Su Jiehua, Liu Jiali, Xu Linyu, Zhong Pingping, Zhang Duanqiang
Department of Orthodontics, Affiliated Stomotological Hospital, Fujian Medical University, Fuzhou 350002, China.
Department of Orthodontics, Affiliated Stomotological Hospital, Fujian Medical University, Fuzhou 350002, China. Email:
Zhonghua Kou Qiang Yi Xue Za Zhi. 2015 Feb;50(2):84-8.
To investigate the biomechanics of J-hook headgear in En mass intrusion and retraction of maxillary anterior teeth and provide guidance for clinical treatment.
A three-dimensional finite element model of maxillary teeth, periodontium, straight wire appliance and maxillary bone was established in ANSYS 14.0. En mass retraction of anterior teeth with force of 1.5 N through J-hook headgear was stimulated. Force was applied mesial to lateral incisor in group A and distal to lateral incisor in group B. The force direction was 30° to the sagittal plane and 20° to 60° to the occlusal plane. Force direction to the occlusal plane was changed every 5° and 18 cases were calculated. Displacement of upper anterior teeth and stress distribution in the periodontium were analyzed.
As the degrees of force direction to the occlusal plane increased, the moving pattern of upper anterior teeth changed from clockwise rotation (lingual movement with intrusion) to bodily retraction and intrusion, and counter- clockwise rotation (intrusion with labial movement). With the force direction of 35° to occlusal plane applied mesial to lateral incisor or force direction of 45° to the occlusal plane applied distal to lateral incisor, bodily movement of upper anterior teeth without rotation was achieved.
Placement of J-hook mesial to lateral incisor enable orthodontists to maintain better en mass intrusion and retraction of upper anterior teeth. The direction of J-hook should be adjusted according to individual condition and treatment objective.
研究J钩头帽对上颌前牙整体压低和后移的生物力学作用，为临床治疗提供指导。
在ANSYS 14.0中建立上颌牙齿、牙周组织、直丝弓矫治器和上颌骨的三维有限元模型。通过J钩头帽以1.5 N的力刺激前牙整体后移。A组在侧切牙近中施加力，B组在侧切牙远中施加力。力的方向与矢状面呈30°，与咬合平面呈20°至60°。每隔5°改变力与咬合平面的方向，共计算18种情况。分析上前牙的位移和牙周组织的应力分布。
随着力与咬合平面角度的增加，上前牙的移动方式从顺时针旋转（舌向移动伴压低）变为整体后移和压低，再变为逆时针旋转（压低伴唇向移动）。当在侧切牙近中施加与咬合平面呈35°的力或在侧切牙远中施加与咬合平面呈45°的力时，上前牙可实现无旋转的整体移动。
将J钩置于侧切牙近中可使正畸医生更好地实现上颌前牙的整体压低和后移。应根据个体情况和治疗目标调整J钩的方向。
