| ObjectiveThe four-curved auxiliary arch is currently used in clinical practice has good clinical application effect,but the manual bending is not easy to control the loading of the torque force.Therefore,it is necessary to further study the the four-curved auxiliary arch to biomechanical properties of the periodontal membrane.Excessive moment force causes periodontal stress response,which provides a reliable basis for the further promotion and application of the four-curved auxiliary arch in clinical practice.Studying the change of the torque of the four-curved auxiliary arch caused by the change of the upper central incisor and the periodontal ligament reaction can provide a theoretical basis for the safety of the clinical use of the auxiliary arch.Method1.Three dimensional finite element model was used to analyze the effects of different torque forces on the displacement of upper central incisor and the stress of periodontal membrane(1)A three-dimensional finite element model of four-curved auxiliary arch acting on upper teeth was establishedCBCT was used to establish the head model of normal occlusal patients,and then the Mimics software was used to divide the data into three-dimensional models.Then,a rough three-dimensional finite element model was generated,and the model was trimmed by Geomagic software,and finally a smooth model matching the solid model was generated.After the model is established,four-curved auxiliary arch,stainless steel wire,bracket,micro-implant,etc.are drawn in the computer software.After combining,the analysis software ANSYS is used to mesh each unit,and the unit attribute is set for the combined part,carry out the calculation of the load.(2)Analysis of displacement and periodontal ligament stress of maxillary incisors by four-curved auxiliary arches with different torque force controlIn the absence of the extraction space and the extraction of the interdental space,the same stable anchorage method applies different torque forces,the cutting end of the maxillary central incisor and the apical displacement and the biomechanical reaction of the periodontal membrane,so according to different anchorage,different torque The moment loading method is divided into two groups of models,including the following 16 types of conditions:Group A: The traction hook and the ipsilateral maxillary first molar buccal tube wererigidly ligated to stabilize the main archwire with a ligation wire.(no tooth extraction)A1: 0.5N;A 2:1N;A3:1.5N;A4:2NGroup B: The traction hook and the ipsilateral micro-implants were rigidly ligated to stabilize the main archwire with a ligation wire.(no tooth extraction)B1: 0.5N;B2:1N;B3:1.5N;D4:2NGroup C: Elastic hooking of the traction hook and the ipsilateral maxillary first molar buccal tube(tooth extraction :1.15 N traction force)C1: 0.5N;C2:1N;C3:1.5N;C4:2NGroup D: Elastic hooking of the traction hook and ipsilateral maxillary micro-implants(tooth extraction : 1.15 N traction force)D1: 0.5N;D2:1N;D3:1.5N;D4:2NThe adaxial traction of the maxillary anterior teeth is set to 1.15 N per side.2.Mechanics study on different bending modes of four-curved auxiliary archThe four-curved auxiliary bow is made of a 0.018-inch(0.457 mm diameter),with a total of four long-axis bending forces were applied.The auxiliary arch is placed on the archwire from the bottom of the front bracket.4 The long-axis curve protrudes from the far middle to the center of the tooth,close to the center of the impedance.When the torque force is applied,the magnitude of the applied force can be judged according to the length of the long axis of the auxiliary arch and the tilt angle of the tilt.Therefore,when increasing the strength,special attention should be paid to the change of the angle of the auxiliary arch.The larger the angle,the greater the torque force applied by the auxiliary arch.In the long axis of the curve,the length of the curve is 5mm,6mm,7mm,and the four curves are inclined to the side of pressed down by about15°,20°,25°,30°,35 °to bend the new torque auxiliary bow,and finally bend into different lengths and The new torque auxiliary arch of the angle is placed on the orthodontic standard model and the force value is measured with a dynamometer.Result1.Finite element model analysis of displacement and periodontal stress of upper central incisor by different torque forces(1)Instantaneous displacement direction and size of teethA group: no tooth extraction,the traction hook and the ipsilateral maxillary first molar buccal tube hard ligature stabilize the main archwire with the ligation wire,the movement trend of the teeth of the four groups is: Under the action of torque force,maxillary incisors produce lip movement and incisal tongue displacement.With the increase of the torque force,the tooth cutting end displacement is arranged from large to small :A4>A3>A2>A1;The tooth root end displacement from large to small is also :A4>A3>A2>A1;The displacement difference between cutting tips and root tips of the 4 groups: A4>A3>A2>A1B group: the traction hook and the ipsilateral micro-implant were used to stabilize the main archwire with the ligation wire.The B group conclusion is similar to the A group conclusion.The displacement of the tooth end is arranged from large to small: B4>B3>B2>B1;the root displacement of the teeth from large to small is also B4>B3>B2>B1;4 groups of cut end-root tip displacement difference: B2>B4>B3>B1,the A group and the B group cut The displacement of the cutting end is A1>B1、A2>B2、A3>B3、A4>B4,and the root displacement is A1>B1、A2>B2、A3>B3、A4<B4C group: the tooth extraction gap is not closed group,(1.15 g traction)traction hook and the ipsilateral maxillary first molar buccal tube.The displacement of the cutting end of the tooth is arranged from large to small :C4>C3>C2>C1;the displacement of the root end of the tooth is also from :C4>C3>C2>C1;the displacement of the cutting end-root tip of 4 groups: C4>C3>C2>C1D group: the tooth extraction gap is not closed group,(1.15 g traction)traction hook and the ipsilateral micro-implant.The trend of tooth movement in the 4 groups was consistent with the C group.The displacement of the cut end of the tooth is arranged from large to small :D4>D3>D2>D1;the displacement of the root end of the tooth is also from :D4>D3>D2>D1;the cut end-root tip displacement difference of 4 groups: D4>D2>D1>D3;the displacement of the incisors in the third group and the fourth group: C1<D1、C2<D2、C3<D3、C4<D4,root displacement comparison: : D1<C1、D2<C2、D3<C3、D4<C4(2)periodontal membrane stress distributionA group : A1、A2、A3、A4 group periodontal membrane stress are concentrated in the neck of the teeth,the periodontal membrane stress value range of the root tip is small,A 1,A 2group lip side teeth periodontal membrane The stress value is close to 26 KPa.The stress values of the periodontal membrane of the labial region of the A3 and A4 groups are more than 26 KPa.There is no obvious excessive periodontal membrane stress response at the apex and other positions.B group: the group of B1 、 B2 、 B3 、 B4 group periodontal membrane stress concentration is the same as the A group,the B1,B2 group lip side tooth periodontal membrane stress value is less than 26 KPa,B3 group lip side The periodontal membrane stress value of the tooth neck is close to 26 KPa,the B4 group exceeds the periodontal membrane stress value range,and the apical and other positions have no obvious excessive periodontal membrane stress response.C group: the group of C1、 C2、 C3 、 C4 group periodontal membrane stress concentration is the same as the first group,C1、C2 lip side teeth periodontal membrane stress value is close to 26 KPa,C3,C4 exceeds the teeth Peripheral membrane stress,no excessively large periodontal membrane stress response at the apex and other locations.D group: similar to the C group,the D3 group exceeded the periodontal membrane stress value,and the apical and other positions did not have excessively large periodontal membrane response.2.Mechanical analysis of different bending modes of four-curved auxiliary bowThe four-curved auxiliary bow is made of a 0.018-inch(0.457 mm diameter)round stainless steel wire,which is found that in the mechanical test of the four-curved auxiliary bow in different bending modes:with the increase of the tilt angle of the twisting direction,the torque The force value gradually increases;for every 5° increase,the force value increases by about 48 g,and when the applied force length increases by 1-2mm,the torque force value is not affected.Therefore,in clinical application,the applied torque force can be judged according to the increased angle of the clinic,and the root force absorption phenomenon occurs when the force is excessively applied.conclusion1.When the tooth extraction gap is not closed,as the torque force value increases,the cutting end and root tip displacement of the molar ligation group are larger than the implant ligation group,and the displacement of the cutting end of the molar ligation group greatly exceeds the implant return.Grouped.Therefore,when the tooth extraction is closed,the implant ligation group can better control the root movement when different torque forces are applied,and the cutting edge is not excessively lip-tilted.2.When the tooth extraction gap is not closed,the cutting end displacement of the implant body is slightly larger than that of the molar recovery group.The root tip displacement is similar under the force of each force value or the molar group is slightly larger than the implant body.When the tooth extraction gap is not closed,different torque forces are applied,and the molar closes tooth extraction clearance group and the implant closes tooth extraction group can better control the root movement so that the anterior cut ends are not excessively lip-dipped.3.When the tooth extraction gap is closed,the torque auxiliary arch can apply a torque force of less than 1N when the molar ligatuion to traction hook,and a torque of 1.5N can be applied when the implant ligatuion to traction hook,so before using the torque auxiliary arch control When the tooth torque is used,it is best to choose the implant ligature to control the anchorage.4.When the tooth extraction gap is not closed,whether the molars are used to adduction the anterior teeth or the implants adduction the anterior teeth,the torque of the auxiliary arch can be applied less than 1N,so 1N is the safe range that the torque auxiliary arch can controlled.5.When the four-curved auxiliary arch exerts force,the root tip does not exceed the periodontal membrane stress response,so the torque auxiliary arch will not cause the absorption of the root tip.6.The length of the four curved auxiliary bow lines is increased or decreased by 1-2 mm,which does not affect the application of the torque force value.At the same length,the force arm force is increased by about 48 g for each 5° increase in the tilt of the gibbon,and the clinically required force can be evaluated within this range. |
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