Crowns & Bridges

Question 1

What is a crown?

Answer 1

An artificial replacement that restores missing tooth structure by surrounding part or all remaining tooth structure with a material e.g. metal, porcelain

Question 2

List the 4 types of crowns:

Answer 2

1. Anterior complete crowns for vital teeth
2. Anterior complete crowns for root filled teeth
3. Posterior complete crowns
4. Posterior partial crowns

Question 3

Give 2 advantages and 2 disadvantages of ceramic crowns:

Answer 3

Advantages:
1. Highly aesthetically pleasing and high strength material
2. Resist plaque accumulation

Disadvantages:
1. More teeth reduction
2. Bitterness

Question 4

What size shoulder is needed for support in crowns?

Answer 4

2mm shoulder

Question 5

Give 2 advantages and 2 disadvantages of metal ceramic crowns:

Answer 5

Advantages:
1. High strength
2. Adequate tooth reduction can be done on palatal surface of teeth

Disadvantages:
1. More susceptible to root fracture upon trauma
2. Margin often placed sub-gingivally for aesthetics which can cause periodontal problems

Question 6

Give 2 indications and 2 contraindications of metal ceramic crowns:

Answer 6

Indications:
1. Aesthetics
2. Can act as retainer for fixed dental prosthesis

Contra-indications:
1. Active carious lesions & perio. problems
2. Young patients with large pulp chambers

Question 7

Give 2 advantages and 1 disadvantage of cast metal crowns (GOLD):

Answer 7

Advantages:
1. Greater retention and resistance
2. Less tooth preparation required

Disadvantage:
1. Poor aesthetic

Question 8

What is the main disadvantage of metal porcelain crowns?

Answer 8

Retention can be a problem

Question 9

What is the main advantage and disadvantage of ceramic crowns?

Answer 9

Advantage = aesthetic

Disadvantage = requires a lot of tooth preparation

Question 10

What material are posterior-partial crowns always made of?

Answer 10

Cast metal

Question 11

Give 3 reasons for recementing crowns:

Answer 11

1. Restore appearance (aesthetic)
2. Minimise tooth’s sensitivity to hold, cold, air
3. Prevent movement of neighbouring or opposing teeth

Question 12

What is the most common temporary cement material?

Give another example

Answer 12

Temp bond

GI (Fuji Temp)

Question 13

When is temp bond NE (non-eugenol) used?

Answer 13

1. When there is a composite core
2. Eugenol allergy

Question 14

Give 2 reasons why Zinc Polycarboxylate (Poly-F) is used as a temporary cement:

Answer 14

1. Unretentive preparations
2. Risk of crown falling off before next appointment

Question 15

What is a bridge?

Answer 15

Any dental prosthesis that is luted, screwed or mechanically attached to natural teeth, tooth roots and/or implant abutments that furnish primary support for dental prosthesis

Question 16

What are the 4 materials used for bridges?

Answer 16

1. Metal
2. Metal-ceramic
3. All-ceramic
4. Acrylic

Question 17

What are the 4 structure-types of bridges?

Answer 17

1. Fixed fixed (traditional)
2. Fixed moveable
3. Cantilever
4. Spring cantilever

Question 18

Give 2 advantages and 2 disadvantages of fixed-fixed bridges:

Answer 18

Advantages:
1. Provides cross arch splinting
2. Ease of handling

Disadvantages:
1. Possible bending
2. All units have to be cemented simultaneously

Question 19

Give 2 advantages and 2 disadvantages of fixed-movable bridges:

Answer 19

Advantages:
1. Allows flexure of mandible
2. Units can be cemented as individual sections

Disadvantages:
1. Metal may show occlusally
2. Wear of joints

Question 20

Give 2 advantages and 2 disadvantages of cantilever bridges:

Answer 20

Advantages:
1. Preserve tooth structure
2. Minimal pulp trauma

Disadvantages:
1. Length of span limited to one pontic only
2. Not successful for posterior prosthesis

Question 21

What are spring cantilever bridges restricted to?

What are 3 disadvantages of these?

Answer 21

Restricted to upper incisor teeth

Disadvantages:
1. Only supports one pontic
2. Food impaction under metal connector
3. Fracture and dislodgement of bridge

Question 22

What are the best 2 additional aids to toothbrushing to clean crowns and brides?

Answer 22

1. Superfloss
2. Air/water flosser