Efficacy of the systemic co-administration of vitamin D3 in reversing the inhibitory effects of sodium alendronate on orthodontic tooth movement: A preliminary experimental animal study

Introduction: Bisphosphonates can severely slow down orthodontic tooth movement (OTM) by reducing bone turnover. This calls for materials and methods to reverse or neutralize their effects on OTM. We propose systemic vitamin D3 (D3) for this purpose. Methods: Thirty-two male Wistar rats were randomized into 4 groups of 8 each. Three groups were administered D3 (3 systemic doses of 24,000 IU/kg each), alendronate (ALN) (5 doses of 7mg/kg each), and ALN+D3 (same doses as mentioned above). One group served as the negative control. The incisors were distalized at 30 g of force for 2 weeks. OTMs were measured blindly. Radicular pressure areas were searched histologically (blindly) for capillaries, Howship's lacunae, osteoclasts, and osteoblasts. Data were analyzed statistically (alpha=0.05, alpha=0.0083, beta<0.1). Results: OTMs in the groups D3, ALN+D3, ALN, and control were 1.900 +/- 0.237, 1.629 +/- 0.219, 0.975 +/- 0.145, and 1.565 +/- 0.324 mm (analysis of variance, P<0.001), respectively. OTM in the ALN group was smaller than all other groups (Tukey, P<0.001). OTM in the D3 group was greater than in the control group (P = 0.054). The ALN+D3 group had greater OTM than the ALN group (P<0.001) but was not significantly different from the D3 (P = 0.153) or control (P = 0.951) groups. All histologic variables were significantly different across groups (Kruskal-Wallis, P<0.001). All the markers in the D3 group were more frequent than those of the other groups (Mann-Whitney U, P<0.001). There were fewer markers in the ALN group than in the control group (P <= 0.001). The ALN+D3 group had more markers than the ALN group in terms of capillaries, osteoclasts, and osteoblasts (P <= 0.007). The ALN+D3 group was similar to the control group regarding capillaries, osteoclasts, and osteoblasts (P >= 0.382). Conclusions: Systemic vitamin D3 may accelerate OTM and increase histologic biomarkers of bone turnover. ALN reduces OTM and its histologic biomarkers. Systemic vitamin D3 can reverse this inhibitory effect of ALN on OTM back to normal.