Can monolithic zirconia frameworks in implant-supported cross-arch prostheses deliver reliable long-term outcomes?

Abstract

A retrospective cohort study assessing the mid-to-long-term outcomes and risk factors affecting the prosthetic success and survival of implant-supported cross-arch fixed dental prostheses (IFCDPs) with monolithic zirconia frameworks. Forty-seven patients received a total of 51 cross-arch prostheses (27 maxillary and 24 mandibular prostheses), supported by 302 implants. Comprehensive clinical and radiographic records were available over a follow-up period ranging from 5 to 13 years. A strict inclusion criteria ensured the use of screw-retained implants and monolithic zirconia frameworks fabricated using standardised CAD/CAM protocols, without cemented titanium bases. Exclusion criteria included systemic conditions affecting healing, bruxism, uncontrolled periodontitis, smoking, and significant health changes during the follow-up period. Descriptive statistics summarised implant and prosthesis outcomes, while complications were evaluated for peri-implantitis at an implant level and framework fractures at a prosthesis level. Peri-implantitis was identified through clinical signs, including bleeding on probing, suppuration, and radiographic evidence of bone loss. Prosthetic outcomes were classified using the modified USPHS criteria. Mixed-effects Cox regression models were applied to analyse risk factors. Hazard ratios were calculated for peri-implantitis and framework fractures, with statistical significance set at p < 0.05. The implant survival rate was 97.64%, with peri-implantitis observed in 27 implants, predominantly in the mandible, resulting in an overall implant success rate of 91.06%. Prosthesis survival was 82.35%, with nine framework fractures reported, eight of which occurred in mandibular prostheses. The mandible was identified as a significant risk factor for both framework fractures (HR = 11.64, p = 0.024) and peri-implantitis (HR = 10.88, p = 0.003). IFCDPs with monolithic zirconia-based frameworks exhibited favourable clinical outcomes over a 5–13-year period. However, mandibular prostheses were more prone to framework fractures and peri-implantitis, highlighting the need to consider mandibular flexure in prosthetic design to enhance long-term success and durability.