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Gingival crown margin configurations: A review anddiscussion. Part I: Terminology and widthsA. J. Hunter, B.D.S., M.D.&., D.R.D.R.C.S., and A. R. Hunter, B.D.S., M.D.S.Dunedin, New ZealandThe terms bevel, chamfer, and shoulder are widely used to describe crown margindesigns. However, as no clear definition of the essential feature(s) of each designhas been universally accepted, the same term often describes margins of widelydiffering width andlor configuration. Similarly bevel angles are not consistentlydefined. While tradition favors the use of thinner marginal designs, many of thereasons advanced for their superiority are questionable in the light of contempo-rary research. Use of marginal widths beyond the absolute minimu m demanded ofthe material may contribute to overcoming some of the persistent problemsidentified with fixed prosthodontic replacement of natural teeth. These includeovercontour, porcelain debonds, poor esthetics, and fit. It is suggested that theproblems associated with underpreparation and the potential advantages of widerpreparations need reemphasis. (J PROSTHET DENT 1990;64:548-52.)

T 00th preparation for fixed prosthodontics re-quires a decision regarding the marginal configuration. Thedesign dictates the shape and bulk of the casting andinfluences the fit at the margin.l Although many factorssuch as materials, esthetics, and access influence thisselection, most dentists probably have a preferred de-sign, However, there is disagreement about what consti-tutes ideal marginal geometry and width. These articlesreview the issues involved and discuss the implications ofresearch into the clinical longevity of crowns related to themarginal design. Part I discusses terminology and marginwidth, while Part II reviews the theoretical and practicalmarginal geometry.TERMINOLOGY AND DEFINITIONS

At presen t there is no universally accepted basis forclassifying margin designs, and many texts avoid verbaldefinitions in favor of illustrations.1-6 Unfortunately, thisapproach does not clearly distinguish the essential fea-ture(s) of each design and therefore illustrations of cham-fers or shoulders are often misleading (Fig. I).Chamfers have been defined on the basis of theirmarginal width and/or geometry. Jacobsen and Robinson7stated that a width greater than 0.3 mm at its cervical ter-mination precluded any margin being called a chamfer.Others? 6 g consider an obtuse angled gingival terminationor curved cross-sectional shape to be fundamental forchamfers. Bell et al.1 described a chamfer preparation witha reduction of 1.5 mm, rounded internal line angles, and acavosurface angle of 135 degrees. However, their shoulderpreparations were identical except for cavosurface angle,and this feature was crucial in classifying marginal designs.However, illustrated examples demonstrating rounded in-

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ternal line angles and cavosurface junctions of approxi-mately 90 degrees have also been termed chamfersir, r2Similar problems arise with attempts to define. shoul-ders. Many classify a flat shoulder as one that makes a 90-degree angle with the vertical axial wall o f the prep-aration.2l 8,g, 3 This classification presumably relies onwidth to determine the marginal type, while the angulationfrom the vertical axial wall indicates marginal direction

(for example, 135-degree shoulder). With any classificationbased on width, substantial differences arise with changesin marginal angulation. Some shoulders may exhibit slipjoint geometry (135-degree shoulders) but others may not(go-degree shoulders).Shoulders have also been defined using marginal geom-etry, where the discriminating features are an external ca-

vosurface angle of 90 degrees and a corresponding buttjoint of restoration/tooth at the marg in.? 3l 5, o Dependingon the apical extent o f the preparation, and the axial pro-file of the tooth, a go-degree shoulder using this classifica-tion may often appear similar to a 135-degree shoulder asdefined by McLean and Wilson.i3Bevels are another recommended marginal design be-cause they incorporate geometric principles to minimizemarginal discrepencies. l, 12, 4, 5 It is important to realizethat bevel angulation may be assessed from differentplanes (Fig. 2). Some authorities define the angle of thebevel as the angle between the created bevel surface and thepreparation surface that has been bevelled,13* 49 6-18 hileothers describe it as the angle between the created bevelsurface and the external surface of the tooth.3, lo* gs2i Theformer definition of bevel angulation will be used through-out these articles.For convenience, Kuwata22 classified margins on the ba-sis of their margin angle. This is the angle formedbetween a vertical projection from the external surface ofthe tooth and its prepared surface (Fig. 2, angle b). He

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: :3eFig. 1. Margin illustrations. a, Long chamfer. b and c,Chamfers; note differing exit profiles. d, Flat or go-degreeshoulder, based on the preparation axial wall. e, Slopedshoulder (on axial wall) or go-degree shoulder, based oncavosurface angle.considered that margin angles between 0 and 30 degreesgave bevelled margins, those between 31 and 60 degreeswere chamfers, and those between 61 and 90 degrees wereshoulders.

A practical system for classifying margins was advancedby Pardo, l2 who broadly catego ized margins into the twomain classes of inclined vertical or horizontal. A go-degreeshoulder was considered a horizontal margin and the 135-degree shoulder was considered an inclined vertical design.Although this classification emphasized the importance ofexit configuration while ignoring margin width, in practicethe horizontal designs are often wider.Another source of confusion is the different terminologyfor describing discrepancies between the casting and thetooth. These discrepancies may be the result of inaccura-cies inherent in crown fabrication; an inability to correctlyseat the crown during cementation, or a combination ofthese factors. These discrepancies are commonly measuredat the external margin of the crown or at right angles to thetwo opposing surfaces (Fig. 3). The former has beendescribed as the vertical discrepancy,14 the margina lopening measured verticaIly,23 o r the minimal marginalcement thickness.16 The discrepancy at right angles to thetwo opposing surfaces has been referred to as the margin-al opening, 15t24 the horizontal discrepancy,14 or themarginal adaptation.23 The least confusing terminologyis the use of the term seating to describe the vertical dis-crepancy at the external margin, and the term sealing todescribe the horizontal discrepancy observed at right

angles to the two opposing surfaces.11s 1

Fig. 2. Bevel angles. Angle a is the angle formed by thecreated bevel surface with the surface that has been bev-elled. Angle b is the angle formed by the created bevel sur-face with the external surface, also called margin angle. 180degrees -a = b.

MARGINAL WIDTHFor simplicity, concepts related to marginal width and

geometry can usually be discussed independently. Theminimum marginal width of a crown is largely determinedby the dental materials used, while the maximum width islimited by the desire to preserve both a suitable coronalcore and pulp vitality. Within these general parameters,marginal widths may vary, with designs exhibiting minimalaxial reduction favored when possible.25 These includeregular chamfers and knife edges (including feather andchisel edges) that would seldom be wider then 0.3 mm.Marginal widths below 0.3 mm

The cited advantages of thin margins are that these de-signs allow for intraoral finishing of the crown margins, areconservative, and their geometric configuration improvesthe marginal seal.1,6-8 Because minimal reduction is re-quired, preparation of knife-edge margins has been con-sidered to. be relatively easy.s,s, 26However, others considerthat achieving a definite finish line with a knife-edge con-figuration is also difficult and requires careful prep-aration.1,4 Crown fabrication is also a problem, as thesemargins are often indistinct on the impression and die.4, 7In addition, overcontoured restorations are commonlyproduced to obtain sufficient bulk of restorative material toensure functional rigidity. l, 7 Although sometimes recom-mended for routine use,26knife-edges are not a preferreddesign72 5 and should be restricted to specific clinical sit-

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Fig. 3. Diagram illustrating discrepancies between cast-ings and teeth. a, Seating discrepancy. 6, Sealing discrep-ancy.

uations such as their use in extremely bell-shapedteeth., 2,8,27Greater axial reduction (up to 0.3 mm7) is required forchamfers that many consider the ideal gingival finishline for cast restorations.l* 4,6s~ 5This increased width al-lows easier evaluation of the margin at all stages andreduces the chances of an overcontoured casting, while al-lowing adequate rigidity. While possessing these practicaladvantages, chamfers retain the benefits of the thinner

knife-edge design.Many consider that thin margins (including bevels) aredesirable because they allow for marginal closure throughfinishing procedures.? 5-7* 0* 7-2g hese procedures includespinning and swaging, the use of disks and stones to movemetal to the margins , and burnishing to bend the crownmargin toward the tooth. Stiffler in 1980 reported a 50%reduction in the marginal opening if accessible, and wherethe type of alloy permitted the use of rotary instruments forburnishing (cited by Scharer2g).However, others consider intraoral finishing proceduresfor gingival margins difficult and impractica16* 15, 1, 3Thedentists ability to objectively evaluate the cervical marginsof crowns appears to be limited, particularly in approximaland subgingival locations.28p 0-32 ssif et a1.32 elieved thatthere was a direct relationship between the location o f re-storative margins and the ability to evaluate them by sight

or with an explorer, with the efficacy of the examinationbecoming increasingly questionable the more subgingivalthe margin. Even if objective evaluation were possible,limited access for instruments precludes marginalfinishing.5s 13, 3, gl33Where accesspermits, disks and stonescan be effective in achieving marginal closure, but bur-nishers appear ineffective in reducing d iscrepancies.34g 5Although margin finishing of complete cast crowns duringcementation is often recommended,20*2s,2gv 3 the timeavailable is limited as these procedures must be completedwhile the cement remains fluid.13, 33The limited ductility and high yield strength of manyalloys also limits the effectiveness of finishing procedures.Although Gilboe and Thayer 27accepted that type 3 goldpossessed imited ductility, they maintained that thin cer-vical margins did allow for bending of the metal to improvethe marginal seal. Conversely, Behrend23 considered thatburnishing of margins was impossible with the current hardalloys. Gardiner15 also concluded that burnishing was nota practical way of achieving marginal closure for type 3 goldand ceramometal alloys. Others2g*36also consider ceramo-metal alloys unsuitable for burnishing, while McLean andWilson13 noted that the pressures and distortion of metal,associa ted with the technique, could crack porcelain bondedto these alloys. Alloys with Brine11 hardness numbersgreater than 84 or 100 are unsuitable for burnishing.5s l5Marginal widths greater than 0.3 mm

Margin widths greater than 0.3 mm, often referred to asshoulders, have been unpopular, particularly if a chamfercould be placed. Tylman and Malonesstated that shoulderswere difficult to prepare on posterior teeth, and that theirroutine use was difficult to justify when stress analysis, mi-croleakage, and pulpal response were considered. O thersagreed , and considered shoulders unnecessarily destruc-tive,, bulky,6 and unsuitable for marginal finishing unlessmodified with a beve1.l. 4*7s 31 4 The thickened wax pat-terns resulting from wider margins also exhibit increasedcasting shrinkage, although this can be compensated for byeffective die spacing.3Despite their unpopularity, the advantages of widermargins over thinner designs should be considered. Theseadvantages include improved control of crown contoursand esthetics, increased structural rigidity, and clearer im-pressions and dies.According to Gilboe and Thayer,27 an advantage of bev-elled shoulder preparations were that they allowed the in-corporation of physiologic contours in both the temporaryand final crown. Increased tooth reduction also facilitatescontour changes in the crown, permitting guide planes forremovable prostheses, or flattening contours to facilitateplaque control.8, 27Some believe that with good oral hygiene, minor changesin crown contour ( + 1 mm) do not significantly affect gin-gival health.%, 3gHowever, increases in crown contour usu-ally compromise gingival health by impeding plaqueremoval29 9 21, 3, o-42Fankhauser, cited by Scharer,2g in

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1979 reported that minor changes in contour led to in-creased gingival bleeding and that many ceram ometalcrowns were overcontoured by a mean value of 0.5 mm.Overcontoured crowns are a common problem,41 partic-ularly approximallf13, 44 and with ceramometal restora-tions.2 Karlsso# discovered that a significant numberof ceramometal restorations were overcontoured approxi-mally, and others have reported that 25% to 80% of com-plete cast crowns are overcontoured.45-47 Parkinson47 re-ported that although cast crowns were less overcontouredthan ceramometal restorations, differences in plaque scoreswere not significant, both being significantly higher than inthe uncrowned controls. These studies indicated that theproblem of overcontour was not confined to ceramometalrestorations and that small increases in contour can ad-versely influence gingival health. Grass0 et a1.46 uggestedthat unsuitable embrasures and contours were a greaterproblem with crowns than were inadequate gingival cavo-surface margins.Another advantage of greater axial reduction is that itpermits a greater thickness of restorative material, thusensuring rigidity during func tion.27 Crown flexure predis-poses to cement failure, and with ceramometal crownsthere is the additional hazard of porcelain failure.48, 4gAl-though Karlsson44 and Coornaert et a1.4geported compar-atively low rates of porcelain fracture, Walton et a1.50reported that porcelain fractures and debonds were thesecond highest cause of failure with ceramometal crowns.The rate of porcelain failure due to flexure appears to berelated to the thickness of the metal substructure and toocclusal factors, particularly bruxism.44, 48* g, 1Distortion of ceramometal substructures can occur dur-ing crown fabrication.2p 13xa 51-54 his distortion has beenattributed to temperature-related creep of the alloy53v55, 6or to a thermal expansion mismatch between porcelain andalloy. 13*52Whatever the exact cause, this distortion is acommon problem. Karlsson44 found that although ceramo-metal and acrylic resin veneered crowns had a similarfrequency of poor marginal adaptation, the size of thediscrepancy was significantly greater with ceram ometa lcrowns. He attributed this finding to weak metal substruc-tures that were distorted during the fabrication process.Many consider that increasing the bulk of metal, particu-larly at the internal line angles, increases resistance tomarginal distortion.15, 31, 2, 3 Thus increased marginalwidths (shoulders) have usually been recommended as amethod of minimizing these discrepancies51, 5sThe desire to enhance esthetics without sacrificingstrength is a crucial consideration when using ceramometalrestorations, but a high proportion of ceramometal resto-rations a re judged unacceptable by patients due to pooresthetics.50 Good marginal integrity, suitable marg in loca-tion, and harmonious contour a re all important in achiev-ing optimal esthetics.23s 3, 8, 7, 8 Overcontoured crownsare unlikely to blend with natural counterparts due to theirpoor shape and adverse effect on gingival tissues.ss*43Highreflectance of the opaque layer, particularly at the margins,THE JOURNAL OF PROSTHETIC DENTISTRY

is another common esthetic problem with ceramometalrestorationss All these problems can be minimized byproviding adequate marginal width to accommodateboth metal and porcelain, without overcontouring. Unfor-tunately, there are variations in opinion regarding themargin reduction required for ceramometal restorations,with suggestions ranging from 1 to 2 mm. 32,5,4s+ gBecauseoptimal esthetics depend on adequate reduction, it may bedesirable to increase the marginal width of preparationstoward the upper limit of the recommended range.The effect of increased marg in widths on the ease of theclinical procedures is disputed. Some consider flat or slopedshoulders difficult to prepares l8 or impractical with smallteeth or when excessive root surfaces are exposed.5g Ac-cording to Gilboe and Thayer,27 the increased width asso-ciated with bevelled shoulders facilitates the placement ofgingival retraction cord, while the increased bulk of im-pression material at the gingival margin results in more ac-curate impressions and dies. Increased bulk is useful wherethe impression material possesses imited tear strength. Incontrast, Schweikert2j and Panno et a1.5g stated thatshoulder preparations made impression making difficult,especially for multiple preparations. Perhaps the greatesteffect of increased margin widths clinically is the ease ofevaluating preparations, impressions, and dies. Shouldersare commonly well defined and according to some createthe clearest finish line.g Picard reiterated that a poor im-pression, even of a good preparation, will produce a poor dieand ultimately lead to a poor final result. The ability to ac-curately evaluate margins, particularly at the impressionstage is crucial to ensuring an acceptable crown and is amajor advantage of wider preparations.CONCLUSION

Tradition has favored thin marginal designs, with theconsequence that there is a tendency to underprepareteeth. Inadequate preparation is cited as the reason formany of the problems associated with crowns.2p 1* 3, g, 3, 4The consequences of underpreparation are usually worsethan those associa ted with preparations that are wider thanthe absolute minimum required by the restorative mate-rial.Thin finish lines have been advocated in the belief thatthey allow marginal closure through intraoral finishing andcontribute to the maintenance of pulpal vitality. However,a review of the literature indicates that the efficacy of in-traoral finishing procedures should be reassessed. Theability of dental technicians to produce anatomic crowncontours while working to the minimum possible thicknessof material has also been overes timated. If maintaining anormal emergence profile is important, then wider marginsallow easier fabrication of appropriate ly contoured crownswhile also improving rigidity and esthetics.While conservation of tooth structure is desirable, thisprinciple is not an absolute contraindication to increasingmarginal width beyond the minimum to accommodate thematerials being used. Experience with shoulder prepara-

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tions suggests hat margin widths exceeding 0.3 mm are notusually incompatible with pulpal vitality. If the advantagesof increased preparation were stressed, rather than theconservation of tooth tissue, dentists might be encouragedto increase marginal widths where possible.REFERENCES

1. Shillingburg HT, Hobo S, Whit&t LD. Fundamentals of fixed prosth-odontics. 2n d ed. Chicago: Quintessence Publishing Co, 1981:90-3,118.2. Roberts DH. Fixed bridge prostheses. 2nd ed. Bristol: John Wright &Sons, 1989:112-4.3. Carbeneau GT, Cartwright CB, Comstock FW, et al. Principles andpractice of operative dentistry. 2nd ed. Philadelphia: Lea and FebigerPublishing Co, 1981:377-a.4. Gihnore HW, Lund MR, Bates DJ, Vernetti JP. Operative dentistry. 4thed. St Louis: CV Mosby Co, 1982:263-4,333-4.5. Baum L, Phillips RW, Lund MR. Textbook of operative dentistry. 2nded. Philadelphia: WB Saunders Co, 1985:532-3,573.6. Pitt-Ford TR. The restoration of teeth. Oxford: Blackwell ScientificPublications, 1985:185-6.7. Jacobsen PH, Robinson PB. Basic techniques and materials for conser-vative dentistry. 3. Restoration of the broken down posterior tooth. JDent 1981$X01-8.8. Tylman SD, Malone WFP. Tylmans theory and practice of fixedprosthodontics. 7th ed. St Louis: CV Mosby Co, 1978:112-3,116-7,214.9. Picard HM. A manual of operative den tistry. 5th ed. New York: OxfordUniversity Press, 1983:231-2.10. Bell CJ, Bowden JR, Saund P, Smith M, Stephenson RI. The Dicercastable ceramic crown. Dent Practice 1987;25:20-5.11. Gavelis JR, Morency JD, Riley ED, Sozio RB. The effect of variousfinish line preparations on the marginal seal and occlusal seat of fullcrown preparations J PROSTH~ DENT 1981;45:138-45.12. Pardo GI. A full cast restoration design offering superior marginalcharacteristics. J PROSTHET DENT 1982;38:539-43.13. McLean JW, Wilson AD. Butt joint versus bevelled gold margin inmetal-ceramic crowns. J Biomed Mater Res 1980;14:239-50.14. Rosner D. Function, placement, and reproduction of bevels for goldcastings. J PROSTHET ENT 1963;13:1160-6.15. Gardiner FM. Margins of complete crowns-literature review. J PROS-THET DENT 1982;48:396-400 .16. Grajower R, Lewinstein I. A mathematical treatise on the fit of crowncastings. J PROSTHETDENT 1983;49:663-73.17. Ostlund LE. Cavity design and mathematics: their effect on gaps at themargins of cast restorations. Operative Dent 1985;10:122-37.18. Donovan T, Prince J. An analysis of margin con figurations for metal-ceramic crowns. J PROSTHETDENT 1985;53:153-7.19. Rosenstiel E. The marg inal fit of inlays and crowns. Br Dent J1964;117:432-42.20. Kashani HG, Khera SC, Gulker IA. The effects of bevel angulation onmarginal integrity. J Am Dent Assoc 1981;103:882-5.21. Gulker I. Margins. NY State Dent J 1985;51:213-7.22. Kuwata M. Gingival margin design of abutments for ceramometal res-torations. 2. Quintessence Dent Technol 1979;10:27-38.23. Behrend DB. Crown margins and gingival health. Ann R Auat Co11DentSurg 1984;8:138-45.24. Pascoe DF. An evaluation of the marginal adaptation of extracoronalrestorations during cementation. J PROSTH~ DENT 1983;49:657-62.25. Fusayama T, Ide K, Hosada H. Relief of resistance of cement of full castcrowns. J PROSTHETDENT 1964;14:95-106.26. Schweikert EO. Feather-edged or knife-edged preparation and impres-sion technique. J PRO~THETDENT 1984;52:243-6.27. Gilboe DB, Thayer KE. Bevelled shoulder concep t: full gold crownpreparation. Can Dent Assoc J 1980;46:519-23.28. Christensen GJ. Marginal fit of gold inlay castings. J PROSTHET ENT

1966;16:297-305.29. Scharer P. In: Dental ceramics. Proceedings of the First InternationalSymposium on Ceramics. Chicago: Quintessence Publishing Co,1983:295-7,301-3,311.30. McLean J W, van Fraunhofer JA. The estimation of cement film thick-ness by an in viva technique. Br Dent J 1971;131:107-11.31. Belser UC, MacEntee MI, R ichter WA. Fit of three porcelain-fused-to-

metal marginal designs in viva: a SEM study. J PROSTHETDENT198$53:24-g.32. Assif D, Antopolski B, Helft M, KafIe I. Comparison of methods ofclinical evaluation of the marginal fit of complete cast crowns. J PROS-THET DENT 1985;54:20-4.33. Rosenstiel E. To bevel or not to bevel? Br Dent J 1975;138:389-92.34. Metzler JC, Chandler HH. An evaluation of techniques for finishingmargins of gold inlays. J PROSTHET DENT 1976;36:523-31.35. Sarrett DC, Richeson JS, Smith GE. Scanning electron microscopyevaluation of four finishing techniques on margins of gold castings . JPROSTHET DENT 1983;50:784-92.36. Miller L. In: Dental ceramics. Proceedings of the First Interna tionalSymposium on Ceramics. Chicago: Quintessence Publishing Co,1983:X3,178,183.37. Finger W. Effect of thickness of peridental restorations on the castingprecision. Stand J Dent Res 1980,88:455-g.38. Erhlich J, Hochman N. Alterations on crown contour--effect on gingi-val health in man. J PROWHET DENT 1980;44:523-5.39. Parkinson CF, Schaberg TV. Pontic design of posterior fixed partialprostheses: is it a microbial misadventure? J PROBTHET DENT1984;51:51-4.40. Perel ML. Axial crown contours. J PROSTHET DENT 1971;25:642-9.

41. Yuodelis RA, Weaver JD, Sapkos S. Facial and lingual contours of ar-tificial complete crown restorations and their effects on the periodon-tium. J PROSTHET DENT 1973;29:61-6.42. Becker CM, Kaldahl WB. Current theories of crown contour, marginplacement and pontic design. J PROSTHET DENT 1981;45:268-77.43. Palomo F, Peden J. Periodontal considerations of restorative proce-dures. J PROSTHET DENT 1976;36:387-93.44. Karlsson S. A clinical evaluation of fixed bridges , 10 years following in-sertion. J Oral Rehabil 1986;13:423-32.45. Grasso JE, Nalbandian J, Sanford C, Balit H. The quality of restorativedental care. J PROSTHET DENT 1979;42:571-8.46. Grasso JE, Nalbandian J, Sanford C, Balit H. Effect of restorationquality on periodontal health. J PROSTHET DENT 1985;53:14-9.47. Parkinson CF. Excessive crown contours facilitate endemic plaqueniches. J PROSTHRT DENT 197&3 5:424-g.48. Comcowich W L. In: Dental ceramics. Proceedings of the First Interna-tional Symposium on Ceramics. Chicago: Quintessence Publishing Co,1983265.8.

49. Coornaert J, Adriaens P, De Boever J. Long-te rm clinical study of por-celain-fused-to-gold restorations. J PROSTHET DENT 1984;51:338-42.50. Walton JN, Gardiner FM, Agar JR. A survey of crown and fixed partialdenture failures: length of service and reasons for replacement. J PROS-THET DENT 1986;56:416-20.

51. Hobo S, Shillingburg HT. Porcelain-fused-tometab tooth preparationand coping design. J PROSTHET DENT 1973;30:28-35.52. Shillingburg HT, Hobo S, Fisher DW. Preparation design and margindistortion in porcelain-fused-to-metal restorations. J PROSTHETDENT1973;29:276-84.53. Faucher RR, Nicholls JI. Distortion related to margin design in proce-lain-fused-to-metal restorations. J PROSTHET DENT 1980;43:149-55.54. Wanserski DJ, Sobczak KP, Monaco JG, McGivney GP. An analysis ofmargin adaptation of all-porcelain facial margin ceramometal crowns.J PROSTHET DENT 1 986;56:289-92.55. Bridger DW , Nicholls JI. Distortion of ceramometal fixed partial den-tures during the firing cycle. J PR~~THET DENT 1981;45:507-14.

56. Buchanan WT, Svare CW, Turner KA. The effect of repeated firings andstrength on marginal distortion in two ceramometal systems. J PROS-THET DENT 1981;45:502-6.57. Henry PJ. Pontic form in fixed partial dentures. Au& Dent J 1971;16:l-7.58. Goldstein RE. Esthetic principles for ceramometal restorations. DentClin North Am 1977;21:802-22.59. Panno FV, Vahidi F, Gulker I, Ghalili KM. Evaluation of the 45-degreelabial bevel with a shoulder preparation. J PROSTHRT DENT 1986;561655-61.

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