TMJ Flashcards
Where does the articulating disc of the TMJ lack a blood supply and sensory innervation
Its periphery
What is the articular disc’s function?
- Maximizes joint congruency to reduce contact pressure
- Adds stability to the joint
- Helps guide the mandibular condyle
The posterior region of the articular disc is [convex/concave] superiorly and [convex/concave] inferiorly.
convex; concave
What is the retrodiscal lamina attached to?
The extreme posterior region of the articular disc
The [superior/inferior] part of the retrodiscal lamina contains collagen rich fibers while the [superior/inferior] part contains elastin rich fibers.
inferior; superior
The intermediate region of the articular disc is ______ inferiorly and ______ superiorly.
Concave; flat
The anterior region of the articular dis is ______ inferiorly and _______ superiorly
Flat; concave
True or False:
In a healthy TMJ the articulating disc stays in the same place when the jaw opens.
False; the disc slides with the translating condyle
What is protrusion an important component of? retrusion?
Opening the mouth maximally; closing the widely opened and protruded mouth
Technical name for overbite; technical name for underbite
Retronagthic jaw; prognathic jaw
Movement that occurs and a side to side motion
Lateral excursion
If you have lateral excursion to the left, then on the right side [protrusion/retrusion] occurs, and [protrusion/retrusion] occurs on the left side.
protrusion; retrusion
To have typical mastication, the jaw must open_____. How much can the average adult mouth open?
Two knuckles worth (18mm); three knuckles (50 mm)
How do the disc and mandibular condyle move during general translational movement? during protrusion? during retrusion?
They slide together; anteriorly together and follow the downward slope of the articular eminence; posteriorly together and follow the upward slope of the articular eminance
How does the mandible move during protrusion and retrusion?
anteriorly and slightly downward; posteriorly and slightly upward
What occurs during the early phase of depression?
Primarily rotation; condyle rolls posteriorly within the concave inferior surface of the disc
What ligament is stretched during the early phase of depression?
Oblique portion of the lateral ligament; check reign ligament - once it is taut, second phase begins
Primary ligament reinforcing the TMJ; stabilizes lateral side of capsule; typically described as a combo of horizontal and oblique fibers
Lateral (TM) ligament
What occurs during the late phase of depression?
Primarily translation; condyle and disc slide together forward and inferior
Where is the axis of rotation in the early phase of depression? during the late phase?
Migrates within the vicinity of the condyles; shifts inferiorly, usually below the neck of the mandible
Where is tension increased during the late phase of depression?
The elastic superiorly retrodiscal lamina
What does tension in the superior retrodiscal lamina initiate?
the early translational phase of closing the jaw
What happens during bilateral contraction of the masseter muscle? unilateral contraction?
Elevation and protrusion; ipsilateral deviation
What happens during bilateral contraction of the temporal muscle? unilateral contraction?
elevation and retrusion; ipsilateral deviation (but overall work is to bring it back to neutral
What happens during bilateral contraction of the medial pterygoid muscle? unilateral contraction?
Elevation and protrusion; contralateral deviation
What happens during bilateral contraction of the lateral pterygoid muscle? unilateral contraction?
Strong protrusion (inferior head is the primary depressor of the mandible while superior head helps control the position of the disc and joint during elevation); contralateral deviation
What muscles force-couple to create rotation of the mandible around its axis of rotation to create a CONTROLLED movement to open the mouth?
Lateral pterygoid and the supra hyoid group of muscles
True or false:
The superiorly head of the lateral pterygoid is active eccentrically while closing the mouth.
True
What are symptoms of TMDs?
- Muscle or joint pain during movement
- Joint sounds “popping”
- Reduced molar bite forces
- Limited range in mouth opening
- Headaches
- Joint locking
- Referred pain to the face and scalp
What are causes of TMDs?
- Stress
- Oral habits
- Asymmetric muscle activity
- Sleep bruxism (grinding of teeth at night)
- Chronic forward head posture
- Abnormal anatomy
- Trauma
- Retrognathic or prognathic jaw
What does spheno-basilar flexion lead to?
Widening medial to lateral, shortening of AP; creates a wide pallet (widening of the “freeway space”)
What does spheno-basilar extension lead to?
Elongating AP and raising the roof of the mouth; tall and narrow pallet (raising of “freeway space”)
What is freeway space important for?
Mastication and phonation
