Compomers Flashcards
What material have been termed hybrid materials?
compomers and resin modified glass ionomers
Why are compomers and resin modified glass ionomers termed hybrid materials?
they have both resin and glass ionomer constituents
What is the sequence of compomer, glass ionomer, resin modified glass ionomer and resin composite?
Why has compomers been developed?
in an attempt to combine the potential advantages of fluoride release as seen with glass ionomer cements with the advantages of resin composites
What is the main system of compomers?
primarily resin system
What are compomers manufactured without?
without the addition of water
Instead of water, what is incorporated into compomers?
resin
(difunctional)
Are resin composites hydrophillic or phobic?
hydrophobic, no water in the material at all
How do compomers differ from resin composites?
put an additional difunctional resin in there
become more hydrophilic, allow the uptake of water and promote the release of fluoride ions during its lifetime
What is the generic name of compomers?
polyacid-modified resin composite
What are the 2 resin components of the compomer?
contains 2 monomeric components:
1) dimethacrylate
2) difunctional resin monomer containing both carboxyl and methacrylate groups
can bind to hydrophobic and hydrophilic
What is the difunctional monomer?
TCB resin
What is TCB resin?
cross-linking reaction
reaction product of butane tetrecarboxylic acid and (HEMA) hydroxyethylmethacrylate
What is the most hydrophilic resin being used?
HEMA
What are the hydrophilic monomers? (examples)
glycerol dimethacrylate
What does the difunctional resin monomer do?
enhances water diffusion within resin matrix
What is the filler/ glass ionomer?
fluoro-alumino-silicate glass
What is the filler loading volume of the filler component?
43% and 67%
What are the photo-activators and initiators?
camphorquinone
tertiary amine
How many stages are in the setting reaction?
2 stage process
How is the resin part and glass ionomer part cured?
resin = LC
glass ionomer = chemical
What is the primary reaction?
LC
free radical polymerisation reaction
What is the secondary reaction in compomer setting?
occurs between the glass and the carboxylate groups of the difunctional resin
In the secondary reaction, what is formed?
polysalt matrix is formed around the glass (as conventional gic)
What aids the acid/base reaction in the stage 2?
by additions of small parentages of hydrophilic resin
What does addition of hydrophilic resin allow?
encourage diffusion of water within the resin and fluoride out
What is the secondary reaction?
acid/base
What is the polymerisation shrinkage as a percent by volume?
2-3.5%
What is needed for compomers to bind to tooth tissue?
an intermediate bonding system
Why cant you get the properties of the glass ionomer which bind to tooth surface well?
the components are bunged up in the resin matrix formed in the first reaction
it is more similar to resin composite
What is fluoride release dependent on?
secondary setting reaction
Is fluoride release slow or fast?
slow and steady
Is there an initial fluoride burst initially?
no
What is the concentration of fluoride within the restoration determined by?
determined by the secondary reaction of glass with the pendent carboxyl groups
this in turn is determined by their proximity to the reactive glass surface
Why is there limited ability for the reaction between the glass and carboxyl groups?
the resin phase of the system has already set
What reaction allows the fluoride o be released?
water uptaken, hydrogen ion reacts with the glass and fluoride is released
What permits the uptake of water?
addition of hydrophilic resin systems
When has the compomer fully set?
when the water sorption has occurred and the secondary glass filler/carboxyl reaction has completed
How long until saturation has occurred?
1 week of placement in the mouth
What is the concern of water sorption?
uncontrolled reaction, may lead to excessive expansion - damage to the tooth
hydroscopic expansion
Why is hydroscopic expansion actually a good thing?
primary reaction there is shrinkage, reduce the effect of polymerisation shrinkage
What is the effect of compomers uptaking oral fluids?
leads to discolouration of the entire restoration
What is the wear resistance like of compomers?
less wear-resistance compared to resin composites
When would you use compomers?
class III cavities
class V cavities
fissure sealants (flowable form)
luting of metal-based indirect restorations and orthodontic brackets (luting form for crowns)
restoration of deciduous teeth
Would you use compomers for cermaic crowns?
no, the expansion could break cermain crown
What cavities would you not use compomers?
class I, II, IV
not strong enough
Why would you not use compomers for inter-visit restoration of endodontic access cavities?
poor ability to seal as demonstrated with microleakage
How is the material presented?
compules, light tight, moisture tight
