TMJ

• Temporomandibular Joint


  Allows for movement of the mandible for mastication, speech, and respiration

  
• Temporomandibular Joint


  • Sensory innervation: auriculotemporal and masseteric branches of V3 trigeminal mandibular branch
  • Motor function: muscles of mastication-Masseter, temporalis, medial pterygoid, lateral pterygoid
  • Blood supply: external carotid artery- superficial temporal branch. Venous return by superficial temporal, maxillary, and pterygoid plexus of veins
  • Lymph: drained deeply into the superior deep cervical nodes

  
• Joint Bones


  The TMJ is the articulation of the temporal bone and the mandible on each side of the head

  
• Temporal Bone


  • The squamous portion contains the Glenoid fossa (mandibular fossa)

  
• Mandible


  • The condyle of the mandible articulates with the temporal bone

  
• TMJ abnormalities


  • Left condylar remodeling-articular eminence pronounced
• Joint Capsule


  A fibrous joint capsule completely encloses the TMJ
• Joint Disc


  • The fibrous joint disc or meniscus is located between the temporal bone and mandibular condyle, allowing articulation between the two bones
  • The disc completely divides the TMJ into two compartments or synovial cavities: the upper and lower synovial cavities

  
• Ligaments Associated with TMJ

  • Temporomandibular
  • Stylomandibular
  • Sphenomandibular

  
• Temporomandibular Ligament


  Located on the lateral side of each joint from zygomatic process to neck of condyle, prevents excessive retraction of mandible

  
• Stylomandibular Ligament


  Formed from thickened cervical fascia, prevents excessive protrusion
• Sphenomandibular Ligament


  • Not strictly part of TMJ, more of a sling for the mandible, located on the medial side, variable anatomy, landmark for IA injection
  • Can inhibit anesthetic from reaching Inferior alveolar nerve

  
• Auriculotemporal Nerve


  Communication with the facial nerve sometimes occurs, can be anesthetized by Gow-gates injection and sometimes Inferior alveolar nerve block

  
• The sphenomandibular ligament may act as an outer barrier to the diffusion of the local anesthetic agent if the medial surface of the mandible is not contacted with the needle at the deeper mandibular foramen with the inferior alveolar nerve

  
• Jaw Movements


  Two basic types: gliding (sliding) and rotational (hinge) movements
• Gliding Movement


  1. Occurs mainly between the disc and the articular eminence of the temporal bone in the upper synovial cavity, with the disc plus the condyle moving forward or backward, and down and up the articular eminence

  2. Allows the lower jaw to move forward or backward

  
• Protrusion


  Bringing the lower jaw forward, involves bilateral contraction of both lateral pterygoid muscles

  
• Retraction


  Bringing the lower jaw backward, involves contraction of the posterior parts of both temporalis muscles

  
• Elevation


  Muscles of mastication involved in elevating the mandible during closing of the jaws: bilateral contractions of the masseter, temporalis, and medial pterygoid muscles

  
• Depression


  Anterior suprahyoid muscles involved in depressing the mandible when they bilaterally contract during opening of the jaws with the hyoid bone stabilized by the other hyoid muscles

  
• Lateral Deviation


  Shifting the lower jaw to one side, involves contraction of the contralateral lateral pterygoid muscles

  
• Mastication Power Stroke


  Movement from a laterally deviated position back to the midline, if food is on the right the mandible will be deviated to the right by the left lateral pterygoid muscle, the power stroke will return the mandible to the center, accomplished by the left posterior part of the temporalis muscle, with the closing jaw muscles on the right side contracting to crush the food

  
• Lateral deviation of the jaw


  • Contraction of the contralateral lateral pterygoid muscles is involved

  
• Mastication power stroke


  1. Mandible moves from laterally deviated position back to midline

  2. Accomplished by left posterior temporalis muscle

  3. All closing jaw muscles on right side contract to crush food

  
• Resting position of TMJ

  • Not with teeth biting together
  • Muscular balance and proprioceptive feedback allow physiologic rest for mandible
  • Interocclusal clearance or freeway space of 2-4mm between opposing teeth

  
• Temporomandibular disorders (TMD)


  • Chronic joint tenderness, swelling, and painful muscle spasms
  • Difficulties of joint movement such as limited or deviated mandibular opening

  
• Types of temporomandibular disorders

  • Myofascial pain and dysfunction
  • Internal derangements
  • Arthritis
• Bruxism


  • Palpation of muscles of mastication to detect dysfunction (masseter, temporalis, medial pterygoid, lateral pterygoid, anterior digastric, mylohyoid)

  
• Subluxation


  When the head of each condyle moves too far anteriorly on the articular eminence
• Trismus


  Reduced opening of the jaws, can occur with TMD or odontogenic infections

  
• Most cases of TMD improve over time with conservative treatments
• TMD emergency


  Acute episode when patient opens mouth too wide, causing subluxation or dislocation of both TMJ joints
• The bridge of the nose is formed from the paired nasal bones
• The anterior opening of the nasal cavity, the piriform aperture, is large and triangular
• The floor of the nasal cavity is formed from the palatine processes of the maxillae anteriorly and the horizontal plates of the palatine bones posteriorly

  
• Lateral walls of nasal cavity

  • Formed mainly by the maxillae
  • Have 3 projecting structures extending inward - the superior, middle, and inferior nasal conchae or turbinates
• Nasal meatus


  Channel protected by each nasal concha, has openings for paranasal sinuses and nasolacrimal duct to communicate with nasal cavity
• Paranasal sinuses


  • Paired, air-filled cavities in bone, project laterally, superiorly, and posteriorly
  • Lined with mucous membranes continuous with nasal cavities
  • Warm and filter air
  • Have ostia or openings that communicate with nasal cavity
• The mucous membranes of the sinuses can become inflamed and congested with mucus, causing sinusitis
• Infection in one sinus can travel to other sinuses, and dental disease processes can also cause secondary sinusitis and sinus perforations