Effect of estrogen and calcitonin therapies on bone density in a lateral area adjacent to implants placed in the tibiae of ovariectomized rats

Background: This study evaluated the influence of estrogen and calcitonin administration on tibial bone density in a lateral area adjacent to implants placed in ovariectomized rats (OVX). Methods: One screw-type titanium implant was placed bilaterally in the ovariectomized rats, and the animals assigned to one of the following groups: group 1 (n = 15): sham surgeries; group 2 (n = 15): OVX; group 3 (n = 14): OVX subcutaneously administered with calcitonin (CT) 4 days/week (16 IU/kg); group 4 (n = 14): OVX administered daily with 17beta estradiol (20 mug/kg). After 60 days, the animals were sacrificed and undecalcified sections obtained. Blood samples were collected to measure serum levels of alkaline phosphatase and calcium at the time of sacrifice. Bone density was measured in a 500 mum wide mineralized zone lateral to the implant. Results: Alkaline phosphatase levels in groups 2 and 3 (P >0.05) were statistically higher than groups 1 and 4 (P <0.05), and calcium serum levels were higher in group 2 than the other groups (P <0.05). Regarding bone density, the data were grouped separately for cortical (zone A) and cancellous (zone B) bone. In zone A, intergroup analysis revealed no significant difference among groups (P >0.05). However, in zone B, the animals that received estrogen administration (group 4) presented a higher bone density than groups 2 and 3 (P <0.05). Conclusion: It appears that estrogen therapy may prevent the negative influence of endogenous estrogen deficiency on bone density around titanium implants placed in ovariectomized rats.