Orthodontic tooth movement results from the response of the periodontal tissue to orthodontic force, which leads to modeling and remodeling of the surrounding alveolar bone. The response is considered to occur through the activation of specific signaling pathways, many of which are known, all acting to ultimately result in tooth movement. Much is known about the actions of these two cells, and the signaling pathways that affect them, both in bone and orthodontic literature, however, to date, little work has been carried out to examine the effect of the insulin-like growth factor binding proteins (IGFBP) in orthodontics. Therefore, we investigated the presence of IGFBP-5 in the gingival crevicular fluid (GCF) of 6 healthy subjects, and assessed the effects of orthodontic treatment on the levels and molecular state of this protein.