Prior Tooth Mobility and Furcation Involvement Are Associated With Higher Dental Implant Failure Rates: A Propensity-Matched Cohort Study

Objectives: To compare the long-term survival of dental implants placed in sites with a documented pre-operative history of severe tooth mobility or advanced furcation involvement against a matched control group. Material and Methods: This retrospective cohort study analyzed patient records from a multi-university network. Implants were categorized based on the pre-extraction site history: Mobility Class (M2), Mobility Class (M3), Furcation Grade (G3), Furcation Grade (G4), and a control group. A 1:4 propensity score matching (PSM) was performed to balance baseline covariates (age, sex, smoking, diabetes, implant arch). Results: After PSM, a balanced cohort of 3925 implants (785 risk implants, 3140 control implants) was analyzed. The 10-year survival probability for the matched control group was 98.9%. All risk groups demonstrated significantly lower survival, with M2 at 94.6% and G4 at 95.5%. The adjusted multilevel Cox model confirmed a significantly higher risk of failure for all exposure groups. The adjusted hazard ratio was 2.3 for M2 (95% CI: 1.2–4.4), 3.8 for M3 (95% CI: 1.9–7.5), 3.0 for G3 (95% CI: 1.4–6.5), and 4.5 for G4 (95% CI: 2.1–9.8), compared to the matched controls (all p < 0.01). Conclusions: A pre-extraction history of severe tooth mobility or advanced furcation involvement at an implant site is significantly associated with long-term implant failure. Rather than being independent biological causes, these clinical signs likely serve as historical markers for severe localized bone loss and heightened periodontitis susceptibility and should be carefully considered during risk assessment and treatment planning.