Abstract: Objective: To study the marginal and internal fit of all-ceramic crowns on three different tooth-colored post-cores. Methods: A total of 24 intact extracted teeth were selected and excised at 2mm crows from cemento-enamel junction. Eight of color-masking Co-Cr post-cores, zirconium post-cores, and fiber-resin post-cores were separately made according to the clinical operation procedures and methods. The marginal and internal fit of these groups were measured and recorded using a measuring microscope by silicone rubber gap impression. Statistical analysis was performed with SPSS 17.0 software. Results: The depths of marginal fit of the color-masking Co-Cr post-cores, zirconium post-cores, and fiber-resin post-cores were 96.98±3.51, 62.34±3.22, and 59.00±3.96μm, respectively. The depths of internal fit were 95.71±2.52, 73.14±2.04, and 68.52±4.08μm, respectively. A significant difference was observed in the marginal and internal fit of the color-masking Co-Cr post-cores and the other groups (P<0.05). No statistically significant difference was observed in the marginal and internal fit of the zirconium post-cores group and fiber- resin post group. Conclusion: The marginal fit of all ceramic crowns are clinically acceptable using three post-core methods. The marginal adaptation of zirconium post-cores and fiber-resin post-cores were more closed to America Dental Association standards.

Key words: Post-core, All-ceramic crown , Marginal and internal fit , CAD/CAM