The effect of tooth preparation form on the fit of procera copings

Purpose: This study evaluated the marginal and internal adaptation of Proce ra copings using different tooth preparations. The variations comprised 4 f inish line forms, 3 occlusal forms, 3 occlusocervical undulation forms to t he proximal finish line, and 3 proximal auxiliary retention forms. Material s and Methods: One hundred twenty preparations were made and copings were f abricated, cemented, embedded in an epoxy resin, sectioned, and measured at 14 sites. Results: The feather-edge finish line had the highest mean exter nal marginal opening (135 +/- 79 mu m), compared with the chamfer finish li ne (64 +/- 38 mu m), the 0.8-mm rounded shoulder (51 +/- 34 mu m), and the 0.5-mm rounded shoulder (68 +/- 56 mu m) All 3 forms of occlusal reduction produced comparable internal adaptation at the axial wall. Specimens with n ormal occlusal reduction had the best occlusal adaptation at the cusp tip b ut not to a statistically different degree from the exaggerated form. Varia tions in the vertical height of interproximal finish lines did not signific antly affect marginal opening. However, proximal retentive features less th an 2.5 mm wide and more than 0.5 mm deep cannot be accurately reproduced wi th the present Procera scanner tip. Conclusion: Feather-edge finish-fine fo rms, deep retentive grooves, and deep occlusal morphology are not well repr oduced using this system, but all other finish-line forms and design variat ions are accurately and clinically acceptably reproduced using this system.