应用前倾弯弓丝治疗开畸形的生物力学研究

Biomechanical study of open bite treatment with tip forward bend

目的 探讨应用前倾弯弓丝矫治开畸形的效果。方法 建立包括牙周膜、牙槽骨、 1及 6的三维有限元模型 ,分析矫治力作用下牙体与牙周组织的应力分布以及牙体的位移情况 ,明确牙齿移动的机理。结果 ① 6牙根表面、牙周膜、牙槽骨所受的最大拉应力均位于远中侧牙颈部 ,二种工况分别是 :0 .1830MPa ,0 .14 5 1MPa ;0 .0 2 0 2MPa,0 .0 16 0MPa ;0 .0 4 0 7MPa ,0 .0 32 3MPa ;最大压应力位于近中侧的牙颈部 ,分别是 :- 0 .0 2 2 7MPa,- 0 .0 180MPa;- 0 .0 186MPa,- 0 .0 14 7MPa ;- 0 .0 117MPa,- 0 .0 0 92MPa。② 1牙根表面、牙周膜、牙槽骨所受的最大拉应力均位于根尖区 ,二种工况分别是 :0 .4 36 2MPa ,0 .830 3MPa ;0 .0 0 5 5MPa ,0 .0 0 4 4MPa;0 .0 0 4 8MPa ,0 .0 0 38MPa ;最大压应力均位于舌侧牙颈部 ,分别为 :- 0 .0 0 2 2MPa ,- 0 .0 0 18MPa ;- 0 .0 0 06MPa ,- 0 .0 0 0 5MPa;- 0 .0 0 38MPa ,- 0 .0 0 0 3MPa;③运动趋势 :前牙产生向及舌向运动 ;支抗磨牙会产生近中龈向、远中向及牙冠向颊侧倾斜的复杂运动。结论 利用前倾弯弓丝治疗开畸形 ,支抗磨牙的移动趋势不利于患者后牙的直立及平面改建 ,不利于矫治效果的稳定。应用该方法矫治开畸形时 。

Objective To verify whether it is effective to treat open bite cases with tip-forward bend. Methods Three-dimensional finite element (TDFE) models of the lower left central incisor and first molar were set up by means of CT. Stress distribution in root, PDL and alveolar bone ,and the tendency of the tooth movement were obtained by calculation under different orthodontic forces. Results ①The molar model revealed that the tensile stress concentration was at the distal cervix and the compressive stress concentration at mesial cervix. ②The incisor model showed that the tensile stress was concentrated at apical tip and the compressive stress concentration was at the lingual side of the cervix. ③The incisor had the tendency to elongate and move lingually. The molar tended to tip mesially and buccally. Conclusions Arch wire with tip forward bend depends on the elongation and lingual movement of anterior teeth to treat open bite,but the anchorage molar will incline mesially further,which is not consistent with the mechanism to treat open bite.