Bicortical microimplant with 2 anchorage heads for mesial movement of posterior tooth in the beagle dog

Introduction: The purpose of this research was to study the potential anchorage of a newly designed bicortical microimplant for mesial movement of posterior teeth in the mandibles of beagle dogs. Methods: Five adult male dogs with the third premolars in both arches extracted 1 week before the treatment were used in this study. Two bicortical microimplants were placed in the interradicular region at the center of resistance of the second premolar on each side of the mandible. One served as a loaded microimplant with 2 orthodontic nickel-titanium springs delivering 50 g of force between the bicortical microimplant and the fourth premolar. The contralateral bicortical microimplant without loading was the control. Implant-tooth measurements were made biweekly. At the end of tooth movement, the animals were killed, and the specimens with microimplants were embedded in methylmethacrylate and cut to 100 mu m and ground to a thickness of 70 mu m. Bone-to-implant contact was calculated. Results: All bicortical microimplants remained stable. Obvious mesial movement of the fourth premolar was observed on the loaded side, but no movement was seen on the unloaded side. No evidence of infection was seen in the histologic examination of the bone interface, and no statistical difference in the bone-to-implant contact between sides was seen. Conclusions: A bicortical microimplant with 2 anchorage units can be used for bilateral orthodontic anchorage in protraction of the posterior teeth in the mandibles of beagle dogs.