All-ceramic, bi-layered crowns supported by zirconia implants: Three-year results of a prospective multicenter study.

OBJECTIVES: To determine the clinical and patient-reported outcomes of bi-layered, all-ceramic posterior single crowns (SCs) supported by zirconia implants in an uncontrolled, prospective, multicenter study.

METHODS: In two centers, 60 patients received 71 one-piece zirconia oral implants to be restored with either SCs (n=49) or three-unit fixed dental prostheses (n=11). Of these patients, 45 implants were restored with all-ceramic, zirconia-based posterior SCs (one per patient). Survival rates of implants and reconstructions were assessed, and technical success was evaluated according to modified U.S. Public Health Service (USPHS) criteria. Furthermore, patient-reported outcome measures (PROMs) were assessed by applying visual analog scales (VAS). Kaplan-Meier (KM) plots and log-rank tests were used for success/survival analyses. The Wilcoxon matched-pairs signed-rank test was used to evaluate time effects on response variables (PROMs, USPHS criteria).

RESULTS: Forty patients with 40 SCs could be evaluated after 36.7±1.2months. No SC was replaced, resulting in 100% survival. The KM success estimate was 87.5% (two chippings, one restoration margin, and one contour were rated Charlie). In general, the incidence of chipping (p=.0005) and occlusal roughness (p=.0003) was frequent. Compared with the pre-treatment patient surveys (67-93%), all surveys at prosthetic delivery except for speech (p=.139) showed significantly improved VAS scores (81-94%; p<.0001). Thereafter, no decrease in satisfaction could be observed over time until the 3-year follow-up (86-93%; p≥.390).

CONCLUSION: Veneered, zirconia-based SCs supported by zirconia implants satisfied patients' needs highly. However, significant incidence of chipping and roughness of the veneering ceramic may compromise the clinical long-term outcome for this indication.

CLINICAL SIGNIFICANCE: Posterior, zirconia-based SCs supported by zirconia oral implants entirely survived the follow-up period of 3 years, but two major chippings, one a significant marginal opening and one pronounced over-contouring, resulted in a reduced KM success estimate of 87.5% after 36 months of observation.