tooth coloured filling materials 2 Flashcards
what are examples of cements
GIC
light cured glass ionomer cement
compomer
composite
what can cements be
hydrophilic
or hydrophobic
describe glass polyalkenoates
formed as the result of a acid base reaction lion between fluoride containing glass and a poly acid- usually poly acrylic acid
they are adhesive
cariostatic
what is the composition of glass polyalkenoates
fluoro-alumino-phospho-silicate glass polyacid
eg polyacrylic acid or polymaleic acid
what are the disadvantages of poly alkenoates
technique sensitive moisture sensitive cannot be placed in stress bearing areas low tensile and fracture toughness poor wear resistance average aesthetics
what does adding a acid + base equal
salt + water
what are the steps of the setting reaction
decomposition migration gelation post set hardening maturation
how does the glass polyalkenoate bind to the collagen fibres
h+ ions
how does the glass polyalkenoate bind to the tooth surface
calcium ions and al3+ ions in a process called chelation
what happens in the maturation stage
al3+ salts precipitate for 24 hours
the setting process can continue for unto a year but very slowly
the formation of poly salts is continued
what happens to fluoride ions
not an integral part of the matrix and can be released without upsetting the structure of the cement
what role does water play
slowly hydrates the mature cross linked matrix
this leads to increase strength
improved translucency
increased resistance to desiccation
what can XS water lead to
CONTAMINATION
therefore increased opacity and decreased hardness
what happens if there is less water
desiccation
and more cracking and grazing
when are fluoride ions released
released by the acid attack from the glass
what does fluoride help with
biocompatibility of the material
inhibit recurrent caries
how does fluoride release
a rapid initial process
then a second slower much sustained process responsible for the long term release of fluoride
what is the advantage of fluoride
prevents secondary caries as it promotes remineralisation
it is also the main reason for GIC replacement
what does plaque not thrive on
gic
why does strep mutans not grow on GIC
due to fluoride being present
examples of alternative cements
diamondcarve
diamond 90
what is diamondcarve and diamond90 based on
based on glass and co polymer of
polyvinyl phosphoric acid
polyacrylic acid
give examples vicious glass polyalkenoates
fuji IX, ketac Molar, Hi Dense
describe vicious glass polyalkenoates
higher powder:liquid ratio
lower water content
smaller glass particles
used in ART technique
what is the survival time on posterior teeth of amalgam
median survival time 11 years
what is the survival time on posterior teeth of GIC
MEDIAN survival time of 6 years
deserve resin modified GIC
RMGIC are glass ionomer cements with the addition of a small quantity of resin components
what is the % of resin in set cement
4.5-6%
what are the advantages of RMGIC
tooth coloured
improved aesthetics
medium fluoride release
shorter setting
decreased moisture
improved tensile strength
sets on command
better wear characteristics
easier to use
higher bond strength to composite
fewer steps than composite
describe 2 modifications of conventional GICS
Less water can be used- it is replaced by a water/HEMA mixture called a vitremer
Modification of a poly acid with side chains that can polymerise by high curing mechanisms
what does the polymer also contain
polymerisable functional groups of COO and COOH which can be cured with blue light
what does HEMA stand for
hydroxyethylmethacrylate
disadvantages of HEMA
irritating to the eye and known contact allergen
how do we reduce the risk of allergic response to hema
minimise exposure
esp to uncured resin
clinically what is important when handling HEMA
protective gloves and no touch technique
what are the indications of RMGIC
cervical and root caries
base and abfraction lesions
what are the advantages of RMGIC in terms of cervical and root caries, as a base or in a fraction lesions
resistant to desiccation
can be contoured immediately
what is the composition of composites
bis-GMA UDMA EGDMA inorganic filler silane coupling agent uv stabilisers inhibitors
What is dyract
composition of dyract
Compomer
UDMA resin
TCB resin
strontium fluorsilicate glass
initiators
stabilisers
~~~
what are compomers made from
from from new monomers which contain acidic and acrylate groups
what does the setting mechanism 1st stage include in compomers
light curing induces the polymerisation of the resins
what does the setting mechanism 2nd stage include in compomers
after water uptake the acid base reaction takes place resulting in further cross linking of the matrix
pros of the setting mechanism in compomers
excellent handling
command set
good strength
cons of the setting mechanism in compomers
poor adhesion
low fluoride release
needs a bonding agent
what is the tensile strength of Fuji IILC
45 MPa
what is the tensile strength of VITREMER
75 MPa
what is the tensile strength of dyract
95 MPa
why do GPC restorations fail
due to recurrent caries
what % of GPC restorations fail due to recurrent caries
50%
describe chemfil rock
added zinc which makes it stronger tougher and earlier
no need to condition the cavity
no need to protect with varnish
describe new bioactive RMGIC
It chemically bonds to teeth, seals against bacterial microleakage, releases more fluoride and is more bioactive than glass ionomers, and is more durable and fracture resistant than composites
