Lecture - 09/16 - Provisional Materials

Question 1

What material sets via free radical reactions? Acid/base reactions? Both?

Answer 1

• free radical: composites
• acid/base: glass ionomer
• both: resin-modified glass ionomer

Question 2

What are the (5) common reasons that molar provisionals fail?

Answer 2

• isolation
• clinical crown height
• occlusal forces
• lateral interferences
• reuse of existing provisional at time of finalized prep

Question 3

What are the differences between the acrylics (Jet, Trim) and the BisAcryls in terms of chemical composition?

Answer 3

• acrylics: monomethacrylates

- BisAcryls: dimethacrylates

Question 4

What are the different properties of monomethacrylates vs dimethacrylates?

Answer 4

• monomethacrylates: linear chains (tough and soft)

- dimethacrylates: branched and crosslinked (brittle and hard)

Question 5

The change in density as a polymer forms is realized through ___.

Answer 5

shrinkage

Question 6

Which would shrink more: polymethyl methacrylate (Jet) or polyethyl methacrylate (Trim)?

Answer 6

polyMETHYL methacrylate (Jet) because it has a smaller side chain so it can pack closer together

Question 7

As the side chain length increases, polymer density ___, strength ___, Tg ___, and rigidity ___.

Answer 7

all decrease

Question 8

How is shrinkage reduced in polymers?

Answer 8

add fillers (PMMA and PEMA beads or silicate glasses)

Question 9

What is the composition of monomer liquid? Of powder?

Answer 9

MONOMER LIQUID:
- monomer
- inhibitors
- chemical initiators (1/2 of the component)
POWDER:
- polymer beads
- colorants
- chemical initiators (other half)

Question 10

___ dictate why you cannot mix liquids from one system with powders of another (ex. can’t mix Jet and Trim).

Answer 10

initiator systems

Question 11

Do BisAcryls have more or less shinkage than monomethacrylates (Jet/Trim)? Why?

Answer 11

less shrinkage because it uses higher molecular weight monomers (“oligomers”)

Question 12

What is the purpose of silicate glasses?

Answer 12

fillers that strengthen and give optical properties

Question 13

What are the (9) advantages of BisAcryls?

Answer 13

• good surface hardness
• good transverse strength
• easy to use
• low exothermic reaction
• low polymerization shrinkage
• good marginal fit
• good abrasion resistance
• minimal pulpal irritation
• good translucency and appearance

Question 14

What are the (6) disadvantages of BisAcryls?

Answer 14

• limited shades
• expensive
• brittle
• alteration and repair are difficult
• better stain resistance then methacrylates
• better color stability than methacrylates

*the last two seem like advantages? unless you want the provisional to be esthetically bad purposely?