Summary cards Flashcards
What is the composition of dental amaglam?
50% mercury
50% metal alloy
what is in dental amalgam alloy?
silver, tin, copper, zinc
what is silver and coppers properties in dental amalgam?
strength
what is tins properties in dental amalgam?
corrosion
what is zincs properties in dental amalgam?
deoxidiser - prevents oxidisation of other metals in the alloy
what happens to zinc in dental amalgam is contaminated with moisture?
it can expand
what is it called when amalgam is mixed?
trituration
what components are involved in the setting reaction of dental amalgam?
mercury and silver
what does dental amalgam setting reaction involve in?
3 phases:
Y
Y1
Y2
What is the Y phase of dental amalgam setting?
unreacted silver-tin alloy
what is the Y1 phase of dental amalgam setting?
strong silver-mercury matrix
what is the Y2 phase of dental amalgam setting?
weak tin-mercury
why is the Y2 phase of dental amalgam setting weak?
susceptible to corrosion and creep
what is creep?
deformation of amalgam under compressive stress
on trituration what are the dimensional changes?
30mins shrinkage
30-60mins
what is an advantage of corrosion products?
margin seal
when does dental amalgam reach its peak strength?
24 hours
what are the 2 alloy types for dental amalgam?
conventional
high copper
what percentage of copper differentiates types of amalgam alloys?
12%
why is high copper alloy better for dental amalgam?
doesnt result in Y2 phase = less corrosion and creep
what are the 2 types of dental amalgam alloy particles?
spherical and admixed (spherical and lathe-cut)
what are 3 advantages of a spherical alloy for dental amalgam?
easier to condense
stronger
sets faster
what is an advantage of an admixed alloy particle for dental amalgam?
better proximal contact
what minimum depth should amalgam be placed in?
2mm
how should dental amalgam be placed and filled?
in 2mm increments
overpack
carve back mercury layer
are enamel or dentin bonds weaker?
dentine
why are enamel bonds stronger than dentine?
enamel has more mineral content
enamel rods are parallel and more etchable
why has dentine got weaker bonds than enamel?
more organic matter and water
collagen fibres that are maze like
dentinal fluid
smear layer
what is used for acid etching?
30-40% phosphoric acid
how long do you leave acid etch on for?
15 seconds
what does acid etching do?
cleans surface debris and removes smear layer
widens dentinal tubules
what does enamel look like after it has been etched?
frosty white
what component of primer allows for a good bond?
HEMA
How does HEMA allow for a good bond?
infiltrates enamel prisms and dentinal tubules and WETS dentine to prevent collagen collapsing
what are the contraindications of HEMA in primers?
can cause allergic reaction on skin - contact dermatitis
What is the component of bond/ adhesive?
Bis-GMA
What does bond/ adhesive do?
chemically bonds to underlying primer and overlying composite resin
what is the key to great bond strength?
hybrid layer
what does the hybrid layer create?
mechanical interface between tooth and adhesive
what are resin tags?
extensions of primer into dentinal tubules
what is resin composite made of?
resin matrix (Bis-GMA) and glass filler particles (silica)
what is in resin composite that promotes adhesion between resin matrix and filler?
coupling agent
what does coupling agent do in resin composites?
coats filler particles to promote adhesion between resin matrix and filler
what makes resin composite radioopaque?
filler
what setting reaction does resin composite undergo?
polymerisation
what are the 2 pastes involved in self curing composite?
benzoyl peroxide (initiator)
tertiary amine (activator)
what component allows composite to be light cured?
camphorquione (photo initiator)
how strong does light need to be to initiate polymerisation?
468nm
What makes up a glass ionomer?
acid (polyacrylic acid)
base (aluminosilicate glass)
what are the good properties of glass ionomer?
self-adhesion to tooth
fluoride release
less overall shrinkage
what process makes glass ionomer self adhesive?
chelation
what are the bad properties of glass ionomer?
weaker
longer setting time
lack of control when setting
adding light curing resin to glass ionomer makes it a?
resin-modified glass ionomer
what setting reactions do resin-modified glass ionomers undergo?
acid base
free radical addition polymerisation
what ways can resin-modified glass ionomers be set?
light and/or chemical
what is vitrebond??
resin-modified glass ionomer liner
what are good properties of resin modified glass ionomers?
more rapid polymerisation
fluoride release
if a cavity is deep to pulp what would you use before vitrebond and why?
dycal as vitrebond is an irritant to pulp