GIC’s Flashcards
Are GIC hydrophilic or hydrophobic
Hydrophilic
What is the Glass?
Calcium-Alumino-Fluoro-Silicate Glass
what is the reaction forming GIC?
acid+base reaction
acid = poly acid - usually polyacrylic acid
base = fluoride containing glass
Describe the process of the acid and base reaction
DISSOLUTION
- H+ from polyacid, COOH end of glass base
- displace + ions on glass surface
- e.g. Ca2+, Al3+ or F-
= glass has an ion-deficient layer
GELATION
- dispersed ions form bonds with negative COO-
= crosslinking
POST-SET HARDENING
- modified glass surface = polysalt matrix
What is the Maturation stage?
= continued formation of the polysalt
the Al3+ ions get displaced
precipitate for up to 24 hrs and at slow pace fo a year
what does too much water do to GIC
contamination
increase opacity
reduce hardness and strength
why is water important for GIC (4)
water slowly hydrates mature cross-linked matrix
- increase strength
- increase translucency
- increase resistance to dessiccation
what does too little water do to GIC?
cause dessication
- crazing and cracking
what happens to the calcium free ions?
bond to tooth surface and collagen in dentine through hydrogen bonding
what happens to the fluoride free ions
lie free within the matrix and released into surrounding tooth structure
initially released when acid attack - precipitate
slower release over time - remineralisation
How do you ensure cross linking happens
use a coating or varnish or bonding resin
3 PROS OF GIC - ABCF
Adhesive
Bond to collagen in dentine
Cariostatic
Releases Fluoride
ABCF
CONS OF GIC (5)
Technique and moisture sensitive
Can’t take a lot of stress
Low tensile and fracture toughness
Poor wear resistance
Average aesthetic
What is the main reason for replacing GIC
secondary caries
what is the medial survival time
2.5-3.5 years
What is GIC’s biocompatibility
favourable to soft tissue and pulpal response, plaque doesn’t thrive
BUT mild inflammation
where do we use GIC (6)
restore primary teeth
class III and V carious lesions
temp dressing
crown repair
cement rigid restorations
as a base under amalgam and composite
GIC have replaced cermets, why? (2 pros and 4 cons of cermet)
pros - resistant to acid, adhesive
cons - aesthetics, brittle, prone to abrasion, low coefficient to thermal expansion
what are GIC also known as
Glass Polyalkenoate Cement
why may viscous GIC’s be favourable (3)
higher powder:water ratio - less water
smaller glass particles
=== more packable and greater strength
why may viscous GIC’s be favourable (3)
higher powder:water ratio - less water
smaller glass particles
=== more packable and greater strength
how do you improve the adhesion of GIC?
remove the smear layer and clean tooth surface
use dental conditioner (10% polyacrylic acid) aka etching
wash after 20 seconds and dry
what is the smear layer
a thin layer of organic and inorganic debris compacted onto dentinal or enamel surface
What is Zinc Reinforcements Used and give 2 Uses
higher strength
no varnish or conditioner required
good for long term temp dressing, fissure sealant
