Frictional resistance of self-ligating versus conventional brackets in different bracket-archwire-angle combinations.

Maria Regina Guerra Monteiro,Carlos Nelson Elias,Oswaldo De Vasconcellos Vilella,Licinio Esmeraldo Da Silva

doi:10.1590/1678-775720130665

Abstract

ObjectiveTo compare the influence of archwire material (NiTi, beta-Ti and stainless steel) and brackets design (self-ligating and conventional) on the frictional force resistance.Material and MethodsTwo types of brackets (self-ligating brackets - Smartclip, 3M/Unitek - and conventional brackets - Gemini, 3M/Unitek) with three (0, 5, and 10 degrees) slot angulation attached with elastomeric ligatures (TP Orthodontics) were tested. All brackets were tested with archwire 0.019"x0.025" nickel-titanium, beta-titanium, and stainless steel (Unitek/3M). The mechanical testing was performed with a universal testing machine eMIC DL 10000 (eMIC Co, Brazil). The wires were pulled from the bracket slots at a cross-head speed of 3 mm/min until 2 mm displacement.ResultsSelf-ligating brackets produced significantly lower friction values compared with those of conventional brackets. Frictional force resistance values were directly proportional to the increase in the bracket/ wire angulation. With regard to conventional brackets, stainless steel wires had the lowest friction force values, followed by nickel-titanium and beta-titanium ones. With regard to self-ligating brackets, the nickel-titanium wires had the lowest friction values, significantly lower than those of other materials.Conclusioneven at different angulations, the self-ligating brackets showed significantly lower friction force values than the conventional brackets. Combined with nickel-titanium wires, the self-ligating brackets exhibit much lower friction, possibly due to the contact between nickel-titanium clips and wires of the same material.

Highlights

Tooth movement can occur when the applied forces adequately overcome the friction at the bracket slot-archwire interface
The influence of type of wire material and angulation on friction was analyzed separately for conventional and self-ligating brackets, allowing the behavior of these variables to be assessed in relation to both groups of brackets
With regard to conventional brackets, Mann-Whitney test showed statistic differences in the maximum friction force produced by stainless steel, nickeltitanium (p=0.011), and beta-titanium (p

Summary

Introduction

Tooth movement can occur when the applied forces adequately overcome the friction at the bracket slot-archwire interface. High levels of frictional force between the bracket slot and the archwire might cause binding between the two components; this in turn result in little or no tooth movement. It is essential to understand the friction between the bracket and the archwire so that the proper force can be applied to obtain adequate tooth movement and optimum biologic response. There has been increased use of the selfligating bracket. These brackets are characterized by having a “ligature” similar to an opening and closing cover or precision latch, avoiding the use of additional ligatures for attachment.

Methods

Results

Conclusion