GIC vs RMGIC Flashcards
what is GIC and its composition/setting?
glass/silica powder
tartaric acid / polyacrylic acid
Dissolution: silica powder and acid react. acid begins to dissolve the silica powder. Cations from the powder begin to leave the powder and into the surrounding medium.
Gelation: calcium bivalve to ions begin to cross link between carboxylic acid chains from the polyacrylic acid.
Hardening: Ca double crosslink matrix is replaced by trivalent aluminium ions.
what is dual cure RMGIC and its composition/setting?
Same as GIC with acid base reaction resulting in silica dissolution.
Light activation then initiates free radical addition polymerisation of the methylacrylate.
This creates a solid resin component.
Within solid resin component, the acid base reaction carries on for multiple hours to harden within the resin component.
where may you use GIC or RMGIC?
class 5 or 3 restorations
fissure sealants
cavity base / liners
temporary endodontic fillings
orthodontic cement
deciduous restorations
pros of GIC
low micro-leakage
high fluoride release
no contraction on setting
chemical bond to enamel and dentine
good thermal properties
once set; less prone to discolouration or staining compared to composite
cons of GIC
poor handling and wear resistance
moisture dependant, if water interacts then will set it early.
Swelling due to water content and uptake - decrease strength
brittle
poor aesthetically and translucency
Pros of RMGIC
less water sensitive (still a little due to HEMA)
good thermal properties
light curing
chemical bond to enamel and dentine
little micro-leakage
better aesthetics and translucency
fluoride release
cons of RMGIC
less fluoride than GIC
brittle and poor handling
monomer leaching can cause pulp toxicity from resin component
contraction on setting due to resin component
exothermic setting
water uptake due to hydrophilic HEMA
What is the setting for tri cure RMGIC?
Dissolution and acid attack as seen in conventional GIC
Redox reaction begins
Then photo initiation of the dimethylacrylate model through light curing.
Resin component sets
Redox carries on for around 5 minutes
Acid base carries on for multiple hours.
How does GIC bond to tooth tissue?
Pre-existing calcium in enamel forms cross links between carboxylic acid chains on polyacrylic acid.
How may GIC restorations fail? How can this be avoided?
Through contamination.
Aluminium ions may diffuse out of the GIC, excess drying may also result in water loss.
Saliva contamination too
All of these cause the GIC to weaken.
It can be avoided by covering the GIC restoration / liner etc with either a varnish, a resin or petroleum jelly.
