Risk factors and outcomes of consecutive dental implant replacements at failed sites: a retrospective cohort study

Reimplantation of dental implants at sites of prior failure remains a clinical challenge with variably reported success rates. This retrospective study evaluated the clinical outcomes of consecutive implant reimplantations at previously failed sites and analyzed associated risk factors for re-failure.

Records of 5,201 dental implants placed from 2017 to 2021 were reviewed. A total of 203 implants failed (initial failure rate 3.9%), and 189 of these sites underwent reimplantation. Clinical variables included age, gender, smoking, hypertension, diabetes mellitus, antithrombotic medication use (particularly ASA), bone grafting, implant location, timing of failure, and patient willingness to continue treatment. Statistical analyses included chi-square and Fisher's exact tests for group comparisons, independent-samples t-tests for continuous variables, and univariate logistic regression for risk factor assessment. Analyses were descriptive and based on proportions and univariate logistic regression; time-to-event methods were not applied, and results should be interpreted as exploratory.

Survival was 96.1% for initial implants (4,998/5,201), 78.8% (149/189) for first reimplantations, and 51.5% (17/33) for second reimplantations (χ² for trend, p < 0.001). Older patient age was significantly associated with failure across all stages. Hypertension (7.1% vs. 2.6%; p < 0.001) and diabetes mellitus (8.2% vs. 2.8%; p < 0.001) were significantly associated with initial implant failure but not with reimplantation outcomes. Prior bone grafting increased failure risk during initial placement (7.2% vs. 3.4%; p < 0.001) but showed no significant effect in reimplantations. ASA use significantly reduced the risk of failure during the first reimplantation (OR = 0.42; 95% CI: 0.21-0.87; p = 0.020). Smoking and implant location (mandible vs. maxilla) were not statistically significant predictors at any stage. Patient willingness to undergo further treatment declined after consecutive failures (93.1% after initial failure vs. 82.5% after second failure; χ²=3.51, p = 0.061; Fisher p = 0.057).

Implant survival decreased with each reimplantation attempt, with markedly reduced outcomes in the second reimplantation cohort. Older age, diabetes, hypertension, and prior grafting were associated with initial failure, whereas ASA use appeared protective during first reimplantation. Given the descriptive and unadjusted nature of our analyses, these findings should be viewed as hypothesis-generating and require confirmation in prospective, multicenter studies using time-to-event and adjusted models.