How does alendronate affect orthodontic tooth movement in osteogenesis imperfecta: an in vivo study on a mice model.

OBJECTIVES: The purpose of this study was to evaluate the effects of alendronate on orthodontic tooth movement (OTM) and bone modelling/remodelling in an osteogenesis imperfecta (OI) mice model.

MATERIALS AND METHODS: Ten-week-old male and female OI mice (Col1a2oim, n = 32) were divided into four groups: 1. Alendronate male (AM, n = 8), 2. Alendronate female (AF, n = 8), 3. saline male (SM, n = 8), and 4. saline female (SF, n = 8). The mice in all four groups received either Alendronate (0.05 mg/kg) or vehicle (saline 0.05 mg/kg) subcutaneously for 2 weeks prior to the placement of orthodontic spring. A nickel-titanium spring applying 3-5 cN of force was used to perform the OTM for 1 week. After 7 days of OTM, the OI mice were euthanized with CO2 inhalation and microfocus computed tomography and histological analyses were performed.

RESULTS: AM and AF mice showed a significant decrease (P < 0.05) in the rate of OTM compared with SM and SF mice, respectively. In addition, AM and AF mice showed a significant increase (P < 0.05) in the bone volume fraction (BVF) and tissue density (TD) compared with SM and SF mice. Histological analysis of haematoxylin-eosin staining revealed a hyalinization zone in AM and AF mice compared with SM and SF mice. Furthermore, tartrate-resistant acid phosphatase staining indicated decreased number of osteoclasts in AM and AF mice compared with SM and SF mice. Picrosirius red staining showed, Alendronate treatment led to thick uniform and smooth morphology of collagen fibres as compared with saline group. Similarly, second harmony generation images also revealed thicker collagen fibres at the periodontal ligament (PDL)-cementum entheses and PDL-alveolar bone entheses in AM and AF mice compared with SM and SF mice.

CONCLUSIONS: Alendronate led to a decrease in the rate of OTM, increase in BVF and TD, decrease in the number of osteoclasts, and smooth and thick collagen fibres compared with saline in both male and female OI mice.