Glass Ionomer Cement Flashcards
components of GIC
acid [polyacid]
powder [base, metal]
acid composition
polyacid
polyacrylic acid - ionic monomer
tartaric acid - added to control setting characteristics
powder composition
silica, alumina, calcium fluoride, aluminium fluoride, aluminium phosphate, sodium fluoride
strontium and lithium salts increase radiopacity
3 phases of setting reaction
dissolution, gelation, hardening
dissolution setting reaction
acid into solution, H+ ions attack glass surface, Ca/Al/Na/F ions released, leave silica gel around unreacted glass
gelation setting reaction
initial set due to Ca2+ ions cross linking with polyacid
material appears ahrd in the mouth
hardening setting reaction
trivalent aluminium increases crosslinking
fromation of aluminium polyacrylate
important - setting reaction
must be protected from moisture and desiccation [hardening phase]
if not, aluminium will leach out, less crosslinking, saliva contamination, = WEAK MATERIAL
protecting GIC
must be protected after placement
can be by varnishes, resins or gels/greases
properties of GIC
good - bonds to enamel/dentine, fluoride releasing, no contraction on setting, seals well, low microleakage
bad - poor strength, ok aesthetics, poor compressive/tensile strength, high solubility, bad wear resistance
how does GIC bond to tooth tissue
carboxyl groups in cement bond to Ca in enamel, hydrogen bonding occurs
must be conditioned and not etched, with polyacrylic acid
uses of GIC
dressing, fissure sealant, luting, orthodontic treatment, base/lining, restoration
