Resin Based Composite Materials - basic system Flashcards
What is resin composite material?
materials made of 2 or more constituent materials with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components
tooth coloured restoration
What is resin based composite composed of? (learn)
chemically active resin and inorganic filler bound together by a saline coupling agent
What are the principal monomers in resin?
based on a chemical reaction of 2 resins: bisphenol A and glycidyl methacrylate
What does bisphenol A and glycidyl methacrylate form?
bis-GMA
‘bowens resin’- the base of a lot of resin composites
Can you mix and match materials from different manufacturers?
no, create a substandard restoration
What is the problem with bis-GMA?
HIGHLY VISCOUS, CANNOT BE MANIPULATED CLINICALLY
What do you call the monomers you add to bis-GMA to make it less viscous? (handles clinically)
diluent monomers / viscosity controllers
What are examples of diluent monomers? (4)
What happens to dimethacrylate when cured?
shrinks
What is the effect of a log backbone on dimethacrylate?
longer backbone, the smaller the shrinkage as the reaction only occurs at the active methacrylate groups
What are the active groups at the end of dimethacrylate?
active methacrylate groups at either end of the backbone
If resin is used alone, what does the material exhibit? (shortcomings)
high shrinkage
inadequate wear
increased exothermic reaction
poor mechanical properties
inadequate optical properties
no radiopacity
What is incorporated into the rein to compensate for its short comings?
inorganic filler
What are the benefits of adding filler to the resin component?
increased strength
increased wear resistance
reduced polymerisation shrinkage
improved optical properties such as colour, fluorescence and translucency
less heat production during polymerisation (filler acts as a heat sink)
reduced thermal expansion (closer to tooth)
What metal is added to convey radiopacity?
barium salts
What properties does resin composite take on?
properties of the main constituent - filler
What are the disadvantages top the filler component being added to resin composite?
mechanically become more brittle - due to glass or ceramic
decreased capacity to withstand flexion during function as its modules of elasticity is increased
How can resin composiotyes be classified?
filler type
size of filler particles
mode of cure
type of resin
presentation
What are the 2 filler types?
glass or ceramic
Describe the glass filler?
amorphous (non-crystalline) solid material
What are types of glass filler?
quartz
silicate
barium, strontium and lithium
strontium-containing glasses
What are the features of quartz glass filler?
hardest but not radiopaque
What are the features of silicate glasses?
contain barium but are slightly softer and degrade very slowly when exposed to water
What are he features of barium, strontium and lithium containing glasses?
they are easier to finish and exhibit an improved surface finish
What type of glass filler degrades the fastest in water?
strontium-containing glasses
therefore a small percentage of the overall content used
How much more dense is the glass compared to resin?
glass is about 4 times that of the resin
Describe ceramic fillers?
inorganic, non-metallic solid prepared by the action of heat and subsequent cooling
What synthetic material do ceramic fillers contain?
zirconia-silica filler
- round edges, good translucency and more filler can be incorporated
zirconium oxide (zirconia)
What type of composite is used?
nanohybrid composite
Under ideal conditions, how can packing be substantially improved?
resin acting as a binder
What is the ideal distribution of packing to achieve an optimum filler loading is called what?
trimodal distribution
What is a hybrid composite?
lots of micro and macro filler molecules, so they fill all the spaces, reduce the amount of resin in there
What are nanofilled composites?
nanomers are discrete non-agglomerated and non-aggregated particles of between 20-70 nanometers
What are the benefits of nanofilled hybrids?
act as a single unit enabling high filler loading and high strength
strength of hybrid material but are easier to polish as the individual filler particles are much smaller
What are nanofilled hybrids?
conventional hybrid materials with nanoparticles added to fill inter-particular space - nanohybrids
most of the products are nanohybrids
What is the relationship between resin and filler?
put as much filler in as possible but still have sufficient resin to bind the filler together and hold it all together to minimise weaknesses
Does bonding occur between resin and filler?
no
What is needed to bond resin and filler?
silane coupler
What is the specific name of the silane coupler?
y-MPTS
How does silane coupler work?
bi functional
hydrophilic groups react with the inorganic filler
hydrophobic groups react with the organic resin
Where do crack initiation sites occur?
interface between the resin and filler
Where do fatigue fractures occur?
occur as the resin does not have a high resistance to crack propagation
