Bone formation and tooth movement are synergistically enhanced by administration of EP4 agonist

Introduction: Stimulation of the prostaglandin receptor EP4 induces bone anabolic responses to external loading. The aim of this study was to determine the possibility of synergistic enhancement of tooth movement along with bone formation in vivo through the stimulation of the prostaglandin receptor EP4. Methods: The sample consisted of 25 male rats, 6 to 7 weeks old. Experimental tooth movement was induced in the maxillary right molars with a split-mouth design. During the 7-day experimental period, some rats were injected periodically with a specific EP4 agonist (ONO-AE1-329), a drug that binds to the EP4 receptor to mimic the actions of ligand binding; the injection site was on the tension side in the interproximal region between the first and second molars. Other rats received vehicle injection (saline solution only). For control, EP4 agonist or vehicle was injected into some rats, but tooth movement was not initiated. The amounts of tooth movement and bone volume of the paradental region were evaluated by using soft x-ray and micro-computed tomography. Results: The injection of EP4 agonist alone did not induce notable changes in body weight, macro-structures, or bone volume compared with the vehicle-treated group or the untouched control side. EP4 agonist injection in conjunction with tooth movement significantly enhanced the amounts of tooth movement and regional bone volume in the tension side compared with the vehicle-treated group (P <.05). Conclusions: Our preliminary study suggests the possibilities of synergistic enhancement of the rates of tooth movement and bone formation during tooth movement through the local injection of a specific EP4 receptor agonist. However, more study on the synergistic effect on tooth movement and bone formation in response to an EP4 agonist is needed to determine its mechanisms.