IMMUNOHISTOCHEMISTRY OF SOFT-TISSUES SURROUNDING LATE FAILURES OF BRANEMARK IMPLANTS

The objective of the present investigation was to characterize the cel lular composition of the soft tissues surrounding consecutively retrie ved late failures of Branemark implants. Criteria for implant failure were signs of loss of osseointegration (radiographic peri-fixtural rad iolucency and mobility). The clinical history of the implants did not include adverse symptoms. At the time of retrieval, percussion-induced pain was experienced at 4/8 implants, but no macroscopical signs of i nflammation or infection was observed, Immunohistochemistry was applie d on 6 marginal peri-implant specimens and on specimens of deeper tiss ues associated with the previously load-bearing implant surface from 8 failed implants, whereas 6 clinically healthy mucosal specimens and 4 hyperplastic biopsies from stable implants served as controls. The im munohistochemical evaluation showed that the soft tissues surrounding failed implants contained a large number of macrophages (CD68), HLA-DR positive cells, lymphocytes and plasma cells preferentially accumulat ed towards the removed implant surface. PMNs were a rare finding. Down growth of epithelium, in some cases encapsulating the whole fixture, w as observed in sections where an intact implant/soft tissue interface was preserved. Healthy control mucosal specimens always contained labe lled cells, albeit in a low amount, whereas hyperplastic control sampl es displayed an intense inflammatory and immunological response with n umerous positive cells and PMNs scattered throughout the biopsy, In co nclusion, failed implants were characterized by a chronic inflammatory response of the surrounding tissues with macrophages as the predomina nt labelled cell type, while hyperplastic tissues around stable Implan ts were distinguished by an acute inflammatory process, These findings suggest that an on-going infection is unlikely to be the etiological factor for the late failures of dental implants examined in this study .