M+O 6 - dynamic occlusion Flashcards
What is occlusion?
the contact relationship of teeth or equivalent
What is articulation?
the dynamic relationships of the teeth when in sliding contact
What is jaw relationship?
positional relationship which the mandible bears to the maxilla
What are the 3 vertical jaw relationships?
- rest/postural position
- intercuspal positon (ICP)
- retruded contact position (RCP)
What are the 3 vertical jaw dimensions?
- occlusal vertical dimension (OVD)
- rest vertical dimension (RVD)
- freeway space (FWS)
If you have done a filling on a patient, what should you check?
check bite to check the ICP
What is the rest/postural position?
at rest - teeth apart
How is the rest/postural position maintained?
- minimal muscle activity or…
- is it governed by muscle elasticity
Is rest/postural position reproducible?
remains reproducible throughout life in both dentate and edentulous subjects
When in rest/postural position of particular clinical importance?
when making full dentures
What is ICP?
- maximal intercuspation/interdigitation
- depends on dentition
- ICP changes, rest position doesn’t
What is the jaw in RCP (or ligamentous position)?
- condyles retruded in the glenoid fossa
- teeth in contact
- ~1-2mm posterior to ICP
- same as ICP in 10-20% of patients
What is the clinical significance of RCP?
- symmetrical retrusion
- gives a reproducible relationship between the maxilla and mandible
What is the OVD?
- the face height with the teeth in ICP
- measured between 2 arbitrary points
- governed by the height of the teeth
What can be used to measure OVD?
Willis gauge
- measures from under nose to under chin
What is RVD?
- face height with mandible in rest/postural position
- measured between 2 arbitrary point
- this should not alter significantly throughout life
What is FWS?
- the space between teeth in rest position
- difference between RVD and OVD
- 2-5mm
How do you calculate FWS?
RVD-OVD=FWS
What is it called with the FWS is too big and the OVD is too small?
overclosure
What are the 5 border movements of the mandible?
- ICP
- RCP
- lower extent of retruded hinge arc
- maximum opening
- maximum protrusion
What are the 3 anatomical guide planes?
- incisal guidance
- cuspal inclines
- TMJ
What is the ‘working side’?
- the side to which the teeth move
- teeth contact by guidance:
- canine guidance
- group function
What is the ‘non-working side’?
- the side away from which the teeth move
- teeth do not contact - disclude
-occasional contact can occur e.g. X-bite, after extractions, URAs
Why do the teeth on the non-working side not contact?
because the condyle drops down
What is canine guidance, and what is group function?
- canine guidance - canines in contact
- group function - multiple teeth in contact
What happens to the condyle on the working side?
- rotates around vertical axis
- lateral bodily movement - Bennet movement
What happens to the condyle on the non-working side?
- moves downwards
- forwards over eminence
- moves medially
What muscle pulls the condyle on the non-working side forward?
lateral pterygoid
What is the balanced occlusion concept?
- tooth contact during excursion at both working and non-working sides
- difficult to achieve because teeth rarely in contact
- cannot exist in a normal dentate occlusion
Why is the balanced occlusion concept ideal for F/F dentures?
- maintains stability
- control cusp shape/tooth position and orientation
