Three-dimensiona Finite Element Analysis Of Child Maxillary Complex Of Rapid Maxillary Expansion

Objective: Rapid maxillary expansion (RME) is a significant orthodontic method which is being used to treat the transverse discrepancy of maxilla, bow narrow maxillary teeth, against tooth and posterior teeth and remove maxillary teeth column crowded. RME orthodontic force acts on maxillary teeth,alveolar bone or other maxillary organizations. In a short time to exert greater orthopaedic to maxillary organization to expand maxillofacial bone sutura, thereby maxillary width expanded. The increase of maxillary width mainly includes maxillary basal bone expansion and the expansion of maxillary teeth width. Previous researcher has suggested that the nasal cavity crosswise width was increasing, anchorage odontic lean and extend when appliance was expanding maxillary dental arch speedly. Some patients on clinical treatments reflected the nasal frontal appeared pain and eye socket broaden in rapid expansion. It is worth to orthodontic researchers to ponder earnestly of how to have a comprehensive understanding about Hyrax dynam distribution characteristics and reduce ill-effect.Involving RME maxillary compound and neighboring tissues, mechanical mechanism is very complicated. Finite element method (FEM) is a kind of collection to solve the efficient continuous physical learning problems by numerical method. Brekelmans and Rybicki, for the first time, 3-d finite element (Three - dimensional finite element of 3-d FEM) is applied to the experiments in medical biomechanics field in 1972, now this method has been widely used in oral biomechanics research field.In the biomechanical study methods, as the Rapid expansion is unique mechanics analysis simulation characteristics, it is widely adopted by the domestic and international orthodontic researchers. However, due to the maxillary complex structure is very complicated and research limitations, the past models for the anatomical structure are simplified, model accuracy is not high and the geometric similarity is poorer. The RME mechanics analysis on how to use the simulated expand the method analyzes the teeth bow anatomical structure stress, we do not found the appliance and maxillary compound as different modeling and mechanics analysis, so the form established finite element model biomechanical characteristics was poor. Now, how to establish a rapid expansion appliance quickly -- the method of maxillary compound finite element model has not yet been reunified, how to establish precise craniofacial of bone sewing, periodontal model and the meshing standard entity has not yet reached a consensus.Minics 10.0,Geomagic Studio 9,Ansys 10.0 were used to build a high similarity of the geometry with biological characteristics children Hyrax appliance --maxillary complex three-dimensional finite element model method. On rapid expansion maxilla,for using of ANSYS imitate the maxillary palate,the stress condition of gentle or harsh tissue and dental structure,in order to know the location change of every parts stress distribution conditions and index points of three-dimensional directions, so as to explain the process of rapid expansion by the theory of the finite element analysis, for better design and improvement of the appliance and so that we can obtain satisfactory clinical results.Materials and methods:1 A 8.5-year-old, female, healthy child was selected as test subject for oral cavity pyramidal tract spiral CT scanning, slice thickness is 0.3mm, finally 636 two-dimensional CBCT scanning tomography images were obtained. The CBCT scan data was stored into the read-write CD-ROM in DICOM files. The DICOM files were imported in MIMICS10.0. The 3-D maxillary complex models were generated from skinning the original image after thresholding, region growing and smoothing three phases. Next, the Geomagic Studio 9.0 could transform 3D Scan Data into accurate digital models. Then IGES files were imported into the finite element analysis software Ansys10.0 to get the finite element models. 2 The isolated first molar, first premolar, canine, central incisor and the second deciduous molar which were intact shape , surface without caries and right size were raster scaned using 3DSS-MINI-II three-dimensional scanistor.The point-cloud data model trimmed smooth using Geomagic Studio 9.0 with IGES format stored. After the space assembly of maxillary complex—maxillary dentition 3D models with Geomagic Studio 9.0,the model files were stored with IGS format.3 Inport the above models into Ansys10.0, set the grid parameters, devide 3D models into entity by entity (SOLID) unit, take the suture simulation based on normal human anatomy data, finally create maxillary complex three-dimensional finite element model of maxillary dentition. 4 After the model is incised and simplified,then loaded the mechanics, the sphenoid pterygoid process and the amount of zygomatic suture are all-round-shaped symmetry constraint. The first molar and the first premolar were selected the clinical crown center and dental crowns palatal alveolar ridge roof loading level, the static pressure to 3-D finite element analysis, simulated clinical rapid expansion of unilateral bow process 5mm teeth when bow width expand each maxillary complex 3-D change of direction and stress distribution.Results:1 The Hyrax appliance three-dimensional visual models of maxillary complex were established.2 The simplified model is loaded biomechanical mechanics analysis selecting the first molar , the first premolar clinical crown center and dental crowns palatal side nearly alveolar ridge roof,obtained the maxillary complex stress distribution and shift diagram.3 Points of application force in the first molars and premolar clinical crown center were simulated the rapid expansion loaded, the maximum horizontal displacement of the maxillary teeth - the X direction in first molar buccal tip, the displacement is -6.57mm; the largest displacement before of shape to the displacement - that is, Y direction in the first premolar at the tip of the tongue the displacement is 3.11mm; vertical direction - the Z direction, a maximum in the first premolar at the tip of the tongue, the displacement is -2.2mm. Maxillary nearly palate from front to back in the joints and displacement before of form to the maximum level of displacement in the maxillary central incisors appear between the alveolar ridge the displacement is -2.25mm,3.62mm. Vertical direction,the maximum in ANS point, the displacement is -5.40 mm.4 Points of application force in the first molars and premolar clinical crown center were simulated the rapid expansion loaded, the maximum horizontal displacement of the maxillary teeth - the X direction in first molar buccal tip, the displacement is -6.80mm; the largest loss of shape and vertical displacement - that isY, Z direction of the first premolar in section at the tip of the tongue, the displacement direction is 3.41mm,-2.40mm; maxillary nearly palate from front to back in the joints of the maximum horizontal and the maxillary lost sagittal plane displacement in maxillary alveolar ridge between the central incisors at the top of the displacement is-2.57mm,4.15mm;vertical direction, the point of maximum in ANS the displacement is -6.1mm.5 Force points in the first molars and first premolars which simulates the rapid expansion of clinical crown arch are loaded, the first molar periodontal ligament at the first principal stress occurs at the force point of the palatal alveolar, stress is 392Mpa. The third principal stress occurs near the alveolar at the opposite side,stress is -373Mpa;equivalent stress and the lateral displacement force point of maximum value was in the palatal alveolar,the stress value is -377Mpa, X displacement value is -3.16mm.6 Force points in the first molar and first premolar palatal alveolar crest, the first molar periodontal ligament at the first principal stress occurs at the force point of the palatal alveolar crest, stress is 474Mpa;the third principal stress occurs near the alveolar crest at the opposite side, stress is -601Mpa; equivalent stress and the lateral displacement point of maximum value was in force palatal alveolar, stress is 286Mpa, X to displacement value is -3.92mm. Conclusion: A high similarity of the geometry with biological characteristics children Hyrax appliance ---maxillary complex three-dimensional finite element model is builded. The first molar , the first premolar clinical crown center and dental crowns palatal side nearly alveolar ridge roof were selected biomechanical mechanics analysis,obtained clinical rapid expansion of unilateral bow process 5mm teeth when bow width expand each maxillary complex 3-D change of direction and stress distribution.On the maxillary complex finite element analysis, the same as the width of maxillary arch expansion, the stress application closer to the alveolar bone crest expansion of the premises to obtain the greater effect, the smaller the teeth tipping movement, periodontal ligament suffered in the tensile stress, compressive stress is greater, lateral displacement of the teeth. The results suggest that the clinical production of rapid maxillary expansion appliance should be worn when the belt loop system as close as to the alveolar crest department to obtain better treatment results.