Evaluating the effect of a sloping shoulder and a shoulder bevel on the marginal integrity of porcelain-fused-to-metal (PFM) veneer crowns.

AIM A porcelain-fused-to-metal (PFM) veneer crown restoration is considered successful when biological, mechanical, and esthetical concerns are satisfied. Restorations with poor marginal integrity may contribute to the cause of severe caries and periodontal defects. The most important factor in achieving successful marginal integrity is preparation design. Although a sloping shoulder preparation offers biologic and esthetic advantages over a shoulder bevel, a comparison of the marginal integrity of these two designs is less clear and is the main focus of this study. METHODS AND MATERIALS This study was based on the analysis of 40 PFM veneer specimens fabricated on 20 stone dies. Each die had a beveled shoulder on one side of the preparation and a sloping shoulder design on the other. All specimens were selected and managed in an identical manner throughout the entire experimental process. All specimens were fabricated on stone dies made from a standard stainless steel die with the two shoulder designs in the preparation. Marginal integrity of the PFM veneers was evaluated using a scanning electron microscope to measure the gap between the restoration and tooth margin. The data were analyzed using the Student t-test at a significance level of p>0.05. RESULTS An average amount of gap (+/- SD) for the test groups were as follows: shoulder bevel, 40.78+/-18.4 microns; sloping shoulder, 52.8+/-27.4 microns (p>0.05). All the data were within acceptable clinical range and no significant difference between two preparation designs were observed. CONCLUSIONS Within the limitations of this study the marginal integrity of both preparation designs were found to be similar. Since the sloping shoulder design offers biological and esthetical advantages over the shoulder bevel, its use is indicated for anterior restorations.