Effect of Alendronate on Bone Formation during Tooth Extraction Wound Healing

Alendronate (ALN) is an antiresorptive agent widely used for the treatment of osteoporosis. Its suppressive effect on osteoclasts has been extensively studied. However, the effect of ALN on bone formation is not as clear as its effect on resorption. The objective was to determine the effect of short-term ALN on bone formation and tooth extraction wound healing. Molar tooth extractions were performed in mice. ALN, parathyroid hormone (PTH), or saline (vehicle control) was administered. PTH was used as the bone anabolic control. Mice were euthanized at 3, 5, 7, 10, and 21 d after extractions. Hard tissue healing was determined histomorphometrically. Neutrophils and lymphatic and blood vessels were quantified to evaluate soft tissue healing. Gene expression in the wounds was assessed at the RNA level. Furthermore, the vossicle bone transplant system was used to verify findings from extraction wound analysis. Alkaline phosphatase (ALP) was visualized in the vossicles to assess osteoblast activity. ALN exhibited no negative effect on bone formation. In intact tibiae, ALN increased bone mass significantly more than PTH did. Consistently, significantly elevated osteoblast numbers were noted. In the extraction sockets, bone fill in the ALN-treated mice was equivalent to the control. Genes associated with bone morphogenetic protein signaling, such as bmp2, nog, and dlx5, were activated in the extraction wounds of the ALN-treated animals. Bone formation in vossicles was significantly enhanced in the ALN versus PTH group. In agreement with this, ALN upregulated ALP activity considerably in vossicles. Neutrophil aggregation and suppressed lymphangiogenesis were evident in the soft tissue at 21 d after extraction, although gross healing of extraction wounds was uneventful. Bone formation was not impeded by short-term ALN treatment. Rather, short-term ALN treatment enhanced bone formation. ALN did not alter bone fill in extraction sockets.