Effect of different media on frictional forces between tribological systems made from self-ligating brackets in combination with different stainless steel wire dimensions

Abstract

The purpose was to determine the effect of different environments (artificial saliva, human saliva, distilled water, dry storage) on frictional forces between various tribological systems made from self-ligating brackets in combination with stainless-steel wires (dimensions: 0.016″×0.022″, 0.018″×0.025″ and 0.019″×0.025″). An universal testing-machine applied a normal force of 1 N. Two-way ANOVA and Tukey post-hoc tests (α=5%) were used. Saliva had significantly higher frictional forces (p<0.001). Yet, the influence of the media depends on the wire dimensions. The results were not as straightforward as in 0.018″×0.025″, which had a clear order (dry storage<water<artificial saliva<human saliva, p<0.001 each). Except for human saliva, wire dimensions differed significantly from each other (p<0.001). Increasing wire cross-sections increases frictional force. Thus, saliva acts as adhesive. High frictional forces of larger wires are attributed to the contact between latch and wire. Still, in-vitro experiments can only approximate the quasi-static tooth movement and the various fluids in the mouth.

Friction Force Adjustment by an Innovative Covering System Applied with Superelastic NiTi Brackets and Wires—An In-Vitro Study

“…Friction in brackets is known to be a complex and system-depending variable, with the main factors being bracket design and wire dimensions [2,[25][26][27][28]. High frictional forces hinder sagittal movement but allow for better anchorage, whereas tooth movement along the archwire is facilitated if low frictional forces are obtained [2,4,10]. According to the results presented in this study, frictional forces can be adjusted as needed during the phase of the orthodontic therapy by means of a corresponding polymeric covering clip.…”

“…Friction in brackets is known to be a complex and system-depending variable, with the main factors being bracket design and wire dimensions [2,[25][26][27][28]. High frictional forces hinder sagittal movement but allow for better anchorage, whereas tooth movement along the archwire is facilitated if low frictional forces are obtained [2,4,10].…”

“…The amount of frictional force provided by the bracket and its covering depends on the wire dimensions [2,29]. Based on the given covering design, friction can only be applied in combination with a slot filling V-shaped archwire.…”

“…A distinction must be made between physical and biological factors, both affecting friction. Wire properties, such as material, surface condition and stiffness, as well as the design of the brackets, e.g., the width or depth of the slot, the bucco-lingual angle between slot and bracket-base (i.e., torque) and the amount of the applied force are important [1][2][3][4][5][6][7][8]. The type of ligation, which creates a force between wire and bracket, also has a major influence on frictional forces [9,10].…”

“…While high frictional forces have a negative influence on the efficiency of tooth movement along the archwire, a high frictional force may, on the other hand, serve anchorage purposes and thus exhibit beneficial effects on the therapy. Depending on the treatment stage in orthodontics, single teeth and tooth segments must be moved with the lowest possible friction in contrast to teeth that are used for anchorage [2].…”