Provisional Materials Flashcards
What are 4 types of provisional materials used in dentistry ?
PMMA.
PEMA.
UDMA.
Bis-acryl composite.
What type of reaction do provisional materials undergo on setting ?
Free radical polymerisation.
What is significant about provisional materials structure which allows free radical polymerisation ?
C=C allows for cross linking and formation of polymer.
Produces long chain network.
What does free radical polymerisation do to the properties of provisional materials ?
Increases strength and increases weight.
What is the initiator used in the free radical polymerisation reaction of provisional materials ?
Benzoyl peroxide.
What two types of cure can provisional materials undergo ?
Heat cure.
Self cure.
What are self cure provisional materials usually used for ?
Chairside single crown or short span bridge formation.
What two provisional materials are self curing ?
PEMA and bis-acryl composite.
What form do self curing provisional materials come in ?
Two pastes in mixing cartridge.
What provisional material is heat curing ?
PMMA.
What form does heat curing provisional materials come in ?
Powder and liquid.
What temperature do heat curing provisional materials need to be heated to for setting ?
73 degrees.
What can PMMA be used for ?
Indirect use for short and long span bridges.
What can PEMA be used for ?
Direct use for single crowns.
What can bis-aryl composite be used for ?
Direct use for short span bridges.
What are the four stages to PMMA setting reaction ?
- Activation - initiator to provide free radicals.
- Initiation - free radicals break C=C bonds.
- Propagation - growth of polymer chain.
- Termination - i.e. setting of material.
What are the 5 constituents of PMMA powder ?
PMMA particles.
Initiator - benzoyl peroxide.
Pigments.
Plasticiser.
Copolymers - improve mechanical properties.
What are the 2 constituents of PMMA liquid ?
Methylmethacrylate monomer - to dissolve PMMA.
Coploymers - improve mechanical properties.
What study was carried out to research exothermic properties of provisional materials ?
Zach and Cohen.
What did the Zach and Cohen study find ?
That degree of temperature increase and time of exposure to temperature increase are contributable to pulpal irritation and necrosis.
Zach and Cohen study: what was the effect on the pulp with +2 degrees increase on exothermic setting reaction of PMMA ?
No effect.
Zach and Cohen study: what was the effect on the pulp with +5.5 degrees increase on exothermic setting reaction of PMMA ?
56 days to overcome thermal trauma.
Small % of pulps of smaller teeth became necrosis.
Zach and Cohen study: what was the effect on the pulp with +11 degrees increase on exothermic setting reaction of PMMA ?
Irreparable damage to the pulp initiating pulpal necrosis.
Maximum exothermic temperature for temporary material to be used.
What are important properties of a temporary material ?
Temperature produced on setting.
Colour stability.
Compressive strength.
Abrasion resistance.
Surface roughness.
Polymerisation shrinkage.
Mean marginal discrepancy.
What is the manufacturer name for PMMA ?
Jet.
What is the manufacturer name for PEMA ?
Trim II.
What is the manufacturer name for bis-aryl composite ?
Protemp4.
What is the manufacturer name for urethane dimethacrylate ?
Provipont DC.
What monomer is present in Bis-acryl composite ?
BisGMA.
What is the difference between BisGMA and PMMA ?
BisGMA (liquid) monomer contains two reactive methacrylate groups (i.e. 2x C=C) forming 3D polymer network - cross linking agent used in composites and adhesives - better mechanical properties.
PMMA - made by polymerising mono-functional methyl methacrylate monomer (1x C=C) forming linear chain-like polymer - glass substitute due to transparency.
