Motion reconstruction and finite element analysis of the temporomandibular joint during swallowing in healthy adults.

There is a close physiological connection between swallowing and the temporomandibular joint (TMJ). However, a shortage of quantitative research on the biomechanical behavior of the TMJ during swallowing exists. The purpose of this study was to reconstruct the movement of the temporomandibular joint (TMJ) based on in vivo experiment and analyze the biomechanical responses during swallowing in healthy adults to investigate the role of the TMJ in swallowing. Motion capture of swallowing, computed tomography (CT), and magnet resonance images (MRI) were performed on six healthy subjects. The movements of the TMJ during swallowing were reconstructed from the motion capture data. The three-dimensional finite element model was constructed. The dynamic finite element analysis of the swallowing process was performed based on the motion data. The range of condylar displacement was within 1 mm in all subjects. The left and right condyle movements were asymmetrical in two-thirds of the subjects. The peak stresses of the discs were relatively low, with a maximum of 0.11 MPa. During swallowing, the condylar displacement showed two trends: slow retraction and slow extension. The tendency to extend could lead to a gradual increase in stress on the disc.

Altered dynamic joint space in the lateral condyle compartment following medial unicompartmental knee arthroplasty.

PURPOSE: The progression of osteoarthritis in lateral compartment has been identified as a primary complication in medial unicompartmental knee arthroplasty (UKA) revisions, irrespective of whether employing fixed bearing (FB) or mobile bearing (MB) designs. Compared to the previous contact point analyses, the tibiofemoral contacts during knee movements are comprehended by a more comprehensive understanding of joint spaces. This study aims to dynamically map the joint spaces in the lateral compartment during the single-leg lunge following FB and MB UKA procedures, and compare them with the respective contralateral native knees. It is hypothesized that the significant change in joint space for post-UKA compared to their native knees. METHODS: Twelve patients with unilateral medial FB UKA and eleven patients with unilateral medial MB UKA were included and underwent computed tomography scans. The exclusion criteria included anterior cruciate ligament deficiency, postoperative knee pain, any postoperative complications, and musculoskeletal illnesses. A dual fluoroscopic imaging system was utilized to capture the single-leg lunge, and 2D-to-3D registration facilitated the visualization of knee motion. According to the knee motions, joint spaces on tibial and femoral surfaces in the lateral compartments of native, FB, and MB UKA knees were calculated and mapped. RESULTS: In comparison to the native knees, FB UKA knees exhibited significant increases in medial, lateral, central, and posterior joint spaces in the lateral compartment (p < 0.05), while MB UKA knees showed significant increases only in central and posterior joint spaces (p < 0.05). Moreover, FB UKA demonstrated greater increases in medial, central, and posterior joint spaces compared to MB UKA. Tibial varus and valgus during lunges, as well as the Oxford Knee Score (OKS) and Hip-Knee-Ankle angle (HKA), correlated with joint spaces. CONCLUSIONS: Dynamic joint space analysis provided a more comprehensive insight into contact dynamics. FB UKA led to an enlargement of joint spaces, whereas MB UKA resulted in joint spaces closer to native knees. These findings contribute to understanding potential postoperative complication in UKAs.

Temporomandibular joint stress analysis of patients with different mandibular deformities during unilateral molar occlusion.

Mandibular prognathism, retrusion and deviation are common mandibular deformities. They can lead to functional and aesthetic problems due to their important role in the oral system. Different from other occlusions, unilateral molar occlusion often occurs during mastication, which has a deep impact on the functions of temporomandibular joints (TMJs). Therefore, the study of unilateral molar occlusion is of great importance and significance to the daily life of patients with mandibular deformities. A total of 35 individuals were involved in this study, including 11 asymptomatic subjects, 10 patients with mandibular prognathism, 5 patients with mandibular retrusion and 9 patients with mandibular deviation. Finite element (FE) models corresponding to the unilateral molar occlusion were constructed. During unilateral molar occlusion, mandibular deformity increases the pressure on the condyle and articular disc. Compared with mandibular protrusion or retraction, facial asymmetry will significantly increase the stress of TMJ. Chewing on the non-deviated side also will lead to higher stress in the TMJ of patients with mandibular deviation. Therefore, patients with mandibular deviation have the highest risk of temporomandibular disorder (TMD), and it is recommended that patients with mandibular deviation chew bilaterally or with the deviated side.

In vivo biomechanical dynamic simulation of a healthy knee during the single-leg lunge and its experiment validation.

Biomechanical modeling of the knee during motion is a pivotal component in disease treatment, implant designs, and rehabilitation strategies. Historically, dynamic simulations of the knee have been scant. This study uniquely integrates a dual fluoroscopic imaging system (DFIS) to investigate the in vivo dynamic behavior of the meniscus during functional activities using a finite element (FE) model. The model was subsequently validated through experiments. Motion capture of a single-leg lunge was executed by DFIS. The motion model was reconstructed using 2D-to-3D registration in conjunction with computed tomography (CT) scans. Both CT and magnetic resonance imaging (MRI) data facilitated the development of the knee FE model. In vivo knee displacements and rotations were utilized as driving conditions for the FE model. Moreover, a 3D-printed model, accompanied with digital imaging correlation (DIC), was used to evaluate the accuracy of the FE model. To a better inner view of knees during the DIC analysis, tibia and femur were crafted by transparent resin. The availability of the FE model was guaranteed by the similar strain distribution of the DIC and FE simulation. Subsequent modeling revealed that the compressive stress distribution between the medial and lateral menisci was balanced in the standing posture. As the flexion angle increased, the medial meniscus bore the primary compressive load, with peak stresses occurring between 60 and 80° of flexion. The simulation of a healthy knee provides a critical theoretical foundation for addressing knee pathologies and advancing prosthetic designs.

Transparent and Soft Crack-Resistant Bouligand Elastomers Inspired by Fish Scales.

Nature with its abundant source offers numerous inspirations for structural and engineering designs. The oriented membranes stacked with bouligand structures in the fish scales show an outstanding combination of high strength and crack resistance. Although the applications of hard biomimetic composites are reported, the structures are rarely utilized in soft materials. Inspired by the scales of various fishes, electrospun membranes are used and stacked to fabricate bouligand elastomers, including orthogonal-plywood, single-bouligand, and double-bouligand structures. The effects of different structures on the properties of elastomers are systematically investigated and possible mechanism is explained using finite element analysis (FEA). The stiffness and fatigue characteristics of these biomimetic elastomers with the above structures are improved compared with the original membranes, especially the elastomers with a single-bouligand structure, which can undergo 5 000 cycles at a maximum strain of 35% without complete failure. The crack only propagates to half of the width of the elastomer with remaining strength of 50% of its original strength. Moreover, the mechanical performance can be adjusted by regulating the proportion of the components. The excellent crack-resistant properties and transparency promote its various potential applications.

Effect of pre-stress on dynamic finite element analysis of the temporomandibular joint.

The pre-stress of the temporomandibular joint (TMJ) at the intercuspal position (ICP) was often neglected, which would cause errors in the finite element analysis. The purpose of this study was to investigate the effect of pre-stress on dynamic finite element analysis of the TMJs. One healthy female adult was recruited for medical imaging and motion data acquisition of the reference position (RP) to the ICP and the clicking teeth. The three-dimensional maxillofacial model including the maxilla, mandible, articular cartilages, discs, and discal attachments was reconstructed. Motion from the RP to the ICP was simulated to obtain pre-stress at the ICP. Two groups of the clicking teeth were simulated: (1) the group without pre-stress (GWoP); (2) the group with pre-stress (GwP). Significant differences were found between the two groups at the initial moment of movement, during the open-mouth phase, and during the collision phase between the upper and lower teeth. The maximum difference in the discal contact stress between both groups was even more than double. The relaxation of the TMJ at the beginning of the mouth opening was simulated in the GwP. In addition, an increase in the TMJ stress during teeth tapping was simulated in the GwP. These were not reflected in the GWoP. If pre-stress at the ICP was not considered, part of the true results would be lost. It is necessary to consider pre-stress in the dynamic finite element analysis of the TMJ.

The effects of the size and strength of food on jaw motion and temporomandibular joints.

Mastication displays much importance in people's lives. The masticatory mandibular motion associated with dental kinematics also impacts temporomandibular joint (TMJ) kinematics and even TMJ health status. How food properties impact kinematical parameters of TMJs is a meaningful question for the conservative treatment of temporomandibular disorders (TMD) and evidence for the diet recommendation of TMD patients. The aim of this study was to find the primary mechanical properties influencing the masticatory motion. The potato boluses with different boiling times and sizes were chosen. The optical motion tracking system was adopted to record the masticatory trials of chewing boluses with various mechanical properties. The mechanical experiments revealed that increasing boiling time could reduce compressive strength. Moreover, multiple regression models were built to find the primary property of food influencing the TMJ kinematics, including condylar displacement, velocity, acceleration, and crushing time. The results showed that the bolus size had a significant primary influence on condylar displacements. The chewing times had a significantly minor influence on condylar displacements, while bolus strength had only a small impact on condylar displacements. Furthermore, condylar displacements on the non-working side were more affected by bolus size and chewing times than on the working sides. The crushing time of the bolus was significantly influenced by the compressive strength. Meals with small sizes and soft properties were therefore advised to lessen condylar displacements and relax the crushing process, and further reduce the loadings in the TMJ.

Biomechanical comparison of the effect of bilateral sagittal split ramus osteotomy with or without Le Fort I osteotomy on the temporomandibular joints of the patients with maxillofacial deformities under centric occlusion.

Mandibular deformities negatively affect the daily activities of the patients and may cause temporomandibular disorders (TMD). Bilateral sagittal split ramus osteotomy (BSSRO) and Le Fort I osteotomy are effective treatments to correct the mandibular deformities. The aim of this study was to investigate and compare the effects of the BSSRO with or without Le Fort I on the stress distributions of the temporomandibular joints (TMJs) of the patients with mandibular deformities under centric occlusion based on finite element (FE) method. Preoperative and postoperative cone-beam computed tomography (CBCT) images of twenty-four patients diagnosed with mandibular prognathism, including ten patients with BSSRO and another 14 patients with bimaxillary osteotomy (BSSRO with Le Fort I), were used to construct maxillofacial models. Ten asymptomatic individuals were also performed CBCT scanning and defined as the control group. In addition, the muscle forces and boundary conditions corresponding to centric occlusions were applied on each model. For the preoperative groups with both the BSSRO and bimaxillary osteotomies, the average peak contact stresses of the TMJs were both greater than those of the control group. After the surgeries, the contact stresses of the discs and temporal bones of both groups considerably decreased. However, the contact stresses on the condyles slightly increased after BSSRO but decreased after bimaxillary osteotomy. The TMJs of the patients with maxillofacial deformities suffered abnormal tensile and compressive stresses compared with the asymptomatic subjects under centric occlusion. Both of the BSSRO and bimaxillary osteotomy could improve the risk stress distributions of the TMJs.

Descriptions of the dynamic joint space of the temporomandibular joint.

BACKGROUND: Clinical diagnosis and treatment depended heavily on the motion analysis of the human joints. Although the dynamic joint space (DJS) of other organs was widely used in academic investigations, they were not universally used in the temporomandibular joint (TMJ) field, which was also important for the motion evaluation of the TMJ. The objectives of this study are to introduce the DJS of the TMJ and characterize the DJS regulars of mandibular movements. METHODS: Ten asymptomatic subjects were selected to instruct this application. The mouth opening and closing, mandibular protrusion, and left and right protrusions, were tracked by the optical motion tracking system. According to trajectories of markers and reconstructed models from computed tomography, the motions of the mandibles could be obtained. The DJSes, which were described as the minimum Euclidian distances, were subsequently calculated based on the geometrical surfaces between the condyle and fossa during the motions. Then, the DJS map could be drawn based on the calculated values. RESULTS: The DJS map manifested a decreasing trend when the condyle crossed the glenoid fossa, while it generally increased after the condyle crossed the fossa during the mouth opening. The results showed that the average maximum and minimum anterior joint spaces were 5.39 mm and 2.07 mm during mouth opening respectively with a great discrepancy existing among the subjects. The average maximum and minimum anterior joint spaces were 4.74 mm and 2.19 mm during mandibular protrusion. As for left and right protrusions, the DJS of the contralateral side was greater than that of the ipsilateral side. CONCLUSION: In comparison to morphological analyses or only mandibular motions, the DJS provides more dynamic and interactive information about the TMJ. The research and methodology may help us comprehend TMJ motions and temporomandibular disorders.

The effect of mandibular movement on temporomandibular joint morphology while eating French fries.

BACKGROUND: The preferred masticatory side was reported to be almost always the same as the affected side of the temporomandibular disorder. Unbalanced alterations of temporomandibular joint morphology were found to be associated with unilaterally masticatory habits. The aim of this study was to investigate the effect of the mandibular movement on the remodeling of temporomandibular joint during eating French fries using a 3D motion capture system. METHODS: Twelve volunteers with non-maxillofacial deformity and a healthy temporomandibular joint were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to eat French fries by unilaterally mastication, which was recorded by a 3D motion capture system. The trajectories of the incisors and the condyles and the condylar acceleration during unilateral mastication were analyzed. RESULTS: During incisal biting, there was no significant difference in the condylar trajectories between the left and right sides (P > 0.05). During unilateral mastication, the average displacement and acceleration of the masticatory condyles were significantly lower than those of the non-masticatory condyles (P < 0.05). The trajectory angles of the masticatory condyles were significantly steeper than those of the non-masticatory condyle (P < 0.05). During swallowing, there was no obvious movement of the mandible. CONCLUSIONS: Between both temporomandibular joints, unilateral mastication resulted in significant differences in the regions of the condylar movement within the articular fossa, and then caused different compressive regions of the temporomandibular joints. Thus, unilateral mastication might result in a significantly different pattern of temporomandibular joint remodeling between the two sides.

In vivo biomechanical effects of maximal mouth opening on the temporomandibular joints and their relationship to morphology and kinematics.

The temporomandibular joints (TMJs) are the only joints in the human skull and regulate all mandibular motions. The functions of TMJs are considerably influenced by their biomechanical surroundings. However, owing to the unique characteristics of TMJs, comprehending their kinematic and biomechanical mechanisms remains challenging. As a result, understanding how biomechanics relate to TMJ structures and motions is critical in subsequent therapies. The goal of this study is to investigate any links between morphological or kinematic factors and discal stresses during mouth opening. Our study included eight asymptomatic participants who did not show any signs or symptoms of temporomandibular disorders. The morphological parameters, kinematic properties, and stresses were determined using computed tomography (CT), magnetic resonance imaging (MRI), and subject-specific movements. Following the investigation, we discovered that the opening of the mouth was not the primary cause of TMJ stress. The stress on the discs is directly linked to condylar displacements during mouth opening. Furthermore, morphological characteristics related to the relative position of the condyles in the glenoid fossa at the intercuspal position have a limited effect on condylar displacements and stresses. In conclusion, the morphological parameters, which are commonly employed in clinics, show only static conditions in the TMJs. The kinematic parameters provide dynamic information regarding the TMJs, which can be used in the examination, diagnosis, and treatment of TMJ diseases to reduce stress.

High-Performance Crack-Resistant Elastomer with Tunable "J-Shaped" Stress-Strain Behavior Inspired by the Brown Pelican.

The gular sac tissue of brown pelican featured by the curvy pattern of fibers has an excellent combination of strain-stiffening behavior and fracture resistance. We develop an embroidery-reinforcement and solvent-welding strategy to fabricate a biomimetic elastomer with similar structure to that of the gular sac tissue. The embroidery reinforcement enables a well-designed biomimetic pattern of aramid fibers, and the solvent welding induces strong interfacial interaction between the aramid fibers and polyurethane matrix. This strategy endows the composite with excellent strain-stiffening behavior, fracture resistance, mechanical strength, and toughness, which are even better than the living prototype. Finite elements analysis reveals that the curvy pattern and strong interfacial interaction are crucial for both the J-shape behavior and the mechanical properties. The facile and robust strategy can be extended to other fibers reinforced polymers and should be promising for development of strong and tough soft materials with "J-shape" behavior.

Three-dimensional morphological and biomechanical analysis of temporomandibular joint in mandibular and bi-maxillary osteotomies.

Orthognathic surgery is a typical approach for treating maxillofacial deformities. However, orthognathic surgery results in positional changes in the condyles. In a previous review, the effects of orthognathic surgery on temporomandibular joints (TMJs) are not provided. Hence, in this study, we investigate the morphological changes in TMJs after mandibular and bi-maxillary osteotomies. The relationship between the morphological parameters of TMJs and symptoms of temporomandibular disorders (TMDs) is discussed. Finite element contact stress analysis is performed, and the results show that the two abovementioned surgeries can improve maxillofacial deformities, although the positions of the condyles are changed. Moreover, preoperative stress asymmetry of the left and right TMJs is observed, which remain after the surgeries. TMD patient-specific analysis shows that three joint spaces (medial joint space, lateral joint space, superior joint space) are significantly correlated with TMD symptoms.

Biomechanical effects of high acceleration on the temporomandibular joint.

The symptoms of temporomandibular disorders (TMD) are easily developed in pilots after long flights, such as joint pain, anterior displacement disc and so on. Related studies have suggested that abnormal high acceleration would cause temporomandibular joint (TMJ) lesions. Therefore, the purpose of this study is to analyze the biomechanical effects of high acceleration on the TMJs. The 3D models of the maxilla, mandible, articular disc were generated by Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) of a healthy volunteer without any TMD symptoms. Then, the loads were added according to the various operating conditions of the aircraft. The maximum tensile stress, occurred in the anterior band of the discs, exceeded the failure stress. Compared with the low acceleration, the contact stresses between the discs and the articular cartilages were much greater under the high acceleration. High acceleration had a negative impact on the stress distributions of the articular discs and cartilages and easily led to TMJ damage. Lateral acceleration will cause asymmetric stress distribution of the TMJs.

3D Printing Experimental Validation of the Finite Element Analysis of the Maxillofacial Model.

Contacts used in finite element (FE) models were considered as the best simulation for interactions in the temporomandibular joint (TMJ). However, the precision of simulations should be validated through experiments. Three-dimensional (3D) printing models with the high geometric and loading similarities of the individuals were used in the validation. This study aimed to validate the FE models of the TMJ using 3D printing models. Five asymptomatic subjects were recruited in this study. 3D models of mandible, disc, and maxilla were reconstructed according to cone-beam CT (CBCT) image data. PLA was chosen for 3D printing models from bottom to top. Five pressure forces corresponding to the central occlusion were applied to the 3D printing models. Ten strain rosettes were distributed on the mandible to record the horizontal and vertical strains. Contact was used in the FE models with the same geometries, material properties, loadings, and boundary conditions as 3D printing models to simulate the interaction of the disc-condyle, disc-temporal bone, and upper-lower dentition. The differences of the simulated and experimental results for each sample were less than 5% (maximum 4.92%) under all five loadings. In conclusion, it was accurate to use contact to simulate the interactions in TMJs and upper-lower dentition.

Biomechanical analysis of temporomandibular joints during mandibular protrusion and retraction motions: A 3d finite element simulation.

BACKGROUND AND OBJECTIVE: Temporomandibular disorders (TMDs) represent a wide range of musculoskeletal disorders associated with the maxillofacial system, which negatively affect the daily activities of patients. TMD symptoms are caused by the temporomandibular joint (TMJ) overloading. TMJ motions are frequent and can trigger overloading and imbalanced loads on the TMJs, which are assumed to be dangerous. The condyles move forward a lot during mandibular protrusion, which is possibly harmful to the biomechanical environment of the TMJs. The aim of this study was to investigate the biomechanical behavior of TMJs during mandibular protrusion and retraction. METHODS: Six three-dimensional maxillofacial system models from asymptomatic subjects were established through computed tomography (CT) and magnetic resonance imaging (MRI). The mandibular protrusion and retraction were recorded using an optical tracking system. Finite element analysis was used to simulate the biomechanical behaviors of the TMJs during the movements. RESULTS: The simulation results were validated to be effective by comparison with the MRIs. The results indicated that the stresses during the protrusion and retraction were approximately equal at the same condylar displacement. Meanwhile the discal stresses, relatively correlated with the condylar displacement, increased as the condylar displacement increased during the protrusion and decreased as the condylar displacement decreased in the retraction. In addition, the average peak maximum and minimum principal stresses of the discs were 0.186 and -0.192 MPa, respectively. CONCLUSIONS: The models were reasonable for the investigation of the TMJs motion. Based on the results, three quadratic polynomials were proposed to describe the relationship between the stresses and the condylar displacements. In clinical diagnosis, the functions are helpful in the prediction of the discal stresses by measuring the condylar displacement.

Temporomandibular condylar articulation and finite helical axis determination using a motion tracking system.

Kinematics play an important role in assessing the recovery of the patients' temporomandibular joint (TMJ) and occlusal functions. The finite helical axis (FHA), which simplifies three parameters in Euler-angle descriptions, provides a comprehensive insight into TMJ kinematics. Additionally, the FHA is one of the potential indicators used in the diagnosis and treatment of TMDs and the design and use of the TMJ replacement. This study aimed to illustrate the changes in the FHA of the TMJs during basic mandibular motions. Visible markers were rigidly affixed to the mandibular dentition and a helmet. Four active motions were registered: mouth opening, mandibular protrusion, and left and right lateral protrusions. According to the models reconstructed from the computed tomography of the same subject and the relative distance of the markers, subject-specific condylar tracking was achieved, and the FHAs for the four motions were determined. In addition to the irregular distribution in the initial opening, the FHA of the opening formed an "L-shaped" curve. Mandibular protrusion is a translational motion with little rotation. Additionally, the FHA crossed the ipsilateral TMJ during lateral protrusions, from initially vertical directions generally to horizontal directions at the front view. The proposed method provides a feasible way for measuring the FHA.

[Three-dimensional morphological changes in the temporomandibular joints of patients with anterior disc displacement with reduction].

OBJECTIVES: To investigate the differences in the temporomandibular joints (TMJs) between patients with anterior disc displacement with reduction (ADDwR) and asymptomatic subjects by using 3D morphometric measurements. METHODS: A total of 15 patients with ADDwR and 10 asymptomatic subjects were enrolled. Then, 3D models of the maxilla and mandible were reconstructed using MIMICS 20.0. Nine morphologic parameters of TMJs on both sides were measured on the 3D solid model. The differences in the parameters were analyzed between the patients and the asymptomatic subjects and between the left and right sides of each group. RESULTS: The horizontal and coronal condylar angles on the ipsilateral side of the patients were significantly greater than those of the asymptomatic subjects (P<0.01). Meanwhile, the sagittal ramus angle (SRA), medial joint space, lateral joint space, superior joint space, anterior joint space, and posterior joint space in the patients were significantly lower than those in the asymptomatic subjects (P<0.01). CONCLUSIONS: ADDwR will increase the condylar angles to be significantly greater than the normal level and decrease SRA and articular spaces to be significantly smaller than the normal level. The condyles will be displaced upward, closer to the fossa.

Mathematical analysis of the condylar trajectories in asymptomatic subjects during mandibular motions.

The understandings of motional regular and dynamic information during the mandibular motions are essential to investigate the dysfunctions of temporomandibular joints (TMJ). This study aims to develop a method to record the mandibular movements and analyze the condylar trajectory, velocity, and acceleration in asymptomatic individuals during mandibular motions. Thirteen asymptomatic subjects were strictly selected without symptoms of temporomandibular disorders (TMDs). An optical tracking system was chosen for recording mandibular motions. Curve fitting was used for fitting the trajectories of condyles, notches and lower incisor, and the articular eminence outlines. The sagittal plane (YoZ) provided a better view for condylar trajectories during mouth opening and mandibular protrusion, whereas the coronal plane (XoZ) offered a superior view during lateral protrusions. A parabola had good performance in fitting the trajectories of the condyle, incisor, and outlines with a superior goodness of fit (r2) during mouth opening and mandibular protrusion; linear functions were suitable for fitting the trajectories of the contralateral condyle during lateral protrusions. The velocity during the opening process was lower than that during the closing process, and so were the accelerations. The sagittal space between the articular eminences and condyles during mouth opening and mandibular protrusion were close, 2.8 and 2.7 mm, respectively. The sagittal space, velocity, and acceleration can provide dynamic information of TMJs. Three-dimensional motion analyses of temporomandibular joints during the mandibular motions were conducted to exact the mathematic information of temporomandibular joints. From curve fitting process, the fluctuation can be eliminated and the dynamic information can be obtained. And the parabola was better for the condylar trajectories in the sagittal plane of opening and mandibular protrusion. As to the lateral protrusions, the linear function is suitable for the condylar trajectories in coronal plane. The condylar curve of asymptomatic subjects can set as a reference to diagnose and treat for the patients with associated dysfunctions.

Three-dimensional finite element analysis of temporomandibular joints in patients with jaw deformity during unilateral molar clenching before and after orthognathic surgery.

ABSTRACT: To analyze the effects of orthognathic surgery on stress distributions in the temporomandibular joint (TMJ) of patients with jaw deformity during unilateral molar clenching (UMC) by using three-dimensional (3D) finite element method.Nine patients with jaw deformity (preoperative group, 26.1 ±â€Š5.6 years old) and 9 asymptomatic subjects (control group, 22.0 ±â€Š6.0 years old) were selected. Furthermore, the patients with jaw deformity were also considered as the postoperative group after undergoing orthognathic surgery. Finite element models for the mandible, articular disc, and maxilla were developed through cone beam computed tomography. Contact was used to simulate the interaction of the articular disc, condyle, fossa, and upper and lower dentition. The muscle forces and boundary conditions corresponding to the UMC were applied on the models.The stresses on both TMJs of the control group were significantly different, whereas there was no significant difference on both sides for the preoperative group. All the stresses of the preoperative group were greater than those of the control and postoperative groups, except the minimum principal stress on the ipsilateral fossa.Orthognathic surgery is beneficial for alleviating the abnormal stress distributions on TMJ.