Temporary Materials Flashcards
3 common temporary materials
PMMA
PEMA
Bis-acryl composite
fabrication for PMMA
indirect
fabrication for PEMA
direct/chairside
fabrication for bis-acryl composite
direct/chairside
duration for PMMA
long term
duration for PEMA
short term
duration for Bis-acryl composite
long term
PMMA for crown / bridge?
short and long
PEMA for crown / bridge?
singe crown
Bis-acryl composite for crown / bridge?
short span bridges
PMMA is
PolyMethylMethAcrylate (PMMA) eg Jet
PEMA is
PolyEthylMethAcrylate (PEMA) eg Trim II, Snap
Bis-acryl composite e.g.
Protemp4, Quicktemp
UDMA is
UrethaneDiMethAcrylate (UDMA) eg Provipont DC
feature of methacrylate monomer
NOTICE the single double bond next the CH2
CH2 = C(CH2)(COOCH3)
reaction of methacrylate monomer
Free radical addition polymerisation of methacrylate monomer
Polymethacrylate (PMMA)
- forms a long chain molecule PMMA
There can be hundreds of methacrylate monomer molecules bonded together
Jet is
temporary material product
PMMA
Jet (PMMA) properties
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
PMMA is a
mono-functional monomer (i.e. one C=C double bond)
linear chain like polymer
PEMA is
trim II, snap
based on ethyl methacrylate monomer
bis-acryl(ate) composite is
e.g ProTemp4, Quicktemp
bis-GMA monomer
bifunctional (i.e. 2 C=C bonds)
- 3D polymer network
urethane dimethacrylate e.g.
Provipoint DC
chemistry of temporary materials
polymerisation reaction
powder/liquid or 2 pastes (cartridge system)
then can be mixed and shaped to requirements
2 sources of information for DMS
Journals - peer-reviewed - trustworthy! Product literature* - detailed - objective? *common way for a GDP to assess products – though DATA is not always complete, NOR accurate!
types of DMS product literature
Brochures
- superficial
- “positive” presentation
- sales oriented
Web-sites
- info-rich – not always relevant re properties
Product profile
- scientific info…but not definitive!
- not often supplied for products
Eg 3M ESPE, Heraeus…
assessment of DMS
use (2 factors)
Quality of data
- in-house – biased potentially, commercially driven
- independent
(single study; review (may be out of date))
Competitive performance
- are rival products compared?
2 key properties to assess for temporary materials
temperature
colour stability
temperature importance in temporary materials
exothermic reaction
material encapsulates tooth prep
safety - DENTIST’S concern
- Need to be clinically harmless
- too much heat will potentially harm the dental pulp
safety issue, as pulp damage is to be avoided
colour stability importance in temporary materials
reason for the provisional is to protect eg crown prep. And the end goal is for an aesthetic replacement of the natural tissue.
Aesthetics
- Anterior teeth
PATIENT’s concern
temperature and dental safety
Link between thermal and pulpal damage
- duration
- temperature rise - bellow 11 is better
Clinical and histological evaluation of thermal injury to pulp
colour stability and temporary materials
Will the material remain aesthetic during its lifetime - which may be several months.
Coffee test:
- After three days immersed in coffee at 36° C,
- measure objectively with colorimeter
change in appearance is measured by the delta E value.
The chart shows ΔE for PROTEMP is 1.5, for Integrity it’s 1.6. And with the highest values we have TRIM and JET at 10.9 and 21 units of ΔE.
why is polymerisation shrinkage important for temporary materials
important for assessing a temporary material’s accuracy of fit
low polymerization shrinkage gives good clinical fit of the temporary restoration
can also measure marginal discrepancy
what does marginal discrepancy assess
polymerisation shrinkage
what sort of gap forms at the tooth-material interface?
why is compressive strength important for IM
TM has to withstand biting forces - as a permanent restorative material would.
more the material abrades
the more likely that a SURFACE NOTCH will be created
- plaque trap, rough sensation to patient’s tongue
more abrade = weaker compressive strength
other factors to consider when assessing TMs
Surface roughness (appearance)
ease of use
working and setting time
key properties required for TM (always look for when assessing product)
temperature reached during setting (thermal release);
compressive strength
colour stability
abrasion resistance
polymerisation shrinkage
