Comparing Retention and Internal Adaptation of Different Implant-Supported, Metal-Free Frameworks

Purpose: This study was conducted to compare the fit and retention of implant-supported, metal-free copings fabricated from zirconia, polyetheretherketone (PEEK), or composite, as well as to evaluate the possible correlation between internal adaptation and retention. Materials and Methods: A total of 36 copings were milled from zirconia, PEEK, or composite blanks (n = 12 in each group). Marginal and internal gap were evaluated by replica technique, and the pull-out test was used to evaluate retention. One-way analysis of variance, post hoc Tukey tests, and Pearson correlation coefficient test were used to analyze the data. Results: Zirconia had significantly better marginal/internal adaptation (P .05) than the other materials. There was no statistically significant difference in mean retention force between the different groups (P > .05). No correlation was found between internal adaptation and retention. Conclusion: In the metal-free copings tested, zirconia showed the best adaptation. The retention of copings was not influenced by internal fit or material type.