Occlusion 1 Flashcards
What is the TMJ
a joint between the condylar head of the mandible and the mandibular fossa of the temporal bone
What type of joint is the TMJ
synovial
condylar hinge type joint
What type of surfaces does the TMJ have
fibrocartilaginous surfaces and an articular disc that divides the joint into 2 halves
What muscle is attached to the articular disc
lateral pterygoid
What is the mandibular fossa
an indentation in the cranial base
What is the capsule
a fibrous membrane that surrounds the joint and attaches to the articular eminence, articular disc and the neck of the mandibular condyle
What is the articular disc
it is a fibrous extension of the capsule that runs between 2 articular surfaces of the TMJ
the disc articulates with the mandibular fossa and the condyle of the mandible below
disc divided the joint into 2 sections each with its own synovial membranes and there are synovial spaces and membranes above and below
What is the disc attached to medially, anteriorly, posteriorly and laterally
medially - condyle
laterally - lateral ligaments
anteriorly - joint capsule and superior head of the lateral pterygoid
posteriorly - mandibular fossa (referred to as the retrodiscal tissue)
Why is the retrodiscal tissue more responsible for pain
it is more vascular
What are the function of the muscles of mastication
involved in depression, elevation, and lateral movements of the mandible
What is the function of the supra hyoid muscles
elevate the hyoid bone or depress the mandible
What is the function of the temporalis
elevates and retracts the mandible and assists in rotation
What is the function of the lateral pterygoid
positions disc in closing (superior - SLP)
protrudes and depresses the mandible and causes lateral movement (inferior - ILP)
What is the function of the medial pterygoid
elevates the mandible
lateral movement and protrusion
What is the function of the masseter (SMA)
elevates and protracts the mandible
assists in lateral movement
What are the mandibular movements
rotation
translation (lateral translation is grouped under this too)
What is rotation
small amount of mouth opening (up to 20mm)
What happens in rotation
the condyle and disc remain within the articular fossa
no downwards or forwards movement
aka hinge movement
What is hinge movement
it is the rotation of the condylar heads around an imaginary horizontal line through the rotational centre of the condyles
What is the name given to the imaginary line in hinge movement
terminal hinge axis
What does a face bow record
the terminal hinge axis
the distance between condyles
What does the face bow allow
it allows us to ensure that we get as accurate a relationship as possible to that in the mouth when mounting the maxillary casts
What happens in translation of the condyle
the lateral pterygoid contracts
the articular disc and condyle begin to move
the condyle travels downwards and forwards along the incline of the articular eminence
may also travel laterally (laterotrusive movement)
What is Posselt’s envelope
it is the extremes of mandibular movmenet
it shows the border movements of the mandible in the SAGITTAL PLANE
What is the order of the envelope starting with ICP and going clockwise
ICP E Pr T R RCP
What is ICP
intercuspal position
What is E
edge to edge
What is Pr
protrusion
What is T
maximum opening
What is R
retruded axis position
What is RCP
retruded contact position
What is ICP
it is the tooth position regardless of the condylar position the comfortable bite best fit of the teeth maximum interdigitation of the teeth can be called centric occlusion
What is edge to edge
it is a tooth position
the teeth slide forward from ICP guiding on palatal surfaces of anterior teeth
incised edges of upper and lower incisors touch
What is protrusion
the condyles move forwards and downwards on the articular eminence
only incisors and maybe canines touch
there should be no posterior tooth contacts
eventually there should be no tooth contacts
What is T
no tooth contacts
mouth wide open
full translation of the condyle over the articular eminence
What is retruded axis position
no tooth contacts
most superior anterior position of the condylar head in the fossa
terminal hinge axis
What is the retruded contact position
first tooth contact when the mandible is in the retruded axis position
ICP is approximately 1mm anterior to the RCP in 90% of the population
Are Rcp and ICP coincident
no
mandible slides forward to achieve ICP
What is the working side in lateral translation
the side that the mandible is going to
What is the non working side
the side that the mandible is going away from
What is lateral translation of the mandible known as
Bennet movement
What is lateral movement a result of
contraction of the lateral pterygoid on one side
What is Bennet Angle
The path of the nonworking condyle in the horizontal plane during lateral excursion
What is bennet movement
The bodily lateral movement or lateral shift of the mandible resulting from the movements of the condyles along the lateral inclines of the mandibular fossae in lateral jaw movements
