Temporary Materials Flashcards by niamh ritchie

3 common temporary materials

PMMA
PEMA
Bis-acryl composite

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fabrication for PMMA

indirect

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fabrication for PEMA

direct/chairside

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fabrication for bis-acryl composite

direct/chairside

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duration for PMMA

long term

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duration for PEMA

short term

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duration for Bis-acryl composite

long term

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PMMA for crown / bridge?

short and long

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PEMA for crown / bridge?

singe crown

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Bis-acryl composite for crown / bridge?

short span bridges

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PMMA is

PolyMethylMethAcrylate (PMMA) eg Jet

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PEMA is

PolyEthylMethAcrylate (PEMA) eg Trim II, Snap

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Bis-acryl composite e.g.

Protemp4, Quicktemp

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UDMA is

UrethaneDiMethAcrylate (UDMA) eg Provipont DC

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feature of methacrylate monomer

NOTICE the single double bond next the CH2

CH2 = C(CH2)(COOCH3)

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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