Three-Year Results of a Randomized Controlled Clinical Trial Using Submucosally Veneered and Unveneered Zirconia Abutments Supporting All-Ceramic Single-Implant Crowns

This study aimed at evaluating the influence of veneering of the submucosal part of zirconia abutments on biologic, radiographic, technical, and esthetic outcomes in single-tooth implant sites. A total of 20 patients each received a zirconia abutment to support an all-ceramic implant-supported crown. Patients were randomly assigned to the test group (n = 10), in which the abutment was modified with pink veneering ceramic, or to a control group (n = 10) without further submucosal customization. Patients were followed up at baseline (after the insertion of the final reconstruction) and yearly thereafter. Wilcoxon-Mann-Whitney test was used to evaluate the difference between the medians of the two groups, whereas Wilcoxon signed rank test allowed calculation of the differences per group. At 3 years, 18 patients could be recalled. The survival rates reached 100% (implant level) and 95% (restorative level). Two implant crowns experienced minor chipping, one in each group. No significant intergroup differences were observed regarding mucosa thickness between the groups. The width of keratinized tissue did not change significantly over time in either group. The radiographic evaluation showed no significant differences regarding the marginal bone level at any timepoint between the groups. Changes over time reached -0.27 mm (SD 0.41, median −0.26) for the test group and -0.21 mm (SD 0.30, median −0.31) for the control group. Statistical significance was not reached within or between the groups. Veneering of the submucosal part of zirconia abutments did not significantly influence biologic and technical outcomes in single-tooth implant sites up to 3 years.