Vardimon A D, Bourauel C, Drescher D, Schmuth G P
Maurice and Gabriela Goldschleger School of Dental Medicine, Department of Orthodontics, Tel Aviv University, Israel.
J Dent Res. 1994 Jan;73(1):67-74. doi: 10.1177/00220345940730010901.
Repulsive magnetic appliances can intrude posterior teeth, but create a lateral shift of the mandible and also decrease in force as the mouth opens. To model their optimal use, the 3-D spatial force/displacement (F/D) and moment/displacement (M/D) diagrams of four magnetic repulsive appliances in diverse overlapping arrangements were characterized and compared. In this orthodontic measurement and simulation system, only the medial eccentric magnetic arrangement, of the four compared, partially met the criteria of an optimal repulsive force system, i.e., keeping a constant intruding force and excluding shearing force. The moment analysis found that eccentric arrangements, however, developed high Z-moment. Thus, a perplexing point was reached where the force analysis favored medial centric arrangement and the moment analysis favored centric arrangement. When the gap between juxtaposed magnets increased over 2 mm, the repulsive force declined and the attractive force was favorably eliminated. At gap distances of 3 to 6 mm, the intrusive force was almost constant. These data suggest that centric arrangement is indicated clinically when the gap is minute and Müller prongs are used to prevent deleterious lateral shearing forces.
斥力磁体装置可使后牙内收，但会导致下颌出现侧向移位，并且随着开口度增大力量会减小。为模拟其最佳使用方式，对四种磁斥力装置在不同重叠排列方式下的三维空间力/位移（F/D）和力矩/位移（M/D）图进行了表征和比较。在这个正畸测量与模拟系统中，在所比较的四种装置中，只有内侧偏心磁体排列部分符合最佳斥力系统的标准，即保持恒定的内收力并排除剪切力。然而，力矩分析发现偏心排列会产生较大的Z向力矩。因此，出现了一个令人困惑的点，即力分析倾向于内侧中心排列，而力矩分析则倾向于中心排列。当并列磁体之间的间隙超过2毫米时，斥力下降，引力被有效消除。在间隙距离为3至6毫米时，内收力几乎恒定。这些数据表明，当间隙很小时，临床上应采用中心排列，并使用米勒叉来防止有害的侧向剪切力。
