Head of mandible

Location and anatomical landmarks

The head of the mandible (Caput mandibulae) is located at the superior end of the ramus of the mandible (Ramus mandibulae).

• Condylar process (Processus condylaris) is a bony structure terminating in the head.
• Neck of mandible (Collum mandibulae) is a part of the condylar process. On its medial surface lies the pterygoid fovea (Fovea pterygoidea).
• Mandibular notch (Incisura mandibulae) is a depression separating the condylar process with the head from the coronoid process (Processus coronoideus).

Participation in the temporomandibular joint (TMJ)

The head participates in the formation of the joint together with the mandibular fossa (Fossa mandibularis) of the temporal bone.

• Incongruence: The dimensions of the head and the articular fossa do not match. This creates instability in the intra-articular relationships, which is why joint stabilization depends entirely on dental occlusion and the tone or state of the masticatory muscles.
• Articular disc (Discus articularis): a biconcave plate of dense fibrous tissue that eliminates the mismatch of the articular surfaces. The inferior surface of the disc replicates the shape of the mandibular head.
• Bilaminar zone: a connective tissue structure connecting the posterior part of the articular facet of the head with the posterior part of the fossa.

Movements in the lower compartment of the joint cavity occur between the inferior surface of the disc and the head. The volume of synovial fluid in the lower compartment in adults is 0.5–0.8 ml.

Biomechanics of movements

The TMJ is a paired joint, therefore movements of the heads on both sides of the mandible are strictly simultaneous.

• Mouth opening: the process is divided into three phases. In the first phase, the head rotates around the frontal axis in the lower compartment of the joint. In the second phase, together with the articular disc, it glides forward and downward along the posterior slope of the articular tubercle, displacing anteriorly by approximately 12 mm, in some cases up to 2 cm. In the third phase, at maximum mouth opening, movement occurs exclusively in the lower compartment of the joint around the frontal axis; the articular disc rests on the articular tubercle.
• Lateral excursion: movements are asymmetric. On the working side, the head rotates around a vertical axis passing through the neck of the condylar process and moves backward and medially. On the balancing side, the head along with the disc glides downward, forward, and medially, reaching the crest of the articular tubercle.

Clinical significance: dislocations and displacements

• Anterior dislocation: with excessive mouth opening, the head may slip anteriorly beyond the articular tubercle into the infratemporal fossa. Conservative methods, including the Hippocrates, Blechman, Gershuni, and Popescu methods, or surgical intervention (traction on the mandibular notch downward with simultaneous posterior pressure on the chin) are used for reduction.
• Posterior dislocation: occurs from a blow to the chin from front to back with the mouth open. The head is displaced posteriorly and becomes fixed between the articular fossa and the mastoid process.
• Subluxation of the articular disc: at maximum mouth opening, the head of the mandible does not exit the mandibular fossa. Anterior displacement of the disc occurs with subsequent reduction, accompanied by a characteristic click.

Class and exam questions

What else to study on this topic

• Temporomandibular joint (Articulatio temporomandibularis)
• Articular disc (Discus articularis)
• Condylar process (Processus condylaris)
• Mandibular fossa (Fossa mandibularis)

Other topics in the "Anatomical Structures" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.