Bone Abstracts

To evaluate the regeneration of alveolar bone after treatment with bone-resorption inhibitors in old acyclic rats that had been through a long period of low estrogen. Thirty-two female Wistar rats with 20 months old intact and ovariectomized (OVX at 4 months of age), were randomized into four groups (n=8/group): i) intact; ii) OVX/O (corn oil); iii) OVX/E₂ (17β-estradiol, 400 μg) and iv) OVX/RLX (Raloxifene, 1 mg/kg per day). All treatments began on the 420th day after OVX and lasted for 60 days. At 20 months old, all groups had their right-upper incisors extracted. At 28 days after the tooth extraction, the right maxilla was prepared to histological analyses and immunohistochemistry reaction for osteocalcin. Plasma samples were submitted to RIA for estradiol and ELISA assay to determine osteocalcin concentration. In OVX/E₂ group higher plasmatic concentration of estradiol was verified. The histomorphometric analysis showed 45.26% of bone formation in the intact groups with a higher number of osteocytes and presented bone lining cells more positive for osteocalcin immunolabeling than groups OVX/O and OVX/RLX. The OVX/O groups showed 30.99% of bone formation and discrete presence of osteoblastic lineage cells with positive immunolabel for osteocalcin. The group OVX/E₂ showed 50.28% of bone formation and the number of osteocytes lower than the intact animals, showed yet a more expressive positive label for osteocalcin than other OVXs groups. The OVX/RLX group showed 38.60% of bone formation, greater positive osteocalcin immunolabeling with the presence of osteoblastic cells immunopositive for osteocalcin and a lower number of osteocytes, similar to the animals of group OVX/O. The plasmatic osteocalcin concentration were significantly elevated in OVX animals in comparison with the intact group. Furthermore, plasmatic osteocalcin values were significantly reduced by E₂ and RLX. Our results show that administration of E₂ or RLX to oestrogen-deficient rats leads to a better recovered of alveolar bone healing.