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Okeson: Mgmt of TMD & Occlusion
Chapter 1: Functional Anatomy and Biomechanics of Mastication .................................................. 2
Chapter 2: Functional Neuroanatomy and Physiology of Masticatory System.................................. 4
Chapter 3: Alignment and Occlusion of the Dentition...................................................................... 6
Chapter 4: Mechanics of Mandibular Movement ............................................................................. 8
Chapter 5: Criteria for Optimal Functional Occlusion...................................................................... 9
Chapter 6: Determinates of occlusal morphology........................................................................... 10
Chapter 7: Causes of functional disturbances in the masticatory system......................................... 12
Chapter 8: Signs & Symptoms of TMD......................................................................................... 13
Chapter 9: History & Examination for TMD ................................................................................. 15
Chapter 10: Diagnosis of TMD...................................................................................................... 16
Chapter 12: Treatment of Masticatory Muscle Disorders ............................................................... 21
Chapter 13: TMD and Treatments ................................................................................................. 22
Chapter 14: Tx of Chronic MN Hypomobility and Growth Disorders............................................ 23
Chapter 20: Restorative Considerations in Occlusal Therapy......................................................... 30
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Chapter 1: Functional Anatomy and Biomechanics of Mastication Masticatory system – functional unit of the body primarily responsible for chewing, speaking, and
swallowing - Composed of: bones, joints, ligaments, and teeth
Maxilla: two maxillary bones are fused together at the midpalatal suture making up greater part of upper
facial skeleton.
• Superiorl border forms floor of nasal cavity and floor of each orbit
• inferiorly forms palate and alveolar ridges
Mandible: U-shaped bone supporting lower teeth and making lower facial skeleton with no bony attachments
to skull, suspended below maxilla by muscles, ligaments, and other soft tissues providing the mobility
necessary to function with maxilla.
• superior aspect- alveolar process and the teeth.
• body of the mandible - form mandibular angle and ascending ramus extending upward as two
processes - coronoid process and condyle which articulates with the cranium
Temporal bone: mandibular condyle articulates with squamous portion of temporal bone - a concave fossa
where the condyle is situated aka articular or glenoid fossa
Muscles of Mastication: have only one nerve ending near the middle of the fiber, innervates each fiber.
Higher myoglobin = deeper red & slow but sustained contraction (type I muscle fibers), well-developed
aerobic metabolism, thus resistant to fatigue. Lower concentrations of myoglobin are whiter (type II fibers),
fewer mitochondria and rely more on anaerobic activity for function, capable of quick contraction but fatigue
more rapidly.
1. Masseter: elevates mandible and teeth brought into contact.
o Powerful, provides force necessary to chew efficiently, may aid in protruding the
mandible.
2. Temporalis: elevates the mandible and the teeth are brought into contact.
3. Medial Pterygoid: with masseter, forms muscular sling supporting the mandible at mandibular angle.
• Elevates mandible and teeth are brought into contact, also active in protruding the mandible.
4. Inferior Lateral Pterygoid: functions with the mandibular depressors to lower mandible and condyles glide
forward and downward on the articular eminences.
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5. Superior Lateral Pterygoid: active during power stroke (movements involving closure of mandible) and
when teeth are held together.
6. Digastrics:
• right and left digastrics contract to help depress mandible and teeth brought out of contact.
• along with suprahyoid and infrahyoid muscles, elevate the hyoid bone, necessary function for
swallowing
Chapter 2: Functional Neuroanatomy and Physiology of Masticatory System Central Pattern Generator (CPG): pool of neurons controlling rhythmic muscle activities like
chewingEfficient pattern minimizes damage to structures, learned and repeated pattern called muscle
engram.
The three major functions of the masticatory system are:
(1) mastication
(2) swallowing
(3) speech.
• Secondary functions aid in respiration and expression of emotions.
Mastication: rhythmic and well-controlled separation and closure of maxillary and mandibular teeth, via
CPG in brainstem.
• chewing stroke is tear-shaped, divided into opening & closing movement.
o Closing further divided: crushing phase and grinding phase.
Early studies: teeth do not actually contact during mastication. Speculated food between teeth, along with the
acute response of the neuromuscular system, prohibits tooth contacts.
Other studies: have revealed that tooth contacts occur during mastication.
• New Food - few contacts initially,
• bolus broken down - frequency of tooth contacts increases.
• final stages of mastication contacts occur during every stroke.
• Two types of contact have been identified:
o gliding contact - cuspal inclines pass by each other
o single contact - occurs in the maximum intercuspal position.
Average contact time during mastication: 194 msec.
• contacts influence/dictate initial opening and final grinding phase
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• occlusal condition can influence entire chewing stroke
• quality and quantity of tooth contacts relay sensory information to CNS about chewing stroke,
feedback alters chewing stroke to food being chewed.
• tall cusps/deep fossae vertical chewing stroke
• flattened/worn teeth broader chewing
stroke.
chewing strokes of normal vs those with TMJ pain have marked differences.
• Normal: chewing strokes well rounded, definite borders, less repeated.
• TMJ pain: repeat pattern, short strokes, slower, irregular pathway-all relatable to altered functional
movement of condyle around which pain is centered.
Maximum forces:
• Molars 91 to 198 pounds
• central incisors 29 to 51 pounds.
Swallowing:
Mandible stabilization important part of swallowing, must be fixed so contraction suprahyoid and infrahyoid
muscles can control movement of hyoid bone.
• Somatic swallow - normal adult swallow using teeth for mandibular stability.
o average contact time 683 msec. (3X longer than mastication).
o force applied to teeth during about 66.5 pounds, 7.8 pounds more than during mastication.
• Visceral swallow – no teeth present (e.g. infant) - mandible must be braced by other means, placing
tongue forward & between dental arches/gum pads, occurs until posterior teeth erupt.
Studies: swallowing cycle occurs 590 times a day, 146 cycles during eating, 394 cycles between meals while
awake, 50 cycles during sleep. Lower levels of salivary flow during sleep result in less need to swallow.
Speech
Early stages of life taught proper articulation.
Tooth contacts do not occur during speech.
• If malpositioned tooth contacts during speech, sensory input relayed information to CNS, which
alters speech pattern to avoid the tooth contact, new pattern may result in a slight lateral deviation of
mandible to produce desired sound without tooth contact.
For many years degree and number of nociceptors stimulated were assumed to be responsible for intensity of
pain perceived by the CNS.
• Not found to be true clinically.
• In some patients, small injuries create great pain; in others only mild pain is reported with much
greater injury.
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• As pain has been studied, become increasingly clear that degree of suffering does not relate well to
amount of tissue damage. Instead the degree of suffering relates more closely to the patient's
perceived threat of injury and amount of attention given to injury.
Pain terminology:
• Nociception - noxious stimulus originating from sensory receptor, carried into the CNS by the
primary neuron.
• Pain is unpleasant sensation perceived in the cortex
• Suffering - how human reacts to perception of pain.
• Pain behavior - individual's audible and visible actions that communicate suffering to others.
• source of pain is where the pain originates.
• site of pain is where the patient perceives the pain to be coming from.
The experience of pain (and eventually suffering) may be the most important consideration in caring for
patients.
Types of Pain:
• Central pain - When a tumor or other disturbance is present in the CNS, the pain is often felt in
peripheral structures.
• Projected pain - neurologic disturbances causing pain sensations down the peripheral distributions of
same nerve root that is involved in disturbance.
3. Referred pain. sensations are felt in other branches of nerve
• Referred pain is not a haphazard occurrence but seems to follow three clinical rules:
o most frequently within a single nerve root, passing from one branch to another (e.g., a
mandibular molar referring pain to a maxillary molar).
o can be felt outside the nerve responsible for it, generally moves cephalad (i.e., upward,
toward the head) and not caudal.
o In trigeminal area, referred pain never crosses midline unless it originates at midline, e.g.
pain in right TMJ will not cross over to left side of face. (not true for cervical region or
below)
Local provocation of pain source increase in symptoms
Local provocation of site of pain generally does not increase symptoms
Chapter 3: Alignment and Occlusion of the Dentition Occlusion- static relationship of teeth, basic to all aspects of dentistry
Neutral position – tooth position with equal labio-lingual & bucco-lingual forces
• Tooth stability: tooth too far lingual & tongue moves it buccally & vice versa
• Tongue & lip forces constant – can move teeth (as can muscular forces)
o Large active tongue get open bite
• Proximal contacts also help maintain tooth alignment
o Loss of tooth struct or extraction mesial tipping
• TMJs provide guidance for posterior mandible, determine character of mandibular movement
posteriorly.
Anterior controlling factors:
• incisal edges of mandibular teeth occlude with lingual surfaces of maxillary anterior teeth in protrusion
or lateral movement.
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• Steepness of lingual surfaces determines amount of vertical movement of the mandible.
• Anterior guidance is variable & can be altered by dental procedures, such as restorations, orthodontia,
and extractions and pathologic conditions (caries, habits, and tooth wear).
Understanding the controlling factors:
• Mandibular movement determined by anatomy of TMJs posteriorly & anterior teeth anteriorly
• Mandibular movement both vertical & horizontal component, relationship between components is
significant in study of mandibular movement.
• vertical component is a function of the supero-inferior movement
• horizontal component a function of the antero-posterior movement.
Significance of anterior and condylar guidances: they influence posterior tooth shape.
Factors that influence cusp height and depth of fossae are vertical determinants of occlusal morphology.
Length of cusp and depth of opposing fossa are determined by:
1. ACF of mandibular movement (i.e., anterior guidance)
2. PCF of mandibular movement (i.e., condylar guidance)
3. Nearness of the cusp to these controlling factors
Movement of the mandible when the controlling factors are not identical. The nearer the point is to a
controlling factor, the more its movement is influenced by the factor.
Effects of Anterior guidance on cusp tips:
Anterior guidance a function of relationship between maxillary & mandibular anterior teeth.
• Increase in horizontal overlap decreased anterior guidance angle, less vertical component to
mandibular movement, and flatter posterior cusps.
• Increase in vertical overlap increased anterior guidance angle, more vertical component to
mandibular movement, and steeper posterior cusps.
Effects of the plane of occlusion on cusp height:
• As horizontal overlap increases, anterior guidance angle decreases.
• As vertical overlap increases, anterior guidance angle increases.
• Flat plane of occlusion greater angle mandibular posterior teeth move away from maxillary
posterior teeth taller cusp.
• Acute plane of occlusion smaller angle of mandibular posterior tooth movement flatter teeth
can be.
Effects of lateral translation movement on cups height:
• When distance exists between medial wall and medial pole of orbiting condyle and the
temporomandibular (TM) ligament allows some movement of the rotating condyle, lateral translation
movement can occur. More medial wall from condyle = greater lateral translation movement.
• Looser TMJ ligament = greater amount of mandibular translation movement = posterior cusps
shorter to permit lateral translation without creating contact.
• The greater the lateral translation movement, the shorter is the posterior cusp.
VERTICAL DETERMINANTS OF OCCLUSAL MORPHOLOGY (CUSP HEIGHT AND FOSSA DEPTH)
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HORIZONTAL DETERMINANTS OF OCCLUSAL MORPHOLOGY (RIDGE AND GROOVE DIRECTION)
Chapter 7: Causes of functional disturbances in the masticatory system 1 of 4 people report awareness of TMD, less than 10% of these people get help—most patients between 20 & 40 years old No simple cause and effect relationship between occlusion and TMD
• either the disorder has multiple causes, and no single treatment can affect all the causes • disorder not a single problem, umbrella term grouping multiple disorders.
Mandible closes condyles in most supero-anterior position with even simultaneous contacts directing forces through long axes Mandible moves eccentricallyanterior teeth contact and disocclude posterior teeth. Lack of occlusal stability may be:
• genetic, developmental, or iatrogenic causes, alterations of normal anatomic form. • lack of harmony between stable intercuspal position (ICP) of teeth and musculoskeletally stable
(MS) position of joints.
TMD Development Masticatory system structures tolerate some functional change, but if it exceeds a critical level, alteration of tissues beginsknown as the structural tolerance Numerous factors can contribute to TMD.
• predisposing factors increase risk of TMD • initiating factors cause the onset of TMD • perpetuating factors interfere with healing or enhance the progression of TMD
In some instances a single factor may serve one or all of these roles. Major factors associated with TMD:
These vary from patient to patient Occlusal features in TMD patients but rare in normal subjects:
• presence of a skeletal anterior open bite • retruded contact position (RCP) and ICP slides of greater than 2 mm • overjets of greater than 4 mm
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• five or more missing and unreplaced posterior teeth. Not only rare in healthy individuals, also in patient populations, limited diagnostic usefulness. For functional relationship between mandible and cranium, occlusal condition affects some TMDs:.
• occlusal condition affects orthopedic stability of mandible as it loads against cranium. • acute occlusal changes can influence mandibular functionTMD symptoms
Orthopedic instability & teeth not in occlusion condyles maintained in MS positions by elevator muscles. Orthopedic instability and teeth brought into contactonly one tooth may contact Individual chooses to maintain stable joint position & occlude on one tooth or bring teeth into a more stable occlusal position compromising joint stability. Problems arise when orthopedically unstable condition is loaded by elevator muscles or extrinsic forces
• loading occurs when a joint is not in a stable relationship with disc and fossaunusual movement can occur in attempt to gain stability.
• This small movement a translatory shift between disc and condyle can lead to strain to discal ligaments and eventually elongation of ligaments and thinning of disc.
• changes can lead to a group of intracapsular disorders (chapter 18) Two factors determine whether an intracapsular disorder will develop:
• degree of orthopedic instability • amount of loading.
Orthopedic instabilities with discrepancies of 1 or 2 mm are probably not significant enough to create a problem.
• as discrepancy between MS position of condyles and maximum intercuspation of teeth becomes greater, the risk of intracapsular disorders increases.
Bruxing patients with orthopedic instability represent a higher risk for developing problems than nonbruxers with same orthopedic instability.
• forceful unilateral chewing can provide the mechanics that lead to sudden intracapsular disorders • more significant malocclusion may not always be patient who develops the disorder
Dental malocclusion: specific relationship of teeth to each other, does not necessarily reflect risk factors for development of functional disturbances in the masticatory system
Chapter 8: Signs & Symptoms of TMD Three categories of TMD signs and symptoms: Muscles, TMJ, Dentition
Dysfunction: common clinical symptom associated with muscle disorders usually seen as a decrease in the
range of mandibular movement
Acute malocclusion: is the result of the muscle disorder, not the cause
Masticatory muscle model:
If local muscle soreness does not resolve, changes in
the muscle tissues may develop, resulting in
prolonged pain input
CNS influenced pain disorders:
Myofascial pain – local areas of firm hypersensitive
bands of tissuetrigger points, trigger point has
select group of motor units contracting, no overall
shortening of the muscle results (no jaw positional
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change), trigger points often refer pain to other areas of the head
• E.g. a TP in neck causes pain in temple…so treat TP!
• TP may be active or latent (not sensitive to palpation at that time)…look for them when
symptoms present
• TP DO NOT resolve w/o treatment
Myospasm – a CNS induced tonic muscle contraction
• Jaw positional changes can occur due to muscles in spasm
• Firm mucles upon palpation indicate spasm
As muscle pain progresses from acute to chronic, effectiveness of local treatment diminishes…catch it early
How pain gets chronic
• Protracted cause – fail to eliminate cause
• Recurrent cause – recurrent episodes ( bruxism, trauma)
inflammation and destruction of articular surfaces, no treatment since cause is unknown
• Hyperuricemia – gout – increase in urate leading to urate crystals in joints, usually distal extremities,
treatment is to lower serum uric acid levels (modify diet)
• Psoriatic arthritis – inflammation with psoriasis, no treatment because cause unknown
• Ankylosing spondylitis – chronic inflammatory disease, mainly of spinal column, can affect TMJ
occasionally, unknown cause so no definitive treatment.
Inflammatory disorders of associated structures – tendons and ligaments become painful
• Temporal tendonitis – hyperactive temporalis muscle can cause soreness at insertion to coronoid
process. Treatment is rest, if clenching/bruxism then make stabilization appliance, analgesics can
also help
• Stylomandibular ligament inflammation - pain at angle of mandible radiating towards TMJ and ear,
treated with rest.
General considerations when treating acute trauma to the TMJ – initial exam must determine if trauma
caused soft or hard tissue damage – radiographs, once hard tissue identified and managed the soft tissues of
TMJ can be addressed.
Chapter 14: Tx of Chronic MN Hypomobility and Growth Disorders I. Chronic mandibular hypomobility - the inability of the pt to open the mouth to a mormal range; rarely
accompanied by painful symptoms of progressive destructive changes; If function is impaired, tx is
indicated; no impaired fx, no tx
• A. Ankylosis – abnormal immobility of a joint; cause – hemarthrosis secondary to trauma and
inflammation leads to more fibrous tissue; history – limited mouth opening w/out pain;
definitive tx may not be indicated
o 1. Capsular fibrosis – most common and can occur between the condyle and the disc
or the disc and the fossa
o 2. Bony – rare; occurs between the condyle and the fossa (disc would have to have
been lost)
• B. Muscle contracture – painless shortening of a muscle
o 1. Myostatis – muscle is kept from fully lengthening (stretching) for a prolonged time;
often secondary to another disorder
Two types of exercise to reestablish resting length of muscles:
a. Passive stretching – pt opens to full limit of movement and then
gently stretches beyond restriction
b. Resistant-opening exercises - A neurologic feedback can be used
to help achieve relaxation. This is accomplished by initiating mild
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contraction of the antagonistic muscle groups. When the elevator
muscles will not properly relax, contraction of the depressors provided
by resistance to opening feeds neurologic input to the elevator muscles
to relax.
o 2. Myofibrotic – excessive tissue adhesions within the muscles or sheaths, so can’t
slide over themselves disallowing full lengthening; follows trauma or myositis
o C. Coronoid process impedance - During mandibular opening the coronoid process
passes anteroinferiorly between the zygomatic arch and the lateral surface of the maxilla.
If its pathway is impeded, it will not slide smoothly and the mouth will not open fully.
Causes: long coronoid process or encroachment of fibrous tissues
Tx: alteration of responsible tissues
II. Growth disorders
• A. Congenital and developmental bone disorders – trauma is contributing factor in many
cases
o 1. Agenesis – no growth
o 2. Hypoplasia – insufficient growth
o 3. Hyperplasia – too much growth
o 4. Neoplasia – uncontrolled, destructive growth
• B. Congenital and development muscle disorders – normal range of MN movement is likely
present with any of these conditions
o 1. Hypotrophy – lack of development
o 2. Hypertrophy – over development
o 3. Neoplasia – uncontrolled, destructive growth
Because most bone growth and muscle growth disorders are not associated with pain or dysfunction,
supportive therapy is not indicated. Definitive treatment for these disorders does not fall within the context