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目的利用三维有限元方法模拟在上颌第一磨牙加载不同角度及位置的后倾曲和末端内收曲时,其受力分布规律和位移趋势,并阐明其生物力学机制。方法建立上颌全牙弓三维有限元模型。(1)使用0.018英寸×0.025英寸(0.48 mm×0.64 mm)不锈钢方丝在不同部位建立弯折15°、30°及45°后倾曲弓丝模型。观测不同工况下上颌第一磨牙在Z向的位移;(2)在不同部位建立弯折15°、30°以及45°Toe-in曲弓丝模型,观测不同工况下上颌第一磨牙在X和Y向的位移情况。结果 (1)后倾曲弯折的角度增加,第一磨牙受到净力随之增加;弯折点越靠近第一磨牙近中,其压入力量越大;弯折点靠近第二前磨牙时,磨牙呈整体伸长趋势。(2)Toe-in曲弯折角度增加,第一磨牙的旋转位移角度随之增加;Toe-in曲弯折点靠近第一磨牙颊面管近中时,第一磨牙呈整体舌向位移;弯折点靠近第二前磨牙时,呈顺时针旋转趋势。结论后倾曲对第一磨牙垂直位移影响较大,其弯折点靠近第二前磨牙时有利于支抗控制及咬合打开;Toe-in曲的弯折则有利于平衡第一磨牙旋转的副作用。
OBJECTIVE: To simulate the stress distribution and displacement tendency of the maxillary first molar loaded with posterior and end adduction at different angles and positions using the three-dimensional finite element method and to elucidate its biomechanical mechanism. Methods Three-dimensional finite element model of maxillary maxillary arch was established. (1) Bend archwire models were fabricated at different locations using a 0.018 in. X 0.025 in (0.48 mm x 0.64 mm) stainless steel square wire for bending at 15 °, 30 °, and 45 °. The maxillary first molars under different working conditions were observed in the Z direction. (2) Curved wire models of 15 °, 30 ° and 45 ° Toe-in were established in different sites. The maxillary first molars X and Y direction of the displacement. Results (1) The angle of posterior curve increased, the net force of the first molar increased, the closer the point of bending was to the first molar, the greater the force of pressing in. When the bending point was close to the second premolar, , Molars showed the overall trend of elongation. (2) As the bending angle of Toe-in curve increased, the rotational displacement angle of the first molar increased. When the bending point of Toe-in curve was close to the buccal canal of the first molar, the first molar showed an overall lingual displacement. Bending point near the second premolar, clockwise rotation trend. Conclusions The posterior curve has a great influence on the vertical displacement of the first molar. When the bending point is close to the second premolar, it is conducive to the control of the occlusion and occlusion. The bending of the Toe-in curve helps to balance the side-effect of the first molar rotation .