Evaluation of marginal adaptation of all-ceramic crowns and metal ceramic crowns F a r h a d V a h i d i , DMD, MSD, a E r w i n T. Egloff, DDS, MS, b a n d F r a n c i s V. P a n n o , D D S c

New York University, College of Dentistry, New York, N.Y. The m a r g i n a l adaptation of R e n a i s s a n c e c r o w n s is c o m p a r e d w i t h that of the w i d e l y u s e d m e t a l c e r a m i c and Dicor crowns. This i n v e s t i g a t i o n s h o w s that Dicor and m e t a l c e r a m i c c r o w n s fit better than R e n a i s s a n c e crowns. Clinical i m p l i c a t i o n s of all three restorations are discussed. (J PROSTHET DENT 1991;66:426-31.)

E s t h e t i c dentistry is currently a main theme of dentistry and patients are interested in restorative materials which look and feel like natural teeth. The search for ideal materials to restore missing tooth structure has resulted in the availability of esthetically acceptable restorative materials such as glass-filled, resin-based composite resins, metal ceramic crowns, and other types of improved porcelain crowns such as Cerestore (Johnson &

Johnson Co., Windsor, N.J.; discontinued), Dicor (Dentsply International Inc., York, Pa.), and Renaissance (Williams Gold Refining Co., Inc., Buffalo, N.Y.). This investigation compared the marginal adaptation of Renaissance crowns with two widely used systems of metal ceramic crowns and castable ceramic crowns. METHODS



Presented before the Greater New York Academy of Prosth0dontics meeting, New York, N.Y. aAssociate Professor, Director of Occlusion, Department of Prosthodontics and Occlusion. bFormerly Assistant Professor, Department of Periodontics; private practice in Switzerland. cprofessor and Chairman, Department of Prosthodontics and Occlusion. 10/1/20548

Twenty-two recently extracted premolars were selected for the study. The teeth were prepared with a 360-degree shoulder 1 mm in width and 2 mm occlusal reduction (Figs. 1 and 2). Twelve teeth were selected for Renaissance crowns, five for Dicor crowns, and five were bevelled to receive metal ceramic crowns. These preparations had a 45degree bevel on the facial surface and an 80-degree bevel on the interproximal and lingual surfaces. The 45-degree bevel was created by use of a special diamond stone with

Fig. 1. SEM of shoulder preparation. (Original magnification X20.)

Fig. 2, SEM of shoulder preparation. (Original magnification ×100.)




Fig. 3. Section of Renaissance crown. (Original magnification x20.)

Fig. 4. Section of Dicor crown. (Original magnification x2o.)

a 45-degree cutting surface. The 80-degree bevel was cut with a flame-shaped steel plug finishing bur. 1 The extracted teeth were kept in moisture during the entire study. Die stone casts (Die Keen, Columbus Dental Mfg. Co., St. Louis, Mo.) of the prepared teeth were obtained from impressions made with reversible hydrocolloid. Two layers of die relief (Tru-Fit, G. Taub Products & Fusion Co., Inc., Jersey City, N.J.) were applied to the axial and occlusal surfaces of the dies for all the restorations. 2-4 The stone dies for Renaissance and metal ceramic crowns were sent to commercial laboratories, selected for their expertise in each system. The 45-degree bevel on metal ceramic preparations was waxed to a fine featheredge as described by Kuwata, 6 and the remaining 80-degree bevelled surfaces incorporated a reinforcing collar. Porcelain was baked to the gingival termination of the metal on the 45-degree surface. The Renaissance crowns were made according to the manufacturer's recommendation. However, this study used two layers of die relief instead of the manufacturer's die spacer. 2 Dicor crowns were made by the manufacturer (Dentsply International Inc.). The finished crowns were tried on the original preparations by the same operator (F. V.). Marginal adaptation of the crowns was studied by observation of impressions made with an elastic material (Coltene, Coltene Inc., Hudson, Mass.). The crowns were permanently cemented to the preparation with polycarboxylate cement (Durelon, Premier Dental Products Co., Norriston, Pa.) under constant finger pressure. The cemented crowns on the extracted teeth were embedded in hard resin (Chemco, San Leandro, Calif.) and then sectioned with a diamond saw (Buehler, Ltd., Lake Bluff, Ill.). The cut surfaces were polished to 600-grit fineness (Figs. 3 and 4).

can Optical, Buffalo, N.Y.) at the junction of the finishing line of the prepared tooth and the restoration. The sections for SEM examination were coated with a thin layer of carbon and examined in backscatter mode for easier evaluation of restorative materials. All of the electron micrographs (magnifications x20 and xl00) were obtained at 10 kV with a 35-degree tilt. The marginal characteristics of each crown were studied on the electron micrographs. Overcontouring and undercontouring of the different crown systems were not considered in this study (Figs. 5 through

M e a s u r e m e n t and o b s e r v a t i o n Specimens were examined under a light microscope at ×100 magnification. Cement thickness was measured with a linear occular micrometer (Micrometer 1406 A., Ameri-


12). RESULTS The measurements of the marginal opening (cement thickness) were made to a hundredth of a millimeter with a light microscope. Each section was measured at the facial and lingual surfaces. The Renaissance crowns demonstrated a mean cement thickness of 76 ttm. The marginal opening for the metal ceramic crowns (mean 37 ttm) was approximately half that of Renaissance crowns. Dicor crowns showed the lowest marginal opening, with an average of 30 ttm. The SEM examination in backscatter mode revealed porosity in the porcelain of both metal ceramic and Renaissance crowns. No such finding was made for the castable Dicor restorations. A considerable number of air bubbles was embedded in the cement of all of the specimens. Statistical analysis was by the two-tailed t-test. A statistically significant difference in cement thickness was found between Dicor and Renaissance crowns (p < 0.001). The metal ceramic crowns had significantly better margin adaptation than Renaissance crowns (p < 0.005). No statistically significant difference was found in marginal fit between Dicor and metal ceramic restorations.

DISCUSSION The results show that the margins of Dicor crowns are comparable to metal ceramic margins, supporting the



Fig. 5. SEM of sectioned cemented metal ceramic crown. Facial surface with 45-degree bevel. Porcelain added to gingival termination of metal. (P), Porcelain; (M), metal; (C), cement; (D) dentin. (Original magnification ×20.)

Fig. 7. SEM of sectioned cemented metal ceramic crown. Lingual surface with 80-degree bevel. (P), Porcelain; (M), metal; (C), cement; (D) dentin. (Original magnification x20.)

Fig. 6. Fig. 5 with ×100 magnification of margin.

Fig. 8. Fig. 7 with magnification of ×100 of margin.

findings of Holmes et al. s that there is no statistically significant difference between the margins of Dicor and type III gold crowns. Fig. 13 shows the marginal adaptation of a Dicor crown in our study compared with the outcome of other recent investigations. The finding of Davis 7 and Sorensen and Okamoto s are similar. Hung et al. 9 compared

the margin adaptation of Dicor, Cerestore, and metal ceramic crowns. They reported a greater marginal opening for these three restorations than did other investigators. Fig. 14 shows our results for the Renaissance crown in comparison with other studies. Sch~er et al. 1°, 11tested the marginal adaptation of two Renaissance crowns and found






Fig. 9. SEM of sectioned cemented Renaissance crown. (P), Porcelain; (F), foil coping; (C), cement; (D), dentin. (Original magnification ×20.)

Fig. 11. SEM of sectioned cemented Dicor crown. (P), Porcelain (castable ceramic); (C), cement; (D), dentin. (Original magnification ×100.)

Fig. 10. Fig. 9 with magnification of Xl00 of margin.

Fig. 12. SEM of another sectioned Dicor crown. (P), Porcelain; (C), cement, (D) dentin. (Original magnification

xlO0.) margin openings with a range of 19.8 to 41.5 #m. These authors developed a specific technique of swaging the foil whereas our study adhered to the manufacturer's recommendation and found a cement film thickness of 75.91 _+ 9.66 ttm for our 12 specimens. Meanwhile, Koerber and Ludwig 12have corrected some of the problems with the Renaissance foil and introduced the Ultralite foil. The new


design of this foil (five layers, no folds on the labial surface) appears to facilitate the technique-sensitive adaptation of the foil coping. The SEM examination of the ceramic materials led to an interesting observation. The electron micrographs of Re-



Marginal Opening of Crown in Microns 100

90 80 70 60

50 40 30 20 10 0







Holmes 1987

Vahldl 1988

Hung 1988

Scharer 1988

Fig. 13. Results of this study compared with other studies for Dicor crowns.

Marginal Opening of Crown in Microns 100

90 80 70 60

50 40

i iiiiii!! iliiiiiiii!

30 20 10 0

iT l__l , i Scharer Anterior Teeth-'87

Scharer Posterior Teeth-'87

Sorensen 1987

Vahidi 1988

Fig. 14. Results of this study compared with other studies for Renaissance crowns.

naissance restorations, and to a lesser extent metal ceramic crowns, showed porosities within the porcelain of the marginal surface. These irregularities were not detected on the Dicor specimens, which might explain the slow plaque accumulation and the favorable gingival response with Dicor crownsJ 3 A careful condensation of the porcelain and glazing of the cervical portion appear mandatory for maintenance of gingival health around metal ceramic crowns. The SEM study of these systems showed a horizontal marginal discrepancy in all ceramic crowns in addition to the vertical marginal opening (cement thickness).

recent developments. All three systems should be included as alternatives for restorative procedures since each system has its advantages and disadvantages. These are as follows: (1) Renaissance crown is indicated when less tooth reduction is advisable or internal characterization is necessary for an esthetically pleasing restoration; (2) Dicor crowns offer the advantages of translucency and radiopacity of natural teeth, excellent tissue response, good marginal seal, and can be used in partial coverage restorations; and (3) metal ceramic crowns have superiority for splinted multiple restorations and better retention and strength.

Clinical implications


The search for an ideal material continues and considerable improvements have been achieved with some of the

The marginal adaptation of 12 Renaissance crowns with Dicor and metal ceramic crowns was compared. A statisti-






cally significant difference was found in marginal adaptation between Dicor and metal ceramic crowns on the one hand and Renaissance crowns on the other hand. Dicor and metal ceramic crowns demonstrated a similar cement film thickness. An SEM examination was performed to evaluate the quality of the margin for each system. The advantages and indications of the three different designs for croWns were discussed: REFERENCES

1. PannoFV, VahidiF, GulkerI, GhaliliKM. Evaluationor the 45~degree labial bevel with a shoulder preparation. J PROSTHETDENT 1986; 56:655-61. 2. SorensenJA, Okamot0SK, MillerR, YaroveskyU. Marginalfidelityof four methods of Renaissancecrownfabrication[Abstract].J Dent Res 1987;66:283. 3. Eames WB, O'NealSJ, MonteiroJ, Miller C, Roan JD, Jr. CohenKS. Techniquesto improvethe seating of casting. J Am Dent Assoc 1978; 96:432-7. 4. GrajowerR, LewinsteinI. A mathematicaltreatise on the fit of crown castings. J PROSTHETDENT1983;49:663-74.

5. Kuwata M. GingNal margin design of abutments for ceramometal res~ toratlons. Quintessence Dent Technol 1979;10:19-23. 6. Holmes JR, Bayne S0, Sulik WD, Hiilland GA. Marginal fit of castable ceramic (Dicor) crowns [Abstract]. J Dent Res 1987;66:283. 7. Davis DR. Comparison of fit eftwo types of all-ceramic crowns. J PROSTHET DENT 1988;59:12-6. 8. Sorensen JA, Okamoto SK. Comparison of' marginal fit of all ceramic crown system [Abstract]. J Dent Res 1987;66:283. 9. Hung SH, Hung KS, Eick JD, Tira DE, Chappell RP. Marginal fit and microleakage of Dicor, Cerestore, and PFM crowns [Abstract]. J Dent Res 1988;67:377. i0. Schfirer P, Sato T, Wohlwend A. Marginal fit in the Ceraplation crown system. Quintessence Dent Technol 1987;1:11-25. 11. Schfirer P, Sat() T, Wohlwend A. A comparison of the marginal fit of three cast ceramic crown system. J PROSTHET DENT 1988;59:534-42. 12. Koerber KH, Ludwig K. Die faltenfreie Keraplatinfolie Ulite ~ Die Herstellungsfolge. Zahnaeztliche Wochen Rundscbau 1988;97:200-2. 13. Savitt ED, Malament KA, Socransky SS, Melcer AG, Backman KG. Effects on cokmization of oral microbiota by a cast glass ceramic restoration. J Periodont Rest Dent 1987;2:23-35.

Reprint requests to: DR. FARHADVAHIDI 265 EAST 64TH ST. NEW YORK, NY 10021

Film t h i c k n e s s of die c o a t i n g a g e n t s D. W. R i c h a r d s o n , D D S , a V. A. F l e t c h e r , D D S , b L. K. G a r d n e r , D D S , c a n d J. D. A l i e n , D D S d

Medical College of Georgia, School of Dentistry, Augusta, Ga., and University of Tennessee, School of Dentistry, Memphis, Tenn. Die coating agents are often used during the fabrication of porcelain m a r g i n s for c r o w n s and fixed partial dentures. T h e s e agents seal microscopic irregularities w i t h i n the stone die and resist abrasion. This i n v e s t i g a t i o n m e a s u r e d the film t h i c k n e s s of s e v e r a l die coating agents. A specific r e f e r e n c e point w a s used during the m e a s u r e m e n t process. The results indicate that there is no significant difference b e t w e e n the die coating agents e x a m i n e d under the conditions of the study. The film t h i c k n e s s m e a s u r e m e n t s ranged b e t w e e n 0.367 um for Duro s u p e r Glue Material and 2.3 #m for Zap CA material. (J PROSTHET DENT 1991;66:431-4.)

D u r i n g the fabrication of a porcelain margin for fixed partial dentures, cyanoacrylate resin is recommended to coat the die margins. 14 The coating aids in sealing microscopic irregularities in the stone surface as well as increasing abrasion resistance) The film thickness of cyanoacrylate resins on a flat die

aAssistant Professor, Department of Prosthodontics, Medical College of Georgia, School of Dentistry: bAssistant Professor, Department of Prosthodontics, University of Tennessee, School of Dentistry. CAssociate Professor, Department of Prosthodontics, Medical College of Georgia, School of Dentistry. dAssistant Professor, Department of Occlusion, Medical College of Georgia, School of Dentistry. 10/1/27925 THE JOURNAL OF PROSTHETIC DENTISTRY

stone surface was measured by Fukui et al. 5 In that study, die stone blocks were separated into 12 equal sections. Three cyanoacrylate resins were placed on sections of a stone block and were then either (1) blotted with a tissue, (2) subjected to a blast of compressed air, or (3) simply shaken off. Their study found no significant difference between the cyanoacrylate resins tested when the resins were either blotted with a tissue or were air blasted. The range of thickness was 0.97 to 1,5 #m. In the study by Fukui et al., 5 the surface of the die stone blocks on which the coating agents were placed was made by pouring stone into a smooth plastic mold. When measurements were made, these investigations assumed that the die stone surface was exactly the same height in all areas of the stone block. In an effort to improve the experimental method, a single point on the stone block should 43~

Evaluation of marginal adaptation of all-ceramic crowns and metal ceramic crowns.

The marginal adaptation of Renaissance crowns is compared with that of the widely used metal ceramic and Dicor crowns. This investigation shows that D...
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