Influence of re-cementation on the retention of CAD/CAM zirconia copings over short titanium and zirconia abutments

Abstract

Objective: The aim of this study was to comparatively evaluate the effects of re-cementation on the retention of zirconia copings, which were cemented to short titanium and zirconia abutments with self-adhesive resin cement. Materials and Method: Twelve titanium (Nucleoss T4 implants, NucleOSS T4 flat abutment, İzmir, Turkey) and 12 zirconia abutments (Zirkonzahn, Zirkonzahn GmbH, Bruneck, Italy) were used in this in vitro study. The titanium abutments were shortened to 3 mm and embedded in acrylic by fixing them with analogues. The zirconia abutments and copings were produced by scanning the abutments using the computer-aided design and manufacturing (CAD/CAM) method. All zirconia copings were cemented to the titanium and zirconia abutments with self-adhesive resin cement. Samples were subjected to a pull-out test in a universal testing device, and the bond strength values were recorded. Cement residues on the abutments and copings were removed with a handpiece that had a round head carbon steel bur, and an explorer. The copings were then re-cemented and retested using the pull-out test, and the strength values were recorded. Descriptive statistics were applied to the data, and the mean and standard deviation values were calculated. Bonferroni corrections with pairwise comparisons were used to compare the group and test effect at each level. P<0.01 was considered as statistically significant. Results: The effect of the pre-test and end-test on bond strength (p<0.001), the group effect on titanium and zirconia (p<0.001) and the test-group interaction effect (p<0.001) were all found to be statistically significant. A significant difference was observed between the titanium and zirconia samples in terms of bond strength when the pre-test and end-tests were compared (titanium: p<0.05, zirconia: p<0.001). The end-test bond strength values were significantly lower than the pre-test bond strength values. Additionally, there was a significant difference between the titanium and zirconia samples in terms of bond strength change on comparison of the pre-test and the end-test. Decrease in bond strength values was higher in the zirconia samples (p<0.001). Conclusion: Re-cementation may adversely affect the bond strength of single-unit restorations on short abutments. In the case of re-cementation, a higher retention loss may occur in zirconia abutments than in titanium abutments.