Objectives: This in vitro study evaluated the marginal adaptation and fracture strength of ceromer/ FRC crowns with respect to the various types of finish lines for determining the ideal preparation method for applying this prosthesis. Methods: Four metal dies with different finish lines (0.9 mm chamfer, 1.2 mm chamfer, 1.2 mm rounded shoulder, 1.2 mm shoulder) were prepared. A total of 40 (10 for each group) Targis/Vectris crowns were fabricated on the NPG alloy die. The margin adaptations were evaluated at 56 points with a stereomicroscope before and after cementation. The specimens were compressively loaded to failure using a universal testing machine. The marginal adaptation was analyzed with Kruskal-Wallis test and post-hoc Dunnett test. The fracture strength was analyzed with ANOVA and Scheffe adjustment at the 95% significance level. The fracture surfaces of the crowns were examined with a SEM to determine the mode of fracture. Results: The marginal adaptation of the crowns with the shoulder finish line were better than those of the chamfer finish line. The marginal increase during cementation was the lowest in the 1.2 mm rounded shoulder. The fracture strength of the crowns with the 0.9 mm chamfer and the crowns with the 1.2 mm chamfer were significantly greater than those of the crowns with the 1.2 mm shoulder and a rounded shoulder. The mean fracture strength of all the crowns was 1646 N. The fracture surface of the crown revealed 4 types; Targis breakage from the interface, breakage of the Targis and Vectris, Targis breakage with a crack in the Vectris layer, and crushing without fracture. Conclusion: The marginal gaps were greater in the chamfer finish line than in the shoulder finish line. However, the fracture strength of the chamfer finish line was greater than that of the shoulder finish line.

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