Distribution of stress on TMJ disc induced by use of chincup therapy: assessment by the finite element method.

OBJECTIVE: To assess the distribution of stress produced on TMJ disc by chincup therapy, by means of the finite element method. METHODS: a simplified three-dimensional TMJ disc model was developed by using Rhinoceros 3D software, and exported to ANSYS software. A 4.9N load was applied on the inferior surface of the model at inclinations of 30, 40, and 50 degrees to the mandibular plane (GoMe). ANSYS was used to analyze stress distribution on the TMJ disc for the different angulations, by means of finite element method. RESULTS: The results showed that the tensile and compressive stresses concentrations were higher on the inferior surface of the model. More presence of tensile stress was found in the middle-anterior region of the model and its location was not altered in the three directions of load application. There was more presence of compressive stress in the middle and mid-posterior regions, but when a 50o inclined load was applied, concentration in the middle region was prevalent. Tensile and compressive stresses intensities progressively diminished as the load was more vertically applied. CONCLUSIONS: stress induced by the chincup therapy is mainly located on the inferior surface of the model. Loads at greater angles to the mandibular plane produced distribution of stresses with lower intensity and a concentration of compressive stresses in the middle region. The simplified three-dimensional model proved useful for assessing the distribution of stresses on the TMJ disc induced by the chincup therapy.

Distribution of stress on TMJ disc induced by use of chincup therapy: assessment by the finite element method

ABSTRACT Objective: To assess the distribution of stress produced on TMJ disc by chincup therapy, by means of the finite element method. Methods: a simplified three-dimensional TMJ disc model was developed by using Rhinoceros 3D software, and exported to ANSYS software. A 4.9N load was applied on the inferior surface of the model at inclinations of 30, 40, and 50 degrees to the mandibular plane (GoMe). ANSYS was used to analyze stress distribution on the TMJ disc for the different angulations, by means of finite element method. Results: The results showed that the tensile and compressive stresses concentrations were higher on the inferior surface of the model. More presence of tensile stress was found in the middle-anterior region of the model and its location was not altered in the three directions of load application. There was more presence of compressive stress in the middle and mid-posterior regions, but when a 50o inclined load was applied, concentration in the middle region was prevalent. Tensile and compressive stresses intensities progressively diminished as the load was more vertically applied. Conclusions: stress induced by the chincup therapy is mainly located on the inferior surface of the model. Loads at greater angles to the mandibular plane produced distribution of stresses with lower intensity and a concentration of compressive stresses in the middle region. The simplified three-dimensional model proved useful for assessing the distribution of stresses on the TMJ disc induced by the chincup therapy.

RESUMO Objetivo: avaliar, por meio do método dos elementos finitos, a distribuição das tensões no disco articular produzidas pela mentoneira ortopédica. Métodos: um modelo tridimensional simplificado do disco articular foi desenvolvido com o software Rhinoceros 3D e exportado para o software ANSYS. Uma carga de 4,9 N (500 gf) foi aplicada na superfície inferior do modelo, com inclinação de 30, 40 e 50o em relação ao plano mandibular Gônio-Mentoniano (GoMe). O ANSYS analisou, por meio do método dos elementos finitos, a distribuição das tensões presentes no modelo do disco articular para as diferentes angulações. Resultados: os resultados mostraram que a concentração das tensões de tração e compressão foi maior na superfície inferior do modelo. A tensão de tração foi mais presente na região média-anterior do modelo, e sua localização não se alterou nas três direções da aplicação da carga. A tensão de compressão foi mais presente nas regiões média e média-posterior do modelo, mas quando a carga a 50o foi aplicada, ela se concentrou na região média. As intensidades das tensões de tração e compressão diminuíram progressivamente à medida que a carga foi aplicada mais verticalmente. Conclusão: as tensões induzidas pela mentoneira ortopédica se localizaram principalmente na superfície inferior do modelo. As cargas com maior angulação em relação ao plano mandibular produziram uma distribuição de tensões com menor intensidade e uma concentração da tensão de compressão na região média do modelo. Um modelo tridimensional simplificado se mostrou útil na avaliação da distribuição das tensões no disco articular induzidas pela mentoneira ortopédica.

Morphofunctional features of the temporomandibular joint / Aspectos morfofuncionales de la articulación temporomandibular

This article focuses on important morphofunctional features of the temporomandibular joint, particularly those related to the ultrastructure and anterosuperior attachment of the joint capsule and condylar position at the end of the mouth-opening movement.

Se focaliza importantes aspectos morfofuncionales de la articulación temporomandibular, especialmente aquellos relacionados a la ultraestructura e inserción antero-superior de su cápsula articular y la posición final del cóndilo, en el movimiento de apertura máxima bucal.

A direct anatomical study of the morphology and functionality of disco-malleolar and anterior malleolar ligaments / Estudio anatómico directo de la morfología y funcionalidad de los ligamentos disco-maleolar y maleolar anterior

The disco-malleolar and anterior malleolar ligaments are common to the middle ear, the temporomandibular joint and the jaw, all of them sharing a common embryological origin; these ligaments' morphometric and functional aspects were studied in 23 temporal bones. Experimental design: The epitympanum roof and the temporomandibular joint roof were elevated by micro-dissection of the middle cranial fossa, exposing both disco-malleolar and anterior malleolar ligaments and their association with the malleus, the temporomandibular joint disc and the mandibular lingula. Principal observations: Both ligaments start in the malleus and take anterior and divergent routes towards the temporomandibular joint and lingula, passing through Huguier's canal. The disco-malleolar and anterior malleolar ligaments' mean lengths were 6.88 mm (SD 0.81) and 4.22mm (SD 1.17), respectively, no statistically significant difference being revealed between the sides. Temporomandibular joint disc traction was applied for verifying malleus mobility; malleus movement was observed when applying disco-malleolar traction in 30.5% of the samples. Correlation was observed between malleus movement and disco-malleolar length (R2=-0.499, p<0.05). Both ligaments common to the stomatognathic system and middle ear were present in all specimens. Conclusions: There was an anatomical and functional relationship between human TMJ and the middle ear.

Los ligamentos disco-maleolar y maleolar anterior son comunes en el oído medio, la articulación temporomandibular y la mandíbula, todas ellos comparten un origen embriológico común. Los aspectos morfométricos y funcionales de estos ligamentos fueron estudiados en 23 huesos temporales. Diseño experimental: el techo del epitímpano y el techo de la articulación temporomandibular fue elevada mediante micro-disección de la fosa craneal media, exponiendo ambos ligamentos disco-maleolar y maleolar anterior y su asociación con el maleus, el disco de la articulación temporomandibular y língula mandibular. Principales observaciones: Ambos ligamentos comienzan en el maleus y toman una ruta anterior y divergente hacia la articulación temporomandibular y língula, pasando a través del canal de Huguier. Las longitudes medias del ligamento disco-maleolar y maleolar anterior fueron 6,88 mm (DS 0,81) y 4,2mm (DS 1,17), respectivamente, no fueron reveladas diferencias estadísticamente significativas entre las partes. La tracción del disco de la articulación temporomandibular fue aplicada para verificar la movilidad del maleus; el movimiento del maleus fue observado cuando se aplicó tracción del ligamento disco-maleolar en el 30,5% de las muestras. Se observó correlación entre el movimiento del maleus y la longitud disco-maleolar (R2 = -0,499, p <0,05). Ambos ligamentos comunes al sistema estomatognático y el oído medio estaban presentes en todos los especímenes. Conclusiones: Existe una relación anatómica y funcional entre la ATM humana y el oído medio.

Evaluation of temporomandibular joint in stress-free patients.

OBJECTIVES: The aetiology of temporomandibular disorders (TMD) is presently considered to be multifactorial, and stress has been regarded as an important factor in their onset. Many studies have evaluated the importance of stress in TMD; however, only patients with TMD and stress have been assessed. This study aimed at evaluating signs and symptoms of TMD in stress-free patients. METHODS: The temporomandibular joints (TMJs) of 40 stress-free patients were evaluated during clinical examination and in MRI. RESULTS: The individuals lived in an area without electric power supply or telephone services. They worked in agriculture and fishery. 77.5% of the patients presented normal mandibular function; 70% presented normal mandibular trajectory; 61.25% did not present sounds in TMJ and 93.75% did not present joint pain during palpation. Image screening showed that 70% of TMJ presented normal disc position. Only one patient (1.25%) presented TMD. CONCLUSIONS: The absence of stress is a strong factor for the non-development of TMD.