Resin Composites 1 Flashcards
What are Silicates
earliest tooth coloured restorative material
what si the reaction to get a silicate
acid base reaction (=salt and water) between
aluminosilicate glass and phosphoric acid
what are some properties of silicate
releases fluoride
moisture resist
erosion prone
brittle
what do acrylics come as
powder:liquid
what is the setting reaction for acrylics
free radical addition polymerisation chemical set so working time limited
what is the power used to make acrylics
Pmma beads
chemical initiator
pigment
what si the liquid used in acrylics
Mma monomer chemical activator (tertiary amine)
What are the steps assc with the free radical addition polymerisation recation
activation
initiation
propagation
termination
how does termination of free radical addition polymerisation come about
attatch to impurity/free radical or further growing chain
what happens to the material when polymerisation takes place
contracts
exothermic
what happens when tertiary mania not all used up
poor colour stability (clear-brown)
what are acrylics like compared to silicate
less prone to erosion less soluble less brittle less acidic lower thermal diffusely
how can acrylics irritate the pulp
due to residual Mma
interaction with eugenol
what was introduced to acrylics to reduce the shrinkage
inert filler particles to reduce shrinkage
what does a basic composite contain
BIS GMA matrix
coupling agent
filler particles
what is a resin composite
combination of two comically different materials have props together couldn’t alone
what si the modern way of curing
light cuming for command curing
what is the BIS GMA matrix
methacrylate based
comonomer such as TEGMA
what does th matrix do
controls the viscosity (TEGMA)
inhibitors
what is the viscosity of the matrix polymer do
reduces mobility of unreacted monomers
unreacted monomers means what
chair side repair
C=C takes part in free radical addition poly
in new products siloranes what happens in setting
ring opening
= initial expansion overall contraction
what are some examples of siloranes
siloxanes - hydrophobic
oxiranes - ring open poly
what are some points about cationic curing used for silorane
camphorquinone iodimum salt electron donor ring open poly less shrinkage
what is camphorwuinone
photosensitised
what does the electron donor do in cationic curing
decomposes iodiumum salt to an acidic cation
what are some fillers
quartz
silica
glasses ( aluminosilicates, boro silicate, barium oxide)
what is a common coupling agent
(delta- meathacryloxypropyltimethoxysilane)
what is the properties of coupling agent
difunctional
methacrylate characteristics
silane interacts and bonds with glass
good wetting
what are the means of chemical activation for rein comps
chemical
- powder liquid
- paste liquid
- encapsulated
what is the means of light curing for resin comps
UV not any more
camphorquinone
- protects eyes
what does camphorquinone do
yields necessary free radicals for poly
visible in blu light
what does the coupling agent do
tranfers stresses generated under loading form rigid and brittle filler to more flexible and ductile polymer matrix
filler may be added as a
shock abs
what are types of resin composites
microfilmed
conventional
hybrid
nancomposites
what are some handling characteristics
packable
- v viscous
flowable
- more fluid less filler
what is a type 1 restoration
restroe cavs involving occlusal surfaces
what is a type2 restoration
restore cav medial/distal ad occlusal surface
what is triboloy
changes with function and loss of resin rich outer layer
what sit he thermal property proportional to
to filler content
as filler inc coif of thermal expansion dec
what is mechanical dept on
filler content type and type
efficiency of coupling
degree of porosity
does cav shape influence overall success of restoration
yes
c = no. bonded surfaces/ no. unbounded surfaces
