Oestrogen replacement therapy promotes bone healing around dental implants in osteoporotic rats

The aim of this study was to investigate the effect of oestrogen replacement therapy on bone healing around titanium implants in osteoporotic rats. Sixty 32-week-old female SD rats were used in this study. Ovariectomies were performed in 40 rats, and other 20 rats had sham operation. Eighty-four days after surgery, osteoporotic changes in proximal tibiae were seen in four ovariectomized rats when compared with two sham-operated rats. Then pure titanium implants were placed in the bilateral proximal metaphyses of the tibiae of the remaining animals. Oestrogen replacement therapy was administrated in 18 ovariectomized rats after implantation. Nine rats from each group (ovariectomized, oestrogen-treated and sham-operated) were killed at 28 and 84 days after implantation surgery respectively, and the tibiae specimens were harvested and examined. Both at 28 and 84 days after implantation surgery, most bone histomorphometric indices in the oestrogen-treated group were significantly increased compared with those in the ovariectomized group (P < 0.05 or P < 0.01). Although the oestrogen-treated group showed lower trabecular bone volume at 28 days after implant surgery and lower mineralization rate at both the two time points than the sham-operated group, there were no significant differences in other bone histomorphometric indices between the oestrogen-treated group and the sham-operated group both at 24 and 84 days after implantation. The results of this study suggest that oestrogen replacement therapy may promote bone healing around titanium implants under osteoporotic state, and therefore it seemed to be beneficial to long-term success of dental implants in clinical postmenopausal patients.