【伊卡洛斯】評論

根據Contemporary Orthodontics Ch16. Closing loop mechanics 節錄如下Root-Paralleling Moments... If the legs of a closing loop were parallel before activation, opening the loop would place them at an angle that in itself would generate a moment in the desired direction. Calculations show that unacceptably tall loops would be required to generate appropriate moments in this manner, so additional moments must be generated by gable bends (or their equivalent) before the loop is placed in the mouth 如果loop兩側原本是平行的，那activate之後會產生bodily movement的moment，雖然crown移動但產生一個旋轉的結果，而這個我們不希望的旋轉可以透過增加一個moment of couple來去控制抵銷->舉例而言 牙齒往後退 crown distal tipping, root相對mesial tipping可以簡單想成一個旋轉，但此時額外增加一個couple讓root往distal 轉，那這樣可以讓整體合力變成讓translation就是root-paralleling的效果