Comparison of marginal fit between all-porcelain margin versus alumina-supported margin on procera ^® alumina crowns

Purpose: Procera ^® Alumina crowns are widely used; however, the effect of crown margin design on marginal fit is unknown. This study measured and compared the precision of fit of Procera ^® Alumina crowns with two crown margin designs: all-porcelain versus alumina-supported margins. Materials and Methods: Sixteen noncarious extracted human premolars were prepared for Procera ^® Alumina crowns with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with type IV dental stone. The specimens were randomly divided into two groups. Procera ^® Alumina crowns were fabricated: eight crowns with circumferential porcelain-butt (all-porcelain) margins and eight crowns with coping (alumina-supported) margins (control). Precision of fit was measured at six points on each crown with a profilometer (profile projector). The data were statistically analyzed with an independent-samples t-test (α < 0.05). Results: The mean marginal gap size (μm) of coping margins was 68.07 ± 16.08 and of porcelain-butt margins was 101.29 ± 43.71. There was no statistically significant difference (p = 0.065) of the marginal gap size between coping margins and porcelain-butt margins. Conclusion: The results of this study demonstrate that there was no statistically significant difference in the marginal fit of coping and porcelain-butt margins. Both margin designs are within clinically acceptable ranges. Therefore, clinicians may choose to use a coping margin, as it is less labor intensive and requires less time for fabrication, unless there is a specific high esthetic need for a porcelain-butt margin.