Virtual Simulation And Biomechanics Study Of Mandibular Kinematics

Mandibular kinematics is a sophisticated movement in three-dimensional space executed under the control of nervous system by mandible,temporomandibular joints, occlusion,masticatory muscle and mandibular ligaments.And it can perform many physical activities inseparable in daily life,such as chewing,swallowing,speaking and facial expressions.Therefore,mandibular movement is one of the critical factors in the diagnosis,treatment and prognostic evaluation of some related diseases.The restoration of normal mandibular movement is the main purpose of the maxillary and mandibular operations,the production of dental prosthetic,the implant and the orthodontics.Meanwhile,it is significant for the protection of oral maxillofacial region in sports and traffic accidents.Because of its unique anatomic structure and the high coordination of structure and function,the method recording mandibular movement can not provide satisfactory index in clinical diagnosis and treatment.With the development of computer technology,virtual reality technology(VR) is widely used in biomechanical study of the human body,so the apparence of the digital virtual technology of mandibular movement will bring special significances for the study of the mandibular movement.According to the principle of virtual reality,the objective of this study is to virtually simulate mandibular kinematics utilizing maxillary and mandibular 3D digital model and the information parameters of mandibular movement.The relative structures and biomechanics characteristic of masticatory muscles,the temporomandibular joint disc,and the ligament of mandibular articulation,the dependent organes of mandibular movement,are showed through dissected cadaveric head.The 3D digital analogue of masticatory muscle is established. We can achieve the simulation of mandibular movement with VR by constructing 3-digital version of the maxillofacial bones related with mandibular movement,founding its kinematical model with cadaveric head,collecting the information of jaw motion using three-diamensional laser.Our study can not only simulate the track of the mandibular movement but also realize that when we analyze the relative position relation and contact points of the upper and lower dentition in the movement,as well as we can observe the movement of temporomandibular joint, which will contribute to learn more about the regular pattern of mandibular movement and set up the quantified examination method.At the same time,the mandibular force is tested via biomechanics in vitro and the interal mandibular stress is analyzed with finite element method.They can bring to light the change regularity of interal mandibular stress by the interaction of biomechanical method and finite element analysis which provide the foundation for further human-computer interaction of mandibular motion in VR.This aiticle disscusses detailly the key points in the establishment of the virtual simulation of mandibular movement about cadaveric head:the relevant anatomic feature and modeling means of mandibular motion,the acquisition of information about jaw movement,the virtual simulation of its movement,and the finite element analysis of the stress of mandible The concrete procedures include the following three aspects:1.The relevant digital anatomy of mandibular kinematicsWe dissect the relevant organs of mandibular kinematics in cadaveric head,such as jaw muscle,the temporomandibular joint disc,and the ligament of mandibular articulation.Firstly,we prosect masster muscle,temporal muscle,medial pterygoid muscle,and lateral pterygoid muscle in order to identify the beginning and ending points,course,distribution and delamination of these morphological characteristics. The shape and the organization form of temporomandibular joints(TMJ) disc are observated through the specimen and histological sections.The anatomical features and the mechanical and biological characteristics of masticatory muscles, temporomandibular joint disc,and temporomandibular joint ligament are identified. Then,using CT images,3D laser scanning point cloud and virtual digital human datasets respectively,we reconstruct 3D digital model of masster muscle,temporal muscle,medial pterygoid muscle,and lateral pterygoid muscle based on anatomical features,which may display three-dimensional space targeting,measure their distance, and meet the requirements of biomechanical analysis.We attempt to establish the facial soft tissue model with a variety of methods in order to accurately reproduce the subtle anatomical features,which play key roles not only in its morphology and functions of research,teaching anatomy,preoperative evaluation of the soft tissue repair and reconstruction operations,but also providing the basis for mandibular kinematics model on account of physical and physiological characteristics of human.2.The virtual simulation of mandibular kinematicsOn the basis of CT scan data,the 3D digital model of the independent maxilla and mandible are reconstructed with Minics software,and the standard coordinates system is built by virtue of frankform plane with the view to evaluate mandibular movement.Using three-dimensional laser scanning system we collect the point clouds of mandibular movement model,Geomagic software used to restore the status of the mandibular movement and accessed the six degrees of freedom of its motion. Through repeated measurements of the variance of six degrees of freedom methods for statistical analysis,the results are as follows:the opening and closing movement occurred mainly in the sagittal plane,but there are other directions with the movement.By coordinates transformation we can achieve 6 degrees of freedom of mandibular central incisor point,the right condylar process,and the left condylar process,and gain any points distance changes in mandible of its motion through function calculation or Geomagic software direct measurement.Under 3Dmax software environment,we come true the virtual simulation of mandibular kinematics with the independent upper and lower jaws 3D digital model and the 6 DOF of mandibular central incisor point.In this experimental study,the VR of mandibular motion can display the three-dimensional space position between maxilla and mandible,occlusion,and temporomandibular joint surface,at the same time, visualizate the course of mandibular movement,quantify the regularity of the three-dimensional space changes for the motion,and establish the quantitative methods of mandibular kinematics.3.The finite element analysis of mandible and biomechanies testThe mental force is tested on the MTS materials experiments with the establishment of the mandibular impact model.Using three-dimensional laser scanner system we create a highly realistic mandibular model,and then converted to finite element model in order to perform finite element analysis and calculation.To set up the boundary restraint of finite element method according to biomechanics experimental conditions,it analyzes the internal mandibular stress after the mental is impacted.The results reveal the change of its stress,the mechanotransduction regulation and the stress curve in mandible.Finite element method can not only display the internal mandibular stress which biomechanical analysis experiment can not be involved,but also validate samples trial and maximize the finite element analysis results corresponds to the impact test results so as to implement the true sense of the simulation.Conclusions(1) The establishment of the 3D digital model of the masticatory muscle based on anatomical features:using CT images,3D laser scanning point cloud and virtual digital human datasets respectively,we reconstruct 3D digital model of masster muscle,temporal muscle,medial pterygoid muscle,and lateral pterygoid muscle based on anatomical features,which may display three-dimensional space targeting, measure their distance,and meet the requirements of biomechanical analysis,as well as form the modeling means based on anatomic feature.(2) Achievement virtual simulaton of mandibular kinematics:we come true the virtual simulation of mandibular kinematics with the independent upper and lower jaws 3D digital model and the point clouds of mandibular movement model scanned by three-dimensional laser system.In this experimental study,the VR of mandibular motion can display the three-dimensional space position between maxilla and mandible,occlusion,and temporomandibular joint surface,at the same time, visualizate the course of mandibular movement,quantify the regularity of the three-dimensional space changes for the motion,and establish the quantitative methods of mandibular kinematics.(3) Founding the standard coordinates system of mandibular kinematics:we establish the coordinates system based on Frankfort plane in order to quantify the mandibular movement.(4) With the interaction between biomechanical impact test of mental and finite element method,the results reveal the change of interal stress,the mechano-transduction regulation and the stress curve in mandible.Finite element method can not only display the internal mandibular stress which biomechanical analysis exiperments can not be involved,but also validate samples trial and maximize the finite element analysis results corresponds to the impact test results so as to implement the true sense of the simulation Simulation.The method of visualization and quantization of mandibular kinematics and its virtual reality will be established according to the method of regenerated model,the data of mandibular kinematics,biomechanics measurement,and finite element analysis.