The role of bacterial biofilm and mechanical forces in modulating dental implant failures.

Currently many assume that bacteria are the primary etiological factor associated with failure of titanium dental implants. However, emerging data indicates a possible role for mechanical forces in implant failure. This study is based on the hypothesis that the synergistic effect of mechanical forces and bacterial biofilm can lead to surface damage resulting in in vivo release of metallic particles. The primary aim of the study was to develop a dynamic fatigue test method for dental implants immersed in wet environments such as; (i) 0.01 M phosphate buffer saline (PBS); (ii) lactic acid (pH = 5); (iii) bacterial polyculture. Four dental implants each were subjected to fatigue loading from 45 N to 450 N at 4 Hz for 2 million cycles while immersed in (i) PBS (negative control); (ii) bacterial culture (test); and (iii) lactic acid (positive control). Post-testing, optical microscopy, x-ray photoelectron spectroscopy, and electrochemical corrosion tests were performed to evaluate the surface morphology, chemistry, and potential, respectively, of titanium implants. Post-testing, surface discoloration was evident in all three groups. However, the surface damage was further established in XPS analyses of test specimens, which showed that the interplay of bacterial biofilm and mechanical forces resulted in thinning of the TiO2. Lower corrosion potential (Ecorr) of the test specimens compared to positive and negative controls also illustrated damage to the oxide layer. However, other electrochemical parameters such as linear polarization resistance (LPR) and corrosion rate (CR) were comparable among the groups indicating the corrosion resistance post-testing. The synergistic effect of cyclic occlusal loading and bacteria biofilm could negatively affect the surface of titanium dental implants.