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A double chin is a loss of definition of the jawbone or soft tissue under the chin. There are two possible causes for a double chin, which have to be differentiated. In overweight people, commonly the layer of subcutaneous fat around the neck sags down and creates a wrinkle , creating the appearance of a second chin.
Changes to the dental morphology and jaw are major elements of hominid evolution. These changes were driven by the types and processing of food eaten. The evolution of the jaw is thought to have facilitated encephalization, speech, and the formation of the uniquely human chin.
The necessity of translation to produce further opening past that which can be accomplished with a sole rotation of the condyle can be demonstrated by placing a resistant fist against the chin and trying to open the mouth more than 20 or so mm. The resting position of the temporomandibular joint is not with the teeth biting together.
The size and shape of the bones making up this structure are responsible for the size and shape of a person's chin. Synonyms of mental protuberance include mental process and protuberantia mentalis. Mental in this sense derives from Latin mentum (chin), not mens (mind), source of the more common meaning of mental.
The angle of the mandible (a.k.a. gonial angle, Masseteric Tuberosity, and Masseteric Insertion) is located at the posterior border at the junction of the lower border of the ramus of the mandible.
The mentalis muscle causes a weak upward-inward movement of the soft tissue complex of the chin. [2] This raises the central portion of the lower lip. [2] In the setting of lip incompetence (the upper and lower lips not touching each other at rest), the contraction of the mentalis muscle can bring temporary but strained oral competence.
The mental nerve can be blocked with local anesthesia.This can be used in surgery of the chin, the lower lip, and the buccal mucosa from midline to the second premolar.In animals, it can be used in surgery of the lower lip, [2] and lower teeth anterior to the site of administration. [3]
Growth of mandible depends on the normally developing condyles and the muscle function For example, trauma or infection that affect mastoid, middle ear or the joint will result in ankylosis of temporomandibular joint leading to mandibular micrognathia. [31] Macronagthia; Macronagthia is a condition of abnormally large jaws.