10. Flashcards
What functions does the masseter muscle have? (3)
- elevation of the mandible
- chewing
- protruding
What functions does the temporalis muscle have? (2)
- mandible elevation
- mandible follows the direction of the portion of fibers contracting
What functions does the pyergoideus medialis muscle have? (3)
- elevation
- protrusion
- mediotrusion
What are the two divisions of the pyergoideus lateralis?
- inferior
- superior
Function of the inferior lateral pterygoid?
- lateral movements
- lowering of mandible
- protrusion
Function of the superior lateral pterygoid?
- articular stability of TMJ
- activates when forcing the ICP position
Function of the digastricus?
- depression of the mandible
- opening
- swallowing
What muscles are involved with protrusion? (2)
Lateral pterygoid assisted with medial pterygoid
What muscles are involved with retraction? (4)
- posterior fibers of temporalis
- deep part of masseter
- geniohyoid
- digastric
What muscles are involved with elevation? (3)
- temporalis
- masseter
- medial pterygoid
What muscles are involved with depression? (3)
- digastric
- geniohyoid
- mylohyoid
How much are teeth separated during mouth opening without condyles moving from the fossae?
20-25mm
What occurs when the mouth opens wider than 20-25mm? (3)
- Ligaments are fully extended
- Condyles move downward and forward out of the
fossae - It is called the second arc of opening
What is a predisposing factor?
Increase the risk of appearance of the disorder
What is a precipitating factor?
They activate the process
What is a perpetuating factor?
They prolong the situation
What are the five principal etiological factors in the apparition of TMD?
- Occlusal condition
- Trauma over structures of the masticatory system
- stress
- deep pain input
- parafunctional activities
What is the optimum occlusion?
MI & condyles are in their most superoanterior position resting over the posterior slopes of the articular eminences with the discs properly inserted
What is a prematurity? (2)
- happen at MI/CR
- avoids ICP in a retruded position
What is an interference? (3)
- undesirable contact during eccentric movements
What is the ideal articulation for a dentate patient?
Mutually protected articulation
What is the worst intereference?
on the NWS
Define protrusion (2)
- Mandible moves forward the ICP
- predominant protrusive contact is between the anterior teeth
What is a static occlusal factor?
predisposing occlusal factor
What can affect the occlusal condition? (5)
- Static occlusal factors
- Orthopedical instability of the jaw
- Acute changes in the occlusion
- chronic changes in the occlusion
- types of occlusal interferences
What are the static occlusal factors?
– Musculoskeletal anterior open bite – Displacement (deviation) from CR to MI of more tan 2mm – Absence of anterior guidance: interferences. – Overjet greater than 4mm – 5 teeth or more missing.
How does orthopedical instability of the jaw affect occlusal condition? (3)
– Dynamic oclusal factors, like the prematurities,
forces a sliding to reach the
InterCuspalPosition.
– Overexertion of the external pterygoid and
intracapsular disorder of the TMJ, specially
when subject to higher forces (ex: Bruxism)
– Discrepancies of 2 to 3mm are one of the
principal factors involved in a TMD
How does acute changes in the occlusion (interferences) affect occlusal condition? (2)
- Increase the muscular tone and it´s
hyperactivity that can lead to symptoms
of the elevator muscles due to aprotective co-contraction
– Muscles develop a new way of avoiding the
interferences
– The patient generally adapts to the new
situation.
– If it becomes a chronical occlusal
situation associated to the stress factor,
a parafunctional activity can appear
– Sleep bruxism is more associated to the
stress and sleep alterations than with the
apparition of acute interferences
How do chronic changes in the occlusion affect occlusal condition ? (4)
– Occlusal interferences due to the migration of teeth adjacent/antagonist to an edentulous ridge – The apparition of a small interference, mantained over the time, can also be converted into a chronical one. – In those cases, there is a failure of the proprioceptive defensive system that was used to avoid the interference – In those situations, the mandible does not try to avoid the interferences, but unconsciously grinds the area creating the subsequent wear
Adaptation of chronical changes in the occlusion?
The musculatory system tend to adapt to avoid the nocive contacts (adaptative reflex). More frequent when not associated to stress
TMD of chronical changes in the occlusion?
A parafunction is developed by the patient for an
increase of emotional factors (stress), that leads to
the typical muscular hyperactivity associated to
bruxism
What are the types of occlusal interferences? (3)
Prematurites causing more than 2mm discrepancies
-– The factor that is mostly associated to TMD, it
creates an overloading of both pterygoid
muscles or one of them
– Pain during the palpation and functional
manipulation of the inferior external pterygoid
muscle
Make cards for slide 23-24
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What are the different types of trauma over the masticatory system?
- Macro trauma
- Microtrauma
What is defined macrotrauma of the masticatory system? (3)
- intense and sudden force
- Intracapsular disorders
- Elongation of the ligaments and disc displacement
What is an example of macrotrauma of the masticatory system? (2)
– Accident, practicing sports, a fight, etc…
– Iatrogenic trauma: intubation during general
anesthesia, complex tooth extraction,…
What is defined as microtrauma of the masticatory system? (3)
- Small repetitive forces over the same structures during a
long period of time. - Ex; grinding teeth, bruxism
- If associated to orthopedical instability in the IPC; high
risk of elongation of the ligaments
