Temporary Crown & Bridges Materials

Question 1

FUNCTION

Answer 1

1. Protection of the prepared tooth.
2. Aesthetic
3. Masticatory function
4. Speech
5. Maintenance of the relationship between the prepared teeth and the other teeth.

Question 2

Requirements of Temporary Crown & Bridges Materials

Answer 2

1. Non toxic, non allergic and non irritant to soft tissues and pulp tissue(Biocompatible).
2. Adequate strength and abrasion resistance to withstand the masticatory force for short period
   of time.
3. Have a low thermal conductivity.
4. Easy to manipulate in crown former.
5. Low dimensional change on setting and should be not exothermic reaction.
6. Have a sufficient working time to allow mixing placement into impression and seating in the
   mouth.
7. Short setting time which facilitates its removal without distortion.
8. Rapid hardening outside the mouth to enable the trimmed crown or bridge to be cemented
   into place after a short period of time.
9. Good appearance ,translucent, color controllable ,color stable.

Question 3

Types of Temporary Crown & Bridges Materials

Answer 3

Depending on the method of fabrication:
Custom made
Preformed
Depending on the material available in preformed crowns:
Resin based
Metal based
Depending on technique of fabrication:
Direct technique
Indirect technique

Question 4

Materials available for temporary C&B

Answer 4

Polycarbonate.
Acrylic (powder/liquid).
Acrylic (light activated).
Composite(gun mix paste).
Composite(light activated).
Higher methacrylate (powder/liquid).

Question 5

Define Polycarbonates

Answer 5

These are pre-formed crowns (ready made) of polycarbonate polymers.
They have high impact resistance and can be cemented in the place with self-curing resin cement.

Question 6

POLYMETHYL METHACRYLATE SYSTEM (PMMA)

Answer 6

As self-curing polymer system (Powder & Liquid).
Powder : Polymethyl Methacrylate + Peroxide (Initiator).
Liquid : Methyl- Methacrylate Monomer + (activator).
Advantages:
Acceptable mechanical properties.
Good color matching.
Disadvantages:
Irritant monomer.
Polymerization shrinkage.
High exothermic reaction.

Question 7

EPIMINE RESIN is

Answer 7

Base (past) imines- terminated polymer + filler
Catalyst (liquid) aromatic sulphonate ester

Question 8

EPIMINE RESIN advantage and disadvantages

Answer 8

Advantage
Low polymerization shrinkage.
Low exothermic reaction.

Disadvantage
Low impact strength
Possible tissue hypersensitivity

Question 9

HIGHER METHACRYLATE RESIN is

Answer 9

Powder: Polymethyl methacrylate beads + peroxide
Liquid: Iso-butyl methacrylate + activator

Question 10

HIGHER METHACRYLATE RESIN advantages and disadvantages

Answer 10

Advantage
Low exothermic reaction
More flexible
Less irritant to the pulp

Disadvantages
High polymerization shrinkage
Low tensile strength

Question 11

Composite RESIN:
Available as

Answer 11

three paste system
Base paste : multifunctional methacrylic acid ester
monomer + fillers.
Two catalyst pastes :
1. contain initiator.
2. contain activator.

Question 12

None of the materials should be allowed to set completely inside
(on the prepared tooth) why ?

Answer 12

since the undergo setting contraction and produce an exothermic reaction (heat) which may be irritant the freshly cut vital dentin and pulp and the adjacent tissues.