NAME- SK AZIZ IKBALDept. of Conservative

Dentistry & Endodontics

TYPES OF GLASS IONOMER CEMENT & IT's

ADVANCEMENTS

NORTH BENGAL DENTAL COLLEGE & HOSPITAL

Glass ionomer cement is a tooth coloured material, introduced by Wilson & Kent in 1972.Material was based on reaction between silicate glass powder & polyacrylic acid.They bond chemically to tooth structure & release fluoride for relatively long period.

DEFINITION Glass-ionomer is the generic name of a

group of materials that use silicate glass powder and aqueous solution of polyacrylic acid” -Kenneth J Anusavice.

Glass ionomer cement is a basic glass and an acidic polymer which sets by an acid- base reaction between these components”

JW McLean, LW Nicholson. AD Wilson (1994)

INTRODUCTIONINTRODUCTION

CLASSIFICATION

A.ACCORDING TO A.D. WILSON AND J.W.McLEAN IN 1988

Type I --- luting cements

Type II --- restorative cements

a.Restorative aesthetic

b.Restorative reinforced

B. ACCORDING TO PHILIPSType I – LutingType II- RestorativeType III- Liner and base

C. NEWER CLASSIFICATION Traditional glass ionomer a. Type I --- Luting cement b. Type II --- Restorative cements c. Type III --- Liners&Bases Metal modified Glass Ionomer a. Miracle mix b. Cermet cement   Light cure Glass Ionomer HEMA added to liquid  Hybrid Glass Ionomer/resin modified Glass Ionomer a.Composite resin in which fillers substituted

with glass ionomer particles b.Precured glasses blended into composites

D.ACCORDING TO CLINICAL USE AS: Type I- Luting TYPE II- Restorative Type III-Fast setting Liner/ Base Type IV- Pit & Fissure Sealant Type V- Orthodontic cements Type VI- Core build up material Type VII- Glass ionomer cermet cement(a. Silver

b.Gold) Type VIII-GIC for ART(Resin modified GIC) Type IX- GP GIC (Geriatric & Paediatric GIC)

E. ACCORDING TO STURDVENT:

1. Traditional or conventional 2. Metal modified GIC a. Cermet b. Miracle Mix 3. Light cured GIC 4. Hybrid (Resin modified GIC) 5. Polyacid modified resin composites

or Compomer

COMPOSITION

Powder :-Powder :-Acid soluble calcium fluroalumino silicate glass.Silica - 41.9%Alumina - 28.6%Aluminum fluoride - 1.6%Calcium fluoride - 15.7%Sodium fluoride - 9.3%Aluminum phosphate - 3.8% Fluoride portion act as ceramic flux. Strontium,Barium or zinc oxide provide radio opacity.

Liquid :-Liquid :-1.Polyacrylic acid in the form co-polymer with itaconic acid &

maleic acid .2.Tartaric acid: improves handling characteristic & increase working time.3.Water : Medium of reaction & hydrates the reaction products

SETTING REACTION

The acidic liquid solution (pH=1) dissolves portions of the periphery of the silicate glass particle,releasing calcium, aluminum, fluoride, silicon and other ions.

The calcium are chelated quickly bycarboxyl side groups on polyacrylic acid polymer

chains

Cross-linking of the poly acrylic acid chains takes place producing an amorphous polymer gel

During the next 24-72 hours, the calcium ions are replaced by more slowly reacting aluminum ions to produce a more highly cross-linked matrix that is now mechanically stronger

It is now believed that during the maturation involving aluminum ion cross-linking, silicon ions and unbound water participate in producing an inorganic co-matrix, best described as a hydrated silicate

The same carboxylic acid side group also are capable of chelating surface ions on the calcium ions from the tooth structure

The process generates true chemical bonds at all internal and external interfaces when the reaction conditions are correct.

SETTING TIMEType I 4 - 5 minutesType II 7 minutes

PROPERTIES

Compressive strength - 150 mpa

Tensile strength - 6.6 mpa.

Hardness - 49 KHN.

Initial solubility is high due to leaching of intermediate products.

The complete setting reaction takes place in 24 hrs, cement should be protected from saliva during this period.

Adhesion :- Glass ionomer cement bonds chemically to the tooth Glass ionomer cement bonds chemically to the tooth

structure.structure. Bonding is due to reaction occur between carboxyl

group of poly acid & calcium of hydroxyl apatite. Bonding with enamel is higher than that of

dentin ,due to greater inorganic content.

Solubility & Disintegration:-

Biocompatibilty :- Pulpal response to glass ionomer cement is favorable. Pulpal response is mild due to - High buffering capacity of hydroxy apatite. - Large molecular weight of the polyacrylic acid ,which prevents entry into dentinal tubules.

Esthetics :- GIC is tooth coloured material & available in different shades. Inferior to composites. They lack translucency & rough surface texture. Potential for discolouration & staining.

Anticariogenic properties :- Fluoride is released from

glass ionomer at the time of mixing & lies with in matrix. Fluoride can be released out without affecting the physical properties of cement.

Initial release is high. But declines after 3 months.

After this, fluoride release continuous for a long period.

Fluoride can also be taken up into the cement during topical fluoride treatment and released again ,thus GIC act as fluoride reservoir.

MM-GICGIC and-Metallic

fillers-Cermet

fillers CORES

GIC(Original

material)

CEMENTS

RR-GICGIC andResin fillers

ART-GIC &

TEMPORARIES

RM-GICGIC and-VLC hydrophilic

monomer and polymer

CEMENTS

COMPOSITE

CEMENTS FILLING

MATERIAL

COMPOMERVLC composite

and F source

FILLING MATERIALS

GIOMERVLC composite andPre-reacted GIC

powderFILLING MATERIAL

Summary of the historical evolution of Glass Ionomer Cements

The main shortcoming of GIC that limits its use in stress bearing areas is its lack of fracture toughness. To improve upon it metal reinforced GICs were developed.

They are mainly of two types:1. MIRACLE MIXTURE2. CERMET MIXTURE

METAL MODIFIED GIC

• Seed & Wilson (1980) invented Miracle Mixture: Spherical silver amalgam alloy+Type II G I C in ratio 7:1

• Mc lean & Gasser (1985) invented Cermet Mixture.

Miracle Mixture

•This is made by mixing of spherical silver amalgam alloy powder with glass ionomer powder.

•This combination became known as the miracle mixture because it was initially introduced during the early 1980s at the time when the mercury controversy was increasing dentists’ questions about the safety of amalgams.

•Miracle mixture was far inferior to those of amalgam, so it was not well received as restorative material.

•Main problem was that the matrix would not adhere to strongly to the silver- tin alloy particles

Cermet Mixture

CERMET MIXTURE: Ceramic-Metal Mixture

•To circumvent the previous mentioned difficulty, the silver-tin alloy particles were substituted by Silver-palladium(Ag-Pd), which generate passivation of oxide film of palladium oxide that is chemically reactive by chelation with polyacrylic acid.

•Stronger than unmodified glass ionomer cements but had poor esthetics.

•Used mostly as cores

• Indications: • Class I cavities in primary teeth• Core build up material• Lining of class II amalgam

restorations• Root caps for teeth under over

dentures• As a preventive restoration

• Contraindications: • Anterior restoration• In areas of high occlusal loading

Advantages: •Ease for placement•Adhesion to tooth structure and anticariogenic potential•Crown cutting can be done immediately•Increased wear resistance

Disadvantages: •Esthetically poor•Tooth discoloration•Rough surface•Reduced W.L and S.T

RESIN MODIFIED GIC(RMGIC)• To overcome low early strength and moisture

sensitivity

• Defined as HYBRID CEMENT that sets partly by acid base reaction and partly by polymerisation reaction (Mc Lean)

• Materials that are modified by the inclusion of resin, generally to make the them more photo curable (Nicholson)

• Usually light cured, less technique sensitive and may be finished at the time of placement.

• Esthetic – Superior than conventional GIC

• Because RMGIs are significantly stronger than traditional glass ionomers, they are recommended for class V restorations and can be used for class I and class II restorations in primary teeth

Advantages

• Long working time due to photo curing• Improved setting characteristics• Decrease sensitivity to water • Increase early strength• Finishing & polishing can be done immediately• Improved tensile strength. • Better adhesion to composite restoration • Increase fluoride release.• Repairable.

Disadvantages

• Biocompatibility is controversial • More setting shrinkage leading increase microleakage

and poor marginal adaptation

POLYACID MODIFIED COMPOSITE RESIN

• Also called as COMPOMER• Defined as : material that contain both the

essential components of GIC but in an amount insufficient to carry out acid base reaction in dark.

• They are developed to combine fluoride release of GIC and durability of composite

POLYACID MODIFIED RESIN COMPOSITE / COMPOMER

Properties • Adhesion –Micromechanical, absence of water thus no self

adhesion• Fluoride release minimal. • Physical properties better than conventional GIC but less than

composite.• Optical properties superior to conventional GIC. Uses

Pit and fissure sealant• Restoration of primary teeth• Liners and bases • Core build up material • For class III & V lesions • Cervical erosion / abrasion • Repair of defective margins in restorations• Sealing of root surfaces for over dentures• Reterograde filling material.

Contraindications

• Class IV carious lesions• Large areas of labial surfaces• Class II cavities where conventional cavity is

prepared• Lost cusp areas• Under full crown or PFM crowns. Advantages • Ease of use • Easy adaptation to the tooth • Good esthetics • More working time than RM GIC

FIBER-REINFORCED GLASS IONOMER CEMENTS• Incorporation of alumina fibres into the glass powder to

improve upon its flexural strength• This technology called the Polymeric Rigid Inorganic

Matrix Material or PRIMM developed by Dr. Lars Ehrnsford• It involves incorporation of a continuous network of

alumina and SiO2 ceramic fibresAdvantages:

• Increased wear resistance. • Improved handling characteristics• Increased depth of cure• Reduction of polymerization shrinkage• Improved flexure strength(50Mpa)

GIOMERTrue hybridization of GIC and composite . But here pre-reacted GIC powder is dispersed phase within compomer. Combine fluoride release and fluoride recharge of GICesthetic & easy polishableINDICATIONS

• Class I, II, III, IV, and Class V cavities• Restoration of cervical erosion and Root caries• Laminates and core build up• Restoration of primary teeth.• Repair of fracture of porcelain and composites

• To summarize the differences between the three

types of materials:

• Fluoride Release ability GICs>RMGICs>PAMCRs• Wear Resistance PAMCRs>GICs>RMGICs• Strength PAMCRs>RMGICs>GICs• Ease of Handling PAMCRs>RMGICs>GICs• Polishability and Esthetics PAMCRs>RMGICs>GICs

REFERENCESREFERENCES• Glass ionomer cement by Alan D.Wilson and

John W. Mclean

• Philips science of dental materials, 11th ed & 12th ed

• Sturdevant’s Art and science of operative dentistry, Fifth edition