the manner of use, as hand plugger. They describe the form of blades of cutting instruments, as hatchet, hoe, spoon, or they describe the form of the shank, as contra- angle, bin-angle, cow's-horn plugger. Note here especially that there are four classes of names. First, those which denote the purpose, which we call order names, as plugger, excavator ; second, those which denote position or manner of use, sub-order names, as hand or mal- let plugger, enamel hatchet ; third, those which describe the form of point, class names, as hatchet, spoon ; and fourth, those which describe the form of the shank, sub-class names, as bin-angle, contra-angle, cow's-horn or spiral. The names we apply to instruments are classified as follows : Order names. Sub-order names, INSTRUMENTS AND INSTRUMENTATION. 25 Class names, Sub-class names. Order names denote purpose, and answer the question ' ' what for. ' ' Examples : Excav^ators, Pluggers, Separators, Scalers, Clamps, etc. Sub-order names denote the manner or position of use, and answer the question ' ' where or how used ? ' ' and are usually a suffix to an order name. Examples : Hand mallet. Hand plugger, Mallet plugger, Enamel hatchet, Push scaler. Pull scaler, Molar clamp, etc. Class names are descriptive of the working point of the instrument. Examples : Hatchet, Hoe, Spoon, Discoid, Cleoid, Serrated plugger. Smooth plugger, etc. These are also used as suffixes to order names, as in the last two ; and also as in hatchet excavator, hoe excavator, etc. Sub-class names describe the shape of the shank of the instrument. Examples : Mon-angle, Bin-angle, ' Triple-angle, Contra-angle, Cow-horn, Bayonet, etc. These names are often combined for more complete descrip- tions of the instruments named, thus : Mon-angle excavator, or, 26 THE TECHNICAL PROCEDURES IN FILLING TEETH. mon-angle hatchet excavator, bin-angle spoon excavator, etc. In these combinations each name is descriptive of some part of the instrument, or of its uses.^ In addition to these we have adopted formula names -for the cutting instruments that describe each individual instrument so accurately that when learned each one will be known when its formula name is spoken. This is necessary in order that a teacher may be understood when speaking of the uses of par- ticular instruments in lectures, or that students may understand the directions of demonstrators in the infirmary. These formula names are made upon the same principle as that used by the carpenter in naming his chisels or augers, as half-inch chisel, one-inch chisel,^ three-quarter-inch auger, etc. But for us to sufficiently describe the point of an excavator so that we will know the particular instrument at sight, it is neces- sary that we give three measurements. We give first the class name, as hatchet, hoe, spoon, etc. , and then give the formula of the point, or working part. This formula consists of the meas- urement, first, of the width of the blade in tenths of a milli- meter ; second, of the length of the blade in millimeters ; third, the angle of the blade with its shaft or handle, in centigrades, or hundredths of the circle. Note particularly that the width and length make up the size of the blade. Also, in order that the individual instruments of the set may be easily learned and remembered we confine the set to a regular order of sizes and angles of blade that will give a sufficient variety of forms. The set of cutting ihstrurnents consists of two lists of formulae. One of these we call ordinaries, and the other specials. Aside from the regular formula lists we have four instruments that are not made upon these formula lines. These we call side instruments. Dental Instrument Gauge. This gauge for dental instruments is used especially in the measurement of excavators, pluggers and burs. It is in the metric system. It is used as follows : I. Measure the width of the blade in the slot numbered from o to 50, which gives the width in tenths of a millimeter. This is the first figure of the formula. * Only the nomenclature and the uses of instruments will be given here. The phi- losophy of instrument forms has been well presented in the freshman year. INSTRUMENTS AND INSTRUMENTATION. 27 blade, no more and no less up the formula. 2. Measure the length of the blade in the gradations on the prin- cipal shaft, which gives the length of the blade in millimeters. This is the second figure of the for- mula. 3. Measure the angle of the blade with its shaft by laying the handle of the instrument on the main shaft of the gauge, parallel with the lines, and bringing the blade (turned toward the small numbers) parallel with one of the gradations of the cir- cular head. This will give the angle of the blade with the shaft in centi- grades or hundredths of the circle. This gives the third figure of the formula. These formulee are stamped on the handles of the excavators. Plugger points may be meas- ured and designated in a similar manner. The diameter of burs may be obtained by measurement in the slot. The Ordinaries. The set of ordinaries is made up of hoes and hatchets ; nine hatchets and nine hoes, or eighteen instruments. In these there are three widths and lengths of blade (three sizes) and three angles of The measurements of these make 28 THE TECHNICAL PROCEDURES IN FILLING TEETH. Formulae of the Ordinaries — Hatchets and Hoes. Sizes, Angles. 12 wide, 5 long. - 6 centigrades angle. 8 3 " 6 6 2 " 6 12 5 " 12 8 3 " 12 6 2 " 12 12 5 " 23 < ( ' ( ( 8 3 " 23 6 2 " 23 Note particularly that the sizes are the same in each of the three angles, and that there are but three sizes and but three angles, all told, of these ordinaries, and also that the formulae are the same for hatchets and hoes. There are nine hatchets and nine hoes in the set. Or there is a large size, a middle size and a small size in three angles. When these facts are in mind and they have been handled a few times, one should be able to name each instrument at sight. To assist in this the formula of each instrument is stamped on the handle, so that each of the three sizes in each of the three angles can easily be picked out and examined. In learning to read the points, or to name them at sight, one should pick out by aid of the figures upon the han- dles the three sizes of each angle of the hatchets and lay them together; then do the same with the hoes; then change them and lay together each size of the three angles and compare them in this relation .to each other. After doing this a few times one should be able to pick out any instrument without referring to the formula upon the handle. We call them hatchet 12-5-6, hatchet 8-3-12, hoe 8-3-12 or hoe 8-3-23, etc. The set of ordinaries have been so called because they include the forms that have been most used by dentists in the past. Instruments similar to them, but less perfecdy assorted, are found in every dentist's operating case. The smaller sizes of this set are used but little except in the preparation of cavi- ties in the incisor teeth, and mostly in the final shaping of the walls and angles of these cavities after they have been opened by other instruments. The hoe 12-5-6 used as a chisel is the most useful instrument in opening cavities in the incisors, especially for cutting away INSTRUMENTS AND INSTRUMENTATION. 29 the labial enamel margins until the proper form has been reached. The hatchet 12-5-6 performs the same office for the gingival wall. Very often, in the more delicate of this cutting, the middle sizes, i. e. , hoe 8-3-6 and hatchet 8-3-6, will serve better and in many cases it will be found more convenient to use the same sizes in the angle of 12 centigrades, or the hoe 12-5- 12 and hatchet 12-5- 12, etc., or the sizes 8-3. The smallest size, or 6-2-6 and 12, are used only in shaping the internal parts of cavities in the incisors and cuspids, and especially in squaring out the axial line angles of these cavities so that they are sharp and definite. The angles of 23 are convenient for reaching cer- tain points not easily reached with the angles 6 and 12, but are used much less than the latter. The Specials. The set of specials are so called because each instrument is designed for a special use. The formulee of this set are upon a different set of sizes, the plan of measurement being the same. In these are also three widths and lengths of blade, three sizes and one angle of blade of 12 centigrades for all except the binangled chisels, which are 6 centigrades angle. Formulas of the Specials. Straight chisel, 20, width only given. Straight chisel, 15. Straight chisel, 10. Binangle chisel, 20-9-6. Binangle chisel, 15-8-6. Binangle chisel, 10-6-6. Enamel hatchets, rights and lefts, 20-9-12. Enamel hatchets, rights and lefts, 15-8- 12. Enamel hatchets, rights and lefts, 10-6- 12. Spoons, rights and lefts, 20-9-12. Spoons, rights and lefts, 15-8- 12. .Spoons, rights and lefts, 10-6- 12. Gingival margin trimmers, rights and lefts, 20 (95)-9-i2.* Gingival margin trimmers, rights and lefts, 20 (8o)-9-i2. * NoTK.^Whcii it becomes necessary to designate the angle of tlie cutting edge of an instrument with its shaft, it is done by sliding it, without rotation, to the left, still keeping it parallel with the longitudinal lines, until the angle of the cutting edge corre- sponds with one of the lines of the larger numbers to the left. This number is then entered in brackets following the width number. When not so designated the cutting edge is at right angles with the length of the blade. 30 THE TECHNICAL PROCEDURES IN FILLING TEETH. Formulas of Side Instruments. Hatchets, 5-3-28 and 3-2-28. Discoid, 20, and cleoid, 20. Of the three last groups of specials, the enamel hatchets are rights and lefts, because of the form of the bevel of the cut- ting edge. The spoons and gingival margin trimmers are made rights and lefts by the curve of the blade. All the specials are designed for special work. They are used, except the small- est size of the spoons, almost exclusively in the bicuspids and molars, and in these they should be used for almost all of the work of excavating. The chisels and enamel hatchets are used for chipping away the enamel in opening cavities in the bicuspids and molars, and in cutting the outlines to the required form. The enamel hatchets are used especially for cutting away the buccal, lingual and gingival walls of proximate cavities in these teeth and in shaping them. Also, both the chisels and enamel hatchets are used in the final shaping of the enamel wall and in beveling the cavo-surface angle of the enamel. The gingival margin trimmers are used for only the one purpose of beveling the cavo-surface angle of the enamel along the gingival wall of proximate cavities in the bicuspids and molars. For this purpose one pair has the edge cut at an angle of 80 centigrades with the shaft, which is right for beveling the gingival cavo-surface angle of the enamel in mesial cavities, and the other pair has the edge cut at an angle of 95 centigrades with the shaft, which fits them for beveling the gingival cavo- surface angle of the enamel in distal cavities. The spoons are used for scooping out softened material (carious dentin) from the deeper parts of carious cavities. They should be used only after the walls have been cut to form by other instruments. They are not at all suited to cutting hard dentin. Side Instruments. — There are four side instruments in the set. They are called side instruments because their formulae do not coincide with those of either of the other sets. Of these the discoid (disc like) performs a service similar to the spoons, i. e. , the removal of softened dentin from the deeper parts of the cavity after the walls have been cut to form by other instru- INSTRUMENTS AND INSTRUMENTATION. 31 ments. In positions in which the access is direct it is a more convenient instrument than the spoons, though generally the spoons are better. The cleoid is used most for trimming out the angles of pulp chambers in order to reach the canals with the broach more readily, especially the canals in the mesio-buccal roots of the upper molars and the mesio-buccal and mesio-lingual angles in the lower molars. The two hatchets, 5-3-28 and 3-2-28, are used only for the purpose of undercutting the incisal angle of proximate cavities in the incisors and cuspids for the purpose of obtaining retention form. They are designed for this special purpose and are used for nothing else whatever. Instrument Grasps and Rests. The manner of holding instruments in performing dental operations is very important. There are two principal grasps : The pen grasp and the thumb and palm grasp, with modifica- tions of both. The pen grasp is used for most operations. As implied in the term, the instrument is held in the fingers in the position, or with the same grasp with which we would hold a pen, and the manipulation is carried on with the instrument held in that posi- tion, whether in cutting with an excavator or packing gold with a plugger. Perhaps nine-tenths of these operations should be done with the instruments held in that way. Occasionally positions are found in which the operation may be much facilitated by a modification of this grasp, made by bending the fingers into, or nearly into, the palm of the hand, thus inverting the position of the instrument so that it points directly at right angles to the length of the arm. This is called the inverted pen grasp. In the use of these grasps certain rests for the fingers should be sought and practiced until they are correctly obtained without especial thought. By the use of these rests operations can be much more accurately performed than without them, and they gready limit the danger of injury to the patient by slips of the instrument. The rests are generally made by placing the third or fourth finger, preferably the third, upon the teeth of the same jaw in which the tooth operated upon is situated. In operating upon 32 THE TECHNICAL PROCEDURES IN FILLING TEETH. the molars the rest will be upon the anterior teeth. When operating upon the anterior teeth the rest will be found on either side of the tooth operated upon. Any effort to use the teeth in the opposite jaw for a rest will be found very unsatisfactory, on account of the movements of the lower jaw changing the rela- tion of the rest and the tooth operated upon. Rests upon the soft tissues should be avoided as much as possible, because they are unreliable at best, and always unsteady. In the thumb and palm grasp the shaft of the instrument is held in the palm of the hand in such manner as to oppose the working point to the thumb, and the thumb of the same hand is placed either upon the tooth upon which the operation is per- formed, or upon an adjacent one, to steady the instrument and to oppose a counter pressure. This grasp is not oft;^n useful, except when unusual force is to be applied. Neither can it be used successfully in very many positions. However, there are certain operations in which its use is very desirable, and each student should learn these by careful practice. It is especially useful with the Case cleaver in removing the enamel from the teeth for fitting bands for crowns, and may be used upon any of the upper anterior teeth, and often upon the first and second molars. The thumb and palm grasp may be used very successfully with the chisel in opening cavities in any of the upper anterior teeth, and as far back as the first molars, though only in a limited number of positions. The requirement is that when the chisel is grasped in the palm of the hand and the thumb of the same hand applied to the tooth operated upon, or the one next to it, the instrument will come into position to be used effectively. When these positions are found the chisel can be used much more effectively than is possible with the pen grasp. It is therefore desirable that this grasp be practiced at every opportunity, and its use extended as much as possible. Sharpening Instruments. Nothing in dental practice is more important than the care of the cutting edges of instruments. No man ever yet became a good and effective dentist until after he had learned to keep his cutting instruments sharp. It is simply impossible to effectively prepare cavities for filling without sharp instruments. The dental INSTRUMENTS AND INSTRUMENTATION. 33 Student who can not, or will not, learn to keep the edges of his cutting instruments in good condition had better quit and go home, for he will not succeed as a dentist. A good stone is a necessity. It is of first importance that the stone be very hard. Our instruments are small, and if we attempt to use a soft stone the point will catch and ruin both the edge of the instrument and the surface of the stone. The stone should never be smaller than I ^2 by 5 inches. A stone somewhat larger is much better, but a smaller stone is a nuisance. A hard Arkansas stone is best. The hardness should be especially looked to in selecting a stone. The care of the stone is very important. It should be thoroughly oil-soaked and then wiped off. It may then be used dry or with oil, but however used it should be wiped off clean with oil upon a cloth after using. If this be not done the stone will soon fill up with the steel cuttings and it will fail to cut when the effort is made to grind with it. These steel cuttings are removed from the stone by the oil and the cloth. If the face of the stone becomes marred or unlevel from use, it may be refaced by rubbing it on a sheet of emery paper laid flat upon a smooth, level table or board. The facing should be finished on the finest grade of emery paper. A good stone should last a lifetime if well taken care of The cutting edges of the excavators should be ground care- fully, observing that the correct bevel of the edge be maintained and that the edge is kept straight. To this end instruments should be carefully applied to the stone and the correct position maintained throughout the back and forth motions of grinding. The spoons and discoids are ground by placing them on the stone so that the motion in grinding will be parallel with the length of the cutting edge, and during each stroke the instru- ment is rotated upon its edge in such a way that every part of the semi-circular edge will come against the stone in some part of each motion. This is easily done after a little practice. Care as to heating the instrument points while grinding is very important. If heavy pressure is made and the instrument moved rapidly upon the stone, enough heat will be quickly developed to draw the temper of the steel and ruin the instru- ment. It is well for the beginner to place one finger upon the point of the instrument while grinding, that he may feel the heat develop, until he has learned to judge accurately of this danger, 3 34 THE TECHNICAL PROCEDURES IN FILLING TEETH. Use of the Dental Engine. The dental engine has in recent years become an important instrument in operative dentistry. It is used for certain parts of the work of excavating cavities, for trimming fiUings to form after they have been inserted, and a large amount of the work of polishing is best done with it. For these several purposes engines should be equipped with certain sizes and forms of excavating burs, a few sizes and forms of finishing burs, stones for grinding and sandpaper disks of different grades of fineness, rubber disks for carrying polishing powders, etc. In excavating, the bur is nowadays indispensable, and yet but a small part of the excavating should be done with burs. The tendency among students is to continually use the bur too much and to use it in improper places. The forms of bur most useful are what are known as the inverted cone bur and the fissure bur. Round burs are not often used to advantage, and yet there are certain definite pur- poses requiring round burs. The sizes of burs are very important. With the dental engines with which we are supplied no large burs can be used to advantage for the reason that the motion is conveyed by a cable which allows large burs to jump and chatter. Cord engines give to the bur a much smoother motion and better cutting power, but are not regarded as so convenient. Practically none of them have sufficient power to run a large bur to advantage. For our use, then, burs for excavating that are over one and one-half millimeters in diameter should not be used at all. The most useful burs are one millimeter and less in diameter. The round bur is used only for the one purpose of opening pit cavi- ties in which decay has only just begun. For this purpose round burs, from a little less than one millimeter to one and a half millimeters in diameter, should be used by placing them in the pit while in motion and swaying the hand-piece to and fro so as to rotate the bur laterally while it is rapidly turning upon its axis. This lateral motion of the hand-piece will cause the bur " to cut much more rapidly than when held simply against the work. Use the smaller size first, and when it has entered the pit change it for a larger, using this in a similar way and follow this again with a larger size. Then the round bur should be USE OF THE DENTAL ENGINE. 35 laid aside and the cavity finished, if further enlargement is required, with other instruments. There is no other use for a round bur in excavating cavities. It should never be used for removing decayed dentine. If the pit cavity requires no fur- ther extension the round bur should be followed by an inverted cone that will square out the pulpal or axial wall of the cavity and make the angles with the surrounding walls sharp and defi- nite. * " A cavity with rounded angles is the most difficult of all cavity forms to fill perfectly. For other purposes in excavating it is a matter of choice in individual cases between the use of the inverted cone and the fissure burr. These burs should be used in se\eral positions which will be pointed out. Cutting seats or steps for anchorage in mesio or disto- occlusal cavities in the bicuspids and molars. — After the mesial or distal cavity has been well opened with cutting instru- ments, and the cutting of a step in the occlusal surface is required, choose a small inverted cone or fissure bur, never more than one millimeter in diameter, and begin within the dentin close against the dento-enamel junction, causing the bur to enter, and then draw it to the surface of the enamel ; engage it again in the same way and repeat the motion. With this move- ment, using a small bur, a groove is readily cut through the enamel into the center of the occlusal surface. In this cutting the line of the mesial (or distal) groove should be followed, because this is the weakest part of the enamel. If the bur is too large, it will not cut so well. It is only by concen- trating the force on a small bur that the enamel can be cut to any advantage, and even then the cut should be made from within outward. After this first cut has beea made the groove or channel formed should be broadened by chipping away the enamel with chisels, or the enamel hatchets, and the inverted cone bur again used to undermine the enamel upon either side, which is again chipped away. In this way a seat or occlusal step of any required extent is readily formed, the pulpal wall of which will have sharp and definite angles with its surrounding walls. Grooves that need to be cut out, merely for the purpose of finding a position for finishing the filling, i. e. , when there is solid dentin beneat^h, are to be cut in the same manner, with the inverted cone or fissure bur. In none of these cases should 36 THE TECHNICAL PROCEDURES IN FILLING TEETH. any attempt be made to cut the enamel from without inward with the bur. Cutting enamel with the bur dulls the blades very quickly. After the bur has been used for this purpose a few times, it should be discarded and a new one employed. The dull bur may be sharpened by the instrument maker. In squaring out angles of cavities, the inverted cone bur may often be used to advantage in such positions as are readily accessible, as in occlusal, labial and buccal cavities. Usually this is done by flattening the pulpal wall in occlusal cavities, or the axial wall in buccal or labial cavities. In order to accomplish this with the bur the approach must be such that the square end of the bur may be placed in the plane of the pulpal or axial wall to be formed, or, in other words, the axis of the hand-piece must be at right angles to the pulpal or axial wall to be formed. Then the side or periphery of the bur is engaged in the deeper part of the rounded pulpal or axial wall, and made to cut toward one of the surrounding walls. This is then repeated in another direction, and the bur is finally carried in a similar way around the whole circumference of the cavity in such a way that its square end leaves the pulpal or axial wall flat, and its line angles with the surrounding walls are made sharp and definite. The right-angle hand-piece is often useful for doing this work in occlusal cavities in the lower second and third molars, and occasionally in buccal cavities in these teeth. With it the proper position of the bur may be obtained in these places that are not accessible to the straight hand-piece. The right-angle hand-piece, as at present constructed, is an awkward instrument, and it should be used only in well chosen positions, inaccessible to the straight hand-piece.^ In most cases this squaring out of the pulpal or axial walls to definite angles with the surrounding walls is done just as easily and quickly with the hoes 12-5-6, 1 2-5- 1 2, or the 8-3-6 or 12, used with a scraping motion. These instruments will reach any of these positions if the sur- rounding walls have been properly formed previous to their use. In making extensions for prevention in any of the axial surface cavities the small inverted cone burs may be used to advantage. If, in excavating proximate cavities, we find that *It is now expected that a contra-angled hand-piece that will be much more useful, will be on the market soon. USE OF THE DENTAL ENGINE. 6i after cutting the gingival wall to sound dentin it is desirable to extend the cavity further to the gingival, place the end of an inverted cone bur, five to eight-tenths of a millimeter in diameter, against the gingival wall upon the dentin, close against the dento-enamel junction, and incline the hand-piece just enough to cause the periphery of the bur to cut, and press it toward and into the bucco-gingival angle, then incline the hand-piece in the opposite direction and press the bur in the linguo-gingival angle. Now, by repetitions of these movements cut as deeply to the gingival as may be required, keeping close against the dento- enamel junction. This undermines the enamel, which is now easily removed with the enamel hatchets. In extending to the buccal or to the lingual the enamel hatchets generally serve best, but occasionally the operation is facilitated by starting a small inverted cone bur in the axio-bucco-gingival angle and drawing it to the occlusal, cutting away the dentin of the buccal wall just beneath the enamel, which is then removed with the enamel hatchet. The same operation is repeated upon the lingual wall. In this extension it is important that the bur be kept close against the enamel so that it shall not cut into the tooth so deeply as to endanger the pulp. There should be no attempt to cut the enamel with the bur, for the reason, first, that it is not easily done, and second, because it ruins the bur. Whenever it is regarded as important that enamel should be cut with a bur one must expect that the bur will be ruined in the operation. , That is to say, the blades will be so dulled that it will be unfit for further use, and a new bur must be provided for the next operation. A good bur will cut dentin, however, for many operations. In making starting points for packing gold the smaller inverted cone bur is especially useful. In mesial and distal cavities in nearly all positions, starling points in the axio-linguo- gingival angle and the axio-gingivo-buccal (or laljial; angle are important conveniences. They are best made by placing the end of an inverted cone bur in the angles named, and by a slight swaying of the hand-piece cause the bur to enter just a little, then draw the bur toward the occlusal (or incisal if in incisor cavities), a short distance, making a slight groove lead- ing away from the pit first formed to give strength to the gold when placed. The pit itself shtjuld not be directed into the 38 THE TECHNICAL PROCEDURES IN FILLING TEETH. gingival wall, or only slightly, but to the lingual or buccal (labial in the incisors and cuspids), and the groove should be close against the axio-buccal or axio-lingual line angle. In this method of cutting these starting points the square end of the bur gives a square floor to the pit at the point where the first piece of gold is placed, which prevents any tendency of the gold to roll from side to side in the first efforts to condense it, so that a very shallow pit, a mere corner or sharp angle, so to speak, is all that is necessary. It should be remembered always that these convenience points are not anchorage points for the filling, but are simply starting points for the temporary anchorage of the first pieces of gold. The use of drills should be confined to certain especial purposes. These should be used when for any reason it becomes necessary to cut into the pulp-chamber of a sound tooth, or one that has already been filled. This necessity occurs frequently because of hyperaemia of, or death of, the pulp after a filling has been made, or from death of the pulp from a blow or some unknown cause. In these cases it is often necessary to cut from the surface of the tooth to the pulp-chamber, either through a filling or through the enamel and dentine. The bur is not suit- able for this work. The flat drill, bi-beveled to a point, is the proper instrument, or the drill followed by a round bur to enlarge the opening. In doing this where considerable tissue is to be cut through, it is best to use a small drill first, and when this has penetrated some distance, enlarge the opening with a larger drill or a round bur, then penetrate further with the small drill and again enlarge. Proceed in this way until the pulp-chamber is reached. In the attempt to drill deeply with a small flat drill the instrument does not clear itself of chips readily and is apt to heat ; also, it is likely to be broken by any movement of the patient. The drill is also the best instrument for enlarging root-canals for setting posts or pins for artificial crowns. It will be seen that these uses of the drill are aside from cavity excavation. The Use of Water. The use made of water in operative dentistry is very impor- tant. Every dental office should have a liberal supply of both warm and cold water. The use of water for the hands of the THE USE OF A\'aTER. 39 operator is in itself important, and the wash basin, while not necessarily before or about the operating chair, should be conve- nient, and in such position that the patient may at least know when the operator washes his hands. Cleanliness and neatness are important in gaining and in holding a practice. Water should be constantly ready for use at the operating chair for washing the teeth and gums of patients. For use in the mouth water should genei'ally be heated to about 105 degrees Fahrenheit, or just a little warmer than blood temperature. In the large majority of cases this temperature will be found most grateful to patients. If, however, cases occur, as they will, in which some of the teeth are very sensitive to thermal changes, the temperature of 105 degrees will cause considerable pain, and in such cases the temperature should be carefully reduced to gS}4 degrees, or blood temperature. The uses of water at the operating chair are : For cleaning the teeth preparatory to operating. For keeping the teeth and mouth free from blood and debris while removing calculus, or in doing any operations upon dis- eased gums, or while treating diseases of the peridental mem- branes. For washing cavities during any portion of the work of excavating that may be done before placing the rubber dam. For cleaning the necks of the teeth before applying the rub- ber dam. For treating the gums after removing the rubber dam. For removing debris and polishing powders during any por- tion of the polishing of fillings that may be done without the rubber dam. P'or any and all of these uses a good rubber-bulb water syringe which will hold a little more than a gill is necessary. A little bit of a water syringe is a nuisance. A syringe should be used with which the mouth can be flooded with water, or a strong continuous stream thrown for several seconds. For cleaning the teeth preparatory to operating, warm water should be used in almost every case, even though the teeth are apparendy in a cleanly condition. In the best of conditions there is usually more or less gummy material containing many micro-organisms about the necks of the teeth, or about cavities, especially proximal, buccal and labial cavities, which should be 40 THE TECHNICAL PROCEDURES IN FILLING TEETH. loosened up with scalers and removed with a strong stream of water. In very many cases the teeth should be cleaned with a rubber disk and powdered stone and washed clean with a jet of water before anything is done toward excavating cavities. In all cases the field of operation should be made clean as the first procedure. The use of water while removing calculus is impera- tive. The field of operation requires to be repeatedly washed with strong jets of water, in order to do both operator and patient justice. This is necessary in order to remove blood and debris that the next step of the operation may be seen. It is necessary to impart a sense of cleanliness and comfort to the patient. It is necessary to the removal of particles of loosened calculus from about the necks of teeth. In excavating cavities water should be used freely in any portion of the operation that is done before placing the rub- ber dam. In many cases it is desirable to open cavities and do the rougher parts of the excavating before the dam is applied. During such part of the operation as may be done without the rubber dam the cavity should be frequently washed with strong jets of water of the proper temperature for the purpose of removing all debris from the cavity and from the mouth of the patient. Before placing the rubber dam water should be used to free the necks of the teeth from micro-organisms, even in the most cleanly mouths. A thin scaler should be passed around all of the surfaces, loosening up any gummy substance adhering to them, and this should be washed away with a strong jet of warm water. If the case is not especially cleanly there is greater necessity for this proceeding, provided, of course, that this has not been done preparatory to ' some previous operation at the same sitting. The object of this care is especially to prevent pushing a mass of micro-organisms and debris under the free margin of the gum by the rubber and the ligature. Often the gums are more or less bruised by this procedure, and if at the same time a mass of debris containing many active micro-organisms is crowded into the soft tissue and held there for a considerable time, the micro-organisms will take hold of this injured tissue and cause very inconvenient soreness, or actual suppuration. THE RUBBER DAM. 41 Many incurable cases of phagedenic pericementitis are started in this way. After removing the rubber dam the gums should be treated with a thorough douching with w^arm water while kneading them thoroughly with the fingers of the other hand. This is especially important to the comfort of the patient. The rubber dam has been in place for a considerable time, perhaps for one, two or three hours, and during this tune the free margins of the gums have been tightly compressed by the rubber and the ligatures or other appliances for securing it in place. The circulation of the blood through this part has been stopped. The douching, together with the kneading, causes the blood to return to these tissues, starts it into active circulation again, and removes any poisonous material that may have been forced into the gingival space by the rubber. It imparts a feeling of comfort to the parts and causes at once the most complete feeling of rest from the operation that it is possible for the operator to give. The washing away of powdered stone and debris during and after polishing fillings should be thorough and com- plete, and the patient dismissed with a clean mouth, free from all grit and dirt of any sort that has been used. Always look particularly to the comfort of your patients and they will reward you for your care. The Rubber Dam. The objects to be attained by the use of the rubber dam are : to keep cavities dry and clean while excavating and while mak- ing fillings ; to better expose and bring the parts into view ; and to prevent ingress of saliva and micro-organisms during the treatment and filling of root canals. In using the rubber dam it should be remembered that it is disagreeable, sometimes painfully so, to patients, and, therefore, its use should be restricted to the actual necessities of the case in hand, and the time it remains in place should be made as short as practicable. When the cavity to be prepared is in sufficiently plain view, and the conditions are such that the saliva will not obscure the seat of operation, the ru'ober dam should not be placed until the rougher parts of the excavating is done. In excavating cavities 42 THE TECHNICAL PROCEDURES IN FILLING TEETH. in the upper teeth a considerable portion of the work may often be done before applying the rubber dam, but it should always be in place before the excavation is finished, and remain until after the filling is completed. The rule should be that the walls of a cavity should never become damp after the last of the cutting is done in their preparation. If, however, it appears from the position of the tooth, and the conditions present, that the field of operation will be contin- ually overflowed by saliva, or that the case is particularly diffi- cult to see, the rubber dam should be placed before beginning the operation. In proximate cavities it is generally best to open the cavity by cutting away the overhanging enamel, and to deter- mine the position of the gingival wall of the prepared cavity with some degree of certainty before applying the rubber dam. This will usually facilitate the' application of it, and in obtaining its proper position in relation to the gingival wall. Preparations for Applying the Rubber Dam. The rubber dam should be tough and very elastic. Gener- ally a medium thickness should be employed. It should be cut in pieces about six inches square. Before making any effort to apply it, the teeth should be well cleaned and douched with a stream of warm water from the syringe to free them from gummy material, and from collections of micro-organisms that would otherwise be forced under the free margins of the gums, or even into the soft tissues, by the ligatures or clamps. The interproxi- mate space should be cleaned by use of the ligature passed between the contact points. In doing this the difficulties to be met with in passing the rubber between the teeth will be deter- mined. The position and size of the holes in the dam should next be determined, together with the number of teeth to be included. Not less than three, generally four or five teethi should be included. If a front tooth is to be filled, include four or more, always one or two on either side of the tooth to be operated upon ; if a bicuspid or first molar, include one tooth to the distal, and at least two to the mesial ; if the second molar and the cavity involves the distal surface, include the third molar ; if the cavity does not involve the distal surface, the inconvenience of placing the rubber upon the third molar will be greater in many cases than to do the operation with a clamp THE RUBBER DAM. 4?j on the second molar. In all cases there should be as clear a field and as much room for operating as practicable. The holes in the rubber should be placed in such position that when applied it will cover the upper lip, lower lip and chin, but should not cover the nostrils of the patient and interfere with the breathing. The distance between the holes is an important consideration. They should always be as far apart as the mesio-distal breadth of the teeth to be included. In case of bicuspids and lower incisors that have thin necks mesio-distally, the distance should be a little greater. This is necessary to prevent the septum of rubber between the teeth from stretching into so narrow a band that it will fail to hug so closely to the necks of the teeth as to exclude moisture. Rubber Dam Grasps. The particular manner of grasping the rubber dam when about to apply it is very important, and should be studied with much care in the beginning of the student's experience. Cer- tain ways of grasping the rubber dam are particularly suited to the application of it in certain positions in the mouth, or to cer- tain teeth ; also to certain positions of the operator when apply- ing it. If these are well learned in the beginning it will save much time, and much of the difficulty in attaining facility in this work. In considering these grasps the side of the rubber which, when applied, will be next the gingivre is called the gingival side, and that which will be toward the occlusal surfaces of the teeth is called the occlusal side. The first grasp is used when tlie dam is to be applied to the upper front teeth. Grasp the rubber between the thumb and finger of each hand, with the ends of the thumbs on the occlusal side of the rubber and their ends touching together immediately over the hole to be first used, and the finger-ends midway the balls of the thumbs. .Stretch the rubber a litde with the thumbs still touching end to end. Then stretch the rubber a little more, and, standing to the right and in front of the patient, pass the hole o\ er the tooth; the right thumb on the lingual and the left on the labial side. In doing this, first place the free edge of the rubber at one side of the hole between the teeth, and with a slight sawing motion force it past the 44 THE TECHNICAL PROCEDURES IN FILLING TEETH. contact on that side. Then stretch it over the tooth and force it past the contact on its other side in a similar way. Now carry- each of the thumbs against the gingivae. At this point hold the thumbs in position for an instant, release the hold of the rubber with the fingers and allow it to draw around the neck of the tooth before loosing the pressure of the thumbs. Generally the rubber will be felt to draw around the thumbs, and then they should be given a slight shaking motion which will allow the rubber to draw around the tooth before releasing the pressure, and removing them. When the rubber is applied in this way it will generally be found to cling to the neck of the tooth and have its cut edge turned under the gingivae. Repeat this motion with each hole in the rubber, grasping it anew, and in the same manner for each, and pass it over the appropriate tooth with a similar motion. This grasp and these motions will answer for all of the upper teeth as far back as the first molars. When applying it with this grasp to the teeth of the left side, the face of the patient should be turned strongly to the right; or the operator should pass to the left side of the patient. The second grasp is a modification of the first, which allows the left hand of the operator to be passed around the head of the patient when standing to the right of, and partially behind, the chair. This will generally be found more conven- ient for the upper teeth of the left side as far as the bicuspids. In this the rubber is grasped with the right hand in the same way as before, but with the left hand the grasp is inverted so that the forefinger takes the place of the thumb, or is on the occlusal side of the rubber, with the thumb about oj)posite the first joint of the finger. In applying the dam with this grasp the thumb of the right hand is placed on the li;igual side of the tooth and the forefinger of the left on the labial, or buccal side. Otherwise than this change of positions the motions with which the rubber is placed are the same as with the first grasp. This grasp is also suitable for the application of the rubber to the lower teeth of the right side as far back as the second bicuspid, the operator standing to the right and partially behind the patient. In this position the forefinger of the left hand will be placed to the lingual of the tooth and the thumb of the right hand to the buccal. The third grasp is a modification of the second, in which THE RUBBER DAM. 45 the two hands are simply inverted, so that the thumb of the left is on the occlusal side of the rubber and the thumb of the right is on the lingual side. In e\ery other way the grasp is the same. This is suited to placing the rubber on the lower teeth of the left side of the mouth as far back as the second bicuspid; the operator standing on the right and passing the left hand around the head. The fourth grasp is a complete inversion of the first. In this the thumbs are both placed on the gingival side of the rub- ber, and both forefingers on the occlusal side. The rubber is grasped with the thumbs opposite the first joint of the forefin- gers, or thereabouts. The ends of the forefingers come together over the hole to be used, not directly end to end, but in the form of a letter V, the finger-ends forming the angle. The rubber is now stretched so as to open the hole slightly while the finger-ends are close against its margins. Then it is carried over the tooth, stretching the rubber sufficiently by spreading the fingers apart, made to pass the contact points between the teeth one after the other by a slight sawing motion, and the finger-ends carried hard against the gingivae, one on the buccal side and one on the lingual side of the tooth. Then the grasp of the thumbs is released while maintaining the position of the fingers and the rubber allowed to draw around the tooth. If the rubber is felt to close on the finger-ends, which it will often do, and fail to close on the tooth, make a slight oscillating motion of the fingers which will allow it to slip past them and hug to the tooth before removing the fingers. The rubber is now gras])ed anew and in the same way to be passed over the next tooth, being careful to place the finger-ends very close on either side of the hole to be used in each instance. This grasp is i)articularly suited to the upper bicuspids and first molars, the operator standing partially behind and above the patient. For this the head of the patient should be thrown well backward. Often, also, this grasp w ill be very convenient for placing the rubber on the lower bicuspids and first molars, the operator standing to the right and in front of the patient. For this position the head of the patient shoukl be ujiright. The fifth grasp is used especially for placing the dam on the second and third molars, or where it is necessary to reach far back into the mouth. In this the dam is first taken between 46 THE TECHNICAL PROCEDURES IN FILLING TEETH. the first and second fingers of each hand with the forefingers and thumbs on the occlusal side. Then the second, third and fourth fingers are closed, or nearly closed, and the dam grasped be- tween the thumbs and second fingers with the thumbs placed opposite the second joint of the fingers, or between the first and second joints. With this grasp stretch the dam a little and engage the two forefingers in it close on either side of the hole to be used and with them stretch the hole open. It is generally necessary that the hole be opened.sufificiently wide so that the tooth to which it is to be applied can be seen through it. Then carry it back into the mouth and pass it over the tooth with the forefingers, the one on the buccal, the other on the lingual, and engage one edge of the hole between the teeth, preferably the mesial first, and cause it to pass the contact by a sawing motion. When this has passed into the interproximate space throw the rubber over the distal surface, and if it is a second molar pass the contact in a similar way. Then carry each of the finger- ends hard against the gums on either side, buccal and lingual, of the tooth and holding them firmly in position release the dam with the thumbs and second fingers. The dam will now draw around the tooth, or else it will be felt drawing on the ends of the forefingers. In the latter case a little motion of the ends of the fingers will allow the dam to slide by them and close firmly around the tooth. Then, and not till then, the fingers may be removed. The dam may now be grasped again in the same way and the forefingers engaged on either side of the next hole to be used and it brought over the next tooth, whether to the mesial or distal, in a similar manner. Notice particularly that the grasp on the rubber is to be released entirely at the end of its application to each particular tooth and grasped anew for the next. It is just as important to know how to remove the fingers from the rubber without pulling the rubber away with them after it has been placed on the tooth as it is to place the rubber over the tooth ; and I wish to emphasize the necessity of noting very carefully the manner of doing this, and draw attention strongly to the fact that the dam should be allowed to fully close around the tooth while the fingers are still pressed against the gums on its buccal and lingual sides. This applies to all grasps whatso- ever that may be used in adjusting the rubber dam. THE RUBBER DAM. 47 In using the fifth grasp, the operator can use the full length of the forefingers for reaching back into the mouth and yet have full command of the rubber and readily place it on any tooth where the contacts can be passed with a sawing motion of the fingers ; and in ordinary cases it will hold without the aid of a ligature while passing it over other teeth. Of course, there are many molar teeth around which the gums are so high that the rubber can not be passed far enough onto the crown in this way for it to hold. There are also a good many tooth crowns so rounded that the dam must be forced actually to the gingival line and tied down with a ligature or held by a clamp before it can be induced to remain in place. With these grasps, how- ever, everything can be done that it is possible to do with the unaided fingers. The Use of Ligatures in Adjusting the Rubber Dam. There are many cases in which the rubber can not be forced between the contact points of adjoining teeth with the unaided fingers, and then it must be forced with the ligature. This is best done by an assistant. However, by careful practice one may learn to do it successfully alone. The ligature may be used with any of the five grasps. To accomplish this, wrap the end of the ligature on the little finger of the left hand and catch a part of its length in the same grasp with the rubber in the thumb and finger of the right hand, leaving just sufficient length ■ between so that the ligature may be tightly drawn by a move- ment of the little finger on which it is wrapped. Bring this ligature over the contact to be forced beside the finger, or the thumb, of the left hand at the same time that the rubber is stretched over the tooth. Then, by drawing with the little finger of the left hand and by the grasp with the right, the ligature is forced through, carrying the rubber before it. To get just the right length and adjustment of the ligature generally requires a little maneuvering in each individual case. The observant operator will see his way clearer and be better able to avoid difficulties with each failure. In cases in which considerable force is recjuired to drive the rubber past the contact the grasp with the fingers is often insuffi- cient. The ligature will slip in the fingers and the rubber will be stretched • too much, and a general derangement of the position 48 THE TECHNICAL PROCEDURES IN FILLING TEETH. will result. In this case it will be necessary to arrange to use greater force. To do this, wrap the ligature on the little finger of each hand, noting carefully that the length between the fingers is just right. It will often be necessary to try this length a number of times before getting it to exactly suit the particular case. Then bring the ligature over the contact and under one of the fingers or thumb with which the rubber is forced down, and stretch down the rubber into the embrasure as far as possible; then draw the ligature with the little fingers so as to tighten it on the rubber to hold it, and work the finger on the opposite side of the tooth onto the ligature, so that it may be forced on both sides of the tooth at the same time. The accomplishment of this last movement is the most difficult point, but it can generally be done after a few efforts, and then the operator has command of the situation. The rubber can be forced into the contact with all of the power of the fingers. After forcing the first contact the grasp of the rubber must generally be released, a second ligature wrapped on the fingers, the rubber grasped anew, and the second contact forced in the same way. This may now be continued until the rubber has been placed on a sufficient number of teeth. Generally, when the rubber has been forced, past one close contact this holds the rubber as a starting point, and the rest is much easier of accomplishment. Very much of the difficulties of adjusting the rubber is relieved by having an assistant pass a ligature, or set a clamp in position in these difficult cases. Another method of avoiding the most serious difficulty in passing ligatures to force the rubber between teeth far back in the mouth is to set a special clamp on the tooth first, and then throw the rubber over the bows of the clamp. For this purpose the fifth grasp should be used, and the hole in the rubber should be a little larger than usual. The ends of the forefingers should be placed fully to the distal side of the hole, or so that its distal edge is fully between the finger-ends and upon their planter surfaces. Then it must be so stretched that the distal edge of the hole may be passed over the distal edge of the bow of the clamp, starting it first over its lingual portion and sweeping it around over the buccal portion. Then release the rubber, and by a little careful motion of the fingers it is allowed to close around the tooth under the clamp. This is generally done easily THE RUBBER DAM. 49 and quickly when the particular relation of the fingers to the hole in the dam is appreciated. After this starting point has been secured it is not so very difficult to secure the rubber over the teeth mesial to it. Passing the contact with ligatures should be done with much care, for if it is allowed to snap onto the gums it will often induce considerable pain and do the patient a real injury by cutting into the tissues. To avoid this, always catch the ligature very close to the tooth on both the buccal and lingual sides. This will pre- vent that forcible snap onto the sensitive tissues that is sure to occur if this precaution is not observed. In manv cases a ligature must be tied over the rubber to hold it in place, or to force the gums sufficiently to the gingival to expose the gingival margin of the cavity. In doing this the lig- ature should be carefully forced close to the gingival line and tightly drawn with a surgeon's knot. Generally it is not neces- sary to tie ligatures on every tooth over which the dam is placed. Often when ligatures seem necessary, if the rubber is just drawn well down the ligature may be at once removed and the rubber will remain in position. Ligatures are often painful and when the results can be well accomplished without them they should not be used. Often there will be difficulty in adjusting the ligature to the lingual side of the incisors with the unaided fingers. The shape of the lingual surface causes it to slip off. In these cases the ligature should be thrown loosely around the tooth and the first half of the knot formed, but before it is drawn up the flat-curved burnisher should be passed to the lingual of the tooth inside the loop of the ligature, and carried to the gingival line and so inclined that when the ligature is drawn with the other hand it will be guided to the right position. Then the burnisher may be removed and the knot closed. This burnisher is useful in many positions as an aid in the adjustment of ligatures. In tying ligatures about the teeth, the first half of a surgeon's knot should first be formed and tightly drawn. In doing this the ligature should be grasped as close to the knot as practicable, and held close against the teeth, both to the mesial and to the distal. If the ligature is over the biduspids or molars catch the distal end of it over the end of the forefinger of one hand and force it to the distal while pulling the mesial end with the other 4 50 THE TECHNICAL PROCEDURES IN FILLING TEETH. hand. If the Hgature has been well waxed, the first half of the knot will not slip or loosen ; but it must not be pulled or dis- turbed in the least while forming the other half of the knot. Let the ends fall perfectly loose while forming the second half and work it up carefully until it is just right and then draw it tight at a single pull, again keeping the fingers close against the arch, both to the mesial and distal. A ligature tied in this way will always be tight around the tooth. Rubber-Dam Clamps. The question of rubber- dam clamps is always a troublesome one. Nothing is entirely satisfactory in all positions. The selection on the list is as good for the purpose as can be had. With them all can be done that clamps will do. In filling cavities in the bicuspids the rubber should be secured on the molar tooth distal to them with a rubber-dam clamp. The bow of the clamp holds the rubber out of the way and gives space and a better view of the field of operation. In excavating and filling cavities in the molars this is still more nec- essary. Whenever practicable the clamp should be placed upon the first molar for operations on the bicuspids, and on the second molar for operations on the first molar. Generally, in operations on the second molar not involving the distal surface, a clamp with a bow standing well to the distal should be placed on the same tooth in order to avoid the difficulty of placing the dam on the third molar. Rubber-dam clamps on the bicuspids are not per- missible at all except in cases where the molar teeth are missing; and even then they are of doubtful usefulness, and are so unsteady as to cause the patient much annoyance, and often considerable pain. In buccal and labial cavities, that approach near to, or pass beyond the gingival line, the special clamp should be used on the molars and the Hatch clamp on the bicuspids and front' teeth. Except in the most difficult cases, the special clamp will answer the purpose if the rubber, after being placed on the tooth, is drawn well away from the buccal and the clamp applied, or if the clamp is put on first and the rubber passed over it. When the Hatch clamp is applied to the front teeth with labial cavities, the rubber must be drawn well away from the labial surface and the points placed in position and the set- THE ENAMEL, 51 screw made tight. Then the rubber may be allowed to draw tightly around it, and is fairly certain to exclude moisture per- • fectly. For this purpose the hole in the rubber should be cut a little larger than usual. With the most skilful, some impossible cases occur with any and all of these instruments. Then resort must be had to hold- ing the dam in position with an instrument while performing the operation with the other hand. This is difficult, but prac- ticable. The best instrument for this purpose is a straight shaft with a broad flat point cut in the form of a fork, or a V-shaped notch. Often in proximate cavities, where the gingival wall is very difficult to reach, the rubber may be forced into position and held with a matrix, or the matrix may be placed first and securely tied and the rubber applied over it. Sometimes a similar device will accomplish the same upon buccal surfaces. When the operation is completed, great care should be had to remove all ligatures before removing the rubber, for if the rubber is pulled away with a ligature on, a ring of rubber will sometimes be torn away and remain around the neck of the tooth unobserved, and do great damage before the cause is dis- covered. When the contacts between the teeth are close, or when gutta-percha fillings have been placed to seal in treat- ments, the rubber should be drawn to the buccal or labial, and the septum passing between the teeth cut before removing the rubber. This will avoid the danger of leaving bits of rubber dam hanging between the teeth or of disturbing a soft filling. Finally, when the rubber has been removed, the gums should be well kneaded with the fingers, while being flooded with warm water from the syringe. The gums have been compressed and the circulation interfered with, and this will clean the parts and start the blood into full activity and prevent the severe soreness that is so apt to follow. The Enamel. The structure of the enamel is of such importance in its rela- tion to the preparation of cavities for filling that it requires spe- cial study. It is difiicult to so prepare specimens of the enamel that they show its structure well, and when the specimens are well prepared, it requires a large amount of study to gain that 52 THE TECHNICAL PROCEDURES IN FILLING TEETH. intimate knowledge of it that is necessary to the most intelhgent practice in filling operations. The enamel when examined macroscopically appears as a very hard, vitreous body, white, or a bluish-white, very dense and brittle, in which no traces of structure can be determined. It cuts with much difficulty, and is much inclined to chip and crumble. If, however, it is examined with a good hand magni- fying glass, certain striations can be observed that give a sugges- tion of histological structure. Although the enamel seems to be opaque, or, at most, trans- lucent, by ordinary examination, it is found to be almost as trans- parent as glass when ground into thin sections. When so prepared, very little of the structure can be seen with the micro- scope usually, without some preparation that will cause its histo- logical elements to appear. It is largely for this reason that so little is seen of the structure of enamel in the sections ordinarily prepared for microscopic observations. Histological Characters of the Enamel in Relation to the Preparation of Cavities. Enamel is composed of rods or fibers cemented together by an intervening cement substance. These rods and cement substance are very nearly of the same density, so that when examined in the perfect state the enamel seems to be almost homogeneous, or without special structure. In the most perfect specimens of enamel only a striation suggesting structure can be seen. It has been learned, however, that the cement substance between the rods by which they are united dissolves more readily in acids than the rods themselves. We may avail ourselves of this fact, and partially isolate the rods by solution of the cement substance with very dilute hydrochloric or lactic acid, and in that way obtain good views of them. We can not, however, carry this solution very far, for the reason that the rods will also be dissolved, and the whole tissue disappear. Still, by working carefully with very dilute acids, good fragments of the rods may be obtained. The enamel rods seem to be made up of globules or little balls pressed together in a single row or line, forming the rod. One can readily copy this formation by taking small balls of soft clay and pressing one upon the other, forming a rod. In some THE ENAMEL, 53 enamel these globular forms are very prominent in the apparent make-up of the rod, while in some other specimens these globules are so perfectly fused together and smoothed as to almost dis- appear ; we then have a smooth enamel rod. This latter is rather the exception than the rule. The enamel rods are stronger than the cement sub- stance, so that in any attempt to break up or cut the enamel it is inclined to split along the length of the rods. Then, since the enamel is very hard and difficult to cut, a knowledge of the direction of the rods becomes of first importance in any attempt to form cavities in teeth. These rods, while hard to cut, are, when they are parallel, very easy to split apart. Indeed, much of human enamel will split almost as easily as straight-grained pine, if the force is applied in just the right direction. This is because the cementing substance that cements the rods together is much weaker than the rods themselves. In other specimens of enamel the rods, instead of lying parallel with each other, are very much interwoven and twisted together ; so much so, indeed, as to prevent them being readily split apart. This enamel, instead of splitting like straight-grained pine, is more like the pine knot, which is very difficult to split or cut, as com- pared with the straight-grained wood. Formerly it was sup- posed that this difference in the enamel to cutting instruments was due to a greater amount of lime salts, or the hardening ele- ment. We have learned in recent years, however, that this is not the case. The one contains no greater proportion of lime salts than the other and will not resist decay any better. But the difference is due wholly to the difference in the relative inter- lacing of the enamel rods. This interlacing or twisted form of enamel is usually confined to the inner half of its thickness. While in the outer half of the enamel the rods are parallel and will split apart readily, the rods of the inner half are interwoven or twisted in such a way as to prevent splitting. Therefore, when a chisel or enamel hatchet is applied for the purpose of splitting it off it will,- if supported by sound dentin, split but about half way, and the remaining half of the thickness is removed with great difficulty. It is then almost a necessity that we undermine this by cutting away the dentin from beneath it, after which we may break it down f|uite reachly. 54 THE TECHNICAL PROCEDURES IN FILLING TEETH. The enamel rods are almost always parallel AA/^ith each other in the outer half or near the surface of the enamel. This fact you should observe carefully, for it is of the utmost importance in the preparation of the enamel margins of cavities. All that we have said of the splitting apart of the enamel rods applies with all of its force to this outer portion of the enamel, no matter how much the rods may be twisted in the deeper portions, and for this reason the enamel margins of cavi- ties should be so prepared that no portion of the cavo-surface angle will present short ends or rods unsupported; that is, the enamel wall should be parallel with the length of the rods, and the bevel of the cavo-surface angle should cut off the ends so that there may be no loose ends of rods upon the surface to fall away while packing gold or after finishing the filling. This may readily be accomplished if we know the direction of the enamel rods. The direction of the rods may be known, first, by obtaining a good general knowledge of their course by the study of pre- pared sections of enamel; second, by observing the direction of cleavage during the preparation of cavities. By the term cleav- age we express the tendency of a substance to split or separate in given directions. The direction of cleavage is the direction in which it splits most readily. Therefore, for our purposes the terms cleavage and splitting are practically synonymous. It may be stated as a general rule that the direction of the enamel rods is from the center of the crown of the tooth tow^ard the surface. Everywhere on the crown of the tooth the ends of the enamel rods present to the surface. Over the greater portion of the crown the direction of the enamel rods is perpendicular to the surface, but in every tooth there are certain portions in which the enamel rods approach the surface at a more or less considerable inclination. If we draw a line around the crown of a molar or bicuspid tooth in the middle of its length and examine the enamel rods in that section we will find them everywhere very nearly perpen- dicular to the plane of the surface. If we move, now, gradu- ally, toward the cusps of the tooth we will find the direction of the enamel rods progressively leaving the perpendicular and inclining toward the cusps. This inclination becomes continually greater, until when the point of the cusp is reached the direc- THE ENAMEL. tion of the enamel rods is parallel to the length of the cusp, or, in other words, the direction of the rods is perpendicular to the surface of the tip or point of the cusp. If from this line around the crown of the molar or bicuspid in the center of its Length we approach one of the marginal ridges of the occlusal surface, we will also find the direction of the enamel rods inclining toward the marginal ridge in such a way that as we pass over the marginal ridge the direction is so changed that the rods stand perpendicular to the occlusal surface. If the attempt be made to prepare a cavity upon an axial surface of one of these teeth for filling, and this cavity ap- proaches a cusp or a. marginal ridge, the enamel wall must be inclined outward Tor toward the occlusal) very gready, or else short ends of enamel rods will be left at the surface. And if inclined enough to prevent this, the filling material will be so thin at its margin that it will not have sufficient strength. These facts forbid us laying enamel margins near the occlusal margins of the axial surfaces of the teeth. If now, we proceed from the center of the length of the crown of the molar or bicuspid toward the gingival line, we will find the direction of the enamel rods again deviating from the perpendicular and inclining toward the gingival line. This inclination is much less in extent, however, but more variable than that found in passing toward the marginal ridges of the occlusal surfaces. The inclination at the gingival line is usually about six centigrades, often less, and the greatest that I have observed has not been more than ten centigrades. An inclina- tion of six centigrades is readily overcome by inclining the enamel wall, or even twelve centigrades inclination of this part of the enamel wall can readily be made and the filling material be sufficiently strong for the locality. On examination of the occlusal surface of a molar or bicus- pid we find a tendency of the enamel rods to incline somewhat toward the pits and grooves, and especially do they incline toward open pits or fissured grooves. If the grooves are well closed and shallow, there will be less inclination toward them. As we pass from the pits and grooves toward the cusps the direction of the rods first becomes perpendicular to the surface and then begins to incline toward the cusps, and when we arrive 56 THE TECHNICAL PROCEDURES IN FILLING TEETH. at the point of the cusps the direction will be perpendicular to the surface at the immediate point of the cusp. Or, if we follow the direction of the rods passing from the fossae of the occlusal surface to the marginal ridges, mesial and distal, we find the direction of the rods first deviating from the perpendicular toward the center of the fossae, but as we pass toward the mar- ginal ridges the deviation is toward the marginal ridges, until, when we arrive near the crest of the ridge, the direction of the inclination is decidedly toward the ridge. Therefore, in the preparation of cavities in the occlusal sur- faces of these teeth the enamel wall may be cut perpendicular to the general plane of the occlusal surface, so long as the enamel margin does not approach too closely to cusps or the marginal ridges, for a slight bevel of the cavo-surface angles will insure a solid margin without any short ends of rods. But if the cusps or the marginal ridges are closely approached the inclina- tion of the enamel wall should be toward the ridge and the cavo- surface angle beveled rather more strongly in order to insure the removal of all short ends of enamel rods, and to secure a firm margin. In the incisors and cuspids, if we draw a line around the crown at the junction of the middle and gingival third, we will find the enamel rods perpendicular to the surface upon the mesial, distal and labial surfaces, and generally nearly so upon the lingual surface. In these teeth the direction of the enamel rods at the junction of the middle and gingival third of the lin- gual surface is very variable, because of the differences of the prominence of the linguo-gingival ridge and the depth of the grooves of the lingual surface. In cases in which the linguo- gingival ridge is prominent and the grooves deep, or fissured, ' there will be a strong inclination of the enamel rods toward the grooves. If, on the other hand, this surface is smooth and even, with the grooves perfectly closed, so as not to be apparent, the direction of the enamel rods will be perpendicular to the surface. As we pass from the junction of the middle and gingival third of the crown toward the incisal margin of the lingual surface, the inclination of the enamel rods is more and more toward the incisal. At the junction of the middle and incisal third the inclination is from six to twelve centigrades, and in the incisal third it often is fifteen or eighteen centigrades before the incisal THE ENAMEL. 57 edge is reached. This very strong inclination of the enamel rods toward the incisal upon this surface renders it exceedingly- difficult to make good margins if the marginal lines of the cavity approach nearer the incisal edge than the junction of the middle and incisal thirds of the crown. If the cavo-surface angle of the enamel is beveled enough to remove all short ends of enamel rods the filling material becomes too thin to stand well. This is the reason we so frequently see imperfect margins when the marginal lines of fillings have been laid inthis position. On the labial surface of the incisors and cuspids, the direction of the enamel rods is generally about perpendicular to the surface of the junction of the middle and gingival third, and as the incisal margin of the surface is approached there is a gradual inclination toward the incisal. This change is slow in the middle third, so that it is rarely more than six centigrades at the junction of the middle and incisal thirds. In the incisal third the increased inclination to the incisal is much more rapid, so that upon the incisal edge the direction of the enamel rods is parallel to the long axis of the tooth. These directions of the rods must be taken into account in any case in which the mar- ginal lines of labial cavities" approach the incisal margin of the surface. Fortunately, such cavities are rare. On the mesial and distal surfaces the direction of the enamel rods is generally perpendicular to the surface through- out the middle third of the length of the crown. In the incisal third an inclination toward the angle begins. The extent of this is quite variable. The rule is that the more acute the angle the closer the angle is approached before the inclination of the rods toward the angle becomes pronounced. Therefore, the distal angle being more rounded the inclination of the rods toward it begins further from the angle upon the distal surface, but often approaches the angle quite closely upon the mesial before the inclination becomes great. For this reason cavity lines in mesial surfaces may approach safely quite close to the incisal angle if the enamel is well supported by sound dentin. In the distal surfaces much more care must be exercised in lay- ing cavity lines close to the incisal angle, for the reason that if the enamel wall is inclined enough to give a good cavo-surface angle the edge of the filling is likely to become too thin to stand well. 58 THE TECHNICAL PROCEDURES IN FILLING TEETH. In following the inclination of the enamel rods around the incisors and cuspids in the circumferential direction, we find them generally standing perpendicular to the surface. A notable exception to this is the approach to the mesial and distal marginal ridges on the lingual surface and over the lingual marginal ridges. Here the enamel rods incline somewhat toward the marginal ridges, but in passing over these ridges their direction or inclina- tion changes rather suddenly. For this reason this becomes rather a dangerous point in the preparation of proximate cavities in the incisors. When the marginal lines of these proximate cavities reach to the lingual marginal ridge, it is rarely safe to leave any of the ridge remaining, because of the very uncertain direction of the enamel rods. Especially is this true of lateral incisors, in which the curve of the ridge is often very abrupt. While this ridge is very strong in the perfect tooth, it becomes very frail when its support on either side has been destroyed, and the only safe course seems to be to cut it away sufficiently to be certain of the direction of the enamel rods upon the margin formed. The rounding of the labio-mesial or labio-distal angles is not so abrupt, and the enamel rods usually hold closely to a direction perpendicular to the surface, so that good margins can be made at any point by observing carefully the form of the tooth and the enamel cleavage. In passing toward the gingival line from the junction of the middle and gingival third of the length of the crown, the inclina- tion of the enamel rods changes more and more toward the gingival. This varies considerably in different specimens ; gen- erally it is not much more than six or eight centigrades at the gingival margin of the enamel, but in some specimens it is ten or twelve centigrades. This calls for extreme care in beveling gingival cavo-surface angles in cavities that approach close to the gingival line. How to Study the Direction and Inclination of the Enamel Rods. The first studies of the enamel rods should, of course, be made by grinding sections and studying these with the aid of the microscope, and in lantern illustrations. But when a fairly good idea of the structure has been obtained in this way it is better to continue the study by noting carefully the cleavage of the enamel THE ENAMEL. 59 while operating at the chair. In preparing cavities one is han- dHng the enamel all the time, and by noting the direction of the cleavage and remembering that this cleavage follows the length of the enamel rods, may be continuously studying their direction in ditTerent positions upon any and all of the teeth. This study, when pursued for some time, enables an operator to so place his instruments as to split ofif the enamel easily in opening cavities, which is of immense advantage in this work, as he will do it easier and quicker. The operations will also be greatly improved because of more perfect preparation of the enamel margins. He will come to know very perfectly the direction of the rods, and the proper inclination of the enamel wall in all positions. One soon learns to feel for the direction of the enamel rods with his cutting instruments and to take advantage of the cleavage in cutting the enamel, and then readily feels this in the formation of the enamel wall and its cavo-surface angle, and knows when his enamel margin is firm and strong. Carry on the study at the chair and become a rapid and strong operator. The shaving up of the enamel in forming the enamel wall should be looked to with great care. Those points at which the enamel rods are more or less broken apart will generally appear a little whitish, and in pushing a sharp edge lighdy along them the loosened rods are easily dislodged in what appears as a fine powder. By continuing this shaving motion the enamel wall will become clear, and have a firm, vitreous appearance. This condition of the enamel wall should always be obtained in finishing the preparation of the cavity. In the study of the enamel in sections and on the screen, it has been seen that the lines of the grooves are weak lines on account of the imperfect fusion of the enamel plates in coming together during development. This is true even in those grooves that are most perfecdy closed. But in very many cases they are imperfectly closed, so that along these lines the enamel has no strength. It should, therefore, be the rule that, when in the prepara- tion of a cavity the marginal lines must approach near a groove, cut to the groove or past it. This rule should be regarded as applying in all positions upon the teeth if the cavity margin is parallel, or very nearly parallel, with the groove. For instance, I will mention that in preparing 60 THE TECHNICAL PROCEDURES IN FILLING TEETH, large cavities in the distal surfaces of upper molars the disto- lingual groove is often approached. In any such case cut to the groove until it has passed over the ridge to the lingual surface, when its direction is more to the mesial, and then break away from it rather suddenly, forming a kind of step, if the enamel of this portion of the lingual surface is well supported by sound dentin. If the mesio-buccal angle of a molar is so decayed as to make the removal of a considerable part of it necessary, cut to the buc- cal groove, for if this is not done the intervening portion of enamel is very likely to break away. The same rule applies to the triangular grooves of the bicus- pids that pass to the buccal surface to the mesial and distal of the buccal cusps. If in any case the angles of these teeth are so injured that the cavity lines should approach near these grooves, cut to the grooves. In any case in which the angle of an incisor must be removed, cut to the labial groove, whether it be mesial or distal. This is for the reason that the lines of the grooves are weak lines, and the enamel is likely to break along these lines. These cases will sufficiently illustrate this rule. Excavation of Cavities by Classes. Note. — The determination of the conditions calling for filling operations is largely dependent upon pathological pro- cesses. As it is the intention to confine this book as strictly as possible to the technical procedures of filling operations, these pathological processes will not be discussed. Here we can only take note of the physical conditions presented by individual teeth, leaving pathological processes related to them to be taken up at another time. Class I. — Cavities beginning in structural defects in the teeth, as pits and fissures. — These occur in the occlusal surfaces of the molars and bicuspids, in the occlusal half of the buccal surfaces of the molars, or in the buccal pits, more rarely in the lingual portion of the disto-lingual groove of the upper molars, and in the lingual surfaces of the upper incisors ; most frequent in the laterals. EXCAVATION OF CAVITIES PA" CLASSES. 01 The primary physical condition leading to the location of caries in these positions is a foult, or imperlection in the enamel — an imperfect closure of the enamel plates — which leaves an opening of more or less depth as a pit or fissure, and it is in these that decay starts. The surface of the enamel in the immediate neighborhood of these is fully exposed to the friction of mastication and is kept well cleaned. For this reason there is no disposition to the spreading of the carious process upon the surface of the enamel. Therefore, these cavities all belong to the class which do not require extension of the cavity outiines for the prevention of the recurrence of decay. All the extension that is necessary is such cutting away of the cavity walls as will fully uncover the carious area and present a surface upon which a good, smooth finish of the filling can be made. In order that this good, smooth finish may be made, it is necessary that all sharp grooves connecting with the cavity be cut out to a point where the enamel is sufficiently level. Pit Cavity in Central Fossa of an Upper First Molar No. I. Description. — Upon examination a small pit in the enamel is found and the point of the exploring instrument passes through it into the dentin, which seems to be softened, show ing that caries has begun. The surface of the enamel about the pit is clear and clean. The buccal groove is deep and sharp, but the mesial and distal grooves are shallow, fairly smooth, and well closed. Procedure. — A round bur, A millimeters in diameter, in the engine, is placed in the pit while in rotation and fairly strong pressure applied, while the hand-piece is swayed to and fro. In most cases the bur will cut through the enamel and enter the cavity within a few seconds. If it does not do so promptly, it should be removed for a moment and allowed to cool — for heat will develop quickly — and then reapplied in the same manner. This should be repeated until the bur passes through the enamel and enters the softened dentin. Immediately this occurs, the bur should be removed from the hand-piece and a bur, i mil- limeter in diameter, chosen. This is passed through the opening into the dentin in the same way, thus enlarging the opening in the enamel. This is then exchanged for a larger bur, i i^o mil- limeters in diameter, which is also passed through the opening. 62 THE TECHNICAL PROCEDURES IN FILLING TEETH. This completes the use of the round bur, and it is the only use made of it in excavating cavities. An examination should now be made with a curved explorer to determine more nearly the extent of the decay in the dentin. In case no softened dentin extending laterally under the enamel is found, the rubber dam should be applied and an inverted cone bur, equal in size With the last round bur used, should be introduced, and with its square end the remaining decay should be removed, and the floor, or pulpal wall of the cavity made flat. Now, with hoe 12-5-6 used as a chisel (straight chisel 10 or binangle chisel 10-6-6 may be substituted), the enamel is chipped away along the buccal groove as far as it will readily split off". Then an inverted cone bur, 10 millimeters in diameter, is passed into the cavity and made to enter the dentin just beneath the dento- enamel junction toward the buccal groove, and slowly drawn to the surface of the enamel. It is then entered again at the same point, and this motion repeated, making cut after cut, following the line of the groove, until the groove has been opened to a point where it is sufficiently shallow, or the surface of the enamel is sufficiently level for a good finish of a filling to be made. Often it will be necessary to follow this groove to the crest of the marginal ridge. This done, chip away the mesial and distal walls of the slot formed, with straight chisel 15 or 20, sufficiently to remove the inclines of the buccal groove, after which pass a large inverted cone, or a fissure bur (ito millimeters), through the slot, and make its floor square and flat, and smooth up the walls. A very careful examination should now be made of all parts of the walls of the cavity. If any softened dentin is found, the enamel should be chipped from over it with hoe 12-5-6 or chisel 10, the softened area removed and the pulpal wall of the cavity squared out to the increased area. The outline of the cavity should now be re-examined to see whether every part of the margin is sufficiently level to permit a good finish of the filling when this has been placed, and if irreg- ularities occur that would prevent a smooth finish, the cavity must be sufficiently extended to obtain conditions that will allow a good, smooth finish of all parts of the margin to be made. The finish of the enamel wall is now to be made by careful paring or planing with a sharp chisel. So far as possible EXCAVATION OF CAVITIES BY CLASSES. G3 the mo\ement of the edge of the chisel should be in the direc- tion of the length of the margin, or around the cavity. In such a cavity as this, both the dentin and enamel walls may be per- pendicular and the opposing walls parallel. The enamel rods will be inclined toward the cavity in every part, and no outward inclination of the enamel walls is necessary. The cavo-surface angle of the entire margin should be slightly beveled to dirninish the danger of fracture in placing the filling material. In such a cavity no starting points for beginning the filling are required, and no further preparation for retention of the filling is necessary, except to see that the opposing walls are parallel. Variations. — It will often happen that in a cavity of this description a considerable area of decayed dentin will be found beneath the enamel after the burs have been passed through into it. In this case the overhanging enamel must be chipped away with hoe 12-5-6 or chisel 10 or 15, until sound dentin is reached in every direction. When this has been done, the remaining portion of the buccal groove should be cut out as described, first completing the outline of the cavity. Then, if the area has become considerable, the remaining decay is best removed with spoons 1 5-8- 1 2 or 20-9-12, as may best suit the size of the cav- ity. Enter the blade beneath the softened material, close against the enamel wall at the lingual or buccal side, and force it with a strong thrust in a curved direction to the other side of the cavity ; two or three strokes well made should be sufficient. Then square up the pulpal wall so that its angles with the sur- rounding walls are sharp and definite, using hoe 12-5-6 or, in some positions, hoe 1 2-5-1 2, with a scraping motion. In many cases this will be as conveniently and accurately done with a square-ended fissure bur, i /,? millimeters in diameter, or with the inverted cone bur. In this use of the bur, the shaft should be held parallel with the long axis of the tooth, so that the square end of the bur will cut the pulpal wall of the cavity flat and make its angles with the surrounding walls sharp and definite. Finish the enamel wall and cavo-surface angle the same as before. In many cases the mesial groove will be so sharp and deep that it will require cutting out well toward the mesial marginal ridge. 64 THE TECHNICAL PROCEDURES IN FILLING TEETH. Pit Cavity in Central Fossa of Upper First Molar No. 2. Description. — The pit is open so that the exploring instru- ment readily passes in, giving room to be turned about, revealing a considerable decayed area ; some discoloration shows through the enamel. Procedure. — Begin the excavation by chipping away the overhanging enamel with straight chisel 15. Or, if the orifice in the enamel is still very small, begin with straight chisel 10, and use the 15 later. This may be done by hand pressure, but mallet pressure is much better. Continue this chipping as far as the enamel can be readily cut in this way, or until sound dentin is found supporting the enamel at every point. Now look care- fully to the relations of the outline of the cavity to the surface, and proceed at once to cut out any grooves that will interfere with a perfect finish of the filling. Now take hatchet 8-3-23, or, if the opening into the cavity is too small for this, take hatchet 6-2-23, and sweep its edge around the dentin wall of the cavity with a few vigorous strokes, loosening up and partially removing the softened material from them, and see whether or not there are some points at which decay extends beneath the enamel. If such are found, clip the enamel from over them and perfect the cav- ity outline. At this point the rubber dam should be adjusted. The next step should be to square up the dentin walls. If there is a considerable mass of decay obscuring the cavity, it may be first removed roughly by a few vigorous strokes with spoons 20-9-12. In squaring up the dentin walls a square-end fissure bur (irV millimeters) may be used in cases in which this may be brought parallel with the long axis of the tooth, which can gen- erally be done in the occlusal cavities in the first molars and bicuspids. This is placed with its end upon the pulpal wall, and, while rotating, pressed laterally against one of the sur- rounding walls, and carried around the whole cavity in a series of cuts. This will square up the surrounding dentin walls to the enamel walls, and its square end will leave the pulpal wall flat, and its angles with the surrounding walls sharp and definite. This is to be taken as the plan of squaring up the sur- rounding and pulpal walls (and axial walls in buccal and labial cavities) when burs are used for that purpose. EXCAVATION OF CAVITIES BY CLASSES. 65 In doing this, care should be had not to continue any single cut so long as to develop considerable heat. Often much unnec- essary pain is produced, and occasionally serious injury done to the pulp of the tooth by the heat developed by rapidly rotating burs. Also care must be had as to possible unnecessary expo- sure of the horns of the pulp of the tooth. In very deep cavities it may be best not to square up the whole central depth of the ca\ity, because of danger to the horns of the pulp, but to cut a shelf, so to speak, around the periphery to form the principal seat of the filling, leaving the central part of the cavity deeper. This deeper portion should then be freed of softened material with the spoon excavators. In no case should any decayed and softened material be left in the deeper parts of the cavity. It is better to expose the pulp of the tooth than to leave it covered only with softened dentin. In many cases the squaring up of the surrounding walls, and flattening of the pulpal wall, may be more easily done with the hoe 1 2-5- 1 2, or 12-5-6, used with a scraping motion, than with the bur. When the walls of the cavity have been squared up, and the angles of the pulpal wall, with the surrounding walls, made sharp and definite, and all carious material removed, the enamel walls may be planed to form, and made smooth in every part. Unless the enamel walls approach very close to the marginal ridges, they may be in the same plane with the dentin walls, or parallel to the long axis of the tooth. But if they do approach closely to the marginal ridges, the enamel rods will be inclined toward the ridges, and the enamel wall must be similarly inclined to be in correct form. This may always be discovered by noting carefully the direction of the cleavage of the enamel while chip- ping it away, and the inclination of the enamel wall should be made to correspond with the enamel cleavage. When the enamel wall is in correct form and planed smooth, the cavo-sur- face angle must be slightly beveled in every part. This bevel should not extend to more than one-fourth the thickness of the enamel, and often should be much less. Generally such cavities need no convenience points for starting fillings, but when large, and the operator feels that slight con- venience pits will aid him, there is no special objection to their use. They should be placed in the distal portion of the cavity. 66 THE TECHNICAL PROCEDURES IN FILLING TEETH. Parallel walls and a flat pulpal wall as a seat, or a good strong peripheral ledge in very deep cavities, gives perfect anchorage. No undercuts are required. All of this done, the cavity should be swept free of chips and fine dust and is ready for filling. The use of chip-blower should be sufficiently frequent and thorough to keep the cavity free from cuttings, and the whole field of operations cleared of debris during all parts of the operation. In second and third molars some differences of procedure and of instrumentation are necessary on account of the differ- ences of position. Often the bureau not be brought into position for effective use in squaring up the surrounding and pulpal walls, and this is done best with the hoes 12-5-6 or 1 2-5-12, or, in some positions, hoe 12-5-23, used with a scraping motion. In a few cases the bur may be used effectively in the right-angle hand- piece, but this is an awkward, and generally ineffective, instru- ment, and its use instead of hand instruments should be reserved for cases of the greatest necessity. The mesial wall, and especially the mesio-buccal angle of occlusal cavities in the second and third molars, should be so inclined to the mesial and buccal as to allow of packing gold against them easily. The amount of this inclination will depend upon the position and the character of the approach to the cavity. If the mouth of the patient opens well, giving a good view, and allows instruments to be placed very nearly parallel with the long axis of the tooth operated upon, very little inclina- tion to the mesial and buccal will be required. If, on the other hand, the mouth does not open well, and the approach of the instruments must be at a considerable inclination to the distal, the mesial wall and the mesio-buccal angle must be inclined in proportion, or sufficiently to allow of mallet force being applied parallel with the plane of this wall and angle. Any failure in this will require in filling with gold that the gold be packed against this wall by lateral hand-pressure, which greatly increases the difficulty of making a good filling. When the preparation is for amalgam fillings this is not demanded, but it is still desirable. When the distal pit in the occlusal surface of the upper molars is the seat of operation, the procedure is not essentially different, except that the approach should be rather more from the buccal. The same instruments and the same methods should be employed. In these it is very generally necessary to cut out EXCAVATION OF CAVITIES BY CLASSES. 67 the disto-lingual groove to the crest of the hngual marginal ridge, and frequently to follow it over onto the lingual surface of the tooth. This should be done with the inverted cone bur, as previously described (pages 35 and 62). In the lower molars the grooves are generally deeper and more deeply sulcate than in the uppers, and will much oftener require cutting out to the crests of the marginal ridges. These teeth frequently have a lingual inclination, which renders occlusal cavities less easy of approach. In this they present great varia- tion, many being as easy of approach as the upper teeth, and sometimes easier. Yet frequently there occurs a lingual inclina- tion that renders them very difficult. If these are prepared for filling with gold by the use of direct force, the mesial wall must be inclined to the mesial, and the mesial portion of the buccal wall must be strongly inclined to the buccal to allow of direct force being used. It is in these cases, however, that reverse pluggers have their greatest use, and when such cavities are to be prepared for the use of these, the mesial and buccal walls may be squared up in the axial plane ''^ without inclination by use of the. square-ended fissure bur in the right-angle hand-piece, or with hoes 12-5- 12 and 12-5-23, and the binangle chisels. Gold can then be well packed with reverse pluggers, but not by direct force. Occlusal cavities in the upper bicuspids are so easy and direct of access, that little difficulty is experienced in their preparation. The principal points of instrumentation are the same as have been described. Occlusal cavities in the lower bicuspids are difficult only in cases of strong lingual and distal inclination of these teeth. In these cases the instrumentation is similar to that described for the second and third lower molars, except that smaller cutting instruments will be required. Pit cavities in the buccal surfaces of the molars. — The pit cavities in the buccal surfaces of the molars must be distin- guished sharply from smooth-surface cavities occurring in these surfaces. The pit cavities have their beginning only in the buccal pits and arc primarily in the occlusal half of the buccal surface. .Smooth-surface buccal cavities are primarily in the gingival half of the buccal surface and begin in the smooth * Any plane, one direction of which is parallel with the long axis of the tooth. 68 THE TECHNICAL PROCEDURES IN FILLING TEETH. portion of the enamel close to the gum margin. They are not always very close to the gingival margin* of the buccal sur- face of the tooth, because the free margin of the gum often, particularly in young people, considerably overlaps the gingival portion of this surface. In these cavities the principles of instrumentation are the same throughout as that described for occlusal cavities, except as their location and the direction of approach render differences necessary. Pits, in which decay has just begun, should be opened with burs as described for occlusal surfaces. Where more decay has occurred, so as to allow the use of chisels, or hoes used as chisels, the opening should be made by chipping away the enamel. The squaring up of the axial and surround- ing walls and making the axial line angles definite, should be done in the same way as in occlusal cavities, if done with burs, or if done with the hoes and chisels. Sometimes in the second molars and generally in the third molars the angle of approach will be such that the straight hand-piece of the engine can not approach the cavity at the correct angle, and the right-angle hand-piece must be used, or what is usually better, the work must be done with hoes and binangle chisels. In finishing the enamel walls the case is different, in that the enamel rods will generally be found perpendicular to the surface upon the central part, but inclining toward the occlusal as the occlusal margin of the surface is approached. Therefore the incli- nation of the enamel rods, or the direction of the cleavage, should be closely noted while chipping away, and the occlusal enamel wall finished in inclination to the occlusal, so as to be parallel with the line of the cleavage. If in any case it is found that because of close approach to the occlusal surface, the inclination of the enamel wall to the occlusal will render the filling material too thin at its margin to have sufficient strength, the buccal groove should be opened over the crest of the marginal ridge and the filling carried onto the occlusal surface in the form of a step. Neglect of this precaution is causing the loss of many otherwise good fillings in this position. * Note.— Distinguish carefully between the terms gum margin and gingival line, or a gingival margin of a surface of a tooth. Gum margin refers to the position of the free edge of the gum, while the gingival line is the line of junction of the enamel with the cementum, or the normal line of the attachment of the gums to the tooth. The gingival margin of a surface of a tooth is at its gingival line. EXCAVATION OF CAVITIES BY CLASSES. 69 Pit or fissure cavities on lingual surfaces do not occur in the lower molars, but do occur occasionally as independent cavities in the lingual grooves of the upper molars and rarely in the mesio-lingual groove of the upper first molars, where there is a fifth cusp. The instrumentation in these is on the principles already given and requires no special description. In pit cavities in the lingual surfaces of the incisors, two points of special caution need to be mentioned. First, the location of the cavity is such that the pulp is easily reached, and accidentally and unnecessarily exposed, unless especial caution be observed. The use of burs should be limited strictly to the first opening of pits but little decayed. Neither inverted cone nor fissure burs should be used in squaring up the axial and sur- rounding walls, because the angle of approach is such that the sharp angle of the bur is presented toward the pulp, . instead of its square end. This necessarily defeats the object as to squaring up the axial and surrounding walls, and rendering the axial line angles sharp, and especially endangers the pulp. All of this work should be done with the hoes and the smaller chisels. Except in the smaller cavities, the direction of the enamel rods will be much inclined to the incisal upon the incisal_^wall of the cavity. This should be carefully noted in clipping away the enamel, and the finished enamel wall should have the proper inclination to give it the necessary strength. Smooth-Surface Cavities. Classes 2, 3, 4 and 5 are all smooth-surface cavities. This distinction has been sufficiently described (page 7), but it is so important that it will be repeated here. The special points of distinction will also be further emphasized as the procedures are developed. Class 2. — Cavities in the gingival third — not pit cav- ities — of the labial, buccal, or lingual surfaces of the teeth. — Of these the smooth-surface cavities in the lingual sur- faces of the teeth are so infrequent that a mention of them seems to be all that is necessary. Difference in position calls for some differences in instrumentation between these and smooth-surface cavities on the labial and buccal surfaces, but the principles of their preparation are the same. 70 THE TECHNICAL PROCEDURES IN FILLING TEETH. Labial cavities in the incisors and cuspids. — These cavities occur in surfaces of the enamel that are smooth and per- fect. There is no pit, groove or fissure which serves as a start- ing point for the carious process. In this they are totally different in their conditions and surroundings from the cavities which begin in structural imperfections of the surfaces of the teeth, as pits and fissures. In the beginning of pit and fissure cavities, lodgments of d6bris and fermentable material is con- fined to the pit itself ; the surface of the tooth immediately sur- rounding the pit or fissure is so situated in relation to the uses of the teeth that it is constantly kept clean by the friction of masti- cation. Decay never begins upon clean surfaces. Therefore, there is no disposition for decay to spread upon the surface of the enamel, or to make a new beginning in the immediate neighborhood of the pit or fissure ; it spreads beneath the enamel only. In all smooth-surface cavities the case is reversed. There is no pit or fissure that holds debris, but the position and relation of the surrounding parts of the surface to the first starti-ng point of decay are such that it is not kept well cleaned by the fric- tion of mastication and the motions of the tongue, lips and cheeks. Therefore, it is much of the time in an unclean condi- tion. This area of uncleanness will vary indefinitely, so that the cases met with in practice vary indefinitely. The first beginning of decay in these surfaces is central to the area of habitual uncleanness, or better, central to the greatest constancy of the uncleanness. As this is close to the gum margin, the first begin- ning of cavities in labial surfaces is usually close to the gum margin. But as the area of uncleanness is spread upon the sur- face, so has the beginning of decay a tendency to spread upon the surface. For this reason we find in labial and buccal cavities broad, shallow injuries to the enamel, very frequently, and many instances, when seen early, in which the enamel is broken through at a number of points near together, or spread in a line near the gum margin. An examination of these cases show clearly the tendency for the decay to begin in the enamel in a constantly widening area. Therefore, in preparing this class of cavities for filling, the principle is established of so extending the cavity outline as to include the area of the surface, which, under the conditions presented, is especially liable to decay in the EXCAVATION OF CAVITIES BY CLASSES. 71 future. This is called extension for prevention. It applies to all smooth-surface cavities. Case I. — A central incisor has shown sensitiveness near the gum margin, and upon passing a pointed exploring instrument over it, it catches at a number of points, and at some of these the point evidently passes through the enamel into the dentin. Examining the condition of the surface carefully, the appearance of an area of habitual uncleanness is found to extend along the gum line, occupying the middle three-fifths of the surface mesio- distally, and about one-third of the surface gingivo-incisally. The incisor teeth are now well cleaned and the rubber dam adjusted over them, and the Hatch clamp applied to this tooth and the gingivus forced well out of the way. The surface indi- cated is well dried and examined. The enamel is found chalky, whitish, with openings through its thickness in the central area ; and, extending mesially and distally in a crescentic form, there are whitish lines. In these lines an exploring instrument does not catch when passed lightly, but when a little force is used it does catch, showing a degree of softening of the enamel. Gin- givally the line of injury ceases abruptly at the border of the gums. That portion of enamel covered by the gum is smooth and perfect. Procedure, — One, or two, or three vigorous strokes of chisel 15 breaks up and removes the injured and friable enamel over the central area, leaving the dentin bare, and reveals the fact that it is exceedingly sensitive. An inverted cone bur with sharp blades, i ni millimeters in diameter, is placed with its end perpendicular to the labial surface directly into the central decay and quickly carried over the whole surface, extending the depth a little into the dentin and somewhat enlarging the opening. The effect of this first movement is to remove the hypersensitive area almost, or quite, completely, and the rest of the excavation can proceed with much less pain. The same bur is again intro- duced and carried along the mark indicating the position of the gum line until the mesial border of the surface is nearly reached and all of the whitish line of the enamel removed. This may possibly have required two or three cuts, but often may be done with one. With the same bur the distal part is cut out the same way and to the same extent. The result is a narrow, crescent- shajjed cavity, no wider than the bur, following the gum line 72 THE TECHNICAL PROCEDURES IN FILLING TEETH. from angle to angle (nearly - — not passing around quite to the actual line of the mesial or distal angle of the tooth, though in many cases it should). The incisal wall of this is now broken down with the straight chisel, and if still further extension to the incisal seems required, the bur is passed around the incisal wall, cutting away the dentin from beneath the enamel, which is again chipped away with the chisel. This cutting should be carried to the incisal until such portion of the surface as may seem especially liable to future decay has been removed. Generally, it is not necessary to make considerable extension in this direction. Next, attention is turned to the gingival wall. The first cut has removed all injured enamel in this direction, but the length of the free gum margin will allow of the cavity being extended more, without reaching the gingival line, and a finish can be made against perfect enamel that will be fully covered by the gum margin. This is just such a wall as is most desirable in all smooth-surface labial or buccal cavities. Decay never begins under a covering of healthy gum, and as long as the margin of the filling is thus protected, and the margin well made, it is safe; therefore the enamel is carefully planed away to the proper position with very sharp chisels with a motion along the length of the wall or from mesial to distal, and from distal to mesial. In executing this the thumb and palm grasp is to be preferred. The dentin wall is now cut back with the same inverted cone bur used previously or with hoe 6-2-12 or 8-3-12, and slightly undercut in order that it may be retentive. Any corrections required in the gingival enamel wall are now made. This should be inclined strongly to the gingival, the particular inclination having been determined by observation of the direc- tion of the enamel rods while trimming away the enamel from this surface. The incisal wall is also squared up and the dentin wall slightly undercut — about as an inverted cone bur placed with its flat end on the axial wall would do it. This is generally easier done, however, with hatchet 6-2-23. Then the enamel wall is finished, .inclining it slightly to the incisal. Its cavo- surface angle should be slightly beveled by a planing motion with a very sharp chisel carried very lightly along its length. The mesial and distal angles of the cavity are similarly finished. EXCAVATION OF CAVITIES BY CLASSES. 73 Before filling, the operator may, if he thinks it will be more con- venient for starting the filling, cut two convenience points, one in the axio-mesio-gingival angle and one in the axio-disto- gingival angle. This should be done with the square end of an inverted cone bur, about A or A millimeters in diameter, and be about half the depth of the head of the bur. After forcing the bur into the dentin to this depth it should be drawn a little away along the axio-gingival line angle extending the pit into a slight groove that diminishes and runs out at a length of about three diameters of the bur. This little extension will increase the hold of the gold and render the starting easier and more certain. We now have a crescent-shaped cavity, with somewhat blunt points, with a perfectly flat axial wall that includes the area of the surface most liable to decay. Case 2. Left upper central incisor with labial decay. — Cavity open and occupying the gingival third of the surface inciso-gingivally, and the middle three-fifths mesio-distally. The incisors are cleaned, the rubber dam adjusted, the gingivus pushed well back with the Hatch clamp, and the tooth dried. It is now seen that a line of injury to the enamel runs from the mesio-gingival angle of the cavity to a filling in the mesial surface, and another such line connects with the distal surface, in which there is a small open cavity. The filling in the mesial surface is good and sufficient except at its labio-gingival angle, where slight decay has begun. These lines of injury show as a w^hitening of the enamel only, there being as yet no apparent loss of substance. The patient is twenty years old and suffer- ing badly from caries. Procedure. — All overhanging enamel is chipped away from the incisal portion with chisel 20, using the thumb and palm grasp, and the dentin wall squared up to a sufficient depth. Then with chisel 15 the gingival wall is cut away to sound dentin, again using the thumb and palm grasp and cutting from mesial to distal. This wall is found solid and clean very close to the gingival line, only a very slight band of thin enamel remain- ing, but it is sufficient to prevent actual injury to the attachment of the peridental membrane. This is favorable and regarded as important, because it insures a healthy free margin of gum after the operation. The angles are also cut to sound dentin with the chisel. At the angles the superficial injury to the enamel is 74 THE TECHNICAL PROCEDURES IN FILLING TEETH. found to be more extended than the decay in the dentin. An inverted cone bur, i miUimeter in diameter, is placed in the mesio- gingiwil angle of the cavity with its square end toward the axial wall, and entered into the dentin just beneath the dento-enamel junction and carried along the line of whitened enamel to the point of connection with the filling in the mesial surface. The enamel is chipped from the incisal wall of this cut with chisel 15 and the cut widened by again passing the bur, cutting the dentin toward the incisal. This portion of the incisal wall is now trimmed smoothly to its connection with the incisal wall of the original' cavity. The same bur is now entered in a similar manner into the disto- gingival angle of the cavity and carried to the distal along the line of the whitened enamel to the margin of the labial surface and slightly over onto the distal surface, but not connected with the distal cavity. This cut is stopped at a point upon the distal surface at which the outline of the distal cavity, when prepared, will cut into it. This cut is now widened toward the incisal by chipping the enamel with the chisel and again cutting away the dentin with the bur and smoothly connected with the incisal wall of the original cavity. This completes the outline of the cavity. The surrounding walls are clean and the retention form partially provided for, but the carious material in the central and deeper portions of the cavity is undisturbed. It is still a question whether or not the pulp will be found exposed when this is removed. The right- hand spoon 20-9-12, used with the palm and thumb grasp, is now entered under the distal margin of the carious mass and its edge swept across to the mesial, along the incisal wall, cutting out the decayed material. Another similar cut is made, directed to the gingival half of the cavity, by which the last of the carious material is removed, leaving all parts of the cavity clear and white. The pulp is found covered by sound Ijard dentin. The edge of the spoon is now passed carefully over the surface of the cavity with a scraping motion, to be sure that no softened material remains. This central portion being deeper than is desirable to make the surrounding walls, it may be filled for a part of its depth with zinc oxyphosphate as a protection to the pulp, or better, its central portion may be covered with a bit of quill after the anchorage of the filling has been started and the gold built upon and over it. The anchorage is now to be perfected. The EXCAVATION OF CAVITIES BY CLASSES. <0 gingival dentin wall which was left inclined to the gingi\al by the chisel is squared up with hoe 12-5- 12 and slightly undercut with hoe S-3-12 or 6-2-12. Then the enamel wall is finished to the mesial and distal angles with chisel 15, and the cavo-surface angle very slightly beveled. A convenience pit is now made, one toward the mesial and one toward the distal in the gingivo- axial line angle with an u> millimeter inverted cone bur, and each extended slightly by grooving toward the central part of the length of this line angle. The incisal dentin wall is slightly undercut with an inverted cone bur held with its square end to the axial wall and passed along from mesial to distal, or better, with hatchet 8-3-23 or 6-2-23. The incisal enamel wall is finished, being inclined slightly to the incisal and its cavo-surface angle very lightly beveled, the straight chisel 20 being used, and cuttmg in the direction of the length of the wall, using the thumb and palm grasp. This cavity as prepared in\oh'es nearly half the labial surface inciso-gingivally, and the whole surface mesio-distally, the filling in the mesial cavity making a portion of the wall. Upon the distal the filling, after being made, will be cut into when the cavity on the distal surface is prepared. It is a somewhat extreme type of labial cavity. Labial cavities in the upper laterals and cuspids, in the lower front teeth, buccal cavities in the bicuspids and in the first molars, would be excavated in the same manner and with the same instruments. The thumb and palm grasp of instruments can not so frecjuently be used to advantage in buccal cavities in bicuspids and first molars, as in like positions in the anterior teeth. In the second and third molars this grasp is usually inapplicable. Generally the inverted cone or square-ended fissure bur may be used with its shaft at right angles to the buccal surfaces as far back as the first molar, and in occasional fa\orable cases in the second molar. Usually the right-angle hand- piece must be used if the bur is employed in excavating buccal cavities in the second or third molars. In most cases, however, the instrumentation is e.'isier, and the excaxation is made quicker by using chisels and the hoe excavators. These may be effectually assisted by using the inverted cfjne bur for making extensions toward the mesial, chijjping tlie enamel from the occlusal wall of the slot cut, and again undermining with the bur. 76 THE TECHNICAL PROCEDURES IN FILLING TEETH. The difficult point in the preparation of buccal cavities in the second and third molars occurs when considerable extension of the cavity to the distal is required. If the dentin is hard and firm, and the enamel still strong, it is difficult to cut with hand instruments. This work is effectively done by placing an inverted cone bur, i\ millimeter in diameter, used in the right- angle hand-piece, in the distal portion of the cavity, and entering it in the dentin near the dento-enamel junction, and pushing it to the distal, and at the same time drawing it to the surface. By repeating this motion in cut after cut, the required extension may be made. This slot is now extended by chipping the enamel, and again undermining with the bur as described for other posi- tions. This plan of operating is not always available, however. Often the clamp must be used on the second molars, always on third molars, and the bow of the clamp is in the way of the right-angle hand-piece. In this case, if burs are used at all, they must be used by a different method. An A millimeter inverted cone bur used in the straight hand-piece, is placed with its end against the distal wall of the cavity, and its square end entered in the dentin at the dento-enamel junction. Now by swaying the hand-piece back and forth, the bur is caused to enter the dentin to about the depth of its head ; then, by pres- sure toward the surface while withdrawing the bur, it is made to cut the enamel from its inner surface. By repeating this motion, the enamel may be cut through and a slot formed of any desired extension. The enamel may now readily be pared from the margins of this with straight chisels, the enamel further under- mined to the occlusal or to the gingival by cutting out dentin along the dento-enamel junction with the bur, and removing more enamel with the chisel. In_ this use of instruments the axio-gingival and axio-buccal line angles, as made with the bur, are rounded and not in good condition to receive filling mate- rial. This is remedied by cutting these to sharp and definite angles with hoe 6-2-12 or 6-2-23, by a scraping motion!. When the cavity is broad gingivo-occlusally, the size 8-3 of tlie hoes may be used. Buccal cavities often extend so far gingivally that the gingival wall is beyond the gingival line and the cavo-surface angle is of cementum instead of enamel. This must always be regarded as unfortunate, for the reason that the attachment of the gum to EXCAVATION OF CAVITIES BY CLASSES. i t the tooth has been injured and because of the increased difficulty of making the filling. The injury to the attachment of the gums is necessarily permanent, and yet, if the operation is well and smoothly made, a fair degree of health of the gum margin is generally maintained. In these cases it is best to remove the attached membrane from the cementum sufficiently to allow room for the clamp and provide additional room to readily see the cavity margin after the filling is in place, in order that the filling may be, finished definitely and smoothly to the tooth sur- face. It is better to destroy the attachment a little further and secure a smooth perfect finish, than to risk imperfect work at so important a point. Class 3. — Cavities in the proximate surfaces of the incisors and cuspids, which do not involve the removal and restoration of the mesial or distal angle.— In the excavation of this class of cavities a much greater range of forms of cutting instruments may be used effectively than in other classes, and a greater variation of method of instrumentation is consistent with rapid and thorough operating. In the work the ordinaries are used almost exclusively, the bur being employed only to accomplish a few special purposes. The cavities are all smooth-surface cavities and the rules of extension for prevention are applied in their preparation. Case I. — The left upper central incisor has a decay in its mesial surface, just to the gingival of its contact point. Appa- rently it is small, but a curved exploring instrument introduced from the labial or from the lingual enters through the enamel. Procedure. — The first procedure is to free all of the incisor teeth of debris or micro-organisms and gummy material, par- ticularly about their gingival portion, and apply the rubber dam. Dry the teeth and apply the- Perry separator and get sufficient separation to pass a thin polishing tape between the teeth. Then, with the 8-3-6 hoe used as a chisel, begin near the labial margin of the cavity to break down the overhanging enamel, chipping from the surface into the cavity. This should generally be done by hand pressure, being careful to place the edge of the cutting instrument very near the margin in each instance and split off the enamel in little flakes. In this cutting the third finger should be very securely rested upon the adjacent teeth and the motions of the instrument so closely controlled that its 78 THE TECHNICAL PROCEDURES IN FILLING TEETH. edge will not be thrust into the depths of the cavity and cause pain. Continue this cutting until the enamel is found supported by sound dentin, or until the cavity of decay is well exposed. In many cases it will be best in this position, when decay is extensive, to leave some enamel unsupported by dentin, espe- cially when of about full strength, rather than expose so much filling material as the complete removal of the enamel would do. When this wall has been chipped away sufficiently, chip away the lingual wall in the same way and with the same instrument, working from the lingual. This, if the cavity be not very small, will give good access to all of its parts. If the cavity is small, take hatchet 8-3-12 and introduce its blade between the teeth from the labial, with the edge directed to the gingival, catch the enamel near the cavity margin and chip it away by a prying motion, using the proximating tooth as a fulcrum, removing as much enamel in this way as practicable. Only the thinner por- tions of weakened enamel margins can be removed by this motion ; but now a stronger instrument may be used, sufficient room having been obtained for its introduction. Generally, hatchet 12-5-6 or chisel 10 may be introduced against the labial enamel wall, with its edge directed toward the gingival and the enamel wall trimmed away, using strong hand pressure, and, by changing the direction, the cutting can be continued along the gingival wall to or past the labio-lingual center of the tooth. With the same instruments working from the lingual, the lingual wall is next cut down in the same way, to, and somewhat past, the linguo-gingival angle of the cavity. For trimming the remainder of the gingival wall hoe 12-5-6 will be required, or the 8-3-6 if the cavity is not opened sufficiently to admit the larger instrument. This is done with a scraping motion. Fre- quently hatchet 12-5- 12 will do this well, working from the labial. The gingival wall should be cut to sound dentin and made as nearly flat in the horizontal plane as practicable. Now, examine carefully as to the requirements of extension for prevention. In most cases a line of superficial injury to the enamel will be found running away labially, from the labio-gin- gival angle of the cavity near the gum line. Another line of superficial injury leads away in similar fashion from the linguo- gingival angle. Often, also, particularly in the smaller cavities, there is superficial enamel injury to the gingival of the gingival EXCAVATION OF CAVITIES BY CLASSES. 79 wall. The cavity must now be extended so that it will include all of these superficial injuries. To do this, place a small inverted cone bur (I'V or lu millimeter) in the labio-gingival angle, intro- ducing it from the lingual in most cavities, and enter the dentin close to the enamel junction, and swaying the hand-piece as much as the position will allow, undermine the enamel in the direction of the line of superficial injury, sinking it at first about the depth of the bur head. Then very slowly withdraw the bur, pressing it toward the labial and incisal, thus widening the cut in this direction. Now, with the hoe 12-5-6 or 8-3-6, the undermined enamel may be chipped away. These cuttings may be repeated until the extension in this particular direction seems sufficient. If now it is desirable to extend the cavity to the gingival, the same bur may be introduced as before, and drawn toward the lingual with pressure against the gingival wall, cutting the den- tin close against the dento-enamel junction, and the undermined enamel chipped away with the hoes or hatchets, working from the labial. In many cases all of this cutting with the bur can better be done from the labial, keeping the shaft of the instru- ment as nearly as possible in line with the central axis of the tooth. After some cutting in this way, the attention should be turned to the linguo-gingival angle. To extend this the same bur should be introduced from the labial and its end entered into the dentin at the dento-enamel junction in the direction to under- mine the line of injured enamel. In this position the first cut should generally be made as near to the lingual enamel plate as is desirable to cut the cavity, and the bur should be drawn back with pressure toward the gingival, extending the undermining in that direction. It is also generally desirable in this position to again introduce the bur, and while drawing it toward the labial make pressure against the undermined enamel, so as to weaken it. Then it may be broken away with hoe 8-3-12, catching the edge of the instrument on the surface and using a pulling motion, throwing the chips into the cavity, or it may be cut away by using a scraping motion from labial to lingual with hoe 12-5-12, or 83-12 if the first is too broad to enter the cavity well. Also this is well done with hatchets 12-5- 12, or 8-3-12, or enamel hatchet 10-6- 12 working from the labial. If still more extension to the gingival is required, it is readily done by passing the square end of the bur along the gingival wall, cutting out the 80 THE TECHNICAL PROCEDURES IN FILLING TEETH. dentin close against the dento-enamel junction and afterward removing the enamel. In excavating and extending cavities in the proximate surfaces of the incisors and cuspids, it should be noted particularly that these surfaces are wedge-shaped or triangular, with the base of the triangle at the gingival margin, and that the finished cavity should have that form, with its labio-gingival and linguo-gingival - angles widely extended toward the angles of the surface de- cayed. The gingival wall should be perfectly flat mesio-dis- tally with the axio -gingival line angle sharp. Labio-Iingually it should be either straight and parallel with the horizontal plane of the tooth, or curved with its convexity to the incisal. The incisal angle should next receive attention. It often happens that decay has extended along the dento-enamel junc- tion considerably in this direction. The enamel should be chipped away with hoe 12-5- 12 or 8-3-12 until sound dentin has been fully reached, and in doing this, very careful attention should be given to the direction of cleavage with reference to the final inclination of the finished enamel wall. When the out- line form has been attained, the incisal angle should be undercut for retention. Usually this should be done before looking specially to the retention in other parts of the cavity, for the strength required of these will depend much upon the strength of the incisal retention. The incisal retention is made by under- cutting to the incisal in the form of a groove. The incisal angle is first well rounded and the dentin cut away to some depth from the dento-enamel junction directly at right angles to the axial surface of the tooth, with hoes 8-3-12 and 8-3-23, or equivalent hatchets, using angle 23 mostly close against the labial wall. Then hatchet 5-3-28, or if that blade is too long, hatchet 3-2-28 is used for cutting a groove in the incisal angle, and extending it along the labio-axial line angle. The instru- ment is introduced from the labial, its edge directed to the incisal, and, beginning at the labio-axial line angle a little removed from the incisal angle, carry its edge toward the incisal and lingual around the angle, in part by a twist of the instru- ment. Then it is placed well to the lingual and swept in the opposite direction, or toward the labial, all the time cutting close against or slightly into the axial wall. These motions are repeated until the groove is of sufficient depth. Now, with the EXCAVATION OF CAVITIES BY CLASSES. 81 8-3-23 hoe, or if the cavity is small the 6-2-23 hoe, introduced from the labial and with its edge turned to the labial or the axial wall, the axio-labial line angle is made sharp and definite along the length of it well to the gingival, using a scraping motion from the gingival toward the incisal. Often the 6-2-23 hatchet will do this as well, using it with a back and forth scraping motion, holding the shaft of the instrument at right angles to the long axis of the tooth. The axio-lingual line angle is now made definite throughout its length, using hoes 8-3-12 or 6-2-12 or the 6-2-23 near the incisal angle. This should be completed to, and into the axio-linguo-gingival angle. Undercutting at the axio-linguo-gingival angle for retention will depend upon the strength of the incisal anchorage ; if this be good, but slight retentive form, just sufficient to serve in starting the filling, is all that is needed in this position. The ' axio-labio-gingival angle, which has been left sufficiently definite by the bur, is now slightly grooved for a short distance toward the incisal, complet- ing the retentive form by squaring out with hoe 6-2-12 or hatchet 6-2-23. Any decay now remaining in the deeper parts of the central portion of the cavity is removed with spoons 10-6-12. Or if the cavity is large, the spoons 15-8-12 may sometimes be better. The cavity is now ready for the finish of the enamel walls and the cavo-surface angles. The enamel wall is planed smooth in every part and its inclination corrected. If the operator has noted carefully the direction of the cleavage of the enamel at all points while chip- ping it away, he will be at no loss as to the correct inclination at the different points, he remembering that this shall follow closely the cleavage lines. This is done in all parts with the chisels, except some por- tions of the gingival enamel wall and a short reach upon the lingual wall where it joins the incisal angle. The movement of the chisel should be along the length of the enamel wall, cutting very lightly. It must be very sharp to be effective. At the labio-gingival and linguo-gingival angles the outline should form short curves, no matter how sharp the angles of the dentin walls; sometimes it is difficult to plane the whole length of the gingival wall smoothly with the chisel, especially where it joins the curve at the linguo-gingival angle. Here hatchet 12-5-6 or 1 2-5- 1 2 answers better; or occasionally one of the hoes. These 6 82 THE TECHNICAL PROCEDURES IN FILLING TEETH. instruments will also smooth the lingual portion of the curve at the incisal angle in many cases. At the incisal angle, the incli- nation of the enamel wall must generally be strongly toward the incisal, especially in distal cavities, in order to follow the length of the enamel rods. When the trimming is done, note carefully whether the retentive form has been injured at any important point by trimming too deeply, and make such corrections as may be required. Finally bevel the cavo-surface angle in all parts of the enamel margin, using the chisel for nearly all this work. At a few points, especially along the gingival, the hatchet 12-5-6 or 12-5-12, or the 10-6-12 enamel hatchet, will do the work easier. Make the toilet of the cavity and fill. General observations on the preparation of prox- imate cavities in the incisors and cuspids. — In all cases the enamel margins should be cut sufficiently around the curves of the surface toward the labial and lingual, that the margin will be well away from the contact of the two teeth when the filling has been finished. At the gingival the mar- gin should be well covered by the gum septum when this is in its normal position. The gum septum should be carefully preserved from injury in all parts of the operation, for upon the health of this tissue depends largely the health and good appear- ance of the tooth. Toward the incisal the cutting should always include the normal contact point in distal cavities. In mesial surfaces the contact point is sometimes so near the incisal angle that this is impracticable. In these cases, unless strictly required by the extension of decay, the original contact point of the enamel should not be removed, but a new contact should be made by a slight fullness of the filling a little to the gingival of the position of the original contact, so that the incisal enamel mar- gin will be held a little apart from contact with the proximating tooth. A very little space at this point is sufiicient, for the rea- son that to the incisal of the contact, in the use of the teeth, the excursions of food constantly cleans the margin of the filling. In medium and large cavities it is best to cut the labial wall well over onto the labial surface of the tooth, for the reason that, if cut only to the mesio-labial or disto-labial angle the light will not reflect from the surface of the filling and it will appear as a EXCAVATION OF CAVITIES BY CLASSES. 83 dark cavity. A little further extension to the labial relieves this and gives the appearance of a filling. A little careful observa- tion of this point will prevent mistakes that are often very annoying to sensitive patients. The appearance of sharp angles in cavity outlines that are exposed to view should be avoided. Slighdy curved lines are better than straight lines. But the key to good appearance of operations on the incisors is perfect tooth form, including particularly the full mesio-distal breadth of the tooth. In the incisors, and especially in the laterals, the labial embrasure is usually well rounded out, and open, because of the rounded form of the labio-mesial and labio-distal angles of these teeth. Upon the lingual the embrasures are very shallow and close, because of the acuteness of the mesio-lingual and disto- lingual angles of the teeth, and the flatness of the lingual surfaces from mesial to distal. For this reason the proximate cavities in these teeth often begin well toward the lingual and burrow much more under the enamel of the linguo-mesial or linguo-distal angle of the tooth than toward the labial. The result is that the enamel to the lingual is often undermined and very thin from injury of the inner half of its thickness from backward decay, or decay of its inner surface. Also the lingual marginal ridges are often quite sharp and the course of the enamel rods uncertain, so that a good margin can not certainly be made upon the sharp curves of these ridges. Therefore, when the enamel margin of the cavity must be laid against the enamel of the lingual marginal ridge, it is best to cut away the marginal ridge and lay the enamel margin of the cavity on the lingual surface of the tooth. In this case this enamel wall will be cut parallel with the axial wall of the cavity, or in the labio- lingual plane of the tooth. Frequendy this enamel wall will be level with the axial wall of the cavity, and this renders the placing of the filling more than ordinarily difficult. When the amount of tissue will allow, it is well to sink the lingual portion of the axial dentin wall sufficiendy to obtain a slight ledge at the lingual. This is readily done with a few strokes of the 6-2-12 hoe for the gingival third, and with the 6-2-23 hoe for the incisal two-thirds of the lingual wall, introducing these instruments from the labial. Class 4. — Cavities in the proximate surfaces of the incisor teeth involving the loss of the mesial or distal 84 THE TECHNICAL PROCEDURES IN FILLING TEETH. angle, and its restoration. — In this class of cases the prox- imate cavity is prepared, with the exception of its mesial angle, in the same way and with the same instruments as have been described, except that the anchorages in the labio-gingival and linguo-gingival angles are made deeper and stronger. That is, the axial wall is cut deeper into the dentin in the gingival portion to the lingual and to the labial than in its central area, for the purpose of sinking these anchorage points deeper into the substance of the dentin. The weak incisal angle is cut away to the labial groove, mesial or distal, as the cavity is to the mesial or distal. This groove, although not very apparent, is a weak line in the enamel at which it most often breaks, and it should always be included when the angle is so weak as to require removal. When this has been done, cut away the incisal edge of the middle lobe of the tooth, i. e. , to the next labial groove mesial or distal, with the corundum stone in the engine or with a small flat jeweler's file, cutting more from the lingual than the labial. The depth of this cutting should depend upon the thickness of the cutting edge of the tooth. If the cutting edge be thick and already somewhat worn, very slight cutting is sufficient. If unworn and thin, the cut- ting should be greater. A small inverted cone bur, not more than I'ij millimeter in diameter, is now caused to enter the dentin in the proximate cavity, close to the junction of the labial and lingual enamel plates, and carried, by a series of cuts in which the bur is drawn out at the incisal edge, along the length of the incisal edge across the middle lobe, or as far as the incisal edge has been previously cut. In this cutting with the bur, the labial enamel plate should be left complete and the cutting done at the expense of the lingual enamel plate. After the first cut is completed, forming a groove, in which the bur should always reach fully into the dentin between the labial and lingual plates, the lingual plate should be cut away to very nearly or quite the depth of the cut by the bur. Then the bur should again be passed along the slight groove left, cutting it deeper, keeping close to the lin- gual rather than the labial enamel plate, forming a groove in the dentin between the enamel plates. In making this groove it is an object to leave as much dentin as possible supporting the labial enamel plate. The depth of the cutting toward the pulp of the tooth must be guided by the judgment of the operator, EXCAVATION OF CAVITIES BY CLASSES. 85 care being taken not to expose the pulp. But in these cases it is ahvays better to expose and remo\e the pulp, than to fill with an anchorage that is manifestly insufficient. The groove is the principal dependence for the incisal anchorage. This should be squared out with a fissure bur and its walls made parallel. No undercuts or pits are needed. A little broadening and rounding away where it joins the proximate cavity will make this connec- tion stronger. In the incisal enamel walls formed in making this incisal step, both labial and lingual, the enamel rods incline toward the incisal, and these walls should take that form rather than be cut at right angles with the long axis of the tooth, and then the cavo-surface angle must be slightly beveled ip order to give it greater strength. Teeth with thin, cutting edges are very difficult of manage- ment in making incisal steps for the restoration of a lost or weak angle, because the gold built on them is too thin to have suffi- cient strength. In many of these cases, the incisal edge of all of the incisors, or only the centrals, may be ground away in imitation of normal wear, and the incisal edge thickened without injury to the appearance. In doing this it is well to remember that in very thin teeth the horn of the incisal pulp is likely to be long and slender, and the danger of exposing them in cutting the step is increased. In cases where there has been such wear of the incisal edges of the teeth that the dentin is exposed, the step should include all of the exposed dentin. In this case very little cutting from the lingual enamel plate will be needed, and generally none from the labial. In the management of this class of cases it should be remembered that in such large cavities the bulk of gold in close proximity to the pulp is liable, through its conductivity of thermal changes, to set up irritation that will destroy its vitality. In cases in which there seems to be imminent danger of this, it is better to remove the pulp at once. It is also better to remove the pulp at once than to run serious risk of losing the filling from insufficient anchorage in the effort to save the pulp alive. Class 5. — Preparation of cavities in the proximate surfaces of bicuspids and molars. — The preparation of proximate cavities in the bicuspids and molars, if estimated by the comparative number of failures in filling teeth, must be regarded as the most difficult of filling operations. Therefore, 86 THE TECHNICAL PROCEDURES IN FILLING TEETH. more than usual attention should be given by the student to the specific plans and details of these operations. The instruments used are almost exclusively the specials. There is very little that can be done advantageously with the ordinaries except some occasional cutting with the larger sizes. More cutting away of sound firm dentin and enamel is required than in any other class of cavities. The proximating surfaces are broad, and for success in preventing recurrence of decay, it is required that these be cut away, so that the outlines of the cavity be free from near contact with proximating teeth, and laid in such position that they will be well cleaned by excursions of food over them in mastication. Also, in making fillings it is of the utmost impor- tance that the contact be restored in normal form for the protec- tion of the interproximate gum septum, that this may be retained in health and vigor. To do this effectually, it is required that these fillings be finished to the full mesio-distal breadth of the teeth. Case. — A right upper first molar has a decay in its mesial surface, which has been discovered by the patient because of a slight breaking away of the mesial marginal ridge, disclosing the cavity. Examination with the exploring instrument shows the cavity to occupy about half of the mesial surface occluso-gingi- vally and the middle two-fourths bucco-lingually in its extension beneath the enamel, though the enamel opening is very much smaller. Procedure. — In these cases it always becomes a question as to when the rubber dam and the Perry separator shall be adjusted. It may be done first, or it may be done after the cavity has been opened and the outline form roughly cut. But it must always be done before the final shaping and trimming of the walls and margins of the cavity is undertaken. Opening the cavity. — With straight chisel 15, preferably by mallet pressure, though hand pressure may be used, begin chipping away the mesial marginal ridge of enamel overhanging the decayed area, first toward the buccal, and then toward the lingual, and continue until the enamel is found supported by sound dentin. In the cutting, especially if done by hand pres- sure, the edge of the chisel should be set very close to the mar- gin to be chipped, and the enamel cleaved off in little flakes, the direction of the pressure and the motion being almost in the line EXCAVATION OF CAVITIES BY CLASSES. »( of the length of the enamel rods, but slightly inclined in a direc- tion to throw the chips off from the free surface into the cavity. The instrument must be very sharp to be effective. Then cut away the enamel toward the central fossa, as far as it can well be done by the chisel. At this point it is well to take the enamel hatchets 15-8- 12, or 20-9-12 if there is sufficient room, and trim the overhanging enamel from the buccal and lingual walls of the cavity with a few strong, vigorous strokes, or the buccal wall may usually be cut with the straight or binangle chisel, using the enamel hatchet for the lingual wall. Then sweep the enamel hatchets around the gingival wall with a scraping motion, cutting to sound dentin. Note particularly that the enamel hatchet of the right bevel, to cut the lingual wall, 'should cut to the lingual in trimming gingival wall ; while the one with the right bevel, to cut the buccal wall, should move to the buccal in cutting the gingival wall. If the cavity is shallow mesio- distally, this will incidentally remove most of the carious dentin ; but that is immaterial. If the cavity is very deep mesio-distally, no further effort should now be made to remove the carious dentin. The outlines of the cavity are exposed, and that is sufficient. The next procedure is to cut a step in the occlusal surface for the retention, and complete the outline of the cavity in this direction. Select an inverted cone bur not more than one millimeter in diameter, and placing its shaft nearly or quite parallel with the long axis of the tooth, enter the bur sidewise into the dentin just beneath the dento-enamel junction, and draw it slowly to the occlusal surface of the enamel. Repeat this motion in cut after cut, following the mesial groove distally to the pit in, the central fossa. Then with straight chisel 15 or 20, or with the enamel hatchets, chip away the enamel from either side of the slot formed by the bur. Now pass the bur along the slot again, first pressing it strongly to the buccal so as to undermine the enamel, then pressing to the lingual, and again chip away the enamel both to the buccal and to the lingual. Repeat this until the step occupies the full middle third of the occlusal surface bucco-lingually to and including the pit in the central fossa. Now the buccal groove and other sharp grooves should be cut out as in the preparation of occlusal cavities. This gives a step with a flat pulpal wall and definite angles with its surrounding walls, and of perfect retentive form. »» THE TECHNICAL PROCEDURES IN FILLING TEETH. Next the proximate portion of the cavity must be extended. When the buccal and lingual walls have been cut away to sound dentin, it is often' necessary to extend them further. They should be cut well into the embrasures, both buccally and lingually, so that the cavity margin will be removed from near contact with the proximating tooth. When much sound dentin must be removed to accomplish this, it is easier to do it by intro- ducing an inverted cone bur into the dentin against the dento- enamel junction, about the bucco-lingual center of the length of the gingival wall, and carry it buccally to the buccal wall, squar- ing out the bucco-^ingival angle, and then, drawing it along the buccal wall toward the occlusal surface, undermine the enamel along this wall also. Then the undermined enamel is easily cut away with the enamel hatchets, or by chipping with the chisel used from the buccal angle of the tooth through the embrasure. Cut out and extend the linguo-gingival angle and the gingival wall in the same way and using the same instru- ments. A good rule as to the extent of the extension is to cut the lingual wall to a line where its margin will be in view, past the proximating tooth when looking across the central incisors at the median line, and make the extension of the buccal wall to correspond. In some instances it will be found that after this extension has been made, a line of superficial injury to the enamel extends beyond the margin of the cavity at one or both of its gingival angles. This should be carefully looked for, and when found, the cavity should be fur- ther extended so as to include the injured portion. It must now be determined whether or not the gingival wall has been sufficiently extended gingivally for its margin and its buccal and lingual angles to be covered by the free margin of the gums when the filling is finished. If not, it must be extended further to the gingival. This is difficult to do entirely with hand instruments, but by using an inverted cone bur with its flat end against the gingival wall, it is inclined sufficiently for its corner to engage, and carried, within the dentin, along the dento-enamel junction to the bucco-gingival angle, then inclined in the opposite direction it is carried into the linguo-gingival angle. In this way the enamel to the gingival is undermined and may be much weakened by passing the bur a few times with hard pressure against its inner side. It may then be removed EXCAVATIOX OF CAVITIES BY CLASSES. 89 with the enamel hatchets and the gingival wall be made horizon- tal and smooth. Its angle with the axial wall should be sharp and definite. Any decay remaining on the axial wall is now removed with spoons 20-9-12, or in this particular position with the discoid. The enamel walls are now planed to form. ' In all of the occlu- sal portion these may be perpendicular. On the buccal, the enamel wall must be inclined strongly to the buccal to agree with the enamel cleavage. The lingual enamel wall must be inclined similarly to the lingual. The inclination given the buc- cal and lingual enamel walls will depend upon their relations to the angles of the tooth. Generally the plane of the enamel wall should be perpendicular to the surface of the tooth at the partic- ular point where the enamel margin is laid. The apparent inclination will therefore vary with its position. If the cavity margin is carried far around the angle onto the buccal surface, the plane of the enamel wall will be nearly or quite in the bucco- lingual plane of the tooth. If a less distance, the inclination will be less. The gingival enamel wall should be inclined a little to the gingival. The cavo-surface angle of all parts of the cavity outline must now be beveled. All except the gingival and the rounding of the bucco-and-linguo-gingival angles may be done with the chisels. A special instrument is required for beveling the gingival cavo-surface angle, the gingival margin trimmers 20- ( 80) -g- 12 for mesial cavities and 20- (95) -9- 12 for dis- tal cavities. These instruments are used for no other purpose whatever. They have the angle of the edge cut purposely for making this bevel. A few strokes lightly made, and carried around the angle first with the right-hand instrument in the one direction and then with the left-hand instrument in the other direction, are sufficient. The cavity now only requires the toilet to be made^ to be ready for filling. However, most persons would prefer some convenience points in the gingival portion of the cavity for retention in starting a gold filling. These are made, one in the axio-bucco-gingival angle, and one in the axio-linguo-gingival angle, by pressing an inverted cone bur into the dentin slightly and drawing it a short distance to the occlusal along the bucco-axial line angle and the axio-lingual line angle respectively. These give sufficient starting 90 THE TECHNICAL PROCEDURES IN FILLING TEETH. points and will retain the filling while the building of this part is in progress. Variations due to position. — The variations of procedure due to position of the teeth in the mouth and the different degrees of exposure of the parts to view and to approach, relate mostly to the second and third molars and to the lower bicuspids. The upper first bicuspids are usually so well exposed that both the mesial and distal cavities are easily reached, and except that the smaller cutting instruments, as the 15-8-12 and 10-6-12 enamel hatchets and corresponding chisels and spoons, are neces- sary, the instruments and the instrumentation will be the same. Neither is it often necessary to make any variation in distal cavi- ties in the first molar or mesial cavities in the second molar, above or below. In distal cavities in the second molar and mesial cavities in the third molar it frequently happens that the inverted cone bur can not be made to approach the cavity at the proper angle to square out and extend the bucco- and linguo-gingival angles. In these cases the bur in the right-angle hand-piece may be substi- tuted, or the cutting may be done entirely with the hand instru- ments. However, in the greater number of cases in which distal cavities in the second molar are excavated at the same time with mesial cavities in the third, the straight hand-piece may be used for both. This is facilitated by cutting the step in the second molar first and carrying it well to the mesial. This gives addi- tional room for the application of instruments to the distal portion of the cavity and also to the mesial cavity in the third molar. Occasionally there is difficulty in so placing the inverted cone bur as to begin cutting the step in the occlusal portion from the distal cavity of a second molar. The approach is such that the shaft of the instrument is inclined so much to the distal that the bur cuts the enamel from the surface inward, instead of cutting the enamel from within outward, and for this reason will not cut well. The proper position of the bur may be obtained with the right-angle hand-piece, but if the enamel proves very hard this instrument does not work well. It is better in such cases to enter the occlusal surface through the pit in the central fossa in the usual way of opening pits, or with a drill, if the pit is fully closed, and then enter the inverted cone bur at this point and cut to the distal along the line of the distal groove until the EXCAVATION OF CAVITIES BY CLASSES. 91 distal cavity has been entered. This slot may then be broad- ened to the buccal and to the lingual in the usual way to form the step. The approach to distal cavities in the upper second molars is often somewhat from the buccal, and to facilitate this approach in building the filling the buccal wall should be strongly inclined to the buccal, whenever this can be done without very positive detriment to the case. One should never neglect to obtain such form as will render the filling of the cavity convenient. In the lower molars, especially those that have a strong lin- gual inclination, the form of the distal cavity may be made for filling with reverse pluggers. In this case the buccal wall may be cut parallel with the long axis of the tooth and the gold packed against it entirely with the reverse plugger. The greatest difficulty is met with in distal cavities in lower bicuspids that have a strong distal and lingual inclination. It is in these that a right-angle hand-piece and the reverse pluggers are most needed. These teeth are often small and the crowns long and decayed far to the gingival. They are difficult to reach with direct instruments. In these cases at least two teeth to the distal should be included in the rubber dam. Even if the first and second molars are lost, the rubber should include the third molar, to give good room for the use of the mouth mirror, for light, and to hold the rubber out of the way of instruments. It will then be found that the cavity is easily reached with hand- cutting instruments and the right-angle hand-piece, and is readily filled with reverse pluggers after having attained facility m their use. In the absence of reverse pluggers much of the filling must be made by hand pressure. The form of the cavity should not differ materially from the forms produced in other teeth. If, however, it is decided that direct mallet force is to be employed to the greatest possible extent, the disto-buccal angle of the tooth should be boldly cut away sufficiently to give access to the gingival wall and the greater part of the cavity walls gen- erally, and the step carried close against the mesial marginal ridge. This will allow a direct approach from the disto-buccal to all of the cavity walls except the axio-bucco-gingival angle, which must be filled by hand pressure. 92 THE TECHNICAL PROCEDURES IN FILLING TEETH. Management of Weak Cavity Walls in Molars and Bicuspids. In the lower molars, especially when the contacts are very broad, the proximate cavities are likely to be deepest toward the lingual, and to burrow extensively along the lingual dento- enamel junction. In these cases the lingual wall will be weak at the mesio- or disto-lingual angle of the tooth, and this not infrequently extends to the central line of the lingual surface. In all such cases the removal of the angle, including the lingual cusp, mesial or distal, is imperative. This should usually be done by catching the enamel near the margin of the cavity with the sharp edge of binangle chisel, and with a pull toward the cavity, split it off. This may be thrown off, chip after chip, easily, until a point is found at which it is supported by sound dentin, or strong enough for a filling to be built against it and restore .the lost contour with safety. In occlusal cavities in these teeth, the central pit in which decay begins is much nearer the lingual than the buccal surface, because of the rounding of the buccal surface toward the occlusal. For this reason the lingual enamel plate is often undermined and weakened in its central portion mesio-distally, even in cavities that are not very much extended in other directions. In these cases the lingual groove should be cut out over the crest of the marginal ridge and the marginal ridge itself removed well toward both the disto- and mesio-lingual cusps. The gap formed in the lingual wall may be built over and the form of the tooth restored. In both these cases the enamel wall remaining should be smoothly cut at right angles to the axial plane of the tooth. In the upper molars the buccal wall is more often the weak wall. This does not so often occur in case of occlusal cavities, though it is not infrequent. But often in mesial cavities the mesio-buccal angle is found badly undermined by decay. If the decay has spread along the dento-enamel junction or if the decay has reached the enamel and left it unsupported, the cusp should be cut away at once and be restored with the filling material. Often in mesial cavities decay will have extended far to the buccal without undermining the cusp, in which case an extension of the enamel margin will not meet the SEPARATING TEETH. 93 requirements without the removal of the cusp. In such cases the enamel wall should be finished in the bucco-lingual plane. In upper first molars, with large disto-lingual cusps, the contact point is often toward the lingual, and caries of the distal surface is therefore likely to begin in such position as to under- mine the linguo-distal cusp and weaken the lingual wall of the cavity. Also the disto-lingual groove is usually deep and sharply sulcate in these teeth, and forms a very weak line in the enamel. Therefore, unless the lingual enamel wall is found well supported by dentin, the cusp should be removed and the enamel cut away to the disto-lingual groove, and the cutting continued toward the gingival until good strength is found. In the upper bicuspids, the buccal angles are most likely to be undermined first because of the contact point being well toward the buccal, and the first beginning of decay occurring just to the gingival of it. When the angle, either mesial or distal, is so undermined that the enamel is unsupported by den- tin, it should be cut away to the buccal groove. This groove, though generally so well closed on the buccal surfaces of the bicuspids as not to be very apparent, is still a weak line in the enamel, at which it is more than usually liable to break. In addition to these special points of liability to weak walls, decay is liable to burrow in any direction, causing weak walls in other, and occasionally in unusual, positions. Any such are to be treated upon the general lines that have been indicated. It should be a rule that when a wall requires cutting away be- cause it has been weakened by decay, and, in the cutting, a developmental groove is approached, it should be cut to, or past the groo\'e. In mesio-occluso-distal cavities in the upper bicuspids, from which the pulp has been removed, the whole of the occlusal enamel plates should be removed to, and slightly over, their crests to the buccal and lingual, and be restored by filling material. This will bring the work of mastication entirely upon the filling material and prevent the weakened cusps from being split off. Separating Teeth. In filling proximate cavities in which the proximate tooth is present, provision must be made before the fill- ing is begun for finishing the filling. If the teeth originally 94 THE TECHNICAL PROCEDURES IN FILLING TEETH. made a close contact, it is necessary to separate them, or lift them a little apart in order that we may finish the filling to the full mesio-distal breadth of the tooth and restore the contact in correct form, preserving the full breadth of the interproximate space. This is necessary to the maintenance of the health of the interproximate gingivae, the gums, the peridental membranes and the teeth. If the contact of the filling with the proximating tooth is not made in correct form, food will be held between the teeth and will be crowded upon the interproximate gum tissue, causing inflammation and absorption, and finally injure the gums and peridental membranes, perhaps causing incurable disease and final loss of the teeth. Or, by forming a pocket in the gum tissue about the gingival margin of the filling, in which debris undergoes fermentative decomposition with acid formation, recurrence of decay is caused which destroys the filling and the tooth. These considerations, derived from careful clinical obser- vation, render it imperative that we make provision for finishing proximate surface fillings to very exact form by first separating them sufiiciently to give room to do this work. In all ordinary cases the separation of teeth to gain room for finishing is done best by the use of the Perry separator. This in- strument simply catches the two teeth by their necks and lifts them apart by turning a screw. The separation required is done with the least pain possible, is done at once, and without causing especial soreness of the teeth. Generally the separator should be applied before the filling is begun and the teeth separated sufficiently at once. Occasionally, and especially with the molar teeth, when the teeth are very firm, they are difficult to move sufficiently. If in such cases the separator is forced very tight, the instrument springs instead of separating the teeth, B.ut when it is allowed to remain and the filling is proceeded with, it is found that when the filling has been built and is ready for finishing the continuous spring force of the separator has caused them to yield sufficiently. "We should make note of this and be careful not to force the separator too hard upon the single-rooted teeth, for if we attain the full separation required at once we will find when the filling is completed that we have separated the teeth much more than was necessary. All of this you will learn intimately by observation in the infirmary. When the separator is applied, if the bows do not rest firmly SEPARATING TEETH. 95 upon the teeth they should be made firm by propping them with gutta-percha. To do this the gutta-percha is softened by heat and placed between the bows of the separator and the occlusal, or incisal, surfaces of the teeth, and allow a little time for it to harden before finishing the separation. This should be done at once when the separator has been made just tight enough to retain its position well, for in the after tightening of the screws there is a tendency for the claws of the separator to slip further to the gingival and, coming against the attachment of the peri- dental membrane to the neck of the tooth, cause unnecessary pain and some injury. This also prevents movements of the separator which causes the patient much pain and inconvenience while operating. The principal objections to the Perry separator are, first, that in the sets of six, as usually sold, there are not a sufficient num- ber of forms to accurately fit all kinds of cases ; second, that they are very expensive instruments ; and third, that there are many irregular cases with teeth so out of position that they can not be made to fit. This last objection will naturally attach to all mechanical devices for this purpose.* When the teeth are very irregular in the arch, other means of separation often have to be devised. Wedges of wood may sometimes be used, or cotton can be crowded tightly between the teeth and tied over or about the contact point with a ligature and accomplish a sufficient separation within a few days. Drawing slips of rubber between the teeth and cutting the ends short is a very efifective method of slow separation, but is apt to make the teeth very sore. In using rubber for separating great care should be had that the rubber does not press upon the gum septum. This not only creates unnecessary soreness, but is liable to do great injury to the gum septum. A method that is excellent for very slow separation in the molars and bicuspids is to excavate the cavity roughly and moisten its surfaces with eucalyptol to make the gutta-percha adhere to the walls, and then fill it solidly with gutta-percha, filling the interproximate space solidly against the proximating tooth. In doing this an instrument of some form should be NoTK.— A modified form of the Perry separator, universal in its application, is now under trial, which, if successful, will materially reduce the cost, as one instrument will take the place of the set of six. 96 THE TECHNICAL PROCEDURES IN FILLING TEETH. placed firmly in the interproximate space against the gum septum while the gutta-percha is being packed, and afterward removed. This will protect the gum septum from being absorbed by the continued pressure of the gutta-percha. This point should never be neglected, as a full gum septum is necessary to the health of the parts, and it should be carefully protected against injury. When the patient is discharged temporarily he should be directed' to make vigorous use of the tooth in chewing. The impact of the food will cause the gutta-percha to spread and carry the teeth' apart sufficiently within a week or two. This is a very effective method of slow wedging in cases in which the teeth have dropped together from loss of the contact point, and has the merit of moving the teeth without creating soreness. In cases requiring much movement it can be hurried a great deal by first putting on the Perry separator and lifting the teeth apart as much as possible, and making the gutta-percha filling, as indicated above, and giving sufficient time for the gutta- percha to become fully hard before removing the separator. This may be repeated at intervals of two or three days until sufficient separation has been obtained to fully restore the width of the interproximate space and mesio-distal breadth of the tooth. It occasionally happens that a tooth has lost the greater part of its crown, and the teeth on either side have dropped together over it, so that the restoration of the form of the crown is impossible without a very considerable separation. In this case the breadth of two interproximate spaces are to be recovered by separation. If the lingual and buccal walls are still sufficiently strong, it is still possible to accomplish this with gutta-percha, but when they are not it is better to cut away most of the remaining portions of the crown, and insert a piece of hard, dry hickory wood in place of the missing crown in such a way that the length of the grain of the wood shall be from buccal to lingual. This should be cut to fit snugly between the two teeth on either side, and forced into position. This will absorb mois- ture from the saliva, and swell and slowly carry the teeth apart. The wood should be exchanged for a new piece once in two or three days, and continued until space is gained for the restora- tion of the full mesio-distal breadth of the crown. This plan is especially useful in gaining the necessary space for restoration FILLING MATERIALS. 97 with artificial crowns, as well as in building up badly decayed teeth with metal. Filling Materials. The fining materials at present in use for permanent opera- tions are, gold, which holds the first place, and amalgam, which holds a second place, in value. Added to these many would reckon tin as holding a place equal or nearly equal to amalgam, but the. general judgment of the dental profession would seem to consign tin to a very obscure position as a filling material, as nowadays very few persons make much use of it. The filling materials for temporary operations are the cements, especially the oxy-phosphate of zinc cements, and gutta-percha. The qualities most desired in a filling material for permanent operations are indestructibility in the fluids of the mouth, adaptability to the walls of cavities, freedom from shrinkage or expansion after having been made into fillings, and resistance to attrition and the force of mastication. The qualities of secondary importance are color, or appear- ance, non-conductivity of the thermal impressions, and conveni- ence of manipulation. Of these first qualities gold seems to possess in much the greatest degree those most essential. It is perfecdy indestructi- ble in the fluids of the mouth; it is very perfecdy adaptable to the walls of cavities; it is free from objectionable shrinkage or expansion ; its resistance to attrition is good and it resists the force of mastication better than amalgam. Of these second qualities gold is not so good. It conducts thermal impressions strongly, its yellow color is objectionable, and it is not very convenient of manipulation. Indeed, it may be said of this last quality, that its successful manipulation requires much study and careful experience, and yet, when this study is given it and the required experience has been obtained, it may be worked into fillings more perfectly than any other material. Amalgam, as alloys for which are at present produced by the best makers, is possessed of the first (jualities in a high degree, yet inferior to gold in all. It is not completely inde- structible in the fluids of the mouth, but oxidizes or sulphurets slightly, just sufficient to change its color from a silvery white- ness to brown or black. Its adaptability to the walls of cavities 7 98 THE TECHNICAL PROCEDURES IN FILLING TEETH. is not SO perfect as that of gold, though apparently so easy - when used in a very plastic state as to be very deceptive. Much careful study and experience are required to work it well. Its resistance to attrition is good, but its capability of resistance to the force of mastication is less than that of gold. Much of the difficulty attending the use of amalgam arises from a lack of an understanding of its qualities. It is a metallic compound in which each element entering into its composition exerts its special influence upon the qualities of the product; and these qualities are varied with every little change in its composi- tion. These changes of qualities and the laws controlling them are as yet understood by but few makers of amalgam alloys, and are not generally understood by the dental profession. For these reasons dentists are in constant danger of using amalgam alloys with which good fillings can not be made because of shrinkage or expansion of the material after being made into fillings. In secondary qualities its color is bad, so bad indeed that it should never be used in the anterior teeth on this account. Its conductivity of thermal changes is nearly equal to that of gold. Its working qualities render it much more convenient than gold in very large and difficult cavities. It can be placed much quicker, less expenditure of force is required, and much less time, but ordinarily perfection of adaptation is less certain. Forms of Gold. Gold is prepared in the form of foil for filling teeth. This foil is prepared in various thicknesses, which are rated on the basis of the number of grains in the sheet four inches square. If a sheet of this size contains two grains it is called No. 2; if three grains. No. 3; if four grains. No. 4, and so on up to what is known as the heavy foils, such as Nos. 30, 60, 120, etc. Gold is also prepared for use in filling teeth in the crystalline form. These crystals are put up in various kinds of masses, with about as many names as there are makers, and in these forms possesses certain desirable qualities, especially convenience of manipulation. In any of these forms, however, it is much less readily kept in good working condition than foil, and for this reason is not so certain in its working properties. It often fails to weld perfectly, and especially it is often unreliable in FILLING MATERIALS. 99 adaptation to the margins of cavities. Great effort has been made to bring this form of gold into general use, but the gen- eral judgment of the dental profession has seemed to be against it, for foil has always maintained its position as the form of gold most used. Welding Properties of Gold. Gold prepared in the form of foil or crystals welds perfectly in the cold state when clean surfaces are pressed into contact. It is the only metal which has this property in a high degree. In order that the welding property may be successfully used the surfaces of the gold must be clean. As this property of gold is readily lost by improper care, it is well to know intimately the conditions of the develop- ment of it, and the loss of it. All metals, except those known as the noble metals, oxidize quite readily when exposed to the air ; that is, they attract the oxygen of the air and unite with it to form a film of oxide upon the surface. This prevents the contact of clean surfaces and therefore prevents welding. Gold, silver, platinum and mercury do not oxidize in this way, and it is for this reason that they are called noble metals. Silver and platinum do, however, attract oxygen to their surfaces in the form of a transparent film of con- densed gas sufficient to prevent their surfaces from coming in contact, which prevents them from welding cold. Gold does not attract oxygen nor nitrogen to its surface and it is for this reason that it can be welded cold. Gold does, however, attract to its surface certain gases that are often present in our atmosphere in such quantities as to prevent its surfaces from coming in con- tact, and destroy, temporarily or permanently, its welding properties. Some of these gases are such as will Ije removed from the surface of the gold by volatilization when heat is applied (by annealing;, rendering the surface again clean with restoration of welding property. Other gases, notably those of the sulphur and phosphorus groups, condense upon the surface of gold and refuse to volatilize by heat, and in that case the welding property of the gold is permanently destroyed. In these cases it seems probable that compounds in the form of fixed salts — non-evaporablc — are formed on the surface of the gold. 100 THE TECHNICAL PROCEDURES IN FILLING TEETH. These general facts with regard to gold may readily be illus- trated by a few simple experiments, which any one can perform. Ammonia is strongly attracted to gold. Place a small quantity of spirits of ammonia, or of aqua ammonia, in a large glass jar. The ammoniacal gas from this will fill the space above the liquid. Now take a rope of gold which has been annealed and the weld- ing property of which is perfect, and swing it by a thread above the liquid in the jar and replace the cork. In fifteen minutes remove the gold and try its welding property. It will not weld any more than so much tissue paper. If it is swung above chlorine water the welding property will be completely destroyed in two minutes. Now reanneal these ropes of gold ; the welding property is completely restored. How are we to know that this effect is produced by a condensation of gas on the surface of the gold ? Place the gold first in chlorine gas for ten minutes, and then transfer it to ammonia for an equal time. Now, as these two gases unite to form a volatile salt, ammonium chloride, which readily crys- tallizes upon any cold substance, place the gold thus treated in a long test tube, and heat it quickly over a bunsen burner. Immediately white fumes begin to leave the gold, and these crystallize in a white ring on the colder portion of the test tube. Chemical examinations of these crystals show them to be ammo- nium chloride. This could occur only by the condensation of the gases on tha gold, and the amount formed shows this con- densation to be in very considerable quantity. The experiment may be varied by placing the gold first in the gaseous ammonia, and then transferring to the chlorine, but in this case there will not be so large an amount of the ammonium chloride formed, for the reason that the ammonia is not condensed on the gold in so large a quantity as the chlorine. In this experiment the salt formed is volatile, and the gold is readily cleaned by heat. But suppose the salt formed were a fixed salt that we can not volatilize by the annealing temperature ; then the welding property of the gold is permanently destroyed. This is what often occurs when the gold is not well protected. Now one of the principal reasons why the crystalline forms of gold are more difficult to keep in good condition than foil, is the fact that the crystals form a sponge that more readily takes up and holds gases. FILLING MATERIALS. 101 By careful experiment it has been found that acid gases are most likely to permanently obscure the welding property of gold ; hence, if the gold be kept in an atmosphere containing a liberal per cent of ammonia, ammonium salts will be formed on the gold. These salts are readily volatile, hence, gold so kept will always be readily cleaned by annealing and its welding prop- erty restored. "We may use gold, non-cohesive or cohesive, as we choose, from the same book, or the same sheet, by sim- ply keeping it in a dra-wer containing a small bottle in which a bit of sponge, punk or cotton is placed and occasionally saturated with spirits of ammonia. Used without annealing this w^ill be perfectly non-cohesive, or when annealed will be perfectly cohesive. This should be taken advantage of in keeping gold in good condition for use in either form. Annealing Gold. Gold is annealed to develop its welding property. This annealing is not for the purpose of softening the metal, as in annealing plate, but for the purpose of cleaning the surface of the gold by volatilizing any gaseous film that may have' collected upon it. This purpose is explained sufficiently in the preceding article. The best means of accomplishing this will depend some- what upon circumstances. For the general work of filling teeth the annealing is very well done in the flame of the alcohol lamp or the flame of a small bunsen burner. The element of time is important in annealing, particularly if the annealing is done at low temperatures, for the gases are not driven off" at once unless a full red heat is obtained. Therefore, in annealing in the flame the gold should always be brought to a glow, and so held for a moment or two. It is also necessary to the best results that every particle of the gold be brought to a glow. In taking up the gold with the pliers, that portion of it that is caught between the beaks, and that very close to the beaks, will not be heated sufficiently to develop its welding property. This will introduce into the filling spots of failure to weld and greatly impair the strength of the work. For this reason great care should be exercised in annealing to see that all parts of the gold are brought fully to a glow. This is especially important when 102 THE TECHNICAL PROCEDURES IN FILLING TEETH. a corner is to be built up, as in the restoration of the angle of an incisor, or when a very solid surface is to be made, as upon the occlusal surface of a molar that will receive severe wear. Pitting of the surface of fillings is in a large degree the result of the introduction of bits of gold that have not been sufficiently annealed. To prevent the possibility of this it is well to first anneal one part and then lay down the piece and catch it at another point and anneal again. W^hile the gold should be heated to redness, it should not be heated to the melting point. This ruins the plasticity of the foil and makes it impossible to properly condense it. To avoid these difficulties the gold may be annealed upon a tray over the flame of the lamp. A number of devices for this purpose can be had, most of which are convenient and eflective. The tray may be made of metal, of porcelain, or of mica; it does not seem to make much difference which is used. In annealing in this way the gold may conveniently be exposed to the heat for a considerable time, and therefore a full red heat is not necessary to the complete development of the welding property, so that there is no danger of hardening the gold by melting portions of it. However, the heat must closely approach the point of red- ness to be effective. Another advantage is that all parts of the gold will become annealed. The disadvantages of this method are, the presence of such an apparatus upon the bracket which is needed for operating instruments, and that the gold spread upon the annealing tray is liable to movement by every motion, or in the eflbrt to lift pieces from it, and roll together and stick to each other in such a way as to cause much annoyance and delay in handling it. Much of this annoyance can be avoided by having a tray that is so roughened as to prevent the rolling or sliding of the gold. Filling with Gold. In filling teeth, cohesive gold or non-cohesive gold may be used, or the cavity may be partly filled with non-cohesive gold and finished with cohesive gold. Filling with Non-Cohesive Gold. Filling with non-cohesive gold for the entire cavity is prac- ticed but very little nowadays, apparently for two reasons. It requires the development of a different order of skill from that FILLING WITH GOLD. 103 required for cohesive gold, which is somewhat difficult to mas- ter, and it can not be used for contouring or even in filling to form in cavities that have lost one or more of the surrounding walls ; for in this manner of filling the principle of wedging the gold between the surrounding walls is depended upon to retain the gold. For this purpose only foil is used and its lamina must extend from the floor to the surface of the cavity. Either the form of the rope or cylinders may be used. In this form of fill- ing the gold is not annealed. With our present ideas of pre- paring cavities, only occlusal and buccal or labial ca\ ities that have complete and good surrounding walls would be suitable for non-cohesive gold work. The forms in which we now prepare these are as suitable for non-cohesive as for cohesive gold, only that no convenience points for starting the filling are required for non-cohesive gold. In filling an occlusal ca\ity in a molar with non-cohesive gold cylinders we would prepare these so that the length of the cylin- ders should be a litde greater than the depth of the cavity. Some should be large and some small, the size of the larger ones depending upon the size of the cavity. Begin with the cylinder which, as loosely rolled, would about fill the cavity full. Set this in the cavity with one of its ends standing upon the pulpal wall and the other protruding from its orifice. Now, with the side of a large plugger press the cylinder against the distal wall. Set another cylinder in in the same way and condense it against the first. Repeat this by adding cylinder after cylinder until the distal half or more of the cavity is filled. Then continue by condensing the cylinders against the mesial wall, and in turn the buccal and lingual walls, all the time using the lateral pressure with the side of the plugger point, not with its end. As the work progresses and the cavity room is narrowed, the cylinders intro- duced must be smaller and smaller. Finally, to obtain room for additional cylinders, a sharp point of a wedge form must be pressed to the floor of the cavity and with a prying motion the gold is wedged against the cavity walls in every direction with great force. The space thus gained is again filled with small cylinders and the wedging repeated so long as it is possible to force in another cylinder. The small cylinders last introduced should be rolled very hard. When it is no longer possible to force another cylinder into the central portion of the cavity, 104 THE TECHNICAL PROCEDURES IN FILLING TEETH. efforts should be made at various points to force in the sharp, wedge-shaped point and any opening made filled with a small cylinder. When no more gold can be introduced the whole sur- face should be condensed as completely as possible with the end of a finely serrated plugger. Then the surplus gold should be trimmed partially and the condensation repeated. Then again, trim and condense, repeating this until the surface of the filling is brought to proper form, with its margins just flush with the cavity margins. Generally these fillings should be finished with the burnisher. Instead of the cylinders, ropes of foil may be used by carry- ing an end to the bottom of the cavity and folding in fold after fold, so that one end of the loop is on the floor of the cavity and the other protruding from the orifice. These loops are con- densed against the walls laterally and finally condensed by wedg- ing, the same way as in filling with cylinders, filling the space gained by other loops. The filling is finished in a similar manner. In filling buccal or labial cavities with non-cohesive gold the steps of the procedure are practically the same as in filling occlusal cavities. However, the operation is generally rather more difiicult in these, for the reason that the cavities are so gen- erally of less depth in proportion to their breadth. The most convenient cavity to fill with non-cohesive gold is one in which the depth is nearly equal to the breadth. One who has become skilful with this manner of manipulating non-cohesive gold can make gold fillings in cavities suited to this work in much less time than they can be made with cohesive gold. This plan of filling is often very desirable for first molars for children, and in various cases that come up in practice when it is important to shorten the time of the operation. These non-cohesive gold fillings do not stand attrition so well as cohesive gold fillings in positions where great wear comes upon them. They are, therefore, more suitable for buccal and labial cavities. If very well done, however, they do excellent service in occlusal cavities where the wear is not extraordinary. It is the general opinion of those who use much non-cohesive gold that water-tight margins are more certainly made with it than with cohesive gold. I am satisfied that this is correct. With the same care and skill more gold can be put into a cavity FILLING WITH GOLD. 105 of a given size, using non-cohesive gold, than can be done with cohesive gold. The Application of Force in Filling with Cohesive Gold. In using cohesive gold in filling teeth all parts of the gold should be welded into one solid mass. This is accomplished by using the gold in small masses and condensing each of these perfectly upon preceding masses with the end of the plugger point, by either hand pressure or the blows of the mallet. The use of hand pressure with sufficient force to accomplish this well, or to obtain the necessary degree of solidity, while it can readily be done, becomes exceedingly tiresome to both the patient and the operator. For this reason mallet force has come into general use. The kind of mallet used for condensing the gold seems to be of much less importance than the particular manner of handling it, and this last must be stated as being a personal equation. That is to say, one person will accom- plish a given condensation of gold with much less inconvenience to the patient than another can do, and yet, the differences in the application of force are not such as permit of analysis and a determination of the precise differences in manipulation. Of the different plans of applying mallet force the hand mal- let used by an assistant is by far the best, as it will produce the desired result with the least wear and tear to both patient and operator. The next best, but much inferior method, is by the use of the automatic mallet. Of these instruments there are a variety in the market of almost equal merit. The poorest method practiced is the use of the hand mallet by the operator himself In this use of the mallet he can not handle either the plugger or the mallet properly, and the usual result is great wear and tear upon both patient and operator, and generally much imperfect work in condensing the gold, especially in its adaptation to margins. In order to condense gold well, and with the least pain to the patient, the mallet force should be combined with a certain degree of hand pressure. The plugger should be placed firmly in position with such force as to bring the looser portions of gold well together, and to force the tooth into a stable position in which the fibers of the peridental membrane are rendered tense, and then the blow from the'mallet follows on the instant this is 106 THE TECHNICAL PROCEDURES IN FILLING TEETH. done. Experience has, I think, sufficiently shown that the best results are obtained by this method. This is in a good degree copied with the automatic mallets. The sliding of the plugger point over the surface of the gold while blows are being rapidly applied is very much more painful to the patient if the same results in condensation are accom- plished. A number of machines for this kind of malleting have been devised that are very convenient in use, and yet they seem not to be much used, evidently for the reasons I have assigned. It is perfectly practicable, however, to make good gold fillings by any one of these plans of using mallet force. The main questions here are as to ease and rapidity of manipulation in the first instance, and, in the second, as to comparative ease of obtaining good results. In most fillings hand pressure should be used in the conden- sation of some particular parts to which mallet force is inapplic- able. Mallet force can be applied successfully only in a direct line with the shaft of the instrument. In all cases, in which it becomes necessary to apply force in lateral directions to the shaft of the instrument, hand pressure must be used, unless reverse pluggers can be substituted. This can be done in the more difficult positions in lower molars and bicuspids by judicious study of the capability of reverse pluggers. The fill- ing of the incisal anchorage in incisor cavities requires almost uniformly the use of hand pressure. The manner in which we now prepare cavities for filling reduces the necessity for the use of hand pressure more than ever before, because of the very free access obtained. Conven- ience in placing the filling material should always be held strictly in view in the preparation of a cavity. The Relation of the Size of Plugger Points to the Applica- tion of Force. A correct appreciation of relation of the size of the condens- ing area of the plugger point to the force used is of first impor- tance in filling teeth with cohesive gold. The force that can be applied is limited by the capability of the peridental mem- brane to resist, and the possibilities of the use of more or less force will vary with the strength and endurance of the mem- brane. People who have very strong peridental membranes FILLING WITH GOLD. 107 and are accustomed to using their teeth very vigorously in chewing food, will bear much heavier blows of the mallet than those who have weaker peridental membranes and habitually use their teeth more delicately. All of this must be considered in filling operations and the force used limited accordingly. A point of no less importance is the requirements as to solidity and strength of fillings for different persons. Persons with strong peridental membranes who use their teeth vigor- ously require the strongest possible fillings. Persons who have weak peridental membranes and who habitually use their teeth feebly will not require the same solidity and strength in the fill- ings in order that they may stand. In either case, however, the adaptation of the gold to the margins should be the same, and in all cases a density that will be moisture-tight is absolutely required. Because a patient can bear heavy blows of the mallet is no excuse for using a plugger of large impacting area, for the reason that such persons require very dense fillings. For condensing the main portions of a cohesive gold filling the impacting area of the plugger should never be more than one square millimeter, and generally plugger points of one-half to I'a millimeter area should be used. The area of a plugger point is practically the square of its diameter. That is, a point one millimeter in diameter has an area four times as great as one- half millimeter in diameter. Five-tenths multiplied by five-tenths gives twenty-five as the area, while ten-tenths multiplied by ten- tenths gives one hundred, or four times as much. This being true, a reduction of the size of the plugger point below one millimeter increases the condensing power of the impact in pro- portion to the square of the reduced area, and increasing the size of the point above one millimeter diminishes the condensing power of the impact in proportion to the square of the increased area. Twenty-five pounds impact or pressure on a point one- half a millimeter in diameter is equal in condensing power to one hundred pounds upon a plugger point one millimeter in diameter. Therefore, to make solid fillings small condensing points must be used. We must not, however, use points that are so small that they will penetrate the gold and chop it instead of 108 THE TECHNICAL PROCEDURES IN FILLING TEETH. condensing it. Therefore we should not use heavy blows with very small plugger points. For some special places about mar- gins, or packing in delicate grooves, a smaller point used with lighter force is useful. And occasionally a larger area than one millimeter in the form of a foot may be useful in packing over certain cavo-surface angles. Forms of plugger points. — The form of the impacting area or points of plugging instruments may be round, square, parallelograms, or what is known as the foot forms. All of these have their uses in special localities. For the general work of building cohesive gold either the round, square or parallelogram forms may be used. The foot forms are not suited to general building of gold, but are useful for condensing over certain cavo- surface angles and for after-condensation, especially where it is necessary to reach into the interproximate space, or at other nar- row points requiring a short crook of the plugger point. The parallelograms, or narrow flat points, are especially useful in condensing gold against the surrounding walls of cavities when the direction of force must be nearly or quite parallel with the cavity wall, for the reason that they tend strongly to wedge the gold between the wall and the condensed gold and perfect the adaptation to the wall. For this purpose the flat side of the plugger point is placed parallel with the wall. The point or impacting area of the plugger may be smooth (smooth plugger), or serrated (serrated plugger). Gold fillings may be made with either, but for general use the judgment of the profession seems to be decidedly in favor of the serrated point. The principal object of the serrations is to prevent the point from slipping or sliding on the gold, and they should be just sufficient to do this eifectively. Long, sharp serrations should not be used, because they chop into the gold. ^Very fine, short serrations are much the best. Great care should be taken to keep plugger points in good order. Forms of the shanks of pluggers. — As we now prepare cavities with broad, free access, no great variety of crooks and turns in the shanks are necessary. In the instruments for gen- eral use a slight bend in the shank is desirable in order that the shaft may be just a little out of the line of vision. A perfectly straight plugger is a little awkward for that reason. This curve should be from three to five centigrades. For special purposes FILLING WITH GOLD. 109 we need some special forms of shank. Especially in filling upon the gingival walls of proximate cavities in the bicuspids and molars, a straight or nearly straight plugger would necessarily bring the angle of force almost perpendicular to the plane of the wall. In order that a more desirable angle of force may be had, a contra-angled shank is provided that will reach over the proximating tooth and permit an inclination of about twelve cen- tigrades of the angle of force toward this wall. In your sets there is a pair of these in parallelogram forms of impacting area in which the width of blade is in opposite directions to the plane of the curves of the shank. For filling the incisal anchorages of incisor cavities an angle of twenty-five centigrades (a right-angled plugger) is provided which is used entirely by hand pressure. This instrument, though used only for this one purpose, is a necessity to every outfit. These are, with the exception of the foot pluggers, the only curves of shanks required, and are quite sufficient for ordi- nary filling operations. In addition to these the school has provided reverse plug- gers of several patterns, which are issued upon order of the demonstrators for use in some especially difficult positions. These are occasionally needful for certain positions in filling lower molars and bicuspids, especially for packing against buccal walls in teeth that have a strong lingual inclination. List of Pluggers Required. University No. 4, 5x10-3-3 ) Face rounded on dimension lo ; University No. 5, 10x5-3-3 ^ serrated. University No. 6, 4x6-5-5 I University No. 7, 6x4-5-5 ^ ^^""^ ^""^ ' ^'^'''^^^'^■ University No. 9, 6x12-6-10) Contra-angled ; face rounded on University No. 10, 12x6-6-10) dimension 12; serrated. University No. 14, 5-2-23. No. 7, 5-10-3 I No. 8, 7-10-3 - Round. No. 9, 10-10-3 3 No. 322, 4x4 Bayonet ; serrated. ^o- 393. 5x20. Angle of face 20 ; serrated. No. 408, 5x20-5-15 I VarneyNo. 5, 5x15-3-6 )^'°°^- 110 THE TECHNICAL PROCEDURES IN FILLING TEETH. I Special Holding Instrument. I Weston's Plugging Assistant. I Automatic Plugger. Starting cohesive gold fillings. — In treating this subject I will suppose that the cavity has been prepared as has been directed in the article on cavity preparation, and that the con- venience points have been arranged for the beginning of the filling. Begin the filling in the most convenient angle of the cavity. In occlusal cavities this will usually be at some point along the pulpo-distal angle. In proximate cavities it will usually be the linguo-axio-gingival angle. In buccal cavities it will usually be the axio-disto-gingival angle. In labial cavities it may be either the axio-gingivo-mesial or the axio-gingivo-distal angle, etc. Select a plugger point that will easily go into all parts of the convenience point with which to condense the first piece of gold, and have the holding instrument or the assistant plugger ready in the left hand. Select a piece of gold rope, cylinder or block, that seems rather large for the conven- ience point, and see to it carefully that it is well annealed. Convey it to the point with the annealing instrument and catch it with the assistant plugger ; hold it so while the annealing instrument is exchanged for the plugger selected, and with the two bunch the gold carefully into the angle and catch it with the assistant plugger in such a way that the condensing instrument will have free access to the convenience point. Now, condense the gold into the angle by a few quick blows of the mallet, beginning in the central portion, and drawing the outlying parts of the gold into the angle with the subsequent blows. If the convenience point has been correctly formed this first piece will seldom need to be held afterward, but sometimes a second and a third piece should be added while still holding the gold with the assistant plugger. In case the operator is using a hand mallet with his own hand this first condensation must be done by hand pressure. The first piece of gold should always be sufficient in quantity so that the plugger point will not come in contact with the dentin. The plugger point should never punch through the gold. Remember that if the bottom of your convenience point is round, as made with a round bur, this first piece of gold will roll, but if the bottom is FILLING WITH GOLD. Ill well squared, as made with an inverted cone bur, this first piece of gold will remain firm. Next proceed to build up a mass of gold upon the first piece and extend this along one of the axial or pulpal angles to the second convenience point and unite the two. When this has been done the lodgment of the gold should be so secure that there will be no further fear of movement and the body of the filling may be built upon this foundation. If the case is an occlusal cavity the building should at first be about equally upon the pulpal and distal walls, forming a triangular mass filling the disto-pulpal line angle and extending to the buccal and lingual walls. Later, after the anchorage has been made still more secure by some building across and across against the lingual and buccal walls, the building should proceed more rapidly upon the pulpal wall until this is covered and the gold brought securely into all of the pulpal line angles. In no case should there be any attempt to spread a thin layer of gold on the pulpal wall, or any other wall, of a cavity and condense it in a thin sheet. Any such attempt insures a failure of perfect adaptation to the wall of the cavity. Always secure a thick mass of gold along a line angle and build out on the wall gradually, keeping the thickened mass close to the margin of the building as it progresses over the wall that will keep the margin from curling away from the wall as it is condensed. The angle toward the plane of the wall at which the con- densing force is applied is very important in making perfect adaptation. The direction of force should never be perpendicular to the plane of the wall that is being covered. Whenever possible the angle of force should be inclined as much as twelve centigrades from the perpendicular to the plane of the wall. In adapting gold to the surrounding walls in an occlusal cavity the direction of force should be inclined toward the wall, "if possible, as much as six centigrades. It is quite possible, by using the wedging principle, to secure good adaptation if the angle of force is parallel with the wall, but it is more difficult. 112 THE TECHNICAL PROCEDURES IN FILLING TEETH. The Wedging Principle. The stepping of the plugger should always be from the central part of the mass of gold toward the walls, and the last condensation of each individual piece of gold added should be along the wall being covered. This rule is practically universal to filling with cohesive gold, except when condensing pieces laid upon central parts of the filling, no portion of which is condensed against a wall of the cavity. When the stepping of the instrument is toward the wall, finishing the condensation against the wall, the last of the gold is w^edged betw^een the w^all and that last con- densed, thus securing perfect adaptation to the wall. If, on the other hand, the condensation is begun at the wall, the tendency is to pull the gold away from the wall in moving from it in the condensation of the remaining portions, and to make imperfect adaptation. In condensing each piece of gold added the stepping of the plugger point should be in a regular order, moving only the width of the condensing point at each step, con- densing every portion of gold. Regular lines of movement or stepping should be formed generally parallel with the wall that is to be approached, finishing along the wall. Such an order of work, pursued with regularity, secures speed in operating, and accuracy of adaptation of the gold to all parts of the cavity walls and margins. In the approach to and covering margins, great care should be had not to step the instrument onto the cavo-surface angle of the cavity. If this is done the cavo-surface angle of the enamel will be chipped and rendered imperfect. As the margin is approached the gold should be laid over the cavo-surface angle in sufficient quantity to admit of malleting directly upon it, without danger of the plugger point punching through it and making contact with the enamel. This requires that the gold be built completely over the margin at every point before the filling is regarded as completed. In finishing the building of the gold to form there should always be an excess to allow for sufficient trimming to remove all instrument pits and marks. It requires much care and good FILLING WITH GOLD. 113 judgment to always have sufficient gold for a good finish, and not have a wasteful surplus. The Gingival Wall in Proximate Cavities. The management of the gingival wall in proximate cavities, especially in the bicuspids and molars, has always been the great stumbling-block in filling operations. It is confessedly the most difficult point at which to secure perfect adaptation of gold, or, indeed, any other filling material. In part, this difficulty has been from imperfect preparation of this wall, but the real diffi- culty in securing adaptation lies in the fact that the tendency is to apply the condensing force in a line per- pendicular to the plane of that wall. To make perfect adaptation it is necessary that the angle of force be inclined as much as twelve centigrades to the plane of the wall. In mesial cavities in bicuspids and molars this is easily accomplished by using the contra-angled pluggers which are made for this especial purpose. These instruments will reach over the proximating tooth and give the correct angle of force. The filling is begun in the convenience points, and these are con- nected along the axio-gingival angle, as has been described. Then the building proceeds about equally upon the axial wall and the gingival wall, creeping slowly over the gingival wall until its cavo-surface angle is reached and has been built over; always keeping a thick margin of gold to build against while covering the wall and cavo-surface angle. During this building the plane of the surface of gold being built should be inclined about twelve centigrades toward the long axis of the tooth, one margin of this plane being upon the gingival wall, and the opposite margin against the axial wall in a direction toward the occlusal surface in the central fossa, if a molar, and a similar direction if a bicuspid. When the gingival wall and its cavo-surface angle has been fully covered, then the building may be more rapid in the prox- imate portion, and the plane of the gold be brought parallel with the horizontal plane of the tooth. The mesial portion of the filling is then extended to the mesial to make the contact with the proximating tooth. The rest of the filling is done according to rules previously given. 8 114 THE TECHNICAL PROCEDURES IN FILLING TEETH. In distal cavities in bicuspids and molars it is more difficult to obtain the best angle of force, and often the building must proceed differently. The angle of force inclined from the distal toward the mesial can not generally be obtained, and it is necessary to substitute an inclination from the buccal toward the lingual. In the beginning, build a thick mass of gold in the axio-linguo-gingival angle, and gradually extend it out to the cavo-surface angle of the cavity at that point ; then continue the building, keeping the plane of the surface of gold being built sloping occluso-gingivally from lingual to buccal, gradually covering the gingival wall and its cavo-surface angle, until the bucco-gingival angle is reached. Then wedge the gold into the bucco-gingival angle, between the gold already built and'the buccal wall. After this is accomplished the build- ing will proceed without especial difficulty. In accomplishing this the greatest difficulties will be found in lower bicuspids that have a distal and lingual inclination, and occasionally in lower molars that have a strong lingual inclination. In these the reverse pluggers are a necessity to easy and safe w^ork. With these the procedure is the same as in mesial cavities, except that the order is reversed, as the left hand is the reverse of the right. Begin in the axio-bucco-gingival angle and work along the axio-gingival angle to the lingual, and generally fill the axio- linguo-gingival convenience point with a direct plugger. After this is accomplished the building is not difficult. In making these fillings entirely with direct pluggers, hand pressure lateral to the direction of the shaft of the instrument is often necessary in starting the filling, and in building over the gingival cavo sur- face angle, and also in much of the building against the buccal wall. In proximate cavities in the incisors and mesial sur- faces of the cuspids, no great difficulty will be found in gaining the proper angle of force in building over the gingival wall and its cavo-surface angle. These, like all other gingival walls and margins, should be covered only after having secured a mass of gold in the axio-gingival line angle, and then keeping the plane of the surface of gold being built sloped at an angle of about twelve centigrades to the long axis of the tooth until the gingival wall and its cavo-surface angle are covered. FILLING WITH GOLD. 115 Combination of Non-Cohesive and Cohesive Gold in Proximate Cavities in the Bicuspids and Molars. Combinations of non-cohesive and cohesive gold may be used effectively in many positions in filling teeth, but I attach great importance to it only in the gingival portion of proximate cavities in the bicuspids and molars. The best cohesive gold workers fail, when they do fail, oftenest at this point. And so difficult is it to make perfect adaptation of cohesive gold to this wall that my observation teaches me that our very best men fail in ten per cent of their cases. A much larger per cent of success can be obtained by the combination of non-cohesive foil, with a saving of both time and labor. This is sufficient reason why I should urge this plan of filling. It is not, however, an easy matter to learn this method. It will not be gained without careful study and effort in practice. This combination consists of laying a large flat cylinder or mat of non-cohesive foil on the gingival wall and then beginning upon this to build cohesive gold. The beginning and continuation of the building with cohesive gold is the same in every respect as if the non-cohesive gold had not been used, except that it will be necessary to continue the use of the assistant plugger for a longer time before the mass is perfectly secure in its position. The flat cylinder or mat is made by first folding a sheet foil, or such part of a sheet as may be required, to the right width, and then rolling the ribbon formed upon a flat steel instrument of suitable width. The length of the cylinder is controlled by the width of the ribbon, and the breadth is controlled by the width of the flat instrument. The length should be such that when placed flat upon the gingival wall with one end against the axial wall the other end protrudes over the gingival cavo-surface angle of the cavity. The breadth should be such that it will extend fully from the buccal wall to the lingual wall and require some crowding to make it lay flat. Simply lay this in position and begin building upon it, practically as has been described for beginning with all cohesive gold. Instead of this flat cylinder or mat, ordinary round cylinders may be used by laying the first in the linguo-gingival angle, a second in the bucco-gingival angle, and a third between the two. 116 THE TECHNICAL PROCEDURES IN FILLING TEETH. Or two cylinders may be used that have breadth enough to fill the space from buccal to lingual. Do not condense the non- cohesive gold before beginning with the cohesive. Merely adjust it in position with gentle pressure, and then condense it by building cohesive gold upon it. Then proceed as in all cohesive gold work, except that after the filling is otherwise finished the gingival portion should be very thoroughly con- densed from the surface. The reason that non-cohesive gold is safer in this position is that there is less disposition to curl from the margin, and if there is any disposition to curl from the margin it is easy to make it tight by this after-condensation, because if not tight it moves readily under the blows of the mallet, while cohesive gold does not. Generally a considerable quantity of non-cohesive gold may be used in this way and greatly reduce the labor of making the filling. This plan of filling is especially adapted to proximate cavities in the bicuspids and molars. These fillings, as we prepare the cavities, are not anchored in the proximate portion of the cavity, but in the step cut in the occlusal portion of the tooth. The filling is supported against the force of mastication upon the broad, flat gingival wall as a seat, and when non-cohesive gold is laid upon this in the manner indicated and condensed by packing cohesive gold over it, it h^s all the supporting strength of the complete cohesive gold filling. This plan of using non-cohesive gold is not so well adapted to proximate cavities in the incisors and cuspids, for in these we have not the opportunity to make strong occlusal step anchor- ages, but must depend upon the gingival wall and its angles in part for the strength of the anchorage. To use non- cohesive gold upon the gingival wall would materially diminish the strength of this anchorage. The use of non-cohesive gold upon the gingival wall of proximate cavities in the incisors is not so much needed, for the reason that they are in much plainer view during the progress of building the filling. Strength of the Bite. In the consideration of the strength required in fillings, the strength of the bite, or the power with which the teeth may be closed upon food, is a matter of first importance. This is STRENGTH OF THE BITE. 117 to be considered with great care by every operator, both in general and in relation to each individual operation. The strength required in fillings is very much greater than was for- merly supposed. It has been but a few years since we began to know definitely of the strength of the bite or of the strength actually required of fillings. I believe the first paper that brought this prominently before the profession was one which I presented to the Illinois State Dental Society in May, 1893. Following that, two instruments were presented for measuring the strength of the bite at the meeting of the World's Dental Congress in Chicago, later in the year of 1893, and very con- siderable interest was at once manifested in this subject, which has led rapidly to considerable changes in the preparation of cavities and to a radically new study of the strength of filling materials. These instruments were presented, one by the late J. J. R. Patrick, of Belleville, Illinois, and one by Dr. George Dennis, of Chicago. The instrument we are now using is a modification of the instrument presented by Doctor Dennis. It was immediately found that the actual strength of the human bite was very much greater than had been supposed, and that the strength of fillings had been insufficient, and this was the cause of the rapid failure of many fillings, particularly proxi- mate fillings. In order that the instrument should well repre- sent the strength of the bite, the surface upon which the biting is done should be spread over the crowns of at least two molar teeth, but as it is the force of the bite is generally expended upon a single cusp of an upper tooth and a single cusp of a lower tooth, which does not give sufficient space to properly present the full power with which the jaws may be closed upon food. The strength of the teeth is found to be ample; one can not break a tooth with the power of the muscles of the jaw, unless the biting is done on steel or some other very hard sub- stance. In biting upon steel, or other substance equally hard, the area of tooth substance presented to the steel will be very small indeed, and by hard biting the enamel may be fractured. But when the substance bitten upon is soft, as a piece of hard rubber, the tooth will sink into it a little and spread the area of stress more upon the surface of the tooth. On hard rubber or the softer metals I have never known a person to check the enamel of a tooth in biting with all the power of the muscles. 118 THE TECHNICAL PROCEDURES IN FILLING TEETH. Therefore, the teeth are abundantly strong, unless we happen to catch them on a bit ot gravel or a large bit of sand, or some- thing of that kind that is extremely hard. Half a dozen stu- dents who tried the force of their bite on the Knatho-dyna- mometer* during one of my lectures last year, registered respectively, 155, 190, 250, 220, 225 and 150 pounds. This represents very fairly the usual amount, and the variations in the stress persons with fairly good teeth, and of ordinary habits in their use, can exert. A few will exert a greater stress, as much as 275 or 300 pounds. Many people who use their teeth deli- cately will stop at 100 pounds or less. Often persons have registered 100, 130, and, occasionally, 200 pounds and over on the central incisors. Generally per- sons biting upon the instrument stop because it hurts the peri- dental membranes; they do not register the full power of the muscles of the jaws. A few tell me they have exerted the full power of the muscles without pain, and in these cases I suppose the full power of the muscles is registered. In chewing food we use, as a rule, very much more stress than is actually required to crush the food. By trying the crushing strength required, with the phago-dynamometer f we may find the crushing power required for the various foods. Filberts that school children are in the habit of crushing with their teeth give a register of from 100 to 150 pounds, occa- sionally more. In chewing meats much difference in the required stress is shown, good beefsteak requires from forty to sixty pounds, tough beefsteak from sixty to eighty pounds, occa- sionally more. Mutton chops usually require from thirty to forty pounds, pork chops (loin) twenty to twenty-five pounds, broiled ham from forty to sixty pounds, etc. If any one in chewing a piece of beefsteak will notice it he will hear a crack- ling sound just at the time the fiber of the flesh is breaking up. We can notice that also in the phago-dynamometer, and just at the time that the fiber is breaking up we find that the meat crushes out from between the teeth and the teeth pass through it and come together. Most person in chewing meats of any kind crush their teeth through it at a dash. A person who * An instrument for measuring the force with which the jaws may be closed. t An instrument for measuring the crushing force necessary in chewing different articles of food. STRENGTH OF THE BITE. 119 chews feebly will not do this. A person who is chewing with artificial teeth generally can not. A person who can use 40 pounds pressure upon artificial teeth is doing very well, and such persons will often find their beefsteak very tough ; but a per- son who can crush down 200 pounds can eat any beefsteak. In the ordinary chewing of beef or flesh, great force is not required, we may say, and yet, if we catch upon a bone, or in game, upon a shot, we will get a terrible jolt upon the teeth, for we actu- ally use much more than the necessary force. That is as likely to come upon fillings as upon any other part of the tooth, and, of course, will give the strength of the filling a sore trial. In chewing meats the motion is directly up and down ; we do not use the lateral movement in chewing meats. In this we copy the motions of the carnivorous animals. The carnivorous animals have their jaws hinged so that they have but the up-and- down motion used in crushing. We crush our meats ; we do not grind them. In chewing bread, or any of the grains — the cereal foods — we do use the lateral motion ; we grind them ,- we can not crush them. The more we crush upon bread the more we pack it between the cusps of the teeth. A little lateral motion will cause it to go to pieces quite readily, but we can not crush even a comparatively soft bread crust with all the force that we can put upon it ; it will simply pack into the sulci be- tween the cusps of the teeth and remain there. This is shown very readily with the phago-dynamometer. If I put a piece of comparatively soft crust in the instrument and put on a pressure of 60, 80 or 100 pounds it is simply packed between the teeth and has not been cut through at all, A litde lateral stress will grind it. Patients used to come to me saying that they had broken the cusp off of a bicuspid, for instance, "just biting a piece of soft bread." Sometimes I thought it was a kind of a joke, and sometimes I felt that it was absolute dishonesty ; I did not know the facts until I began to try the artificial chewing of food. Then I found that there was a substantial reason for it, for in taking a piece of bread crust between the teeth, without having it wet, we may crush with all the force of the muscles and simply pack it between the cusps of the teeth and bring to bear a powerful splitting force, calculated to throw off a cusp from a tooth. In this way we lose the cusps of a good many teeth, and teeth are broken from plates, crowns are broken, bridges 120 THE TECHNICAL PROCEDURES IN FILLING TEETH. are broken, ' ' just in biting a piece of soft bread crust. ' ' In these several ways very powerful stress is brought upon fillings, and cavities must be cut with the view of giving great strength to the fillings and of maintaining the strength of the teeth. It is for this reason that cavities are prepared in certain ways. In occlusal cavities, as they are formed by decay, the pulpal wall will usually be rounded — will be circular. This would be the form of the cavity after the removal of the decay. Now, this gives an opportunity for the rolling of fillings ; the filling is not as easily placed ; it is more difficult to make a good filling in such a cavity and the filling is more easily moved by the force of mas- tication. It might stand for a considerable time in chewing beefsteak, if it had no bones in it, no bits of gravel, or in chew- ing game, if there were no shot that would come upon a partic- ular portion of a filling and cause it to roll. But if the seat is cut flat, then the filling is supported in such a way that it is not disposed to roll. Again, a still more important point — when in a mesio-occluso-distal cavity in a molar or a bicuspid, with the pulp removed so that the tooth is open through from mesial to distal, the breadth of the pulp chamber is considerable ; and perhaps there has also been decay that has further weakened the dentinal walls. If the filling is finished in the normal form of the occlusal surface, leaving the inclines of the cusps toward the central area of the tooth standing, the food catches between these inclines of the cusps upon the buccal and upon the lingual. In this case the patient crushes down upon a bread crust ; it packs between these inclines of the cusps and great force is brought upon them, and the lingual wall or the buccal wall is broken away, "just biting a piece of bread crust." For this reason it is necessary to take great care in the preparation of all such cavities. Never leave the central incline of a cusp under such conditions. No matter how good it may be, no matter how perfect the enamel may be, no matter if it is supported by dentin immediately beneath, never leave it. It may be strong toward the occlusal, but more toward the gingival it is weak, and it is that weak portion that we need to protect. In all of those cases cut to the crest of the cusp, at least so that when food is packed between the cusps the stress will come entirely upon the filling ; let the filling material take this strain instead of the cusp of the tooth. This will also remove the possibility of STRENGTH OF THE BITE. 121 catching a shot or a piece of bone upon the cusp of the tooth and throwing it off. It is that which is caught upon the slope toward the central portion of the tooth that crushes it off, not that which is caught upon the slope toward the axial surface of the tooth. This is more essential in the bicuspids than it is in the molars, because they are less strong. In an ordinary mesio- disto-occlusal cavity, where the pulp is still retained, the inclines of the cusps may be left with perfect safety. All the strength of the muscles will not break it. But when the length of the walls is increased by extending the cavity to the floor of the pulp- chamber the case is entirely different. The bicuspids have sharper inclines than the molars, and food wedged into their sulci has a greater splitting force, and in these, with a mesio-occluso- distal cavity, and the pulp removed, it is necessary to protect the cusps in every way possible. In building out central incisors that have lost an angle there is only about half the stress to contend with as upon the molars ; and yet, in some instances there is as much as 200 pounds brought upon them. It is not uncommon for persons to take a bread crust between the teeth and put stress upon it, perhaps the full strength of the muscles of the jaws, and then tear it off with the hand, putting an additional force upon it. Now, that we have to build against, in building up these angles. We must pre- pare for this in the anchorage of the fillings and depend upon the strength of the gold when they are built. In this case it is nec- essary that we have the welding property of the gold perfect in every part ; any carelessness in the annealing of the gold will tell in the breakage of fillings in incisal angles. A little portion imperfecdy annealed will make a fault ; a little imperfection in the malleting will make a fault, either of which will extend over a portion of the area and cause a break. In the preparation of gold for such building we should generally resort to annealing upon a tray, allowing the gold to remain hot for a considerable time in order that every particle may be well annealed. And then pack the gold with a plugger point with a small condensing area, and go over every part of it with great care and use enough force. The force required in making fillings, and the strength required of fillings, will depend largely upon the strength of the peridental membranes. If the peridental membranes are not 122 THE TECHNICAL PROCEDURES IN FILLING TEETH. Strong the patient will not use the teeth very vigorously, and fillings of less strength will answer. But be careful not to under- estimate that. If the pulp has been removed from a tooth and it is still somewhat sore it may be very difficult to use sufficient force, and one may be deceived ; for when it is well the patient may put great force upon it. One should study each individual case as to the strength of the peridental membranes, the probable habits of the patient in chewing food, and build the filling accord- ingly. A person whose peridental membranes are strong, who, from the appearance of the teeth, you would suppose used much force in masticating food, particularly in cases where teeth are worn, you may expect that great force is used in the mastication of food, and you must build fillings accordingly, and see that every portion of gold is well annealed and malleted well home. A careful study of persons in regard to the force they use in biting seems to me almost essential in the practice of dentistry. I know it is difficult to do that without being equipped with the proper instruments for this study. I wish every one could be equipped with the instruments for taking the bite of patients. Many patients will become interested in it and it would afford a fund of information that would be of great benefit. Finishing Fillings. Except in proximate cavities in the presence of a pro:ximat- ing tooth, trimming fillings to form and finishing presents very little difficulty, and requires no special preparation for the finish- ing before the filling is introduced. In these it is necessary to the proper finishing that the teeth be separated, either before the filling is begun, or at some time during the building of it, to allow room for finishing the surface to the correct form. This separating has been described. Before any finishing is begun, the cavity must be filled more than full at every part to allow for sufficient trimming to remove all instrument marks, leaving a surface condensed to an even, perfect hardness. In occlusal, buccal, labial and lingual cavities, the first trimming may be done with the engine, using fine-cut finishing burs, or corundum stones, as may be most convenient, or in some positions the trimming may be done with the finishing files. Rotary instruments used in the dental engine should be FINISHING FILLINGS. 123 passed over the surface of the gold in some regular order, being careful not to cut too deeply in some parts, or cutting down irregularly. In occlusal cavities, when the bulk of the trim- ming has been done in this way, overlaps will remain in the grooves and irregularities of the surface. These are best re- moved with the discoid excavator, or spoons 20-9-12. These instruments should be very sharp. In buccal and labial cavities the finishing of the gin- gival margin is the difficult point. Generally no attempt should be made to cut these fully down to the enamel margin with the bur or stone, but after the first part of the cutting has been done, the gingival margin should be trimmed with the files or with the finishing knives. In some positions this will be done easiest with the knives ; in others it will be done easiest with the files. Generally the knives should do the last part of the trimming, for the reason that the sharp edge (and it must be very sharp to be of use) will catch under the least over- lap, find the exact enamel margin, and cut to it with certainty. In using the finishing knives no effort should be made to cut away a thick mass at a single stroke, but rather so catch it as to remove thin shavings and pare down the gold litde by little. Used in this way they will, in positions suited to their use, cut faster than any other instrument used for this purpose. Great care should be taken not to overtrim the gingival margin, cutting away part of the thin enamel, or all of it, leaving a depression. This is very liable to be done by the careless use of the stone, and forms a depression in which debris will lodge, setting up fermentation which will insure the recurrence of decay at that point. This error is a very common one. All parts of the margin of the filling should be trimmed exacdy to the cavity margins. This should be so perfect that a sharp edge or a sharp point will slide from the enamel onto the filling, or from the filling onto the enamel, without the least catch or interference with the perfectly smooth movement. All parts of the surface of the filling should harmonize with the surface of the tooth ; or, in other words, should reproduce the tooth form with accuracy. Then the whole surface should be evenly polished. This is best done by using a rubber disk of triangular form with a sharp outer edge armed with pulverized pumice, rotating rapidly in the engine. Or, on axial surface fillings, the 124 THE TECHNICAL PROCEDURES IN FILLING TEETH. sandpaper disk may often be used to advantage. When all instrument marks have been removed with this it may be fol- lowed by a leather disk and pumice, which at the last is carefully run dry. This will give a brilliant surface. In using the engine great care must be taken not to develop too much heat, as this is likely to cause severe pain, and may do perma- nent injury to the pulp of the tooth by setting up hyperaemia. A hard steel burnisher should not be used on cohesive gold fillings, for, if used with force enough to be of value, there is danger of checking the enamel margins, and for the reason that there is no necessity for its use if the surface of the filling has been well condensed. Finishing proximate fillings. — The teeth having been separated to give room, and the filling built out sufficiently to allow of its being finished to the original mesio-distal breadth of the tooth, the gold will have been packed very solidly against the proximating tooth. The first thing is to cut through between this tooth and the filling with a Koeber saw, held in the Wilson or Sibley frame. This cut should be close against the proximating tooth, removing as little gold as possible. Now, take a thread saw (made by grinding from the back of a Koeber saw on an ordinary corundum wheel until its width is reduced one-half), place it in the frame with the teeth toward the back, and pass this between the filling and the proximating tooth and work it under the gingival margin of the filling against the neck of the filled tooth and sawing toward the occlusal, cut away the overlap of gold. Afterward the saw may be turned first one way and then the other, and cut away the overlap well around to the buccal and to the lingual in case of very broad fillings. Then the saws have done their full duty. In cutting away the surplus with the saw especial care should be had not to cut too much toward the occlusal, and thus cut away the contact point. Now with the finishing knives begin at the gingival, and cutting fine shavings (the krtives must be sharp), remove any remaining overlap first and shave the proximate surface and the gingival portion of the embrasures to the required form. When the hand has become trained to the use of these knives, and they are kept sharp, this part of the work is quickly done and well done. The buccal and lingual embrasures are then to be FINISHING FILLINGS. 125 trimmed to form, and the contact which has been left flat with the saw must be rounded. This part of the work is best done with the file-cut finishing files. The blades of these files must be sharp to do this work well. When they have become dulled they are easily sharpened with slips of Arkansas stone, made for this purpose. Each blade is to be carefully ground sharp by drawing the stone back and forth against it. Generally, oil should be used on the stone. When the edge of the stone has become dulled or gaped it may be sharpened by whetting on fine emery paper laid flat on a table. Generally these files may be used with the thumb and palm grasp, and the flat sides applied to the gold, and with short, strong strokes almost parallel with the long axis of the tooth, the excess of gold is quickly removed. As the margins of the blades of these files are thin and sharp, they can pass well into the embrasure toward the contact point, rounding the surface just up to that point without cutting over it. This is done first on the buccal and then upon the lingual, and the contact point sharply rounded, and the embrasures, lingual and buccal, rounded to the proper form. Obtaining this marble-like roundness of the contact points is the critical requirement in finishing proximate fillings. If the surface is cut flat, the contact will grasp and hold food between the teeth and cause annoyance and pain, and cause injury to the gum septum by forcing the confined food against it. Neglect of this precaution has caused the loss of thousands of otherwise good fillings, and the teeth themselves, either by causing a recurrence of decay or by inducing disease of the peridental membrane. The occlusal surface, if the case be a molar or bicuspid, is to be trimmed and finished as described for occlusal fillings, after which corrections are made in the occlusal third of the proximate surface, and the whole filling polished. Polishing of proximate surface fillings should be done partly with tape and partly with disks in the engine. Tapes should be used for polishing the gingival two-thirds of the sur- face, or all of that portion of the filling to the gingival of the contact point, having especial care not to cut away the contact point. Narrow strips should be used. The embrasures, buccal and lingual, should be polished with disks, usually not more 126 THE TECHNICAL PROCEDURES IN FILLING TEETH. than five-eighths of an inch in diameter, in the engine. The disks should never be allowed to pass the point of con- tact, as they would quickly ruin the filling by cutting away the contact point, but should be confined to the embrasures and the buccal and lingual margins. When this has been completed satisfactorily, a very fine tape may be passed a few times over the contact point, rounding it and completing the polish. The importance of the form of fillings will be consid- ered more fully when the causes of caries and the conditions of its occurrence have been presented. Filling with Amalgam. I will preface the consideration of the manipulative proced- ures in filling with amalgam by saying that every detail of the cavity preparation should be the same as for filling with gold, except that convenience points for starting the filling need not be made. Neither is it quite so explicitly required that conven- ience forms of the walls for access be so rigidly observed, though there should not be much difference. If possible, the anchorage should be stronger than for gold, and as amalgam is so much used for very badly decayed teeth, especially in bicuspids and molars from which the pulps have been removed, advantage should be taken of the pulp chamber to strengthen the anchor- age. The pulp chamber should be filled solidly with amalgam to the pulpal orifice of the root canals when using it in pulpless teeth. With the amalgam we are using nowadays the teeth will not be discolored if the filling is properly made. The amalgam exposed upon the surface will discolor up to the margins, but the amalgam that is in contact with the walls of the cavity will not discolor, and consequently will not discolor the tooth. It is only when the amalgam filHng leaks about the margins that the tooth is discolored by it, and as we can now use amalgams that do not shrink, discolorations of the teeth will occur only through imperfect manipulation. The fact that amalgams used in the past and until very recently would shrink, causing leakage, is the reason why teeth filled with it have been so generally discolored. It is not easy, however, to make mechanically perfect amalgam fillings, and for one to succeed uniformly requires skill and the utmost care in every detail. FILLING WITH AMALGAM. 127 Amalgam is admissible only in the bicuspids and molars. All cavities filled ■with amalgam must have continu- ous surrounding walls during the building of the filling. We can not build up a corner of a tooth with amalgam and expect good adaptation to the walls, for the material is plastic, and, when pressed upon, the whole body of the filling is liable to movement. To prevent this, complete surrounding walls are a necessity. Therefore, whenever a cavity presents that has not four surrounding w^alls, the missing w^alls must iDe supplied by artificial walls. This is done by the applica- tion of the matrix. It is to be used in filling all proximate cavi- ties, and in any others in which one wall is broken down. Placing the matrix. — When a proximate cavity is other- wise ready for filling with amalgam, a slip of thin metal plate (copper, brass, German silver or steel) is cut of sufficient width to extend from the occlusal surface of the tooth to near the gin- gival line, or far enough to fully cover the gingival margin of the cavity, and long enough to encircle about half the tooth. The rubber dam having been applied before the excavation of the cavity was completed, this slip is passed between the teeth and roughly fitted to see that the width and length are right. Then at the corners to the gingival a little ear is turned with the pliers that will prevent a ligature from slipping off to the gingival, when it is drawn tightly around the tooth. Also the cut ends of the metal should be so bent that the sharp angles will not cut the ligature. This is now passed between the teeth so as to cover the proximate portion of the cavity. Then a ligature is thrown two or three times around the tooth, including the matrix, tightly drawn and tied. This is often a difficult operation for the beginner, but after a little experience the manipulation comes easy enough in most cases. A few cases occur where the conditions arc unfavorable and try one's wits, but these can be successfully done by a little effort. When this has been done the Perry separator is applied over the matrix, or in many cases the matrix may be held with the separator without the ligature. It is just as important to separate the teeth for amalgam fillings as for gold fillings, and on no account should this be neglected in cases requiring it. After the preparation is other- -wise complete, a careful examination of the gingival margin of 128 THE TECHNICAL PROCEDURES IN FILLING TEETH. the cavity should be made to see that the matrix is close at that point, and if it is not, it should be brought close, by inserting a small, soft wood wedge from the lingual side with just suffi- cient force to bring the matrix close. This is most likely to be needed in molars that have broad, flat, proximate surfaces. Preparing the Amalgam. It is of great importance to obtain in the beginning the right proportions of alloy and mercury. This proportion will vary with the alloy used. Of the higher grades of alloy we are at present using, this proportion is very nearly equal parts by weight, but generally a slightly greater proportion of mercury is required ; or about 52 per cent. This proportion should be carefully determined for the alloy used, and the proportions weighed for each mix. We think this of such importance in our infirmary work that we have this weighing done, and the prop- portions put in separate capsules. I have also found that to undertake to knead the alloy with too much mercury results in very imperfect kneading and makes a weak amalgam, while to knead with too little mercury also makes a very weak amalgam, and a mass that is too granular and stiff to work well. Kneading. The first of the kneading is done best in a wedgewood or ground-glass mortar. This should be continued until all of the fillings are incorporated with the mercury, when it should be turned into the palm of the hand and vigorously kneaded with the fingers. For this work the hand should be as dry as possi- ble. This kneading should be continued until the mass is per- fectly soft, plastic and free from granulation. If in the kneading the mass becomes too very soft there is too much mercury in the mix, and so soon as that is determined a portion of the mercury should be removed by squeezing the mass between the fingers and the kneading immediately continued, for if -the mass is allowed to stand for even a few moments in this condition it is likely to become too stiff for rekneading. When sufficiently kneaded, the mass should not very readily break when rolled into a long roll in the palm of the hand. Everything should be in exact readiness to insert the filling and the packing immediately FILLING WITH AMALGAM. 129 proceeded with, for if the alloy is just what it should be, the mass will begin to stiffen very quickly, and possibly become unfit to work before the packing is completed. Packing Amalgam Filling. The importance of the best form of instrument for packing amalgam can hardly be overestimated. Until I had examined this over and over again, experimentally, under conditions which enabled me to determine results, I had no idea of the importance of the instrument forms for this purpose. The one thing need- ful in packing amalgam is to grasp the mass as a whole as nearly as possible, and compress it into the cavity. The whole prin- ciple of making perfect work is contained in the one word, compression. Therefore, the cavity must be a simple one with complete surrounding walls, or must be converted into a simple cavity by supplying any missing walls with the matrix. Then the instrument point should be flat and as large as the cavity will conveniently admit, and, when practicable, its form should be such as to as nearly fit the cavity as possible. With it and the walls of the cavity the mass of amalgam should be grasped as perfectly as possible and powerfully compressed, so as to force the amalgam into all parts of the cavity. About all the force the hand is capable of should be brought upon it and maintained for an instant. Then more of the mass is added and again pressure applied. This should be done as rapidly as perfect work will admit, until the cavity is full and much more than full. Indeed, more of the mass should be added and compressed as long as compression of the mass in the cavity can be made by adding to the surface, for the time comes when the m.ass added simply spreads out over the cavity walls. If, during the packing, there are narrow parts of the cavity or irregularity of walls into which the instruments do not go well, a smaller instrument should be used to pack the amalgam into them. These should not be used with such force as to crush into the mass and chop it up, but only with such force as will compress. When the cavity is full it should be allowed to rest undisturbed for a few minutes to give it time to stiffen a little before attempting to remove any of the surplus. 130 THE TECHNICAL PROCEDURES IN FILLING TEETH. Instruments. In the lists of instruments there are three round points of different sizes from small to large for the more ordinary work, and then there are two pairs arranged with special reference to filling occluso-proximate cavities. One of each of these pairs will fit fairly well into the proximate portion of these cavities, and the other into the step. They grasp and compress the mass well in either of these positions. All of them are serrated to prevent slipping and sliding. These instruments should be used in all amalgam work. Heretofore many dentists have used burnishers to pack amal- gam fillings, thinking they could burnish and amalgam to the walls of the cavity. This is a popular error. I once supposed I could do this, and could prove it by burnishing amalgam onto a tooth-brush handle, causing it to stick so firmly that I could build a great mass upon it and the whole would cling very tightly. But on prying this off and examining the surface that stuck so well with the microscope, I found it full of fine bubbles. In trying some of these in an aniline dye I found that these bub- bles became filled with the colored fluid. In trying this in cav- ities in teeth and breaking the tooth after the amalgam was hard, I found the same thing occurred. Finally, I became convinced that the endeavor to make a perfect amalgam filling with a bur- nisher was a failure. The thing simply can not be done. The amalgam will flake up from the wall and the adaptation be imperfect. Finishing Amalgam Fillings. When the amalgam filling has stood a few moments to stiffen in some degree, the surface should be trimmed to form with a discoid or spoon excavator, if on an occlusal surface, and care- fully burnished toward the walls, using a light pressure that will not be liable to move the mass as a whole. If upon an axial surface, as the buccal, it may very conveniently be trimmed with the finishing knives and all overlaps removed, and then carefully but lightly burnished. If an occluso-proximate filling, trim the occlusal portion before removing the separator, as this work will give a little more time for the mass to harden to prevent the fill- ing being crushed by the teeth dropping together. When the separator is removed the matrix will be THE CEMENTS. 131 firmly held between the filling and the proximating tooth. Any attempt to pull this out is liable to injure the filling. In this case straighten out the ends of the matrix to the lingual and to the buccal and reapply the separator with the matrix between the claw^s. Then tighten the sepa- rator sufficiently to loosen the matrix and remove it. Now, while the separator is in place, with the finishing knives trim the proximate surface to form and remove all overlaps about the margins. Then burnish lightly, remove the separator and the rubber dam. Be careful to note the occlusion, and if a cusp of an opposing tooth strikes the filling, trim it down so that there may be no danger of injury to the fill- ing from that cause. Trimming to form as described is very important, because it can be done at this time while the amalgam is still but partially hardened, with ease, and very quickly. If we wait until the amalgam is fully hard it is a tedious, difficult operation. The patient may now be dismissed for one, two or three days, as may be mutually convenient, or until the amalgam is fully hard. Then the whole filling must be polished. This polishing is practically the same, is done with the same instruments as a gold filling, and must be done with the same care. In proximate fillings it is very often necessary to re- apply the separator to properly finish the proximate surface and the contact point. The Cements. The cements at present available for use in filling operations are the oxy-chloride of zinc and the oxy-phosphate of zinc. The composition of these you have already learned in the chemical laboratory. Formerly the oxy-chloride of zinc cement was much used, but since the introduction of the oxy-phosphate it has fallen into disuse on account of the very irritating qualities of its fluid portion. The phosphate of zinc cement is very much less irrita- ting and is generally preferred for this reason. The cements are received from the dealer in two separate bottles, the one contain- ing the powdered oxide of zinc and the other the fluid. In use a small portion of the powder is placed upon a porcelain or glass slab, and a drop or two of fluid is placed beside it. The two are then drawn together and thoroughly mixed by rubbing them 132 THE TECHNICAL PROCEDURES IN FILLING TEETH. together with a spatula. This spatulation should be continued until a very smooth, creamy mass has been formed. The mix- ture of the oxy-phosphate should be much thicker and stififer than the mixture of the oxy-chloride to obtain the best results with the respective cements. Indeed, the oxy-chloride may be mixed so thin and soft as almost to flow and yet become very hard and firm; while the oxy-phosphate, to produce the best mass, should be rather stiff, yet it may be quite plastic. As yet, there has been very little careful examination of the physical properties of these cements. We do not know accu- rately the proportions of powder and fluid required to produce the best results. It is probable that these vary with the different makes of these cements, and also with the age, for the fluids seem to be inconstant in their properties. It has been the con- stant habit of dentists to mix them without any rule, simply observing the plasticity of the mass produced, being governed entirely by the eye and the observation of the results. This must be regarded as a very inaccurate method of using this material, but so long as we are without more accurate knowledge of it than this gives, we can only follow it. Very recently some work has been done on the physical properties of the cements by Doctor Wedelstaedt, of St. Paul, and by Doctor Ames, of Chi- cago. In this work it has been shown that most of the cements are readily permeated by moisture, while some are not, and also that some of the cements will shrink badly while hardening. In mixing the oxy-phosphate it seems to be best to draw the powder into the fluid and incorporate it little by little until the required stiffness of the mass has been acquired. Just what this should be can not, in the absence of carefully conducted experi- ments, be definitely stated. In practice it is varied with the particular use to be made of the particular mix. If for filling and setting crowns, in which case great plasticity is required, the consistency of very thick cream is usually acquired, and this very thoroughly spatulated and used quickly, or before it has begun to stiffen. If for filling cavities in teeth, more of the powder is added and the mix made stiffer, and the spatulation continued somewhat longer, so that the mass assumes a putty- like consistence. It seems to be the general notion that when mixed in this way a much stronger mass is formed. This idea is strongly supported by some recent physical experiments, yet THE CEMENTS. 133 these have not been in sufficient number, nor have they been sufficiently varied as to conditions to give certain working data. These cements are not impervious to moisture. Some experiments have recently been made as to the qualities of the cements with regard to exclusion of moisture, and it has been found that none of them are actually impermeable, while many of those on the market admit moisture readily. As yet, we do not know with any degree of certainty upon what these differences depend. They are, however, very important. Other things being equal, the cement that is nearest moisture-tight is the best for use. Any one may try cements by making experi- mental fillings and placing them for a day, or two or three, in a solution of aniline dye, and then breaking them open and observing the penetration of the color into the mass of the material. Some of the cements will be penetrated through and through in a very short time, while others will resist for a longer time. It appears from experiments already made that those cements which are not permeable by moisture shrink badly while setting. This shrinkage renders them a poorer material for use than some of those that are in a degree penetrable by moisture. When made into fillings in teeth the cements do not resist perfectly the solvent action of the oral secretions. Thisy are slowly dissolved, or waste away. They are, therefore, not very permanent fillings. In this regard great differences are observed. In a few cases cement fillings have done excellent service for many years, seemingly resisting the action of the oral secretions perfectly. In the majority of cases, however, they dissolve away within two or three years, and in many instances within a few months. We have not yet such a knowledge of the conditions of these variations as will enable us to control them, and must therefore regard cement fillings as temporary in their nature and qualities, expecting to renew them at frequent inter- vals. Use of the Cements. The cements are used for setting crowns and bridges, for temporary fillings, and for preserving for a time teeth that are very badly broken down, or in other conditicHis which seem to render the use of the metallic fillings undesirable at the time. 134 THE TECHNICAL PROCEDURES IN FILLING TEETH. They may also be used for temporary fillings in cases of very sensitive dentin for the purpose of allaying the extreme sensitive- ness, which is generally found to disappear, in large part at least, within a few weeks or months. They may also be used for temporary fillings in cases of hyperaemia of the dental pulp with marked advantage, for the reason that their conductivity of thermal impressions is less than that of the metals, though in this respect gutta-percha is much better than the cements ; also they may be used in capping exposed pulps. The cements are also much used for sealing treatments in pulp-chambers and root-canals. This last use of the cements is not good practice. They do not perfectly exclude moisture. Gutta-percha is much better for this purpose for the reasons, first, that gutta-percha is impermeable to fluids, and moisture-tight fillings can be made with it; second, gutta-percha is much more easily removed from the cavity in opening it for changes of the applications. It is very painful to cut out a cement filling when the peridental membrane of the tooth is sore, while gutta-percha may be softened by heat and removed with very little pain. Filling with Cement. In filling cavities with cement the preparation should be well made, all of the walls being cleaned by perfectly removing all carious dentin to sound tooth structure, and the walls and mar- gins trimmed smooth. Some degree of retention should also be given to the cavity form, but this is not so imperative as with metal fillings. -The cavity should be perfectly dry at every part, for in this case we may expect that the cement will adhere strongly to the cavity walls and in part sustain the filling in position. The cement should be mixed with as much of the powder as will work into a plastic mass and spatulated vigorously until it has begun to stiffen, and, when at the consistence of putty, should be packed into the cavity in moderately small masses, using as much force as the consistence will allow, adding piece after piece, until all parts of the cavity are full and over-full. Then a few moments should be allowed for the cement to stiffen a little more, after which the filling is trimmed to form with the finishing knives. In this trimming the cement should be so stiff that the stickiness shall have disappeared, for it is only just at this time GUTTA-PERCHA. 135 that it can be cut smoothly without dragging. After trimming it may be burnished Hghdy, and if necessary smoothed with polishing strips. After the filling is completed it should be protected from moisture for some minutes, the longer the better, as the cement will become harder. It seems that when moisture is admitted early a part of the phosphoric acid is dissolved out of the cement, robbing it of a part that is necessary for the most complete hard- ening of the mass. These general principles should be observed in all uses of cements. Softer masses must be used in setting crowns and some other operations requiring a plasticity approaching a fluid condi- tion, but it should be remembered that this renders the cement less strong and more soluble, and is to be avoided whenever the conditions of the case in hand will allow. Gutta-percha. Gutta-percha is used for various purposes in connection with filling operations. The best form for this purpose is the ordinary base-plate gutta-percha. Besides this, however, a multitude of makes for the purpose of filling teeth are found in the market. None of these are superior to the ordinary base-plate, and the greater number of them are very inferior. Many of them seem to be mixtures of gutta-percha and wax that soften very readily by heat. These are especially to be avoided. Gutta-percha is the best material we have for root filling, for sealing dressings in root-canals, and for most of the temporary stoppings used in connection with treatment cases. Under certain conditions it is also an excellent material for more or less permanent fillings in cavities in the teeth. Filling with Qutta-percha. In filling cavities in teeth with gutta-percha the cavity should be prepared almost as for gold or amalgam, but generally con- venience points for starting may be dispensed with. The cavity should, however, be made as strongly retentive as possible. When otherwise ready for filling, every portion of the cavity walls should be moistened with eucalyptol or oil of cajuput. These oils take strongly to the cavity walls and also dissolve slightly the surface of the gutta-percha as it comes in contact with it. The 136 THE TECHNICAL PROCEDURES IN FILLING TEETH. oil then diffuses through the mass of the gutta-percha and is lost, apparently, leaving the gutta-percha adhering firmly to the cavity walls. Therefore, for this purpose the cavity -walls should only be moistened. No excess of the oil should be allowed to remain in the cavity, as the effect will be to soften the whole mass of the filling. Prepare the gutta-percha by gently warming it over the flame of the alcohol lamp, or upon a warm tray. Care should be had not to heat the gutta-percha too hot. This will develop an inordinate stickiness of the mass, and it will not again become fully hard; the quality of the material is per^ manently injured. When it is made just plastic by heat, convey it to the cavity in small pieces and build the filling up from the most convenient angle or wall of the cavity piece by piece, sticking the warm pieces to the mass in the cavity with a considerable pressure, and condensing well against all walls and margins. In this work it is well, if possible, to add no more of the material than will just fill the cavity, having none to remove in trimming. If, however, a surplus has been added, warm a small flat burnisher sufficiently to quickly soften the gutta-percha upon contact, and with this cut away the surplus, and immediately condense and adjust the surface of the filling with a cold burnisher that has been laid ready. The finish should generally be made entirely with the burnisher, as we can not polish the surface of the filling by any of the usual means. By waiting until the filling is fully hard it may be trimmed with a sharp knife, but the edge must be very sharp to cut smoothly. This is the best instrument for remov- ing overlaps and making a good finish of margins. Another plan of filling with gutta-percha that is useful in many cases, especially cavities of easy access, is to form a mass that will just fill the cavity and warm it only sufficiently to obtain the necessary plasticity, (and insert the whole filling in one piece, condensing with a broad, cold instrument, afterward finish as before described. Much experience is required to handle gutta-percha well, but when once the manipulation has been learned it is not difficult, and requires but little time. It should be the only material used for sealing in dressings, and for the temporary stoppings in connection with treatments. EXPOSURE AND REMOVAL OF THE DENTAL PULP. 137 Gutta-percha is too soft for permanent fillings in any positions that are exposed to the stress or friction of mastication. In some cavities, where it will not be exposed to wear, it will do most excellent service. It is especially to be recommended for fillino- cavities in the buccal surfaces of the teeth of old people, especially those that are in large part in the cementum, and extend beneath the free margin of the gum. It is often useful as fillings in the temporary teeth for chil- dren. By renewing it from time to time these teeth may be made useful until removed in the shedding process. However, children often wear it out of cavities rapidly, and it needs to be very frequently renewed. Gutta-percha is also very useful in the treatment of sensitive dentin, and in cavities of teeth with hyperaemia of the pulp. It is tolerated in both of these conditions better than any other filling material, and, if well put in, will generally stand long enough to accomplish good results. But to do well in either of these classes of cases, it must be made to cohere to the walls of the cavity. Otherwise it is liable on account of its softness to slight movement in the ca\ity, and to admit moisture. In that case the condition, especially of sensitive dentin, is liable to be made worse instead of better. Exposure and Removal of the Dental Pulp. Exposure of the dental pulp. — The pulp of a tooth may be found exposed by caries so that it lies naked and in view ; it may have been reached by the extension of caries but remain covered by a softened carious mass of dentin ; it may become exposed by accident during the preparation of a carious cavity ; the conditions may require that an intentional exposure be made through a carious cavity that has nearly reached the pulp, or that an intentional exposure be made, there being no carious cavity. The first and second cases are so similar that they may be treated of together, only noticing differences of manipulation as they occur. In both, the supposition is that the pulp is to be destroyed and removed. In the first procedure the problem is the preparation of the cavity for the treatment of the exposed pul[>, and with the least pain and inconvenience to the patient. The requirement is that the cavity be opened by the removal 138 THE TECHNICAL PROCEDURES IN FILLING TEETH. of all overhanging enamel and that the surrounding walls be freed from carious material, perfectly cleaned to solid dentin, and cut to a form that will certainly retain a temporary filling for the purpose of sealing in applications that may be required in the treatment of the pulp. It is not required here that the cavity be cut to the full outline form, as it will be prepared to receive the permanent filling later ; nor that permanent anchor- ages be provided ; but it is required that good and sufficient anchorage be provided for a temporary gutta-percha filling against good clean surrounding walls in every part. It should be opened sufficiently wide to admit of the free and easy appli- cation of instruments for the exposure of the pulp. In doing this especial care should be taken that the instruments used be not directed toward the pulp of the tooth and that it be not interfered with in any way until after the surrounding walls are clean and solid in every direction. This excavation is to be done upon the principles already laid down for the excavation of cavities in the class to which the case in hand belongs. If the rubber dam has not been placed at the beginning, it should be placed now and every preparation made for the best possible view of the deeper parts of the cavity. The next step is the removal of the carious material from the deeper parts of the cavity — the axial or pulpal wall — and from about the expo- sure. In case the exposure is large and the pulp is already laid bare, this need not be very perfectly done at first, the ne- cessity being that applications can be laid directly upon the pulp tissue and perfectly sealed in place by a temporary filling. In case the pulp is covered with carious material only this should be removed and the tissue of the pulp laid bare. In every position this should be done with the broadest cutting instrument that is applicable to the position, usually with the spoons. One should never undertake to remove softened mate- rial from over a pulp with an instrument so small that it is liable to penetrate through the opening into the pulp chamber, lacerate the pulp tissue, and inflict unnecessary pain. This should be taken as a principle controlling every procedure in this class of cases, and the operator should see to it particularly that the cav- ity be so opened and prepared that broad points may be used with facility. When these preparations have been made, if the case be other than a proximate cavity in the incisors, take the spoon EXPOSURE AND REMOVAL OF THE DENTAL PULP. 139 20-9-12, and having determined the best direction in which to make a sweeping cut, start its edge carefully under the carious mass close against one of the walls of the cavity and, with a strong thrust in a curved direction, carry it across the other side, cut- ting at once to the full depth of the softened dentin, and if pos- sible remove the whole mass at the single cut, laying the pulp bare. This should be carefully planned and firmly exe- cuted. If the cut should be through the superficial portions of the pulp, excising a portion of the tissue, it is just as well, for when the hemorrhage has ceased we are sure of the best condi- tion for the absorption of remedies for destroying it, whether this be done by the application of the arsenic or by the use of cocaine under pressure. In some broad cavities in which it may seem that the carious mass is too broad to be removed at a single cut, one or more preparatory cuts may be made to either side, avoiding the pulp, before making the principal cut for its exposure. An exposure of the pulp made in this way is usually not very painful, and even if it be very sensitive, the duration of the pain is reduced to the shortest limit. In proximate cavities in the incisors the spoons 20-9-12 can not generally be used for want of room. Much oftener the spoons 15-8-12 or the discoid are applicable. In these cavities the most desirable direction for the final cut for exposing the pulp is from the gingival toward the incisal directly over the pulp. In these cases the opening into the pulp is apt to be long inciso-gingivally, and if the broad cutting edge can be placed at right angles to this it is much safer against dropping into the pulp chamber and producing unnecessary laceration of the sen- sitive tissues. By proceeding carefully this position or an angle closely proximating it can often be obtained, and then the exposure is made with safety ; a discoid 15 is really the best instrument for the purpose in this position. By working with care the exposure maybe made with hatchet 12-5-12, cutting from labial to lingual, but with much more danger of inflicting severe pain. Destroying the dental pulp,— When the pulp has been fully exfjoscd, the cavity should be ready for the ap[)lication to the pulp without further [m.-paration. If it is to be destroyed by arsenic, cut a piece of ordinary writing paper of such size and 140 THE TECHNICAL PROCEDURES IN FILLING TEETH. form that it may be easily so laid in the cavity as to cover the exposure, and try it in place. Then the walls of the cavity should be moistened with eucalyptol or oil of cajuput, to pre- pare them for receiving a gutta-percha filling, and any excess of oil removed. Then place a small, but sufficient amount of arsenical paste upon this paper, and apply it directly to the exposure, and press it gently in place ; see to it carefully that there is not so much of the paste that it will run out around the margins of the paper, and be in danger of smearing the walls of the cavity, and possibly getting out toward the gingival margin of proximate cavities, for in this case there will be danger of arsenical poisoning of gum tissues. Place over this a gutta- percha filling, using especial care not to make unnecessary pressure over the exposure of the pulp that will cause compres- sion and pain. This gutta-percha filling should be as perfect in its adaptation to the cavity walls as it is possible to make it, in order that there may be no leakage of the arsenic outward to poison the surrounding tissues, or of moisture from without inward to interfere with the action of the drug. Another impor- tant care should be that in proximate cavities no overplus of gutta-percha be allowed to infringe upon the gum septum and cause absorption. Overplus in this direction is readily avoided by placing any suitable instrument between the teeth at the gin- gival, such as the shaft of hoe 8-3-6, and making the gutta- percha filling against that, and afterward removing the instru- ment. This gives room for the gum septum, and yet allows the temporary filling to be placed firmly against the proximating tooth. Finally, the filling must be so finished as not to give the patient annoyance, after which the patient may be discharged for forty-eight hours, or until the arsenic has acted. Anaesthetizing the dental pulp. — If it has been decided to anaesthetize the pulp with cocaine under pressure, the opening into the pulp must be free and large, and the position such that the after manipulation can be readily done. The surrounding walls must be sufficient so that the drug may be readily confined under pressure, and the access fairly direct. Otherwise arsenic should be used. When the cavity has been fully prepared — an occusal cav- ity in an upper first molar for example — a sufficient amount of cocaine crystals should be dissolved in a few drops of water in a EXPOSURE AND REMOVAL OF THE DENTAL PULP. 141 capsule (always made fresh for each case), and a small pellet of cotton saturated with this solution is placed in the cavity upon the exposed pulp. Over this place a pellet of soft, or unvulcan- ized, vulcanite rubber that will completely fill the orifice of the cavity and prevent the escape of the solution. Upon this make pressure with a broad-faced amalgam plugger. The pressure should be gentle at first, and be gradually increased as the pain is relieved, watching for evidence of pain in the countenance of the patient, until very heavy pressure can be made. This should be maintained for several minutes. Then if all has gone well the rubber and the cotton may be removed, and the pulp will be found insensible and its removal may be proceeded with.* In anaesthetizing the pulp in this way notice particularly that the cavity must be so stopped with the soft rubber as to prevent the escape of the solution along the cavity walls, otherwise the pressure will fail to force the drug into the pulp tissue and the anaesthesia will fail. This is fairly easy of accomplishment in the cavity named above and those of similar form and situation. But in proximate cavities it is often much more difficult to so place the rubber that it will successfully stop the orifice of the cavity and prevent the escape of the fluid. In the molars and bicuspids this may be successfully done by first placing a properly formed piece of rubber against the proximating surface of the adjacent tooth and forcing it against the gingival wall of the cavity, and then doubling it over the occlusal portion so as to close that also, and then applying pressure with a broad instru- ment point selected to fit the cavity to the best advantage. As one becomes expert in this, most cavities may be so handled as to successfully produce anaesthesia of the pulp. Opening the pulp chamber preparatory to removal of the pulp. — When the pulp has been destroyed by arsenic, the procedure when the patient has returned for the next sitting is first to adjust the rubber dam. In proximate cavities in which the gutta-percha filling has been placed firmly against the proximating tooth, the filling must first be cut through with a Koeber saw, or trimmed away with a sharp finishing knife in order to allow the rubber dam to pass. When the dam is in position sterilize the field of operation by mopping the teeth included, their interproximate spaces and the adjacent rubber * Prof. A. H. Peck's Lectures, 1899. 142 THE TECHNICAL PROCEDURES IN FILLING TEETH, with 1-2-3, oil of cloves or oil of cassia, and then drying them off with absorbent cotton. Then the gutta-percha filling may- be softened by warming a burnisher and passing the hot point into it, and holding it for a moment to allow the general softening of the gutta-percha, when it may be lifted out. The cavity is now freed from the arsenic paste and washed out with the antiseptic and dried. It is now ready to proceed with the opening of the pulp chamber. In case the pulp has been anaesthetized with cocaine, the rubber dam will be in place and ready for the opening of the pulp chamber so that from this time the procedures in the two cases will be similar. In either case the pulp should first be pricked cautiously with a very fine broach, to be sure that it has lost its sensibility, for sometimes there is a failure in either way of operating. Having determined that the conditions are favorable for removal of the pulp, the first operation is the opening of the pulp chamber. In the bicuspids and molars this consists in the removal of the entire roof, or den- tinal covering, and the manner of doing this will depend much upon the extent and the location of the decay. In occlusal cavities in the molars in which the decay is large, often the hoe 6-2-23 can be slipped into the opening and the roof of the chamber pulled away, uncovering the entire pulp. But when the dentinal covering is strong, as is usually the case when the opening is only the exposure of one of the horns of the pulp, the better way is to enlarge the opening with a small fissure bur. This is passed into the pulp chamber through the orifice of the exposure, and when the operator is sufficiently sure in his knowledge of the anatomy, he may cut around the pulp chamber parallel with its axial walls and remove the covering in a single piece. Otherwise the opening may be enlarged by carrying the bur laterally toward the central portion of the covering of the chamber and then carrying it around in a circle. Then hoe 6-2-23 may be passed into the opening and its blade turned under the roof covering the pulp, the overhang determined, and the cutting directed, until the whole extent of the chamber is uncovered ; no overhang should be left at any point. In this cutting the greatest care should be taken that the bur be not pressed onto the floor of the chamber and its form marred by cut- ting into it. When the whole of the roof has been removed, it is generally best to enlarge somewhat toward the mesio-buccal EXPOSURE AND REMOVAL OF THE DENTAL PULP. 143 angle in order to better reach the mesio-buccal root canal. This may be done most readily and in the best form by a scraping movement with the cleoid. The case is now ready for the removal of the pulp. Incidentally much of the tissue of the bulb of the pulp, possibly all of it, will have been removed in doing this cutting, but no attempt should be made to remove the pulp from the canals until this cutting is satisfactorily com- pleted. In many cases after the first opening has been made the roof of the pulp chamber can be cut away quicker and much more satisfactorily with the chisel and mallet. If the exposure is from a mesial cavity the cutting will be, of course, to the distal and often will involve the removal of the middle third of the occlusal surface with the whole of the dentin intervening between it and the pulp. If a distal cavity, the middle third bucco-lingually of the occlusal surface with the intervening dentin should at once be removed to a point well toward the mesial marginal ridge. In the bicuspids the exposures are almost uniformly from cavities in the proximate surfaces, and the chambers are broad bucco-lingually. The cutting for the opening of the chambers must be directed first to the central part of the crown, but later broadened from buccal to lingual ; for the horns of the pulp, when long, in these teeth spread out toward the points of the cusps. These should be fully opened into so that they may be cleaned, also the root canals in these teeth, especially in upper first bicuspids, are given off from the extreme buccal and extreme lingual portions of the chamber, and unless this cutting is broad in this direction, the broach will not have direct entrance into them. In the incisors and cuspids exposures are generally from proximate cavities. In opening these for the removal of the pulp, the orifice of the exposure should be first extended to the gingival wall of the cavity, and. to the full breadth of the cham- ber. The approach should be carefully considered. Generally a broach will not readily slide into the canal without being bent more or less. This is unfavorable, and a better approach must be made. Generally when a cavity is so large that the pulp has been reached, the lingual wall should be cut away, and this will improve the approach, the instrument being passed to the lingual 144 THE TECHNICAL PROCEDURES IN FILLING TEETH. of the incisal edge of the tooth ; rarely the labial wall should be cut away. Then, to improve the approach still more, take a small fissure bur in the engine, and approaching the canal from the direction in which a broach would be introduced, pass it into the canal, and cut by lateral pressure broadening the canal in a direction to straighten the approach. This cutting will be toward the disto-lingual if a distal cavity, or mesio-lingual if a mesial cavity, if the approach is to the lingual of the incisal edge. From whatever the direction of the approach, the cutting is to be so directed that the broadening of the coronal portion of the canal will straighten it. In this cutting special care should be had that the end of the bur should not cut the oppo- site side of the canal and roughen it, for if it should, the point of an instrument will be catching in the rough points at every effort to introduce it into the canal. By this cutting the curve of the instruments introduced into the canal for the removal of the pulp, or for filling the canal, will be much less abrupt, and these operations can be done more perfectly. It is particularly desirable that all cutting in opening the pulp chamber be completed, and the cavity cleaned of chips or cut- tings before the pulp is removed from the root canals. Often these cuttings will fall into a small canal, and an instrument thrust will so fasten them' as to occlude the canal. If in any case it should become necessary to do more cutting after remov- ing the pulp from one root canal in order to gain access to another, a wisp of cotton to catch any chips should first be placed in the open canal. Removal of the Pulp. The instruments used for removing the pulp from the canals are the barbed broach and the smooth broach. Gen- erally the barbed broach should be used first. Usually the bulb of the pulp will have been removed during the opening of the pulp chamber, and the broach selected should be suited in size to the canal. Test the broach before using it by taking the point on the finger and bending it. See that it bends in a regular curve. Occasionally in cutting the barbs the shaft is cut too deeply at some point, which will cause it to break easily — such a broach should be discarded. The broach should be held EXPOSURE AND REMOVAL OF THE DENTAL PULP. 1-45 in a light handle, but may be used without. Just before introducing the broach dip it into a good antiseptic, pref- erably 1-2-3, or oil of cloves. This should never be neglected, for the broaches are liable to carry micro-organisms into the canal and infect it. Now pass the broach into the canal, direct- ing it against one of the walls, so that it will pass in beside the pulp tissue rather than through it. Generally the point should be pushed to the apical foramen and then, if it is felt to be held tightly in the apical end of the canal, withdraw it until it is felt to be loose. Now rotate the broach lightly, moving it slightly back and forth to be sure that the whole length is rotating and not being held in some curved part of the canal which would be liable to break the broach. The rotation should not exceed one turn, then withdraw it. In a good many cases the entire con- tents of the canal will be brought away with the first effort. If not, the movement is repeated. Often the tissue of the pulp will break up into shreds and be but partially removed. In this case the smooth broach with cotton should be used. For preparing this the fingers should be disinfected by taking a bit of cotton moistened with the disinfecting agent used, and rolling it between the fingers and thumb. Then take a small bit of absorbent cotton and pull it between the fingers of the two hands until a small shred is formed containing but a few parallel fibers. Take one end of this between the forefinger and thumb of the right hand and grasp with it the broach at midlength, or with the cotton wisp extending slightly past its point. With the left hand grasp the other end of the cotton wisp and the point of the broach together and rotate the broach in the fingers of the right hand until the cotton is wrapped firmly upon its shaft. When this is properly done the cotton will cling firmly to the broach, and is not likely to be lost in the canal. With the broach thus armed, dip it first in the antiseptic and then pass it into the canal, slightly rotating back and forth. When the full depth has been reached, turn the broach fully upon its axis and withdraw it while in rotation. Generally the shreds of the pulp will become entangled in the cotton and be brought away. This should be repeated until satisfied that all tissue has been removed from the canal to the apex. .Students often have difficulty in finding the canals in the molar teeth. .Specific directions for approaching them are given 10 146 THE TECHNICAL PROCEDURES IN FILLING TEETH. in the anatomy.* Difficulty of this kind should not occur except in abnormal cases, and when they do, it is generally because the floors of the pulp chambers have been mutilated with burs, and the openings of the canals filled with chips. This should never be done ; burs should not be used in the floor of the pulp chamber. No specific directions can be given for abnormal cases. When the pulp chamber is filled with secondary deposits, the effort should be directed to the removal of these, preserving the out- lines of the pulp chamber. When the pulp chamber is much narrowed by secondary dentin deposited upon its walls, the openings into the canals should be found before any cutting is done, and then the cutting carefully directed to straightening them. In most instances this is done best with the barbed broach. All small tortuous canals should be enlarged and straightened with the barbed broach. To do this, cause the broach to enter the canal as far as possible and withdraw it. The barbs will impinge upon the walls and cut away the dentin. Repeat this, pressing the broach in a direction that will tend to straighten the canal. By repetitions of the movement, the canal that can be entered by the smallest broach can soon be enlarged sufficiently for filling. Generally partial occlusions of canals are confined to or near their pulpal ends, and where this has been straightened up, the broach will pass to the apex. In elderly people certain canals are often too small for successful cleaning and filling. In cases in which there has been much wearing away of the teeth, the pulp chambers and the pulpal ends of the root canals are apt to be much narrowed by secondary dentin. This applies to all of the teeth in the mouth, i. e., to any that have, from any cause, not been worn away the same as those that are worn. When the root canals have been cleaned, it is generally neces- sary that a dressing be laid in the canals and the cavity sealed with a gutta-percha filling until a future time. For this purpose a wisp of cotton should be formed with its fibers mostly parallel, and the end of this caught with the point of the broach with the thumb and finger of the left hand and the broach rotated with the right hand, while the fingers of the left roll the cotton on its * Black's Dental Anatomy. For upper molars, paragraphs 173 to 178 inclusive; for lower molars, paragraphs 180 to 185 inclusive, to which the reader is referred. EXPOSURE AND REMOVAL OF THE DENTAL PULP. 147 end. In this way the cotton is rolled on the broach in such a way that it will not slip backward on the broach and can be car- ried to the apical end of the canal ; and when the broach is withdrawn the cotton will remain in the canal. This is now saturated with the dressing, or drug indicated, and laid in the canal. One end of the cotton wisp should project into the pulp chamber in order that it may readily be removed at another sit- ting, and the cavity sealed with a gutta-percha filling. Rule : In no case should the saliva be allowed to enter a root canal after the pulp has been removed. At any future sitting the rubber dam must be applied and the included region disinfected before the gutta-percha filling is removed. Any neglect of this precaution is apt to result in alveolar abscess. In cases of dead pulps, pulps in a state of decomposition, empty root canals, alveolar abscesses, etc., the technical proc- esses of cleaning the canals are not essentially different from those described, though they may require radically different medicinal treatment. This latter is not within the province of this book. Opening the Pulp Chamber in Sound Teeth. Frequently it is necessary to open the pulp chamber of teeth that are sound, or have fillings previously inserted that it is not desirable to remove. The pulp may be dead or in such a con- dition of disease that it should be removed. In these cases it becomes necessary to cut from the surface of the tooth or through the filling. In case of the incisors or cuspids the best place to enter the pulp chamber is through the central portion of the lingual surface. For this purpose a bibeveled drill, one milli- meter in diameter, should be first used. With this the enamel should be penetrated and the drill forced a little distance into the dentin. Then this opening should be considerably enlarged by a larger drill or a round bur. Then the small drill should be forced carefiilly into the pulp chamber. If the pulp is alive and sensitive, it should now be destroyed. Afterward the complete opening of the chamber may be jjroceeded with. If the pulp is dead, the fiirther opening of the chamber may be done at once. In cutting into the pulp chamber the drill has entered from 148 THE TECHNICAL PROCEDURES IN FILLING TEETH. the lingual at a considerable inclination, and it is now necessary to make the opening as near parallel with the length of the pulp canal as practicable. To do this use a fissure bur, pass its end into the pulp chamber and bring the hand-piece slowly parallel with the long axis of the tooth, cutting mostly from the incisal wall of the opening first made, but also cutting some from the distal wall of the pulp chamber. This cutting should be suf- ficient to admit a broach to the full length of the canal, with very little bending. The cleaning and treatment of the canal can then be proceeded with. Generally, when incisors have proximate fillings that are good, the opening into the pulp should be made from the lin- gual, without disturbing the fillings. If, however, there is reason for removing a proximate filling, the pulp chamber should be opened through the cavity. In case of bicuspids and molars the opening should be made through the occlusal surface. In bicuspids the mesial pit should be chosen. In molars it is generally much easier to penetrate the enamel through the pit in the central fossa. In this case, as soon as the dentin has been entered, it is best to introduce a small inverted cone bur, and cut a slot to the mesial, inclining to the buccal, as far as the mesial marginal ridge, and chip the enamel from its margins. The length of this toward the mesial will depend on the position of the tooth and the incli- nation of the hand-piece in drilling through the dentin. The dentin is thick, and in passing through it, this inclination will often carry the hole considerably to the distal. Therefore, in beginning again with the drill it should be set sufficiently to the mesial so that it will strike the pulp chamber centrally, or to the mesial of its center. In drilling through the dentin the small drill (one millimeter in diameter) should first be made to pene- trate a little, and then the hole enlarged, then drilled deeper and enlarged, until the dentin has been cut through. If the pulp is alive and sensitive, it should now be destroyed ; if dead, the opening may at once be so enlarged as to remove the entire roof of the pulp chamber, and the treatment of the canals pro- ceeded with. Never undertake to treat pulp canals through a little bit of an opening. In a considerable number of cases it is necessary to open the pulp chambers of bicuspid and molar teeth that have been filled. FILLING ROOT CANALS. 149 If the fillings are good, proceed as if the tooth was sound, cut- ting through the filling, or through the dentin, as the case demands. If there is reason for removing the filling, do so at once, and open the pulp chamber through the cavity. Filling Root Canals. When it is decided that the conditions are right for filling the root canal, or canals of a tooth, the rubber dam must be placed and the included region disinfected. Then if a treatment has been in the canal the gutta-percha filling and the dressing is removed and a critical examination made as to its condition. If this is satisfactory, first see that the canal is reasonably dry, then flood it with eucalyptol or oil of cajuput, liberally applied upon a wisp of cotton wrapped upon a broach, and dry out the excess with a fresh wisp of cotton that has first been dipped in the oil and well squeezed out with another wisp of cotton. Try the sizes of the root canal pluggers in the canal, always washing the point with an antiseptic first, and select one that will pass nearly, but not quite, to the apical foramen. Select a gutta-percha cone and cut a portion of it about three or four millimeters long of the size which, from the information gained of the size of the apical end of the canal, will be sufficient to fully fill the opening and not force through the apical end. Warm the point of the root plugger selected, and holding the piece of gutta-percha cone in the thumb and finger of the left hand, bring its point quickly in contact with its large end, and hold it a moment, or until the gutta-percha has stuck to the end of the instrument. Dip this into eucalyptol, which will soften the surface of the gutta-percha slightly; convey this to the root canal and start it in carefully, and carry it firmly into its apical end. On withdrawing the root plugger the gutta-percha cone will remain, closing the apical end of the root. Repeat this with other bits of gutta-percha cones ; cut them from larger parts of the cones as the canal is filled to its larger portion and use the larger root canal plugger. After the first two or three pieces the subsequent ones may be slightly softened by passing them quickly over the flame of the annealing lamp and directly into the canal. Continue this until the canal is full. This plan of filling root canals is applicable to all except the very smallest, and to all positions. In some of the smaller ones 150 THE TECHNICAL PROCEDURES IN FILLING TEETH. it is necessary to make a special root canal plugger for the case by cutting ofif the barbed portion of a Donaldson broach of a suitable size and squaring its end on the stone. Rationale of this procedure. — By flooding the root canal with eucalyptol or oil of cajuput the moisture is effectually removed. The oils have a greater affinity or attraction for the dentin than the moisture and displace it. These oils dissolve gutta-percha slightly, and the little remaining serves to stick the gutta-percha firmly to the walls of the canal. By putting in the gutta-percha in small pieces an opportunity is given to pack every portion of the canal and all of its irregularities full. In filling root canals that are very large at the apical end, as in young persons, care must be exercised that the first cone selected is not so small that it could be forced through into the apical space. In very small canals, in which there is much doubt of being able to reach the apical end, chloro-percha * should be pumped into them, filling them as completely as pos- sible, and then a small solid cone forced in. This pumping in of chloro-percha is done by wrapping three or four fibers of cot- ton firmly on a small broach, dipping this in the chloro-percha and conveying it into the canal and pumping it back and forth, repeating the operation until the canal seems to be well filled. Then thrust a root canal plugger of suitable size into it and force out some of the gutta-percha from the pulpal end. Then, having a suitable gutta-percha cone prepared, quickly stick it onto the plugger point, and thrust it as far into the canal as pos- sible. Such canals may not always be perfectly filled by this plan, or by any other. But in each case the best effort should be made. The pulp chamber should not be filled with gutta- percha. This material is much too soft to serve as a seat for a metallic filling. In any case in which it is not desirable to fill the pulp chamber with the material with which the cavity is to be filled, oxy-phosphate of zinc should be used. Horns of pulp chambers. — Attention to the horns of pulp chambers is most urgently demanded in the incisors, cuspids and bicuspids. In incisors particularly, exposures of the pulp, whether made primarily by caries, or by cutting into them, are some distance from the incisal end of the pulp, leaving an end protruding into the incisal end of the crown of the tooth. Gutta-percha dissolved in chloroform. FILLING ROOT CANALS. 151 Before filling the cavity this must be looked for and so exposed that every part of it is cleaned and filled. Any neglect in this will result in discoloration of the tooth by the decomposition of the debris left in this neglected portion of the pulp chamber. In cuspids and bicuspids the horns of the pulp are often long and slender, and penetrate far toward the ends of the cusps. Unless these are thought of, and especially looked for and cut out, so that they may be perfectly filled, discoloration of the tooth in some degree is sure to occur. INDEX. PAGE. Amalgam 97 filling with 126 instruments for filling with 130 kneading: of 128 packing, fillings 129 preparing for filling with 128 Amalgam fillings, discoloration of 126 finishing 130 importance of separating teeth for '. 127 placing matrix for 127 removing matrix from 130 where admissible 127 Annealing gold : 101 Application of force in filling with gold 105 Bite, strength of the 116 Burs in cutting out grooves 35 in cutting seats and steps 35 in making extensions for prevention 36 in making starting points tor packing gold 37 in squaring out angles of cavities 36 Cavities, beveling cavo-surface angle of 23 classification of 8 convenience form of 21 distal, in lower bicuspids, preparation of 91 filling distal, in bicuspids and molars 114 filling proximate, in incisors 114 gingival wall, in proximate 113 in incisors and cuspids, general observations on the preparation of 82 in proximate surfaces in bicuspids and molars, preparation of 85 nomenclature of, angles of 13 nomenclature of, internal parts of 10 opening, in bicuspids and molars 86 outline form of 20 proximate in bicuspids and molars, filling with combination of non-co- hesive and cohesive gold 115 removing carious dentin from 22 resistance form of 20 retention form of 21 variations in preparation of, due to position 90 Cavity nomenclature 6 nomenclature, rule for 6 preparation, general principles of 19 preparation defined 6 toilet of 23 walls, management of weak, in bicuspids and molars 92 Cement, filling with 134 Cements 131 examination of physical properties of 132 how mixed ." 131, 132 not impervious to moisture 133 154 INDEX. PAGE. Cements, shrinkage of 133 " solvent action of oral secretions on 133 " use of 133 Clamps, rubber dam 50 Classification of cavities 8 Cotton, wrapping on broach 145, 146 Cutting out angles of cavities, use of burs in 36 Cutting out grooves, use of burs in 35 Cutting seats and steps, use of burs in 35 Cutting, size of burs for 34 Dental engine, use of 34 Dental instrument gauge 26 Divisions of the surfaces of the teeth in cavity description 18 Drills, use of 38 Enamel 51 histological characters of, in relation to preparation of cavities 52 margins, nomenclature of 17 " rods, how to study the inclinations of 58 rods, inclinations of 54 " walls, finishing 23 Excavation of cavities by classes 60 Class first 60 variations in 63 second 69 " " variations in 76 third 77 " " general observations on 82 fourth 83 variations in 85 fifth 85 " " variations in 90 Excavation of cavities, order of procedure in - 19 Exposure and removal of the dental pulp 137 Extension for prevention 9, 20, 70, 78 " " " in bicuspids and molars 88 " " " use of burs in making , 36 Filling materials 97 Filling root canals 149 " " " rationale of procedure in 150 " " " with large apical opening 150 Filling, starting cohesive gold 110 with amalgam 126 " with cement 134 " with cohesive gold 105 with gold 102 " with gutta-percha 135 with non-cohesive gold 102 Finishing fillings 122 " buccal and lingual embrasures 124 " " gutta-percha 136 "in buccal and labial cavities 123 in occlusal, buccal and lingual cavities 122 obtaining roundness of contact point 125 overtrimming gingival margin in 128 proximate 124 " use of burnisher in 124 use of corundum stones in 122 " use of disks in 125 use of rubber disks in 123 use of tape in 125 INDEX. 155 PAGE. Finishing fillings, with file-cut finishing files 125 Force, direction of, to plane of walls in packing gold Ill Forms of plugger points ^^^ Forms of shanks of plugger points 108 Gold 97 " annealing ^^^ ■' condensation of gases on 9^ " destroying and restoring welding property of 100 " filling with 102 forms of • "° " welding property of ^^ Grasps, rubber-dam ^^ Gutta-percha ^^^ filling with .135 finishing fillings of 136 use of eucalyptol in filling with 135 Incisal step . . . .' Inclination of cavity walls 1 ' Instruments and instrumentation •. ^^ Instruments for packing amalgam 130 •SI Instrument grasps Introduction 1 1 Q Knathodynamometer Ligatures, use of Making starting points for packing gold 37 Management of weak cavity walls in bicuspids and molars 92 1 27 Matrix, how to place removal from amalgam fillings 130 INomenclature. cavity instrument of angles of cavities 13 ^^ 24 of enamel margins of cutting instruments 17 of internal parts of cavities. 10 19 111 \^av iL y jji\,i^c*»**vx\j** *• •• Planes of the teeth Order of procedure in cavity preparation 118 Phagodynamometer '. 17 108 108 Plugger points, forms of Plugger, forms of shanks of list of, rcfjuired stepping of point of Polishing fillings 123.125.130 12S proximate fillings 140 Pulp, anaesthetizing the 139 destroying the • 1 ^9 destroying the. With arsenic 138 exposing the exposure and removal of the instruments for removing the preparation of cavity for exposure of the 13' removal of the removing the. from root canals 144 150 Pulp chamber, horns of the opening the " in bicuspids 1^3 " in bicuspids and molars that have been filled 148 ■' in distal cavities in molars 143 " in incisors and cuspids 1''3 " in mesial cavities in molars 1''3 156 INDEX. PAGE. Pulp chamber, opening- the, in occlusal cavities in molars 142 " " " " in sound teeth 147 Relation of the size of plugger points to the application of force 106 Right-angle hand-piece 36 Root canals, filling 150 " " finding 145 " rationale of procedures in filling 150 " " removing pulp from 144 Rubber dam 41 " applying the 42 " " clamps 50 grasps 43 first 43 " second 44 third 44 fourth 45 fifth 45 ligatures in adjusting the 47 Rule for extension for prevention in bicuspids and molars 88 Rules for naming angles of cavities 13 cavities 6 walls of cavities 10, 11 Separating irregular teeth 95 Separating teeth 93 use of gutta-percha in 95 " use of wood in .■ 96 Sharpening instruments 32 Strength of the bite 116 " " " " instruments for measuring the 117 " " " measuring the 117 Use of the dental engine 34 drills 38 gutta-percha in separating teeth 95 ligatures 47 water \ 38 wood in separating teeth 96 Water, use of 38 Welding property of gold 99 RK541 Black B56 filling teeth, 111947 9^ ^^"-^' ^A^yT^/ /^^6 COLUMBIA UNIVERSITY LIBRARIES (tisl.stx) RK 541 B56 C.1 The technical Procedures in tillinqte^^^^ 2002447916