Scanning electron microscopy observations of osseointegration failures of dental implants that support mandibular overdentures.

AIM: : Investigating possible failure causes of mandibular implants after their immediate loading with an overdenture retained with bilateral bar attachments, using scanning electron microscope. PATIENTS AND METHODS: Twenty edentulous male patients were included in the present study. Each patient had 2 fixtures inserted in the canine and the first molar areas on each side of the mandible. After abutments screwing, the 2 fixtures on the same side were splinted with a bar, and immediately loaded with an overdenture. Implants mobility was assessed on weekly basis. Failed implants were removed, and examined by scanning electron microscope. RESULTS: The failed implants, removed after 4 weeks of treatment, showed an intimate contact of mineralized and osteoid tissues with dense collagen-rich matrix in the apical third of implants. Furthermore, newly developed bone was observed at the same area in implants removed after 7 weeks. However, there was no evidence of such growth at the middle and/or cervical thirds in either case. CONCLUSION: Lack of osseointegration at the middle and cervical thirds of the root could be a possible cause of implant failure. Early loading by an overdenture retained with bilateral bars is considered a major contributing factor to incomplete osseointegration of the supporting implants.