Risk factors for proximal contact loss after implant-supported prosthetic restoration in adjacent natural teeth

Proximal contact loss (PCL) between implant-supported restorations and adjacent natural teeth is a frequent clinical complication, potentially leading to food impaction, caries, and periodontal issues. However, the risk factors contributing to PCL remain incompletely understood. This retrospective cohort study included patients who received single implant-supported crowns adjacent to natural teeth between June 2015 and June 2025. Eligible cases met stringent inclusion criteria based on radiographic, clinical, and periodontal assessments. PCL was diagnosed using floss resistance and radiographic separation tests, and quantified via calibrated shim stock measurements. Data on demographic, prosthetic, anatomical, and periodontal variables were extracted. Univariate and multivariate Cox proportional hazards regression analyses were used to identify independent predictors of PCL. A total of 206 patients (395 contact points) were included. The incidence of PCL was 67.5% at the patient level and 40.3% at the contact-point level. Multivariate analysis revealed that clinical food impaction (HR 2.75; 95% CI, 1.70–4.58; P < 0.001), residual ridge height discrepancy (HR 2.51; 95% CI, 1.37–4.58; P = 0.003), and advanced alveolar bone loss in adjacent teeth (HR 5.83; 95% CI, 1.05–32.33; P = 0.044) were independently associated with PCL. PCL is a prevalent complication following implant-supported prosthetic restoration. Local anatomical and prosthetic factors—particularly food impaction, ridge discrepancy, and bone loss—are key predictors. Proactive identification and management of these risk factors may help preserve interproximal contact integrity over time.