GLASS IONOMER CEMENT

PRESENTED BY : AADITYA MALLIK

ROLL NO. : 28

BDS 4TH YEAR

CONTENTSINTRODUCTION

CLASSIFICATION

INDICATIONS AND CONTRAINDICATIONS

COMPOSITION

SETTING REACTION

PROPERTIES

CLINICAL MANIPULATION

ADVANTAGES AND DISADVANTAGES

ADVANCES IN GLASS IONOMER CEMENT

CONCLUSION

REFERENCES

Glass ionomer cement is the generic name for materials based on the reaction of glass powder and polyacrylic acid.

Glass ionomers were first developed by Wilson and Kent in 1972.

Glass ionomers are water-based, self-adhesive tooth colored, anti-cariogenic restorative materials in which the filler is a reactive glass called fluoroaluminosilicate glass and the matrix is a polymer or a copolymer of carboxylic acids.

CLASSIFICATIONTYPE I - FOR LUTING

TYPE II - FOR RESTORATIONS

A. RESTORATIVE ESTHETICB. RESTORATIVE REINFORCED

TYPE III - LINERS AND BASES FURTHER CLASSIFICATION :

TYPE IV - FISSURE SEALANTS

TYPE V - ORTHODONTIC CEMENTS

TYPE VI - CORE BUILD UP

TYPE VII - FLUORIDE RELEASING GIC

TYPE VIII - GIC FOR ATRAUMATIC RESTORATION

TYPE IX - FOR PEDIATRIC PURPOSE

indications

a. Restoration of erosive/abrasive lesions without cavity preparation.b. Sealing and filling of occlusal pit and fissures.c. Restoration of primary teeth.d. Restoration of Class V carious lesions.e. Restoration of Class III carious lesions, preferably using lingual approach.f. Repair of defective margins in restorations.g. Minimal cavity preparations in a proximal lesions through buccal and occlusal approach (tunnel preparations).

CONTRAINDICATIONS

i. Class IV carious lesions (or) fractured incisorsii. Lesions involving large areas of labial enamel where esthetics is of major importance.iii. Class II carious lesion where conventional cavities are prepared, for replacement of existing amalgam restorations.iv. Lost cusp areas.

COMPOSITION

POWDER

SILICA41.9%

ALUMINA 28.6%

ALUMINIUM FLUORIDE 1.6%

CALCIUM FLUORIDE 15.7%

SODIUM FLUORIDE 9.3%

ALUMINIUM PHOSPHATE 3.8%

LIQUID

POLYACRYLIC ACID IN FORM OF COPOLYMER WITH

ITICONIC ACID

MALEIC ACID

TRICARBALLYLIC ACID

TARTARIC ACID

WATER

SETTING REACTION

Water serves as a reaction medium

The polyacrylic acid chains are then cross-linked by the calcium ions; however, over the next 24 hours, the calcium ions are replaced by aluminum ions.

Sodium and fluorine ions from the glass do not participate in the cross-linking of the cement.

When the powder and liquid are mixed for a GIC, the acid starts to dissolve the glass, releasing calcium, aluminum, sodium, and fluorine ions.

Some of the sodium ions may replace the hydrogen ions of carboxylic groups, and fluorine ions are dispersed within the cross-linked (matrix) phase of the set cement.

The cross-linked phase becomes hydrated over time as it matures.

The undissolved portion of glass particles is sheathed by a silica-rich gel that is formed on the surface of the glass particles.

Thus, the set cement consists of undissolvedglass particles with a silica gel coating embedded in an amorphous matrix of hydrated calcium and aluminum polysalts containing fluoride.

SETTING REACTION

MECHANISM OF ADHESION

Glass ionomers bond to tooth structure by chelation of the

carboxyl groups of the polyacrylic acids with the calcium in

the apatite of the enamel and dentin in a manner similar

to polycarboxylate cement.

The significance of water inglass-ionomer

Water plays a significant part in their setting reaction as well asin their final structure.

Water is the reaction medium into which the cement-forming cations –calcium and aluminium – are leached and within which they are transported to react with the polyacid to form a polyacrylate matrix.

It also serves to hydrate the siliceous hydrogel that surrounds the glass particles and the metal polyacrylate salts as they form the matrix.

Once the material is set the water content is arbitrarily classified as either ‘loosely bound water’ or ‘tightly bound water’.

PROPERTIES

MECHANICAL PROPERTIES

COMPRESSIVE STRENGTH – 150 Mpa

TENSILE STRENTH – 6.6MPa

HARDNESS - 40 KHN

FRACTURE TOUGHNESS – Inferior to composites

SOLUBILITY AND DISINTEGRATION

INITIAL SOLUBILITY – HIGH (0.4%)Complete setting reaction takes 24 hrs so , the cement

should be protected from saliva during this period.

ADHESION

Adheres well to enamel and cementum.

Chemical adhesion

ESTHETICS

Inferior to silicates and composites.

LACK Translucency and accumulate stain with time.

BIOCOMPATIBILITY

Pulpal response – mild

ANTICARIOGENIC PROPERTIES

Release of fluoride!

Fluoride recharging.

CLINICAL MANIPULATION

The following conditions for GIC must be satisfied :

(1) the surface of the prepared tooth must be clean and blotted dry,

(2) For luting purposes, the entire intaglio of the prosthesis must be coated with luting cement and seated completely,

(3) excess cement must be removed at the appropriate time.

GIC surface must be protected to prevent dehydration or premature exposure to saliva. Surface finishing of GIC restorations must be carried out without excessive drying.

Surface Preparation

Clean tooth surfaces are essential for sustained adhesion.

A pumice slurry can be used to remove the smear layer producedby prepared cavity.

Alternatively, the tooth may be etched with phosphoric acid (34% to 37%) or conditioned with an organic acid like polyacrylic acid (10% to 20%) for 10 to 20 seconds, followed by a 20- to 30-second water rinse.

After conditioning and rinsing the preparation, the surface should be dried but not desiccated and it must remain uncontaminated by saliva or blood.

Material PreparationThe P/L ratio recommended by the manufacturer should befollowed.

A paper pad or a cool, dry glass slab may be used for mixing.

The latter serves to retard the reaction and extend the working time.

The powder and liquid should be dispensed just beforemixing is begun; otherwise evaporation of water increases theacid/water ratio of the liquid.

Normally half of the powder is mixed into the liquid for 5 to 15 seconds; the rest of the powder is then quickly added and mixed by folding the cement on itself until a uniform, glossy appearance is achieved.Mixing time should not exceed 45 seconds.

GLOSSY APPEARANCE - the presence of unreacted polyacid, which is critical for bonding to the tooth,

DULL APPEARANCE - the acid has reacted too much with the glass particles for good bonding.

Placement of Material

A tooth cavity should be slightly overfilled with GIC restorative.

A freshly prepared glass ionomer mixture is hygroscopic,which means that it absorbs water from thesurrounding environment.

After placement, the GIC surface should be covered with a plastic matrix for about 5 minutes to protect the material from gaining or losing water during the initial set.

When the matrix is removed, the surface must immediatelybe protected with the varnish supplied with the GIC or with petrolatum while the excess GIC is removed from the margins.

Finishing is improved if the cement sets while protected, which lowers the risk of dehydration and the tendency to craze the surface, which would make the restoration more opaque.

ADVANTAGES

• Inherent adhesion to tooth structure because of chemicalbonding to enamel and dentin through ion exchange.

• Biocompatible because large sized polyacrylic acidmolecules prevent the acid from producing pulpalresponse.

• Little shrinkage and good marginal seal.

• Anticariogenic because of fluoride release. This fluoridecan also be recharged from topical fluoride applications.

• Good color matching and translucency makes it esthetic.

• Minimal tooth preparation required hence easy to useon children.

• Less soluble than other cements.

• Less technique sensitive than composite resins.

DISADVANTAGES• Brittle and low fracture resistance

• Low wear resistance

• Water sensitivity during setting phase affects physicalproperties and esthetics.

• Some newer products release less fluoride thanconventional GIC.

• Opaque which makes glass ionomer cement less estheticthan composites.

• Not inherently radiopaque.

• Require moisture control during manipulation andplacement.

ADVANCES IN GIC

METAL REINFORCED GIC

RESIN MODIFIED GIC (HYBRID IONOMER)

HIGH VISCOSITY GIC FOR ART

TRI-CURE GLASS IONOMER SYSTEM

NANOIONOMER GIC

GIOMER AND COMPOMER

CONCLUSION

No single type of cement satisfies all of the ideal characteristicsor is best suited for all indications in dentistry.

Each situation should be evaluated based on the pertinentenvironmental, biological, and mechanical factors.

Glass ionomer cements bond to tooth structure and releases fluoride.

The fluoride-releasing capability makes GIC the material of choice for the replacement of restorations that have failed because of secondary caries and for patients living in areas where fluoridated drinking water is not available.

REFERENCESAtlas of Glass-Ionomer Cements - A Clinician's Guide 3rd Edition (2001) - Graham J. Mount

Phillips' Science of Dental Materials (Anusavice) 12TH Edition (2012)

Craig’s Restorative dental materials 13th edition

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