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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:
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 ...
Lateral movements – Medial and lateral pterygoid (the ipsilateral temporalis and the pterygoid muscles of the contralateral side pull the mandible to the ipsilateral side). [36] Each lateral pterygoid muscle is composed of 2 heads, the upper or superior head and the lower or inferior head.
In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: symphysis menti) or line of junction where the two lateral halves of the mandible typically fuse in the first year of life (6–9 months after birth). [1]
The temporomandibular ligament, also known as the external lateral ligament, is a ligament that connects the lower articular tubercle of the zygomatic arch to the lateral and posterior border of the neck of the mandible. It prevents posterior displacement of the mandible.
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 ...
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.
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).