Impression Materials Pt. 1

Question 1

Classify impression materials

Answer 1

1. Tissue displacement
2. Viscosity
3. Properties of set materials

Question 2

What are the factors that effect accuracy of impression materials?

Answer 2

1. Viscosity
2. Wetting
3. Interaction with saliva
4. Dimensional change
5. Coefficient of thermal expansion
6. Retention of material
7. Removal without distortion from undercut

Question 3

Materials used to record undercuts must have which properties?

Answer 3

1. Adequate elasticity
2. Adequate tear resistance
3. Low rigidity

Question 4

If an impression contracts on setting want will happen to the die?

Answer 4

Oversized and loose fitting

Question 5

If an impression material expands during setting what happens to the die?

Answer 5

Undersized and results in a tightly fitted crown.

Question 6

What are the manipulative variables of impression materials?

Answer 6

1. Method of dispensation
2. Setting mechanism

Question 7

Chlorine compounds cannot be used to clean which type of impression compound?

Answer 7

Zinc Oxide Eugenol Pastes

Question 8

Phenolic sprays can be used on which impression compound materials?

Answer 8

1. Zinc Oxide Eugenol Paste
2. Impression compound

Question 9

For tissue management and moisture control, which two materials/ drugs are used?

Answer 9

Retraction cord and Hemostatic agent

Question 10

Which three methods are used for displacement of gingival tissues away from tooth preparation?

Answer 10

1. Retraction cord
2. Electro surgical unit (not for patients with pacemaker)
3. Soft tissue laser

Question 11

What hemostatic agents can be present in retraction cords?

Answer 11

1. Epinephrine containing cords
2. Aluminum containing cords
3. Ferric chloride containing cords

Question 12

What are the complications of retraction cords?

Answer 12

1. Gingival recession
2. Epinephrine has systemic effects- contraindicated in patients with cardiac conditions.
3. Aluminum and ferric chloride dissolve superficial dentine and causes sensitivity.

Question 13

What is the ideal disinfectant for impression materials?

Answer 13

Immersion in sodium hypochlorite solution for 10 minutes.

Question 14

What are the requirements of impression materials?

Answer 14

1. Factors that effect accuracy
2. Factors that effect dimensional stability
3. Manipulative variables
4. Additional factors such as cost, taste, colour etc.

Question 15

If the impression stock tray is too long or two short what should we do?

Answer 15

1. Too long: cut it back
2. Too short: use a rigid thermoplastic material like green stick tracing compound.

Question 16

Which part of the impression material sets first?

Answer 16

The part that is directly in contact with the lips or tongue sets more rapidly than the bulk of the material in the tray