Composite resins Flashcards
What are the three types of components every compost has
Resin Matrix, Inorganic filler, and coupling agents
What (in general) makes up the resin matrix
monomer, initiator, inhibitors, pigments
How do the inorganic fillers affect cmpsts
creates strength, more filler ore strength
How can composites be classified
by monomer type, or filler particle type
What are two types of monomers
Methacrylate
silorane
What are the 4 types of compost particle
macrofil, microfilm, hybrid, nano
What do monomers due?
binds filler particles together providing workability.
What kind of money is sometimes mixed in with BisGMA to lower viscosity
TEGMA
What are the three steps of polymerization
Initiation
propagation
termination
What happens during initiation
chemical, light, or heat stimulus produce reactive free radicals
what happens during propagation
monomer units going due to free radical to form polymer network (think dominoes falling)
yields 50-60% conversion
Whats the average shrinkage noted with polymerization
1-6%
what is a good % by weight for composites..% by volume
50-86% by weight 35-71% by volume
what features give your composites less wear?
Smaller partial size to decrease abrasion
heavier filled to decrease attrition (large chunks breaking off)
non contact areas
less restoration surface area
restoration in anterior v posterior
higher cure
what do coupling agents do?
chemically bond filler particles to matrix
transfers stresses overal strength increases
what are the advantages of using light activation
longer working time
greater polymerization
reduced porosity
better color stability
what is the disadvantage to using a light cured resin
limited depth of cure
what are the two chemicals used in chemical activation
initiator-benzoyl peroxide
activator tertiary amine
Where do the radicals attack during polymerization
double carbon bonds of the resin
microfil have what particle size
40-50nm
nano composites have what particle size range
5-100nm
what are the micro hybrid particle sizes
.6 - 1 microns plus 40 nm particles
How does particle size affect polishability
smaller particles finer polished
do microfilms have a coupling agent
no, so inferior properties
also radiolucent
ok for class 5
Z250 is what class
microhybrid
what coupling agent do nano composites use
silane
what kind of filler distribution do nano composites have
broad with high loading increasing stregnth
What aspect of nano composites increases polish retention
addition of nanometer filler particles
Filtek supreme ultra is what % by weight filled
78%
What are the two types of filler particles in Filtek Supreme Ultra
nanomers .02-.07 microns
nano clusters the act as single unit
.6-1.4microns
controlled clinical studies say what when comparing wear of micro hybrid and nanofil
no sig difference in wear after 5 years but nanofil maintained a better polish
Whats the difference between nano composites and nanohybrid
composite has just nanometer sized particles throughout matrix whereas hybrids also have conventional fillers like sillica
What composite has the best flexural strength
Z250
whats a drawback of Z250
higher polymerization shrinkage 3%
how does composite clinical behavior comapre
limited studies
short observation times
large differences not easily demonstrated
What is a newer developed monomer that supposedly decreases shrinkage
Silorane
What is silorane
a ring monomer that opens during reaction.
uses camphorquinone and iodonium salt initiation
does shrinkage matter?
Clinical study showed no advantage between siloxane v methacrylate in 5 year study
Why are flowable composites flowable
less filler content and less viscous monomers (TEGMA)
How do flowables compare to hybrids
mechanical properties are less and polymerization shrinkage is higher
Do liners under direct composites improve marginal integrity or reduction of post op sensitivity
no clinical evidence for either
Can flowables be used in class one preps
Controlled clinical studies showed no difference at two years between flowable and a nano fill similar results for class 2 restorations
do self adhesive flowables work
less shear bond strength than etch/adhesive
How does heating affect composites
reduces viscosity but doesn’t seem to affect other properties
when testing depth of cure what must be the hardness of the deepest level to be considered cured
80% of top hardness
how does depth of composite affect cure
deeper composites attenuate the light decreasing the cure (same with darker shades)
what happens to cusps deflection with bulk placement
Increased due to C factor, but this may not be clinically significant
which type of fill has been shown to contain greater porosity: Incremental or bulk
Incremental
what properties might increase depth of cure for a composite
increased translucency, additional photo initiators, just more photo initiators
what is sonic fill
Single step bulk fill, using trigger sided cure can get up to 5mm, sonic activation decreases viscosity but its expensive
How do stress reducing monomers work
use fragmenting monomers that can break during polymerization reducing the stress on the prep.
Are bulk fill flowables a definitive restoration
No, Require covering by a restorative composite. they are very translucent.
overall lack of clinical studies
what are some advantages of dual cure composites
unlimited depth cure
less stress (but greater shrinkage) due to slower cure
less porosity because its bulk fill
equivocal fracture toughness
What are some disadvantages of dual cure bulk fill composites
color stability. Amines can discolor over time
its incompatible with simplified bonding agents
2x microleakage
what was the northern lights consensus statement on light cured bulk fill composites as far as advantages
may reduce placement time
may reduce air voids
may have stress reduction
what was the northern lights consensus statement on light cured bulk fill composites as far as disadvantages
may need more than one increment depending on depth
need supplemental cure from buccal and lingual
learning curve
may not be as esthetic due to translucency
are composites bio comparable to the pulp
yes with good seal
are there allergic reactions to composites
rarely with hema
any cytotoxicity of composities
maybe but short lived so not a chronic source
from a biocompatibility standpoint why is degree of cure important
decreases free monomer.
Whats BPA
Bisphenol A
Acts like estrogen
disruption in animal hormone activity but role in human hormone yet to be determined
BPA and dental resins
BPA used to make most resins
salivary enzymes breakdown bis dma
detected in saliva and urine in minute amount
overall much less than consumer item
how can reduce boa exposure
rubber damn
remove air inhibited layer
study of BPA urinary concentrations
Transient increase in BPA concentration that was no longer detectable at 14 days
ADA position onBPA
unwanted concern
