Survival of Single-Tooth Implants in Sites With and Without History of External Cervical Root Resorption: A Register-Based Cohort Study

Purpose: To compare the survival of single-tooth implants placed in sites with a history of external cervical root resorption (ECRR) to those placed in unaffected sites. Methods: A retrospective matched cohort study was conducted using data from the Swedish National Dental Health Register (2009–2022). Patients receiving a single-tooth implant in a site with prior ECRR were identified and matched 1:1 to controls without such history by age, sex, tooth position, and timing of implant placement (± 2 years). Implant survival, defined as time from placement to removal, was analyzed using Kaplan–Meier curves and stratified Cox proportional hazards models. Restricted mean survival time (RMST) was estimated up to 10 years. Subgroup and sensitivity analyses assessed robustness. Results: The final cohort included 605 matched pairs (n = 1,210). The mean age was 52 years, and 56% of implants were placed in the maxillary anterior region. Implant extraction occurred in 12/571 (2.1%) ECRR sites and 21/564 (3.7%) control sites. Ten-year cumulative survival was 97.3% for ECRR sites and 94.4% for controls. The difference was not statistically significant (HR = 0.58; 95% CI: 0.28–1.22; p = 0.15). RMST analysis showed a negligible absolute survival difference (0.11 years; 95% CI: −0.04 to 0.25; p = 0.15). Conclusions: Single-tooth implants placed in sites with a history of ECRR demonstrated survival outcomes comparable to implants in unaffected sites. Prior ECRR does not appear to compromise implant prognosis.