intro to occlusion

Question 1

Why study occlusion?

Answer 1

Failure of routine restorations esp. fractures

Over eruption and tilting due to undercontouring

Question 2

What is ICP?

Answer 2

Intercuspal position
Position of mandible where there is the most tooth contacts
Most comfortable position ideally

Question 3

What is RCP?

Answer 3

Retruded contact position
First tooth contact in centric relation
Range of movement (~20-25mm) when condyles are fully seated in glenoid fossa
Hinge movement

Question 4

What is CR?

Answer 4

Centric relation
Relation of mandible to maxilla when condyles are seated in mid most uppermost position in glenoid fossa
Snuggly seated- most comfortable

Question 5

What are protrusive excursions?

Answer 5

Move forwards
Start in ICP, move mandible forward slowly
Teeth in contact when they slide forward are in protrusive guidance

Question 6

What are working and non-working side lateral excursions?

Answer 6

Move side to side

Working side- side jaw is moving to, guidance can be canine or group function
Non working side- posterior teeth should separate to avoid destructive forces on inclines of teeth

Question 7

What is the classification for protrusive guidance?

Answer 7

Class I- usually incisors, usually discludes on posteriors

Class II div I- shallow anterior guidance, initial guidance by posterior

Class II div II- v steep overbite, steep guidance on anterior teeth

Class III- v little/no/negative overbite so no guidance on anterior teeth, guidance by posterior teeth

Anterior openbite- no contact between anterior teeth, posterior provide guidance

Question 8

What is an interference?

Answer 8

Non working side contact

Can lead to failed restorations and occlusal disharmony

Question 9

How do you understand a detailed occlusal analysis?

Answer 9

1. ICP contacts
2. RCP contacts
3. Slide from RCP to ICP
4. Anterior guidance
5. Lateral excursions

Question 10

What do you use to check occlusion?

Answer 10

Horseshoe articulating paper- too thick- only for dentures

Regular articulating paper- okay

GHM articulating paper- 19 microns thick, excellent for detailed occlusal analysis

Shimstock foil- 8 microns thick, excellent for checking contact point (bite down, try to pull out)

Question 11

How do you check ICP contacts?

Answer 11

Shimlock/GHM paper

Question 12

How do you check RCP contacts?

Answer 12

Manipulate into centric relation- stabilise head, position fingers on lower border on mandible, thumbs on symphysis, gently open and close freely, guide upwards into occlusion

Note first contact w GHM

Question 13

How do you check slide from RCP to ICP?

Answer 13

Is slide large or small?

Question 14

How do you check anterior guidance?

Answer 14

Which teeth guide?
Use shimstock/GHM- v slow movement
Check if posterior disclusion?
Check for crossover interferences- overlap upper teeth w lowers

Question 15

How do you check lateral excursions?

Answer 15

Which teeth guide?
Canine or group function?
Shimstock/GHM to indicate
Move jaw v slowly
Any non working side contacts?

Question 16

Why might you change the occlusion for a restoration?

Answer 16

Tooth in excursive contact previously
But led to restoration failure or might lead to failure
So change to have minimal/no guidance
However need ICP contact to avoid overeruption

Be aware- may transfer excursion onto another tooth