Objective: The complex movement of the temporomandibular joint (TMJ) disc during mastication is controlled in large part by the disc's attachments to the surrounding tissues. This study seeks to address the lack of available quantitative data characterizing the extracellular matrix composition of the discal attachments and how these properties compare to the disc.
Design: Porcine TMJ disc-attachment complexes were carefully dissected into six discal attachments and five TMJ disc regions. All samples were assayed biochemically for total collagen, glycosaminoglycan (GAG), DNA, and hydration. Additionally, histology was performed on the whole joint to investigate the anatomy of the disc-attachment complex, and to verify the regional distribution of matrix components.
Results: Quantitative biochemical assays showed that overall water content was fairly constant in all disc and attachment regions. Disc regions generally showed higher sulfated GAG and collagen content than the attachments. In contrast, the attachments contained greater DNA content than the disc. Histological staining supported the quantitative results and also indicated more elastic fibres to be present in the attachments than the disc.
Conclusions: Although macroscopically the TMJ disc and its attachments form a seamless complex within the joint, a closer look at regional biochemical constituents reveals that these two components are distinct. Whilst the disc and attachments both contain the same major constituents, the relative amounts of these components vary based on the functional requirements of the tissue. These results can further understanding of both TMJ biology and pathology.
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