W1: GIC Flashcards
What is GIC?
- The glass-ionomer (GI)= group of tooth-coloured restorative materials
- based on an acid- base reaction: polyalkenoic acid liquid + an aluminosilicate glass powder. - These components harden in a few minutes.
Summary:
- youngest material, 1970s, powder (glass particles, silicon, alumnium) + LIQUID (a group of acid)
-Acid base reaction= salt created
What is the main acid in GIC?
POLY CO acids (heaps of acid building blocks)
weak acidity bc of this structure, so it doesnt demineralise quickly
How does GIC set?
when mix, A-B rxn starts= setting
- glass bits + acid grp of (POLCA) interacts with metal ions on glass= forms salt
- glass does not dissolve, remains in material
- rxn on superficial, only on sf of glass bits, forming salt bridges (AKA silica hydragel)
Acid attacks glass, metal cations interact with acidic group= salt formation ONLY ON SURFACE, reaction rate of ions are diff (e.g. Calc interacts asap faster than aluminium)
What are the main stages of GIC setting?
- mix: acid + powder together
- reaction 3-6 mins= setting, when Ca interact to make salt (keep pt ~5 mins)
- maturation= when pt go home it is still hardening. aluminium ions interact with PA(polyCO acid)
Is the AB reaction instant? What should we do to protect GIC from?
NO reaction matures.
protect from water.
precise balance of water of material
need to protect material from losing or abs water
What types of GIC are there based on contents/ ingredients in it?
acid + power + RESIN = resin increases reaction rate (has 2 rxn, AB + polymerisation- monomers become polymers)
There are two general types of glass-ionomers available:
1. GIC – glass-ionomer cement
- exclusively for a material of an acid-decomposable glass + water-soluble acid = sets by neutralisation reaction.
- RMGI – resin-modified glass-ionomer
- glass-ionomer+ lil bit of resin, mostly HEMA (hydroxyethyl methacrylate).
- Setting reaction: AB +~ photochemical polymerisation.
- Additionally, in some materials, the
polymerisation of the resin component may
involve a chemical initiator mechanism
Is GIC resin vs GIC better?
resin is faster but toxic (less biocompatible- so can’t use on pulp= necrosis or inflammation)
Give an example of how GIC is being improved:
developed
Manufacturers always tryting to make better GIC
e.g. GIC + nanofillers (~composite material)
- Giomer: GIC + composite
Adv and Disadv of GIC
Adv
1. chemical bonding
2. Fluoride= stops caries
3. biocompatibility
3. Coefficient thermal extension: in mouth hot/cold, if material has diff CTE then teeth they will expand or contract… if mismatch will lead to stress. CTE close to dentine
Disad
1. not mechanical strength like in class 2 occlusal loading
2. unnatural look
3. water imbalance (resin)
4. takes long to set
GIC basics
powder + liquid mix as
AB reaction
over time
How does GIC adhere/ what is the process of it’s setting reaction?
Calc hydroxy ap + binds with acidic group= chemical bonding
and
secondary bonding
3-stage setting reaction:
1. Dissolution (glass decomposition)
2. Precipitation of salts; gelation and hardening
3. Hydration of salt (maturation)
When is F released in GIC?
in low pH, it increases pH when released= this is called buffering
benifits
1. buffers
2. turns in fluorapatite= caries resistant (but flurapatite can only occur few micons on sf of tooth, decrease uptake over time)
What is Biocompatibility vs Bioactivity of GIC
Bcomp= no necrosis
Bactive= antimicrobial, if ion rich layer formed on tooth sf and acts acid resistant by interacting with salive
not exam. What types of GIC are there based on application?
- cement/RCT
- fillings
- FS, liner, base, cement
this is didatic… now… we use
sometimes we can use it all as class 1,2,3
Detailed: Types of GIC based
Type I GICs - Luting and Bonding Cements
* Cementation (inlays, onlays, crowns, bridges,
orthodontic appliances)
* Root canal sealers
Type II GICs – Restorative Cements
* Type II1 for anterior
* Type II2 for posterior
Type III GICs – Fissure Sealants, Linings/ base Cements
* Liner or base under permanent restorations
When should you use GIC?
active carious lesion
1. chem bonding to DENTIN (other materials dont stick to dentin well)
2. you want F= anticariogenic (comps arent)
3. C1 & C2 fillings as long as pt doesn’t bite on it (non load), or when C2 has no adjacent tooth, if use in load bearing areas= ONLY TEMPORARY
4. can use in comp/amalgam
Explain the 5 indications for GIC
Example of sandwhich.
if gingival margin is sub= no enamel = OK
GIC can be used to elevate gingival margin= easier moisture control, occlusally/prox composite = sandwhich
Are GIC compatible with comp?
yep, GICR esp with composites
What is the ART technique?
probs we won’t do.
only in pt who have no dental care, use spoon excavator and place GIC
What must you do before apply GIC?
condition with acid. using same acid in material… or something more diluted.
removes smear layer and
expose clean dentine
What to do ASAP as mixing is over?
APPLY MATERIAL IN CAVITY
so that chemical bonding to HA of tooth
place too late then all acidic groups consumed nothing to interact with calcium HA of tooth.
Diff btw GICR vs GIC setting:
- GIC – “chemical (or auto) cure” mechanism (for a RMGI, this refers to the chemical component of the setting mechanism)
RMGI – dual-cure or tri-cure mechanism
- Cross linking of polymer chains takes place by two or
more of the following reactions.
- Acid-base reaction.
- Light-cure mechanism (in the presence of a photo-initiator such as camphorquinone.
- Oxidation-reduction reaction (resin auto-cure
mechanism).
LECTURE NOTES:
FUJI 2 LC
- LC= resin
- matrix placed gingivally and closed occlusally, to prevent excess
- you can overcure (avoid undercurve)
FUJI 9= general placement
- line, base, sandwhich,
- no resin= no LC
- conventional powder + liquid
- no LC so can use metal matrix
Both can be used for class 5
protective coating is used for GIC, why?
note: that matrix pictured is not used much
- water balance
- hydrophobic resin with no filler, GIC doesn’t like water so we use coat, LC coat
-If no coat, can use multipurpose adhesiove
How is water balance a disadvantage of GIC materials?
Water balance:
- Successful management of the water balance
(water uptake and water loss) of the glass-
ionomer material is probably the most significant
factor in ensuring long-term success with the auto-
cure cements. Approximately 24% of the set
glass-ionomer is water.
* Prolonged setting
* Setting contraction – 2-3%
At the beginning of a GIC reaction, which chains are formed? Describe the nature of this chain/initial setting.
- The calcium chains form first,
producing an early set= but are fragile and highly
soluble in water. - The aluminum chains form after= strong and insoluble + provide the major physical properties of the set restoration.
SUMMARY: MOA (acid-base reaction): poly (alkenoic acid) liquid + glass, => diffusion- based adhesion between the glass particles + the matrix.
How much therapeutic agent should be applied? What material is used?
deepest dentine + Calcium Hydroxide
Do you need a liner underneath a GIC filling?
No. Unless there is a deep part, spot apply calcium hydroxide then cover it with liner RMGI
NOTE: 3M™ Vitrebond ™ Liner/Base. 1. is a resin modified glass ionomer (RMGI) liner/base material, its composition and curing mechanism extensively described in the literature. It is recommend for use as a liner or base under composite, amalgam, metal and ceramic restorations.
There is a deep cavitation (no deeper than 1-2 mm from the
initially prepared pulpal or axial wall), do you line?
There is a deep cavity, should you line? Why so?
spot apply CH
RMGI
GIC
GIC are self adhesive, what does this mean?
bonds to our tooth :)
What was previous recommendation of GIC lining in amalgam restorations compared to now?
Where should you apply/not apply the GIC?
- dry dentine
- deepest part, cover mTA
- distant part
- dip 1/2 ball burnisher/ perioprobe into GI
-DONT use thick/dried up GIC
How is GIC bonding optimised?
How is GIs sensitive to moisture?
What are 2 clinical indications for GI use?
- dry when apply, wet when set
- polish on the day
