细的是刚开始几个月用的,用力矫**齿形状。每个月都要换一次。粗的是后来固定形状用的,有保持的作用。从弓丝材料来分:常用的有不锈钢丝和钛镍丝。钛镍丝根据性能的差别,又可分为普通钛镍丝和热激活钛镍丝,另外还有一种β钛丝。从弓丝的粗细来分:有0.012,0.014,0.016,0.018,0.020;对于方丝的粗细常见的主要有这几种(单位:英寸):0.016*0.016,0.017*0.022,0.017*0.025,0.018*0.025,0.019*0.025,0.0215*0.028。