Temporomandibular joint under the influence of stress

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There are two major macromolecular components of the extracellular matrix・・・・・・glycosaminoglycans (GAG) and collagen. GAG is responsible for the elastic property in the formation of the proteoglycan aggregates, whereas collagen makes the tissue hard through its maturity. Although the stiffness relates with the extracellular matrix in the connective tissue, there have been few reports on their relations of the temporomandibular joint with stress.We investigated of GAG and collagen immunohistochemicaly and biochemichaly about stressed rat.There are slight decrease of GAG and collagen after stress. GAG makes a contribution to elasticity due to the formation of the proteoglycan aggregate and virtue of their highly anionic charge. On the other hand, collagen makes the tissue hard by its maturity and cross link. For the reasons stated above, the stiffness of condyles changed as a consequence of movement of GAG and collagen. Next, from the viewpoint of structure of condylar cartilage, the molecular composition and structural arrangement of the matrix components reflect the external biomechanical forces functionally exerted on them. The dense type I collagen bundles covering the condyle prevent to tear the cartilage. In the hyaline cartilage, type II collagen arranged on three dimensions contributes to strenght, and chondoroitin sulfate and keratan sulfate kept lots of water provide the cartilage with elasticity. Since the condylar cartilage is located in areas that are subjected to multidirectional large stress, it followed that coexistence of these matrix is necessary to withstand such biomechanical demands.