Histological evaluation of different abutments in the posterior maxilla and mandible: an experimental study in humans

Objectives To histologically evaluate and compare the performance of healing abutments with either hydrophobic or hydrophilic surface properties in humans. Materials and Methods According to a parallel-group design, titanium implants placed in the posterior mandible and maxilla of 30 patients were randomly assigned to either (1) hydrophobic machined (M), (2) chemically modified hydrophilic (mod) acid etched (MA) titanium (Ti) (modMA1) or (3) modMA Ti- Zirconium alloy (modMA2) healing abutments and left to heal in a transmucosal position. At 8 weeks, the abutments and a limited soft tissue biopsy were harvested according to a standardized procedure and processed for histological analysis (primary outcomes: percentage epithelial- (EC) and subepithelial connective tissue contact (CTC) to the abutment surface). Results The surgical procedure was associated with an incomplete mucosal coverage of the study abutments in nine patients, and an unintentional submerged healing procedure in three patients. Per protocol analysis (18 patients) has pointed to an improved quantitative EC [modMA2 (53.45 ± 28.25) > modMA1 (32.25 ± 24.3) > M (23.15 ± 16.09)] and CTC [modMA2 (75.12 ± 43.22) > modMA1 (69.41 ± 46.74) > M (47.63 ± 19.28)] (%) to modMA surfaced abutments. Conclusions It was concluded that modMA surfaces may have the potential to enhance soft tissue adhesion at the transmucosal aspect of titanium dental implants.