Transmission electron microscopic and high voltage electron microscopic observations of the bone and osteocyte activity adjacent to unloaded dental implants placed in dogs.

The purpose of this report is to describe ultrastructural observations of the bone and associated tissues supporting 24 unloaded endosteal dental implants placed in mongrel dogs (canis familiaris). The following 3 specific areas of the supporting tissues were targeted: 1) the osteocyte populations; 2) the mineralized collagen fiber matrix of the bone; and 3) an electron dense interfacial deposit. To investigate these areas, transmission electron microscopy and high voltage electron microscopic (HVEM) protocols were emphasized. HVEM permitted stereologic observations. Further, all observations were obtained from undecalcified tissues obtained from animals with commercially available implants placed into the mandible. From the study we observed a mineralization pattern of the implant supporting bone that was similar to those events occurring naturally within the mandibular bone. Osteocyte morphology was similar whether the osteocytes were found well below the implant interface or close to the interface. Osteocytes within lacunae were routinely found close to the implant interface, often extending cellular processes through canaliculi to the bone-implant interface. At the interface, an electron dense deposit approximately 50 nm in thickness was often observed. In interfacial regions, densely mineralized collagen fibers were observed running primarily parallel to the implant surface. This dense mineralized tissue was separated from the interface by a mineralized, but finely fibrillar matrix of approximately 200 nm in thickness.