mix Flashcards
what are the 2 types of amalgam?
conventional - 6% copper
high copper - 30% copper
what are the different forms of amalgam?
lathe cut
spherical
admixed
what compound takes place in the setting reaction of amalgam?
Ag3Sn
what chemical strengthens amalgam?
copper
what acts as a scavenger for oxygen in the set reaction of amalgam?
zinc
when is amalgam fully set and ready to be polished?
24 hours
how long do you have between placement and function of amalgam?
15-20 mins
how does corrosion of amalgam occur?
electromechanical interaction of different alloy phases with saliva as the electrolyte
what can corrosion products of amalgam provide?
a good marginal seal
what is creep?
when amalgam flows out of the cavity and protrudes at the margin
can fracture off and produce ditching
what component of amalgam is toxic to the CNS?
what can it cause?
mercury
MS
behavioral and psychiatric problems
how is excess mercury removed?
mercury rises to the surface during packing and condensation and is removed by carving
why are bonded amalgams used?
not enough tooth structure to give retention
complete marginal seal and prevent ingress of bacteria
what are advantages of amalgams?
reduced need to prep
no pins
reduced leakage and sensitivity at margin
what is the process of a bonded amalgam?
vitrebond lining
etch prime bond
rely x arc uncured
amalgam
when is an amalgam filling indicated?
poor moisture control large occlusal load missing cusp subgingival no enamel margins
what are some reasons for using a matrix band?
retain material in cavity
recreate a contact point
protect the adjacent tooth
what are the components of composite?
resin matrix fillers coupling agent pigments activator
what is in the resin matrix?
principle methacrylate monomers e.g BISGMA
dilutent monomers e,g TEGMA
what is the filler portion of composite?
particles of silica glass and barium oxide
aluminasilicate
borosilicate
what are the 3 types of composite?
hybrid
macrofilled/conventional
microfilled/nanocomposite
when does shrinkage of a composite occur?
polymerisation of the resin matrix
what component of composite might cause hypersensitivity?
HEMA
what depth of composite can be cured per increment?
up to 2mm
why cure the last composite increment under a cellulose strip?
removes oxygen inhibited layer
what is the action of TEGMA?
controls the viscosity
what is the coupling agent used and what is its function?
gamma silane
transfers stresses generated under occlusal forces from rigid filler to more flexible ductile matrix
what is the action of camphorquinone?
yields necessary free radicals to set off polymerisation
at 460-480 nm = visible blue light
readily generated by quartz halogen lamps
what are the differences between flowable and normal composite?
flowable has 50-60% less filler
low wear resistance
more shrinkage
dont use composite when?
high occlusal loading
RSC
poor moisture control
HEMA sensitivity
what lamps are used to set composite?
quartz halogen
LED
plasma arc - increased shrinkage
powder/Liquid GI, what are the components and how is it set?
sodium aluminasilicate and 20% CaF
aqueous solution of acyrilic acid copolymer and tartaric acid to control set
acid/base reaction
powder/water GI, what are the components?
sodium aluminasilicate and 20% CaF with vacuum dried polyacid
water or aqueous solution of dilute tartaric acid
what is the problem with hand spatulation of GI?
increased porosity because of air incorporation
how does GI bond to tooth? Bond to collagen?
- calcium ions
- H bonding and metallic ion bridging
how do you boost the bond of GI to tooth?
- citric acid - remove smear layer
- polyacrylic acid - boosts tooth bond
properites of GI?
brittle exothermic chem set brittle poor abrasion resistance acid erosion radiolucent F release
what is a cermet?
Ag pellized mix of glass and metal particles
poor appearance but better strength
what is a modified composite?
filler of composite is placed with aluminasilicate glass
encourages fluoride release
light cured
what is a giomer?
modified composite structure but aluminasilicate glass is pre reacted with a polyacd
what are the two setting reactions of a giomer?
surface reaction
full reaction
both VLC light cured
what is RMGIC?
ion leachable glass with methacrylate resin
polyacid, hema, water, chem activators, polymerisation activatos
what do RMGIC do in water?
expand
what are some indications for GI use?
abrasion and erosion cavities tunnel prep temp restoration deciduous teeth ART luting cement root caries
what are some indication for RMGIC use?
lining
base
sandwhich
what is the open sandwich technique?
RMGIC on occlusal floor
composite on top
what is the closed sandwich technique?
RMGIC on occlusal floor and pulpo axial wall
composite on top
what are the 2 pastes of CaOH? and how is it set?
- glycol salicylate
- Zno and CaOH
light set
what are some properties of CaoH?
high ph = bacteriocidal and beneficially irritant
insulates, radiopaque, compatible
what are some disadvantages of CaOH?
cant withstand condensation
no coronal seal
what are the components of Zinc polycarboxylate and what is its brand name?
- zinc oxide 2. aqueous solution of polyacrylic acid
Poly F
what are some properites of Poly F?
high mw = cant penetrate the tubules
F = bacteriostatic
Zn = bacteriocidal and radiopaque
insulates, strong, compatible
disadvantages of PolyF?
no coronal seal
not obtundant
what are the 2 pastes of zinc oxide eugenol? what is its brand name?
l = eugenol and olive oil p = zinc oxide and hydrogenated resin for reinforcement
what are some properties of Kalzinol?
slight irritancy is beneficial
zn = bacteriocidal and radiopaque
v. obtundant
what are some disadvantages of kalzinol?
no seal
not compatible
what are the components of zinc phosphate?
p = zinc oxide and other metallic oxides l = aqueous sol of phosphoric acid with buffers of aluminium phosphate and zinc phosphate
what are some properties of zinc phosphate?
low pH/low MW = highly irritant
zn = bacteriocidal and radiopaque
compatible
insulates
what are some disadvantages of zinc phosphate?
no seal
not obtundant
what is Vitrebond?
GI as a liner
what are some properties of vitrebond?
low pH/high MW = mildly irritant
F = bacteriostatic
insulates/strong/directly adheres = good seal/compatible
when to line a cavity and where?
if cavity over 2mm
pulpo axial wall and occlusal floor
what is an indirect pulp cap?
cavity within 0.5mm of pulp
calcium hydroxide and vitrebond
what is a direct pulp cap?
exposed pulp covered in calcium hydroxide or mineral trioxide aggregate
DRY WITH COTTON WOOL NOT AIR
what are the 3 forms of direct attachment?
micromechanical tags
chemical adhesion
complex adhesion
how does acid etch work?
selective decalcification of enamel prisms = allows tags for bond to flow into
what does acid etch increase?
surface roughness
surface energy - removes surface contaminants, micromech attachements, increase wetting
what are problems with dentine bonding agents?
dentine is hydrophilic, vital, covered in a smear layer and has organic and inorganic material
what are primers really and what do they do?
conditioners
acids - alter surface appearance and characterisitics
what are some examples of primers and how do they work?
maleic acid, oxalic acid, nitric acid, phosphoric acid
acid base reaction
create tags in dentine/demineralise up to 4 microns
what are coupling agents really and what do they do?
primers
do the sticking
bond hydrophobic material to hydrophilic dentine
HEMA
what are sealers?
flow into tubules and seal surface rich in methacrylate
BISGMA and HEMA
what is an example of a reversible hydrocolloid?
irriversible?
agar
alginate
what are alginate and agar both?
colloidal suspensions of polysacharides in water
what is agar?
complex polysachharide based on seaweed
borax gives body
sodium phosphate is a retarder
what are alginates/components?
sodium or potassium salt of alginic acid
calcium sulphate - calcium ions for linking
sodium phosphate - controls working time, limits availability of calcium ions
fillers
how does alginate set?
gels by cross linking of calcium ions
what is the gelation time of alginate?
spatulation time?
working time?
3-4 mins
1 min
30 seconds
what should impressions be disinfected in?
sodium hypochlorite 5-10 mins
actichlor - 10 tabs per 1 litre - 2 mins immersion
how are polysulphides set?
condensation polymerisation
what are the components of polysulphide?
base - terminal and pendant thiol groups, polysulphide prepolymer, plasticiser, inert filler
catalyst - lead dioxide, sulphur, inert oil
what are the concerns with polysulphides?
lead is a concern
bad smell and taste
how are condensation set silicones set?
by cross linking of hydroxyl terminated polydimethyl siloxane chains
what are the components of silicones (condednsation)?
- hydroxyl terminated polydimethylsiloxane chains and inert fillers
2 alkyl silicate. tin compound
what is the by product of condensation silicones?
alcohol
what are the components of silicone addition?
- fillers, liquid silicone prepolymer with some methyl as vinyl. chlorplantinic acid
- fillers. liquid silicone prepolymer. polydimethylsiloxane chains with some methyl as hydrogen
how is addition cured silicone set?
platinum catalysed set
what are the two components of polyether?
base = imine terminated prepolymer and inert filler catalyst = aromatic sulphonic acid ester with paste forming oils and filler
how are polyethers set?
cationic ring opening polymerisation
how is dental plaster made from gypsum?
heated to 120 degrees
how is dental stone made from gypsum?
steam 125degrees in an autoclave
how is densite made from gypsum?
boil in calcium chloride
as you move from plaster to stone to densite what happens to particle size and porosity?
reduced particle size and reduced porosity
gypsum may interact with what?
alginate
