temporary materials Flashcards
types of temp materials
PolyMethylMethAcrylate (PMMA) eg Jet
PolyEthylMethAcrylate (PEMA) eg Trim II, Snap
Bis-acryl Composite eg Protemp4, Quicktemp
UrethaneDiMethAcrylate (UDMA) eg Provipont DC
methacrylate’s monomer structure
with the C to C double bond,
enabling polymer development via cross-linking.
Polymerisation produces a long chain molecular structure or network - PMMA - yielding a material with greater weight, rigidity and strength.
PMMA e.g.: Jet
Powder/liquid formulation
Self-curing
Good marginal fit
Good transverse strength
Polishable
But
poor abrasion resistance
high shrinkage
high thermal release
free monomer may be toxic
chemistry of temp materials
these resins being considered undergo polymerisation after mixing - either a powder
and liquid; or two pastes
temperature safety when it comes to dental materials
The conclusion of this study was that:
an 11ºC rise in temperature most likely caused IRREPARABLE NECROSIS and
pulp death
even a 5.5ºC temperature rise caused significant histological change, which took 2 months for recovery, BUT not all pulps did increases of less than 5ºC did not affect pulp histology
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One factor the study didn’t account for was the DURATION of the heat stimulus – that’s bound to influence histological change in soft tissue.
driscoll and thermal trauma
DRISCOLL refers to the need for dentists to take necessary steps to minimise
the possibility of TM causing injury to oral tissues.
DRISCOLL also mentions gingival tissue not just pulp tissue as being at risk of thermal
trauma caused by the polymerisation reaction of these resins.
So the potential risk of TM causing harm has been known for some time.
properties you want to compare in temporary materials
Comparison of thermal responses - temperature rises
colour stability - coffee test
polymerisation shrinkage - lower is better
compressive strength - need to withstand biting forces
abrasion resistance - resist its surface being worn down - compared to amalgam - higher abrasion as its softer
surface roughness
ease of ise
working and setting time
