Podcast
Questions and Answers
What is the primary movement occurring during lateral excursion of the mandible?
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?
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?
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?
What occurs during retrusion of the mandible?
What is the maximum amount of mouth opening that occurs during depression of the mandible?
What is the maximum amount of mouth opening that occurs during depression of the mandible?
What is the movement of the mandible during the late phase of depression?
What is the movement of the mandible during the late phase of depression?
What guides the movement of the mandible during lateral excursion?
What guides the movement of the mandible during lateral excursion?
What is the action used to grind food during mastication?
What is the action used to grind food during mastication?
What is the result of bilateral action of the TMJs during movement of the mandible?
What is the result of bilateral action of the TMJs during movement of the mandible?
During which phase of depression does the body of the mandible move inferiorly and posteriorly?
During which phase of depression does the body of the mandible move inferiorly and posteriorly?
What happens to the condyle and disc during translation?
What happens to the condyle and disc during translation?
What is the result of bilateral contraction of the masseter muscle?
What is the result of bilateral contraction of the masseter muscle?
What is the effect of unilateral contraction of the temporalis muscle?
What is the effect of unilateral contraction of the temporalis muscle?
What is the result of bilateral contraction of the medial pterygoid muscle?
What is the result of bilateral contraction of the medial pterygoid muscle?
What is the effect of unilateral contraction of the lateral pterygoid muscle?
What is the effect of unilateral contraction of the lateral pterygoid muscle?
What is the main function of the secondary muscles of mastication?
What is the main function of the secondary muscles of mastication?
What is the special role of the superior head of the lateral pterygoid muscle?
What is the special role of the superior head of the lateral pterygoid muscle?
What happens to the axis of rotation at the end of opening?
What happens to the axis of rotation at the end of opening?
What is the result of bilateral contraction of the temporalis muscle?
What is the result of bilateral contraction of the temporalis muscle?
What is the effect of bilateral contraction of the lateral pterygoid muscle?
What is the effect of bilateral contraction of the lateral pterygoid muscle?
What is the primary function of the TMJ?
What is the primary function of the TMJ?
What type of joint is the TMJ?
What type of joint is the TMJ?
What is the function of the articular disk in the TMJ?
What is the function of the articular disk in the TMJ?
What is the main component of the passive stability of the TMJ?
What is the main component of the passive stability of the TMJ?
What is the movement of the mandible during protrusion?
What is the movement of the mandible during protrusion?
What is the function of the medial pole of the mandibular condyle?
What is the function of the medial pole of the mandibular condyle?
What is the characteristic of the articular disk of the TMJ?
What is the characteristic of the articular disk of the TMJ?
What is the function of the lateral temporomandibular ligament?
What is the function of the lateral temporomandibular ligament?
What is the movement of the mandible during depression?
What is the movement of the mandible during depression?
What is the characteristic of the retrodiscal tissue?
What is the characteristic of the retrodiscal tissue?
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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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