At which bone level are implants explanted

OBJECTIVES: Clear guidelines when to remove an implant are missing. The aim of this study was to evaluate the amount of peri-implant bone loss at explantation by specialists. MATERIAL AND METHODS: Implantology specialists were asked to provide implants explanted due to peri-implantitis with related clinical information. Early failures (survival time < 12 months) were analysed separately. Questionnaires inquired age, sex, smoking, implant location, usage of bone substitutes and implant brand. Explants were measured and bone loss was assessed using radiographs. Covariate-adjusted mixed-effects models were evaluated for bone loss and survival time. RESULTS: Twelve dental offices provided 192 explants from 161 patients with 99 related radiographs. Thirty-three (17.2%) explants were early failures. Excluding early failures, average survival time was 9.5 ± 5.8 years with absolute and relative bone loss of 7.0 ± 2.7mm and 66.2 ± 23.7%, respectively. Late failures were removed at mean bone loss of 57.7% in the maxilla and 73.7% in the mandible irrespective of survival time. In fully adjusted mixed-effects models, only age at implantation (B=-0.19; 95% CI: -0.27, -0.10) remained a significant factor for survival time. Implants exhibited significantly more relative bone loss if they were positioned in the mandible (B=17.3; 95% CI: 3.91, 30.72) or if they were shorter (B=-2.79; 95% CI: -5.50, -0.08). CONCLUSIONS: Though the mean bone loss (66.2%) at which implants were explanted was in accordance with the literature, its wide variation and differentiation between jaws showed that the profession has no universally accepted threshold beyond which an implant cannot be preserved.