lec1 med

• Temporomandibular joint

  A complex synovial articulation between the condyle of the mandible and glenoid fossa of temporal bone

  
• TMJ is similar to other joints in that it has osseous tissue and soft tissue
• TMJ


  • Both TMJ are joined by a single bone (mandibular bone), so movement in one joint cannot occur without similar coordinating movement in the other joint
  • The articular part is covered with dense connective tissue, not hyalin cartilage like other synovial joints
  • The movement of the upper compartment (gliding or translation) is independent from the movement of the lower compartment (rotatory)
  • There is a limit or fixed end point to the movement by bringing the teeth into maximum intercuspation
  • The head of the condyle and the disc act as one unit against the eminence, not against the fossa

  
• Types of motion of the mandible

  • Elevation
  • Depression
  • Protrusion
  • Retraction
  • Side to side movement
• Accessory motion in TMJ


  • Rotation movement occurs in the inferior joint compartment, approximately 2.5cm measured at the incisal edge
  • Translatory motion occurs in the upper joint compartment, approximately 1.5cm

  
• Osseous components of TMJ

  • Glenoid fossa
  • Tympanic plate
  • Condylar head of mandible
  • Articular eminence
  • Squamous portion of temporal bone
  • External auditory meatus

  
• Soft tissue components of TMJ


  • Articular disc
  • Muscular tissue
  • Bilaminar zone
  • Capsule
• Articular disc


  • Formed of dense fibrous collagenous tissue, also called fibrocartilage as it incorporates cartilage with fibrous connective tissue
  • Provides stabilization during condylar movement and shock absorption during mastication
  • Biconcave in shape, with anterior attachment to the upper head of the lateral pterygoid muscle and posterior attachment to loose connective tissue containing elastic fibers, which is highly vascular and innervated
  • Superior bilaminar zone holds it to the tympanic plate bone, and inferior bilaminar zone holds it to the condyle

  
• Function of the articular disc


  Separates the joint into superior and inferior compartments, filled with synovial fluid for lubrication, nutrition, and waste removal

  
• Muscles related to the TMJ

  • Masseter
  • Temporalis
  • Medial pterygoid
  • Lateral pterygoid

  
• Masseter and medial pterygoid muscles


  • Have their insertion at the inferior border of the mandibular angle, forming a sling that cradles the ramus of the mandible and produces powerful forces required for chewing
  • The masseter muscle has been divided into deep and superficial portions

  
• Lateral pterygoid muscle


  • Originates in two heads - the upper head from the greater wing of the sphenoid, and the lower head from the lateral wall of the lateral pterygoid plate
  • Inserts into the meniscus and the lower fibers insert into the condyle

  
• Bilaminar zone


  • Consists of elastic fibers that hold the meniscus to the tympanic plate (superior bilaminar zone) and to the neck of the condyle posteriorly (inferior bilaminar zone)
  • Functions to restrain disc movement in extreme translatory and rotational movements

  
• Capsule


  • Dense fibrous connective tissue that encapsulates all the structures of the TMJ
  • Laterally and medially the capsule is firm, while anteriorly and posteriorly it is loose to allow forward and backward movement
• Temporomandibular ligaments


  • Capsular ligament
  • Sphenomandibular ligament
  • Stylomandibular ligament

  
• Closing of the mandible

  1. Temporalis

  2. Masseter

  3. Medial pterygoid muscles
• Opening of the mandible


  1. Upper head of lateral pterygoid

  2. Suprahyoid muscles

  3. Infrahyoid muscles

  
• The mandibular branch of the trigeminal nerve provides motor innervation to the muscles of mastication

  
• Common symptoms of temporomandibular disorders


  • Facial pain
  • Pain in TMJ and surrounding tissues, including the ear
  • Limitation in opening and closing the mouth
  • Swelling in the side of the face
  • Clicking and crepitus
  • Pain in shoulders, neck, and back
  • Headache

  
• Jaw jerk reflex


  A stretch reflex that occurs by applying a downward tap on the chin, demonstrating the existence of a feedback loop from the jaw-closing muscles to their own motor neurons in the central nervous system

  
• Jaw open reflex


  Stimulating mechanoreceptors or nociceptors in the mouth triggers this reflex, with the pathway being polysynaptic and involving the trigeminal sensory nuclei or adjacent reticular formation, and the trigeminal motor nucleus

  
• Intercuspal position


  Achieved when maximum intercuspation of opposing teeth occurs, representing occlusal stability and a state of homeostasis in the masticatory system

  
• Classification of temporomandibular disorders

  • Masticatory muscle disorders (myofacial pain, myospasm, local muscle soreness, centrally mediated myalgia)
  • Temporomandibular joint disorders (derangement of condyle-disc complex, disc displacement, disc dislocation with/without reduction)

  
• Motor neurons


  n in the central nervous system
• Jaw open reflex


  Stimulating mechanoreceptors or nociceptors in the mouth triggers the jaw-opening reflex. The pathway is polysynaptic; the first synapse is in either the trigeminal sensory nuclei or the adjacent reticular formation and the final synapse is in the trigeminal motor nucleus

  
• Occlusion


  The intercuspal position is achieved when maximum intercuspation of opposing teeth occurs. Occlusal stability has been defined as "the equalization of contacts that prevents tooth movement after closure." A physiologic occlusion has been defined as "an occlusion in which a functional equilibrium or state of homeostasis exists between all tissues of the masticatory system"

  
• Classification of disorders of TMJ

  • Masticatory muscle disorders
  • Temporomandibular joint disorders

  
• Masticatory muscle disorders


  • Myofacial pain
  • Myospasm
  • Local muscle soreness
  • Centrally mediated mylagia

  
• Temporomandibular joint disorders


  • Derangement of condyle-disc complex
  • Structural incompability of articular surfaces
  • Inflammatory Disorders of TMJ

  
• Derangement of condyle-disc complex

  • Disc displacement
  • Disc dislocation with reduction
  • Disc dislocation without reduction
• Structural incompability of articular surfaces


  • Deviation in form (Disc,condyle,fossa)
  • Adhesion (disc to condyle, disc to fossa)
  • Subluxation (hypermobility)
  • Spontaneous dislocation
• Inflammatory Disorders of TMJ


  • Synovitis
  • Retrodiscitis
  • Arthritites (osteoarthrosis, osteoarthritis, polyarthrities)
  • Inflammatory disorders of associated structures (Temporal tendonitis, Stylomandibular ligament inflammation)
• Chronic mandibular hypomobility


  • Ankylosis (Fibrous, Bony)
  • Muscle contracture (Myostatic, Myosfibrotic)
  • Coronoid impedance

  
• Disease effect TMJ and associated structures


  • Intracapsular disorders of TMJ (Developmental anomalies, Inflammatory changes, Degenerative joint disease, Infections, Neoplasia, Drug-induced, Systemic factors)
  • Extracapsular disorders of TMJ (Infection, Trauma, Tumors, Muscular spasm)
• Myofascial Pain Dysfunction Syndrome (MPDS)

  Psychological factors, Occlusal factors, Habitual factors
• Signs and symptoms of MPDS

  • Unilateral, dull pain in ear or preauricular region
  • Pain may be stationary or referred to temporal region, to neck and to teeth
  • Ear symptoms: tinnitus, fullness, vertigo
  • Tenderness of one or more muscle mastication on palpation
  • Limitation or deviation of mandible on opening
  • Clicking

  
• Disc displacement


  • Type I (Type I A - clicking without pain, Type I B - clicking with pain)
  • Type II (Clicking with pain and opening of the mouth normal, open lock problem open cycle [with reduction])
  • Type III (without reduction - Anterior displacement of the disc, Pain, Lock joint, Restriction of mouth opening, Deviation of the mandible)
• Diagnosis


  • Patient history (Chief complaint, History of present illness, Past dental history, Medical history, History of trauma, History of stress/anxiety/depression, Family history, Social history)
  • Pain (Occur spontaneously or when do certain activities, Intermittent or constant, Gradually or paroxysmal, Duration, Sharp, dull, throbbing)
  • TMJ symptoms (Clicking or pop, Limitation or deviation, Pain and dysfunction in other joint of the body, Locked jaw or dislocation)
  • Clinical examination (Inspection, Palpation, Auscultation)
• Imaging for TMJ


  • Transcranial radiography
  • Planigraphy
  • Panoramic radiography
  • CBCT
  • Arthrography
  • Magnetic Resonance Imaging (MRI)
  • Arthroscopy of the upper compartment
  • Electromayography (EMG)
• Clinical examination is usually unsuccessful to exactly identify degenerative jawbone variations and so radiographic examination is achieved to benefit in TMJ diagnosis & management