Occlusion

Question 1

What is cuspid protected occlusion?

Answer 1

During lateral and protrusive movements, the canines guide the two arches so that the posterior teeth come out of contact (protect it from attrition wear)

Question 2

True or false: Tooth grinding is not pathological, but erosion is.

Answer 2

True, tooth grinding is so widespread that it is considered physiological. Teeth also remain functional throughout this process. The process can be termed “Occlusal equilibrations”

Question 3

Describe how occlusion is dynamic (continuously changes throughout life)

Answer 3

1. Tooth morphology determines occlusion
2. Occlusion and types of food that we eat determine masticatory patterns
3. Masticatory patterns determine wear patterns
4. Wear patterns determine tooth morphology
   - Cycle continues.

Question 4

Why is it important to retain primary dentition?

Answer 4

They act as space maintainers.

e.g. If E lost prematurely, 6 may drift forward and anterior crowding may result.

Question 5

What is interproximal wear?

Answer 5

As teeth are loaded with occlusive forces, tooth movement mesio-distally causes rubbing against each other = wear.

• Mesial wears faster than distal
• Aboriginals with normal interprox wear had less third molar impaction.

Question 6

Relate canine/cuspid protected occlusion with Group function.

Answer 6

As canines are worn down, premolars will then also come into contact during lateral excursion = group function.

Question 7

What is the main limitation of a plane-line articulator (vs. a semi-adjustable articulator)?

Answer 7

It cannot customise itself with the patient’s opening measurements, so if OVD change is required, plane-line articulator will result in a poor outcome.

Question 8

When is it okay to use a plane-line articulator?

Answer 8

When you’re not changing the patient’s OVD or occlusal scheme.

Question 9

What are the roles of the facebow and orbital pointer?

Answer 9

Facebow = provides distance between TMJ and upper arch (bitefork)
Orbital pointer = provides angle of upper arch (bitefork) relative to the cranial base.

Question 10

Why might it be better to use maximum interdigitation rather than centric occlusion?

Answer 10

There are many meanings of centric occlusion, one of them being maximum interdigitation.

Question 11

What does a protrusive record measure, and where would we apply this on an articulator?

Answer 11

• Protrusive record measures the angle of the articular eminence.
• Condylar angle track

Question 12

How do we obtain a customised Bennett angle for a patient?

Is it important to do so?

Answer 12

• Canine edge-to-edge bite record will provide the Bennett angle for the contralateral side
• No, most people will be okay with the default 15deg

Question 13

What are THREE treatments in which you would definitely use a semi-adjustable articulator vs. a plane-line articulator?

Answer 13

• Minor changes (e.g. cusp reduction)
• Orthodontics
• Fixed/Rem pros

Question 14

What might happen if you use a plane-line articulator when making a denture for someone?

Answer 14

We may need to adjust it A LOT.

Question 15

If we were making a denture for a patient that does not have lower posteriors to establish maximum interdigitation, what is one reproducible reading we can use instead?

Answer 15

Centric relation (to do with the position of the condyle in the TMJ)

Question 16

What is ONE issue with nightguards containing only anterior coverage?

Answer 16

Continual eruption of posterior teeth

Question 17

Why is it useful to place a ramp on a nightguard?

Answer 17

It mimics anterior guidance so that during eccentric movements (protrusion/lateral), the posterior teeth are discluded.

Question 18

How thick should a nightguard be?

Answer 18

Two credit card thickness on the posteriors.

Question 19

What is a survey line and what is it used for?

Answer 19

Survey line marks the points of maximum tooth diameter.
- This can be used to form extensions at points to improve retention while having the nightguard fit as well.
NOTE: retention usually placed bilaterally on 5’s and 7’s

Question 20

Why is having a duplicate master cast useful?

Answer 20

To check if the prosthetic appliance fits on the model.
If it does, but doesn’t fit on the pt, then the impression was inaccurate.
If it doesn’t fit on the duplicate master cast, it is the lab’s fault.

Question 21

How is the thickness of the nightguard set when using a plane-line articulator?

Answer 21

It is set by the bite wax when taking the bite registration.

Question 22

What is a ‘slide’? (prosthodontics/nightguard)

Is it okay to leave it as is?

Answer 22

Slide is interference by posterior teeth during canine guidance.
- It must be removed, but posteriors should still contact normally on maximal interdigitation.

Question 23

What are FIVE things that should be included on a nightguard request form to the lab?

Answer 23

• Please construct an upper dual laminated nightguard using bite record provided
• Thickness of NG as per thickness of wax
• Please include a ramp from 13-23
• Please survey the cast
• Please add acrylic extensions past survey line on 5’s and 7’s

Question 24

Why might we want to opt for a soft nightguard for a young child?

Answer 24

Hard/acrylic nightguards can potentially prevent growth of the hard palate, resulting in crossbite.