Resin Based Composite Materials - basic system Flashcards by Hannah Maclean

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

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What is resin based composite composed of? (learn)

chemically active resin and inorganic filler bound together by a saline coupling agent

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What are the principal monomers in resin?

based on a chemical reaction of 2 resins: bisphenol A and glycidyl methacrylate

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What does bisphenol A and glycidyl methacrylate form?

bis-GMA

‘bowens resin’- the base of a lot of resin composites

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Can you mix and match materials from different manufacturers?

no, create a substandard restoration

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What is the problem with bis-GMA?

HIGHLY VISCOUS, CANNOT BE MANIPULATED CLINICALLY

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What do you call the monomers you add to bis-GMA to make it less viscous? (handles clinically)

diluent monomers / viscosity controllers

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What are examples of diluent monomers? (4)

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What happens to dimethacrylate when cured?

shrinks

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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

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What are the active groups at the end of dimethacrylate?

active methacrylate groups at either end of the backbone

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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

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What is incorporated into the rein to compensate for its short comings?

inorganic filler

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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)

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What metal is added to convey radiopacity?

barium salts

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What properties does resin composite take on?

properties of the main constituent - filler

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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?

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