Delayed Versus Immediate Loading of Implants: Survival Analysis and Risk Factors for Dental Implant Failure

PurposeThe purpose of this study was to estimate 1-year survival for delayed versus immediately loaded implants and identify risk factors for implant failure.Materials and MethodsThis was a retrospective cohort study, consisting of a sample of subjects who had greater than or equal to 1 Bicon dental implant (Bicon, Boston, MA) placed over a 13-year period. The primary predictor variable was method of implant loading: delayed (3 to 6 months after placement) or immediately after insertion. Secondary predictor variables were classified as demographic, anatomic, implant/abutment, and reconstructive. The outcome variable was implant failure, defined as removal of the implant, and was recorded as months of survival. Descriptive, Kaplan-Meier, and univariate Cox proportional hazards statistics were computed. Univariate associations with P ≤ .15 and biologically relevant variables (eg, age, gender) were included in a marginal multiple Cox regression model. In the multiple model, a P value of ≤ .05 was considered statistically significant.ResultsThe study sample consisted of 677 subjects who had 2,349 delayed-loaded dental implants and 178 patients who had 477 immediate-loaded implants. The unadjusted 1-year survival estimates for the delayed and immediate loading groups were 95.5% and 90.3%, respectively (P < .01). In the marginal multiple Cox regression model, immediate loading, current tobacco use, maxillary implants, and shorter implants were associated with failure (P ≤ .05).ConclusionIn this study, implants loaded immediately were 2.7 times (after adjusting) more likely to fail at 1 year compared with delayed-loaded implants.