Observations on arthrodial types of temporomandibular joints

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V ARIOUS OPINIONS ARE HELD by different investigators as to the functional importance of the anatomic structures which take part in limiting retrusion of the mandible. Arstadl points out that in other joints, of the digits for example, limitation of motion is due to the joint capsule and re-enforcing ligaments. In the temporomandibular joint, the capsule is slack and flaccid, so much so that it is not injured when the joint is dislocated. The sphenomandibular and stylomandibular ligaments, by their position, cannot prevent the condyles from sliding dorsally. In 1933,2 Arstad maintained that the anterior part of the joint capsule supports the retruded position. In 1954,l however, he described some collateral capsular ligaments as being responsible for limited retrusion of the condyles. Steinhardt3 reported in 1934 that the external pterygoid muscle limits retrusion of the condyles. In 1957, however, Steinhardt4 agreed with Arstadl that the collateral capsular ligaments of the temporomandibular joint are responsible. He also said that the muscles are important but did not elaborate. Siche+a stated that one function of the external pterygoid muscle is to hold the condyle and disc against the posterior slope of the articular eminence while the teeth are in contact, Markowitz and Gerry? and other investigators state that the function of the external pterygoid muscles acting together is to cause protrusion of the mandible. The role muscles play in limiting retrusion of the condyles was contradicted by the work of Aprile and Sai.zar3 when they obtained symphyseal angle tracings from specimens with the joints intact but with the muscles removed. The work of PosseltQ also nullified the theory that muscles are the effecters which limit posterior retrusion of the condyles. Posselt obtained Gothic arch (stylus) tracings from anesthetized living persons under the influence of curare. Ferrein,lO Breuer,ll and ReeC reported that the retruded position of the condyles is held by the temporomandibular ligament. Kirk13 was of the opinion that the denture bears the main stress of mastication and prevents the backward thrust of the condyles. Robinson14 reported that the mandibular condyle in its most retruded position is not normally situated at the bottom of the mandibular fossa but is closer to the posterior part of the tuberculum articulare.