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

This study evaluated the marginal and internal adaptation of Procera copings using different tooth preparations. The variations comprised 4 finish line forms, 3 occlusal forms, 3 occlusocervical undulation forms to the proximal finish line, and 3 proximal auxiliary retention forms.

One hundred twenty preparations were made and copings were fabricated, cemented, embedded in an epoxy resin, sectioned, and measured at 14 sites.

The feather-edge finish line had the highest mean external marginal opening (135 +/- 79 microns), compared with the chamfer finish line (64 +/- 38 microns), the 0.8-mm rounded shoulder (51 +/- 34 microns), and the 0.5-mm rounded shoulder (68 +/- 56 microns). All 3 forms of occlusal reduction produced comparable internal adaptation at the axial wall. Specimens with normal occlusal reduction had the best occlusal adaptation at the cusp tip but not to a statistically different degree from the exaggerated form. Variations in the vertical height of interproximal finish lines did not significantly affect marginal opening. However, proximal retentive features less than 2.5 mm wide and more than 0.5 mm deep cannot be accurately reproduced with the present Procera scanner tip.

Feather-edge finish-line forms, deep retentive grooves, and deep occlusal morphology are not well reproduced using this system, but all other finish-line forms and design variations are accurately and clinically acceptably reproduced using this system.