A 3D-Fem Study On Stress Distribution And Displacement Of Craniofacial Complex And Suture With Retractive Forces To Maxilla Of Rhesus Monkey

[Objective] To construct the 3-D finite elemet model of craniofacial complex with the original DICOM data of CT and investigate the biomechanics characters preliminarily with different direction and the magnitude of the retractive forces to maxilla of rhesus monkey.[Materials and Methods]1. The establishment of 3-D finite elemet model of craniofacial complex:a male rhesus monkey in mixed dentition was used, spiral CT scaned, then CT workstation outputed CT images in DICOM format to a personal computer, using ANSYS and Mimics software established the 3-D finite elemet model of craniofacial complex of monkey.2.3-D finite element analysis of craniofacial complex with backward orthopedic forces: based on the establishment of Craniofacial complex 3-D finite element model of the monkeys in experiment 1. Then the ANSYS software was used to analyse stress distribution and displacement of craniofacial complex on nasofrontal suture, zygomaticofrontal suture, zygomatic suture, zygomatic temporal suture.[Results]1. The establishment of craniofacial complex three-dimensional finite element model:model, which was made up of 278995 units and 78677 nodes, included maxilla and bones all around, parts of the skull, and all of the cavity, sinus, pore structures. Model and modeling were of the same size with a good geometric similarity. So it could be splitted randomly or extracted a certain part for a separate study. And it had scalability which made it possible to attach brackets, arch wires, implants to start related studies.2. orthopedic effects on maxilla with retraction force:â‘ Loading force backward on alveolar bone between the bilateral lateral incisor and canine meanwhile the force paralleled withY axis (functional occlusal plane). with the increase of the force value, each landmarks (A, N, ANS, PNS, Zm, Zm') showed larger displacement, values of displacement and force the size suggested a linear relationship. In the X-axis (horizontal) direction, all the displacements are small, showing that level backward traction will not have significant impact on the width of the upper jaw. In the Y-axis direction, all the displacements showed great changes, with the increase of the force value displacement increased significantly, showing that there was an obvious backward effect on maxilla. In the Z axis (vertical) direction, A-point and ANS point moved downward but PNS Upward, showing that maxilla rotated clockwisely.â‘¡The distribution of stress produced three pathways, consistenting with the three pairs of maxilla pillars basically. The stress value and the magnitude of force were of a linear relationship. With the traction value increased, stress value in all sutures increased too. Nasofrontal suture and zygomaticofrontal suture showed tensile stress, but zygomatic suture and zygomatic temporal suture showed compressive stress, showing that maxilla rotated clockwisely too. The stress distribution of Zygomatic suture was complex because of the complexity of the anatomy.3. High and low traction:Changing the angle of traction along the Z axis (vertical), the displacements'changes of the points (A, N, ANS, PNS, Zm, Zm') in the Z axis were most effective, in the Y-axis were more effective, in the X-axis were almost no effect, when the traction angle was negative, points moved to the negative direction of the Z axis; when the angle is positive, points moved to the positive direction of the Z axis, indicating that the direction of traction is important.when the traction direction went down relatively under functional occlusal plane, clockwise rotation will occured on maxilla, on the contrary, the counterclockwise rotation would happened on maxilla.4. Maxillary width changes with tracting inward and outward:tracting inward or outward had significant impact on the width of the maxilla. When the posterior-traction leveled with the Y-axis, it gave molar compression slightly, and with increasing outward angle, the arch width was increased. The traction affected the width of the central facial part less than arch, suggesting that traction on the patient would have some influence in central facial form. The traction almost had no influence on the width of the upper facial part, suggesting that the orbital and frontal width would not be affected with orthopedic traction.[Conclusion]1. Explored a way to built the 3-D finite element model from helical CT tomography data which is based on the conventional two-dimensional spiral CT scan of the original DICOM digital image data. Using MIMICS, ANSYS software, we established the three-dimensional finite element model which adjusted to biological morphology and biomechanical characteristics, what's more it was easy to apply and calculate.2. The stress of suture and the magnitude of the force is of a linear relationship, with the magnitude of force increasing the stress increased. To achieve better orthopedic effect, it was better to increase the value of tractive force. However, the force select should also consider the biological requirements of suture. That is to say the chosen force was the stronger the better in the physiological range.3. The maxillary rotation changed along with the vertical angle, high traction produced counterclockwise rotation, low-traction caused rclockwise rotation; Changing the inward and outward direction had an impact on the maxillary arch width, the outward traction caused the expansion of the maxillary arch and central facial width, the effect is greater with angle increasing. The direction of force should be selected according to the type of malocclusion in the clinical treatment.