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
What are the consequences of not taking ICP into account ?
high restorations
will fail
leads to TMJ pain, Pain, sorness
restorations will fracture
When are new contacts (restorations) most table ?
fit into marginal ridge or fossa
Why are guidance teeth important ?
come into fucntional contact a lot throughout the day
How do you identify anterior guidance teeth ?
ask the patient to protrude mandible from ICP
teeth that are in contact are anterior guidance
What is incisal guidance ?
incisors tear food
then incisors aid protrusion of the mandible to ICP after chewing
What does the amount of incisal guidance depend on ?
overlap of upper and posterior teeth
How is the mandible guided away and to the ICP ?
by guidance teeth slopes
What happens with a class III relationship with incisal guidance ?
the canines and premolars provide guidance
What is lateral excursive guidance ?
guidance that occurs on the working side
What are the 2 types of lateral excursive guidance ?
canine guidance
group function
What is canine guidance ?
excursion to the WS results in WS canines being in contact only
teeth on NWS are discluded
What is group function ?
excursion to the WS results in contact between more than 1 pair of WS teeeth
discussion on the NWS
Which type of lateral excursive guidance is most common ?
canine guidance
In which patients is group function common in ?
elderly patients
due to tooth wear, tooth loss
What must be considered when restoring guidance teeth ?
restored teeth are weak
it is unreasonable to let restored guidance teeth provide all the guidance
shape guidance if the restored tooth is sole guidance tooth
do not interfere with guidance unless trying to protect a heavily restored tooth
What should be considered when restoring guidance teeth ?
dont just restore the ICP contact areas
restore the entire contact concave area
What shape should guidance surfaces be ?
concave
if convex- too much material is present which can become overloaded with axial forces leading to interferences
What is problematic about crown materials and guidance ?
tooth preparations must reproduce guidance whilst being sufficient for crown materials - bulbous
if too bulky palatal surfaces take a lot of masticatroy load
can lead to tenderness of Tooth and drifting
Describe a class I lever system ?
effort fulcrum load
produces the largest forces
Describe a class II lever system ?
effort load fulcrum
results in intermediate forces
Describe a class III lever system ?
fulcrum effort load
least force is produced
What does the effort refer to in the dental setting ?
work of temporalis and masseter
Which lever class system is the best dentally ?
class III results in the least forces
What is the relationship between fulcrum and load and force ?
the further away the fulcrum is from the load the smaller the forces
What is the fulcrum in the dental setting ?
condyle
What is mutually protected occlusion ?
Upon closing to ICP the posterior teeth take forces down their longitudinal axes
Upon lateral excursive guidance the posterior teeth disclude and the anterior teeth take forces
What is centric relation?
position when the condyles are in most posterior superior position in the glenoid fossae
What is CR dictated by ?
the TMJ only
Can CR be reproduced in a diseased mandible ?
no
Describe the positions of the teeth, discs and muscles in CR ?
CR is independent of tooth contact
muscles are most relaxed
discs are interposed
To which position can you move to from the RCP ?
from the RCP you can move into the ICP by sliding anteriorly and superiority
What are deflective contacts ?
deflective contacts are contacts that deflect the mandible from one path of closure to another
Give an example of a deflective contact ?
RCP-ICP slide
What can be detrimental in the RCP-ICP slide ?
when the mandible is thrust forward into ICP
lower incisors impinge heavily on upper incisors
non axial loading that leads to localised wear and drifting of maxillary incisors
What is a working side interference ?
heavy or early contact of teeth when mandible is moved to working side
What is a non working side interference ?
occlusal contact is made on the side the mandible is moving away from
potentially more detrimental as the forces are oblique
What is a protrusive interfernce ?
contact between incisors
What are functional cusps ?
they maintain tooth height
they bite into the fossa of the opposing tooth
buccal cusps of the lowers
palatal cusps of the uppers
What are guiding cusps ?
they dont come into contact help maintain food bolus on occlusal table guide into ICP lingual of the lowers buccal cusps of the uppers
`What are marginal ridges ?
raised mesial and distal aspects of the tooth
they provide structural integrity to the tooth ]#deflect food away to the occlusal table
What are the consequences of leaving a tooth out of occlusion ?
it can form a premature contact
What are the 3 types of articulators?
simple hinge
semi adjustbale
fully adjustable
What do simple hinge articulators do ?
they mimic ICP
limited simulation of jaw movement
limited alteration
What are semi adjustable articulators ?
they adequatrly stimulate jaw movement
lower member has condylar
What does ARCON mean ?
Articulating condyle
What does it mean if an articulator is ARCON ?
the articulating condyle is attached to the lower member as would be in the body
What is a non-arcon articulator ?
condyalr elements attached to the upper member
What is the condylar guidance angle ?
25 degrees
What is the progressive side shift ?
the linear movement that moves the condyle downwards and forwards after the immediate side shift
What are arcon artiulators used for ?
occlusal analysis and crown and bridgework as the upper member can be removed
What is the intercondylar distance ?
110 mm
Which articulators are preferred for denture work ?
non arcon
members are hinged and remian hinged
What do non arcon articulators rely on to guide lateral excusrive movement ?
3 walls-
superior
medial
rear
Describe the movement on the NWS ?
progressive side shift
movement is downwards, forwards, medially
bennet angle and condylar angle
Describe the movement of the WS ?
rotational
bennet movement
immediate side shift
What is the bennet angle ?
the angle between the sagittal plane and the NWS condyle in a lateral excursive movement
What is the condylar guidance angle ?
angle between the frankfurt plane and the condylar path of the NWS condyle
angle of downward movement of NWS condyle and horizontal plane
What is the immediate side shift ?
the initial body movement of the mandible on the WS i
lateral movement that occurs on the WS before forward movement of the NWS condyle
What is the progressive side shift ?
the lateral translation that continues after forward movement of the NWS condyke
creates the bennet angle (angle between the sagttal plane and the NWS condyle)
