CSAR 3 - Indirect restorations and principles of preps

Question 1

What is the difference of the preparations on the functional and non-functional cusps of a crown prep?

Answer 1

More prep on functional –> 0.5mm more

Question 2

If a tooth is over prepped what happens?

Answer 2

Compromises/weakens pulp

Question 3

If a tooth is under prepped what happens?

Answer 3

Think weak crown or over built crown

Occlusal and periodontal problems

Question 4

What is the difference between retention and resistance form?

Answer 4

• Retention form = prevents removal of restoration along long axis of tooth
• Resistance form = prevents dislodgement by forces directed in apical/oblique direction

Question 5

When prepping a tooth for a crown, what length should the prep height be?

Answer 5

3-4mm

Question 6

What taper should be used when prepping a crown?

Answer 6

6-12 degrees

Question 7

What 2 methods can be used to increase ferrule of crown?

Answer 7

Crown lengthening

Orthodontic extrusion

Question 8

What 3 different types of margins can be created when prepping a tooth?

Answer 8

Shoulder
Chamfer
Knife edge

Question 9

If prepping a tooth for a full metal crown what occlusal and marginal reductions should be made?

Answer 9

1-1.5mm occlusal reduction

0-1mm chamfer

Question 10

If prepping a tooth for a porcelain crown what occlusal and marginal reductions should be made?

Answer 10

2-2.5mm occlusal reduction

0.8-1mm heavy chamfer/shoulder

Question 11

Why is a knife-edge margin not preferred?

Answer 11

Difficult for lab to identify

Question 12

Why is dentine bonding not predictable?

Answer 12

Bond can degrade as dentine has fluid in tubules and linked to the pulp