Dynamic Occlusion

Question 1

Define:

• occlusion:
• articulation:
• jaw relationship:

Answer 1

• occlusion: contact relationships of teeth or equivalent
• articulation: dynamic relationships of teeth when in sliding contact
• jaw relationship: positional relationship which the mandible bears to the maxilla

Question 2

What is the rest/postural position?

Answer 2

Rest/postural position: at rest - teeth apart

• maintained by minimal muscle activity or governed by muscle elasticity
• remains reproducible throughout life in both dentate and edentulous subjects (stable position)
• important with full and partial dentures - reference position

Question 3

What is intercuspal position?

What is retruded contact position? (RCP)

Answer 3

Intercuspal position: maximal intercuspation/interdigitation

• depends on dentition
• may change due to tooth wear/loss so not stable position

Retruded contact position: ligamentous position

• condyles retruded maximally in the glenoid fossa
• teeth in contact: 1-2mm posterior to ICP, same as ICP for 10-20% of patients

Clinical significance: symmetrical retrusion

• gives reproducible relationship between maxilla and mandible
• often used in patients with full dentures

Question 4

What is occlusal vertical dimension (OVD)?

What happens if this is measured wrong?

What instrument can you use to measure this?

Answer 4

OVD: face height with teeth in ICP

• measured between two points (dot on upper lip and lower)
• governed by height of teeth
• if wrong, denture may be wrong causing patient to overclose, or lower face height too high and patient struggles to close lips together
• Willis gauge - place upper element against nose, lower element slide up chin and measure - compare with rest vertical dimension

Question 5

What is rest vertical dimension (RVD)?

What is freeway space (FWS)?

Answer 5

Rest vertical dimension:

• face height with mandible in rest.postural position
• measured between two arbitary points (same as OVD), also using a Willis gauge
• this should not significantly alter throughout life

Freeway space:

• FWS = RVD - OVD
• gap between teeth in rest position
• 2-5mm range usually

Question 6

What is canine guidance?

What is the other type of guidance?

What happens on the non-working side?

What is the movement at the working side of the condyle?

Non working side?

Answer 6

Canine guidance: upper and lower 3’s are only teeth in contact during lateral excursion

Group function: more than one pair of teeth touching during lateral excursion

On the non-working side, the teeth disclude

Working side: Bennett Movement

• rotates around vertical axis
• lateral bodily movement

Non-working side: Bennett Angle

• moves downwards, forwards over eminence, moves medially

Question 7

What is the balanced occlusion concept?

Answer 7

• 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 are rarely in contact
• cannot exist in a normal dentate occlusion