TMJ Flashcards
What bones make up the TMJ?
Articulation of mandibular condyle and mandibular fossa of temporal bone
What is the purpose of the articular disc at the TMJ?
- Disc is biconcave allow convex surfaces to remain congruent throughout ROM
- Increases stability
- Minimizes loss of mobility
- Reduces Friction
- Decreases biomechanical stress
What kind of joint is the inferior TMJ?
Simple hinge joint
What kind of joint is the superior TMJ?
Functions as a gliding joint
What attaches to the articular disc?
- Medial/lateral poles of condyle
- Anteriorly - Joint capsule and lateral pterygoid
- Posteriorly - bilaminar retrodiscal pad
What does the superior lamina assist the disc with?
Assists the disc in translating anteriorly with mandibular depression
What does the inferior lamina do?
Limits forward translation
What is the make up of the joint capsule of the TMJ? Where is it strong? Where is it weak? How does those strength and weaknesses influence dislocations?
- Firm medially/laterally
- Thin and loose anterior/posterior
- Allows for ant translation when mouth is open
- Predisposes TMJ to ant dislocation due to lack of strength of ant capsule and the incongruence of articular surfaces
What are the ligaments of the TMJ? What purpose do they serve?
- Lateral lig - stabilize lateral portion of capsule
- Stylomandibular lig - weakest of 3
- Sphenomandibular lig - swinging hinge that suspends manidle
What is the normal resting position of the TMJ?
- Lips closed and teeth several mm a part
- Maintained by temporalis muscle
]What are the different movements osteokinematically?
- Depression/elevation
- Protrusion/Retrusion
- Left & Right lateral excursion
How and at which part of the joint does the first part of mouth opening occur?
Roll posterior in lower joint
How and at which part of the joint does the second part of mouth opening occur?
Glide ant in upper joint
How and at which part of the joint does the first part of mouth closing occur?
Glide post in upper joint
How and at which part of the joint does the second part of closing opening occur?
Roll posterior in lower joint
What happens with the articular disc during mouth opening and closing?
50% rolling in lower joint = disc remains stationary
50% gliding in upper joint = disc slides along with condyle
How and at which part of the joint does protraction and retraction occur?
Protraction - anterior/slight inferior glide of condyle/disc
Retraction - post/slight superior glide of condylde/disc
What happens with the articular disc during protraction and retraction?
Same as condyle
What occurs on the ipsilateral side during lateral excursion?
Glide posterior (retrude)
What occurs on the contralateral side during lateral excursion?
Glide anterior (protrude)
What muscles and forces act on the TMJ during opening?
- Primarily gravity
- Digastric
- Suprahyoids
- Inferior lateral pterygoid
What muscles and forces act on the TMJ during Closing?
- Temporalis
- Masseter
- Medial pterygoids
- Control of disc via superior lateral pterygoids
What muscles and forces act on the TMJ during Protrusion?
- Superior masseters
- Medial Pterygoids
- Lateral Pterygoids
What muscles and forces act on the TMJ during Retrusion?
- Post. Fibers: Temporalis
- Deep Fibers: Masseter
- Ant. Digastric (some help)
What muscles and forces act on the TMJ during Lateral excursion?
- Contralateral Med/Lat Pterygoid (pull condyle forward)
- Ipsilateral Temporalis (pull condyle posterior)
What is the normal ROM for the different motions of the TMJ?
- Opening: 35-50 mm
-(25-35 mm: needed for everyday activity)
-Functional screen of mandibular depression
2 knuckles=functional
3 knuckles=normal - Lateral deviation: 10-15mm
- Protrusion: 3-9 mm
- Retrusion: about 3 mm
What is TMD?
- Broad/vague term used to describe dysfunctions associated with TMJ
- Includes pain, popping, reduced bite force, reduced ROM with mouth opening, headaches, tinnitus trigger points
What factors are associated with TMD?
- Stress/emotional disturbance
- Daily oral parafunctional habits
- Asymmetric muscle activity
- Sleep bruxism
- Chronic forward head posture
- C-spine pathology
- Sensitization of the CNS
What is deviation of TMJ?
Motion that produces “S” curve with depression or protrusion
What is deflection of TMJ?
Motion that produces “C” curve with depression or protrusion
Describe what is occurring during mouth opening/closing when there is a disc displacement with reduction? Why is there a click? What is a reciprocal click?
- Full opening
- Disc sits anterior
- Reciprocal Click: opening click as disc relocates, closing click as disc gets squeezed abnormally & subluxes anteriorly
Describe what is occurring during mouth opening/closing when there is a disc displacement without reduction? Why is there not a click?
- Closed lock/no clicking
- Partial anterior displacement or dislocation
- Mandibular condyle unable to pass over the posterior border of the disc with opening (disc remains bunched anterior to the mandibular condyle)
- Disc does not relocate: Blocks translation and limits motion
- Deviation toward painful side during opening
How does posture and the cervical spine impact the TMJ?
- may affect tension in cervical muscles which can influence the function of the mandible
- Forward head = posterior/superior position -> greater stress on TMJ, lateral pterygoid contracture, anterior disk displacement
