Theme 3- Occlusion Flashcards
What is meant by occlusion ?
The relationship of opposing teeth in contact
Movement of opposing teeth during mastication
What does the CNS control ?
Masticatory muscles
TMJ
occlusion
What is the TMJ ?
a synovial joint that allows for rotational and translational movements of the mandible
What are the articulating surfaces of the TMJ ?
Condyle of the mandible
Glenoid fossa of temporal bone
What is the structure of the TMJ ?
fibrous capsule surrounds the TMJ
Synovial fluid
Articulating discs separates the condyle and the glenoid fossa and into superior and inferior compartments
What is the articulating disc divided into ?
anterior band
intermediate zone
Posterior band
What is the function of TMJ ligaments ?
to prevent undesirable movements
What is rotation of the mandible ?
condyle moves around a plane
What is rotation of the mandible mediated by ?
TMJ
What are the 3 planes that TMJ rotation occurs around
intercondylar
vertical - left and right turning
sagittal - up and down
What is translation of the mandible ?
bodily movement of the mandible
What are the 2 directions of translation of the mandible ?
anterior/posterior
laterally
What is the ICP ?
intercuspal position
relationship of maximum interdigitation between the mandibular and maxillary teeth
affected by occlusal interferences
What is the RCP ?
retruded contact position
position of the mandible when the posterior teeth make initial contact on the retruded arc of closure
muscles have to overcome this
What is centric relation ?
condyles are in most superior position in the glenoid fossa
What is the working side ?
the side that the mandible moves toward during lateral excursion
this side exhibits rotation of the mandible around the intercondylar axis
What is the non working side ?
the side which the mandible moves away from
condyle exhibits orbiting movement
Describe posselts envelope of border movement ?
Teeth in ICP
Retrude to RCP
Open mandible with rotation
Open more with translation to max opening
protrude the mandible to P - max protrusion
slide back to edge to edge position
back to ICP
What are the muscles of mastication ?
lateral pterygoid
medial pterygoid
masseter
Temporalis
What are the attachments of masseter ?
From the zygomatic arch to the ramus of the mandible
What are the attachments of temporalis ?
From the temporal fossa to the coronoid process
What are the attachments of lateral pterygoid ?
Superior head From the GWS to the pterygoid fovea on the mandible
Inferior head from the Lateral aspect of the lateral pterygoid plate to pterygoid fovea
What are the attachments of medial pterygoid ?
Superficial from the maxilary tuberosity to the ramus of the mandible
Deep from the medial aspect of the lateral pterygoid plate to the ramus of the mandible
Which muscles are used for closing ?
temporalis
medial pterygoid
masseter
all are elevators of the mandible
Which muscles are used for depressing the mandible ?
Inferior head of lateral pterygoid
Where are masticatory forces directed ?
down the long axes of the teeth
How are masticatory forces and movement regulated ?
with proprioceptive input from the PDL, pulp, TMJ, muscles and ligaments
Why can the PDL regulate forces and movement ?
it is extremely senstive
What does the neuromuscular system do ?
Regulates occlusal forces
makes the mouth go back to ICP after swallowing
Is ICP guaranteed ?
no
some people have anterior/posterior open bites
How is ICP developed ?
premature contacts in the form of erupting teeth are subject to greater occlusal forces
leads to orthodontic realignment and ICpP
What determines ICP ?
it is tooth detemrined
lack of Teeth- no ICp
Is ICP stable in the long term ?
no
What can change the ICP ?
tooth wear and restorations
What can lead to the collapse of ICP ?
Loss of vertical dimension of teeth- due to wear drifting of teeth periodontal disease class II/III skeletal relationships scissor bite
What is crossbite ?
upper arch is wider the lower arch
buccal cusps of lower teeth fit into central fossa of the upper teeth
palatal cups of the upper teeth fir onto central fossa of lower teeth
What is buccal crossbite ?
lower jaw wider
buccal cusps of the upper teeth fit into central fossa of lower teeth
lingual cusps of the lower teeth fit into central fossa of upper
What is scissor bite ?
upper jaw is significantly wider so teeth are not in contact
Why is the ICP important?
restorations should conform to and accomodate the ICP