An in vitro investigation of the influence of self-ligating brackets, low friction ligatures, and archwire on frictional resistance

This study, performed using a specially designed apparatus that included 10 aligned brackets, evaluated the frictional resistance generated by conventional stainless steel (SS) brackets (Victory Series), self-ligating Damon SL II brackets, Time Plus brackets, and low-friction ligatures (Slide) coupled with various SS, nickel-titanium (NiTi), and beta-titanium (TMA) archwires. All brackets had a 0.022-inch slot and the orthodontic wire alloys were 0.016, 0.016 x 0.022, and 0.019 x 0.025 inch NiTi, 0.017 x 0.025 inch TMA, and 0.019 x 0.025 inch SS. Each bracket-archwire combination was tested 10 times. Coupled with 0.016 inch NiTi, Victory brackets generated the most friction and Damon SL II the least (P < 0.001); with 0.016 x 0.022 inch NiTi, the self-ligating brackets (Time and Damon SL II) generated significantly lower friction (P < 0.001) than Victory Series and Slide ligatures; with 0.019 x 0.025 inch SS or 0.019 x 0.025 inch NiTi, Slide ligatures generated significantly lower friction than all other groups. No difference was observed among the four groups when used with a 0.017 x 0.025-inch TMA archwire. These findings suggest that the use of an in vitro testing model that includes 10 brackets provides information about the frictional force of the various bracket-archwire combinations.