Influence of human parathyroid hormone during orthodontic tooth movement and relapse in the osteoporotic rat model: A preliminary study.

Abstract

To investigate the effects of parathyroid hormone (PTH) on tooth movement in ovariectomized (OVX) rats by comparing the tooth movement distance and relapse and by examining the alveolar bone microstructure. Thirty 8-week-old female rats were classified into 3 groups: sham-operated, OVX and ovariectomized rats injected with PTH (PTH). Eight weeks later, a closed-coil spring appliance was placed between the maxillary incisor and the first molar and then activated with 50cN of force. During tooth movement, 30μg/kg of PTH was administered 3 times per week in the PTH group. Tooth movement distances were measured weekly. Five rats in each group were killed after 3weeks for microcomputerized tomographic analysis, and the remaining 5 rats in each group were killed at an additional 3weeks after the removal of the appliance to measure relapsed distance. The OVX group showed significantly greater tooth movement compared to those in the other 2 groups at 2 and 3weeks (P<.05). The relapse distance and relapse percentage for the OVX group were higher; however, it did not differ significantly from the PTH group. On micro-CT analysis, bone volume/tissue volume ratio and bone mineral density in the PTH group were significantly greater than in the OVX group (P<.05). Application of PTH did not promote tooth movement in OVX rat, however, did lead to decrease in relapse tendency. Therefore, the application of PTH during orthodontic treatment of patients with osteoporosis should be carefully considered.