Eight-Year Clinical Performance of Cantilevered Zirconia Resin-Bonded Fixed Dental Prostheses: A Randomized Controlled Trial Evaluating the Effect of Nanostructured Alumina Coating.

OBJECTIVE To evaluate the clinical performance of cantilevered zirconia resin-bonded fixed dental prostheses (RBFDPs) pretreated with nanostructured alumina coating (NAC) as a non-invasive surface modification alternative to airborne-particle abrasion (APA).

MATERIALS AND METHODS In this prospective, randomized, controlled clinical trial, 57 patients requiring replacement of a maxillary or mandibular incisor received 64 zirconia RBFDPs, randomly assigned to APA (n = 32) or NAC (n = 32) groups. APA surfaces were air-abraded with 50-μm alumina, whereas NAC surfaces were coated with NAC. Restorations were further classified by pontic position. Retention and survival rates were analyzed using Kaplan-Meier and log-rank tests; patient-specific factors were assessed with Mann-Whitney U and Fisher's exact tests (α = 0.05). Debonded surfaces were examined under scanning electron microscopy.

RESULTS Over a mean observation period of 61.4 ± 22.1 months (range, 8.3-97.4 months), six debondings occurred, corresponding to an overall survival rate of 100% and retention rates of 88.4% for NAC and 89.1% for APA (p = 0.99), with no significant differences among pontic groups (p = 0.18). Failures were predominantly adhesive, characterized by partial coating delamination at the NAC-zirconia interface.

CONCLUSIONS NAC-pretreated zirconia RBFDPs achieved mid- to long-term retention comparable to APA and represent a minimally invasive, clinically reliable pretreatment alternative.

CLINICAL SIGNIFICANCE NAC provides a minimally invasive zirconia pretreatment, particularly for RBFDPs fabricated from damage-prone translucent zirconia, mitigating mechanical failures while maintaining long-term retention comparable to APA.