Experimental Study On Orthodontic Tooth Movement Through Alveolar Bone Regenerates Following Mandibular Distraction Osteogenesis in Dogs

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The purpose of this study was to evaluate the effects of orthodontic tooth movement into immature or mature new alveolar bones created by distraction osteogenesis in the canine mandible.Six adult male beagles underwent 10 mm of bilateral mandibular lengthening by using custom-made intraoral bone-borne distractors between the 3rd and 4th premolars. After 2 weeks (Group 1) or 12 weeks (Group 2) of consolidation period, the 3rd premolars were distalized into the distracted bones at 100g of orthodontic force for 12 weeks. At the same time, the 2nd premolars were distalized (Control) . After the tooth movement was completed, the dogs were sacrificed for the histological evaluation.When compared the 3rd premolars in Group 1 to those in Group2 or Control's teeth, Group 1 showed that the rate of tooth movement was significantly faster(P<.05). The amount of tooth movement in Group 1 was significantly larger than that of Control (P<.01). Clinically and radiographically, the retracted 3rd premolars in Group 1 at completion of tooth movement showed distal tipping and extrusion into the regenerate, higher tooth mobility, loss of lamina dura and horizontal alveolar bone on the pressure side of the distal root, and lateral root resorption. In the histological sections obtained from Group 1, a large amount of lateral root resorption extended from enamel-cement junction to the root apex was observed and the thickness of the dentin reduced into nearly half of that of Control.These results demonstrated that severe root resorption would occur by orthodontic tooth movement into immature fibrous distracted bones, because of the higher magnitude of orthodontic force or the higher remodeling activity of bone regenerate. Further studies are needed to optimize the timing and the force magnitude for tooth movement through regenerate alveolar bone after distraction osteogenesis.