Three-dimensional Finite Element Analysis Of Maxillary Ifrst Permanent Molar Distalization By Differential Angle Face-bow

Objective:Useing the original DICOM data of CT and ProENGINEER.Wlidfire4.0software to construct three-dimensional finite element models of maxillary,maxillary first permanent molar and its periodontal ligament, band-buccal tube and different angle face-bows. Analyze the both sides of first molars’original displacement value and the largest equivalent Von Mises stress and the stress distribution of its periodontal ligament by every angle face-bow in symmetric or asymmetric force.The result can provide the theoretical basis for the properly application of different angle face-bow to unilateral molar distaligation.Methods:1. Acquire the original DICOM data by CT scanning. Apply the combination of Mimics10.0,Geomagic Studio10.0,MSC.Marc.Mentat2010and ProENGINEER.Wildfire4.0software to develop6groups of3-D finite element models of bilateral sides of maxillary,maxillary first permanent molar and its periodontal ligament, band-buccal tube and different angle face-bows(According to the Maxillary occlusal plane as a reference, the inner-bow was in parallel with the occlusal plane while the outer-bow was bended0°,15°,30°,45°,-15°,-30°above the occlusal plane, respectively in turn, for model1,2,3,4,5,6).2. Use the MSC.Marc.Mentat2010software to design the physical parameter of various model materials. The posterior of the maxilla and frontal process is used as the standard, while simulate molar distalization by face-bow with the force of bilateral sides of outer bow. Setting the traction force was at4N per side; simulating all of the headgears’ force position kept constantly one side while the other side was opposite, then both sides of first molars’periodontal ligament equivalent Von Mises stress, the stress distribution and each data point to be simulated for original displacement according to coordinates X, Y and Z. Result:1. Well constructed three-dimensional finite element models of maxillary,maxillary first permanent molar and its periodontal ligament, band-buccal tube and various angle face-bow was established, furthermore, these models had a properly geometric compat and mechanical similar.2. In the Symmetric force, both sides of maxillary first permanent molars’ periodontal ligament of six models was consistent on equivalent Von Mises stress and maximum stress value.The stress concentration zone of model1,5and6were similar. The zone concentrated in root furcation area, the distal surface of tooth cervix, buccal surface, and mesial surface of palatine root, what’s more the mesial surface of mesial and distal-buccal root also has. Model2had a uniform stress distribution at mesial surface, buccal surface and root furcation while model3was buccal surface, mesial surface of mesial and distal-buccal root, root furcation, the mesial surface of tooth cervix and distal surface of palatine root.3. In the asymmetric force, the stress distribution of all the models were similar to symmetric except model2.The stress distribution of molar periodontal ligament in model2were concentrated in root furcation, distal surface and buccal surface of tooth cervix and mesial surface of palatine root in the shortening arm side; the elongating one had the them case, then the palate side of1/3of palatine root tip also came to be the stress concentration zone.4. At the symmetric face-bow systems, the molar displacement of both sides were the same. Model1,5and6had an identical distal movement with distal tipping, rotation and buccal inclination; while model2,3and4had the same distal molar displacement with pressed movement and distal tipping, mesial rotation and buccal inclination; model2approached to bodily movement.5. While use the asymmetric face-bow systems, the molar displacement trend was consistent with the symmetric one, but the elongating arm had more molar displacement than the shortening one. Conclutions:1. Apply the original DICOM data of CT combine with Mimics10.0,Geomagic Studio10.0,MSC.Marc.Mentat2010and ProENGINEER.Wildfire4.0software to develop6groups of3-D finite element models of bilateral sides of maxillary,maxillary first permanent molar and its periodontal ligament, band-buccal tube and different angle face-bows. All the six groups had satisfactory results in biological similarity, geometric accuracy and simulation of orthodontic clinical force.2. Asymmteric face-bow system is available for the one-side molar distalization.3. Molar distalization by face-bow could induce molar distal rotation and buccal tipping.0°、-15°、-30°groups could also cause molar extrus and distal tipping while15°、30°、45°groups could cause molar intrus and mesial tipping.