The Temporomandibular Joint

1
Chapter 24

• The Temporomandibular Joint

2
Overview

• The stomatognathic system comprises the
  temporomandibular joint (TMJ), the masticatory
  systems, and the related organs and tissues such
  as the salivary glands
• Due to the proximity of this system with the
  other structures of the head and neck, an
  intimate relationship exists
• This relationship begins in the early stages of
  human embryology

3
ANATOMY
4
Bones

• Mandible
• Maxilla
• Zygomatic arch
• Temporal bone

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Temporomandibular Joint

• The articular surfaces of the temporomandibular
  joint are lined by fibrous tissue - this reflects
  the development of the joint
• Unlike all other synovial joints whose articular
  surfaces develop endochondrally and are therefore
  lined by hyaline cartilage, the temporomandibular
  joint develops in membrane

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Intra-articular Disc

• Fibrous in structure
• Divides the joint cavity into two regions
• Thinnest centrally
• Attaches anteriorly to the lateral pterygoid
• Attaches posteriorly to the condyle

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Joint Capsule

• Capsular ligaments fibers only pass between
  the temporal bone and mandible on the lateral
  side
• Intrinsic ligaments short fibers which pass
  from the bone to the intra-articular disc

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Ligamentous support

• Lateral TMJ ligament
• Stylomandibular ligament

9
Muscles

• Lateral pterygoid
• Origin
• Upper head arises from the infratemporal surface
  of the greater wing of the sphenoid
• Lower head arises from the lateral surface of the
  lateral pterygoid plate
• Insertion - The anterior aspect of the neck of
  the mandibular condyle and capsule of the TMJ
• Innervation - A branch of the mandibular division
  of the trigeminal nerve
• Function
• Upper head - involved mainly with chewing, and
  functions to anteriorly rotate the disc on the
  condyle during the closing movement
• Lower head - exerts an anterior, lateral, and
  inferior pull on the mandible, thereby opening
  the jaw, protruding the mandible, and deviating
  the mandible to the opposite side

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Muscles

• Medial pterygoid
• Origin - Deep origin situated on the medial
  aspect of the mandibular ramus
• Insertion - The inferior and posterior aspects of
  the medial subsurface of the ramus and angle of
  the mandible
• Innervation - A branch of the mandibular division
  of the trigeminal nerve
• Function - Working bilaterally - assists in mouth
  closing. Working unilaterally deviation of the
  mandible toward the opposite side

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Muscles

• Masseter - two-layered quadrilateral shaped
  muscle.
• Origin
• The superficial portion arises from the anterior
  two-thirds of the lower border of the zygomatic
  arch
• The deep portion arises from the medial surface
  of the zygomatic arch.
• Insertion - On the lateral surface of the
  coronoid process of the mandible, upper half of
  the ramus and angle of the mandible
• Innervation - A branch of the mandibular division
  of the trigeminal nerve
• Function - The major function of the masseter is
  to elevate the mandible, thereby occluding the
  teeth during mastication.

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Muscles

• Tempororalis
• Origin - The floor of the temporal fossa and
  temporal fascia
• Insertion - On the anterior border of the
  coronoid process and anterior border of the ramus
  of the mandible
• Innervation - A branch of the mandibular division
  of the trigeminal nerve
• Function - assists with mouth closing/side-to-side
  grinding of the teeth. Also provides a good
  deal of stability to the joint

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Muscles

• Digastric
• Origin - The posterior belly arises from the
  mastoid, or digastric, notch immediately behind
  the mastoid process of the temporal bone.
• Insertion - The posterior belly passes downwards
  and forwards towards the hyoid bone where it
  becomes the intermediate digastric tendon and
  joins with the anterior belly.
• Nerve Supply - derived from the digastric branch
  of the facial nerve.
• Vasculature - arterial blood supply from the
  posterior auricular and occipital arteries.
• Action - The muscle depresses the mandible and
  can elevate the hyoid bone. The posterior bellies
  act in unison and are particularly active during
  swallowing and chewing.

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BIOMECHANICS
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Biomechanics

• TMJ motions involve a combination of rolls and
  glides of the mandibular head and disc
• All TMJ motions involve all or some of the
  following
• Anterior/posterior glide
• Medial/lateral glide
• Inferior/posterior glide

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Opening and closing

• Mouth opening
• Anterior glide
• Lateral glide
• Inferior glide
• Mouth closing
• Posterior glide
• Medial glide
• Superior glide

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Lateral Deviation

• Contralateral deviation
• Anterior, inferior and lateral glide of the
  mandibular head and disc
• Ipsilateral deviation
• Posterior, superior and medial glide of the
  mandibular head and disc

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Protrusion and Retrusion

• Protrusion
• Anterior, inferior and lateral glide of the
  mandibular head and disc
• Retrusion
• Posterior, superior and medial glide of the
  mandibular head and disc

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EXAMINATION
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Examination

• As with any other synovial joint, there are a
  number of possible causes/scenarios
• Local cause
• Referred cause
• Loss of motion with or without pain
• Excessive motion with or without pain

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History

• There are three cardinal features of
  temporomandibular disorders (TMD)
• Restricted jaw function (intermittent or
  progressive)
• Joint noise (significant if associated with other
  factors)
• Orofacial pain (Pain that is centered immediately
  in front of the tragus of the ear and projects to
  the ear, temple, cheek, and along the mandible is
  highly-diagnostic for TMD)
• It is important to observe the patients mouth
  while they talk

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History

• Attempt to determine a specific mechanism
• Trauma (including surgery controlled trauma)
• Posture
• Emotional factors
• Parafunctional habits (cheek biting, nail biting,
  pencil chewing, teeth clenching (day), bruxism
  (night))
• Symptom-provoking motions of the TMJ or
  neighboring joint(s)

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History

• The patients past dental and orthodontic history
  
• Whether the patient has experienced any locking
  of the jaw
• Whether the symptoms are improving or worsening

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History

• Systems review
• Pain or dysfunction in the orofacial region can
  often be due to non-musculoskeletal causes
• Otolaryngologic disease
• Neurologic disease
• Vascular disease
• Neoplastic, and infectious disease
• Psychogenic disease

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Observation

• The forward head posture is frequently associated
  with TMD..try it
• A lateral deviation of the jaw, evidenced by a
  malalignment or malocclusion of the upper and
  lower teeth, may cause an adaptive shortening of
  the mastication muscles on one side, and a
  lengthening of the mastication muscles on the
  contralateral side.

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Observation

• Cavities, wear patterns, and restored and missing
  teeth should be noted
• Tooth wear and fracture are often destructive
  signs of parafunctional habits
• The rest position of the TMJ should be noted
• The rest position of the TMJ is determined by
  gently placing the little finger with the palmar
  portion facing anteriorly into the external
  auditory meatus. From an open mouth position,
  the patient is asked to slowly close their mouth.
  At the point of the resting position, the
  patients mandibular heads should be felt to
  gently touch the finger.

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Range of Motion

• The range of motion of the cervical spine,
  craniovertebral joints and the shoulders should
  be assessed
• The range of motion of the neck and jaw should
  then be assessed
• Active range of motion with passive overpressure
  to assess the end feel.

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Range of Motion

• All movements should be smooth and without noise
  or pain
• If pain occurs, a determination should be made as
  to where in the range the pain occurs, and the
  location of the pain
• The type and temporal sequence of joint clicking
  can provide the clinician with information

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Joint Noise

• Reciprocal clicking is defined as clicking that
  occurs during opening and again during closing.
• Early clicking usually indicates a small anterior
  displacement
• Late clicking usually indicates that the disc has
  been further displaced
• Often due to articular hypermobility, and is
  accompanied by a deviation of the jaw toward the
  contralateral side.

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Mouth Opening

• Mouth opening is the most revealing and
  diagnostic movement for TMD
• Normal motion tested using knuckle test
  (approximately a two-three-knuckle width of the
  non-dominant hand) or more objectively by
  measuring (closer to 40 mm)
• A limited opening of the jaw may indicate joint
  hypomobility, muscle tightness, or the presence
  of trigger points within the elevator muscles
  the temporalis, masseter and medial pterygoid
• Other causes of diminished mandibular opening
  include structural disorders of the TMJ, such as
  ankylosis, internal derangements, and gross
  osteoarthritis

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C and S Curves

• A C-pattern of motion occurs if the
  hypomobility is due to internal derangement
• The mandible deviates toward the involved side in
  the midrange of opening before returning to
  normal.
• An S-pattern of movement while opening the
  mouth may indicate a muscle imbalance. An arc
  may indicate a muscle imbalance
• Lateral excursion of the mandible with mouth
  opening implicates contralateral structures such
  as the contralateral disc, masseter, temporalis,
  lateral pterygoid, or the lateral ligaments

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Palpation

• Palpation of the TMJ is used to assess
  tenderness, skin temperature, muscle tone,
  swelling, skin moisture, and the location of
  trigger points
• Palpations of the lateral and posterior aspects
  of the temporomandibular joints are performed
  bilaterally and simultaneously

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Strength Testing

• It is important to be able to selectively stress
  the muscles of mastication and facial expression
  to determine whether they are implicated in the
  symptoms

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Ligament Stress Tests

• The ligament stress tests assess the integrity of
  the capsule and ligaments
• Positive findings include excessive motion as
  compared to the other side, or pain
• Two structures are primarily tested
• Temporomandibular ligament
• Joint capsule

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Passive Articular Mobility

• The passive articular mobility tests assess the
  joint glides and the end feels
• Findings are compared with each side
• Pain or a restricted glide are positive findings
  and may indicate articular involvement or a
  capsular restriction.
• It is important to check the specific glides that
  are related to the loss of active motion. For
  example, if a patient demonstrated diminished
  mouth opening mouth, the combined anterior,
  inferior, and lateral glide is assessed for each
  joint.

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Articular glides

• Mouth opening, contralateral deviation, and
  protrusion all involve an anterior, inferior and
  lateral glide of the mandibular head and disc
• Mouth closing, ipsilateral deviation, and
  retrusion all involve an posterior, superior and
  medial glide of the mandibular head and disc

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Conclusions

• If the joint glides are normal the joint is OK
• Check ligaments and surrounding tissues
• If the joint glides are restricted, the cause
  could indicate a joint/joint capsule restriction,
  a ligamentous adhesion or adaptive shortening of
  the surrounding tissues need to mobilize the
  offending joint and re-assess
• The intervention should always match the
  diagnosis!!

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Articular tests

• Dynamic loading
• The patient bites forcefully on a cotton roll or
  tongue depressor on one side. This maneuver
  loads the contralateral TMJ.
• Joint compression
• The clinician, standing behind the seated or
  supine patient, places the fingers of each hand
  under each side of the mandible, with the thumbs
  resting on the ramus. The mandible is then
  tipped posteriorly and inferiorly to compress the
  joint surfaces

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Neurological tests

• Trigeminal sensation
• Trigeminal reflex

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INTERVENTION
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Intervention

• Based on
• Stage of healing. Chronic TMD pain often occurs
  because of secondary factors
• A fixed head forward posture
• Abnormal stress levels
• Depression
• Oral parafunctional habits
• Structure involved

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Acute Stage

• The acute patient typically demonstrates
• A capsular pattern of restriction (decreased
  ipsilateral opening and lateral deviation to the
  contralateral side), with pain and tenderness on
  the same side
• There may be associated ligamentous damage
  (positive stress tests), or muscular damage
  (positive strength tests)

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Acute Stage

• The usual methods of decreasing inflammation are
  recommended PRICEMEM
• Protection
• Rest
• Ice
• Compression
• Elevation?
• Manual therapy
• Early motion
• Medications

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TMJ Exercises

• Acute stage
• 6x6 exercise protocol of Rocabado
• Cork exercise
• Tongue positioning during mouth opening and
  closing

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TMJ Exercises

• Functional Stage
• Strengthening exercises for the cervicothoracic
  stabilizers, and the scapular stabilizers
• Stretching exercises for the scalenes, trapezius,
  pectoralis minor, and levator scapulae and the
  suboccipital extensors

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Home (Automobilization) Exercises

• Mouth opening exercise
• Tongue depressor exercise
• Toothpick exercise
• Distraction mobilization

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Functional (Chronic) Stage

• Postural and patient education should form the
  cornerstone of any plan of care for TMD
• Psychotherapy referral
• Manual techniques
• Exercise
• Thermal and electrotherapeutic modalities
• Trigger point therapy