Occlusion Flashcards
Consequences of bad occlusion
Fractured cusps, teeth, restorations Failed crowns and bridges Localised periodontal disease Drifting/overerupted teeth Loss of vitality of teeth TMD Muscle pain Parafunction
ICP
Mandible position when there is maximum cuspation of teeth
RCP
Mandible position when condyles are fully seated in glenoid fossa/in most superior position - first tooth contact in this position
CR
Jaw position when condyles are fully seated in glenoid fossa/in most superior position - best neuromuscular position because muscles don’t need to work as hard. Condyle braced by bone so muscles are doing less work.
Techniques to find CR/RCP
and when to use
Gothic arch tracing Manual positioning/Dawson technique Flat plane splint Anterior jig - Useful for when reorganising occlusion or if ICP is unstable or OVD needs to be increased e.g. CD, TMD
THA/terminal hinge axis
Hinge movement of condyles in CR
Lateral excursion details [4]
The working side is the side you’re moving to. Group function or canine guidance.
NWS - there shouldn’t be any contacts hee. If there are, they are called interfering contacts and lateral force on cusps can cause a fracture.
Bennett movement/angle
Horizontal plane
During lateral excursion
NWS Condyle moves down forward and rotates = Bennett’s movement
WS condyle rotates ~7.5 degrees = Bennett’s angle
Protrusive excursions
Anterior guidance or group function if class 3 or edge-to edge. Condyle moves down and forward
Condylar movement
Rotation movement in glenoid fossa first and then moves down articular eminence.
Rotation and translation
Occlusal schemes [4]
Ideal occlusion Balanced occlusion (For CD) Group function Gnathecial occlusion (all teeth working in all movements. Difficult)
Principles of ideal occlusion [4]
- ICP = RCP
- Mutual protection bw anterior and posterior teeth, heavier contacts on posterior teeth during ICP movements, lighter during eccentric.
- Posterior teeth disocclude on eccentric movents
- Forces down long axis of the molar teeth
Bruxists in ideal occlusion
Parafunction in RCP and destroy this contact
Grind in ICP and increase neuromuscular activity
- Good to know where RCP contact is and provide tougher restoration or make ICP = RCP
Why is canine guidance good
Good crown: root ratio
Highly innervated so can feel when too much force etc
Distance from TMJ muscles/hinge means less force through it
What is group function
Lots of teeth contacting on WS, NWS teeth disocclude
Class 2 div 1 protrusive movements
May have posterior contacts/less anterior guidance, esp if proclined.
Class 3 protrusive movements
Will have posterior contacts or group function e.g. if edge-to-edge
Different types of articulators [5]
Simple hinge articulator - just has the teeth in ICP, no eccentric movements.
Anatomical articulators - have the hinge in the same place as TMJ so models can be mounted in CR. Show eccentric movements
- Average value articulator = 30-degree condylar angle and flat/straight condylar pathway
- Semi-adjustable = adjustable condylar angle but a flat condylar pathway
- Fully adjustable = custom made condylar pathways
Denar Automark articulator = 20-degree condylar angle, which means that any posterior work will definitely have disocclusion on the model, and be more in real life bc IRL condylar angle is steeper.
What is a facebow used for/details
Used to record the relationship between condyles and teeth.
2 separate parts - earbow to record TMJ position, and one on the occlusal plane and then join them together and send to the lab.
Also useful for getting the correct height of the model.
Can get different ones for maxilla and mandible.
Complete denture - equipment and occlusal considerations
ICP = RCP
Facebow and models mounted in CR
To create balanced occlusion (ICP = RCP) and restore OVD
Restorative work on posterior disoccluding teeth - equipment and occlusal considerations
Facebow and mount models in ICP
Can use a 20-degree articulator to ensure no posterior interfering contacts
Or use a simple articulator and rely on the anterior guidance.
Restorative work on guiding anterior teeth- equipment and occlusal considerations
Facebow and mount in ICP
Record all eccentric movements and contacts on the anterior teeth on the articulator
Make sure not to change these movements
- If intending to change the movements, need to mount the models in CR
RPD - equipment and occlusal considerations
If OVD and ICP are stable - mount the models in ICP.
If unstable, facebow and mount models in CR and recreate ideal occlusion (ICP = RCP, eccentric movements, etc.)
Hard acrylic splints - equipment and occlusal considerations
Facebow and mount models in CR
20-degree articulator to ensure posterior disocclusion