04 Tooth Prep Principles

Question 1

Total Occlusal Convergence

• Ant or Post teeth prepped with more
• Mand or Max?
• Which type of teeth?
• Single or FPD?

Answer 1

1. Posterior’s
2. Mandibular
3. Molars
4. FPD’s

Question 2

1. What is a realistic degree range for total occlusal convergence?

Answer 2

10 to 20 degrees

Question 3

1. Out of taper, diameter, and height, which is the most critical to retention?

Answer 3

Diameter and height > taper

Question 4

2. Minimum occluso-cervical height for adequate resistance for anteriors and premolars?

Answer 4

3 mm

Question 5

2. Minimum occluso-cervical height for adequate resistance for molars?

Answer 5

4 mm

Question 6

3. Recommended occluso-cervical to facial-lingual ratio for adequate resistance for all teeth?

Answer 6

0.4 or higher (shorter base needs to be more parallel total occlusal convergence)

Question 7

3. What are means of increasing resistance form of a short, wide prep?

Which teeth typically have height to base issues?

Answer 7

1. Box, groove, or ledge (shortens the tangent line and increases the resistance area)
2. Molars have a height to base and TOC problem

Question 8

4. Where should grooves be placed to maximally improve resistance to faciolingual forces?

Answer 8

Proximal (facial/lingual grooves only provided partial resistance)

Question 9

5. Where should finish lines be positioned, provided retention and resistance form, tooth condition, and esthetics permit?

Answer 9

Supragingivally

Also level

Question 10

6. What finish line recommended for all metal crowns and how deep should that finish line be?

Answer 10

1. Chamfer finish

2. 0.3 mm deep

Question 11

6. What finish line for metal ceramic and how deep?

Answer 11

1. Chamfer or shoulder

2. 1.5 mm

Question 12

6. What finish line for all ceramic crowns and how deep?

Answer 12

1. Shoulder finish if not etched and either shoulder or chamfer if bonded
2. 1 mm

Question 13

7. AMR - Axial and occlusal reduction

Answer 13

1. Axial - 0.5 mm

2. Occlusal - 1 mm

Question 14

7. MCR - Axial and occlusal reduction

Answer 14

1. Axial - 1 mm

2. Occlusal - 2 mm

Question 15

7. ACR - Axial and occlusal reduction

Answer 15

1. Axial - 1 mm

2. Occlusal - 2 mm (1.5 for e-max lithium disilicate)

Question 16

8. Sharp line angles produce stress concentration, which is structurally significant with what type of restoration?
   - What is the purpose of rounding line angles with AMR and MCR crowns?

Answer 16

1. Significant with ACR

2. Facilitating lab procedures and optimizing fit

Question 17

9. Smooth or rough tooth preparation enhances fit of restorations?

Answer 17

Smooth preparations