1975年Jacobson介绍了Wits法。即通过A点及B点向解剖性平面作垂线。其交点间的距离为Wits值.平均在-2mm～+3mm之间.它对于判断颌骨前后不调的程度很有帮助.但是,在混合牙列期的深覆患者其解剖平面与切能性平面完全不一致;同样,在恒牙期的有陡峻矢状曲线患者,很难作出解剖平面。本研究的目的是观察在青少年及年青成人中用上述两条不同的平面后对Wits的影响.并把它与骨性及 Jacobson introduced the Wits Act in 1975. That is, through point A and point B to the anatomical  plane for vertical. The distance between the intersections is Wits, which averages between -2 mm and +3 mm, which is helpful in judging the degree of pre and post jaw dislocation.However, in the mixed dentition period, In the same way, it is very difficult to make anatomical planes in patients with steep sagittal curves during the permanent dentition. The purpose of this study was to observe the effect of Witch's flat on the Wits in adolescents and young adults,