Department of Biotechnological and Applied Clinical Sciences, University of L'Aquila, Viale S. Salvatore, Edificio Delta 6, 67100, L'Aquila, Italy.
Department of Life, Health and Environmental Sciences, University of L'Aquila, Piazzale Salvatore Tommasi 1, 67100, L'Aquila, Italy.
Prog Orthod. 2020 Sep 14;21(1):32. doi: 10.1186/s40510-020-00333-5.
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.
由于扭转间隙的存在，预调整托槽会损失第三阶信息，这是临床正畸中的一个问题。本研究旨在评估槽高、弓丝高、宽度和边缘斜角半径对三种托槽/弓丝系统扭转间隙的影响。
选择三个厂家生产的带有 McLaughlin-Bennett-Trevisi 规格 0.022×0.028 in. 槽的 90 个托槽，使用轮廓投影仪测量槽的高度和深度。从三个不同厂家截取出 60 根不锈钢方丝，用 SEM 观察其高度、宽度和边缘斜角半径，记录数据并计算不同槽-弓丝组合的理论扭转间隙。采用单因素方差分析比较不同托槽类型之间和不同厂家之间的测量值。
槽高通常过大。弓丝高度通常过小，但也观察到过大的弓丝。边缘斜角半径是最易变的参数。一定程度的扭转间隙总是存在的，同一生产厂家的不同托槽类型之间存在差异，甚至在不同厂家之间差异可以翻倍。
由于生产公差，槽/弓丝系统任何部件的标称值和实际尺寸之间存在差异是很常见的。这导致了扭转间隙，限制了转矩的表达。弓丝的边缘斜角在转矩表达中起着重要作用，厂家应该提供更清晰的这方面的信息。
