clinical aspects of composite Flashcards
understand chemistry look at clinical techniques understand shortcomings understand clinical indications
what is the chemistry of composite
matrix fillers coupling agents initiators and accelerators pigments
what is the composite called if it is just resin matrix
unfilled resin
what are the two viscous monomers
BIS-GMA
UDMA
what are the two diluents
TEGDMA
HEMA
what is step 1
resin matrix
what is a matrix
Phase that polymerizes to form a solid mass
what are the properties of matrix
absorbs water stains and discolours
least wear resistance
what does step 2 include
Silica particles
Quartz
Glass (Ba, Sr, Zr)
what is it called when composite is made of resin matrix and filler particles
filled resin
what are composites classified by
by filler size( micro filled and nano filled)
what determines the surface smoothness
filler size
what does the change in particle size lead to
the rougher the surface
what does an increase in filler content lead to
increase hardness/strength
increase abrasion resistance
handling
aesthetics
what happens as the filler content decreases
the resin content decreases
what is step 3
the coupling agent
what happens in step 3
the filler particle which is the inorganic matrix binds to the the resin matrix which in organic
what is organosilane known as
a bifunctional molecule
what does the silane end bond to
OH group of the filler particle
what does the methacrylate end polymerise to
polymerises to resin
what is step 4
Optical modifiers/Pigments
what do Optical modifiers/Pigments do
provide translucency and opacity
what do the Optical modifiers/Pigments tend to be
metal oxides of titanium dioxide and aluminium oxide
what is the colour shading chart we use for teeth
vita classical
what materials are radiopaque
boron or zinc
what do we need for a light activated composite- free radical activation
1.For light activated materials:
◦ Photo initiator - camphorquinone
◦ Amine accelerator (diethy-amino-ethyl-methacrylate)
◦ Polymerization inhibitor – hydroquinone (prevents setting during storage)
what are examples that give the right wavelength of light
blue light emitting diode
plasma arch light
argon laser
halogen light
what is the filler size of macro filled particles
8-12 micrometres
what is the filler size of small particle
1-8 micrometres
what is the filler size of hybrid
0.4-1 micrometres
what is the filler size of micro filled
0.04-0.4 micrometres
what is the filler size of nano hybrid
0.02-2.5 micrometres
what is the filler size of nano filled
culsters 0.06-1.4 micrometres
what is the disadvantages of composite
polymerisation shrinkage
technique sensitive- water control
doesn’t bond to a tooth- need a bonding agent
what is shrinkage
the development of gaps
what does shrinkage lead to
leads to sensitivity
secondary caries
staining
what do we need for moisture control
good gingival health
cotton wool rolls
rubber dam
Contra - Indications of composite
Where moisture control cannot be achieved • Subgingival restorations
• Composite polymerization is reduced in the presence of Eugenol (don’t use with ZoE)
Very deep restorations…pulpal irritation due to un set monomers…. (new materials/techiques/ place a linner).
what are the stages in the bonding phase
Total etch – etch enamel and dentine for 15 seconds. Wash off all acid for at least 15 seconds
dry- slightly for 5-10 seconds
what substance do we use to etch
37% phosphoric acid
what changes in enamel occur when etching has taken place
creates micro porous layer
increases SA
increases wettability
increases surface energy
what changes in dentine occur when etching has taken place
removes smear layer
unblocks and widens dentinal tubules orifices
exposes network of collagen fibres
what do we need to use when bonding
apply primer
thin by drying slowly
light cure for 20-30 seconds
what are bonding agents
chemicals that allow the composite to bond to teeth
the common used technique is 2 step-total etch followed by prime and bond
what is the hybrid layer
is the ’zone’ of resin interlocking with demineralised dentine surface. responsible for micromechanical bonding between tooth and resin
what wavelength of light is present in the light curing
450-490nM
benefits of composite
sets material when you want
disadvantages of composite
limited depth for curing only 2mm
what is the oxygen inhibition layer
glossy film of uncured resin
what can we use for tooth separation
Matrix strip and wedge
what can matrix bands and wedges stop
to prevent bonding two adjacent teeth together and to help shape proximal surfaces
what do we use to separate teeth on posterior surfaces
matrix bands
what do we do after the restoration and and polishing
finishing and polishing
what do we consider when finishing a tooth
removal of XS material and get the correct shape
what can we use to finish a tooth
finishing burs
abrasive discs
why do we polish a tooth
to get a high polish
what do we use to polish a tooth
soflex discs
abrasives such as polishing points
what are the different type of discs
course
medium
fine
superfine
what are interproximal strips
used for removing overhangs
Insert and use below contact area to maintain proximal contact
