頭部 X 線規格写真による正常咬合および上顎前突者の成長変化に関する研究

Abstract

The present study was undertaken to determine the difference morphologically and longitudinally between normal occlusion and maxillary protrusion with more than overjet 5 mm. The 42 subjects comprised of 11 males and 10 females with normal occlusion and 11 males and 10 females with maxillary protrusion. Lateral roentgenocephalograms taken at 6 years and 12 years were mainly used. The results were as follows : On the mean growth of both male and female, there were significant differences between normal occlusion and maxillary protrusion in ANB angle, A-B distance, overbite, and overjet. The mean values for maxillary protrusion were bigger than those for normal occlusion with aging. On the individual growth of both male and female, facial axis did not change in 60% of normal occlusion but decreased in 60% of maxillary protrusion. The mandible also rotated posteroinferiorly. Ramal plane angle ∠BN-CG increased in 60% of normal occlusion, and did not change in 30%. The angle increased in 90% of maxillary protrusion, and opened. Mandibular plane angle ∠BN-GG decreased in 50% and did not change in 30% of normal occlusion. This angle did not change in 40% and decreased in 30% of maxillary protrusion, then gonial angle decreased. Palatal plane angle ∠BN-PP increased in 70% of both normal occlusion and maxillary protrusion ; clockwise rotation was found. Occlusal plane angle ∠BN-Occ showed no change or decrease in 100% of normal occlusion and in 80% of maxillary protrusion. Condyle growth direction index ∠CDC' showed increase or no change in 80% of both normal occlusion and maxillary protrusion ; condyle had a tendency to grow anterosuperiorly. The above results showed many references leading to greater maxillary protrusion tendency for maxillary protrusion as compared with normal occlusion ; for example, opened facial axis and ramal plane angle. There were also strong significant negative correlation coefficients between facial axis and mandibular plane angle ∠BN-GG for both normal occlusion and maxillary protrusion, and both male and female. However, there were no significant correlation coefficients between facial axis and mandibular length Cd-Gna.