Crowns

Question 1

Why crowns

Answer 1

To protect weakened tooth structure
To improve or restore aesthetics
For use as a retainer for fixed bridgework
When indicated by the design of a RPD
Rest seats
Clasps
Guide planes
To restore tooth function
e.g. restore in OVD

Question 2

When not to use crowns

Answer 2

Active caries and periodontal disease
More conservation options available
Lack of tooth tissue for preparation
Unable to provide post and core
Unfavourable occlusion

Question 3

What are the principles of crown prep

Answer 3

1)Preservation of tooth structure

2)Retention and resistance

3)Structural durability

4)Marginal integrity

5)Preservation of the periodontium

6)Aesthetic considerations

Question 4

What is meant by retention and resistance

Answer 4

Retention:
Prevents removal of the restoration along the path of insertion or the long axis of the tooth preparation

is improved by limiting the number of paths of insertion

Resistance:
Prevents dislodgement of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces

Question 5

What are the finish lines confugurations

Answer 5

(a) Knife edge

(b) Bevel

(c) Chamfer

(d) Shoulder

(e) Bevelled shoulder

Question 6

What are te preservations of the perio.

Answer 6

Margins of the restoration should be:

Smooth and fully exposed to a cleansing action

Placed where the dentist can finish them and the patient can clean them

Placed supra-gingival or at gingival margin whenever possible

Question 7

What has tooth prep done

Answer 7

Compromises aesthetics in smile line
Degrades tooth function
Render a vital tooth sensitive
Compromise coronal seal of RCT’d teeth (in some cases)