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Questions and Answers
What is the primary function of the articular disc in the TMJ?
What is the primary function of the articular disc in the TMJ?
What is the shape of the mandibular condyle?
What is the shape of the mandibular condyle?
What is the characteristic of the articular disc in terms of blood supply and sensory innervation?
What is the characteristic of the articular disc in terms of blood supply and sensory innervation?
What is the purpose of the symbiotic movement in the TMJ?
What is the purpose of the symbiotic movement in the TMJ?
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What are the two synovial joint cavities in the TMJ?
What are the two synovial joint cavities in the TMJ?
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What is the function of the mandibular fossa?
What is the function of the mandibular fossa?
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What is the characteristic of the mandibular condyle?
What is the characteristic of the mandibular condyle?
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What is the purpose of the articular disc in the TMJ?
What is the purpose of the articular disc in the TMJ?
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What is the type of joint that the TMJ is classified as?
What is the type of joint that the TMJ is classified as?
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What is the importance of synchrony and synergy in the TMJ?
What is the importance of synchrony and synergy in the TMJ?
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What is the primary function of the articular disc in the TMJ?
What is the primary function of the articular disc in the TMJ?
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What type of fibers are found in the retrodiscal tissue?
What type of fibers are found in the retrodiscal tissue?
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What movement of the TMJ is essential for maximum opening of the mouth?
What movement of the TMJ is essential for maximum opening of the mouth?
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What structure provides lateral stability to the TMJ capsule?
What structure provides lateral stability to the TMJ capsule?
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What is the average normal translation of the mandible during lateral excursion?
What is the average normal translation of the mandible during lateral excursion?
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What type of stability is provided by the musculature of the TMJ?
What type of stability is provided by the musculature of the TMJ?
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What is the movement of the TMJ that involves side-to-side translation of the mandible?
What is the movement of the TMJ that involves side-to-side translation of the mandible?
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What is the opposite movement of protrusion in the TMJ?
What is the opposite movement of protrusion in the TMJ?
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What structure guides the line of movement during lateral excursion?
What structure guides the line of movement during lateral excursion?
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What is the primary function of the fibrous capsule in the TMJ?
What is the primary function of the fibrous capsule in the TMJ?
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What is the average maximum opening of the mouth during yawning or singing?
What is the average maximum opening of the mouth during yawning or singing?
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During mastication, how much of the maximum opening is required?
During mastication, how much of the maximum opening is required?
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What is the primary movement of the mandible during elevation?
What is the primary movement of the mandible during elevation?
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What is the effect of abnormal function in one TMJ on the other?
What is the effect of abnormal function in one TMJ on the other?
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During rotational movement, what is the action of the mandibular condyle relative to the inferior surface of the disc?
During rotational movement, what is the action of the mandibular condyle relative to the inferior surface of the disc?
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What is the direction of movement of the disc during protrusion?
What is the direction of movement of the disc during protrusion?
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What is the primary movement of the condyle and disc during lateral excursion?
What is the primary movement of the condyle and disc during lateral excursion?
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What is unique about the movement of the TMJ during depression and elevation?
What is unique about the movement of the TMJ during depression and elevation?
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Why is the TMJ unique in terms of movement?
Why is the TMJ unique in terms of movement?
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What happens to the axis during TMJ movement?
What happens to the axis during TMJ movement?
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What percentage of the range of motion (ROM) is primarily characterized by rotation of the mandible relative to the temporal?
What percentage of the range of motion (ROM) is primarily characterized by rotation of the mandible relative to the temporal?
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What is the direction of the condyle's roll during the early phase of opening the mouth?
What is the direction of the condyle's roll during the early phase of opening the mouth?
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What is the result of the rolling motion of the condyle during the early phase of opening the mouth?
What is the result of the rolling motion of the condyle during the early phase of opening the mouth?
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During the late phase of opening the mouth, what is the primary movement of the condyle and disc?
During the late phase of opening the mouth, what is the primary movement of the condyle and disc?
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What is the direction of the condyle and disc sliding during the late phase of opening the mouth?
What is the direction of the condyle and disc sliding during the late phase of opening the mouth?
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What is the result of bilateral contraction of the masseter muscle?
What is the result of bilateral contraction of the masseter muscle?
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What is the result of unilateral contraction of the temporalis muscle?
What is the result of unilateral contraction of the temporalis muscle?
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What is the function of the medial pterygoid muscle?
What is the function of the medial pterygoid muscle?
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What is the shift of the axis of rotation during the late phase of opening the mouth?
What is the shift of the axis of rotation during the late phase of opening the mouth?
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What is the location of the axis of rotation during the late phase of opening the mouth?
What is the location of the axis of rotation during the late phase of opening the mouth?
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Study Notes
TMJ Biomechanics
- The Temporomandibular Joint (TMJ) is a bilateral action joint that is one of the most continuously used joints in the body.
- It is responsible for mastication, talking, and swallowing, and requires synchrony and synergy for correct jaw function.
Anatomy of the TMJ
- The TMJ is a bicondylar synovial joint between the condyle of the lower jaw (mandible) and the mandibular fossa of the temporal bone.
- The joint has a wide range of rotation and translation, and is cushioned by an articular disc that separates the joint into two synovial joint cavities.
- The inferior joint cavity is between the inferior aspect of the disc and the mandibular condyle.
- The larger superior joint cavity is between the superior surface of the disc and the segment of bone formed by the mandibular fossa.
Mandibular Condyle
- The mandibular condyle has a convex shape and possesses short projections known as medial and lateral poles.
- The medial pole is more prominent than the lateral pole.
- The condyle is covered by a thin layer of fibrocartilage.
Mandibular Fossa
- The mandibular fossa is a segment of bone formed by the temporal bone.
Articular Disc
- The articular disc is a dense fibrocartilage that lacks blood supply and sensory innervation (except the periphery).
- The disc's main function is to generate greater congruence and reduce contact pressure.
- The disc's thickness varies between its anterior and posterior regions.
- The disc position protects the condyle as it slides forward across the articular eminence during the later phase of opening the mouth.
- The disc also adds stability to the joint and helps guide the condyle of the mandible during movement.
Stability of the TMJ
- Passive stability is provided by the fibrous capsule, articular disc, lateral temporomandibular ligament, and retrodiscal tissue.
- Active stability is provided by the musculature.
Osteokinematics of the TMJ
- The TMJ has three main movements: protrusion-retrusion, lateral excursion, and depression-elevation.
- Protrusion and retrusion involve anterior and posterior translation of the mandible without significant rotation.
- Lateral excursion involves side-to-side translation of the mandible, with an average of 11mm translation considered normal.
- Depression and elevation involve opening and closing of the mouth, with a 50mm average opening from the frontal area.
TMJ Arthrokinematics
- Movement of the mandible typically involves bilateral action of the TMJs.
- Abnormal function in one joint naturally interferes with the function of the other.
- During rotational movement, the mandibular condyle rolls relative to the inferior surface of the disc, and during translational movement, the mandibular condyle and disc slide essentially together.
- The disc usually moves in the direction of the translating condyle.
TMJ Arthrokinematics-Protrusion and Retrusion
- Protrusion involves anterior translation of the mandibular condyle and disc.
- Retrusion involves posterior translation of the mandibular condyle and disc.
TMJ Arthrokinematics-Lateral Excursion/Deviation
- Lateral excursion involves side-to-side translation of the condyle and disc within the fossa.
- Secondary rotational components occur during lateral excursion.
TMJ Arthrokinematics: Depression and Elevation
- Depression and elevation involve a combination of rotation and translation among the mandibular condyle, articular disc, and fossa.
- The early phase of opening involves primary rotation of the mandible relative to the temporal.
- The late phase of opening involves a gradual transition from primary rotation to primary translation.
Kinetics of the TMJ
- Masseeterus muscle has deep and superficial heads with similar functions.
- Bilateral contraction of the masseterus elevates the mandible and brings teeth into contact, and also protrudes the mandible slightly.
- Unilateral contraction of the masseterus causes slight ipsilateral excursion.
Kinetics of the TMJ (continued)
- Temporalis muscle has bilateral contraction that elevates the mandible and slightly retrudes it.
- Unilateral contraction of the temporalis causes slight ipsilateral excursion of the mandible.
- Medial pterygoid muscle has two heads with similar functions.
- Bilateral contraction of the medial pterygoid elevates the mandible and slightly protrudes it.
- Unilateral contraction of the medial pterygoid causes slight ipsilateral excursion of the mandible.
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Description
Learn about the Temporomandibular joint (TMJ), its bilateral action, and its importance in daily functions like mastication, talking, and swallowing. Discover the synchrony and synergy required for correct jaw function.
