Metal particles and tissue changes adjacent to miniplates. A retrieval study.

Peri-implant soft tissue and bone from 12 patients undergoing removal of stainless steel miniplates and screws after healing of jaw fractures were studied with regard to histomorphology and metal content. Three patients with titanium plates were also included. Light microscopy and scanning electron microscopy with energy-dispersive X-ray microanalysis were used. Non-osseous tissue adjacent to devices of both materials showed fibrosis, including areas of mild chronic inflammation. The cellular picture was dominated by fibroblasts with small aggregates of lymphocytes and scattered macrophages. A connective tissue collar was found between the bone tissue and the screws of both stainless steel and titanium. Bone formation was also evident adjacent to screws of both materials. Stainless steel or titanium particles 5-50 microns in diameter were found in both soft tissue and bone next to implants of their corresponding bulk material. The amount of metal impregnation varied between individual sections, and fewer particles were found in the bone specimens than in soft tissue. The mild inflammatory changes were not restricted to areas of metal impregnation.