Oral Surgery Lecture 13: TMJ Overview

Oral Surgery - Lecture 13: TMJ (1)

• The temporomandibular joint (TMJ) is the most active and frequently used joint in the body.

• It moves up to 2000 times a day during talking, chewing, swallowing, and snoring.

• A joint is an articulation between two bones. A true joint has movement between the bones, while a false joint does not.

• The TMJ has three basic components:

  • Temporal bone of the skull
  • Mandible (lower jaw)
  • The structure connecting the two

• The TMJ is a bilateral ginglymo-diarthrodial synovial joint.

  • Bilateral means it exists on both sides and is connected.
  • Ginglymus means the joint allows movement back and forth in one plane (hinge or rotational).
  • Diarthrodial means the joint permits gliding or translation motion of surfaces.

TMJ Anatomy & Physiology

• The TMJ has articular surfaces, a joint capsule, a disc (meniscus), and synovial membranes.
• The skeletal components of the masticatory system include the maxilla, mandible, and temporal bones. These support the teeth and articulate with each other.
• The articular surfaces are covered with fibrocartilage.
• The TMJ is a synovial joint containing synovial fluid. This fluid lubricates and nourishes the joint. Its volume is approximately 1 cubic centimeter.

Articular Surfaces (detailed)

• The articulation involves the mandibular condyle and the glenoid fossa of the temporal bone.
• The condyle is horseshoe-shaped and articulates with the temporal bone.
• The glenoid fossa is part of the temporal bone's squamous portion, where the condyle articulates.

Joint Capsule

• The joint capsule encompasses and protects the TMJ.
• Attachments include the articular eminence, the glenoid fossa, the condylar neck, the lateral and medial pterygoid muscle, and the retrodiscal tissue. The retrodiscal tissue is found posteriorly to the disc, and consists of 2 layers- the superior and inferior laminae.
• Ligaments in the TMJ complex stabilize the condyle and disc during movement.

Articular Disc (Meniscus)

• The articular disc is a biconcave shaped structure that separates the condyle from the mandibular fossa.
• It divides the synovial cavity into two compartments (superior and inferior).

Vascular and Nerve Supply

• The TMJ receives its blood supply primarily from branches of the external carotid artery, including the superficial temporal and maxillary arteries.
• The TMJ receives its nerve supply from the auriculotemporal nerve and branches from the posterior division of the mandibular nerve, along with deep temporal and masseteric nerves from the anterior division.

Normal TMJ Function

• The mouth opening involves rotation and translation (gliding) movements.
• Rotation occurs around a horizontal axis through the condylar heads (20-25mm opening).
• Translation involves the condyle and meniscus moving downward and forward beneath the articular eminence (40-60mm opening).

Muscles of Mastication

• Four paired muscles (masseter, temporalis, medial pterygoid, and lateral pterygoid) work in coordination to move the mandible during chewing.
• These muscles work in coordination with ligaments and accessory muscles to enable efficient mastication.
• Problems when these muscles do not function correctly can lead to deviations in movement.

Questions

These questions cover different aspects as listed on the notes' document.