Influence of osteoporosis and aging in the bone structure to biomaterial

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The aim of this experimental study was to evaluate the influence of osteoporosis induced after implantation on bone structure around dental implants using ovariectomized rats. Tibiae of 30 to 32-old female Wistar rats were used in this study. Hydroxyapatite (HA) and titanium (Ti) rods were inserted into tibiae of 6 4 rats. Six weeks after implantation, 28 rats were ovariectomized (ovx), 26 rats were sham-operated (sham) and 10 rats were sacrificed (control). Four, 8 and 16 weeks following the operation, the rats were sacrificed. The reaction of the bone tissue surrounding HA and Ti implants was examined histologically. The results can be summarized as follows.1) The body weight of "ovx" rats markedly increased compared with "sham" rats. Trabecular bone volume percent in distal region of femurs of "ovx" was significantly lower than that of "sham" 4, 8 and 16 weeks following the operation. These findings showed that the this model represents osteoporosis.2) Mature trabecular bone around HA in "ovx" was resorbed chronologically, but some remained at 16 weeks. In "sham", a large amount of trabecular bone remained around the HA and was connected to the cortical bone as seen m "control" The area of connective tissue increased chronologically m the HA and bone interface. Sixteen weeks following the operation, fibrous tissue was observed on the implant surface.3) Very small amount of mature trabecular bone remained around Ti in "ovx" as seen in distal region of femurs, whereas the thickness of surrounding bone rapidly increased at 1 6 weeks. A greater amount of mature bone was found close to Ti m "sham" compared to that in "ovx". These findings suggest that the bone reaction, especially in the bone-implant interface, is different between HA and Ti in cases of osteoporosis.