| Objectives As for the discussion of appendages in invisible correction,a large number of scholars mainly focused on the influence of attachment size,retention force,degree of shedding,surface damage,etc.,while there were few studies on the influence of attachment position on the biomechanics of tooth movement.The experiment is aimed to provide a theoretical basis for reasonably designing accessories clinically when without braces stealth device moves in pushing molars to far through the establishment of maxillary alveolar bone and periodontal membrane and without braces maxillary teeth contact correctional implement three-dimensional finite element model and adhesive horizontal rectangle attachments in the different location of the maxillary first molar and three-dimensional finite element analysis to explore attachment location's influence on molar displacement tendency,tooth and the stress distribution of periodontal tissue in the process of invisible corrector far moving from maxillary molar.Methods 1 A few female patients with normal occlusion were selected.The third molars on both sides of the upper jaw were extracted,and the bone tissue in the tubercular area of the upper jaw was intact.2 CBCT quick scan was performed on the maxillofacial region of the patient to get The DICOM data and it together with modeling software such as Mimics20.0 Geomagic Studio12.0 was used to establish a three-dimensional finite element model of maxillary alveolar bone,periodontal membrane,maxillary dentition and invisible orthodontic device.3 Simulate the bonding of horizontal rectangular attachments at different positions of the right maxillary first molar and force the molar to move to the far center by 0.5mm.Group B: the horizontal rectangular attachment was placed in the buccal side of the tooth in the clinical crown center;Group C: the horizontal rectangular attachment was placed in the palatal clinical crown center of the tooth.Group D: the horizontal rectangular attachment was placed in the buccal palatal clinical crown center of the tooth.4 Hypermesh10.0 software was employed to obtain the data cloud map of tooth displacement and stress distribution of the tooth body and periodontal membrane in the four groups of experiments,and the results were analyzed.Results 1The three-dimensional finite element model of maxillary alveolar boneperiodontal ligament-maxillary first molar-bracketless invisible appliance established by CBCT scanning equipment and various computer software can meet the requirements of this experimental study.2 When the right maxillary first molar was forced to move 0.5mm distally,the result of the tooth displacement trend cloud showed that the movement of the teeth in Groups A and B was mainly tilted;the movement of teeth in group C was tilted with palate rotation;the tooth movement in Group D tends to move as a whole.3 Four groups of experimental tooth displacement results showed that during the distal movement of the molars,the teeth were relatively elongated in the mesentery,and the distal and middle teeth were relatively depressed,accompanied by crown and cheek tilt.4 The results of the tooth stress cloud diagram showed that the maximum stress of the first maxillary molar on the right side was also different according to the attachment position.The stress values of the four groups of experimental teeth were B>C>A> D.5 The stress distribution cloud image of the periodontal ligament showed that the stress distribution of the periodontal ligament of the right maxillary first molar in Group D was the most uniform.Conclusions 1The biological characteristics and material properties of the threedimensional finite element model of maxillary alveolar bone-periodontal ligamentmaxillary first molar-bracketless invisible appliance established by CBCT scanning technology and Mimics20.0,Geomagic Studio12.0 and other softwares better simulate the characteristics of the physical object its elf,which is conducive to experimental analysis.2When the invisible corrector push the molars to move distally,the horizontal rectangular attachment is placed in the center of the clinical crown of the buccal and palate sides of the teeth,and the teeth are more inclined to move overall,which is beneficial to the stable arrangement of the teeth.3 When the invisible corrector push the molar towards the middle,the horizontal rectangular attachment is placed in the center of the clinical crown of the buccal and palate sides of the tooth.Figure45;Table7;Reference 133... |
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