Anterior PFM

Question 1

What are the 4 stages of anterior PFM prep?

Answer 1

1. Buccal and incisal reduction
2. Proximal reduction
3. Palatal reduction
4. Margin finishing and smoothing

Question 2

What is size of the end of shoulder bur?

Answer 2

0.9mm

Question 3

How should you start prep?

Answer 3

Place buccal depth grooves

• Use full depth of shoulder bur to give approx 1mm
• Grooves in 2 planes

Question 4

How to prep incisal portion of tooth?

Answer 4

Place depth grooves - follow angle of tip

Final reduction 1.5mm

Question 5

How should buccal prep be refined?

Answer 5

Join depth grooves

Shoulder bur used - 1.2-1.5mm preparation

Question 6

Why is buccal prep of PFM heavy?

Answer 6

Need adequate space for metal and porcelain

Question 7

How to finish incisal reduction?

Answer 7

Join depth grooves - aim for 1.5mm reduction

Follow contour of anatomy

Question 8

How should proximal breakthrough be carried out?

Answer 8

Use needle bur
Achieve 5-10 degree taper
Then once broken through use chamfer bur (transition should be at mid-point so metal can’t be seen anteriorly)

Question 9

How should palatal reduction be carried out?

Answer 9

Lighter prep- chamfer (just metal)
Aim 0.5-0.7mm reduction
Cingulum reduction - use depth gauge pits

Question 10

Why is it important to have adequate cingulum depth reduction?

Answer 10

Will get perforations during try-in/ crown adjustment