An Experimental Research On The Influnce Of Different Recycling Methods Of Brackets On Their Frictional Resistance

Objective:The purpose of this paper is to discuss the effect of different bracket recycling methods on the frictions between bracket slots and arch wires and the changes of slot glossiness.Method:This test uses 90 upper central incisor stainless steel square wire arch brackets from A and B companies. Divide them into 5 treatment groups at random with 18 brackets in each group. The first group is kept untreated as cross reference; The second group is treated by sand blasting (sand blasting group); The third group is sintered by spirit lamp (sintered group); The fourth group is treated with heat and cleaned by ultrasonic wave after the heat treatment (heat-ultrasonic group); The fifth group is treated by electrolysis polishing after heat treatment and ultrasonic wave cleaning (heat -ultrasonic-electro group). Use 0.019X0.025 in. stainless steel square wire and 0.018 in. stainless steel round wires and divide every one of the five treatment groups into 2 groups. Take one at random from each group to observe the slot glossiness. Use Instron universal dynamometer to measure the static and kinetic frictions between brackets and arch wires and observe the roughness of the slots of the brackets after different treatments with scanning electron microscope.Results:1.For brackets of the same company, no matter the square wire group or the round wire group, the static and the reference group and sand blasting group have no statistical significance (P>0.05).2.For the sintered group,"A"brackets, no matter the square wire group or round wire group, have larger static and kinetic frictions than that in reference group and other groups, and they have statistical significance(P<0.05). For square wire"B"brackets, the data of static and kinetic frictions in the sintered group, comparing with those of frictions in reference group, have statistical significance (P<0.05); But for the round wire"B"brackets in sintered group, the data of static and kinetic frictions, comparing with those of frictions in reference group, have no statistical significance(P>0.05).3. For"A"brackets, the static and kinetic frictions in heat-ultrasonic group are obviously larger than those in reference group. The data have distinct statistical significance (P<0.05). For"B"brackets, the data of the static and kinetic frictions in heat-ultrasonic group, comparing with the reference group, have no statistical significance(P>0.05).4. For"A"brackets, the static and kinetic frictions after heat, electrolysis and ultrasonic treatment are obviously smaller than those other groups. The data have distinct statistical significance (P<0.05), For"B"brackets, the data of the static and kinetic frictions and those of reference group have no statistical significance (P>0.05).5. It can be observed from scanning electron microscope: for"A"brackets, there are small protrusion in the slots of reference group and sand blasting group brackets, small granules can be seen in sand blasting group brackets; there are large amount of irregular isles and deep large gully in sintered group brackets; there are irregular deep gully on the surface of brackets in heat-ultrasonic group; the surface in heat-electro-ultrasonic group is smoother than that of reference group but slight interlaced cracks can be seen. For"B"brackets, the ones in reference and heat-ultrasonic groups are smooth and flat; There are small granules in sand blasting group brackets; there are small protrusions in the slot of sintered group brackets and large amount of slot pits can be found in heat -ultrasonic-electro group brackets.Conclusions:1. For"A"brackets, the frictions have no distinct changes after sand blasting; they increase in the sintered group and heat-ultrasonic group and decrease in heat-electro-ultrasonic group.2. For"B"brackets, the fictions have no distinct changes in any of the groups.3. The frictions between"A"brackets and arch wires are larger than those between "B"brackets and arch wires in sand blasting group, sintered group and heat-ultrasonic group. But there is no distinct difference between the two in heat -ultrasonic-electro group.