Fit of single tooth zirconia copings: comparison between various manufacturing processes.

STATEMENT OF PROBLEM: Various CAD/CAM processes are commercially available to manufacture zirconia copings. Comparative data on their performance in terms of fit are needed. PURPOSE: The purpose of this in vitro study was to compare the internal and marginal fit of single tooth zirconia copings manufactured with a CAD/CAM process (Procera; Nobel Biocare) and a mechanized manufacturing process (Ceramill; Amann Girrbach). MATERIAL AND METHODS: Abutments (n=20) prepared in vivo for ceramic crowns served as a template for manufacturing both Procera and Ceramill zirconia copings. Copings were manufactured and cemented (Clearfil Esthetic Cement; Kuraray) on epoxy replicas of stone cast abutments. Specimens were sectioned. Nine measurements were performed for each coping. Over- and under-extended margins were evaluated. Comparisons between the 2 processes were performed with a generalized linear mixed model (alpha=.05). RESULTS: Internal gap values between Procera and Ceramill groups were not significantly different (P=.13). The mean marginal gap (SD) for Procera copings (51(50) mum) was significantly smaller than for Ceramill (81(66) mum) (P<.005). The percentages of over- and under-extended margins were 43% and 57% for Procera respectively, and 71% and 29% for Ceramill. CONCLUSIONS: Within the limitations of this in vitro study, the marginal fit of Procera copings was significantly better than that of Ceramill copings. Furthermore, Procera copings showed a smaller percentage of over-extended margins than did Ceramill copings