Mehta Aditi, Shah Alap, Prasad Anisha, Jani Bharvi, Shah Kinnari, Kulkarni Anirudh, Chantarapanich Nattapon, Inglam Samroeng, Fareed Mohammad, Marya Anand
, Ahmedabad, Gujarat, India.
Department of Orthodontics and Dentofacial Orthopedics, Karnavati School of Dentistry, Gandhinagar, Gujarat, India.
Sci Rep. 2025 Apr 22;15(1):13938. doi: 10.1038/s41598-025-94627-5.
This study aimed to compare three different loops (T loop, Cherry loop, and Open helical loop) and optimal tip back angle (10°, 15°, 20°) for protraction of mandibular second molar using Finite Element Model (FEM). A CBCT scan of a 20-year-old patient was recorded. It was converted into a CAD file and then into a FEM. A FEM model developed was used to find out the efficacy of the loops and optimal tip-back angles. Displacement of the molar was measured at four reference points: the mesio-buccal cusp, distobuccal cusp, mesial root, and the distal root of the first molar. No significant difference was seen in the displacement for all three loops. At a 10° angle, there was more mesial tipping (5.9°) and molar extrusion. At a 15° angle, there was less mesial tipping (2.9-3°) and no changes in the vertical plane. At a 20° angle, there was bodily movement and intrusion of molars. All three loops are equally effective in the protraction of mandibular molar. A 15° tip back angle was most effective in protracting the mandibular molar as only a negligible amount of mesial tipping of the molar was seen, and there was no extrusion or intrusion of the molar, thus maintaining the occlusal plane. Loop mechanics are preferred over the use of power chains as this helps maintain better control over the molar position during protraction. Loops are very effective at avoiding mesial tipping and extrusion of molars during mesialization to close spaces.
本研究旨在使用有限元模型（FEM）比较三种不同的曲（T形曲、樱桃曲和开放螺旋曲）以及下颌第二磨牙前牵引的最佳后倾角度（10°、15°、20°）。记录了一名20岁患者的锥形束计算机断层扫描（CBCT）。将其转换为CAD文件，然后转换为有限元模型。所建立的有限元模型用于研究曲和最佳后倾角度的效果。在四个参考点测量磨牙的位移：第一磨牙的近中颊尖、远中颊尖、近中根和远中根。三种曲的位移未见显著差异。在10°角时，有更多的近中倾斜（5.9°）和磨牙伸长。在15°角时，近中倾斜较少（2.9 - 3°），垂直平面无变化。在20°角时，磨牙有整体移动和压低。三种曲在下颌磨牙前牵引方面同样有效。15°的后倾角度在牵引下颌磨牙时最有效，因为磨牙仅出现可忽略不计的近中倾斜，且磨牙无伸长或压低，从而保持了咬合平面。曲力学比使用动力链更可取，因为这有助于在牵引过程中更好地控制磨牙位置。在近中移动关闭间隙时，曲在避免磨牙近中倾斜和伸长方面非常有效。
