Assessment of friction resistance of four orthodontic arch wires using three ligation methods in dry and wet conditions

Abstract

Aim: Comparison of static and dynamic friction resistance of stainless steel (SS), nickel titanium (NiTi), titanium molybdenum alloy (TMA) and copper nickel titanium (CuNiTi) archwires using three different methods of ligation; St St ligature, Slide low friction elastics and conventional elastics in both dry and wet conditions. Materials and Methods: 144 new orthodontic arch wires were divided according to the alloy type into four groups with 36 archwires for each; group 1: stainless steel (SS), group 2: nickel titanium (NiTi), group 3: titanium molybdenum alloy (TMA) and group 4: copper nickel titanium (CuNiTi). Each group was divided according to the method of ligation into three subgroups with 12 archwires for each; subgroup A: ligated with SS ligature, subgroup B: ligated with Slide low friction elastics and subgroup C: ligated with conventional elastics. Static and kinetic friction resistance was measured using Lloyd Instruments in both dry and wet conditions by adding artificial saliva. Student t-test, ANOVA and LSD’s test were used for statistical analysis. Significance level was set at P≤ 0.05. Results: Student t-test showed static and kinetic friction for wet conditions were highly significant lower than dry conditions for the same arch wire/ligature cominations (P<= 0.001). Static and kinetic frictionresistance of SS archwires had significantly the least amount of friction followed by TMA then NiTi (Nitinol) and lastly CuNiTi. SS ligature exhibited significantly the least amount of friction followed by Slide low friction elastics while conventional elastics exhibited the greatest amount of friction (P<0.001). Conclusions: Wet conditions are essential for reducing friction in stainless steel bracket/archwire/ligature combinations. Stainless Steel archwire ligated to the SS bracket with SS ligatures exhibited the least amount of static and dynamic friction resistance followed by TMA and then NiTi and CuNiTi in an ascending order. SS ligature showed the least amount of friction followed by Slide elastomers and conventional elastic reported the highest friction resistance.