The aim of this study was to investigate the periodontal response according to the timing of orthodontic force application after bone graft into the angular bony defect Nine dogs were divided into three groups, 2, 4, and 6 weeks, according to the timing of orthodontic force application after bone graft. Periodontal angular bony defects were created
surgically at the distal aspect of both maxillary third incisors. Two weeks later, flap operation was performed to eliminate inflammation and reference notch was made on the root surface at the level of the bottom of each defect. Demineralized ,freeze-dried bone was implanted on the left side whereas only debridement was done on the other side. Experimental tooth movement was executed during 8 weeks on both graft and non-graft sides. After 2 weeks of retention period, animals were sacrificed for histologic specimens. The results were obtained as follows
1. New bone formation was more pronounced in the graft side than in the non-graft side in all experimental animals. 2. In the 6-week group, new bone and cementum formation was observed in more than half from the notch to the
cemento-enamel junction, and the zone of connective tissue attachment was found without apical migration of
junctional epithelium.
3. In the 4-week group, the amount of new bone formation was smaller than in the 6-week group whereas the overall remodeling pattern was similar.
4. New bone formation was confined to around the notch and the junctional epithelium migrated apically to the level of the notch with no connective tissue attachment and cementum formation in the 2-week group.
The results of the present study suggest that periodontal response may be influenced by the timing of orthodontic force application after bone graft into angular bony defect.
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