A HISTOLOGICAL INVESTIGATION ON TISSUE RESPONSES TO TITANIUM IMPLANTSIN CORTICAL BONE OF THE RAT FEMUR

IMPLANT MATERIALS ARE PLACED under various sites-including cortical bo ne, spongy bane, and bone marrow-at the same time according to the dep th at implantation. Although cortical bone is an important site for th e prognosis of implantation, detailed reports on tissue responses to i mplantation have been meager. The present study aims to reveal tissue responses to pure titanium implantation in rat femoris cortical bone. The rats received titanium bars surgically in their femurs and were sa crificed 1 day to 40 weeks post-implantation. The prepared tissue spec imens were processed for light and transmission electron microscopy (T EM). Further histochemical detections were performed. One day post-imp lantation, empty osteocytic lacunae indicating degeneration of osteocy tes were found in pre-existing cortical bone around the implant. Such pre-existing bone was replaced by new bone, but remained in part even 40 weeks post-implantation. Light microscopy showed that direct contac t between the implant and new bone was identified 12 weeks post-implan tation, Chronological and ultrastructural observation showed that new bone deposition appeared to proceed toward the implant, and that the i ntervening layer at the interface was derived from the degenerated deb ris of multinucleated giant cells and/or osteoblasts. Furthermore, it seemed that the width of intervening layer varied in relation to the d istance from the blood vessels. The cells showing tartrate resistant a cid phosphatase activity possessed cytological features of osteoclasts under TEM; they were frequently observed in perivascular sites near t he implants even after osseointegration, suggesting that bone remodeli ng took place steadily around the implant.