Phelps A E
Angle Orthod. 1978 Oct;48(4):283-90. doi: 10.1043/0003-3219(1978)048<0283:ACOLFC>2.0.CO;2.
A comparison has been made of cases treated with deliberate anchorage preparation (Class III elastic mechanics) prior to Class II elastic mechanics and cases treated with Class II elastic mechanics only. Treatment goals were the same. Extraoral traction was used as necessary to achieve those goals. Appliance quantity and size were the same. Age, sex, and severity of malocclusion were comparable. It remained that the anchorage-prepared cases demonstrated a flattening of the mandibular plane, greater retraction of the lower incisors, more retraction of midface, and more protraction of lower face. These changes of lower face are consistent with the normal growth changes of the human face.
对在使用II类弹性力学之前采用刻意支抗预备（III类弹性力学）治疗的病例与仅采用II类弹性力学治疗的病例进行了比较。治疗目标相同。必要时使用口外牵引来实现这些目标。矫治器的数量和尺寸相同。年龄、性别和错牙合畸形的严重程度具有可比性。结果发现，采用支抗预备的病例表现出下颌平面变平、下切牙更多后移、中面部更多后移以及下面部更多前突。下面部的这些变化与人类面部的正常生长变化一致。
