An Experimental Study On Frictional Resistance And Torsional Efficacy Of Different Self-ligating Brackets

Objective:To investigate the difference of frictional resistance and torsional efficacy of variation combination of four kinds of self-ligating brackets(Damon3,SmartClip,Time2,and OPA-K) and four different archwires.Methods:1.Frictional resistance:The static and kinetic friction of four brackets(two passive self-ligating brackets -Damon3,SmartClip;and two active self-ligating brackets-Time 2, OPA-K) coupled with 4 types of archwires(0.019×0.025 inch nickel-titanium archwire, 0.019×0.025 inch stainless steel archwire,0.016×0.022 inch nickel-titanium archwire,and 0.014 inch nickel-titanium archwire) in the buccal segment in the dry(control group) and artificial saliva states(experimental group) were tested.2.Torsional efficacy:The torsional efficacy of four brackets(that mentioned above) coupled with 4 types of archwires(0.019×0.025 inch nickel-titanium archwire,0.019×0.025 inch stainless steel archwire,0.018×0.025inch nickel-titanium archwire,and 0.018×0.025 inch stainless steel archwire) were tested by torsion measurement instrument.Results:1.Frictional resistance:(1)There was significant difference of frictional resistance between experimental group and control group(P＜0.001);(2) In the artificial saliva state,there was significant difference of frictional resistance among the different self-ligating brackets (P＜0.05),except the static and kinetic friction of Damon3 self-ligating brackets and SmartClip self-ligating brackets,the static friction of OPA-K and Time2(P＞0.05)(3) There was significant difference of frictional resistance among 4 types of archwires,except 0.019×0.025 stainless steel archwire and 0.019×0.025 nickel-titanium archwire.2.Torsional efficacy:There was no significant difference of torsional efficacy between Damon3 and SmartClip self-ligating brackets,Time 2 and OPA-K self-ligating brackets(P＞0.05),but the others had significant difference(P＜0.05).(2) There was significant difference of torsional efficacy among the different archwire(P＜0.05),except 0.019×0.025 inch nickel-titanium archwire and 0.018×0.025 inch stainless steel archwire.(P=0.188)Conclusion:1.The frictional resistance of the self-ligating brackets was increased in the artificial saliva state.2.In comparison with the active self-ligating brackets,the frictional resistance and the torsional efficacy of the passive self-ligating brackets were obviously lower.3.The frictional resistance of archwire of the same material increased along with the enlargement of size.4.The torsional efficacy of archwire of the same material increased along with the enlargement of size.And the torsional efficacy of the stainless steel archwire was larger than that of the nickel-titanium with the same size.