Discontinuation of simvastatin leads to a rebound phenomenon and results in immediate peri-implant bone loss

Although administration of simvastatin has been reported to promote bone formation, the effect of short-termsimvastatin administration is not well known. Following implant installation, 10-week-old male Wistar rats (n= 24) were divided into two groups randomly. The experimental group received 10 mg/kg of simvastatin daily for seven days. Then simvastatin administration was discontinued, and the animals were observed up to 28 days. Animals in the control group underwent the same procedure but received saline instead of simvastatin. All animals were analyzed by micro-computed tomography. Samples at days 14 and 21 were subjected to histological analyses. After seven days of simvastatin administration, more new bone formation around the implant was observed in the simvastatin group compared with the control group. Seven days after simvastatin discontinuation, however, the amount of peri-implant trabecular bone began to decrease. Results from morphometric analysis also showed a reduction in new bone area after day 7, which was lowest at day 14. These results were confirmed by histological analyses. In contrast, both the peri-implant trabecular bone and new bone area were maintained in the control group. Short-term administration of simvastatin may affect implant stability owing to a rebound phenomenon and an immediate loss of peri-implant bone.