Finite Element Study On The Control Of Molar Anchorage By Physiological Anchorage Technique

Objective:The three-dimensional finite element model of maxillary dentition physiological anchorage control orthodontic system at different orthodontic stages was established and the related data of maxillary first molar during orthodontic treatment were detected to explore the biomechanical principle of physiological anchorage orthodontic technology and evaluate the protective effect of physiological anchorage technique on molar anchorage.Materials and Methods:Find a qualified patient with individual normal occlusion.After CBCT imaging data obtained,import the data into mimics15.0.According to the difference of the grayscale between bone tissue and dental tissue,reconstruct the maxillary and dental models and use Geomagic Studio10 reverse engineering software to optimize the jaw and dental models.Use CATIA software to establish the models of periodontal membrane,physiological anchorage appliance,arch wire and traction hook.Establish the finite element models of physical anchorage in the early stage of orthodontic treatment(simulating the working condition of circular wire entering the buccal canal),the leveling stage(simulating the working condition of rocking chair bow wire entering the buccal canal)and the sliding adduction stage respectively.After cell division and parameter set,establish coordinate system(x axis for horizontal direction,y axis for sagittal direction,z axis for vertical direction);the elastic force of the arch wire in the early stage of orthodontic treatment and in the stage of orthodontic treatment should be calculated respectively and then load the model,thus deriving the displacement trend and initial displacement of teeth.In the model of sliding adduction stage,150 g sliding adduction force is applied to derive the displacement of the first molar at different angles.Result:The three-dimensional finite element model of the physiological anchorage controlled orthodontic appliance for maxillary dentition was established in the early stage of orthodontic treatment,the stage of row leveling and the stage of sliding adduction,includingmaxilla and dentition model,periodontal membrane model,bracket model,arch wire model and traction hook model.1.In the three-dimensional finite element model of the physiological anchorage orthodontic system of maxillary dentition at the initial stage of orthodontic treatment,the maxillary first molar shows the dental crown moving towards the buccal side on the X axis;the dental root moving toward the middle,the dental crown moving away to the middle,and they rotating clockwise on the Y axis;a slight elongation of the teeth happening near the middle and lowering down slightly in the far on the Z axis.In addition,we also observed that on the Y-axis,the fangs tended to move farther away.2.In the three-dimensional finite element model of the physiological anchorage orthodontic system of maxillary dentition at the stage of alignment,the maxillary first molars show that the teeth have shifted sideways in the cheek on the X axis;the dental root moving toward the middle,the dental crown moving away,and they rotating clockwise on the Y axis;some reduction of the teeth happening on the Z axis.3.In the three-dimensional finite element model of the physiological anchorage orthodontic system of maxillary dentition at the sliding adduction stage,after the maxillary first molar tilts backward,the proximal and medial displacement of the molar decreases significantly when the maxillary first molar is pulled forward.Conclusion:1.In the three-dimensional finite element model of the physiological anchorage orthodontic system of maxillary dentition at the initial stage of orthodontic treatment,under the force of the arch wire,the maxillary first molars take a tendency of moving the dental crown to the far and the root to the near and clockwise rotation,which makes the molars in the backward state and has a protective effect on the anchorage molars.In addition,it was observed that the fangs were also subjected to a tendency of distancing,which accelerated the rapid alignment of the front teeth and saved the rear teeth anchorage.2.In the three-dimensional finite element model of the physiological anchorage controlled orthodontic system of maxillary dentition at the stage of alignment,under the action of arch wire,the dental root of the maxillary first molar moves toward the near and the dental crown moves toward the far,which has a protective effect on the molar anchorage.3.In the three-dimensional finite element model of the physiological anchorage controlled orthodontic system of maxillary dentition at the sliding adduction stage,the displacement of the maxillary molars under the sliding adduction force at different angleswas detected.After anchorage prepared,the proximal displacement of the molars was significantly reduced and the anchorage of the molars was significantly increased.