下顎骨 後方 堅引力이 家免의 顎骨 成長에 미치는 影響에 관한 實驗的 硏究

The effect of retractive force on jaw growth in growing rabbits

The purpose of this study was to investigate the effect of jaw growth in a growing rabbits, when they are subjected to retractive force and after removal of retractive force. The experimental animals were Oryctolagus couniculus, male rabbits of 4 weeks of age. The mandible is retracted with 200gm in force of each side to the posterior and superior direction for 14 hours a day. Then rabbits were used as control group. First experimental group received retractive force for 4 weeks. Second experimental group received for 8 weeks. Third experimental group received for 12 weeks. True lateral films and dorso-ventral films were taken before wearing appliances, 4 weeks, 8 weeks, 12 weeks and 16 weeks after wearing appliance. The changes of rabbits jaw growth were observed radiographically. The findings were as follows : 1. Mandibular retractive force decreased total mandibular length, mandibular condylar length and angular length. 2. Mandibular retractive force increased nasal height, condylar width and angular width. 3. Mandibular retractive force decreased mandibular length growth but increased mandibular width growth. 4. There is no phenomena of catch-up growth after retractive force removal.