The Biomechanics Research Of Condylar Defects Reconstructed With Artificial Temporomandibular Joint

BackgroundTemporomandibular joint is one of the most complex joints in the human body, is a rotating and sliding motion of linkage around the joints. The stability of the anatomical structure and determines the flexible joint has important physiological functions, including participation in mastication, speech, swallowing and facial expressions, etc. The temporomandibular joint disease, such as the jaw joints stiffness, mandibular tumor involving the condylar and can’t reset after condylar fracture fixed and other diseases often need to partial or total removal of condylar, it is difficult to keep good relationship with the jaw and chin postoperative function, the patients with facial deformity, occlusal disorders caused by serious influence the patient’s quality of life.At present, human temporomandibular joints have to mimic the normal anatomic morphology, laminating, don’t need to be further out, with the host and immediate postoperative function training and avoid osseous adhesion, makes artificial TMJ articular reconstruction clinical can choose one of the effective methods. But with artificial knee joint, hip joint gap on the success rate of repair, significantly lower. Can lead to repair the failure of a variety of reasons, such as material cause inflammation, nearly titanium prosthesis fracture stress concentration, because titanium screw nail and appearance shortage and the joint area of stress caused by bone joint fracture, etc. To the main reason for the artificial inappropriate in the temporomandibular joint prosthesis repair material and improper fixed design. At present a lot of research on artificial temporomandibular repair defect effect mainly through in vitro animal experiments and clinical cases were retrospectively summarized, can accurately show the artificial force when the temporomandibular joint prosthesis and bone on the stress distribution and the change. The ideal human temporomandibular joint fixed way and titanium nail requirements is not exact. Due to artificial temporomandibular joints are single side retainer, the appearance of the artificial condylar prosthesis, retainer, titanium nail design, quantity and distribution will be an important impact on the retention and stability, and good design and shape retention and stability is the necessary premise of prosthetic function, artificial temporomandibular joint biomechanics research of applied mechanics principle and method of artificial joints, the stress distribution and the change in quantitative research, has good prospects for development.ObjectiveThis experiment using computed tomography (CT) scanning technology, three-dimensional reconstruction, reverse and finite element calculation of engineering software:Free Form, Mimics, Geomagic, Solid works, ANSYS Workbench, etc., was established by a single tooth of mandibular three-dimensional finite element model of complete denture, analysis in the side of the condylar defect cases, human temporomandibular joint reconstruction after the joint, masticatory force loading of mandibular, artificial temporomandibular joint, stress distribution and influence of titanium nail, analyzed the human temporomandibular joint reconstruction of mandibular stress distribution and displacement trend; Through the establishment of condylar defect prosthesis replacement three-dimensional finite element model, reveal the different characteristics in the reconstruction of condylar defect repair modes and relationship, for the development of the new type of joint prosthesis and clinical prosthetic restoration application to provide laboratory data support.Materials and MethodsPart I Artificial temporomandibular joint reconstruction on the right side of condylar defect digital model1. Model data sources:according to research needs, choose south, southern medical university affiliated hospital of oral and maxillofacial surgery a healthy female volunteers,26, mandible and temporomandibular joint disease and abnormal shape, there is no history of trauma surgery, dentition occlusal complete, normal. And volunteers agreed after a CT scan.2. Data access:the German SIEMENS company64CT scanned for mandibular continuous level. Scan parameters:1mm, with a thick layer of the tube current200mA, voltage120kV. The object of study in supine position, cross beam, localization scanning baseline and orbital plane parallel the ear, orbital ear and the plane perpendicular to the plane. Scan range:on the superior border of condylar, next to the edge of mandible, the image data in DICOM format.3. Mandibular simulation of three-dimensional finite element model is established in this paper, by using CT scanning head image data in Dicom format input3d reconstruction software Mimics Materialise company (Belgium), export to the STL file format and enter to the reverse engineering software Geomagic software, smooth, polished, denoising and a series of image processing, generate3d graphics IGES file format, get complete normal mandible model.4. Finite element model of right mandibular condylar defect implementation:in normal condylar model, on the basis of the mandibular three-dimensional entity model data import ANSYS Workbench (ANSYS company, USA), the entity cutting function by using ANSYS, so as to the working plane to cut parts for Boolean operation, remove the right side of the condylar, simulated defect after condylar excision (sigmoid notch level) and to establish a three-dimensional model on the right side of mandibular condylar defect. 5. Artificial temporomandibular joint and titanium nail of the three-dimensional entity model:according to the clinical use of human temporomandibular joint prosthesis model is set up, titanium nail using simplified model, the cylinder model, diameter is2.0mm,2.5mm and3.0mm respectively three titanium nail. Using three-dimensional CAD software Solidwork (French dassault company) for artificial temporomandibular joints, titanium nail, modeling.6. Three different artificial temporomandibular joint diameter titanium nail fixed model establishment:the human temporomandibular joint, titanium screw3d model data is input into the mandibular condylar defect on the right side in the3d model, and according to the experiment of different diameter titanium nail fixed assembly with artificial temporomandibular joints. Way I:2.0mm diameter titanium nail in artificial joint handle and temporomandibular joint fixed jaw rises a place, down the same distance apart from the condylar defect fixed three; From to edge of mandibular condylar direction in turn into1titanium nail,2stars titanium nail,3star titanium nail. Way II:2.5mm diameter titanium nail conditions at the same position; WayⅢ:3.0mm diameter titanium nail at the same location conditions.7. Finite element mesh model:the mandibular model and fixed components adopt Workbench default Solid187Solid elements, division, mandibular model of cell size2.5mm, artificial TMJ model1mm. Establish human temporomandibular joint reconstruction condylar defect in three different diameter titanium nail fixed three-dimensional finite element model.PartⅡ Artificial temporomandibular joint biomechanics analysis of condylar defect reconstruction1. The boundary conditions:on the left mandibular condylar completely fixed, the right side of the fixed human temporomandibular joint top, front end fixed front teeth. Static mechanics finite element calculation and analysis, open the large deformation effect, set up the model boundary conditions.2. Contact Settings:in the Workbench, mandibular cortical bone and cancellous bone is completely fixed. Cortical bone to Bond with the teeth contact (binding), titanium nail into the lower jaw is also set to Bond after contact, set up the cortical bone and artificial temporomandibular joint joint handle Frictional contact between the friction coefficient is0.42.3. Bite force loading and mandible bone biomechanics analysis:simulated masticatory muscle bite resultant force direction, in bilateral mandibular Angle oblique loading force of200N, on the lower jaw and three different artificial temporomandibular joint titanium nail fixed model, equivalent stress and the calculation of the displacement analysis and interception of artificial temporomandibular joint and the mandible bone joint the same site, analysis of different titanium nail fixed biomechanical characteristics of the way.4. Artificial temporomandibular joints, titanium nail biomechanics analysis: occlusal loading extraction of artificial temporomandibular joints in three different fixed way, titanium screw displacement and stress distribution, stress concentration of biomechanics analysis, in combination with bone biomechanics characteristic, analyzing the characteristics of the artificial TMJ stress itself and comparing three different titanium nail under stress intensity and stability.Part III New artificial temporomandibular joint design and biomechanics analysis1. New artificial temporomandibular joint design:based on the clinical use of artificial TMJ condylar and mandibular branch of applied anatomy, design a new type of artificial temporomandibular joints. New artificial temporomandibular joint consists of three parts:the rotating disc, the connecting body, even the hole prosthesis.2. Contact Settings:same as the second part, the lower jaw is set to Bond contact, cortical bone and artificial temporomandibular joint joint handle Frictional contact between the friction coefficient is0.42.3. New artificial mandibular temporomandibular joint biomechanics analysis: under the same conditions in the second section, and interception of artificial temporomandibular joint and the mandible bone joint the same site, analysis of the new human temporomandibular joint biomechanics characteristics of mandible.4. New artificial temporomandibular joints, titanium nail biomechanics analysis: occlusal loading under the new artificial temporomandibular joints, titanium screw displacement and stress distribution, stress concentration, biomechanics analysis combined with biomechanical characteristics of mandible, compared with the traditional joint analysis of the new artificial good biomechanical characteristics of the temporomandibular joint itself.Results1. Using CT precision scanning acquisition healthy adult volunteers mandibular data, through3d reconstruction software Mimics successfully established normal mandible3d entity model, the model contains the complete denture, cancellous bone and cortical bone, and has good geometric similarity.2. In mandibular complete3d finite element model based on the right side of condylar defect model was established, and the human temporomandibular joint for fixed-point assembly, set up under the three different titanium nail fixation of condylar defect model of artificial temporomandibular joint reconstruction.3. Bilateral mandibular Angle of bite after loading for three different diameter titanium nail fixed after mandibular biomechanical characteristics:From mandibular equivalent stress distribution, the lower jaw of the maximum stress concentration in the condylar recently1of titanium nail hole, from condylar to the first2titanium nail and three titanium nail hole stress significantly decreased; Mandibular maximum equivalent stress value is:3nail hole area<2nail hole area<1nail hole area; With the increase of titanium screw diameter, mandibular maximum equivalent stress value decreases; The way Ⅲ<ⅡIway<Ⅰ way.4. Artificial temporomandibular joint and the titanium nail stress analysis:Through artificial stress distribution of the temporomandibular joint, we found that the maximum stress concentration part located in artificial joint head of temporomandibular joint and joint handle border area, to stress weak spot. Titanium nail its maximum equivalent stress distribution is:3titanium nail<2titanium nail<1titanium nail. Maximum stress value with the increase of titanium screw diameter:3.0mm diameter titanium nail<2.5mm diameter titanium nail<2.0mm diameter titanium nail.5.The biomechanical characteristics of the new type of artificial temporomandibular joint:Overall equivalent stress distribution:mandibular overall stress value are smaller, has not been beyond the breakdown strength of bone, bone cortex uniform stress value less than108Mpa. Side3hole at the peak stress zone from top to bottom:3nail hole<2nail hole<1nail hole. Local equivalent stress distribution: mandibular rise with the truncation plane stress area, for connecting the conduction nail hole area,artificial temporomandibular joint equivalent stress distribution in the joint of joint head and joint handle stress larger area appear red. Titanium nail equivalent stress distribution:titanium nail equivalent stress distribution can be seen that the peak stress into3titanium nail<2titanium nail<1titanium nail, from top to bottom in turn. Mandibular overall deformation distribution:mandibular overall deformation, deformation degree on the mandibular Angle to the right, the largest of the whole deformation distribution in the mandibular basic symmetry.Conclusions1. CT scans obtained data, the use of3d reconstruction software Mimics combination of reverse engineering software to establish a mandibular three-dimensional finite element model of complete denture, the level is clear, has excellent geometric similarity. Reverse engineering software for mandibular model is smooth, polished, denoising and a series of processing, model is more close to the real, can be divided into a single tooth of complete denture, cancellous bone and cortical bone; With the phase of the clinical, mandibular biomechanical characteristics analysis more accurate;ood foundation for the further mandibular biomechanical characteristics analysis. 2. Mandibular equivalent stress analysis confirmed that near to the first hole of condylar area, there is an obvious stress concentration phenomenon, too much stress will lead to bone absorption, resulting in titanium nail loose, reduce artificial temporomandibular repair defects of success; With the increase of titanium screw diameter, mandibular maximum equivalent stress shows the trend of decrease; In clinical applications, the need to consider first the stress concentration phenomenon of nail hole area, through the design of the new artificial temporomandibular joint or increase titanium nail diameter makes the stress distribution near normal mandible biomechanical characteristics of the stress, is beneficial to promote healing of the area, and the long-term success rate of repair.3. Artificial temporomandibular joint and titanium nail equivalent stress analysis confirmed that the joint handle and joint stress of the border area for prosthetic head vulnerabilities, artificial design should consider the characteristics of the temporomandibular joint; Titanium screw in as the diameter increases, the maximum equivalent stress of titanium nail itself is reduced, the prompt appropriate increase titanium nail diameter can increase the stability of titanium nail.4. New artificial temporomandibular joint design can make the most of the mechanical transmission by connecting body to condylar fracture, reduced the stress of the titanium nail side, increase the stability of the prosthesis; New type of prosthesis will force well dispersed to cross section, to alleviate the stress of the titanium nail, the nail3uniform stress distribution obviously, far smaller, avoid the mandibular caused by excessive stress absorption; Overall deformation also reflects the new artificial temporomandibular joints can be a good way to ensure mandibular stress and deformation on the symmetry. New human temporomandibular joint has good biomechanical properties of artificial temporomandibular joint for clinical improvement and reconstruction provides the reference for condylar defect.