The mechanical overloading of temporomandibular joint (TMJ) is generally linked to temporomandibular disorders (TMD). However, in patients with a typical combination of maxillofacial morphology and occlusal features, the reduction of joint load and treatment with general occlusal splints are often ineffective. This study investigates the biomechanical behavior of the stomatognathic system in a TMD patient with personalized splints by finite element analysis. The therapeutic position, determined based on the intercuspal position, served as the basis for designing personalized customized splints. The design of occlusal contact and splint structure was evaluated in terms of their impact on the maximum stress level in the TMJ and the biting forces on the dentition. The relationship between joint stress and biting force was further examined during treatment with different customized splints. In preoperative case, there was a significant increase in stress level and stress concentration in the medial to posterior band of the articular disc. However, in all customized splint cases, the highest stress area shifted to the intermediate zone and exhibited a decrease. Notably, the bi-splints demonstrated superior ability in relieving overloading and balancing the occlusal force on both sides of the dentition, as verified by clinical treatment. The predictable simulated results offer valuable interactive information regarding TMJ overload, aiding doctors in making better-informed clinical decisions in future.
A model of the temporomandibular joint (TMJ) was developed using the finite element method (FEM). The aim of the procedure is to identify reduced stresses and resultant displacements in the TMJ and to evaluate the transfer of contact loads for the three articulation states of the mandible that represent the activity of the joint. The study mapped the layered structure of the bio-bearing with different strength parameters of the tissues and synovial fluid. The model was loaded with the forces generated by the mandibular abduction muscles during chewing. Our method allowed for the assessment of the transfer of physiological loads within surfaces when lubricating with the synovial fluid and showed compressive stimulation of bone structures. Under load transfer conditions, the maximum values of reduced stresses are located not in the immediate friction zone, but in the structures of the compact and spongy bone.
PL
Opracowano model stawu skroniowo-żuchwowego (SSŻ) z wykorzystaniem metody elementów skończonych (MES). Celem jest identyfikacja naprężeń zredukowanych i przemieszczeń wypadkowych w SSŻ oraz ocena przeniesienia obciążeń kontaktowych dla trzech stanów artykulacyjnych żuchwy, które są reprezentatywne dla czynności tego stawu. W badaniu odwzorowano warstwową budowę biołożyska o zróżnicowanych parametrach wytrzymałościowych tkanek oraz cieczy synowialnej. Model obciążono siłami generowanymi przez mięśnie odwodzące żuchwę w warunkach żucia pokarmów. Zaproponowana metoda pozwoliła na ocenę przeniesienia obciążeń fizjologicznych w stawie skroniowo-żuchwowym. Umożliwiła analizę funkcjonalną krążka stawowego i powierzchni stawowych w warunkach smarowania cieczą synowialną oraz wskazała na stymulację kompresyjną struktur kostnych. W warunkach przenoszenia obciążeń maksymalne wartości naprężeń zredukowanych zlokalizowane są nie w bezpośredniej strefie tarcia, ale w strukturach kości korowej i gąbczastej.
Purpose: This study aimed to analyze the changes of the stress distributions in TMJs for the pre- and postoperative patients with mandibular prognathism under unilateral occlusions, a frequent occlusion in mastication. Methods: Pre- and six-mouth postoperative cone-beam computed tomography images of thirteen patients diagnosed with mandibular prognathism were scanned and used to construct complete maxillofacial models, assigned as the Pre and Post group, respectively. Another ten asymptomatic individuals were defined as the Control group. The inhomogeneous properties were assigned to the models. The muscle forces and boundary conditions corresponding to left and right unilateral occlusions were applied on the models. The analysis of variation (ANOVA) was chosen for the comparison among the groups. Results: The results showed that the Pre group had abnormal stress distributions ang higher stress level in TMJs, compared with those of the Post and Control groups. Moreover, from clinical cases, symptoms of temporomandibular disorders (TMDs) always followed with increased stresses. Conclusion: Generally, orthognathic surgeries could improve the stress distribution in TMJs of the patients with mandibular prognathism under the unilateral occlusions. However, the postoperative complications, especially symptoms of TMD, were closely related to changes of stress for patients with mandibular prognathism after orthognathic surgeries. Individual virtual surgery and finite element analysis should be conducted to prevent complications in TMJ.
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Poniższy artykuł opisuje budowę oraz biomechanikę stawu skroniowo-żuchwowego pod względem pomiarów przemieszczenia żuchwy względem czaszki. Jest to wstęp do opracowania metody pomiaru przemieszczeń żuchwy w ramach projektu POIR.04.01.02-00-0029/17, którego celem jest opracowanie trójwymiarowego modelu stawu skroniowo-żuchwowego w celu odwzorowania działania aparatu kostno-chrzęstnowięzadłowego na potrzeby protetyki, ortodoncji i chirurgii ortognatycznej.
EN
The following article describes the structure and biomechanics of the temporo-mandibular joint in terms of measurements of the mandibular dislocation relative to the skull. This is the introduction to the development of the method of measurement of mandibular movements as part of the project POIR.04.01.02-00-0029 / 17, whose aim is to develop a three-dimensional model of the temporomandibular joint to reproduce the operation of the osteochlear-ligament apparatus for the needs of prosthetics, orthodontics and orthognathic surgery.
The temporomandibular (TM) joint is one of the most active joints in the human body, and any defect in this joint has a significant impact on the quality of life. The objective of this study was to analyze changes in the force ratio after TM joint replacement on contralateral TM joint loading. Implantation of an artificial TM joint often requires removal of 3 of the 4 masticatory muscles (activators). In order to perform true loading of the TM joint, loading during mastication was investigated. Input kinematic variables and mastication force were experimentally examined. The inverse dynamics approach and static optimization technique were used for solution of the redundant mechanism. Muscle forces, and reactions in the TM joint were calculated. We modified the model for several different tasks. The m. temporalis and m. masseter were removed individually and together and the forces of mastication on the TM joint were calculated for each variation. To evaluate the results, a parametric numerical FE analysis was created to compare the magnitude of the TM joint loading during the bite process for four different muscle resections. The results show an influence relative to the extent of muscle resection on contralateral TM joint loading in a total TM joint replacement. The biggest increase in the loading magnitude on the contralateral TM joint is most evident after m. masseter and m. temporalis resection. The results from all simulations support our hypothesis that the greater the extent of muscle resection the greater the magnitude of contralateral TM joint overloading.
Purpose: Patients with spasticity suffer not only from neurological problems but also from various dentistry problems due to spasticity of the jaw muscles. Measurements of motion in temporomandibular joints should reflect the amount of abnormal muscle tone of these muscles. The aim of this study was to find out if the measurements of temporomandibular joint movements performed with the ultrasound Zebris device are different in cerebral palsy patients than in healthy subjects; and to find out if the information on the degree of spasticity in the lower legs provided by the Wartenberg test could be used to predict the degree of spasticty in the jaw muscles. Method: Twenty five healthy subjects and 25 cerebral palsy patients participated in the study. Two types of measurements were performed: temporomandibular movements measured with Zebris device, and instrumented Wartenberg test. Results: The laterotrusion and opening movements are different in CP patients than in healthy subjects. Laterotrusion movement correlates with velocity measured during the Wartenberg test. Conclusion: This finding suggests that high spasticity in the lower legs could indicate jaw movement restrictions in CP patients.
Celem pracy była elektromiograficzna ocena i porównanie aktywności bioelektrycznej wybranych mięśni układu stomatognatycznego dwóch osób dotkniętych dysfunkcją stawu skroniowo – żuchwowego (ang. temporomandibular disorders - TMD) o różnym stopniu nasilenia, oraz osoby zdrowej deklarującej brak objawów TMD.
EN
The aim of the study was an electromyography assessment and comparison of stomatognatic system’s selected muscles bioelectrical activity. The material consisted of two subjects who suffers from differential intensity of temporomandibular disorders (TMD) and the another one who’s healthy and doesn’t declare symptoms of TMD
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The paper presents the results of a study on mechanical properties of porcine temporomandibular joint discs. Taking into account anatomical properties, three typical spots were selected for the investigation: the posterior, anterior and central parts of the disc. The main focus was on the influence of samples' preparation on the changes in mechanical properties. Complete undamaged discs, cylindricallycut disc samples of 5 mm in diameter as well as discs of locally broken continuity in the upper layer around the measuring zone were prepared. Periodic compression was applied during testing, by varying the force in a sawtooth control signal. The rate of increasing the force applied equalled 1 N/s with a maximum value of 3 N. Based on the stress and strain characteristics obtained, the object's rigidity, Young's modulus of the samples, and effective Young's modulus of joint discs were calculated. Results showed that the stress and strain characteristics of the discs' substance depend on sample preparation, measurement location and load history within a given number of cycles. Only the fifth load cycle may be considered as stabilized. The most rigid proved to be the posterior part of the disc, as the rigidity of the samples, of an incised disc and of a complete disc in the fifth loading cycle amounted to 117.9 N/mm, 88.8 N/mm and 87.1 N/mm, respectively. A central part of the disc exhibited the lowest rigidity, whose values for the samples, for an incised disc and for a complete disc reached 87.9 N/mm, 70.6 N/mm, and 38.7 N/mm, respectively. Excision of the samples resulted in their dehydration, which led to increased rigidity, as reflected by Young's modulus values. In the posterior part of the disc, the modulus value was 12.56 MPa, while in the anterior part and in the center, these values reached 7.25 MPa and 6.99 MPa, respectively. Excised discs also exhibited dehydration effects during examination. While loading complete discs, the lowest effective values of Young's modulus were obtained, despite the influence of the tissues adjacent to the loaded zone, counteracting deformation. The values were 4.44 MPa, 1.97 MPa and 2.99 MPa for the posterior, central and anterior parts, respectively. Present data allow the conclusion that the error introduced due to breaking the tissue continuity is greater than the error resulting from ignoring substance continuity when applying local loads to an undamaged disc. Therefore, it seems more sensible to adopt the effective Young's modulus values in numerical analyses rather than to apply the results obtained for the samples cut out of discs.
The purpose of this paper is to develop a new complete replacement of the temporomandibular joint (TMJ). A three-dimensional finite element model of the temporomandibular joint has been developed according to the CT data. The model consists of a half skull, a half mandible and a temporomandibular joint disc. Stress analysis of TMJ during normal occlusion was carried out using non-linear finite element analysis (FEA). The model consists of 54 758 elements and 16 665 nodes. Material properties were obtained from previously published data and were considered to be isotropic and linear. Contact surfaces were defined between the temporomandibular disc and the mandibular condyle and between the temporomandibular disc and the fossa eminence on the skull. Between contact surfaces a finite sliding was allowed. Stresses in the TMJ components (disc, mandible condyle and the fossa eminence on the skull) were obtained. The results have shown stress distribution during normal occlusion.
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The masticatory system, which is also referred to as the stomatognathic system, consists of the temporomandibular joints, dentoalveolar apparatus, dentodental junctions and the neuromuscular complex. This articlc prcsents the relations between various joints under both physiological and pathological conditions.