Marginal and Internal Adaptation of Zirconium Dioxide Ceramic Copings and Crowns with Different Finish Line Designs

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The present study evaluated the marginal and internal adaptation of single-tooth zirconium dioxide (ZrO_2) ceramic copings or crowns with three different finish line designs. Twenty-four steel dies were prepared for maxillary central incisor crowns with the following finish line designs : shoulder (S), rounded shoulder (RS), and chamfer (C) preparations. Twenty-four standardized ZrO_2 ceramic copings were manufactured with a CAD/CAM system (Cercon Smart Ceramics), and the crowns were finalized by veneering with a feldspathic ceramic. Measurements for marginal and internal adaptation were performed at two stages : the copings and the completed crowns. No significant differences were observed between the three groups in terms of marginal discrepancy median value : S, 73/69 ; RS, 61/60 ; C, 64/55 (μm). However, significant differences in internal adaptation were widely found among all groups : S, 117/111 ; RS, 72/75 ; C, 56/57 (μm). As for intra-group comparisons of marginal and internal adaptation values for all groups, the differences were not significant. It was found that the finish line design seemingly wielded no influence on marginal adaptation of single-tooth ZrO_2 ceramic copings and crowns. It was also observed that the marginal and internal adaptation values in the present study were all within the clinically acceptable range.