Background Wnt signaling is valuable protein network involved in bone metabolism; however, its relationship in bone resorption and formation during orthodontic treatment is currently unknown. Purpose This study examined Wnt5a expression on the compression side in an in vivo experimental rat tooth movement model. The study then investigated the relation of compression force(CF)to Wnt5a expression from human periodontal ligament(PDL)cells. Material and Methods In vivo, to movement the maxillary first molar, we added 10 g of orthodontic force to twenty male rats for seven days. We assessed the production of tartrate-resistant acid phosphatase (TRAP) and Wnt5a protein in rats alveolar bone through an immunohistochemical analysis. In vitro, we examined the effect of compression force(CF)on Wnt5a expression using the human PDL(hPDL)cells. Results We observed resorption lacunae with the multinuclear cells in rat alveolar bone during tooth movement in the 10g group. We observed Wnt5a immunoreactivity on day seven with orthodontic force in the PDL tissue. Wnt5a expression increased for timedependent maner after addition of CF in hPDL cells. Conclusion Given these findings, the Wnt signaling response to optimum orthodontic force appears to stimulate resorption of alveolar bone in the orthodontic tooth movement.

Wnt signaling plays a vital role in bone metabolism. However, currently, its role in bone formation and resorption during orthodontic tooth movement is still unclear. This study aimed to investigate in vivo Wnt5a expression in the resorbed root in rats during experimental tooth movement. Eighteen 6-week-old, male Wistar rats were subjected to an orthodontic force of 10 or 50 g for 7 days to induce the mesial movement of the upper first molars. Immunohistochemical analysis was performed to assess tartrate-resistant acid phosphatase, receptor activator of nuclear factor-B ligand(RANKL), and Wnt5a protein expressions in the alveolar bone. Additionally, the effects of different compression forces (CFs)on Wnt5a production were investigated using human periodontal ligament(hPDL) cells and human cementoblast-like cells in vitro. Resorption lacunae with multinucleated cells in the CF-10 g group under experimental tooth movement conditions in vivo. Moreover, RANKL and Wnt5a immunoreactivity was detected in the alveolar bone-PDL tissues. In the CF-50 g group, resorption lacunae and RANKL and Wnt5a expressions were detected in PDL-cement tissues. In the in vitro study, 1.0-and 4.0-g CF increased Wnt5a production in hPDL cells and HCEMs, respectively, in a time-dependent manner. These results indicate that the Wnt signaling response to heavy orthodontic forces stimulates the root resorption process during orthodontic tooth movement.