Pizzoni L, Ravnholt G, Melsen B
School of Orthodontics, University of Milano, Italy.
Eur J Orthod. 1998 Jun;20(3):283-91. doi: 10.1093/ejo/20.3.283.
Orthodontic tooth movement can be regarded as teeth sliding on a wire like pearls on a string, the force being supplied by springs or elastics. The movement implies friction between wire and bracket, taking up part of the force and leaving an uncontrolled amount to act on the teeth. The friction is likely to depend on bracket construction and wire material. Therefore, in this investigation the friction of self-ligating brackets and beta-titanium wires was evaluated, as opposed to more conventional configurations. Carried by low-friction linear ball bearings, a bracket was made to slide along an out-stretched archwire with minimal (and known) basic friction, either parallel or at an angle to the wire. Two self-ligating brackets were used in their closed position without any normal force. Friction was tested against four wires: stainless steel and beta-titanium, both in round and rectangular cross-sections. The force used to overcome friction and to move the bracket was measured on a testing machine at 10 mm/min, and the basic friction was subtracted. The results show that round wires had a lower friction than rectangular wires, the beta-titanium wires had a markedly higher friction than stainless steel wires, and friction increased with angulation for all bracket/wire combinations. The self-ligating brackets had a markedly lower friction than conventional brackets at all angulations, and self-ligating brackets, closed by the capping of a conventional design, exhibited a significantly lower friction than self-ligating brackets closed by a spring. The selection of bracket design, wire material, and wire cross-section significantly influences the forces acting in a continuous arch system.
正畸牙齿移动可被视为牙齿在钢丝上像串在绳子上的珍珠一样滑动，力由弹簧或弹力线提供。这种移动意味着钢丝和托槽之间存在摩擦，会消耗一部分力，从而使作用于牙齿的力变得不可控。摩擦力可能取决于托槽结构和钢丝材料。因此，在本研究中，对自锁托槽和β-钛丝的摩擦力进行了评估，与更传统的配置形成对比。一个托槽由低摩擦线性滚珠轴承支撑，使其沿着一根拉伸的弓丝滑动，基本摩擦力最小（且已知），滑动方向与钢丝平行或成一定角度。使用两个处于关闭位置的自锁托槽，且不施加任何法向力。针对四种钢丝测试摩擦力：圆形和矩形横截面的不锈钢丝和β-钛丝。在测试机上以10毫米/分钟的速度测量克服摩擦力并移动托槽所需的力，并减去基本摩擦力。结果表明，圆形钢丝的摩擦力低于矩形钢丝，β-钛丝的摩擦力明显高于不锈钢丝，并且对于所有托槽/钢丝组合，摩擦力随角度增加而增大。在所有角度下，自锁托槽的摩擦力均明显低于传统托槽，并且通过传统设计的盖帽关闭的自锁托槽，其摩擦力明显低于通过弹簧关闭的自锁托槽。托槽设计、钢丝材料和钢丝横截面的选择会显著影响连续弓系统中的作用力。
