The loss of third-order information in pre-adjusted brackets due to torsional play is a problem in clinical orthodontics. The aim of this study was to evaluate the impact of slot height, archwire height, width and edge bevel’s radius on the torsional play for three brackets/archwire systems. Ninety brackets with a 0.022 × 0.028 in. slot with McLaughlin-Bennett-Trevisi prescription from three different manufacturers were selected, and the slot’s height and depth were measured using a profile projector. Sixty stainless-steel rectangular archwires from three different manufacturers were sectioned and observed with a SEM to measure their height, width, and radius of edge bevel. The recorded data were used to calculate the theoretical torsional play between different slot−archwire combinations. One-way ANOVA was used to compare the measurements within different bracket types and among different manufacturers. Slot height was usually oversized. Archwire’s height was usually undersized, but oversized wires were also observed. The radius edge bevel was the most variable parameter. A certain degree of torsional play is always present that differs from one bracket type to another of the same producer and that can even be doubled from one manufacturer to another. Due to production tolerance, differences between the nominal values and the real dimensions of any components of a slot/archwire system are common. This results in a torsional play that limits torque expression. The archwire’s edge bevel plays an important role in torque expression, and clearer information should be provided by the manufacturers regarding this aspect.

中文翻译：

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正畸槽和弓丝的尺寸变异性：扭矩表达及其临床意义的分析。

由于正畸运动而导致在预先调节的支架中丢失三阶信息是临床正畸中的一个问题。这项研究的目的是评估槽孔高度，弓丝高度，宽度和边缘斜角半径对三个托槽/弓丝系统的扭转间隙的影响。选择了具有0.022×0.028英寸狭槽的90个托架，并使用来自三个不同制造商的McLaughlin-Bennett-Trevisi处方，并使用轮廓投影仪测量了狭槽的高度和深度。将来自三个不同制造商的60根不锈钢矩形弓丝切成薄片，并用SEM进行观察，以测量其高度，宽度和边缘斜角半径。记录的数据用于计算不同的缝隙-弓丝组合之间的理论扭转间隙。单向方差分析用于比较不同支架类型和不同制造商之间的测量结果。插槽高度通常过大。Archwire的高度通常过小，但也观察到过大的电线。半径边缘斜角是变化最大的参数。总是存在一定程度的扭转间隙，这种扭转间隙从一个托架类型到同一生产商的另一托架类型都不同，甚至可以从一个制造商到另一生产商加倍。由于生产公差，插槽/拱形系统的任何组件的标称值和实际尺寸之间的差异是常见的。这会导致扭转间隙，从而限制转矩表达。弓丝的边缘斜面在扭矩表达中起着重要作用，制造商应就此方面提供更清晰的信息。