Characteristics of the inflammatory process around skin-penetrating titanium implants for aural rehabilitation.

Skin-penetrating titanium implants have been used to anchor bone-anchored hearing aids (BAHAs) since 1977. The aim of the present immunohistochemical study was to analyse the distribution of inflammatory cell types in the skin penetration site with a panel of monoclonal antibodies. Many inflammatory cells were present at the tissue-implant interface but decreased gradually in number from the interface. The predominating cell types in the dermis in clinically non-inflamed tissue were T lymphocytes and macrophages, indicating a chronic inflammatory response. In specimens from clinically inflamed tissue, a large number of polymorphonuclear positive cells were present. B lymphocytes and plasma cells were also found, indicating that bacterial infections were superimposed on the chronic inflammatory response. An additional aim was to revise the clinical scoring system based on the present findings and earlier histological results.