Delayed versus immediate loading of implants: survival analysis and risk factors for dental implant failure

Abstract

Purpose: The 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 methods: This 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 <or= .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 <or= .05 was considered statistically significant.

Results: The 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 <or= .05).

Conclusion: In this study, implants loaded immediately were 2.7 times (after adjusting) more likely to fail at 1 year compared with delayed-loaded implants.

Figure 1. Image depicting well-size measurement

Well-size was measured as the diameter at the occlusal extent of the implant, to which the diameter of the abutment was adapted. Well-size was not necessarily consistent with implant diameter.