Comparative assessment of frictional forces between differently designed esthetic brackets during simulated canine retraction.

Abstract

To evaluate force loss due to friction (FR) with an emphasis on esthetic brackets and their design differences during simulated canine retraction. The tested brackets were round and sharp-cornered conventional-ligating brackets and round-cornered self-ligating brackets. The tested archwires were stainless steel (0.018 × 0.025″ and 0.019 × 0.025″, and 0.018″) archwires. Atotal of 90bracket-archwire combinations in 9equally-sized groups (n = 10) were analyzed. Canine retraction was experimentally simulated in abiomechanical set-up utilizing the custom-made orthodontic measurement and simulation system (OMSS) using aNiTi coil spring that delivered aconstant force of 1 N. The simulated retraction path was up to 4 mm. FR was compared among groups using the Welch t‑test. Significance level(α) was set to 0.05. The round-cornered conventional-ligating bracket exhibited the least FR (28.6 ± 5.4%), while there were no significant differences in FR between the round-cornered conventional-ligating bracket and the round-cornered self-ligating bracket with 0.018″ stainless steel wires. However, the round-cornered self-ligating bracket exhibited the least FR (34.9 ± 5.1% and 39.3 ± 4.6%) with 0.018 × 0.025″ and 0.019 × 0.025″ stainless steel archwires, respectively. The sharp-cornered conventional-ligating bracket showed the highest FR of 72.4 ± 3.0% among the bracket systems tested in this study. The round-cornered conventional-ligating bracket showed less FR when compared to sharp-cornered conventional-ligating bracket. Conversely, the round-cornered conventional-ligating bracket exhibited greater FR when compared to the round-cornered self-ligating bracket, with an exception with respect to the 0.018″ wire. In general, FR increased with increased wire dimension.