Histological characteristics of advanced peri-implantitis bone defects in humans

Background Inflammatory osteolysis is the clinical hallmark of peri-implantitis. The morphology of the remaining peri-implant bone and the level of osseointegration, however, remain unknown. Our aim was to characterize advanced peri-implantitis bone defects in humans. Methods Four patients (3 female and 1 male) were diagnosed with peri-implantitis. A total of 5 implants with machined surfaces and a mean loading time of 12 +/- 6 years were removed due to advanced bone loss. The defect extension, the peri-implant bone density (bone area per tissue area in percentage), bone-to-implant contact (%), and the number of filled and empty osteocyte lacunae were calculated based on undecalcified histological specimens. Results The defect extension was on average 4.2 mm (95% CI 0.8-3.4). Remaining peri-implant bone showed a high density of 85.5% (95% CI 79.1-91.3) and covered in total 74% (95% CI 70.5-77.5) of the implant surface. Filled and empty osteocyte lacunae density was on average 191 and 165/mm(2) (95% CI 132-251; 103-225), respectively. Histology further revealed signs of ongoing bone formation and resorption. Conclusion There are signs that suggest that once the original cortical bone is lost due to peri-implantitis, the remaining apical trabecular bone is reinforced and transformed into cortical bone that might take over the functional load.