Crown

margin

design: A dental

Eugene M. Butel, D.D.S.,* Jerry C. Campbell, Peter M. DiFiore, D.D.S., M.S.***

school survey D.M.D., M.S.Ed.,**

and

Fort Bragg, N.C. A survey aR dental schools in the United States and Puerto Rico was conducted concerning ceramometal crown margin design. The crown margin designs taught most often were the flat shoulder, the 45-degree bevel shoulder, and the chamfer. (J PROSTIWTDENT~~~~;~~:~O~-S.)

I

n 1956, 13recker’ introduced the porcelain-metal restoration. Since then many articles have been written concerning the design of ceramometal crown margins.2-14 An important consideration in the fabrication of the ceramometal crown is margin design. There appears to be no The opinions or assertionscontained herein are the private views of the authors and Bpe not to be construed as official or as reflecting the views of the Department of the Army. *Major, U.S. Army, DC, Senior resident, Advanced Education Program-Cenernl Dentistry. **Lieuten~t Colonel, U.S. Army, DC; Chief, Fixed Prosthetics and Mentor, Advanced Education Program-General Dentistry. ***Lieutenant Colonel, U.S. Army, DC: Chief, Endodontics and Mentor, Advanced Education Program-General Dentistry. 10/l/22772

con~nsus on which margin designs are appropriate in any particular clinical situation.3l 11*12+is>I6 Some of the designs that have been used in tooth preparation for ceramometal crowns are flat shoulder (butt joint), chamfer, deep chamfer with bevel, 135-degree shoulder, flat shoulder with 45-degree bevel (bevel shoulder 45degrees), flat shoulder with 70- or 75- degree bevel, and knife-edge or shoulderless.3* I1912*I53l6 The margin designs considered to be most appropriate are all modifications of the shoulder and chamfer?? 11x12p15*I6 Christensen2 studied the marginal fit of gold inlay castings and determined that the minim& acceptable open margin was 39 pm. This value has been cited repeatedly as a clinically acceptable marginal discrepancy. Margin designs have received increased attention in re-

Fig. 1. Margin designs included in survey. A, Flat shoulder (butt-joint); B, chamfer; C, deep chamfer with bevel; D, 135-degree shoulder (long bevel, sloped shoulder) E, flat shoulder with 45-degree bevel (bevel shoulder, 45-degrees); F, flat shoulder with 70-degree bevel (beveled shoulder, 75 degrees); G, knife-edge (shoulderless). THE3OURNALO~

PROSTHETIC

DENTfSTRY

303

BUTEL,

CAMPBELL,

AND DIFIORE

Table I. Results of questionnaires No. of Responses*

MX ANT MIX POST MN ANT MN POST

A

71

7 (10%)

(Iii%, 15 (21%) 7 (11%)

10 (14%) 9 (13%) 10 (16%)

70 70 62

in each category

C

D

E

F

G

4 (6%) 9 (13%) 10 (14%)

11 (15%)

I? (24%)

3

0

(4%)

B

t&

responses

&,

8 (11%) .A& (8;)

H

fl%l

0 (3;) (2:) (3%)

Cl:%, 6 (3%)

2 (3%)

1 (1.5%)

11.51%)

0

0

(I;%,

Key to responses. A, Flat shoulder; B, chamfer; C, deep chamfer with bevel; D, 135degree shoulder; E, 45-degree bevel shoulder; F, 70- to 75degree bevel shoulder; G, knife-edge or shoulderless; H, other. MX ANT, Maxillary anterior teeth; MX POST, maxillary posterior teeth; MN ANT, mandibular anterior teeth; MN POST, mandibular posterior teeth. *Total number of responses is greater than number of schools surveyed because of multiple responses in some categories.

Table II. Results according to location in dental arch Maxillary anterior A. Flat shoulder E. 45-degreebevel shoulder D. 135degree shoulder B. Chamfer C. Deep chamfer with bevel F. IO- to ‘i°ree bevel shoulder H. Other Mandibular anterior E. 45-degreebevel shoulder A. Flat shoulder C. Deep chamfer with bevel D. 135-degree shoulder B. Chamfer F. 70- to 75-degree bevel shoulder G. Knife edge/ shoulderless H. Other

Maxillary posterior E. 45-degreebevel shoulder 24% A. Flat shoulder

38%

32% 16%

15%

B. Chamfer

14%

10%

C. Deep chamfer w/bevel D. 135-degree shoulder F. 70- to 75degree bevel shoulder H. Other

13%

6% 4% 3%

Mandibular posterior E. 45degree bevel shoulder 21% B. Chamfer 14% C. Deep chamfer with bevel 14% F. 70- to 75degree bevel shoulder 13% A. Flat shoulder 9% D. 135-degree shoulder 1.5%

26%

11% 11% 3%

34% 16% 16% 15% 11% 8%

1.5%

cent years. Minimal opening has been the objective for designing margins. Some margin designs are touted as withstanding the ceramometal crown fabrication procedure better than others. Some authors have concluded that combinations of shoulder and shoulder-bevel are the ceramometal margin design of choice, while others have found the shouider-bevel inferior to the chamfer?-srg

304

However, Richter-Snapp et al.1° found that marginal adaptation following firing was not dependent on margin design. In recent years the scanning electron microscope (SE&l) has been used to evaluate margin closure for ceramometal crowns made with various margin designs. Belser et al.rl showed that there were no significant differences among the 0.5 mm beveled metal-to-tooth margin, metal butt margins with porcelain placed within 0.2 mm of the margin, or porcelain butt margins either before or after cemen~tion. Cooney et al.r2 studied marginal fit of ceramic margins using different techniques of fabrication. SEM analysis of margins revealed ceramic margins formed with a platinum foil fit better than margins formed with the direct lift technique and gave a comparable fit to that obtained with metal marginsI Hamaguchi et a1.13concluded that no significant marginal distortion occurred during porcelain application in the four margin designs studied. That study indicated that regardless of marginal design, application of porcelain and firing do not mechanically distort the facial margin.r3 Omar,14in an SEM study, found a mean marginal opening of 11 + 4 prns for unveneered shoulder-bevel ceramometal restorations and one of 23 A 7 pm for veneered shoulder bevel ceramometal restorations. Facially butted porcelain ceramometal restorations showed a mean marginal opening of 33 k 8 pm. SEM studies show that there is not a significant difference in clinical acceptability among the different margin designs studied.11-14 With this wealth of information and controversy, it is apparent that there is no consensus about current margin designs for ceramometal crowns. Therefore this study determined which margin designs are currently being taught in dental schools.

METHODS

AND MATERIAL

A survey was sent to all dental schools in the United States and Puerto Rico. The margin designs that were in

FEBRUARY

1991

VOLUME

65

NUMBER

2

SURVEY

OF CROWN

MARGIN

DESIGN

the survey are illustrated in Fig. 1. Of the 59 dental schools surveyed, 51 responded.

RESULTS The results of the 51 questionnaires are listed in Table I. The results according to location in the dental arch are shown in Table II. The responses ranked in descending order by percentage are shown in Table II. The results of the dental school survey show that all designs listed in this article are currently taught. The flat shoulder and bevel shoulder are the ceramometal margin designs taught most frequently for maxillary and mandibular anterior and maxillary posterior teeth. The 45-degree bevel shoulder and the chamfer are most frequently taught for the mandibular posterior teeth.

The wealth of articles concerning ceramometal margin design indicates the controversy surrounding this subject. Repeated heating and cooling cycles and stresses induced by application of porcelain are thought to cause distortion of ceramometal restorations.*! 6 Investigation has focused on the margin designs most resistant to this distor6,1’& 14,15

One technique for evaluating ceramometal margins involves mapping the margins with various microscopic equipment and determining the degree of change in margin coordinates following heat cycling and porcelain application.9 With the advent of the SEM researchers are now able to more accurately measure the marginal opening from casts made from impressions of castings before and after cementation in the mouth.13 Although all margin designs considered are currently being taught, the flat shoulder, the 45degree bevel shoulder, and the deep chamfer with bevel are the most popular, The all-porcelain labial margin can be used successfully in locations where an exposed metal collar would not be acceptable. HowSever,recent articles have addressed the problem of fabrication of this type of margin. This margin design is gaining in popularity and, with the advent of better shoulder porcelains, may become commonly used. Justification for using any of the margin designs listed in this article, with the exception of the feather-edge, is well supported in the literature. The feather-edge margin design is not considered appropriate for ceramometal restorations.16 With proper technique, from chairside through laboratory fabrication to insertion, any of the margin designs listed can be used to achieve a clinically acceptable ceramometal restoration.

THE JOURNAL

OF IPROSTRRT~C

AND CONCLUSIONS

In the dental school survey the flat shoulder and 45-degree bevel shoulder ceramometal margin designs were most popular for maxillary and mandibular anterior and maxillary posterior teeth. The 45degree bevel shoulder and chamfer ceramome~l margin designs were most popular for mandibular posterior teeth. All margin designs listed in this survey, with the exception of the feather-edge, are currently being taught for ceramometal restorations. REFERENCES Brecker SC. Porcelain baked to gold-a new medium in prosthodontics. J PROSTHET DENT 1956;6:801-10. 2. Christensen GJ. Marginal fit of gold inlay castings. J PROSTHET DENT 1.

1966;16:297-305.

DISCUSSION

tion,%

SUMMARY

DENTISTRY

3. Faucher RR, Nicholls JI. Distortion related to margin design in porcelain-fused-to-metal restorations. J PROSTHET DEW 1980;43:149-55. 4. Hobo S, Shillinburg HT. Porcelain fused to metal: tooth preparation and coping design. J PROSTHET DENT 1973;30:28-35. 5. Preston JD. Rational approach to tooth preparation for ceramo-metal restorations. Dent Clin North Am 197~21:683-98~ 6. Shilhngburg HT. Hobo S, Fisher DW. Preparation design and margin distortion in porcelain-fused-to-metal restorations. J PROSTHET DENT 1973;29:276-84.

7. Sozio RB. The marginal aspect of the ceramo-metal restoration: the collarless ceramo-metal restoration. Dent Clin North Am 1977;21:787801. 8. Tjan AHL, Miller GD, Sarkissian R. Internal escape channel to improve the seating of full crowns with various marginal configurations: a follow-up study. J PROSTHET DENT 1985;53:759-63. 9. McLean JW, Wilson AD. Butt joint versus bevelled gold margin in metal-ceramic crowns. J Biomed Mater Res 1980;14:239-50. 10. Richter-Snapp K, Aquillo SA, Svare CW, Turner KA. Change in marginal fit as related to margin design, alloy type, and porcelain proximity in porcelain-fused-to-metal restorations. J PRWTHET DENT 1988;60: 435-s. 11. Belser UC, MacEntee MI, Richter WA. Fit of three porcelain-fused-tometal marginal designs in viva: a scanning electron microscope study. d PROSTHET DENT 1985;53:24-9. 12. Cooney JP, Richter WA, MacEntee MI. Evaluation of ceramic margins for metal-ceramic restorations. J PROSTHET DENT l985;54:1-5.

13. Hamaguehi H, Caccitore A, Tuelter VM. Marginal distortion of the porcelain-bonded-to-metal complete crown: an SEM study. J PROSTHET DENT 1982;47:146-53.

14. Omar R. Scanning electron microscopy of the marginal fit of ceramometal restorations with facially butted porcelain margins. J PROSTH~ DENT 1987;58:13-9. 15. Donovan T, Prince J. An analysis of margin configuration for metal-ceramic crowns. J PROSTHET DENT 1985;53:153-7. 16. Gardner FM. Margins of complete crowns-literature review. 3 PROSTHET DENT 198~4~3~-400. Reprint requests to: DR. EUGENE M. BUTEL 464TH MED DET (DS) APO NEW YORK, NY 09180

305

Crown margin design: a dental school survey.

A survey of dental schools in the United States and Puerto Rico was conducted concerning ceramometal crown margin design. The crown margin designs tau...
1MB Sizes 0 Downloads 0 Views