Effect of systemic intermittent administration of human parathyroid hormone (rhPTH[1-34]) on the resistance to reverse torque in rabbit tibiae.

The aim of this study was to evaluate the effect of intermittent administration of human parathyroid hormone [rhPTH (1-34)] on the removal torque of implants placed in rabbit tibiae. Twenty male New Zealand rabbits were submitted to implant surgery. Each animal received one machined screw-type implant (3.75 mm diameter x 8 mm length) in the proximal metaphysis of the right tibia. The rabbits were then divided into 2 groups: the test group (n = 10) received 6 microg/kg of rhPTH (1-34) subcutaneously in the dorsal region 3 days a week, and the control group (n = 10) received placebo. Removal torque was performed at 28 and 56 days after implant placement for both groups. The mean removal torque values at 28 days were 37.0 +/- 4.36 Ncm and 47.4 +/- 6.77 Ncm for control and test groups respectively (P < .05). At 56 days the reverse torque was 45.8 +/- 3.96 Ncm for the control group and 55.8 +/- 2.86 Ncm for the test group, indicating that the removal torque was significantly higher in the test groups (P < .05). These results demonstrated that intermittent treatment with rhPTH (1-34) enhanced the removal torque of implants in rabbit tibiae.