Resistencia Al Deslizamiento En Autoligantes

Original Article

A comparison of resistance to sliding of self-ligating brackets under an increasing applied moment
Benjamin T. Pliskaa; John P. Beyerb; Brent E. Larsonc
ABSTRACT Objective: To test the null hypotheses that at clinically relevant amounts of applied moment, there are no differences in the amount of resistance to sliding (RS) between self-ligating (SL) and conventionallyligated (CL) brackets on both stainless steel (SS) and nickel-titanium (NT) archwire. Materials and Methods: Three different SL brackets and one CL bracket, all 0.0220 slot, were tested on a custom-built device to simulate canine retraction mechanics in the second-order dimension. The setup allowed for simultaneous and continuous measurement of RS and applied moment at the bracket-archwire interface.The brackets tested were Damon3, In-Ovation R, Smartclip, and Victory, all of which were tested with 0.0190 3 0.0250 SS and NT archwires. The RS at calculated moments of 2000 g-mm and 4000 g-mm was determined and compared between the various brackets and both archwire types. Descriptive measures, analysis of variance, and TukeyKramer post-test comparisons were used to calculate results. Results: Allbrackets displayed a greater amount of RS with NT than with SS archwires. At the higher moment levels (4000 g-mm), no significant reduction in RS was found between CL and SL brackets on both SS and NT archwires. At lower levels of applied moment (2000 g-mm), reductions in RS of 18% (42.7 g) and 18% (38.5 g) were found between the CL bracket and the best performing SL bracket on NT and SS,respectively. Conclusion: At low values of applied moment, some statistical differences were found; however, in general, the differences in RS amongst the various SL and CL brackets tested may not be clinically relevant. (Angle Orthod. 2011;81:794–799.) KEY WORDS: Friction; Self-ligating; Resistance to sliding

INTRODUCTION Contemporary fixed orthodontic treatment involves movement of a bracket alongan archwire. All such movements resulting in the contact of any two objects involve friction, thereby causing a resistance to sliding
a Assistant Professor, Division of Orthodontics, Department of Oral Health Sciences, University of British Columbia, Vancouver, British Columbia, Canada. b Associate Clinical Specialist, Division of Orthodontics, Department of Developmental and Surgical Sciences,University of Minnesota, Minneapolis, Minnesota. c Associate Professor and Director, Division of Orthodontics, Department of Developmental and Surgical Sciences, University of Minnesota, Minneapolis, Minnesota. Corresponding author: Dr Benjamin T. Pliska, Assistant Professor, Division of Orthodontics, Department of Oral Health Sciences, University of British Columbia, 2199 Wesbrook Mall, Vancouver,BC V6T 1Z3 Canada (e-mail: pliska@dentistry.ubc.ca)

Accepted: February 2011. Submitted: November 2010. Published Online: May 14, 2011 G 2011 by The EH Angle Education and Research Foundation, Inc.
Angle Orthodontist, Vol 81, No 5, 2011 794

(RS).1 Whether it is the initial unraveling of crowding or the sliding mechanics of space closure, friction is unavoidable in orthodontics. In the hopesof reducing patient discomfort and treatment time and improving efficiency of orthodontic tooth movement, several attempts have been made to reduce the friction involved in sliding mechanics. These include modifications of bracket2 and archwire materials,3 the addition of coatings or other treatment of material surfaces,4 alterations in the geometry of the bracket slot,4,5 or the use of noveldesigns of elastomeric ligatures.6 Currently one of the most heavily commercially advertised methods of reducing friction is the use of self-ligating (SL) brackets. There is a large body of research examining the RS of SL brackets in terms of bracket and wire material, dimensional and environmental variables, and mode of ligation.7 In the evaluation of frictional studies, a clear understanding of...