Lecture 9- Optimal Functional Occlusion Flashcards
what do we need to know for optimal function occlusion
- optimal occlusion in a stationary position: position of teeth, TMJ, muscles
- optimal occlusion during excursive movements of the mandible
- occlusal philosophies during excursive movements such as canine guidance, group function, balanced occlusion
what is the baseline for evaluating the patients occlusion
-teeth
-TMJ
- musculature
even though a patient may have an othodontically ideal angles class I occlusion what does this not mean
the patient has optimal occlusal contacts, optimal condyle/mandibular position, and ideal/optimal contacts in excursive movements
patients may have a less than ideal occlusion however it may still be a ____ or _____
functionally acceptable occlusion or a physiologically acceptable occlusion
to determine if occlusal treatment is required what should you assess
-the masticatory system for evidence of pathology - tooth wear, tooth mobility, TMJ dysfunction, muscle dysfunction
-adaptive capacity of the patient
- if treatment is rendered what is the optimal position for the joints, muscles and teeth
when are the TM joints in an optimum orthopedically stable joint position_____
when the mandible is in CR
what is centric relation used to define
a position in the condyles in relation to the disc and fossa
what is CR
when the condyles are in the most anteriorsuperior position in the glenoid fossa braced up on the intermediate zone of the disc and the mandible is free to rotate about the terminal hinge axis (up to but not including the point of first tooth contact
what does CR refer to
the joints not the teeth
how does the mandible move in CR
freely arc up and down along the terminal hinge axis
what is it called when the teeth cannot contact in CR
deflection
what is CR the ideal position
- musculature in CR
-TMJs in CR
the muscles ____ in CR
function harmoniously
why is the joint stable in CR
because the muscles attached to the joint prevent dislocation of the articular surfaces
what are the muscles that stabilize the TMJs and what does their contraction result in
-the masseters and the medial pterygoids
- contraction results in antero superior vector of force (stability)
what muscles are the most relaxed in CR
lateral pterygoids
describe the condyles in relation to the articular eminence in CR
condyles rest against the posterior slope of the articular eminence therefore can tolerate higher stresses
in the most retruded position:
-the retrodiscal tissues are innervated and would not tolerate stress
- the posterior wall of the articular fossa is very thin
in CR TMJs are stable even when
heavy loads/forces are applied
CR is the position to which we restore
- completely edentulous patients
- partially edentulous patients, when there are so 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 should the posterior teeth be described as in CR for optimal functional occlusion
multiple, even, bilateral and simultaneous occlusal contacts with the mandible
how are the posterior teeth loaded for optimal functional occlusion
loaded along the long axis of the tooth called axial loading
why are mutliple posterior teeth contacts importatn
the more teeth that contact the more stress is distributed throughout the arch
why are even posterior teeth contacts important
ALL posterior teeth should contact evenly because it distributes the stress over all the teeth
why are bilateral posterior teeth contacts important
for stability. if tooth contacts occur only on one side the mandible will pivot towards that side of contact and put increased pressure on the other side’s TMJ
what type of forces on the teeth are not well accepted
lateral forces
through axial loading _____ can be applied
heavier stresses
anterior teeth should have ____ occlusal contacts when the posterior teeth are in occlusion
lighter
why are anterior teeth not able to withstand higher loads
they are not 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 are contacts between the posterior teeth during excursive movements called and what can they cause
interferences and can cause damage to teeth and periodontium
why is canine guidance/anterior guidance the optimal occusal scheme
- the more anterior the resistance (load) occurs, the lesser the impact
- the canine has the longest root and best bone support
what is the mandible classified as
a class III lever
what is optimal functional occlusion also referred to as
mutually protected occlusion
what is optimal functional occlsuion
multiple, even, bilateral, simultaneous occlusal contacts of the posterior teeth in MIP while the mandible is in CR position
- MIP = CR
how are posterior teeth loaded in MIP
axially
what is mutually protected occlusion
the posterior teeth withstand the majority of the load in MIP, protecting the teeth from high loads
- the anterior teeth disclude the posterior teeth in excursive movements thereby protecting the posterior teeth from off axis loading
-posterior teeth can tolerate axial loading well and protect anterior teeth which are not axially loaded in MIP
why can anterior teeth can tolerate lateral forces in excursive movements
because they are further away from the fulcrum and the loads are less
what is group function
when the mandible moves laterally the mandible is guided by 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
the canine, premolars and MB cusp of the first molar
the more ____ the contacts, the greater the force- ____to the source of power; the more destructive the forces
posterior; closer
on the working side, what guides along the inner inclines of the maxillary teeth as far posteriorly as the MB cusp of the first molar
only the buccal cusps of the mandibular teeth
are there contacts on the non working side in group function
no
is group function ideal
no but it is acceptable
group function is the only option for patients who:
- have no anterior vertical overlap
- a very large anterior horizontal overlap (Class II)
- have a reverse overlap (class III)
what is group function also known as
unilateral balance
what is balanced occlusion
-simultaneous contacts on both sides (working and non working) during lateral excursive movements (working side contacts and balancing side contacts)
- contacts between the posterior and anterior teeth during protrusive movement
what happens in balanced occlusion on the WS and NWS 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
- on the left side (NWS) inner inclines of mandibular buccal cusps contact inner inclines of maxillary lingual cusps
describe balanced occlusion during protrusion
there are contacts between posterior and anterior teeth
describe balanced occlusion on posterior teeth
mesial inclines of mandibular cusps occlude with distal inclines of maxillary cusps
describe balanced occlusion for dentate patients
- not acceptable or ideal for dentate patients
- promotes tooth wear on dentate patients
when is balanced occlusion acceptable
for complete dentures
describe non working side contacts in balanced occlusion
non working side contacts are extremely destructive and must be avoided
