L7: glass ionomer cement Flashcards
the “ glass in GIC refers to :
non crystalline glassy matrix
the “ ionomer” in GIC refers to :
ion crosslinked polymer
GIC is ____ based and ____ adhesive
water based self adhesive
filler in GIC :
Fluoroaluminosilicate glass powder
matrix of GIC:
Copolymer of carboxylic acid
how does GIC bond :
direct chemical bonding
special properties of GIC :
anti-cariogenic
can be used as bone substitute
biocompatibility of GIC?
Good biocompatibility but should be kept 0.5mm away from pulp
uses of GIC:
Type I luting cement
type II a : aesthetic restoration
type II b reinforced restorative
pit and fissure sealant
core build up ( resin and metal modfied)
prevention of carries
atruamatic restorative
liquid composition of GIC:
35-45% POLYACRYLIC ACID in water soultion : contains copolymers such as itaconic , maleic, tricarboxylic acid
uses of tartaric acid:
improves handling
decrease viscosity
increase working time
decrease setting time
GIC in relation to moisture?
should be protected using varnish because its sensitive
which component in glass particles is important for glass reactivity with polyacrylic acid?
aluminum
which 2 components of glass particles crosslink polyacrylic acid chain to form matrix ?
Ca and Al
Na and F particles do not participate –>
what happens to undissolved glass particles after dissolution of glass in liquid ?
undissolved particles are sheathed by silica-rich gel formed on glass
describe the 3 stages of GIC setting
-dissolution
-gelation
-hardening
dissolution :hydroxyl group (cooh) of polyacrylic liquid disolves glass particles —> releasing Ca Al F and Na partilces
gelation : gel is formed by cross linking of Ca and Al with liquid ( highly susceptible to moisture)
hardening : GIC gel transforms to hard material once Ca and Al ions complete initial crosslinking
what is the role of water in GIC setting ?
provide a reaction medium
if water came in contact with GIC during the gelation stage —> Ca and Al ions will be washed away —> becomes weak
disadvantages of conventional GIC:
low abrasive resistance
cannot be used for load bearing roles( inferior mechanical properties)
thermal properties of GIC are similar to___
dentine
what makes metal modified GIC different than the conventional GIC ?
Silver-tin metal alloy micro particles are incorporated in GIC powder( they do not bind with polymer matrix)
metal modified is weaker than conventional GIC
RESIN-MODIFIED GIC curing and available as :
either dual cure : acid/base+light
or tricure: acid/base + light + chemical)
capsule , 2 paste system , powder/liquid system
properties of resin modified GIC:
-releases fluoride
-higher bond strength than conventional GIC
-chemical adhesion
-high compressive strength
-HAS polymerizationshrinkage due to precense of resin
what is contradicted for resin modified GIC?
direct pulp capping
what factor can cause dimensional change of resin modified GIC?
DEHYDRATION
how is translucency of resin modified GIC different than conventional GIC?
it is reduced due to different refractive index of glass powder and resin matrix
compomer =
composite + GIC
Single paste , water free restorative
compomer composition :
non reactive filler particles
reactive silicate glass particles
sodium fluoride
polyacid modified monomer (diester of HEMA + cARBOXYLIC ACID )
setting reaction of modified GIC:
polymerization and absorbs water for slow acid/base reaction between acidic functional groups and silicate glass particles ( both self and light)
how does modified compomer bind to tooth :
most of them require a dentine bonding agent
resin cements are low viscosity versions of resin based composite
which form of curing results in the best color stability ?
light curing
special version of cement used for obturation to fill voids and promote seal , preventing micro leakage :
endodontic sealers
