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There are two lateral excursions (left and right) and the forward excursion, known as protrusion. The reversal of protrusion is retrusion. When the mandible is moved into protrusion, the mandibular incisors , or front teeth of the mandible, are moved so that they first come edge to edge with the maxillary (upper) incisors and then surpass them ...
It is the condyles within the fossa and the associated muscles and ligaments together with its neuromuscular link that determines mandibular movements. Lateral, protrusive and repressive excursions of the mandible are guided by the posterior system. Lateral excursions. It is important to define the movement of the condyles in lateral excursions:
A concerted effort of the lateral pterygoid muscles helps in lowering the mandible and opening the jaw. Unilateral action of a lateral pterygoid muscle causes contralateral excursion (a form of mastication), usually performed in concert with the medial pterygoids. [citation needed] When they work independently, they can move the mandible side ...
Each lateral pterygoid muscle is composed of 2 heads, the upper or superior head and the lower or inferior head. The lower head originates from the lateral surface of the lateral pterygoid plate and inserts at a depression on the neck of mandibular condyle, just below the articular surface, termed the pterygoid fovea.
The four classical muscles of mastication elevate the mandible (closing the jaw) and move it forward/backward and laterally, facilitating biting and chewing. Other muscles are responsible for opening the jaw, namely the geniohyoid, mylohyoid, and digastric muscles (the lateral pterygoid may play a role).
The temporomandibular ligament constrains the mandible as it opens, keeping the condyloid process close to the joint. [2] It prevents posterior displacement of the mandible. It also prevents the condyloid process from being driven upward by a blow to the jaw, which would otherwise fracture the base of the skull.
The pterygomandibular space lies between the lateral surface of medial pterygoid and the medial surface of the mandibular ramus. The four compartents of the right masticator space. A Temporalis muscle, B Masseter muscle, C Lateral pterygoid muscle, D Medial ptaerygoid muscle, E Superficial temporal space, F Deep temporal space, G Submasseteric ...
The principal movements reproduced are: at rest (centric jaw relation), in protrusion (to bite), from side to side (lateral excursion) to chew, in retrusion, and any possible combination of these. Counter-intuitively, it is the cast of the maxilla which moves relative to the cast of the mandible and the articulator.