Precision of fit of two margin designs for metal-ceramic crowns: Basic science research

Statement of Problem: Although metal-ceramic restorations are widely used, there is a lack of information about how the fit is affected by margin designs. Purpose: This study measured and compared the precision of fit of metal-ceramic crowns with two margin designs. Material and Methods: Thirty-two extracted human premolar teeth were prepared for complete-coverage restorations with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with improved stone type V. MC crowns were fabricated with a porcelain-butt margin on the buccal aspect (n = 32) and a feather-edge metal margin on the lingual aspect (n = 32), which served as a control group. Precision of fit was measured three times at the mid-buccal and mid-lingual margins of each crown with a profilometer. The data were statistically analyzed with the paired t-test (α <.05). Results: Mean marginal gap size of porcelain-butt margins was 27.93 μm (±15.84) and of feather-edge metal margins 42.43 μm (±24.12). The marginal gap size of feather-edge metal margins was statistically significantly greater than that of porcelain-butt margins (p = 0.0045). Conclusion: The marginal fit of porcelain-butt margins was significantly better than that of feather-edge metal margins. Clinical Implications: Porcelain-butt margins in this study had a better marginal fit than feather-edge metal margins, and thus have given clinicians evidence to prefer the use of porcelain-butt margins.