EstheticsinanteriorfixedbridgeprosthodonticsGeorgeM.Moulton, D.D.S., Atlanta, Ga.Objcctives of crown and bridge prosthe-on the original contour of the tooth andsis are restoration of function and thewill bearesult of thatcontour ratherthanrestoration of esthetics.This paper re-of the initial attempt to establish thisviews and emphasizessome of themorelabial margin. It must be kept in mindimportant points in the achievement ofthat flat, rigid disks are being utilized toan esthetic replacement in anterior fixedproduce these cuts. If, for example, anattempt is made to establish the marginbridge prosthodontics.toward the gingiva in a self-cleansingarea, this ffat rigid disk will overextendPREPARATION OF ABUTMENTthe margin at the incisal third. This ex-The success of a restoration starts withplains why many times an unnecessaryamount of gold is displayed at the incisalthe preparation of the abutment; this isobvious when failures and successes arethird from the labial aspect.analyzed from an esthetic point of view.After the procedure has been com-pleted to the point of preparing theA few points regarding the selection ofmesial and distal resistance grooves, thethe retainer and its preparation will bepractitioner returns to the labial margin.considered.Thethree-quartercrownisWhether or not an incisal resistanceperhaps the most widely used retainer forupper anterior abutments. Although itgroove has been used, the starting pointof the mesial and distal grooves is ap-has its limitations, it satisfies to a greatextent the requirements of a retainer. Itproximately the same. These grooves arcis in its preparation, however, that theprepared parallel with the labial incisaltwo-thirds. This will provide the longestpractitioner may go amiss (Fig. 1, left)particularly in the mesial and distal slicespossible grooves and will, generally,avoidthe mesial and distal concavities. Thesewhich usually are the first steps of thispreparation.grooves will,however,be"tucked in"beInsofar as possible, the characteristichind thelabial line angles.Insofar ascontourof thetoothfrom thelabialas-possible the dentist is actually establish.pectmust bemaintained;thatis,fromaing the labial margin of the preparationlabial aspect the tooth should still retainwith the labial wall of these grooves, soits square, ovoid or tapering contours.that not only the direction of the grooveStated another way, the mesial and distalbut the eventual esthetics resulting fromslices should reduce only the height ofthis preparation may be controlled.contour and there should be no attemptwith the mesial and distal slices to estab-P:esented before the sectionon partial_prosthodontics.lish the labial margins of the preparation.ninety-fifthanDentalAssociasession,tion,Miami,Fia.,November 9,1954.The extent to which the labial margin isChairmap,crown.and,bridge prosthesis,School ofproduced with these slices depends onlyDentistry,EmoryUniversity.36
Esthetics in anterior fixed bridge prosthodontics George M . M ou lton , D .D .S ., Atlanta, Ga. Objectives of crown and bridge prosthesis are restoration of function and the restoration of esthetics. This paper reviews and emphasizes some of the more important points in the achievement of an esthetic replacement in anterior fixed bridge prosthodontics. PREPARATION OF ABUTMENT Th e success of a restoration starts with the preparation of the abutment; this is obvious when failures and successes are analyzed from an esthetic point of view. A few points regarding the selection of the retainer and its preparation w ill be considered. Th e three-quarter crown is perhaps the most widely used retainer for upper anterior abutments. Although it has its limitations, it satisfies to a great extent the requirements of a retainer. It is in its preparation, however, that the practitioner may go amiss (Fig. 1, left) particularly in the mesial and distal slices which usually are the first steps of this preparation. Insofar as possible, the characteristic contour of the tooth from the labial aspect must be maintained; that is, from a labial aspect the tooth should still retain its square, ovoid or tapering contours. Stated another way, the mesial and distal slices should reduce only the height of contour and there should be no attempt with the mesial and distal slices to establish the labial margins o f the preparation. Th e extent to which the labial margin is produced with these slices depends only on the original contour of the tooth and w ill be a result of that contour rather than of the initial attempt to establish this labial margin. It must be kept in mind that flat, rigid disks are being utilized to produce these cuts. If, for example, an attempt is made to establish the margin toward the gingiva in a self-cleansing area, this flat rigid disk w ill overextend the margin at the incisal third. This explains why many times an unnecessary amount of gold is displayed at the incisal third from the labial aspect. A fter the procedure has been completed to the point of preparing the mesial and distal resistance grooves, the practitioner returns to the labial margin. W hether or not an incisal resistance groove has been used, the starting point of the mesial and distal grooves is approximately the same. These grooves are prepared parallel with the labial incisal two-thirds. This w ill provide the longest possible grooves and will, generally, avoid the mesial and distal concavities. These grooves will, however, be “ tucked in” behind the labial line angles. Insofar as possible the dentist is actually establishing the labial margin of the preparation with the labial wall of these grooves, so that not only the direction of the groove but the eventual esthetics resulting from this preparation may be controlled. P.esented before the section on partial prosthodontics, ninety-fifth annual session, Am erican Dental A ssociation, M ia mi, Fla., Novem ber 9, 1954. Chairm an, crown and brid ge prosthesis, School of Dentistry, Emory University. 36
MOULTON..VOLUME52,JANUARY1956.37the distal surfaces do not. In attemptingOne other point concerning estheticsshould be emphasized: it is not necessaryto prepare both the mesial and distalto show any gold on the incisal edge. Thesurfaces, the esthetic objective of replace-preparation of the incisal edge should bement may be defeated. Also, in instancesaccomplished on a bevel toward the lin-where teeth are slightly tipped or rotatedgual surface and this bevel should starttwo slices can be made, one on each oifrom the height of contour of the incisalthe abutments, and the line of insertioredge. Again, this should result in almostdirected without the overreduction oftotal hiding of the gold from the directone or more surfaces so that the prosthe-labial view.sis may be inserted;in other words, toWhether an incisal resistance groove ismake four parallel slices frequently leadsto unesthetic results.to be used will depend on the labiolin-There are instances where the placinggual bulk on the incisal edge. If the toothof even onc slice for a preparation im-is too thin labiolingually, the placementof a resistance groove will, of course, re-pairs rather than enhances a result:forexample, in the short, bulky teeth whichsult in discoloration about the margins ofdo not allow for adequate resistancethe crown from a labial aspect within agrooves in either the mesial or distalfew months after cementation. This bulksurfaces. In such instances, it is possibleis adcquate in a majority of cases, and itthat the retainer should be the three-pinis improper preparation of the lingualhood (Fig. 1, right). When this retainersurface toward the incisal edge after theaccomplishment of the incisal bevel whichis supplemented with trusses on the lin-gual surface to provide for the necessaryresults in inadequate bulk for the resist-rigidity of the casting, it has many val-ance groove,A good rule to follow in many prepara-uable uses in fixed prosthesis.tions is to remove a uniform amountthroughout; thereby, the original con-PROBLEMS OF SPACINGtours of the teeth can be retained in manyThere are other details in the construc-instances. If, however, this bulk is in-tion of anterior fixed bridgework whichadequate, the use of a lingual step or ofare worth emphasizing.It is necessary attrusses must be considered in order totimes to place a facing where the spaceprovide the required rigidity in castings.If a fixed prosthesis is to be furnishedsecms too small. If such a facing werethe patient, the operator cannot limitplaced within the space it would be un-esthetic because the harmonious effecthimself to the use of the three-quarterwould be lost. The dentist must keep incrown and meet the requirements of amind that an esthetic effect means har-fixed prosthesis, either esthetically or inmony in contour and color, and thatrelation to retention of the prosthesis.Other types of retainers must be selectedthere are many things which go to makewhich better answer the individual needs.up this effect.In the example shown inFigure 2, above, the space does not seemThe modified three-quarter crown is onelarge enoughfor placement of a facing.which has been found to be invaluableHowever,it ispossibleto placethis fac-(Fig. 1, center). This is the preparationing so that it overlaps slightly the adja-which utilizes one resistance groove, ancent abutments and carries out irregu-incisal pin and a lingual pin for reten-larities which are already apparent intion. There are many instances in whichthe mouth; thus harmony is achieved.its use is preferable to that of the three-The incisal opaque staining should requarter crown. In some ovoid teeth theproduce any or all white opaque, brownmesial surfaces often lend themselves toor other inperfections.an adequate resistance groove, whereas
M O U LTO N . . . VO LU M E 52, JA N U A R Y 1956 • 37 One other point concerning esthetics should be emphasized: it is not necessary to show any gold on the incisal edge. The preparation o f the incisal edge should be accomplished on a bevel toward the lingual surface and this bevel should start from the height of contour of the incisal edge. Again, this should result in almost total hiding of the gold from the direct labial view. Whether an incisal resistance groove is to be used will depend on the labiolingual bulk on the incisal edge. I f the tooth is too thin labiolingually, the placement of a resistance groove will, of course, result in discoloration about the margins of the crown from a labial aspect within a few months after cementation. This bulk is adequate in a m ajority o f cases, and it is improper preparation o f the lingual surface toward the incisal edge after the accomplishment o f the incisal bevel which results in inadequate bulk for the resistance groove. A good rule to follow in many preparations is to remove a uniform amount throughout; thereby, the original contours o f the teeth can be retained in many instances. If, however, this bulk is inadequate, the use of a lingual step or of trusses must be considered in order to provide the required rigidity in castings. I f a fixed prosthesis is to be furnished the patient, the operator cannot limit himself to the use of the three-quarter crown and meet the requirements o f a fixed prosthesis, either esthetically or in relation to retention o f the prosthesis. Other types of retainers must be selected which better answer the individual needs. T h e modified three-quarter crown is one which has been found to be invaluable (Fig. 1, center). This is the preparation which utilizes one resistance groove, an incisal pin and a lingual pin for retention. There are many instances in which its use is preferable to that o f the threequarter crown. In some ovoid teeth the mesial surfaces often lend themselves to an adequate resistance groove, whereas the distal surfaces do not. In attempting to prepare both the mesial and distal surfaces, the esthetic objective of replacement may be defeated. Also, in instances where teeth are slightly tipped or rotated, two slices can be made, one on each of the abutments, and the line of insertion directed without the overreduction of one or more surfaces so that the prosthesis may be inserted; in other words, to make four parallel slices frequently leads to unesthetic results. There are instances where the placing of even one slice for a preparation im pairs rather than enhances a result; for example, in the short, bulky teeth which do not allow for adequate resistance grooves in either the mesial or distal surfaces. In such instances, it is possible that the retainer should be the three-pin hood (Fig. 1, righ t). W hen this retainer is supplemented with trusses on the lingual surface to provide for the necessary rigidity of the casting, it has many valuable uses in fixed prosthesis. PROBLEMS OF SPACING There are other details in the construction of anterior fixed bridgework which are worth emphasizing. It is necessary at times to place a facing where the space seems too small. I f such a facing were placed within the space it would be unesthetic because the harmonious effect would be lost. T h e dentist must keep in mind that an esthetic effect means harmony in contour and color, and that there are many things which go to make up this effect. In the example shown in Figure 2, above, the space does not seem large enough for placement o f a facing. However, it is possible to place this facing so that it overlaps slightly the adjacent abutments and carries out irregularities which are already apparent in the m outh; thus harmony is achieved. T h e incisal opaque staining should reproduce any or all white opaque, brown or other inperfections
38THEJOURNALOFTHEAMERICANDENTALASSOCIATIONFig.I :Left: Preparation for a three-guarter crown.Center:Preparation for a modified three-quarter crown.Right: The three-pin hood (Courtesy of J. Raymond Gill, School of Dentistry,Universityof California)Another detail is the refining of theers have been prepared and temporarilyretainers justprior to takingtheimpres-seated prior to obtaining this movementsions for the working model. The excessIn the example shown, after the centralbulk of gold on the mesial, distal andincisor had been brought into contactwith the adjacent incisor, impressions forincisal surfaces after casting must be re-duced. This should not be done on thethe working model were taken, and theworking models as it is not possible tobridge acted as an absolute retainer afterget the proper perspective on thesethe orthodontic movement. The impor-models.The reduction will accomplishtance of consultation with the orthodon-many things.It will provide for themaxi-tist and use of orthodontic appliancesmum space intowhich the facing can bewhen preparing a mouth for a bettenground and will, to a great extent, ob-prosthesis cannotbe overemphasized.Ifliterate the gold margin of the retainerhowever, spaces exist generally through-and the soldered connector from theout the anterior region, it is not desirablelabial view.The importance of this reto closeany space.A type of connectorduction cannot beoveremphasizedItmust be used that will maintain the spaceshould also be stresscd that the facingor diastema. The bar type connectorselected should be slightly large, if any-shown in Figure 2,below,provides anesthetic result. Occasionally,it is possiblething, for the space. Such a facing willprovide for the necessary bulk of porce-touseabartypeofconnectortoconnecttheponticwith both retainers.Thisgiveslain for its preparation, and it can thenbe spot ground into position and shapeda normal appearance of space betweento harmonize with the abutments.teeth rather than filling in the space withIn many instances, one or more of thean unsightly solder connector.These bars,however, must be rigid enoughto standabutments have moved because of theloss of an adjacent tooth.Orthodonticthe stress to which the prosthesis will betreatment is indicated to reestablish nor-subjected; furthermore, they must bemal alignment (Fig. 2, center). Retain-just off the supporting tissue so that floss
38 • THE JO U R N A L OF THE A M E R IC A N DENTAL A S SO C IATIO N Fig. I • h eft: Preparation for a three-quarter crown. Center: Preparation for a modified threequarter crown. Right: The three-pin hood (Courtesy of J. Raymond Gill, School of Dentistry, University of California) Another detail is the refining of the retainers just prior to taking the impressions for the working model. Th e excess bulk of gold on the mesial, distal and incisal surfaces after casting must be reduced. This should not be done on the working models as it is not possible to get the proper perspective on these models. T h e reduction will accomplish many things. It will provide for the maximum space into which the facing can be ground and will, to a great extent, obliterate the gold margin of the retainer and the soldered connector from the labial view. Th e importance of this reduction cannot be overemphasized. It should also be stressed that the facing selected should be slightly large, if anything, for the space. Such a facing will provide for the necessary bulk of porcelain for its preparation, and it can then be spot ground into position and shaped to harmonize with the abutments. In many instances, one or more o f the abutments have moved because o f the loss of an adjacent tooth. Orthodontic treatment is indicated to reestablish normal alignment (Fig. 2, center). Retainers have been prepared and temporarily seated prior to obtaining this movement. In the example shown, after the central incisor had been brought into contact with the adjacent incisor, impressions for the working model were taken, and the bridge acted as an absolute retainer after the orthodontic movement. Th e im portance of consultation with the orthodontist and use of orthodontic appliances when preparing a mouth for a better prosthesis cannot be overemphasized. If, however, spaces exist generally throughout the anterior region, it is not desirable to close any space. A type of connector must be used that will maintain the space or diastema. Th e bar type connector, shown in Figure 2, below, provides an esthetic result. Occasionally, it is possible to use a bar type of connector to connect the pontic with both retainers. This gives a normal appearance of space between teeth rather than filling in the space with an unsightly solder connector. These bars, however, must be rigid enough to stand the stress to which the prosthesis w ill be subjected; furthermore, they must be just off the supporting tissue so that floss
MOULTONVOLUME52,JANUARY195639aration of this facing for its backing is,may be passed underneath the bar forof course, a requirement. A long-pin fac-proper cleansing.In any discussion of esthetics, the con-ing allows for the protection of the in-cisal edge.If the same approach is usedsideration of thetype of porcelainre-placementsutilized cannot be omitted.as in the preparation of the three-quarterThe author believes that the most es-crown, it is not necessary to show anyof gold from the labial aspectthetic facing is the long-pin porcelainamountfacing.In the past, inadequacies in por-Thesefacan be arranged in anycelain facings have been due,principally,atedfor theindividual patientto the lack of condensation of the porwill produce the artistic resultcelain.The newvacuum-fired pin facingsso much desired (Fig.3, above)nowavailablearewell condensed andAnotheanomaly is the instance inhave the desired strength.Proper prepwhich there is morethanthe normalFig.2.Above: The placement of upper right central incisor where space is inadequate andirregularities exist. Center: Simpleorthodontic treatment used to close space between lateralincisors. Below: The bar type connector used to maintain normal space between central incisors
M O U LTO N . . . VO LU M E 52, JAN U A R Y 1956 • 39 may be passed underneath the bar for proper cleansing. In any discussion of esthetics, the consideration o f the type o f porcelain replacements utilized cannot be omitted. Th e author believes that the most esthetic facing is the long-pin porcelain facing. In the past, inadequacies in porcelain facings have been due, principally, to the lack o f condensation of the porcelain. T h e new vacuum-fired pin facings now available are well condensed and have the desired strength. Proper preparation of this facing fo r its backing is, of course, a requirement. A long-pin facing allows for the protection of the incisal edge. I f the same approach is used as in the preparation of the three-quarter crown, it is not necessary to show any amount of gold from the labial aspect. These facings can be arranged in any way indicated for the individual patient and they will produce the artistic result so much desired (Fig. 3, above). Another anomaly is the instance in which there is more than the normal Fig. 2 • A bove: T he placement of upper right central incisor where space is inadequate and irregularities exist. Center: Simple orthodontic treatment used to close space between lateral incisors. Below: The bar type connector used to maintain normal space between central incisors
4O·THEJOURNALOFTHEAMERICANDENTALASSOCIATIONspace for a single missing tooth, whichbe obvious, however, that if there isaprovides space for two replacements in-deep overbite with little or no overjet, thestead of for only the one which is miss-problemof replacement becomes coming.Suchananomalypresents anplex. The central incisor must certainlyexcellent chance for the dentist to usethen be considered for use as an abutingenuity. Figure 3, center and belowment.left, shows an example in which the abut-ments are the upper left central incisorESTHETICS OF THE FULL-VENEERand the upper right lateral incisor, theRETAINERupper right central incisor having beenlost.If anattemptweremadetoplaceTheproblem of theanterior replacementthe missing central incisor in this space,cannot be left without discussing theit would obviously produce an unestheticnecd for a full-veneer retainer to obtainresult, If a central and a lateral incisoran esthetic result. This need is apparentwereplaced inthis space it would lookfor mouths in which extensive restora-from the labial aspect as if there weretions involve a good deal of the labialtwo lateral incisors on the right side, andsurfaces, or for those which presentthis would create lack of symmetry. Theanomalies of form or color which muslateral incisor that is the abutment in thisbe corrected to produce a pleasing re-instance obviously occupies the positionsult. Many patients are satisfied with theof the upper right cuspid. Therefore, toporcelain jacket crown which is and al.prodluce the desired harmony, this upperways has been the most esthetic restora-right lateral incisor must be prepared ontion.Of late, however, many schools areits incisal edge to simulate a cuspid. Theomitting the construction of the por-right lateral incisor now harmonizes withcelain restoration from the training andthe left cuspid and symmetry has beenothers are content with teaching therestored to the upper anterior segment.placement of one such restoration. ThisOne of the replacements most fre-is woefully inadequate training for thequently needed in the anterior mouth isyoung dentist who may wish to prescribeprobably the lost lateral incisor (Fig. 3,a porcelain restoration.below right). It is the author's opinionIn addition, the widespread use ofthat this is the one instance in which theacrylic resins in dentistry has caused aswing bridge" can and should be utilized.severe setback in the use of porcclainObservation will show that this type ofThere must be a re-evaluation of teach-construction frequently renders the long-ing and ideas relative to the use of theseest service of all fixed prostheses. Thetwo materials. Certainly, for the unittype referred to is strictly a single bridgerestoration, if the conditions are favor-replacement and does not have any at-able, particularly the occlusion, the por-tachment or arm on the adjacent centralcelain jacket is by far the best restoration.incisor. In such instances,judgmentAt the same time, the limitations of anymust be used in the treatment planning.material must be realized. Porcelain isIf the central incisor is involved withbrittle and will not stand undue stress.caries or restorations, it might be con-Therefore, in patients who have a deepsidered for use as an abutment.Probablyoverbite and little or no overjet in themore important,however,is the studyofanterior region of the mouth, the use of athe occlusion. If there is a normal over-full porcelain crown is contraindicated.bite-overjet relationship, this type of con-In such instances, failure would result,struction will serve very well; it willwith a fracture of the porcelain acrossalso where there is more than normalthe area of the cingulum. Under suchoverjet with little or no overbite. It shouldcircumstances a more durable type of
40 • THE JO U R N A L O F THE A M E R IC A N DENTAL AS S O C IA TIO N space for a single missing tooth, which provides space for two replacements instead of for only the one which is missing. Such an anomaly presents an excellent chance for the dentist to use ingenuity. Figure 3, center and below left, shows an example in which the abutments are the upper left central incisor and the upper right lateral incisor, the upper right central incisor having been lost. I f an attempt were made to place the missing central incisor in this space, it would obviously produce an unesthetic result. I f a central and a lateral incisor were placed in this space it would look from the labial aspect as if there were two lateral incisors on the right side, and this would create lack of symmetry. T h e lateral incisor that is the abutment in this instance obviously occupies the position of the upper right cuspid. Therefore, to produce the desired harmony, this upper right lateral incisor must be prepared on its incisal edge to simulate a cuspid. The right lateral incisor now harmonizes with the left cuspid and symmetry has been restored to the upper anterior segment. One of the replacements most frequently needed in the anterior mouth is probably the lost lateral incisor (Fig. 3, below righ t). It is the author’s opinion that this is the one instance in which the “ wing bridge” can and should be utilized. Observation w ill show that this type of construction frequently renders the longest service of all fixed prostheses. Th e type referred to is strictly a single bridge replacement and does not have any attachment or arm on the adjacent central incisor. In such instances, judgment must be used in the treatment planning. I f the central incisor is involved with caries or restorations, it might be considered for use as an abutment. Probably more important, however, is the study of the occlusion. I f there is a normal overbite-overjet relationship, this type o f construction w ill serve very w ell; it will also where there is more than normal overjet with little or no overbite. It should be obvious, however, that if there is a deep overbite with little or no overjet, the problem of replacement becomes complex. T h e central incisor must certainly then be considered for use as an abutment. ESTHETICS OF TH E FULL-VENEER RETAINER Th e problem of the anterior replacement cannot be left without discussing the need for a full-veneer retainer to obtain an esthetic result. This need is apparent for mouths in which extensive restorations involve a good deal of the labial surfaces, or for those which present anomalies of form or color which must be corrected to produce a pleasing result. M any patients are satisfied with the porcelain jacket crown which is and always has been the most esthetic restoration. O f late, however, many schools are omitting the construction of the porcelain restoration from the training and others are content with teaching the placement of one such restoration. This is woefully inadequate training for the young dentist who may wish to prescribe a porcelain restoration. In addition, the widespread use of acrylic resins in dentistry has caused a severe setback in the use o f porcelain. There must be a re-evaluation of teaching and ideas relative to the use of these two materials. Certainly, for the unit restoration, if the conditions are favorable, particularly the occlusion, the porcelain jacket is by far the best restoration. A t the same time, the limitations o f any material must be realized. Porcelain is brittle and w ill not stand undue stress. Therefore, in patients who have a deep overbite and little or no over jet in the anterior region o f the mouth, the use of a full porcelain crown is contraindicated. In such instances, failure would result, with a fracture of the porcelain across the area o f the cingulum. U nder such circumstances a more durable type of