Introduction Peri-implantitis has a prevalence of 11-47%, involves destruction of peri-implant bone, and may lead to implant loss. A detailed understanding of the pathogenesis of peri-implantitis is lacking. The objective of this study was to develop a murine model of experimental peri-implantitis. Materials and Methods Machined, smooth surface screw-shaped titanium implants were placed in the healed alveolar bone of the left maxillary molars of C57BL/6J male mice, eight weeks after tooth extraction. Peri-implantitis was induced by securing silk ligatures around the head of the implant fixtures. Implant survival and peri-implant bone levels were analyzed by micro-computerized tomography (micro-CT) scans and histology twelve weeks after ligature placement. Results Implant survival was 60% (6/10) for implants with ligatures and 100% (8/8) for controls. Micro-CT revealed significantly greater bone loss around the implants that received ligatures and that survived as compared to controls. The radiographic findings were confirmed via histology and toluidine blue staining. Conclusions This study describes a murine model of experimental peri-implantitis around screw-shaped titanium implants placed in the edentulous alveolar bone. This model should be a useful tool to dissect pathogenic mechanisms of peri-implantitis and evaluate potential treatment interventions.

Introduction Dental implants are a vastly used treatment option for tooth replacement. Dental implants are however susceptible to inflammatory diseases such as peri-implant mucositis and peri-implantitis, which are highly prevalent and may lead to implant loss. Unfortunately, the understanding of the pathogenesis of peri-implant mucositis and peri-implantitis is fragmented and incomplete. Therefore, the availability of a reproducible animal model to study these inflammatory diseases would facilitate the dissection of their pathogenic mechanisms. The objective of this study is to propose a murine model of experimental peri-implant mucositis and peri-implantitis. Materials and Methods Screw-shaped titanium implants were placed in the upper healed edentulous alveolar ridges of C57BL/6J mice eight weeks after tooth extraction. Following four weeks of osseointegration, Porphyromonas gingivalis-lipolysaccharide (LPS) injections were delivered to the peri-implant soft tissues for six weeks. No-injections and vehicle injections were utilized as controls. Peri-implant mucositis and peri-implantitis were assessed clinically, radiographically (micro-CT) and histologically following LPS-treatment. Results LPS-injections resulted in a significant increase in soft tissue edema around the head of the implants as compared to the control groups. Micro-CT analysis revealed significantly greater bone loss in the LPS-treated implants. Histological analysis of the specimens demonstrated that the LPS-group had increased soft tissue vascularity, which harbored a dense mixed inflammatory cell infiltrate, and the bone exhibited noticeable osteoclast activity. Conclusion The induction of peri-implant mucositis and peri-implantitis in mice via localized delivery of bacterial LPS has been demonstrated. We anticipate that this model will contribute to the development of more effective preventive and therapeutic approaches for these two conditions.