Timing of force application on buccal tooth movement into bone-grafted alveolar defects: A pilot study in dogs

Abstract

The aim of this pilot study was to evaluate the effect of the timing of postoperative orthodontic force application on bone remodeling during tooth movement into surgical alveolar defects with bone grafts in beagle dogs. Six beagle dogs underwent surgery for buccal dehiscence-type defects (width, 5mm; height, 6mm) on the distal root of maxillary second premolars bilaterally for 12 defects. After 1-month healing, bone-augmentation procedures were undertaken at the dehiscence defects. The second premolars were protracted buccally for 6weeks into the surgical sites immediately (F-0), at 4weeks (F-4), or 8weeks (F-8) after grafting. Orthodontic tooth movement was monitored using digital models. Remodeling of alveolar bone was evaluated by histology, histomorphometry, immunohistochemistry, microcomputed tomography, and fluorescence microscopy. Group F-0 showed significant expansion (mean, 2.42mm) and tipping (mean, 9.03°) after completing orthodontic tooth treatment. The vertical bone defect was significantly lower in groups F-4 and F-8 than that in group F-0 (mean, 2.1, 2.7, and 4.5mm, respectively). In group F-4, the formation of new bone and mineralization were significantly greater than those in groups F-0 and F-8 (P<0.05). Group F-4 showed a minimal amount of bone-material remnants. Immunohistochemistry showed the highest expression of collagen-1 and osteopontin in group F-4, followed by group F-8 and group F-0, which demonstrated high osteoblast activity and enhanced bone remodeling in group F-4. Orthodontic force application at 4weeks after an augmentation procedure provided the best functional stimulation for an alveolar bone graft. This strategy enhanced new-bone regeneration and degradation of bone substitutes and, eventually, promoted bone remodeling in the bone-grafted area.