Transmission electron and high-voltage electron microscopy of osteocyte cellular processes extending to the dental implant surface.

Examination of the morphology of osteocytes within the bone supporting endosteal dental implants was performed using conventional transmission and high-voltage transmission electron microscopy (HVEM). The in vivo dog model used 72 implants inserted into the premolar region of 18 experimental animals. Forty-eight implants in 12 dogs were used as anterior abutments for fixed bridges for periods up to 12 months. The mineralized matrix of the supporting bone was either directly apposed to the implant surface or was separated from the implant by a narrow region of unmineralized matrix. Osteocytes were routinely observed to be closely associated with the bone-implant interface, as well as at a distance from the implant. Osteocytes were found to extend cellular processes directly to the implant surface through canaliculi. The osteocyte processes contained microfilaments. The three-dimensional capabilities of HVEM elucidated the nature of these cell processes at the point of exit from the osteocyte, as the processes extended through the mineralized matrix, and as the processes terminated at the implant interface. This report suggests that avenues of communication may exist between the implant and the osseous cells, providing intriguing hypotheses regarding biomechanical forces and osteogenesis at the implant interface. Furthermore, an electron-dense deposit was observed upon the inner confines of the canalicular wall, upon the outer aspects of the osteocyte lacuna, and upon the outer aspect of the bone interfacing the implant.