3/13: Optimal Functional Occlusion Flashcards
What are the factors that contribute to the baseline for evaluating a patient’s occlusion?
Teeth
TMJ
Musculature
If a patient has an orthodontically ideal angles class I occlusion, this does/does not mean that the patient has optimal occlusal contacts, optimal condyle/mandibular position, and ideal/optimal contact in exursive moments
Does not
Someone with a class II or class III occlusion although not orthodontically ideal, may have _________ occlusion
Functional
Patients may have a less than ideal occlusion, however, it may still be a ________ occlusion or a _________________ occlusion
Functionally acceptable; physiologically acceptable
If treatment is rendered, what do you consider
The optimal position for the joints, muscles and teeth (CR)
When are the TM joints in optimum, orthopedically stable joint position?
When the mandible is in centric relation
What is centric relation?
Position of the condyles in relation to the disc and fossa
What is centric relation defined as?
When the condyles are in the most anterosuperior position in the glenoid fossa
What does centric relation refer to?
The joints and does not involve teeth
Bow does the mandible arc up?
Freely up and down along the terminal hinge axis
What is deflection?
Teeth cannot contact
Why is CR the ideal position?
Musculature in centric relation
TMJs in centric relation
How do the muscle function in CR?
Harmoniously
What is the joint like in centric relation?
Stable because the muscles attached to the joint prevent dislocation of the articular surfaces
What muscles stabilize the TMJ?
Masseter and the medial pterygoids
What does contraction of the muscles that stabilize the TMJ result in?
Antero-superior vector of force (stability)
What muscles are most relaxed in CR?
Lateral pterygoid
What do the condyles rest against in centric relation?
Posterior slope of the articular eminence (thickest bone) therefore can tolerate higher stresses
What do condyles rest against in centric relation?
Intermediate zone of the disc (non-innervated and avascular zone) therefore higher stresses can be toelrated
What was CR called in the past?
The most retruded position of the mandible
What are tissues like in the most retruded position?
The retrodiscal tissues are innervated and would not tolerate stresses
What is the posterior wall like in the most retruded position?
Very thin
How do muscles function in centric relation?
Harmoniously
What position are the TMJs in in centric relation?
Optimal, orthopedically stable joint position
What can the TMJ withstand?
The TMJ is stable even when heavy loads/forces are applied
What do we restore in centric relation?
- completely edentulous patient
- partially edentulous patients when there are few teeth remaining that there is not a stable MIP
- dentate patients who are going to receive extensive restorations which will alter their occlusion completely
What do you use to deprogram the muscles of mastication?
Anterior deprogrammer
What three things are necessary for optimal functional occlusion?
- The TMJ
- The teeth
- The excursive movements
What are teeth relations in optimal functional occlusion?
- stationary position
- during excursive movements
What is the most desirable position of the posterior teeth?
Multiple, even, bilateral. and simultaneous occlusal contacts with the mandible in the CR position are the most desirable
Where are posterior teeth loaded?
Mainly along the long axis of the tooth (axial loading)
What happens when more teeth contact?
More stress is distributed throughout the arch
What happens when all posterior teeth contact evenly?
Distributed the stress over all the teeth and does not concentrate it on one tooth causing harm
What happens when the teeth are bilateral?
For stability; if tooth contacts occur only on the right side and not the left, then the mandible will pivot around this right side contact and place increased pressure on the left TMJ causing problems
What happens when the teeth have simultaneous contact?
All the contacts occur at the same time on both sides of the arch and on all the posterior teeth
What does it mean when the teeth are axially loaded?
Through the long axis of the tooth
What forces are not well accepted?
Lateral forces on teeth
When can heavier stresses be applied?
Through axial loading
What teeth should have lighter occlusal contacts and when?
Anterior when posterior teeth are in occlusion
Why can anterior teeth not be able to withstand high loads?
When loaded axially
What is canine guidance?
When the mandible moves laterally, the canines on the working side guide the movement, causing all other teeth to disclude
What is anterior guidance?
In protrusive movement, the anterior teeth should disclude the posterior teeth
What do the canines, central and lateral incisors do when the mandible moves in protrusion?
Disclude
What are contacts between the posterior teeth during extrusive movements considered?
Interferences
- can create damaging effects on T teeth and periodontium
The more anterior (away from the fulcrum), the resistance (load) occurs, the ________ the impact (magnitude)
LEsser
What tooth has the longest root and best bone support?
canine (canine eminence)
What is optimal functional occlusion also referred to as?
Mutually protected occlusion
Multiple, even, bilateral, simultaneous occlusal contacts of the posterior teeth in MIP with the mandible is _______ position. _____ and ____ are coincident
MIP; MIP and CR
What teeth exhibit lighter occlusal contacts in MIP
Anterior
How are posterior teeth loaded in MIP?
Axially
What guidance occurs in excursive movements?
Canine/anterior guidance
What teeth withstand majority of the load in MIP?
Posterior teeth, protecting the anterior teeth from high loads
How do anterior teeth proctect the posterior teeth from off-axis loading?
The anterior teeth disclude the posterior teeth in excursive movements
What teeth tolerate axial loading well?
Posterior teeth, so they protect anterior teeth which are not axially loaded in MIP
What can anterior teeth tolerate?
Lateral forces in excursive movements (off-axial loading) since they are further away from the fulcrum and the loads are less
What are occlusal schemes/philosophies in excursive movements?
- canine guidance - anterior guidance
- group function
- balanced occlusion
What is the mandible guided by when it moves laterally?
The outer inclines of the mandibular buccal cusps sliding along the inner inclines of the buccal cusps of the maxillary posterior teeth
What is the most desirable group function consist of?
The canines, premolars and MB cusp of the first molar
The more posterior the contact, the _______ the force
Greater- closer to the source of power; the more destructive the forces
What are the buccal cusps like on the WS?
Mandibular teeth guide along the inner inclines of the maxillary teeth, as far posteriorly as the first molar (MB cusp)
Where are there no contacts?
On the NWS
________ function is acceptable but not ideal
Group function
When is group function the only option?
For patients who:
- have no anterior vertical overlap
e.g. anterior open bite
- very large anterior horizontal overlap
e.g. class II div I
- have a reverse overlap
e.g. class III
What is balanced occlusion?
Simultaneous contacts on both sides (working and non working) during lateral excursive movements (working side contacts and balancing side contacts)
When is there contact during balanced occlusion?
Contacts between the posterior and anterior teeth during protrusive movement
What happens during balanced occlusion if the mandible moves to the right?
On the right side (WS): outer inclines of mandibular buccal cusps contact inner inclines of maxillary buccal cusps and at the same time
On the left side (NWS): inner inclines of mandibular buccal cusps contact inner inclines of maxillary lingual cusps
What happens during balanced occlusion when in protrusion?
There are contacts between posterior and anterior teeth
What happens to posterior teeth in balanced occlusion?
Mesial inclines of mandibular cusps occlude with distal inclines of maxillary cusps
When is balanced occlsuion not acceptable/ideal?
For dentate patients because it promotes tooth wear
What kind of contacts are destructive and must be avoided?
Non-working side contacts
What kind of occlusion is an acceptable form for complete dentures?
Balanced occlusion
