Purpose: Cellular fibronectin staining is decreased in adult periodontitis, which implies elastase-mediated degradation of periodontal tissues. The purpose of this study was to determine whether failing dental implants display similar changes. Materials and Methods: Cellular fibronectin and its integrin receptors were identified by immunohistochemistry and quantified by computerized image analysis. Results: Cellular fibronectin was found in blood vessel walls, epithelial basement membranes, and fibroblasts. Quantitative results of cellular fibronectin staining were as follows: failing dental implants, median 26.5% (Q3-Q1 = 23%); adult periodontitis, median 5.5% (Q3-Q1 = 5.6%); normal controls, median 12.2% (Q3-Q1 = 7.5%). Cellular fibronectin staining was increased around failing dental implants but decreased in adult periodontitis compared to healthy controls. Discussion: The distribution of integrin receptor subunits 4, 5, and 1 of cellular fibronectin was similar in failing dental implants. The pathomechanisms in adult periodontitis and failing dental implants seem to differ. Conclusions: Adult periodontitis is characterized by proteolysis/loss of cellular fibronectin, whereas failing dental implants are characterized by increased cellular fibronectin deposition, probably as a result of titanium-induced local synthesis and relatively modest degradation.