Mastication and Occlusion Flashcards
What is the TMJ?
Temporomandibular joint
What type of joint connects the temporal bone and the mandible?
Synovial joint
In a synovial joint what is the name given to the cartilage that surrounds the bone?
Hyaline articular cartilage
Where does the condyle sit in the TMJ?
In the glenoid fossa
What is the glenoid fossa bounded by?
articular eminence
tympanic plate of temporal bone
How many layers does the joint capsule have?
2
outer fibrous layer
inner synovial membrane
What is the purpose of the synovial membrane?
secretes synovial fluid to fill the joint spaces
what movements does the lateral ligament restrict?
posterior, lateral and inferior movement
what are the 3 accessory ligaments?
pterygomandibular raphe
stylomandibular ligament
sphenomandibular ligament
What does the articular disc do?
divides the joint into 2 compartments; lower - hinge, upper - slide
what are the 5 zones of the articular disc?
anterior extension
posterior extension
anterior band
intermediate zone
posterior band
what nerve innervates the TMJ?
Trigeminal nerve V3
what supplies blood to the tmj?
superficial temporal artery
maxillary artery
what is the result of an anterior disc displacement with reduction?
clicking jaw
Where would the condyle be to cause a dislocation of the TMJ?
anterior to the articular eminence
What is mastication?
chewing
What is the purpose of mastication?
preparation for swallowing
increase surface area for chemical digestion
release of chemicals for sense of taste
Where do masticatory movements take place?
TMJ
What are the 3 groups of muscles involved in mastication?
skull-mandible
mandible-hyoid
hyoid stabiliser
What are the muscles involved the skull-mandible group?
massester
temporalis
medial pterygoid
lateral pterygoid
what is the origin and insertion of the superficial masseter muscle?
origin: zygomatic arch/bone
insertion: angle/ramus of mandible
what is the action of the superficial masseter?
jaw elevation (closing)
minor protrusive
what is the origin and insertion of the deep masseter muscle?
origin: inner aspect of zygomatic arch
Insertion: angle/ramus of mandible
What is the action of the deep masseter muscle?
jaw elevation (closing)
What is the origin and insertion of the temporalis?
origin: inferior temporal line and fascia
insertion: coronoid process
What is the action of the temporalis?
(anterior fibres) jaw elevation
(posterior fibres) retrusion
what is the origin and insertion of the upper head part of lateral pterygoid?
origin: surface of greater wing of sphenoid
insertion: capsule and articular disc of TMJ
what is the origin and insertion of the lower head part of lateral pterygoid?
origin: lateral aspect of lateral pterygoid plate
insertion: pterygoid fovea below head of condyle
what is the action of the lateral pterygoid?
inferior head: pulls condyle forward, protrusion, assists opening, lateral excursion
superior head: restrusion and closing
what is the origin and insertion of the medial pterygoid?
origin: medial aspect of lateral plate and maxillary tuberosity
insertion: medial aspect of ramus/angle of mandible
what is the action of the medial pterygoid?
jaw elevation
protrusion and lateral excursions
What are the muscles involved the mandible-hyoid group?
geniohyoid
mylohyoid
digastric (anterior)
what is the origin of the geniohyoid?
inferior mental spine + inferior genial tubercle
what is the action of the geniohyoid?
(hyoid fixed): jaw opening and retrusion
(hyoid not fixed): raise and forward hyoid
what is the origin of the mylohyoid?
median raphe
what is the action of the mylohyoid?
(hyoid fixed): jaw opening
(hyoid not fixed): raise hyoid and FOM
What is the origin of the anterior belly of digastric?
digastric fossa
what is the action of the anterior belly of digastric?
(hyoid fixed): jaw opening
(hyoid not fixed): raise hyoid
what are the muscles involved in the hyoid stabilisers group?
infrahyoids (sternohyoid, omohyoid, thyrohyoid)
posterior digastric
stylohyoid
what other muscles are involved in mastication?
buccinator
obicularis oris
Detection of a mechanical stimuli through a peripheral receptor is called.
mechanoreception
Which type of reception gives us information about how things coming into contact with the body?
Exteroception
Which type of reception gives us information about our self, such as awareness of position?
Proprioception
What are the main oro-facial mechanoreceptors?
mucosa (and skin)
periodontal ligament
muscles
joint receptors
what do mucosa (and skin) mechanoreceptors tell us?
food texture
what do PDL mechanoreceptors tell us?
forces on teeth
what do muscle mechanoreceptors tell us?
muscle spindles tell us muscle length
What are the 2 classifications of mechanoreceptors?
physiological
anatomical
What is the receptive field?
The area/space where a stimulus will affect the receptor
Ruffini nerve endings are best found where in the oral cavity
PDL
Are the periodontal ligament mechanoreceptors afferent or efferent?
Afferent, Alpha beta axons
Where do the cell bodies of the periodontal ligament mechanoreceptors reside to?
V ganglion, then to the mesencephalic nucleus
Innervation density is at its highest, in which region of the periodontal ligament
higher at apex
Tooth must move around a what? to detect adequate stimulus?
fulcrum
Which region of the tooth would you expect to find slowly adapting, low threshold mechanoreceptors?
apically
Which region of the tooth would you expect to find rapidly adapting, high threshold mechanoreceptors?
Cervically
What are the 4 stages of the sensory pathway?
Sage 1: mechanoreception
Stage 2: Processing at first synapse
Stage 3: Processing in thalamus
Stage 4: conscious perception
What happens at stage 1 of the sensory pathway?
mechanoreceptors have been stimulated and propagation along primary afferent nerve
What happens at stage 2 of the sensory pathway?
sensory stimulus are processed at the first synapse at the trigeminal nuclei.
What happens at stage 3 of sensory pathway?
Sensory stimulus is processed in the thalamus.
What happens in stage 4 of sensory pathway?
Sensory stimulus is processed in the cerebral cortex for conscious perception.
At what stage does the sensory stimulus leave the peripheral nervous system and enter the central nervous system?
During stage 2, at its first synapse
What is proprioception?
A feedback system that allows us to be aware of our own movement
What are the 3 receptors involved in proprioception
Muscle spindles
Golgi tendon organs
joint receptors
What are extrafusal muscle fibres?
skeletal standard muscle fibres that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement.
What are intrafusal muscle fibres?
skeletal muscle fibres that serve as specialized sensory organs (proprioceptors) that detect the amount and rate of change in length of a muscle
how are afferents activated?
by stretch
What do secondary (flower-spray) nerve endings detect?
length of fibres
what do primary (annulo-spiral) nerve endings detect?
length of fibres and speed of change of length
what is the role of muscle spindles?
gives us information about muscle length
act to maintain muscle length
Where are the masticatory muscle spindles cell bodies located?
Trigeminal mesencephalic nucleus
Were do muscle spindle afferents synapse?
V motor nucleus
What happens when the muscle shortens?
Muscle contracted – shortens.
Gamma (y) motor neurones cause contraction of which muscle fibres?
Intrafusal fibres
What is the purpose of gamma motor neurones?
Maintain tension in spindle and maintain spindle afferent activity
Pacinian, Golgi and Ruffini are example of receptors located where?
the joint
What is occlusion?
The contact relationship of teeth or equivalent
What is articulation?
The dynamic relationships of teeth when in sliding contact
What is jaw relationship?
Positional relationship which the mandible bears to the maxilla
Vertical jaw relationship and dimensions – our teeth when they are slightly apart by few mm is best known as what position?
Rest/postural position
Vertical jaw relationship and dimensions – our teeth when they are together and fully interdigitated?
Intercuspal position (ICP)
Is the Intercuspal position stable or not and why?
Not a stable position because, if you were to lose a tooth then the positions would change.
Is the rest/postural position a stable position or not and why?
It is a stable position because, it is maintained by minimal muscle activity.
In a retruded contact position, describe the position of the condyle?
The condyle is retruded in the glenoid fossa.
What is the only muscle that will retract/move back/retrude the jaw?
Temporalis muscle
What is the occlusal vertical dimension (OVD)
the face height with the teeth in ICP
What two arbitrary points are used to measure the occlusal vertical dimension?
Nose and lower chin
What is the rest/postural vertical dimension (RVD)?
face height with the mandible in rest/postural position
what two arbitrary points are used to measure the rest/postural vertical dimension?
The nose and the mandible
What is used to measure OVD and RVD?
Willis gauge
What is the free way space?
gap between your teeth
The difference between teeth in rest position and ICP
how do you work out a persons free way space?
RVD-OVD=FWS
The restriction of the TMJ is governed by the positioning of the teeth. How does the positioning of the incisors restrict the mandibles movement?
At rest, the incisors will exhibit a slight overbite and overjet, which help restrict movement.
The restriction of the TMJ is governed by the positioning of the teeth. How does the positioning of the cusps restrict the mandibles movement?
The Intercuspal position.
A wide opening of the jaw exhibits what two movements?
Hinge and slide
What does the movement from the ICP to the RCP represent on the border movement graph?
It represents the ICP overcoming the overbite and overjet.
From RCP to the next point what does that represent?
This represents the pure hinge (small opening)
From RCP to maximum opening what movement would the condyle exhibit?
Hinge and slide
What muscle is responsible for moving the muscle forwards?
Lateral pterygoid
Is the working side the side to which the teeth move or the side away from which the teeth move?
the side to which the teeth move
what is canine guidance?
disocclusion of all the teeth by the contact of unilateral maxillary and mandibular canines only in lateral excursion movement
what is group function?
the anterior and posterior teeth have full contact on the working side but no contact on the non-working side
what is the position of the condyle on the non working side during excursion?
moves downwards, forwards over eminence, moves medially
what is the position of the condyle on the working side during excursion?
rotates around the vertical axis
lateral bodily movement
what is the balanced occlusion concept?
tooth contact during excursions at both working and non working sides
what is bennet movement?
a complex lateral movement or lateral shift of the mandible resulting from the movements of the condyles along the lateral inclines of the mandibular fossae during lateral jaw movement.
What is bennett angle?
The angle formed by the spatial coordinates of the condyles shifts and the sagittal plane
how long does the chewing cycle take?
0.5-1.2 secs
what are the phases of the chewing cycle?
opening
fast closing
slow closing
intercuspal phases
Would there be greater or lesser lateral movements during the chewing cycle if the food was brittle
Lesser lateral movements
Would there be greater or lesser lateral movements during the chewing cycle if the food was tougher?
Greater lateral movements
What is the sequence of muscle activation in the opening chewing cycle?
mylohyoid
digastric
lateral pterygoid
What is the sequence of muscle activation in the closing chewing cycle?
temporalis
masseter
medial pterygoid (lateral pterygoid also active)
What is a reflex?
Predictable response to a given stimulus
Why is jaw reflex important?
We may bite our tongue and the jaw reflex will help prevent us from ripping off the tongue.
What is the stages of jaw unloading reflex?
Stimulus: sudden closure following hard biting
Response: inactivation of jaw closing muscles and activation of jaw opening muscles
Result: Teeth do not crash together
Which centre sends a pattern of codes to the motor nucleus which activates specific nerves in a specific pattern which drives the masticatory movement?
Chewing centre
Which centre allows us to voluntarily control chewing pattern, through the motor nucleus?
Higher centres
What are the three type of reflexes?
Stretch reflex
Protective reflex
Unloading reflex – jaw
Which reflex system is the simplest form?
Stretch reflexes
Why are stretch reflex the simplest form?
Because it usually is mono-synaptic, meaning it has to synapse once
A knee jerk reflex is an example of what type of reflex?
Stretch reflex
What is reflex latency?
It is the time taken from the stimulus to the effector. That is usually the length of the pathway.
What is the minimum synaptic delay?
0.2 seconds per synapse.
Are synapses faster then action potentials
No
Muscle spindles act as what in the muscles?
Receptor (afferent, action potentials)
What are Temporomandibular Disorders (TMD)?
A group of conditions affecting the temporomandibular joint and/or the muscles of mastication
What percentage of people suffer with TMD?
10-15%
What age group is most commonly affected by TMD?
18-44
Is TMD more common in males or females?
Females
What factors make up the aetiology of TMD?
Biological
Psychological
Behavioural
What is important to look at when examaning for TMD?
Pain
Noises
Movement
Habits
Trauma
How can stress, anxiety and depression all increase the risk of TMD?
Can cause you to grind your teeth more
What are 3 co-morbidities that can contribute to TMD?
Fibromyalgia
Chronic pain
Psychological factors
What are the stages of a TMD examination?
Palpate the TMJ - lateral pole
Check for noises
Palpate the muscles (temporalis and masseter)
On opening check for deviation and the extent of opening
What else could you use to investigate TMD?
CBCT
MRI
TMD diagnosis is split into 2 groups, what are they?
Pain related TMDs
Intra-articular TMDs
Pain related TMDs are split into 2 groups, what are they?
Myalgia
Arthralgia
How does disc displacement with reduction present?
with clicking
How does disc displacement without reduction with limited opening present?
Characterised by a history of previous clicking which stops at the same time as the onset of restricted mouth movement
What is the TMD classification criteria?
Description
History
Examination
How does TMD- Myalgia description present?
Pain of muscle origin provoked when testing of the masticatory muscles
How does history of TMD-Myalgia present?
Pain in jaw, temple, infront of ear/in ear
AND
modified with jaw movement or function
What does examination of TMD-Myalgia look like?
pain in temporalis or masseter muscle
This pain is reciprocated when:
palpating temporalis or masseter
OR
maximum unassisted or assisted opening movements
What are the sub types of TMD-myalgia?
Local myalgia
Myofascial pain
Myofascial pain with Referral
How does local myalgia present?
pain is localised to the site of palpation
How does myofascial pain present?
pain extends beyond site of palpation but still within the boundaries of the muscle being palpated
how does myofascial pain with referral present?
The pain extends beyond the boundaries of the muscle being palpated
what is arthralgia?
pain of joint origin affected by jaw movement and replicated by testing of the TMJ
What is disc displacement with reduction?
in closed mouth position disc is in an anterior position relative to condylar head and disc reduces on mouth opening
What is disc replacement without reduction?
the disc is in an anterior position relative to the condylar head and does not reduce with opening - mouth will not open all the way
what is jaw lock
when the mouth does not open all the way
what is degenerative joint disease in the absence of pain termed?
osteoarthrosis
what is degenerative joint disease with arthralgia accompanying crepitus known as?
osteoarthritis
what is crepitus?
a popping, clicking or crackling sound in a joint.
what is subluxation
open lock
disc condyle complex lies anterior to articular eminence and cannot be returned to normal position without a manipulative manoeuvre
if a patient can manoeuvre the joint back into position what is this called?
subluxation
if a patient can’t manoeuvre the joint back into position and requires assistance of a clinician, what is this called?
luxation
Conservative management of TMD?
rest and relaxation
modify diet
avoid wide mouth opening
regular application of gentle heat - chronic conditions
regular application of cold pack - acute onset pain &/ or restricted mouth opening
Jaw excercises
NSAIDS
diazepam - helps muscle spasms
what does FLAT stand for?
Fear of pain
Low mood
Avoidance of functional activities
Thinking the worst
what is the purpose of a splint?
Splints are used to allow the muscles and ligaments in the mouth and jaw to relax, and as a result, the facial muscles are able to relieve some of the tension and tightness that may be caused clenching and grinding teeth.
what is the purpose of a splint?
Splints are used to allow the muscles and ligaments in the mouth and jaw to relax, and as a result, the facial muscles are able to relieve some of the tension and tightness that may be caused clenching and grinding teeth.
what is the aim of a michigan splint?
for maxillary arch
to create:
- canine guidance on lateral excursions
- anterior guidance on protrusion
- posterior disclusion on excursion
what is a tanner appliance?
similar to michigan splint but for mandibular arch
are stabilisation splints usually worn during the day or at night?
night time
how do you make a splint to help with TMD
record when condyle comes forward and jaw protrudes, using hard wax, soften it up and get patient to bite down with their jaw
Why should partial coverage splints not be used?
they can cause over eruption on the anterior teeth and a posterior open bite
why is the glenoid fossa thin?
so that the forces go through the teeth and not the joint
what guides the movement of the condyle?
articular eminence
what is canine guidance?
the load is on one tooth
what is group function?
the load is shared
mandibular moments are guided by what?
TMJ
Teeth
what type of articulator is often used in ortho for retainers?
hand held casts
what is the downside of hand held casts?
good for simple analysis but you need sufficient teeth
can only be analysed in iCP
What is good about a simple hinge articulator?
it relocates the teeth, so is better in a case with a lot of missing teeth
what is the downside of a simple hinge articulator
not a good device for simulating anatomical movement
what is an advantage of a plane line articulator?
the hinge is more anatomically correct and sturdy than the hand held casts and simple hinge articulator
what is the disadvantage of the plane line articulator?
the hinge is still arbitrary - not a simulator of movements
What is an advantage of the average value articulator?
has 2 hinges - we have 2 condyles
has a mounting plate - fixed relationship between the glenoid fossa and the jaw
what is an advantage of the semi adjustable articulators?
closest relationship to the real anatomy
what is required to set up an articulator
face bow/ear bow
what do rapidly adapting receptors give information about?
change and only fires when that change happens
