Abstract
ObjectiveThe aim of this article was to assess how intraoral biodegradation influenced the surface characteristics and friction levels of metallic brackets used during 12 and 24 months of orthodontic treatment and also to compare the static friction generated in these brackets with four different methods of the ligation of orthodontic wires.Material and MethodsSeventy premolar brackets as received from the manufacturer and 224 brackets that were used in previous orthodontic treatments were evaluated in this experiment. The surface morphology and the composition of the deposits found in the brackets were evaluated with rugosimetry, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Friction was analyzed by applying tensile tests simulating sliding mechanics with a 0.019x0.025" steel wire. The static friction levels produced by the following ligation methods were evaluated: loosely attached steel ligature around all four bracket wings, steel ligature attached to only two wings, conventional elastomeric ligation around all 4 bracket wings, and non-conventional Slide® elastomeric ligature.ResultsThe results demonstrated the presence of biodegradation effects such as corrosion pits, plastic deformation, cracks, and material deposits. The main chemical elements found on these deposits were Carbon and Oxygen. The maximum friction produced by each ligation method changed according to the time of intraoral use. The steel ligature loosely attached to all four bracket wings produced the lowest friction levels in the new brackets. The conventional elastic ligatures generated the highest friction levels. The metallic brackets underwent significant degradation during orthodontic treatment, showing an increase in surface roughness and the deposit of chemical elements on the surface.ConclusionThe levels of static friction decreased with use. The non-conventional elastic ligatures were the best alternative to reduce friction.
Highlights
Orthodontic tooth movement (OTM) efficiency is influenced by both biological and mechanical variables, and friction is one of the most studied due to its complexity and importance
OTM occurs when the orthodontic forces applied to the teeth are higher than the static friction[22]
Sample and groups The present study evaluated the static friction of metallic brackets as received from the manufacturer and after their intraoral use during 12 or 24 months of orthodontic treatment in a private office
Summary
Orthodontic tooth movement (OTM) efficiency is influenced by both biological and mechanical variables, and friction is one of the most studied due to its complexity and importance. OTM occurs when the orthodontic forces applied to the teeth are higher than the static friction[22]. Some physical variables interfere in the friction magnitude, such as the type of bracket and wire material[14], the angle of insertion of the wires[2], the surface characteristics[11], geometry and dimensions of these materials[22], as well as the type of ligature[12] and method of ligating the wire to the brackets[13]. It is impossible to fully eliminate friction in sliding mechanics. The so-called low friction systems[22], such as self-ligating brackets[22], have been gaining ever-greater space in the orthodontic product market[18], despite their higher costs[22].
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