The bone remodeling process involved in orthodontic tooth movement consists of bone resorption on the compression side and bone formation on the tension side of the teeth. Osteoclasts play an important role in bone remodeling and are necessary for orthodontic tooth movement. Receptor activator of nuclear factor-κB ligand (RANKL) is essential for osteoclast formation and differentiation. Several cell types have been reported to be capable of producing RANKL. We are interested in whether there is a dominant cell type which RANKL production is critical in generating orthodontic tooth movement. In this study, we used a Cre recombinase mouse model to study the effect of RANKL deletion in periodontal ligament cells on orthodontic tooth movement. We found RANKL deletion in periodontal ligament cells significantly decreased the amount of orthodontic tooth movement and reduced the number of osteoclasts formed on the compression side after subjecting the teeth to orthodontic force. It suggests RANKL production from periodontal ligament cells contributes greatly to orthodontic tooth movement and serves as an important source of RANKL in osteoclastogenesis during orthodontic tooth movement
