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By;Mhmood M.H. Radhi

BDSFinal year

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Glass ionomer cement is a tooth coloredmaterial, introduced by Wilson et al in 1970.

It can be used as luting cements or liningunder another restoration or as restorativematerial.

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I. For lutingII. For restoration

III. For liner & bases

Type II.1 Restorative esthetic

Type II.2 Restorative reinforced

Type

Type

Type

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Powder :-It is an 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%

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

& malic acid .2.Tartaric acid: improves handling characteristic

& increase working time.3.Water : Medium of reaction & hydrates the

reaction products

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When the powder &liquid are mixed,Surface of glassparticles areattacked by acid.then Ca, Al,sodium, & fluorideions are leachedinto aqueousmedium.

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Calcium ion cross-link the poly acrylic acid chains,

This forms a solid mass.In next phase, aluminum also begins to cross-link

with poly acrylic acids chains.

Water plays an important role in structure ofcement. Initially it serves as the medium, later itslowly hydrates the matrix.

The unreacted glass(powder) particle is covered bya silica gel.

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The set cements consists of agglomeration of

unreacted powder particles surrounded by a silica gelsheath and embedded in a matrix of hydrated calciumand aluminum cross-liked poly acrylic gel.

The exposure of cement to water before hardening is

complete, leads to loss of cations and anions whichform a matrix as they can be dissolved.

Thus it is very important to protect the cement surfaceafter its placed in the mouth e.g. by applying a varnish

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Initial solubility is high due to leaching of intermediateproducts.

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

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Biocompatibility :- The GIC show high degree of compatibility with living

tissue.Pulpal response is mild due to

- High buffering capacity of hydroxy apatite.

- Large molecular weight of the polyacrylicacid ,which prevents entry into dentinal tubules.

Anticariogenic properties :- Fluoride is released from glass ionomer at the time ofmixing & lies with in matrix.

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1.Preparation of tooth surface :-

2.Proportioning & mixing :- Powder & liquid ratio is 3:1 by wt. Powder & liquid isdispensed just prior to mixing.First increment is incorporated rapidly into the mix withstiff bladed spatula.Mixing done in folding method to preserves gelstructure.

Finished mix should have a glossy surface.Stiff mixing spatula is preferred.

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3. Protection of cement during setting :-GIC is extremely sensitive to air and water during

setting.It should be protected from moisture as well as dryingduring setting for few days.

4. Finishing :-Excess material should be trimmed from margins.Hand instruments are preferred to rotary tools to avoidditching.

Further finishing is done after 24hrs.

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5.Protection of cement after setting :-

Before dismissing the patient ,restoration is againcoated with the protective agent to protect trimmedarea.Failure to protect for first 24hrs results in weakencement.

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Adhesive Esthetic Fluoride releasing

Disadvantages :- Susceptible to erosion and wear brittle

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1.Anhydrous GIC :-Liquid is delivered in a freeze dried form ,which isincorporated into the powder.Liquid used is clean water.

2.Resin modified GIC:-Powder component consist of ion leachable

fluroalumino silicate glass particles & initator for lightcuring.

Liquid component consist of water & poly acrylic acid with methacrylate & hydroxyl ethyl methacrylatemonomer.

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4.Compomer :-

Compomer is a composite resin that uses an ionomerglass which is the major component of glass ionomeras the filler.

Small quantity of dehydrated polyalkenoic acidincorporated with filler particles,Setting reaction is light activated.

Adhesive system used with compomer is based on acidetch found with all composite resin.

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Resistance to fracture is one of the main limitationof using GIC. It is generally quite satisfactory forone-surface lesion but a two surface lesion isalways at risk.Resistance to abrasion and wear is little less thancomposite resin.They also remain susceptible to dehydrationthrough out lifespan, so that pt. with dry mouthshould not have restoration with GIC.

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Text book of pedodontics, Shoba Tandon, 2 nd edition .Dental material book, John J.M. 3 rd edition.

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THANK YOU