ABSTRACT
For orthodontic tooth movement, optimal orthodontic force should be maintained without periodontal breakdown and alveolar bone should be remodeled physiologically. Therefore, To obtain proper occlusion through tooth movement within alveolar bone, we should know the biomechanics of teeth and supporting tissues. The present study was performed to observe histologic changes of periodontal tissue immediately after application of orthodontic force and during the retention period in growing young adult dogs. In this study, experimental group contained between mandibular left canie and 1st molar and control group contained contralateral teeth of same animal. The .018"x.22" stainless steel closed coil spring(Dentaurum Co.) was ligated on the experimental teeth at initial 200gm-force from mandibular canine to 1st molar. The animals(4 to 6 months aged young adult dogs) were sacrificed on 0, 14, 28 days after the finish of appliance activation, and then tissue samples were divided into hematoxylin-eosin(HE) staining section, ground section, alkaline phosphatase(ALP) staining section, and tartrate-resistant acid phosphatase(TRAP) staining section. Thereafter, the preparations were examined under light microsopy. The following results were obtained: 1. Immediately after the finish of appliance activation, the periodontal space was increased in tension side, but decreased in pressure side compared to that of control. The hyalinized zone was also observed in the periodontium. 2. After the 14-day retention, periodontal space was decreased in tension side and slightly increased in pressure side compared to that of immediately after the finish of appliance activation. The hyalinized zone was repaired and a few osteoblasts showing slightly new bone formation were seen. Osteoblasts were scarcely observed along the alveolar bone. 3. After the 28-day retention, the periodontal fibers are normally repaired. A lot of TRAP(+) osteoclasts and increased alveolar bone resorption were observed in pressure side, and AP(+) osteoblast and increased new bone formation were observed in tension side.