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 of stainless steel brackets with different geometries and angulations,combined with orthodontic wires of different diameters. material and methods: the frictional forces were evaluated with three different types of metal brackets: a passive self-ligating (smartclip™,3m/unitek,monrovia,usa),with a modified slot design (mini uni twin™,3m/unitek,monrovia,usa) and conventional (kirium,abzil,são josé do rio preto,brazil). the samples were mounted in a testing device with three different angulations and tested with 0.014 and 0.018 stainless steel wires (american orthodontics,sheboygan,usa). the static frictional force was measured using a universal testing machine (dl 500,emic®,são josé dos pinhais,brazil) with a crosshead speed of 1 mm/min. statistical analysis was performed by two-way anova followed by bonferroni's post hoc test. results: there was a significant difference (p<0.05) in static friction when the three types of brackets were tested with the same wire size. the wire diameter influenced friction only when the brackets had a 10° angulation (p<0.05). the angulation influenced friction (p<0.05) when the brackets were associated with a 0.018 wire. conclusion: brackets with a modified slot design showed intermediate static frictional force values between the conventional and self-ligating brackets tested.