Chapter 3 J: Class III Preparation

Question 1

Is there class 4 for amalgam?

Answer 1

No

Question 2

Where can we have a class III amalgam restoration on an incisor ?

Answer 2

Lingual, above the cingulum

Question 3

What is a class III cavity?

Answer 3

It’s a cavity located on the proximal surfaces of anterior teeth, NOT involving the incisal angle/edge.
Involves the aesthetic zone

Question 4

When is restoring class III cavities with amalgam indicated?

Answer 4

When they’re located on the distal surfaces of maxillary and mandibular canines
Especially if:
- caries do not underline distal slopes of canines
- labial-axial angle is intact
- after removal of caries, sufficient tooth structure is present
- restoration will not be directly loaded with occlusal forces

Question 5

Related to the initial tooth preparation of class III: the outline should only include?

Answer 5

The proximal surface

Question 6

What shape does the initial tooth preparation of a class III have?

Answer 6

Triangular

Question 7

Where is the enamel penetrated through in the initial tooth preparation of class III cavities?

Answer 7

Distolingual marginal ridge

Question 8

Related to the initial tooth preparation of class III: : the lingual wall should meet the axial wall at an ___ angle?

Answer 8

Obtuse

Question 9

Related to the initial tooth preparation of class III: the depth of the bur should be?

Answer 9

0.5mm into dentin

Question 10

Related to the initial tooth preparation of class III: the cavosurface margin should be ___ degrees at all margins?

Answer 10

90

Question 11

Related to the final tooth preparation of class III the steps are:

Answer 11

1. Removing any remaining infected dentin (with a slow speed or a spoon excavator)
2. Pulp protection
3. Secondary resistance and retention
4. Finishing the external walls (removing all unsupported enamel and cavosurface margin of 90 degrees)
5. Final cleaning and inspection of the preparation

Question 12

Related to the initial tooth preparation of class III: how do you provide resistance?

Answer 12

• butt joint, rounded internal angles, and sufficient bulk of amalgam

Question 13

Related to the initial tooth preparation of class III: how do you provide retention ?

Answer 13

Retention grooves and dovetail

Question 14

What is a class V cavity?

Answer 14

Cavity located on the gingival third of facial and lingual surfaces of all teeth

Question 15

What are the free surfaces?

Answer 15

Facial and lingual

Question 16

When is a class V restoration never indicated in anterior teeth?

Answer 16

If it involves the aesthetic zone

Question 17

Related to the initial tooth preparation of class V: the outline is indicated by

Answer 17

The caries extension

Question 18

Related to the initial tooth preparation of class V: which bur is used and how is it held?

Answer 18

Inverted cone bur, held perpendicular to the long axis of the tooth

Question 19

Related to the initial tooth preparation of class V: how many mm should the initial axial wall depth be?

Answer 19

0.5mm into dentin

Question 20

Related to the final tooth preparation of class V: the steps are

Answer 20

1. Remove any remaining caries with a round bur
2. Retention is mandatory due to the divergence of the walls towards facial. Do grooves for retention
3. Extend the preparation close to but no to axial angles of the tooth to prevent secondary caries
4. Hoes and chisel to finish mesial, distal, and gingival walls

Question 21

What are the surfaces where the most unsupported enamel is found?

Answer 21

Mesial, distal and gingival walls.

Question 22

The support of amalgam is compromised (shape) so the ___ walls should be straight?

Answer 22

Occlusal, mesial, distal, and gingival

Question 23

Which wall should be rounded?

Answer 23

Pulpal

Question 24

In class V: Axial angles should always be?

Answer 24

Divergent