Risk factors for dental implant failure in vascularized bone flaps: a decade-long cohort study

This study aims to evaluate the survival of dental implants placed exclusively within vascularized osseous free flaps for oral cavity reconstruction and to identify key risk factors for implant failure. A retrospective cohort study was conducted on 105 patients who received 358 dental implants within fibula, scapula, or deep circumflex iliac artery free flaps at a single institution over a 10-year period. The primary outcome was implant failure, defined as removal for any reason. Statistical analysis employed multivariate mixed-effects Cox regression models to account for patient-level clustering and confounding variables, including adjuvant radiotherapy, jaw location, donor site, and smoking status. Kaplan-Meier analysis demonstrated cumulative implant survival rates of 93.4% at 1 year, 89.2% at 2 years, and 83.9% at 3 years following implant placement. Implant survival remained relatively stable thereafter. Multivariate analysis identified two significant independent risk factors for implant failure: exposure to adjuvant radiotherapy (hazard ratio (HR): 3.46, P = 0.009) and placement in a reconstructed maxilla compared to the mandible (HR: 3.00, P = 0.040). The most common causes of failure were infection/peri-implantitis (68.5%) and osteoradionecrosis. Donor site type and smoking status were not significantly associated with failure in the adjusted model. Dental implants placed in vascularized bone flaps provide a viable rehabilitation method, though failure rates are higher. Adjuvant radiotherapy and maxillary location are the most critical risk factors, increasing the hazard of failure by approximately 3.5- and 3-fold, respectively. These findings underscore the need for careful patient selection and tailored approaches in this complex population.