Fig. 8 Fig. 11 Fig. 9 Fig. 12 Fig. 10 Fig. 13 What are the forces in this system? (Fig. 10) Since the line of force on the second molar is parallel to its COR in the sagittal plane the molar will bodily protract. In the transverse plane, any potential mesial-lingual rotation of the tooth will be limited by the archwire (Fig. 11). If it is necessary to increase the pull of the NiTi closed coil spring, the practitioner may use a shorter spring or move the TAD anteriorly (Figs. 12-13). If the TADs are placed more anteriorly, between the lateral incisors and cuspids, the closed coil springs are no longer on a straight line and must negotiate a curva-ture in the arch, the spring may become embedded in the soft tissue. Consider using a crimpable auxiliary 32 Fall 2018 JAOS
Journal of the American Orthodontic Society Fall 2018: Page 32
