Occlusal Consideration And Articulation Selection

Question 1

What is the intercuspal position ICP or IP

Answer 1

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

Question 2

What guides ICP

Answer 2

1. Shape of teeth

2. Conditioned neuromuscular coordination

Question 3

What is ICP determined by

Answer 3

ICP is the most closed position of the Jaws

Question 4

What are synonyms for ICP

Answer 4

Centric occlusion CO

MAXIMUM INTERCUSPATION

Question 5

Why does ICP matter

Answer 5

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

Question 6

What position should Restorationsbe made to conform to?

Answer 6

ICP

Question 7

What is centric occlusion

Answer 7

Centric occlusion is maximum intercuspation

Where the maximum number of teeth are in contact

Question 8

Is ICP a comfortable reproducible position

Answer 8

Yes

Question 9

What is guidance?

Answer 9

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

Question 10

What guides the mandible?

Answer 10

Guidance teeth can be any teeth anterior or posterior

The shape and form of the TMJ also guide. The movement of the mandible

Question 11

What is the working side

Answer 11

When the pt slides the mandible out to one side the side they move the mandible towards is the working side

Question 12

What is the side the mandible is moving away from

Answer 12

Non working side

Question 13

An excursion to the right side:

Answer 13

Will make the right side the working side and the left the non working side

Question 14

What do the guidance teeth do?

Answer 14

During excursions the upper and lower guidance teeth will be in contact and partly dictate the movement of the mandible

Question 15

What is canine guidance

Answer 15

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

Question 16

What is group function

Answer 16

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

Question 17

What teeth provide protrusive guidance

Answer 17

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

Question 18

Why does it matter what teeth are providing guidance

Answer 18

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

Question 19

What are the manifestations of problems with guidance

Answer 19

Fractured teeth or Restorations
Accelerated local wear
Tooth migration
Tooth mobility
TMJ dysfunction

Question 20

What is important to remember when examining a pt before restorative work

Answer 20

To identify which teeth provide Guidance before you start prep

Question 21

When should conform to the pre op guidance

Answer 21

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

Question 22

If you feel that a tooth you are about to crown is insufficiently robust to carry a guidance contact what can you do?

Answer 22

It may be that guidance is best moved onto other teeth

Question 23

Give an example of a situation where conforming to the pt’s occlusion?

Answer 23

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

Question 24

What are some practical reasons for identifying guidance teeth

Answer 24

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)

Question 25

Getting guidance right is one of the most important aspects of crown provision. How can you ensure you do this

Answer 25

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)