Temporomandibular joint disorders I


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Oral & Maxillofacial Surgery
Fifth Year

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Temporomandibular joint disorders I

  1. 1. Temporomandibular Joint Disorders Dr. Wael M. Talaat Assistant Professor of Oral & Maxillofacial Surgery University of Dammam
  2. 2. Objectives 1) 2) To know the normal TMJ anatomy To understand the biomechanics of the joint during function
  3. 3. TMJ Synonyms     Craniomandibular articulation Diarthroidal joint Mandibular joint Synovial joint
  4. 4. Classification of Joints   Fibrous joints: the 2 bones are connected by fibrous connective tissue. Cartilagenous joints: Primary: Bones are connected by hyaline cartilage or fibrocartilage, occurring between ossification centers. This cartilage may ossify with age. Examples in humans are the "growth plates" in long bones. These joints allow for only a little movement, such as in the spine or ribs
  5. 5. Secondary: Fibrocartilaginous joints, usually occurring in the midline. Examples in human anatomy would be the intervertebral discs and the pubic symphysis.  Synovial joints: Consist of 2 bones covered by hyaline cartilage united and surrounded by a capsule (TMJ) 
  6. 6. Why is the TMJ unique     It functions bilaterally in harmony The articular disc is movable during joint movement The articular surfaces are covered by fibrocartilage and not hyaline cartilage The fibrocartilage is considered as the growth center for the mandible
  7. 7. Parts Of The Joint 1. 2. 3. 4. 5. 6. 7. Articular eminence Articular fossa Condyle Capsule Ligaments Synovial Fluid Articular disc
  8. 8. 1- Articular Eminence  A raised area located on the articulated surface of the temporal bone.
  9. 9. 2- Articular Fossa  The part of the temporal bone which mates to the upper surface of the disk is the glenoid (or mandibular) fossa.
  10. 10. 3- Condyle  The part of the mandible which mates to the under-surface of the disc. The condylar head is about 20 mm wide mediolaterally and 10 mm thick dorsoventrally.
  11. 11. 4- Capsule  The capsule is a fibrous membrane that surrounds the joint and incorporates the articular eminence.  It attaches to the articular eminence, the articular disc and the neck of the mandibular condyle.
  12. 12. 5- Ligaments  1. There are three ligaments associated with the TMJ: one major and two minor ligaments. The major ligament: The Temporomandibular Ligament, is actually the thickened lateral portion of the capsule, and it has two parts: an outer oblique portion and an inner horizontal portion.
  13. 13. 2.  The two minor ligaments: The stylomandibular ligament separates the infratemporal region (anterior) from the parotid region (posterior), and runs from the styloid process to the angle of the mandible.
  14. 14.
  15. 15.  The sphenomandibular ligament runs from the spine of the sphenoid bone to the lingula of mandible. These ligaments are important in that they define the border movements or the farthest extents of movements of the mandible. Movements of the mandible made past the extents functionally allowed by the muscular attachments will result in painful stimuli, and thus, movements past these more limited borders are rarely achieved in normal function.
  16. 16. 6- Synovial Fluid  The synovial fluid is a derivative of plasma and contains low-molecular weight molecules, including glucose, urea, uric acid and proteins. The level of these molecules varies depending on the degree of inflammation in the joint. Total protein in normal synovial fluid is approximately 1.5 to 1.8 g/dl. In the inflamed state, this level increases.
  17. 17. 7- Articular Disc  The articular disc is a fibrous extension of the capsule in between the two bones of the joint. The disc functions as articular surfaces against both the temporal bone and the condyles and divides the joint into two sections. It is biconcave in structure and attaches to the condyle medially and laterally.
  18. 18. 7- Articular Disc  The anterior portion of the disc splits in the vertical dimension, coincident with the insertion of the superior head of the lateral pterygoid. The posterior portion also splits in the vertical dimension, and the area between the split continues posteriorly and is referred to as the retrodiscal tissue.
  19. 19. 7- Articular Disc  Unlike the disc itself, this piece of connective tissue is vascular and innervated, and in some cases of anterior disc displacement, the pain felt during movement of the mandible is due to the condyle compressing this area against the articular surface of the temporal bone.
  20. 20. Innervation and vascularization  Sensory innervation of the temporomandibular joint is derived from the auriculotemporal and masseteric branches of V3 .  Its arterial blood supply is provided by branches of the external carotid artery, predominately the superficial temporal branch. Other branches of the external carotid artery namely: the deep auricular artery, anterior tympanic artery, ascending pharyngeal artery, and maxillary artery- may also contribute to the arterial blood supply of the joint.
  21. 21.  In order to work properly, there is neither innervation nor vascularization within the central portion of the articular disc. Had there been any nerve fibers or blood vessels, people would bleed whenever they moved their jaws; however, movement itself would be too painful.
  22. 22. Biomechanics of the joint during function  During jaw movements, only the mandible moves
  23. 23. Biomechanics of the joint during function   The two movements that occur at this joint are anterior gliding and a hinge-like rotation. When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.
  24. 24. Biomechanics of the joint during function   As this anterior gliding occurs, the head of the mandible rotates on the inferior surface of the articular disc. This permits simple chewing or grinding movements over a small range. 26
  25. 25. Jaw Movements: Muscle Action  The mandible is moved primary by the four muscles of mastication: the masseter, medial pterygoid, lateral pterygoid and the temporalis. These four muscles, all innervated by V3, work in different groups to move the mandible in different directions.
  26. 26. Jaw Movements: Muscle Action  Contraction of the lateral pterygoid acts to pull the disc and condyle forward within the glenoid fossa and down the articular eminence; thus, action of this muscle serves to open the mouth. The other three muscles close the mouth; the masseter and the medial pterygoid by pulling up the angle of the mandible and the temporalis by pulling up on the coronoid process.
  27. 27. Jaw Movements: Muscle Action Actions Muscles Depression (Open mouth) Lateral pterygoid Suprahyoid Infrahyoid Elevation (Close mouth) Temporalis Masseter Medial pterygoid Protrusion (Protrude chin) Masseter (superficial fibres) Lateral pterygoid Medial pterygoid Retrusion (Retrude chin) Temporalis Masseter (deep fibres) Side-to-side movements (grinding and chewing) Temporalis on same side Pterygoid muscles of opposite side Masseter
  28. 28. Depression & Elevation
  29. 29. Depression & Elevation (Medial View)
  30. 30. Lateral Movement
  31. 31. Lateral Movement
  32. 32. Lateral Movement (Medial View)
  33. 33. Protrusion & Retraction
  34. 34. Protrusion & Retraction (Medial View)
  35. 35. Jaw Movements The Role Of The Disc  On mouth closure, the inferior belly of the lateral pterygoid muscle relaxes and the condyle is pulled back to the fossa by the action of the masseter, medial pterygoid and temporalis muscles; however, the disc is firmly attached to the condyle and it pivots to its anterior position by means of the reciprocally innervated superior belly of the lateral pterygoid muscle.
  36. 36. Jaw Movements The Role Of The Disc  On mouth opening, contraction of the inferior belly of the lateral pterygoid muscle pulls the condyle downward and forward along the posterior aspect of the articular eminence; at this junction, the superior head of the lateral pterygoid muscle is relaxed, and this allows the disc to pivot posteriorly. The condyle, together with the tightly connected disc, slides down the slope of the eminence.
  37. 37. Thank You