Plaque-induced marginal tissue reactions of osseointegrated oral implants.
An intimate contact between bone and titanium implants was first demonstrated in 1969, and since then the bone-implant interface of osseointegrated implants has been investigated extensively. However, investigations of the marginal tissues and the microflora associated with osseointegrated implants have almost exclusively been carried out over the last decade. This review covers the clinical, radiographic, histologic, and microbiologic studies of marginal tissues of osseointegrated oral implants. In general, successfully osseointegrated implants exhibit low amounts of plaque concomitant with the absence of marginal inflammation. However, plaque accumulation may cause inflammatory reactions around the implants, sometimes giving rise to mucosal hyperplasia. Apparently, keratinized mucosa is not a requisite for the maintenance of peri-implant health if oral hygiene is adequate, but the presence of peri-implant keratinized mucosa is generally advocated. Alveolar bone loss around successful implants is minimal, but significant focal loss may occur due to plaque-induced inflammation or perhaps repeatedly extensive implant load. The progression of plaque-induced alveolar bone loss of osseointegrated implants may be different from that of teeth. It is unknown whether simultaneous marginal inflammation and excessive implant load further increase the loss of alveolar bone height. Both the light microscopic and ultrastructural characteristics of marginal tissues of implants and teeth are similar except for a lack of root cementum with inserting gingival collagen fibers of implants. Clinical inflammatory reactions are histologically characterized by an increased number of inflammatory cells infiltrating the connective tissue. The scattered subgingival microbiota associated with osseointegrated implants surrounded by healthy or slightly inflamed marginal tissues is similar to that of teeth with healthy gingiva. The microbiota associated with implants affected by marginal inflammation and bone loss is complex and consists predominantly of gram-negative anaerobic rods; this, again, is a similarity to periodontal disease.
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