DMS summary - pros Flashcards
What types of PMMA are there
- heat cure
- self cure
- Light cure
What is the difference between heat cure and self cure in terms of their compositions
Self cure is same as heat cure except benzoyl peroxide is activated by a promoter in the liquid
What is in the heat cure powder
- Benzoyl peroxide (initiator)
- PMMA particles
- Plasticisers
- Pigments
- Co-polymers
What are the constituents of liquid in PMMA
- Methacrylate monomer
- Inhibitor (hydroquinone)
- Co-polymers
How does PMMA set
- Free radical addition polymerisation
What are the 4 stages of free radical addition polymerisation
- Activation
- Initiation
- Propagation
- Termination
What are the two mixing stages for PMMA
sandy
dough
What happens if PMMA is not cooled down slowly
- will result in internal stresses which reduce the mechanical properties
What happens if PMMA is undercured
- will have poor mechanical properties and irritate the patient’s mouth due to free monomer
What is the cause of gaseous porosity
monomer boiling
Where is gaseous porosity generally seen
- Will see this in bulkier parts e.g next to the teeth
What is contraction porosity due to
polymerisation shrinkage
What are causes of contraction porosity
- Too much monomer
- Insufficient excess material
- Insufficient clamp pressure
What is the cause of granularity
too little monomer
What is crazing (PMMA)
- when the material is not mixed properly and can happen when different manufacturers are mixed together
