This study compared the effects of local administrations of
prostaglandin E2 (
PGE2) and
1,25-dihydroxycholecalciferol (1,25-DHCC) on
orthodontic tooth movement in rats. Thirty-seven 6-week-old male Sprague-Dawley rats, weighing 160 +/- 10 g were used. Five rats served as the baseline control group. A
fixed appliance system exerting 20 g of distally directed force was applied on the maxillary incisors of 32 animals for 9 days. Eight rats served as the appliance control group; 8 received a 20-microL injection of
dimethyl sulfoxide (
solvent for 1,25-DHCC) on days 0, 3, and 6; 8 received 20 microL of 10(-10) mol/L 1,25-DHCC on days 0, 3, and 6; 8 received a single injection of 0.1 mL of 0.1 microg
PGE2 only on day 0. There was no significant difference in tooth movement between the
PGE2 and the 1,25-DHCC groups. Both
PGE2 and 1,25-DHCC enhanced the amount of tooth movement significantly when compared with the control group. The numbers of Howship's lacunae and capillaries on the pressure side were significantly greater in the
PGE2 group than in the 1,25-DHCC group. On the other hand, the number of osteoblasts on the external surface of the alveolar bone on the pressure side was significantly greater in the 1,25-DHCC group than in the
PGE2 group. Thus, 1,25-DHCC was found to be more effective in modulating bone turnover during
orthodontic tooth movement, because its effects on bone formation and
bone resorption were well balanced.