Occlusion: Jaws and relationships and dynamic occlusion

Question 1

Intercuspal position (ICP)

Answer 1

When the teeth are together. Used to check the bite.

Teeth are in the ICP during eating.

PDL mechanoreceptors provide sensory information allowing return to ICP position.

Question 1

Occlusion

Answer 1

The contact relationships of teeth or equivalent.

Question 2

Articulation

Answer 2

The dynamic relationships of the teeth when in sliding contact.

Question 3

Jaw relationship

Answer 3

Positional relationship which the mandible bears to the maxilla.

Question 4

Rest/postural position

Answer 4

At rest = teeth apart.
Governed by muscle elasticity.
Reproducible in live with teeth or without teeth.
Important with full dentures.

Question 5

Retruded contact position (RCP or ligamentous position)

Answer 5

Condyles retruded in glenoid fossa

Teeth in contact (the same as the ICP for 10-20% of patients)

Clinical significance; symmetrical retrusion, gives a reproducible relationship between the maxilla and mandible.

Question 6

Occlusal Vertical Dimenson (OVD)

Answer 6

The face height with the teeth in the ICP.

Measures between two arbitrary points.

Governed by the height of the teeth (important to get OVD correct).

Question 7

What is used to measure the OVD?

Answer 7

Willis gauge; measures between the vertical dimension in mm between the maxilla and mandible.

Question 8

Rest/Postural vertical dimension (RVD)

Answer 8

Face height with mandible in rest/postural position.
Measured between two arbitrary points.
This should not alter significantly throughout life.

Question 9

What is the freeway space?

Answer 9

RVD - OVD = FWS
The space between teeth in rest position.
Difference between RVD and OVD.
2-5mm

Question 10

Working side

Answer 10

The side to which the teeth move.
Teeth contact by guidance; canine guidance or group function.

Question 11

Non-working side

Answer 11

The side away from which the teeth move.
Teeth do not contact - disclude.
Occasional contact can occur.

Question 12

What is canine guidance?

Answer 12

When the lateral movements are determined by the canine contacting

Question 13

What is group function?

Answer 13

When the lateral movements are determined by multiple teeth.

Question 14

What happens to the condyle on the working side of the jaw?

Answer 14

Condyle rotates around vertical axis, lateral bodily movement “Bennett Movement”

Question 15

What happens to the condyle on the non-working side of the jaw?

Answer 15

Condyle moves downwards, forwards over eminence and then moves medially.

Question 16

Excursion vs protrusion

Answer 16

Excursion is the jaw moving out as far forwards as it can, when moving to one side.

Protrusion is just when the jaw moves out as far forwards as it can.

Question 17

Balanced occlusion concept

Answer 17

Tooth contact during excursions at both working and non-working sides.

Ideal for F/F dentures; maintains stability, control cusp shape/tooth position and orientation.

Difficult to achieve because teeth rarely in contact.

Cannot exist in a normal dentate occlusion.