Effects of oestrogen deficiency and 17β-estradiol therapy on bone healing in calvarial critical size defects treated with bovine bone graft

To histomorphometrically analyze the effect of ovariectomy-induced oestrogen deficiency and 17β-estradiol therapy on bone healing of surgically created critical-size defects (CSDs) treated with bovine bone graft (BBG).Forty-eight female rats were randomly assigned to the following 3 experimental groups (n=16): sham-operated animals (SHAM), ovariectomized animals (OVX) and ovariectomized animals treated with oestrogen (OVX+E2). OVX+E2 animals received daily subcutaneous injections of 17β-estradiol (20μg/kg) from 8 days after ovariectomy until euthanasia. Thirty days after the surgery, an 8mm CSD was surgically created in each calvaria of all animals and filled with BBG. Animals were euthanized at either 30 or 60 days postoperative. A histological analysis, percentage of Newly Formed Bone Area (NFBA), osteoblast and osteoclast number was histomorphometrically performed (p≤0.05).At 30 days, SHAM group (8.82%±2.93) had significantly greater NFBA than OVX (4.66%±1.35) and OVX+E2 groups (5.85%±4.08) (p≤0.05). At 60 days, SHAM group (11.51%±3.08) and OVX+E2 group (9.84%±1.87) had significantly greater NFBA than OVX animals (5.12%±0.68) (p≤0.05). Fewer osteoblasts were observed in the OVX group at 30 (763.40±121.60) and 60 (696.60±80.92) days than in the SHAM group at 30 days (1356.00±95.38). Fewer osteoclasts were observed in the OVX+E2 group (3.25±2.16) than in the SHAM (9.75±1.82) and OVX (12.75±1.47) groups at 30 days (p≤0.05).Oestrogen deficiency compromises bone healing in calvarial CSDs treated with BBG in ovariectomized rats. After 60 days post-surgery, 17β-estradiol therapy improved bone healing in calvarial CSDs treated with BBG in ovariectomized rats.