Design and development of a patient-specific temporomandibular joint implant: Probing the influence of bone condition on biomechanical response

Total temporomandibular joint (TMJ) replacement is widely recognized as an effective treatment for TMJ disorders. The long-term stability of TMJ implants depends on two important factors which are design concepts for fixation to anatomical locations in the mandible and bone conditions. Other factors include stress distribution, microstrain in the peri-implant, bone attributes like bone conditions leading to the clinical complications and failures. This study addresses these limitations by examining the influence of patient-specific design concepts and bone conditions on TMJ implant performance. Clinical evidences support the importance of implant design on healing ability. Previous studies have focused on achieving precise implant fit based on geometric considerations, however those published studies did not explore the impact of such. Against this perspective, the present study reports the extensive finite element analysis (FEA) results, while analyzing the impact of a newly designed patient-specific TMJ implant to address clinical complications associated with various bone conditions, particularly osteoporotic bone. In validating the FEA results, the performance of additively manufactured patient-specific TMJ implants was compared with designs resembling two commonly used clinically approved implant designs. By addressing the limitations of previous research and emphasizing the importance of bone conditions, the study provides valuable guidelines for the development of next-generation TMJ implants. These findings contribute to enhanced clinical outcomes and long-term success in the treatment of TMJ disorders.

Biomechanical Evaluation of a Standard Temporomandibular Joint Prosthesis and Screw Arrangement Optimization: A Finite Element Analysis

BACKGROUND AND OBJECTIVE

Artificial total joint replacement is an important method of temporomandibular joint (TMJ) reconstruction, which has been advocated for TMJ osteoarthrosis, ankylosis, tumors, and other diseases. We designed one type of standard TMJ prosthesis fit for Chinese patients. This study aimed to explore the biomechanical behavior of the standard TMJ prosthesis using finite element analysis and selects an optimal screw arrangement scheme for clinical application.

MATERIALS AND METHODS

A female volunteer was recruited for a maxillofacial computed tomography scan, then the Hypermesh software was used to establish a finite element model of a mandibular condyle defect repaired with an artificial TMJ prosthesis. An advanced universal finite element program software was used to calculate the stress and deformation under a simulated maximum bite force loading. Also, the forces of screws under different numbers and arrangements were analyzed. Meanwhile, we designed an experiment to verify the calculation model.

RESULTS

The average maximum stress of the fossa component of the standard prosthesis model was 19.25 MPa. The average maximum stress of the condyle component was 82.58 MPa, mainly concentrated near the top row hole. The fossa component should be fixed with at least 3 screws, and the optimal number of screws was 4. The condyle component should be fixed with at least 4 screws, and its optimal number was 6. The best scheme of screw arrangement was determined. The results of the verification experiment showed that the analysis was reliable.

CONCLUSIONS

The stress distribution of the standard TMJ prosthesis is uniform, meanwhile, the number and arrangement of the screws significantly affect the contact force of the screws.

Reconstruction of the mandibular condyle due to degenerative disease

Degenerative joint disease (DJD), also known as osteoarthritis is the most common form of arthritis and can affect the temporomandibular joint (TMJ). TMJ DJD is characterized by degradation of the articular cartilage and synovial tissues resulting in characteristic morphologic changes in the underlying bone. DJD can occur at any age, but it is more common in older age groups. TMJ DJD may be unilateral or bilateral. The American Academy of Orofacial Pain categorizes TMJ DJD into primary and secondary types. Primary DJD is seen in the absence of any local or systemic factors and secondary DJD is associated with a prior traumatic event or disease process. Frequently, these patients present with pain and limited residual mandibular function resulting in significantly diminished quality of life. Classic radiographic features on orthopantogram and CT imaging include loss of joint space, osteophytes (bird-beak appearance of the condyle), subchondral cysts, erosions, flattening of the condylar head, bony resorption and/or heterotopic bone (Figure 1). Conservative and medical management is successful in the majority of patients until the active degenerative phase burns out, but some will progress to end stage joint disease and require reconstruction of the TMJ. Reconstruction of the mandibular condyle should be considered to restore mandibular function and form to patients who have lost it secondary to degenerative joint disease affecting the glenoid fossa/mandibular condyle unit.

Influence of implant parameters on biomechanical stability of TMJ replacement: A finite element analysis

The articular disc reduces the stress distribution from the mandible to fossa. In total temporomandibular joint (TMJ) replacement, the implant is required to reduce the stress on fossa implant. Current studies lack standard and optimized parameters for the cylindrical dome on Christensen TMJ implant collar. This study briefed a novel TMJ implant head design and investigates the biomechanical behaviour by considering the articular disc. The radius of the head was varied with the height of the cylinder height to obtain the design of the experiment and the stress distribution was compared with an intact mandible-articular disc model by considering the viscoelastic property of the TMJ disc. The model was simulated at three different angles: 20°, 0° and -20° in the mediolateral direction to simulate the manducation. FEA analysis showed high stresses at the circular heads, and high strength is achieved with increased implant cylinder length and diameter. The results also showed a stress reduction of 50% on the fossa from the mandible. Hence, the newly designed head and suggested modifications may be used as a reference for further clinical improvement of Christensen TMJ as well as other TMJ implants.

Design and Finite Element Analysis of Patient-Specific Total Temporomandibular Joint Implants

In this manuscript, we discuss our approach to developing novel patient-specific total TMJ prostheses. Our unique patient-fitted designs based on medical images of the patient’s TMJ offer accurate anatomical fit, and better fixation to host bone. Special features of the prostheses have potential to offer improved osseo-integration and durability of the devices. The design process is based on surgeon’s requirements, feedback, and pre-surgical planning to ensure anatomically accurate and clinically viable device design. We use the validated methodology of FE modeling and analysis to evaluate the device design by investigating stress and strain profiles under functional/normal and para-functional/worst-case TMJ loading scenarios.

Biomechanical Analysis of Patient-Specific Temporomandibular Joint Implant and Comparison with Natural Intact Jaw Bone Using Finite Element Method

The purpose of this study is to design a patient-specific TMJ implant and study its behaviour under different loading conditions compared with natural intact TMJ. There are several diseases, which affect the proper growth and function of TMJ, and in some cases, TMJ injury results from accidents. To repair the TMJ, temporomandibular joint replacement or TJR surgery is performed. In this work, CT-scan data of the skull and mandible region with broken condylar head were used to study the biomechanical behaviour of the intact mandible and customized TMJ prostheses in order to design a patient-specific total TMJ implant. The customized TMJ implant was virtually studied under simulated loading conditions using finite element method (FEM) in ANSYS Workbench and then compared to the intact jaw-mandible for the combinations of two different biocompatible material models. It is observed that the natural TMJ has a higher deformation value as compared to the patient-specific TMJ implant due to the lower mechanical strength of bone relative to the Ti-6Al-4V and Co-Cr alloy. Hence, we can conclude that the designed custom TMJ implant is safe for the patient from the point of design perspective.

Biomechanical analysis of a temporomandibular joint prosthesis for lateral pterygoid muscle reattachment

OBJECTIVE

To analyze the biomechanical properties of a novel temporomandibular joint (TMJ) prosthesis with an attachment area for the lateral pterygoid muscle (LPM).

STUDY DESIGN

Three prosthesis models were created and compared using finite element analysis for the displacement, stress, and strain when simulating the maximum bite force loading. A verification experiment and a compression test were conducted.

RESULTS

The displacement, stress, and strain of the novel TMJ prosthesis were larger than the solid condylar neck prosthesis and similar to the slotted condylar neck prosthesis, but the values were far less than the yield strength of titanium alloy. The maximum stress and strain in the novel TMJ prosthesis was concentrated in the inner and boundary areas of the LPM reattachment region beside the thinnest part of the prosthesis neck. The difference in the strain values measured using the verification test and those using finite element analysis was <20%. Compression testing of the novel TMJ prosthesis revealed that the mandible fractured when the force reached 588.97 N, whereas the prosthesis itself did not break or deform.

CONCLUSIONS

The mechanical distribution of the novel prosthesis was feasible under maximum bite force for potential clinical application.

Biomechanical evaluation of a customized 3D-printed polyetheretherketone condylar prosthesis

The present study aimed to evaluate the biomechanical behavior of a custom 3D-printed polyetheretherketone (PEEK) condylar prosthesis using finite element analysis and mechanical testing. The Mimics software was used to create a 3D model of the mandible, which was then imported into Geomagic Studio software to perform osteotomy of the lesion area. A customized PEEK condyle prosthesis was then designed and the finite element model of the PEEK condyle prosthesis, mandible and fixation screw was established. The maximum stress of the prosthesis and screws, as well as stress and strain of the cortical and cancellous bones in the intercuspal position, incisal clench, left unilateral molar clench and right unilateral molar clench was analyzed. The biomechanical properties of the prosthesis were studied using two models with different lesion ranges. To simulate the actual clinical situation, a special fixture was designed. The compression performance was tested at 1 mm/min for the condyle prosthesis, prepared by fused deposition modeling (FDM). The results of a finite element analysis suggested that the maximum stress of the condyle was 10.733 MPa and the maximum stress of the screw was 9.7075 MPa; both were far less than the yield strength of the material. The maximum force that the two designed prostheses were able to withstand was 3,814.7±442.6 N (Model A) and 4,245.7±348.3 N (Model B). Overall, the customized PEEK condyle prostheses prepared by FDM exhibited a uniform stress distribution and good mechanical properties, providing a theoretical basis for PEEK as a reconstruction material for repairing the temporomandibular joint.

Biomechanical evaluation of Chinese customized three-dimensionally printed total temporomandibular joint prostheses: A finite element analysis

PURPOSE

This work aims to evaluate the biomechanical behavior of Chinese customized three-dimensional (3D)-printing total temporomandibular joint (TMJ) prostheses by means of finite element analysis.

METHODS

A 3D model was established by Mimics 18.0, then output in a stereolithography (STL) format. Two models were established to investigate the strain behaviors of an intact mandible and a one-side implanted mandible respectively. Hypermesh and LS-DYNA software were used to establish computer-aided engineering finite element models. The stress distribution on the custom-made total TMJ prosthesis and the strain distribution on the mandible were analyzed by loading maximal masticatory force.

RESULTS

The maximum stress on the surface of the ultra-high-molecular weight polyethylene was 19.61 MPa. With respect to the mandibular component, the maximum stress in the mandibular component was located at the anterior and posterior surface of the condylar neck, reaching 170.01 MPa. The peak von Mises stress was observed on the topside screw of the mandible, which was found to be 236.08 MPa. For the intact model, it was observed that the strain distribution was basically symmetrical. For the model with the prosthesis, the curve of strain distribution was fundamentally consistent with that in the intact mandible, except for the last 24 mm along the control line. A prominent strain decrease between 41.4% and 58.3% was observed in this area.

CONCLUSIONS

Chinese customized 3D-printed total TMJ prostheses exhibit uniform stress distribution without changing the behavior of the opposite side natural joint. Furthermore, the prostheses have a great potential to be improved in design and materials with a promising future.

Influence of Deformation and Stress between Bone and Implant from Various Bite Forces by Numerical Simulation Analysis

Endosseous oral implant is applied for orthodontic anchorage in subjects with multiple tooth agenesis. Its effectiveness under orthodontic loading has been demonstrated clinically and experimentally. This study investigates the deformation and stress on the bone and implant for different bite forces by three-dimensional (3D) finite element (FE) methods. A numerical simulation of deformation and stress distributions around implants was used to estimate the survival life for implants. The model was applied to determine the pattern and distribution of deformations and stresses within the endosseous implant and on supporting tissues when the endosseous implant is used for orthodontic anchorage. A threaded implant was placed in an edentulous segment of a human mandible with cortical and cancellous bone. Analytical results demonstrate that maximum stresses were always located around the implant neck in marginal bone. The results also reveal that the stress for oblique force has the maximum value followed by the horizontal force; the vertical force causes the stress to have the minimum value between implant and bone. Thus, this area should be preserved clinically to maintain the structure and function of a bone implant.

A personalized 3D-printed prosthetic joint replacement for the human temporomandibular joint: From implant design to implantation

Personalized prosthetic joint replacements have important applications in cases of complex bone and joint conditions where the shape and size of off-the-shelf components may not be adequate. The objective of this study was to design, test and fabricate a personalized 3D-printed prosthesis for a patient requiring total joint replacement surgery of the temporomandibular joint (TMJ). The new 'Melbourne' prosthetic TMJ design featured a condylar component sized specifically to the patient and fixation screw positions that avoid potential intra-operative damage to the mandibular nerve. The Melbourne prosthetic TMJ was developed for a 58-year-old female recipient with end-stage osteoarthritis of the TMJ. The load response of the prosthesis during chewing and a maximum-force bite was quantified using a personalized musculoskeletal model of the patient's masticatory system developed using medical images. The simulations were then repeated after implantation of the Biomet Microfixation prosthetic TMJ, an established stock device. The maximum condylar stresses, screw stress and mandibular stress at the screw-bone interface were lower in the Melbourne prosthetic TMJ (259.6MPa, 312.9MPa and 198.4MPa, respectively) than those in the Biomet Microfixation device (284.0MPa, 416.0MPa and 262.2MPa, respectively) during the maximum-force bite, with similar trends also observed during the chewing bite. After trialing surgical placement and evaluating prosthetic TMJ stability using cadaveric specimens, the prosthesis was fabricated using 3D printing, sterilized, and implanted into the female recipient. Six months post-operatively, the prosthesis recipient had a normal jaw opening distance (40.0 mm), with no complications identified. The new design features and immediate load response of the Melbourne prosthetic TMJ suggests that it may provide improved clinical and biomechanical joint function compared to a commonly used stock device, and reduce risk of intra-operative nerve damage during placement. The framework presented may be useful for designing and testing customized devices for the treatment of debilitating bone and joint conditions.

Prosthesis Loading After Temporomandibular Joint Replacement Surgery: A Musculoskeletal Modeling Study

One of the most widely reported complications associated with temporomandibular joint (TMJ) prosthetic total joint replacement (TJR) surgery is condylar component screw loosening and instability. The objective of this study was to develop a musculoskeletal model of the human jaw to assess the influence of prosthetic condylar component orientation and screw placement on condylar component loading during mastication. A three-dimensional model of the jaw comprising the maxilla, mandible, masticatory muscles, articular cartilage, and articular disks was developed. Simulations of mastication and a maximum force bite were performed for the natural TMJ and the TMJ after prosthetic TJR surgery, including cases for mastication where the condylar component was rotated anteriorly by 0 deg, 5 deg, 10 deg, and 15 deg. Three clinically significant screw configurations were investigated: a complete, posterior, and minimal-posterior screw (MPS) configuration. Increases in condylar anterior rotation led to an increase in prosthetic condylar component contact stresses and substantial increases in condylar component screw stresses. The use of more screws in condylar fixation reduced screw stress magnitudes and maximum condylar component stresses. Screws placed superiorly experienced higher stresses than those of all other condylar fixation screws. The results of the present study have important implication for the way in which prosthetic components are placed during TMJ prosthetic TJR surgery.

Finite element analysis of a condylar support prosthesis to replace the temporomandibular joint

This paper presents a finite element study of a temporomandibular joint (TMJ) prosthesis in which the mandibular component sits on the condyle after removal of only the diseased articular surface and minimal amount of condylar bone. The condylar support prosthesis (CSP) is customised to fit the patient and allows a large part of the joint force to be transmitted through the condyle to the ramus, rather than relying only on transfer of the load by the screws that fix the prosthesis to the ramus. The 3-dimensional structural finite element analysis compared a design of CSP with a standard commercial prosthesis and one that was modified to fit the ramus, to relate the findings to the different designs and geometrical features. The models simulated an incisal bite under high loading. In the CSP and in its fixation screws, the stresses were much lower than those in the other 2 prostheses and the bone strains were at physiological levels. The CSP gives a more physiological form of load transfer than is possible without the condylar contact, and considerably reduces the amount of strain on the bone around the screws.

Load transfer in Christensen(®) TMJ in alloplastic total joint replacement for two different mouth apertures

This study analyses load transfer in the fossa component based on two numerical models of total temporomandibular joint (TMJ) implants for two mouth openings. The TMJ articulation is a very complex system with muscles, ligaments and cartilage. Until now, studies of TMJ implants have analysed only condylar behaviour. The finite element models were constructed based on CT scans of a cadaveric mandible and cranium, considering the bone geometry and position. The influence of five principal muscle actions was simulated for two mouth positions, 5 mm and 15 mm openings at the incisive tooth support. Strain distributions into the surrounding bone tissue were analysed in both models in the condyle and fossa components. The results demonstrate that in Christensen(®) TJR of the temporomandibular joint the fossa component is the more critical part, presenting more stress near the screw holes and contact regions with the cranium. The most critical region is around the first two screws and the least critical is in the condyle component. For the mandible condyle reconstructed with a Christensen(®) prosthesis, the 15 mm mouth opening was more critical, as compression was increased, but for the fossa component the most critical situation occurred with the 5 mm opening. The micromovements observed suggest that the number of screws could be reduced to increase osteointegration of screws in the mandible condyle.

Enhancement of biomechanical behavior on osseointegration of implant with SLAffinity

The purpose of this study was to investigate stresses resulting from different thicknesses of hydroxyapatite- and titanium dioxide (TiO(2))-treated layers at the interface between temporomandibular joint (TMJ) implants and bones using three-dimensional finite element models. For ensuring osseointegration of implant treatment, one must examine the stresses of interface between implant and bone tissue. Treated layers on TMJ implants are a very important factor in clinical application. Several studies have investigated finite element models for TMJs, but few have examined a model for TMJ implants with treated layers. In this study, TMJ models were reconstructed using computer tomography data, and the effects of treated layer thickness on the stress field during jaw movement were investigated; this index has not yet been reported with respect to TMJ implant. The maximum stresses in the bone occurred at the position of the first screw. Data analysis indicated a greater decrease in this stress in the case of using TMJ implants with TiO(2)-treated layers, and the stresses decreased with increasing layer thicknesses. Results confirmed that the treated layers improve biomechanical properties of the TMJ implants and release abnormal stress concentration in them. The results of our study offer the potential clinical benefit of inducing superior biomechanical behavior in TMJ implants.

Influence of the TMJ Implant Geometry on Stress Distribution

The purpose of this study was to investigate the influence of Temporomandibular Joint implant geometry on stress distribution in total reconstruction of temporomandibular joint. A three dimensional model of a lower jaw of a patient was developed from a Computed Tomography scan images. Anatomical curvature and flat contact surface of implant design and fixation screws were modeled. Two implanted mandibles were then compared by means of finite element analysis. The muscle forces for incisal clenching were applied. The equivalent stress resulted in contact surface region of the bone and implant and in fixation screw holes were investigated to evaluate the designs. In applied loading condition, The results showed that anatomical design of implant was more preferred and it will lead to long-term success of implant.

Design Analysis of TMJ Implant under Physiological Loading Condition

Equal channel angular extrusion (ECAE) is a severe plastic deformation (SPD) method for obtaining bulk nanostructured materials. The ECAE die consists of two equal channels that intersect at an angle, usually between 90。and 135。. In the present study, the plastic deformation behavior of copper during the ECAE process with 120o die was investigated. To analyze the deformation behavior and the related strain distributions in the specimen, the commercial FE code ABAQUS has been used. The properties of the materials are strongly dependent on the shear plastic deformation behavior during equal channel angular extrusion (ECAE), which is controlled mainly by die geometry, material properties, and the friction between billet and the die. The ECAE process for these conditions was explained using the two different friction conditions of 0.15 and 0.08 to all sliding surfaces. The effective strain by the theoretical equation is in good agreement with the FEM results.

Current computational modelling trends in craniomandibular biomechanics and their clinical implications

Computational models of interactions in the craniomandibular apparatus are used with increasing frequency to study biomechanics in normal and abnormal masticatory systems. Methods and assumptions in these models can be difficult to assess by those unfamiliar with current practices in this field; health professionals are often faced with evaluating the appropriateness, validity and significance of models which are perhaps more familiar to the engineering community. This selective review offers a foundation for assessing the strength and implications of a craniomandibular modelling study. It explores different models used in general science and engineering and focuses on current best practices in biomechanics. The problem of validation is considered at some length, because this is not always fully realisable in living subjects. Rigid-body, finite element and combined approaches are discussed, with examples of their application to basic and clinically relevant problems. Some advanced software platforms currently available for modelling craniomandibular systems are mentioned. Recent studies of the face, masticatory muscles, tongue, craniomandibular skeleton, temporomandibular joint, dentition and dental implants are reviewed, and the significance of non-linear and non-isotropic material properties is emphasised. The unique challenges in clinical application are discussed, and the review concludes by posing some questions which one might reasonably expect to find answered in plausible modelling studies of the masticatory apparatus.