Evaluation of the behavior of different brackets on frictional forces during sliding mechanics

Abstract

Objective: The purpose of this study is to compare, in vitro, the resistance to sliding generated by conventional, active self-ligating and passive self-ligating brackets with stainless steel and nickel-titanium wires and to evaluate the effect of binding upon resistance to sliding In addition to this, the influence of bracket´s slot surface characteristics on measured friction was estimated. Materials and Methods: The following 0,022 inch slot brackets were essayed: Damon® Q™, Prodigy SL™ (Sybron Dental Specialties Ormco™, Orange, California, USA), Smart-Clip™SL3, Victory Series™ (3M Unitek Orthodontic Products, Monrovia, California, USA), Morelli® Roth Standard and Morelli® Roth SLI (Morelli Ortodontia, Sorocaba, São Paulo, Brazil). These brackets were coupled with either 0.016 x 0.022 inch stainless steel (Dentaurum GmbH, Ispringen, Germany) or nickel-titanium (DM Ceosa, Madrid, Spain) archwires. Alicona InfiniteFocus® optical 3-dimensional micro coordinate system (Alicona Imaging GmbH, Grambach/Graz, Austria) and Alicona IFM version 3.5.1.5 software (Alicona Imaging GmbH, Grambach/Graz, Austria) were used for assessing roughness average, root mean square and mean peak to valley height of roughness profile of slot surface. For Damon brackets, a slot profile analysis was executed in order to evaluate the contact areas between bracket and archwire Results: Statistically significant higher resistance to sliding is observed in conventional brackets comparing to passive and active self-ligating brackets. No statistically significant differences were found between passive and active self-ligating brackets and between archwire materials in 0 degrees angulations. For 5 degrees angulations, stainless steel showed statistically significant higher resistance to sliding. No statistically significant differences in resistance to sliding were found between 0 and 5 degrees of bracket tipping. Higher values of roughness average and root mean square were correlated with friction forces lower than 3N while lower roughness values were associated with higher frictional forces. In Damon brackets, the embossed numbers in the slot are not likely to contact with the archwire since they are approximately 5.5μm lower than the lateral boxes. Conclusion: Self-ligating brackets are helpful for obtaining low frictional forces. When coupled with a small rectangular archwire, slight bracket angulations or tooth tipping may not influence resistance to sliding. However, different alloys reveal dissimilar frictional behavior when angulations are present. Surface roughness seems to have an inverse correlation with frictional forces.