Occlusal Consideration And Articulation Selection Flashcards
What is the intercuspal position ICP or IP
Most dentate pts when asked simply to bite together on your back teeth close immediately into a comfortable reproducible closed position where the maximum number of tooth contacts occur this is ICP
What guides ICP
- Shape of teeth
2. Conditioned neuromuscular coordination
What is ICP determined by
ICP is the most closed position of the Jaws
What are synonyms for ICP
Centric occlusion CO
MAXIMUM INTERCUSPATION
Why does ICP matter
ICP IS USUALLY THE POSITION IN WHICH:
vertical occlusal forces are most effectively borne by the periodontium with teeth likely to be loaded axially
This helps stabilise their position
ICP is the end point of the chewing cycle where maximum force is exerted
In everyday practice this is the position of the Jaws in which Restorations are made
What position should Restorationsbe made to conform to?
ICP
What is centric occlusion
Centric occlusion is maximum intercuspation
Where the maximum number of teeth are in contact
Is ICP a comfortable reproducible position
Yes
What is guidance?
When a pt moves their mandible from side to side so that the teeth in opposing Jaws slide over each other the path taken is determined partly by the shapes of the teeth which make contact as well as the anatomical constraints of TMJ and masticatory neuromuscular function. They provide Guidance for the movement of the mandible
What guides the mandible?
Guidance teeth can be any teeth anterior or posterior
The shape and form of the TMJ also guide. The movement of the mandible
What is the working side
When the pt slides the mandible out to one side the side they move the mandible towards is the working side
What is the side the mandible is moving away from
Non working side
An excursion to the right side:
Will make the right side the working side and the left the non working side
What do the guidance teeth do?
During excursions the upper and lower guidance teeth will be in contact and partly dictate the movement of the mandible
What is canine guidance
This is where the upper and lower canines on the working side are the only teeth in contact during a lateral excursion causing all the posterior teeth to disclude
What is group function
When several pigs of teeth usually premolars or premolars and canines and sometimes molars on the working side share the contacts during excursions group function is said to take place
What teeth provide protrusive guidance
Incisors and canines
Usually provide protrusive guidance when the mandible slides forward but where there is only a limited over bite the posterior teeth may be involved
Why does it matter what teeth are providing guidance
Guidance teeth are repeatedly loaded non axially (laterally) during excursions
As a result heavily restored or crowned teeth may be at risk of fracture or decemntation particularly if they are heavy
What are the manifestations of problems with guidance
Fractured teeth or Restorations Accelerated local wear Tooth migration Tooth mobility TMJ dysfunction
What is important to remember when examining a pt before restorative work
To identify which teeth provide Guidance before you start prep
When should conform to the pre op guidance
If during examination it is found that the guidance is satisfactory and the guidance tooth or teeth are strong enough to withstand the likely loading in the long term it is usually best to reestablish the same guidance pattern in the new restoration
If you feel that a tooth you are about to crown is insufficiently robust to carry a guidance contact what can you do?
It may be that guidance is best moved onto other teeth
Give an example of a situation where conforming to the pt’s occlusion?
Where a broken down guidance canine is restored with a post retained crown
There may be a risk of root fracture of the tooth in the longer term because of the heavy lateral forces
In a case like this guidance can be transferred from the canine to the premolars if they are in a better position to accept the heavy loads
What are some practical reasons for identifying guidance teeth
The need to provide clearance from the opposing tooth during prep not just in ICP but also along the guidance track
If you don’t do this you can end up unwittingly transferring all the guidance forces on to your new crown
The need to select and Prescribe an appropriate material to restore the guidance surface (metal is usually best if possible)
Getting guidance right is one of the most important aspects of crown provision. How can you ensure you do this
Provide clearance from the opposing tooth during rep’s not just in ICP but also along the path of excursions (otherwise you might end up transferring all the guidance forces on to your new crown)
Select and Prescribe an appropriate material to restore the guidance surface (metal is usually best)
