The disc is thick all around its rim, and thin in the centre. From anterior to posterior it shows – anterior extension, thick anterior band (2.0mm thick), intermediate thin zone (1.0 mm thick), thick posterior band (3.0 mm thick) and posterior most bilaminar region (Dubrul, 1996; Williams et al, 1999). The disc is attached all around the joint capsule except the strong straps those fix the disc directly to the medial and lateral condylar poles which ensures that the disc and condyle move together in protraction and retraction (Choukas and Sicher, 1960; Williams et al, 1999). The anterior extension of the disc is attached to fibrous capsule superiorly and inferiorly and through that to temporal bone and the mandibular neck respectively. In between it gives insertion to lateral pterygoid muscle where the fibrous capsule is lacking and synovial membrane is supported only by loose areolar tissue. In the opinion of Kreutziger and Mahan (1975), this deficiency anteriorly is the weak point since there is no fibrous resistance to hypertranslation. Apart from lateral pterygoid, anteromedially, there are attached some fibres of masseter and temporalis laterally. Although more than one muscle is inserted into the disc, majority of the interest has been focussed on lateral pterygoid, whose deep position, unfortunately makes it difficult to investigate under natural conditions (Moore). Continue reading
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Anatomy of temporomandibular joint Part 2
Articular coverings :
The smooth slippery, pressure bearing tissue carpeting, the surfaces of the bones varies in thickness across different articular areas. It is essentially a bed of tough collagen fibres bound by special glycoproteins. On the condyle, the tissue is thickest in anteroposterior direction and thickness is greater medially (average measurements 0.37 mm laterally and 0.48 mm medially). On temporal component, it is thickest along articular eminence and preglenoid plane. The thickness is less medially (0.49 mm and 0.36 mm for eminence and plane respectively laterally and 0.45 mm and 0.34 mm medially). In the depth of the mandibular fossa the thickness of periosteum is merely 0.07 mm. Continue reading