Comparison of static friction with self-ligating,modified slot design and conventional brackets

Objective

To compare the static frictional forces generated at the bracket/wire interface ofstainless steel brackets with different geometries and angulations, combined withorthodontic wires of different diameters.

Material and Methods

The frictional forces were evaluated with three different types of metal brackets:a passive self-ligating (SmartClip^TM, 3M/Unitek, Monrovia, USA), with amodified slot design (Mini Uni Twin^TM, 3M/Unitek, Monrovia, USA) andconventional (Kirium, Abzil, São José do Rio Preto, Brazil). The samples weremounted in a testing device with three different angulations and tested with0.014" and 0.018" stainless steel wires (American Orthodontics, Sheboygan, USA).The static frictional force was measured using a universal testing machine (DL500, EMIC^®, São José dos Pinhais, Brazil) with a crosshead speed of 1mm/min. Statistical analysis was performed by two-way ANOVA followed byBonferroni''s post hoc test.

Results

There was a significant difference (p<0.05) in static friction when the threetypes of brackets were tested with the same wire size. The wire diameterinfluenced friction only when the brackets had a 10º angulation (p<0.05). Theangulation influenced friction (p<0.05) when the brackets were associated witha 0.018" wire.

Conclusion

Brackets with a modified slot design showed intermediate static frictional forcevalues between the conventional and self-ligating brackets tested.