Three-dimensional Finite Element Analysis Of Modified Miniplate Implants To Assist Maxillary Protraction Treatment

[Objective]In this study,we established three-dimensional finite element models of two types of modified miniplate implants(L/Y)to assist maxillary complex for maxillary protraction treatment,analyzed the distribution trend of the maxillary displacement and the distribution characteristics of the stress of the main circummaxillary sutures with different titanium plates under different angles,to provide reference for clinical application.[Methods]Select an age of 12 years old person,who during the early period of permanent teeth,accompanying the skeletal class III malocclusion with maxillary deficiency,establish the three-dimensional finite element model of the maxillary complex using CBCT scanning and combined with finite element method,including the physical model of the sutura temporozygomatica,sutura zygomaticomaxillaris,sutura frontomaxillaris,sutura pterygopalatine and midpalatal suture.Based on this,six kinds of modified miniplate implant models were established.500g/side was applied to 6 kinds of modified miniplate implants respectively,forward and downward.In both cases,the maxillary protraction was made at angles of 0°,10°,20°,30°,40°,50°degrees from the occlusion plane,analyze the trend of maxillary displacement and change under different working conditions as well as the stress and displacement trend of the main suture around the maxillary.[Results]Two types of three-dimensional finite element model of a total of 6 kinds of modified miniplate-anchoraged maxillary protraction treatment was established,which contains about 350,000 nodes and230,000 units was built,as well as the physical model of the sutura temporozygomatica,sutura zygomaticomaxillaris,sutura frontomaxillaris,sutura pterygopalatine and midpalatal suture.The application of different modified miniplate implants showed that the displacement of the maxilla,the stress of the suture and the trend of change with the change of the traction angle were basically consistent.In the application of modified miniplate implants to assist the maxillary protraction treatment,the maxillary dentition has a tendency to narrow,and this trend decreases with the traction angle increasing forward and downward.When pulling the maxilla forward and downward,and the angle with the occlusal plane at 0-20 °,the maxilla rotates counterclockwise.At 0 °,the stress of sutura temporozygomatica,sutura zygomaticomaxillaris,sutura frontomaxillaris,sutura pterygopalatine can reach the maximum.When the angle at30-50 °,the maxilla rotates clockwise,as the traction angle down gradually,the clockwise rotation of the maxilla increases and the maximal forward part moves upward.However,the maximal forward displacement of the maxilla decreases with the change of angle,The stress of sutura pterygopalatine decreases gradually,while the stress sutura temporozygomatica,sutura zygomaticomaxillaris and sutura frontomaxillaris increased but the displacement tends to be downward.[Conclusions]1.The establishment of three-dimensional finite element models of two kinds of modified miniplate implants in frontal traction treatment of upper maxilla provides a reliable platform and foundation for the analysis of the displacement tendency of the maxilla and the stress and displacement of the main circummaxillary sutures.2.When the position and direction of the traction force were determined,the morphology of the modified micro-titan plate implants do not affect the displacement of the maxilla in the maxillary protraction treatment and the stress and displacement of the circummaxillary sutures.3.In the application of modified miniplate implants to assist the maxillary protraction treatment,when the traction direction forward and downward at the angle of 0-20 °,there is a counterclockwise rotation in the maxilla,it benefit to crossbite patients;when at 30-50°,there is a clockwise rotation in the maxilla,it benefit to crossbite patients who accompany open bite.However,as the traction angle downs gradually,the maximal forward decreases,it is suggested that we need to increase traction or prolong the treatment time in this direction.We should also pay attention to the width of the patient's dental arch,especially when the traction direction is forward and downward and the Angle is small,If necessary,it should be combined with maxillary expansion treatment.