effect of fluoride on friction between bracket and wire

background: friction is usually encountered during sliding technique for orthodontic space closure. this study aims to investigate the effect of fluoride on frictional resistance between stainless steel orthodontic brackets and steel and niti arch wires. materials and methods: a total of 144 standard 022 stainless steel brackets were used in this experimental study. 0.016 and 0.019 × 0.025 inch steel and niti arch wires were tested. the frictional resistance between wires and brackets immersed in the following three solutions were measured: sultan fluoride gel containing 1.23% acidulated phosphate fluoride at ph 3.5 for 4 minutes, aquafresh mouth wash containing 0.05% sodium fluoride at ph of 5.1 for 1 minute twice a day for 8 weeks and physiologic serum (ph=7) as the control group. static and dynamic frictional forces were measured using testometric machine. surface topography of wires and brackets was qualitatively assessed using electron microscopy. three-way and two-way variance analysis and complementary tuckey analysis were applied to compare the groups for any significant differences ( p< 0.05). results: the average static and dynamic frictional forces for all bracket-wire combinations immersed in sultan fluoride gel were higher than those immersed in naf and control groups ( p< 0.001).the forces measured for rectangular wires were higher than round wires ( p< 0.001). frictional resistance of 0.016 inch niti wire was more than that of the steel one but the difference between steel and niti 0.019 × 0.25 arch wires was not significant. conclusion: friction between steel brackets and nickel titanium and steel wires is affected by prophylactic agents containing high doses of fluoride and acidity. key words: fluoride, friction, orthodontic bracket, sliding mechanics