• The orbicularis oris functions to close and shut the mouth and formes the most versatile types of grimaces.

Physical Examination Of Muscles Of Mastication


  • The patient is asked to clench their teeth and, using both hands, the practitioner palpates the masseter muscles on both sides, making sure that the patient continues to clench during the procedure.
  • Palpate the origin of the masseter along the zygomatic arch and continue to palpate down the body of the mandible where the masseter is attached.
  • The masseter is most often tender along the central fibers of at its insertion.
  • Masseter hypertonicity is found in patients who have premature contacts on the nonworking side.
  • Parafunctions such as bruxism and clenching also give rise to masseter pain that is frequently associated with pain in the temporalis muscle.


  • The temporalis is palpated in much the same manner

to detect lateral interferences.


  •  In patients with nonworking side interferences, the lateral pterygoid muscle on the opposite of the interference is sometimes painful.
  • In addition, this muscle will be painful whenever there is a centric slide with an anterior component and the patient is bruxing or clenching in this anterior position.
  • The lateral pterygoid, despite its commonality in displaying a spasm, cannot be palpated intraorally.


  • The medial pterygoid muscle is not usually involved in gnathic dysfunctions but when they are hypertonic, the patient is usually conscious of a feeling of fullness in the throat and an occasionally pain on swallowing.
  • Muscles and Malocclusion
  • Article published by T.M.Graber. in 1963 June in AJODO.
  • This study attempts  to balance orthodontic therapy and musculature philosophically
  • Orthodontist can balance them physically with appliances.
  • It deals with the role of muscles in the etiology and correction of malocclusion.
  • Muscles function is normal.
  • The teeth are in state of balance with environmental force.
  • The open bite problem may arise because of thumb and finger sucking, that gives an excellent example of applied muscles physiology.
  • With changes in tongue ,cheek, and lip muscle function, the net effect is narrowing of the maxillary arch and over eruption of post teeth.


  • Abnormal muscle activity.
  • A change in muscle function is a requisite expansion is a treatment objective.
  • In hereditary type of class II malocclusion the teeth merely reflect the abnormal antero-posterior jaw relationship, and the excessive over jet is consequence.
  • If structural mal-relationship exists, the muscle function adapt to this pattern as best it can in line with the requirement of mastication, deglutition and speech.
  • The lip may become hypertrophic as a result.
  • The lower incisors buckle as the mandibular segment is flattened by continuously abnormal mentalis muscle activity.
  • The curve of spee increases, buccinator muscle activity.
  • Openbite also occurs in this abnormal muscle activity can cause the pseudo class II div I.
  • t/t for this should creation of normal basal bone relationship that permit muscle function properly and expansion with appliance.


  • The role of musculature is more difficult to establish.
  • Activity of the cheek and lip muscles is usually normal but curve of spee is excessive that interferes with the eruption of post teeth.
  • Because of this TMJ problems arise like clicking, and pain.