The Impact of Posterior Occlusal Support Recovery by Dental Implant Treatment on the Survival of Remaining Teeth: A Long-Term Retrospective Study

<b>Background</b>: Preservation of posterior occlusal support is critical for maintaining residual dentition in partially edentulous patients. Although implant-supported restorations are widely used, long-term evidence on their role in preventing tooth loss remains limited. <b>Methods</b>: A retrospective cohort study of 225 patients (80 males, 145 females; mean age 53 ± 9 years) who received posterior implant-supported restorations, with a mean follow-up of 21 years. Post-treatment occlusal support was classified using the Eichner classification. Tooth and implant loss were recorded. Associations between residual occlusal support and tooth loss were analyzed using Pearson's chi-square test, with thresholds of ≥1, ≥2, or ≥3 teeth lost. Multivariate logistic regression analyses adjusted for age and gender were performed to evaluate the independent association of the Eichner classification. <b>Results</b>: After prosthesis delivery, 159 patients were classified as Eichner A, 48 as B1, 16 as B2, and 2 as B3. The mean number of lost teeth was 2.4, and 35 implants failed in 22 patients. Tooth loss ≥3 occurred more frequently in the Eichner B groups than in A. (48.5% vs. 34.0%). In multivariate analyses, Eichner classification significantly predicted loss of ≥3 teeth (adjusted OR = 1.83; 95% CI: 1.00-3.33; <i>p</i> = 0.048), but not ≥1 or ≥2 teeth. <b>Conclusions</b>: Posterior implant therapy provides durable occlusal support and contributes to long-term preservation of residual dentition. Patients with limited occlusal support remain at a higher risk of substantial tooth loss, even after adjustment for age and gender. The Eichner classification represents a practical clinical tool for evaluating occlusal support and predicting long-term prognosis in partially edentulous patients.