Frictional Properties of Self-Ligating Brackets and Low-Friction Ligatures

Problem statement: To evaluate the frictional forces generated by five different orthodontic brackets when used in combination with stainless steel and NiTi archwires in dry conditions at physiological temperature. Approach: Five different types of maxillary canine brackets (Damon 3 MX, Step, Quick, Sprint, Mini Mono) with a slot size 0.022 inch were coupled with 0.016” and 0.019”×0.025” stainless steel and with 0.016” and 0.018”×0.025” NiTi archwires. Step, Sprint and Mini Mono were used both with traditional ligatures and with Slide ligatures. A total of 320 archwires and brackets were used; ten tests were carried out for each group of bracket-wire combination at physiological temperature and in dry state. Frictional forces were measured by Instron Universal Testing Machine. The statistical significance level was established at P<0.05. Results: Damon 3 MX and Step brackets with Slide ligatures produced statistically lower friction than Quick and conventional brackets with elastomeric ligature. Frictional force increased proportionally to the wire size; NiTi archwires presented higher frictional resistance than stainless steel archwires. Slide ligatures showed lower fictional values in comparison with elastic ligatures. Conclusion: Stainless steel brackets with new Slide ligature show frictional forces similar to self-ligating brackets with passive clip.