Department of Orthodontics and Dentofacial Orthopedics, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan.
Angle Orthod. 2009 Nov;79(6):1102-7. doi: 10.2319/111608-587R.1.
To determine optimal loading conditions such as height of retraction force on the power arm and its position on the archwire in sliding mechanics.
A 3D finite element method (FEM) was used to simulate en masse anterior teeth retraction in sliding mechanics. The degree of labiolingual tipping of the maxillary central incisor was calculated when the retraction force was applied to different heights of a power arm set mesial or distal to the canine.
When the power arm was placed mesial to the canine, at the level of 0 mm (bracket slot level), uncontrolled lingual crown tipping of the incisor was observed and the anterior segment of the archwire was deformed downward. At a power arm height of 5.5 mm, bodily movement was produced and the archwire was less deformed. When the power arm height exceeded 5.5 mm, the anterior segment of the archwire was raised upward and lingual root tipping occurred. When the power arm was placed distal to the canine, lingual crown tipping was observed up to a level of 11.2 mm.
Placement of the power arm of an archwire between the lateral incisor and canine enables orthodontists to maintain better control of the anterior teeth in sliding mechanics. Both the biomechanical principles associated with the tooth's center of resistance and the deformation of the archwire should be taken into consideration for predicting and planning orthodontic tooth movement.
确定滑动机制中在动力臂上施加的回缩力的高度及其在弓丝上的位置等最佳加载条件。
使用三维有限元方法（FEM）模拟滑动机制中前牙整体内收。当回缩力施加到犬齿近中或远中设置的动力臂的不同高度时，计算上颌中切牙的唇舌向倾斜程度。
当动力臂置于犬齿近中时，在 0mm （托槽槽口水平）处观察到未控制的切牙舌侧冠倾斜，并且弓丝的前段向下变形。当动力臂高度为 5.5mm 时，产生整体移动，弓丝变形较小。当动力臂高度超过 5.5mm 时，弓丝前段向上抬起，发生舌侧根倾斜。当动力臂置于犬齿远中时，直至 11.2mm 水平观察到切牙舌侧冠倾斜。
在滑动机制中，将弓丝的动力臂放置在侧切牙和尖牙之间，使正畸医生能够更好地控制前牙。在预测和规划正畸牙齿移动时，应同时考虑与牙齿阻力中心相关的生物力学原理和弓丝的变形。
