Treacher-Colins syndrome caused by abnormal development of the second branchial arch is rare. Treacher-Colins综合征为少见的双侧第一、二鳃弓发育异常综合征。
Three-hinge arch is an abnormal style of construction, but the internal force of cross-section of three-hinge arch is always changing as the angle changes. 三铰拱的内力常因截面处拱轴切线水平倾角的变化而变化,内力计算显得比较麻烦,且计算工程量较大。
Orthopedic treatment on skeletal class ⅱ 1 malocclusion was mainly solved abnormal of length and highness, and by modified width of arch compensated width. 2骨性安氏1的矫治主要是解决了长度和高度的不协调,同时,通过改变后牙牙弓宽度,补偿性协调了上下牙弓宽度的不协调。