RESUMO
Objective To study the repairing mechanism of mechanical microdamage around implants in the cortical bone of rats. Methods Thirty rats were divided into the ovariectomy group (OVX) and the sham group. At three months after the ovariectomy, a hole was drilled in the right tibial diaphysis by a metal pin. The rats were executed at 1, 2 and 4 weeks, respectively, after the hole drilling. The tetracycline and calcein labeling were performed before the execution. Bone segments containing the hole were stained with the basic fuchsin, embedded in the methylmethacrylate and cut into sections with thickness of 50 μm. Histomorphometric measurement was conducted on bone sections using Bioquant image analysis system. Results Bone resporpion cavities related to the microdamage occurred in both the OVX rats and the sham operated rats. The bone porosity and the number of bone resorption cavities were both greater in the OVX rats than that in the sham operated rats (P<0.05). In addition, the number of bone resorption cavities significantly increased with time after the surgery (P<0.05). Conclusions Increased bone porosity and resorption cavities in OVX rats may be related to the crack formation and the estrogen deficiency, which made the bone remodeling in the cortical bone of OVX rats more active. However, remarkably increased resorption cavities would reduce the bone strength and increase the risk of bone fracture.