Resolution of peri-implantitis following treatment. An experimental study in the dog.

The aim of the present experiment was i) to study the effect of anti-microbial therapy of experimentally induced peri-implantitis lesions and ii) to assess features of bone regrowth following treatment. Four beagle dogs were used. Three titanium fixtures (Brånemark System) were installed in each quadrant of the mandible (premolars previously extracted). Abutment connection was performed 5 months later and ligature induced breakdown was initiated. The ligatures were removed when approximately 50% of the initial bone support was lost. A 3-week antibiotic regimen (amoxicillin and metronidazole) was initiated 1 month later. Two days after the start of the antibiotic administration, the experimental implant sites were exposed to local therapy. The abutments were removed and the exposed fixture surfaces were treated with an abrasive (pumice) administered via a rotating brush (left side) or cleaned with cotton pellets soaked in saline (right side). Cover screws were attached to the fixtures and the implants were submerged. Fluorochromes were injected intravenously 2 weeks, 4 weeks and 12 weeks after surgery. The animals were killed 7 months after surgery and block biopsies of each implant site were dissected and prepared for histological analysis. The findings of the examinations disclosed that the inflammatory lesion was resolved and new bone formation had occurred in the previous defect following antimicrobial and local therapy. The amount of "re-osseointegration" that had taken place, however, was small. Indeed, at all experimental implant sites, a thin connective tissue capsule was found to separate the implant surface from the newly formed bone.