TMJ Biomechanics and Functions

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Questions and Answers

What is the primary movement occurring during lateral excursion of the mandible?

  • Protrusion of the mandibular condyle and disc
  • Elevation of the mandible
  • Side to side translation of the condyle and disc within the fossa (correct)
  • Rotational movement of the condyle and disc

What occurs during the early phase of depression of the mandible?

  • The disc moves in the opposite direction of the condyle
  • The condyle rolls posteriorly within the concave inferior surface of the disc (correct)
  • The condyle rolls anteriorly within the concave inferior surface of the disc
  • The body of the mandible moves superiorly and posteriorly

What is the consequence of abnormal function in one TMJ?

  • It has no effect on the other TMJ
  • It leads to protrusion of the mandible
  • It naturally interferes with the function of the other TMJ (correct)
  • It causes the mandible to move only in a rotational manner

What occurs during retrusion of the mandible?

<p>The mandibular condyle and disc translate posteriorly and slightly upwards (C)</p>
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What is the maximum amount of mouth opening that occurs during depression of the mandible?

<p>During yawning or singing (C)</p>
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What is the movement of the mandible during the late phase of depression?

<p>Primary translation of the mandible relative to the temporal (B)</p>
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What guides the movement of the mandible during lateral excursion?

<p>The mandibular fossa and articular disc (B)</p>
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What is the action used to grind food during mastication?

<p>Elevation of the mandible (B)</p>
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What is the result of bilateral action of the TMJs during movement of the mandible?

<p>The movement of the mandible is coordinated and normal (C)</p>
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During which phase of depression does the body of the mandible move inferiorly and posteriorly?

<p>Early phase (B)</p>
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What happens to the condyle and disc during translation?

<p>They slide together in a forward and inferior direction. (A)</p>
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What is the result of bilateral contraction of the masseter muscle?

<p>The mandible is elevated and brought into contact with the maxilla. (D)</p>
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What is the effect of unilateral contraction of the temporalis muscle?

<p>Ipsilateral excursion of the mandible. (D)</p>
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What is the result of bilateral contraction of the medial pterygoid muscle?

<p>Mandible elevation and slight protrusion. (D)</p>
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What is the effect of unilateral contraction of the lateral pterygoid muscle?

<p>Mandible depression. (B)</p>
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What is the main function of the secondary muscles of mastication?

<p>Mandible depression. (D)</p>
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What is the special role of the superior head of the lateral pterygoid muscle?

<p>Adjusting disc position. (C)</p>
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What happens to the axis of rotation at the end of opening?

<p>It shifts inferiorly. (D)</p>
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What is the result of bilateral contraction of the temporalis muscle?

<p>Mandible elevation and slight retrusion. (C)</p>
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What is the effect of bilateral contraction of the lateral pterygoid muscle?

<p>Strong protrusion of the mandible. (B)</p>
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What is the primary function of the TMJ?

<p>To facilitate mastication, talking, and swallowing (C)</p>
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What type of joint is the TMJ?

<p>Synovial joint (A)</p>
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What is the function of the articular disk in the TMJ?

<p>To generate greater congruency and reduce contact pressure (B)</p>
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What is the main component of the passive stability of the TMJ?

<p>Fibrous capsule (B)</p>
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What is the movement of the mandible during protrusion?

<p>Anterior movement without significant rotation (A)</p>
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What is the function of the medial pole of the mandibular condyle?

<p>It is a prominent structure that provides a surface for articulation (A)</p>
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What is the characteristic of the articular disk of the TMJ?

<p>It is a dense fibrocartilage that lacks blood supply and sensory innervation (B)</p>
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What is the function of the lateral temporomandibular ligament?

<p>To provide stability to the joint during lateral movements (A)</p>
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What is the movement of the mandible during depression?

<p>Downward movement of the mandible (D)</p>
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What is the characteristic of the retrodiscal tissue?

<p>It contains collagen and elastic tissue (A)</p>
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Flashcards

What is the TMJ?

A bicondylar synovial joint connecting the lower jaw condyle to the temporal bone's mandibular fossa.

What are the main functions of the TMJ?

Mastication (chewing), talking, and swallowing, all performed bilaterally with tongue and teeth coordination.

What does the mastication process involve?

The TMJ, tongue, and teeth working together to break down food.

What are the arthrologic features of the TMJ?

Permits wide range of rotation and translation, cushioned by an articular disk.

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What is the function of the articular disk?

Divides the joint into superior and inferior cavities.

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What is the shape of the mandibular condyle?

Convex shape with medial and lateral poles, covered by fibrocartilage.

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What is the articular disc made of?

Dense fibrocartilage that lacks blood supply and sensory innervation.

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What provides passive stability to the TMJ?

Fibrous capsule, articular disk, lateral temporomandibular ligament, and retrodiscal tissue.

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What provides active stability to the TMJ?

Muscles surrounding the joint.

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What are the four main movements of the TMJ?

Protrusion-retrusion, lateral excursion, depression-elevation.

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What do protrusion and retrusion involve?

Anterior and posterior movements of the mandible without significant rotation.

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What does lateral excursion involve?

Side-to-side movement of the mandible, guided by the mandibular fossa and articular disk.

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What do depression and elevation involve?

Opening and closing the mouth, respectively.

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What happens to the articular disk during TMJ Arthrokinematics?

The articular disk translates in the direction of the condyle.

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What happens during protrusion and retrusion arthrokinematically?

Anterior and posterior translation of the condyle and disk, respectively.

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What happens during lateral excursion arthrokinematically?

Side-to-side translation of the condyle and disk.

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What happens during depression and elevation arthrokinematically?

Rotation and translation of the condyle and disk.

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What muscles are responsible for TMJ movement?

Masseter, temporalis, medial pterygoid, and lateral pterygoid.

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How do the TMJ muscles function?

Each muscle has a specific function in bilateral and unilateral contraction, affecting mandible movement and disc position.

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Study Notes

TMJ Biomechanics

  • The TMJ (Temporomandibular Joint) is a bicondylar synovial joint between the condyle in the lower jaw and the mandibular fossa of the temporal bone.

Function

  • The TMJ's main functions include mastication, talking, and swallowing, working in bilateral action with the tongue and teeth.

Mastication Process

  • The mastication process involves the TMJ, tongue, and teeth working together to break down food.

Arthrology of the TMJ

  • The TMJ is a synovial joint that permits a wide range of rotation and translation, with an articular disk cushioning the forces related to mastication.
  • The articular disk separates the joint into two synovial joint cavities: the inferior joint cavity and the superior joint cavity.

Anatomy of the TMJ

  • The mandibular condyle has a convex shape with medial and lateral poles, covered by a thin layer of fibrocartilage.
  • The articular disk is made of dense fibrocartilage, lacks blood supply and sensory innervation, and helps to generate greater congruency within the TMJ.

Stability of the TMJ

  • Passive stability is provided by the fibrous capsule, articular disk, lateral temporomandibular ligament, and retrodiscal tissue.
  • Active stability is provided by muscles.

Osteokinematics of the TMJ

  • The TMJ has four main movements: protrusion-retrusion, lateral excursion, depression-elevation.
  • Protrusion and retrusion involve anterior and posterior movements of the mandible without significant rotation.
  • Lateral excursion involves side-to-side movement of the mandible, guided by the mandibular fossa and articular disk.
  • Depression and elevation involve opening and closing the mouth, respectively.

TMJ Arthrokinematics

  • The TMJ's arthrokinematics involve the movement of the mandible, with the articular disk translating in the direction of the condyle.
  • Protrusion and retrusion involve anterior and posterior translation of the condyle and disk, respectively.
  • Lateral excursion involves side-to-side translation of the condyle and disk.
  • Depression and elevation involve rotation and translation of the condyle and disk.

Kinetics of the TMJ

  • The muscles responsible for TMJ movement include the masseter, temporalis, medial pterygoid, and lateral pterygoid.
  • Each muscle has a specific function in bilateral and unilateral contraction, affecting mandible movement and disc position.

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