37201 300x209 Glass Ionomer Cements

INTRODUCTION:

Glass ionomers was introduced by Wilson and Kent in 1972
First commercial aluminosilicate polyacrylate – 1 (ASPA-1) was tested by John Mc Lean.

DEFINITION:
According to skinners, glass ionomer is a generic name of a group of materials that use silicate glass powder and an aqueous solution of polyacrylic acid also known as poly alkeonate cement.

CLASSIFICATION
A] By Skinner
Type I: As luting cements
Type II: As restorative materials
Type III: Liners and bases
Type IV: Metal reinforced
Miracle mix
Cermet
Type V: Light cure GIC
Type IX: For geriatric and pediatric patients

B] By Wilson, Mc lean and Mount – based on application
Type I: Luting crowns, bridges and ortho brackets
Type II: Restorative materials (Cements) in low stress bearing areas
Type III: Pit and fissure sealants
Type IV : Metal reinforced

COMPOSITION:
POWDER LIQUID
SiO2 Polyacrylic acid
Al2O3 Water
AlF3 Copolymers – itaconic, Maleic acid
CaF2 Trycarbollic acids
NaF Tartaric acid
AlPO4

MECHANISM OF ADHESION:
Chelating of carboxyl groups of the polyacids with the calcium in the apatite of the enamel and dentin

BIOLOGICAL PROPERTIES:

Anticariogenic due to fluoride release
Biocompatible
Bond to enamel and dentin causing less secondary caries
PHYSICAL PROPERTIES:

Compressive Strength – 150Mpa

Tensile strength – 6. 6 Mpa

Knoop Hardness – 48

Solubility – 0.4
Advantages :
Cariostatic
Chemically adhesive
Tooth coloured
Biocompatible

Disadvantages :
Aesthetics not at par with composites
Early moisture sensitivity
Lower fracture resistance

Clinical procedure

~ Conditioning of tooth surface
~ Proper manipulation of the cement
~ Protection of the cement
~ Finishing of the cement
Recent Advances :

1. Metal modified GIC
2. Resin modified GIC
3. Poly acid modified Composite
4. Packable GIC
5. Flowable GIC
6. Self hardening RMGIC
7. Flouride charged GIC
8. Low pH ‘ Smart’ GIC
9. Bioactive glass
10. Fiber reinforced GIC
11. Giomer
12. Chlorhexidine impregnated GIC
Metal modified GIC

Developed in an attempt to improve the
mechanical properties of GIC.

Two types – Miracle mix ( by Seed & Wilson in 1980 )
- Cermet (by Mc Lean & Gasser in 1985 )

Uses -
core build up material
temporary posterior restoration
restorations in deciduous teeth
Resin modified GIC / Hybrid ionomers

Hybrid materials that set partly by acid base reaction &
partly by polymerisation reaction.

Powder – Normal glass particles, initiators
Liquid – Polyacrylic acid, HEMA, water

Setting reaction

2 types -
~ Dual cure
~ Tri cure
Advantages –
Longer working time
Reduced early water sensitivity
Tensile strength is higher ( 20 MPa )
Aesthetics better
Increased early strength
Can be finished & polished immediately

Disadvantages –
Polymerisation shrinkage Microleakage
Limited depth of cure in deep areas specially with opaque shades
Biocompatibility controversial

Uses –
Luting agent
Liner and base
Pit and fissure sealant
Core build up material
Repair material for amalgam
Retrograde filling material

Ex – Fuji II LC , Vitremer, Vitrebond
Polyacid modified composites/ Compomers

Material that contains both of the
essential components of GIC but at levels
insufficient to promote acid base reaction
in the dark.

Flouride release of GIC + Durability of composites

Composition – 2 component materials
dimethacrylate monomer Powder – strontium aluminium
carboxylic acid flourosilicate,
ion leachable glass (metallic oxides & initiators
no water Liquid – methacrylate monomers,
acrylate monomers & water
Setting reaction – 2 stages

Properties –
Adhesion – no chemical adhesion. Requires acid etching &
bonding.bond strength similar to composites ( 18 – 24 MPa )

2. Flouride release – reduced. Starts after 2 – 3 months.

3. Physical properties – better than conventional GIC

4. Aesthetics – at par with composites

Uses –
Pit and fissure sealants
Core build up
Repair of defective restoration margins
Class III and V cavities
Low stress bearing areas ( one paste system )

Ex – Compoglass
Packable / Condensable GIC

Developed as an alternative to amalgam specially for ART

Uses –
in ART
restorations in deciduous teeth
core build up

Advantages –
Rapid setting
Reduced moisture sensitivity Ex – Fuji VIII and IX
Solubility in oral fluids less Ketac molar
Non sticky and easy to place
Improved wear resistance.
Flowable GIC

Have low powder : liquid ratio

Better flow

Uses –
mainly as pit and fissure sealants
liners
sealing materials for hypersensitive teeth
Self hardening RMGIC

Purely chemically activated and no light activation required.

Composition –
GIC + monomers + benzoyl peroxide and amines.

Advantages –
easy to handle
no post cementation sensitivity
high compressive strength
no light activation required
significant flouride release

Use –
as a luting agent

Flouride charged materials

System has two parts –
restorative part
charge part ( gel )

Low pH ‘ Smart’ material

Episodic release of flouride specially in presence of
low pH in the oral cavity
Bioactive glass

Developed by Hench and coworkers in 1973.

Dissolution of glass by acid formation of a layer rich in Ca & PO4.

Gets fully integrated in bone ability to form intimate bioactive bond

Uses –
as retrograde filling material
perforation repair
implant cementation
infrabony pocket correction
bone augmentation
Fibre reinforced GIC

Developed by Dr. Lars Ehrnsford.

Also called PRIMM ( Polymer Rigid Inorganic Matrix Material )

Alumina and Silica fibres powder
( in the form of network or scaffold
which formed small chambers or spaces )

filled with resin after silanation.

Advantages –
reduced polymerisation shrinkage
increased wear resistance and flexural strength
increased depth of curing

Giomer
pre reacted glass particles ( made of flourosilicate glass which has been reacted with polyacrylic acid )incorporated into resin matrix

Properties –
Better aesthetics
- Optimal light diffusion
- Flouroscence of giomer similar to natural tooth
2. Flouride release – similar to GIC
3. Hardness – similar to enamel
4. Radio opacity – twice that of enamel

Uses –
Restoration of Class I, II, III, IV & V cavities
Core build up
Repair of # porcelain and composites.

Ex – Beautifil ( S – PRG )
Reactmer ( F – PRG )
Chlorhexidine impregnated GIC

To increase the anticariogenic action of GIC
Still under experimental stage.
Experiments conducted on cariogenic organisms.

  1. Compomers
  2. Are amalgam fillings safe?
  3. Pros and Cons of Different Dental Fillings
  4. Ingredients of Dental Fillings
  5. Composite vs Amalgam


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