Host response to titanium dental implant placement evaluated in a human oral model

Background: Recent reports have questioned if metal sensitivity may arise from exposure to titanium. The objective of this study was to histologically evaluate non-perforated mucosa covering submerged maxillary titanium implants with regard to induced tissue reactions. Methods: Thirteen patients, 21 to 69 years of age, without previous implants were included. After initial examination, the bone crest areas destined for dental implant placement were exposed, and threaded external hex dental implants were inserted. Prior to wound closure, a full mucosal tissue slice was biopsied from the edge of the mucoperiosteal flap (baseline). The patients were monitored monthly for 6 months. At the abutment connection, biopsies were taken by a 6-mm punch, altogether yielding 26 specimens. Tissue reactions were analyzed by coded histometric analysis at four defined areas at increasing distance from the oral epithelium, including ratios of inflammatory cells (IC)/epithelial cells, IC/fibroblasts, and number of dense particles. Results: The stained sections portrayed gingival tissue with intact oral epithelium and connective tissue with variable accumulation of IC. Experimental biopsies demonstrated mineralized areas and dense particles of different sizes. Analysis of variance revealed a higher IC/fibroblast ratio for level 3 at baseline compared to level 3 at 6 months (P < 0.01). Furthermore, a significant decrease in IC/fibroblast ratio was observed between levels 2 and 3 and 2 and 4 at 6 months (P < 0.001). The connective tissue level facing the cover screw contained the highest number of dense particles (P < 0.01). Conclusions: Tissue sensitivity reactions to titanium implants were not disclosed. All 6-month biopsies contained dense particles that were most likely metals.