[Effects of local application of 1,25 (OH)2D3 on experimental tooth movement in rats]

The purpose of the present study was to explore the effect of local application with Vitamin D metabolite, 1,25 dihydroxycholecalciferol (1,25 (OH)2D3), on experimental tooth movement in rats. 1. According to Waldo's method, a piece of orthodontic elastic band was inserted between the upper first and second molars of Wistar male rats weighing 200 g. The amount of 20 microliters of 1,25 (OH)2D3(10(-12)-10(-7) M) was injected locally in the submucosal palatal area of the root bifurcation of the right first molar. The left side was injected with vehicle. The number of osteoclasts was counted in a 700 x 1050 micron 2 area of the inter-radicular septum. The number of osteoclasts was dose-dependently increased 2-fold at 10(-10) M 1,25 (OH)2D3 compared to that in the vehicle-injected side. The maximal increase of osteoclast number was observed 3 days after local injection of 10(-10) M 1,25 (OH)2D3 on experimental tooth movement. 2. The upper first molar of Wistar male rats was moved in a buccal direction by a helical spring. The amount of 20 microliters of the local administration of 10(-10) M 1,25 (OH)2D3 was repeated every 3 days until sacrifice at day 20. The tooth movement in the 1,25 (OH)2D3-treated rats was accelerated about 2-fold compared to that in the control rats. 3. The effect of bone formation in the rats receiving experimental tooth movement was examined by fluorescent labeling and quantitative histology. Thus, the local application of 10(-10) M 1,25 (OH)2D3 tended to prevent the decrease of the mineral apposition rate of the alveolar bone following orthodontic tooth movement. 4. Serum samples of these 1,25 (OH)2D3-treated rats was obtained from abdominal aorta 3 hours after the final injection. Serious effects were not found in the values for parameters such as calcium, phosphorus and alkaline phosphatase. These findings suggested that the local use of 1,25 (OH)2D3 on experimental tooth movement in the rats caused increase in osteoclasts number and accelerated tooth movement. However, no obvious side effects were noted. 1,25 (OH)2D3 was expected to stimulate mineral apposition rate of alveolar bone on the tension side.