Local osteoprotegerin gene transfer inhibits relapse of orthodontic tooth movement

Introduction: In orthodontic treatment, teeth can relapse after tooth movement without retention. The aim of this study was to evaluate the inhibition effects of local osteoprotegerin (OPG) gene transfer on orthodontic relapse. Methods: Eighteen male Wistar rats were divided into 3 groups. The maxillary right first molars of all animals were subjected to orthodontic force and moved mesially. Three weeks later, the force was removed, and the teeth relapsed. During the 2-week relapse period, the 3 groups of rats received local OPG gene transfer (experimental group), mock vector transfer (mock group), and no injections (control group). Tooth movement and relapse were measured by using palatal superimpositions of 3-dimensional digital models. Histomorphometric analysis was used to quantify osteoclasts, and microcomputed tomography analysis was done to quantify the alveolar bone and the tibia. Results: Relapse was significantly inhibited and the number of osteoclasts was reduced in the experimental group. On the other hand, bone mineral density and bone volume fraction of alveolar bone were significantly increased. Bone mineral density and bone volume fraction of the tibia showed no significant difference between the groups. Conclusions: Local OPG gene transfer to periodontal tissues could inhibit relapse after orthodontic tooth movement, through the inhibition of osteoclastogenesis.