A 牙颈缘在牙冠各轴面均呈弧形曲线 B
颈曲线在唇颊面呈凸向<img border="0" alt="" src="https://img.weimei168.com/uploads/upimg/20230804/12272922_0.gif">缘方的弧线 C
颈曲线在近中面呈凸向<img border="0" alt="" src="https://img.weimei168.com/uploads/upimg/20230804/12272922_0_1.gif">缘方的弧线 D
颈曲线在远中面呈凸向<img border="0" alt="" src="https://img.weimei168.com/uploads/upimg/20230804/12272922_0_2.gif">缘方的弧线 E
颈曲线在舌面呈凸向根方的弧线