Long-Term Performance of Bi-Layered Single Crowns Supported by Zirconia Implants: 7.5-Year Results of a Two-Center...

To evaluate the survival and success rates of veneered zirconia-based single crowns (SCs) supported by zirconia implants in posterior regions, along with patient-reported outcomes, over 7.5 years.

Forty-five patients received zirconia implant-supported posterior SCs (n = 45) composed of zirconia frameworks layered with a leucite-reinforced feldspathic ceramic. At 7.5 years, clinical parameters and technical complications were assessed. Technical success was determined according to modified United States Public Health Service (USPHS) criteria. Patient-reported outcome measures (PROs) were evaluated using visual analog scales (VAS). Wilcoxon matched-pairs signed-rank test, mixed-effects ordered logistic regression, and linear mixed models analyzed time-dependent effects.

Thirty SCs (n = 30) could be evaluated at the 7.5-year follow-up (mean: 92.1 ± 3.4 months). Kaplan-Meier survival for SCs was 97.5% [95% CI: 83.6%-99.6%]. Success dropped to 79.4% [63.0%-89.2%] due to reconstructions with major chipping (n = 3), occlusal roughness (n = 7), marginal crevice (n = 1), and over-contouring (n = 2). PROs showed significant improvements from pre-treatment to delivery (VAS scores: 93%-97%) and remained stable throughout the follow-up period.

Veneered zirconia-based SCs supported by zirconia implants in posterior sites demonstrated high survival rates and consistently met patients' functional and esthetic expectations. Despite these favorable outcomes, the considerable incidence of technical complications warrants further investigation through long-term clinical studies.

While veneered zirconia crowns offer favorable esthetics, their susceptibility to chipping in posterior regions suggests that monolithic alternatives may be preferable. Further research is needed to optimize material selection and minimize technical complications.