The Three Dimensional Analysis Of Torsional Property Of The Conventional And Passive Self-ligating Brackets

Objective: In this test,through the establishment of the three dimensional finite element model of conventional and passive self-ligating brackets which assembled a single Nickel-Titanium round wire to analyze the differences of torsional property of these brackets.At the same time,the passive double colpus of self-ligating bracket is assembled auxiliary arch wire in view of the torsional property to study.So as to explore the characteristic and regularity of the torsional property of the different kinds of brackets,and the characteristics and advantages of the passive double colpus of self-ligating bracket applied to the technology of double wires.Method:1.Using the Pro/Engineer Wildfire5.0 to draw the mental brackets,such as HX,MUT,3M,Damon Q,which including the central incisor,lateral incisor,and canine of each one.And to draw the nickel-titanium wires with 30 mm length,including 0.012 inch,0.014 inch,0.016 inch,0.018 inch,0.014×0.025 inch and the ligature wire which is corresponding to the different size of the arch wires.At the same time,establishing elements in the Pro/E,the brackets,ligature wires and arch wires are imported to assemble the model which is containing single and double wire solid models.The number of the experimental model groups is twenty nine.2.After copying the model into STEP format,importing to the MSC.Marc.Patran 2005R3 software,the brackets,ligature wires(or sliding cover)and arch wires are mesh division respectively.At last,after collecting the node and element,the files are exported by the IGS format.3.Importing the IGS format files which exported from the MSC.Marc.Patran 2005R3 software into the MSC.Marc.Mentat 2010R3,the relevant parameter is set to accomplish the establishment of the three dimensional finite element models.4.The experiment is divided into two parts: experiment 1 is a comparative study which is the torsional property of the conventional and passive self-ligating brackets.It means that all the models assembled by single wire are compared to each other.The number of the experimental model groups is sixteen.Experiment two is a comparative analysis about the torsional property of the passive double colpus of self-ligating brackets.That is to say,the models assembled by single and double wires respectively are compared with each other.The number of the experimental model groups is seventeen.5.After getting the three dimensional finite element models,the models are set to corresponding parameters successively.The boundary of brackets of the central incisor and canine are fixed subsequently.Finally,the brackets of the later incisor are chosen a point that is near the mesial side slightly to load the power of torsion 20 degree.6.After collecting the data,it is drawn into the corresponding curve.And then the results of experiments are compared to analyze and discuss.Result: 1.The result is gotten by the first experiment: While the type of brackets and the size of arch wires is the same,the torsional angle is possibility associated with the torsional values.With the type of brackets and the torsional angle unchanged,the torsional value is increased with the size of arch wires.What is more,while the size of wires and torsional angle is not changed,the groups of Damon Q are gotten the minimum torsional values.The torsional values of HX are max.The torsional values of the experimental groups of MUT are close to the HX's.Under the each size of arch wire,the torsional values are little less than HX's.Moreover,the torsional values of experimental groups of 3M are between the MUT's and the DamonQ's.The torsion/angle graphs are drawn by all of the experimental group data: from the trend of the graphs integrally,the torsional values are present certainly regularity that HX>MUT>3M>DamonQ.The experiment groups of MUT and HX are beginning to appear the curve inflection points.With the increase of arch wire size,the groups of the DamonQ are starting to appear the inflection points respectively in the 12°,9.6°,8.4° and 7.6°.The 3M's inflection points are appeared respectively in the 8.4°,6°,5.2° and 4.4°.From the stress diagram,while the later incisor bracket is rotated,the stress is concentrate mainly on the near edge of middle brackets.2.The result of the experiment 2 is that: Whether it is the experimental groups of single wire or the groups of double wire,the torsional value is proportional to the torsional angle.In addition,it is increase with the size of arch wire.To use the same size of wire in the main colpus,the groups of single wire is gotten the smaller torsional values compared with the groups of double wire,which having a multiple relationship between them.While the main arch wire is not the same,except for the arch wire size is 0.018 inch the torsional value of groups of single wire is greater than the groups of double round wire such as the groups of 0.012+0.012NiTi?0.014+ 0.012 NiTi double round wire,the rest of the groups of single round wire is less than the groups of double round wire.And when the main arch wire size is 0.014×0.025 inch,the torsional value of this single rectangular wire is obviously greater than all of the groups of single round wire and double round wire.In the experimental groups of double round wire,when the sum of the main wire size with the auxiliary arch wire size add together is the same,the greater difference of the arch wire size to choose,the less torsional value will be gotten.The graph shows that the curve inflection point angle of groups of double wire is less than the groups of single wire.3.Compared with experiment 1 and experiment 2.The DamonQ and 3M is the passive self-ligating brackets.While compared with the experimental groups of the DamonQ double round wire,in addition to the torsional value of the groups of 3M that assembled 0.018 inch round wire is greater than the group of 0.018+0.012 NiTi double round wire,the groups of single wire are less than the groups of the double wire.The graphs show that the curve inflection point angle of the 3M is between the groups of single wire and double wire.Compared with the conventional brackets,except of the 0.012 inchNiTi round wire,the torsional value of MUT and HX assembled with the other size of single arch wires is greater than part of the groups of double wire.While the size of arch wire is 0.018 inch,the torsional value of MUT and HX only less than the DamonQ assembled with the 0.018+ 0.016 NiTi double round wire.From the graphs,it shows that the curve inflection point angle of the HX and MUT is smaller than the groups of double round wire.Conclusion: 1.The torsional value of brackets is closely related to the length of groove,the method of ligation,the size of arch wire and so on.2.The torsional property of the conventional brackets is obviously higher than the passive self-ligating brackets.And the torsional property of DamonQ assembled single round wire is the worst.3.The DamonQ assembled with the double wire has more advantages than the groups of single wire.If using the assistant-horizontal colpus logically,it will be good for the passive self-ligating brackets to correct the rotated teeth.4.In practical clinic application,we should be based on the patients' situation to choose the suitable brackets or the proper match of arch wire so that the torsional control can be gained more efficiently and stably.