Bacterial biofilm on successful and failed orthodontic mini-implants--a scanning electron microscopy study

Mini-implants have been extensively used in Orthodontics as temporary bone anchorage devices. However, early failure of mini-implants due to mobility might occur and the colonization of their surfaces by pathogenic bacteria has been referred to as one of the contributing factors. In this study, scanning electron microscopy (SEM) was used to assess the presence of microorganisms adhered to the surface of mini-implants that failed due to loss of stability. Twelve self-drilling titanium mini-implants (1.6 mm diameter × 9.0 mm long) were collected from 12 patients undergoing orthodontic treatment-7 successful and 5 failed mini-implants. The mean time of permanence in the mouth was 15.8 and 2.4 months for successful and failed mini-implants, respectively. The devices were placed in the maxilla and/or mandible and removed by the same surgeon and were processed for SEM analysis of the presence of microorganisms on their surfaces (head, transmucosal profile, and body). Extensive bacterial colonization on mini-implant head and transmucosal profile was observed in all successful and failed mini-implants. None of the failed mini-implants exhibited bacteria on its body and only one mini-implant belonging to the successful (stable) group exhibited bacteria on its body. The results did not suggest a relationship between failure and presence of bacterial colonies on mini-implant surfaces.