| Objective:This in-vitro study was simulated oral circumstance to investigate that the influence of different temperature and the duration of time to the mechanical properties of four different nickel-titanium rectangular archwires, and which would provide some reference for its clinical application.Method:Four different kinds of rectangular nickel-titanium orthodontic archwires with same-sized (A:AO, B:L&H Titan, C:SMT, D:Grikin,0.016×0.022inch) were selected and tested by using a modified partial dental arch bending system with the Instron Universal Testing Machine.Experiment 1:test the 4 kinds of rectangular nickel-titanium orthodontic wires in the simulate oral environment.Selected the four different kinds of rectangular nickel-titanium orthodontic archwires,cut out of them to 40mm,there were 5 specimens of ervery kind archwire.Then tested them in 37℃artificial saliva with the Instron Universal Testing Machine,which can applied deflection of 3mm and then unloaded to the passive position, investigated the load-deflection characteristics of these different wires. The stress-strain curves of loading and unloading were derived.The following variables from unloading curves were calculated:stiffness from 0.5mm unloading deflection point(UDP) to 2.5 UPD, stress hysteresis.Experiment 2:test the 4 kinds of rectangular nickel-titanium orthodontic wires by the different ways of cold treatment.Selected the four different kinds of rectangular nickel-titanium orthodontic archwires,cut out of them to 40mm, there were 20 specimens of every kind archwire. Divided the specimens to a,b,c,d four groups with different ways to deal with:a group were soaked in 0℃water bath with 10s then transfered to 37℃artificial salivary with 5min; b group were soaked in 0℃water bath with 10s then transfered to 37℃artificial salivary with 1h; c group were soaked in 0℃water bath with 25h then transfeedr to 37℃artificial salivary with 5min; d group were soaked in 0℃water bath with 25h then transfer to 37℃artificial salivary with 1h. After that using Instron Universal Testing Machine applied deflection of 3mm and then unloaded to the passive position, investigated the load-deflection characteristics of these different wires. The stress-strain curves of loading and unloading were derived.The following variables from unloading curves were calculated:stiffness from 0.5mm unloading deflection point(UDP) to 2.5 UPD, stress hysteresis.Experiment 3:test the 4 kinds of rectangular nickel-titanium orthodontic wires by the different ways of heat treatment. Selected the four different kinds of rectangular nickel-titanium orthodontic archwires,cut out of them to 40mm, there were 20 specimens of every kind archwire. Divided the specimens to a,b,c,d four groups with different ways to deal with:a group were soaked in 60℃water bath with 10s then transfered to 37℃artificial salivar with 5min; bgroup were soaked in 60℃water bath with 10s then transfered to 37℃artificial salivar with 1h; c group were soaked in 60℃water bath with 25h then transfered to 37℃artificial salivar with 5min; dgroup were soaked in 60℃water bath with 25h then transfered to 37℃artificial salivar with 1h. Afer that using Instron Universal Testing Machine applied deflection of 3mm and then unloaded to the passive position, investigated the load-deflection characteristics of these different wires. The stress-strain curves of loading and unloading were derived.The following variables from unloading curves were calculated:stiffness from 0.5mm unloading deflection point(UDP) to 2.5 UPD, stress hysteresis. Statistically significant differences in these variables were analysed by one-way analysis of variance and factorial design material anova.Result:1. A,B,C archwires have superelasticity in the simulate oral environment,but the superelasticity of D archwire was't obvious.The stress of A archwire was least,the stress of D archwire was biggest.The hysteresises of 4 kinds of archwires were no significant difference,the unloading stiffiness had no significant difference between B,C archwires,and the lesat one was A archwire,the biggest one was D archwire. 2.The influence of 4ways of cold treatment to the A,B,C,D archwires was obvious during the loading.When the time of the cold treatment were the same,the change of mechanical of archwires were similar,the loading stress of the archwires would bigger with the longer time of the cold treatment.During the cold treatment,the hysteresis of A,C archwires were approximate at 10s-5min group,10s-1h group and 37℃group; the hysteresis of B archwire were approximate at 10s-5min group,10s-1h group, and which were smaller than 37℃group,the hysteresis were approximate at 25h-5min group and 25h-1h group,and which were bigger than 37℃group;the hysteresis of D archwire had significant difference in every group.A archwire had the smallest fluctuation of hysteresis under the different ways of cold treatment,D archwire had the biggest one.The unloading stiffiness of A archwire were approximate at 25h-5min group,25h-1h group and 37℃group;the unloading stiffiness of B,C archwires were approximate at 25h-5min group and 37℃group;the unloading stiffiness were approximate at 10s-1h group and 37℃group.In the same way of cold treatment,A archwire had smallest unloading stiffiness;in the different ways of cold treatment,A archwire had smallest fluctuation of unloading stiffiness.3. The influence of 4ways of heat treatment to the A,B,C,D archwires was obvious during the loading. During the heat treatment, the hysteresis of A,C archwires were approximate at 10s-5min group,25h-5min group and 37℃group; the hysteresis of B archwire were approximate at 10s-5min group and 37℃group; the hysteresis of C,D archwires were approximate at 10s-5min group and 25h-5min group. B archwire had the smallest fluctuation of hysteresis under the different ways of heat treatment,D archwire had the biggest one. The unloading stiffiness of A archwire were approximate at 10s-1h group,25h-lh group and 37℃group; the unloading stiffiness of B archwire were approximate at lOs-lh group,25h-5min group and 37℃group; the unloading stiffiness of C archwire were approximate at 10s-5min group and 25h-5min group; the unloading stiffiness of D archwire were approximate at 10s-5min group,25h-5min group and 37℃group. A archwire had the smallest fluctuation of unloading stiffiness. Conclusion:1. A,B,C archwires have certain superelasticity,but the superelasticity of D archwire was't obvious.There was no significant difference of hysteresis in the 4 kinds of NiTi archwires,the unloading stiffiness of D archwire was biggest.2. The influence of cold treatment to 4 kinds of archwires was obvious during the loading.The loading stress of archwires would bigger with the longer time of the cold treatment.The fluctuation of hysteresis and unloading stiffiness of A archwire were smallest in different ways of the cold treatment,that means A archwire had best stability.3. The influence of cold treatment to 4 kinds of archwires was obvious during the loading. The fluctuation of unloading stiffiness of A archwire was smallest in different ways of the heat treatment,and B archwire had the smallest fluctuation of hysteresis,which means A,B archwire had better stability;the fluctuation of unloading stiffiness and hysteresis of D archwire were biggest,which means the stability of D archwire was worst.4.A,B archwires can deliver forces continuously for two months or even longer,but D archwire was unsuited to use for long. |
PDF Full Text Request