Effects of FOSAMAX and EVISTA on Orthodontic Tooth Movement

Treatments of osteoporosis in postmenopausal women using FOSAMAX (alendronate) and EVISTA (raloxifene) show evidence of preventing bone resorption by two different mechanisms. Alendronate inhibits osteoclastic activity but not osteoclast recruitment or attachment, while raloxifene regulates osteoclastic activity by binding and modulating estrogen receptors to affect osteoclast number and activity. Our previous studies in rats indicate that cyclic force increases the fractal dimension and osteoclast count at the PDL-bone interface. Objectives: This study investigated the effects that these drugs have on tooth movement generated from cyclic force by looking at the change in intermolar distances (at pre-loading, post-loading, and relapse), MMP9 expression, and fractal dimension of the PDL-bone interface. Methods: Rat maxillary first molars were cyclically loaded without drug application (control) (n=4), and with alendronate (1.00 mg/kg body weight) (n=5) or raloxifene (6.00 mg/kg) (n=4). On every other day over two weeks, drugs were fed to Sprague-Dawley rats, and a 0.5 N cyclic force was applied from the lingual to buccal direction using customized springs. Except for drug intakes, springs were applied on control rats at the same intervals. The Scion Image (Scion Corp) image analysis program and Benoit (Trusoft, Inc.) fractal analysis program were used to calculate the fractal dimension of the PDL-bone interface via the box-dimension method. MMP9 expression by osteoclasts was observed by immunohistochemistry. Results: Control showed relapse in intermolar distance while alendronate and raloxifene groups did not. Osteoclastic counts were higher in control than drug treatment groups. Fractal dimensions were the same for all groups. MMP9 staining was observed in osteoclasts and collagen fibers with no significant difference among the groups. Conclusion: Our short-term study suggests that orthodontic treatment may be contraindicated when taking these drugs, and that longer exposure to drugs and orthodontic treatment is required to show change in fractal dimension.