GLASS IONOMER CEMENTS

INTRODUCTION

GIC is an adhesive tooth coloured restorative material used for eroded areas and now it has been used for other areas also .

Salt formed by reaction between poly alkenoic acid and Calcium aluminoflurosilicate glass .

HISTORY developed by Wilson & Kent in 1972 .

Yogi etal - 1992 – GI cement is used as a sealent for partially erupted permanent molars .

Groll etal – 1993 – Recommended light curable glass polyalkeonate for amalgam replacement .

Althadaing etal - 1994 – light cured glass ionomer for repairing furcated

areas on the pulpal floor .

Thevadans etal – 1996 – Mixing of 4 % NaF with GIC. .

Historical evolution of GIC

Also named as……

polyalkeonates .

ASPA (aluminosilicatepolyacrylic acid )

developed by Wilson etal 1970 .

.

ADVANTAGES

Tooth coloured material .

It will adhere directly to both enamel and dentine through ion exchange mechanism .

Biologically active as it is capable of releasing fluorides , calcium and phosphate .

CLASSIFCATION

CLASSIFICATION

TYPE I - Luting

TYPE II – Resoration .

TYPE III – Liners and bases .

TYPE IV - Pit and fissure sealants .

TYPE V – Orthodontic cements .

TYPE VI – Core built up.

CLASSIFICATION……

• TYPE I - Luting• TYPE II - Restoration• TYPE III - Liners & Bases• TYPE IV - Resin modified• TYPE V - Metal modified• TYPE VI - Ceromers• TYPE VII - Compomers• TYPE VIII - Geriatric• TYPE IX - Pediatric

CLASSIFICATION BY G J MOUNT

Based on the - water powder ratio. physical properties .

clinical application .

TYPE I – Luting agents .

TYPE II i – Esthetic restoration .

TYPE II ii – Non esthetic restoration .

TYPE III - Liners and bases .

CLASSIFICATION NO:3

TYPE I Conventional

TYPE II Restorative

Class 1 – esthetic restorative cements . Class 2 – reinforced restorative cements or metal

modified glass ionomer .

TYPE III Light cured lining glass ionomer cement

( liners and bases ) .

TYPE I –CONVENTIONAL GI.

Mostly used in cementing , luting , liners and bases .

Powder particle size – 15 micron .

Thickness of cement film – 2 micron .

Thin pulpal dentin is required to be protected with hard Setting Ca ( OH )2 .

TYPE II RESTORATIVE GIC

Class I esthetic restorative cement

Mostly used for anterior restorations

Class II reinforced restoration cements

Class I reinforced restoration cement ( metal modified ,

posterior GI)

Mostly used for posterior restorations .

A ) Amalgam alloys mixed with cements.

B ) Cermet ( ceramic metal mixture ) Glass powder is fused and sintered with Ag

particles .

PROPERTIES

Resistance to wear as they are stronger and tougher

.

Poor esthetics due metallic color

Less pulpal irritation .

Posses anticariogenic properties

TYPE 3 a – Light cured lining glass ionomer cements

HEMA ( hydroxy ethyl methacrylate ) added to light component .

Reduce shrinkage .

To increase strength , powder mixed with alumino – silicate glass.

Light cured GIC

TYPE 3 b – Light cured glass ionomer cement

COMPOSITION

POWDER - ion leachable glass .

LIQUID - Polyacrylic acid or

Polyacrylic acid with HEMA .

SETTING REACTION

Initial set – polymerization of methacrylate gp

Final set – slow acid – base reaction

PROPERTIES

Reduced translucency .

Increased tensile strength

Stronger adhesion to teeth surface .

Decreased marginal adaption and increased marginal leakage due to polymerization shrinkage .

TYPE 4 Hybrid resin modified G I

Used as restorative filling material.

HEMA added to liquid component - bonding.

Have higher resistance to wear & tear.

Used in class 1,2,5 filling with conservative cavity preparation.

Avoid cavities in deciduous teeth.

Light cured GIC

AVAILABLE AS… Powder – liquid system .

Pre – proportionate capsule .

Light cure system .

Dual cure system (chemical +light) .

Luting ,restorative & root canal cements

Cement dispensing system

COMPOSITION

POWDER

acid soluble calcium fluoro aluminosilicate glass

SiO2 -35-40%

Al2O3 -20-25%

AlF3 -1.5-3 %

CaF2 -15-20 %

NaF -4-10 %

AlPO4 -1-15 %

Fluoride component - ceramic flux .

Lanthanum , strontium,barium , ZnO- radiopacity .

Fine colloidal Ag and amalgam - enhance the properties.

LIQUID

40 -50% acidic solution……

Poly acrylic acid .

Tartaric acid .

Water.

Poly acrylic acid – very viscous Tendancy to gelation .

Poly acrylic acid co-polymerized with itaconic acid maleic acid .

Increases the reactivity of liquid .

Decreases the viscosity .

Decreases the tendency to gelation .

TARTARIC ACID

Improve the handling character . Decreases the viscosity . Increases the working time . Decreases the setting time .

WATER

Most important constituents . Too much of water- weak cement . Too little water – dehydration .

SETTING REACTION

The liquid acid may be freeze dried and combined with powder [ to have better shelf life and lower viscosity which are important characteristics for luting agents .

Mix can be done on a disposable moisture resistant paper pad or a glass slab .

A plastic spatula is preferred to a metal one to minimize contamination of the mix from eroded metal .

Large increment of powder are rapidly incorporated into the liquid and mixing should be completed within 40 sec Working time – short , not more than 3 min from start of mixing .

SETTING REACTION

Powder and liquid mixed together

Acid attacks the glass particles .

Na,Ca,Al ,F ions are leached into the aquous solution

Ca poly salts in the beginning and later Al – poly salts .

Two salts cross links to form polyanionic chain.

STRUCTURE OF SET CEMENT

Agglomerates of un reacted powder particles surrounded by silica gel and embedded in an amorphous matrix of hydrated Ca-Al polysalts .

Fresh cement once hardened is prone to cracking and crazing due to loosely bound water which is readily removed from mix .

Setting time – Type 1 4 – 5 min Type 2 7 min

STEPS IN GI RESTORATIO

N

• Cavity preparation • Conditioning of tooth preparation

• Proper manipulation

• Protection of cement from setting

• Finishing

CAVITY PREPARATION

Proper adhesion → resistance → retention is achieved by proper cavity preparation .

Eroded rough surfaces can be restored after acid etching alone without proper preparation.

CONDITIONING OF TOOTH PREPARATION

Chemical adhesion of cement with tooth surface .

Surface should be free of saliva, blood and completely dry .

Smear layer on the cavity should be removed .

This is done by Pumice wash 10 % polyacrylic acid 37 % H3PO4 Time 10 to 20 sec

Surface of dentin after application of……….

37% ortho phosphoric acid

10% poly acrylic acid

PROPER MANIPULATION

P/L ratio - type I 3:2 type II 3:1

Hand mixing

Capsule mixing

Divide the dispersed powder into two equal parts .

Powder is incoperated rapidly into liquid .

Mixing should be done in a folding manner in order to preserve the gel structure .

10 sec after adding first increment , 2nd increment is added to liquid .

The final mix should be with in 25 to 30 sec .

Hand mixing

CAPSULE MIXING

Amalgamator is used for mixing

Powder and liquid contained within capsule byremoving the seal separating the liquid and powder .

After mixing is completed by vibration nozzle of the capsule is pierced and the cement is dispersed directly on the prepared cavity .

Advantage

Control over p/l ration Convenience

Mechanical mixing

PROTECTION OF CEMENT DURING SETTING

Matrix placement

Matrix removal

MATRIX PLACEMENT

Pre contoured matrix is placed over the cement in the cavity for a period of 5 – 8

mts

ADVANTAGES

- Provide best possible surface integrity - provide maximum contour - prevent loose or gain of water from cement before initial setting is completed .

MATRIX REMOVAL

– After initial setting the matrix is removed. Excess material is removed by sharp hand instrument BP knife .-Cement then coated with: -light curable bonding agent -Vaseline

This prevent loose or gain of water . dehydrated restored cement become weak

due to microcracks.

FINISHING

Before dismissing the patient , apply one or more layer of protective agents .

GIC is not advised in patient with xerostomia , with mouth breathing habits (restoration are susceptible to dehydration) .

Occlusal caries on mandibular 1st molar

Caries excavation using spoon excavator

Completed caries excavation

CEMENT PLACED

Excess cement removed

Finishing done

LOSS OF GLOSS OR SLUMP TEST

USES

For luting

For restorations

Liners and bases

Fissure sealants

Orthodontic purpose

Core build up

Intermediate Restorations Adhesive Cavity Liners (Sandwich Technique) ART (Atraumatic Restorative Technique) Restorations for deciduous teeth

Luting Agents

Excellent for permanent cementation of crowns, bridges.

Releases fluoride reduces sensitivity by giving a firm foundation for composites.

Fast setting - low film thickness & low viscosity.

P/Lratio………… 1.5:1

Typical Physical Properties: Mixing Time: 15 seconds Setting Time: 2 minutes Working Time: 2 minutes

Luting agent

Orthodontic Bracket Adhesives

Most commonly used .

They bond directly to tooth by the interaction of Polyacrylate ions and hydroxyapatite crystals, thereby avoiding acid etching.

Anticariogenic effect - fluoride releasing ability.

Pit and Fissure Sealants

Cements were found to be unsuitable for use as sealnts if the fissures were less than 100µm wide.

The material is mixed to a more fluid consistency to allow flow into the depths of the pits & fissure of the posterior teeth.

Carious pit & fissures on mandibular molar

Conditioner applied

Placement of the cement

Liners and Bases

GICs have a number of advantages as cavity lining as they bond to dentine and enamel and release fluoride

-prevent decay & therefore minimizing the chances of appearance of secondary carries -promote the formation of secondary dentine.

They can be used as base for both composite resin and amalgam.

GIC as a Base ( P/L ratio-3:1)

Class III cavity preparation in 32

-Liner placed for pulp prottection

( P/L ratio – 3:1 )

GIC as a lining – 0.5mm thick

For Core Build Up

Silver containing GICs (cermet, Ketac Silver, Espe,GMbH or 'miracle mix' of GIC &unreacted amalgam alloy have been used.

Cermet used to fill deciduous teeth . Addition of Ag radiopacity to diagnose secondary

caries. To protect a GIC core crown margin should

completely embrace 1-2 mm of sound tooth structure cervically.

Extension of crown margin -ferrule effect

Advantages: to tooth Intrinsically adhessive Fluoride release - freedom from 2° decay Similar coefficient of thermal expansion

DEVELOPING A CORE

Intermediate Restorations

Due to inherent adhesive nature & brittleness

To restore loss of tooth structure from the roots of teeth [cervical abrasion cavity-product of over zealous tooth brushing]

Used frequently as in non-undercut cavities, to ensure their retention

Deep caries

Temporary restoration - GIC

Adhesive Cavity Liners (Sandwich technique)

Involves using GIC as dentin replacement and a

composite to replace enamel

Surface should be coated either with

an unfilled resin or a DBA to optimize attachment.

ART (Atraumatic Restorative Treatment)

The technique uses simple hand instruments

(such as chisels &excavators) to break through the enamel & remove caries

The cavity is loaded using cotton rolls.

Then residual cavity is restored using a modified GIC.

These GICs are reinforced to give increased strength under functional loads and are radio opaque.

Restorations for Deciduous Teeth

Due to high fluoride release ,minimal cavity preparation & adhesion to dental hard tissue.

Restoring carious teeth is one of the major treatment needs of young children.

And because they require a short time to fill the cavity, Glass ionomer cements present an additional advantage.

PROPERTIES

Film Thickness

The film thickness of GICs is similar to or less

than that of zinc phosphate cement and is

suitable for cementation.

MECHANICAL PROPERTIES

Compressive strength – 150 mPa

Tensile strength – 6.6 mPa

Hardness – 49 khn

The resin-modified materials have been shown to have significantly higher tensile strengths and lower modulus of elasticity than the conventional materials.

ADHESION

Good adhesion to enamel and dentin.

Bonding occurs between exchange of ions .

Some degree of bond is also developed between GI & collagen fibres of dentin.

Bond to enamel more than dentin , due to its high inorganic content and homogenesity .

ION EXCHANGE ADHESION BETWEEN TOOTH & CEMENT

AESTHETICS

Inferior to silicate and composite .

Lack translucency and have rough surfaces texture .

Rough surface texture .

Margin Adaptation and Leakage

The coefficient of thermal expansion of conventional GI is close to that of dental hard tissue- so good margin adaptation of GI restorations.

Shear bond strength of GIC doesnt approach that of dentin bonding agent, resin-modified GIC exhibit microleakage .

This may be partly because their coefficient of thermal expansion is higher than conventional materials, though still much less than composite

BIOCOMPATIBLITY

High degree of compatibility to living tissue

Polyalkenoic acid with high molecular weight is difficult to penetrate throught dentinal tubules .

Induce secondary dentin formation in mechanically exposed pulp .

In deep cavities Ca(OH)2 should be used to prevent post operative sensitivity .

RESISTANCE TO PLAQUE- Lack of plaque build up relative to adjacent

teeth

ANTICARIOGENIC PROPERTIES

GIC is considered as a fluoride reservoir

Remineralisation of tooth structure due to release of Ca , PO4 and F ions

Streptococcus mutans is unable to thrive in the

presence of F ions . so low accumulaton of plaque .

Minimize the white spotting and decalcification which is seen around orthodontic brackets .

Orthodontic bands on posterior teeth – luting agent of choice is GIC

FLUORIDE RELEASE

Fluoride re-uptake & release-after recharging with NaF gel

WATER BALANCE

Susceptible to both water loose and water uptake.

Type 3 cement remains susceptible to water uptake for at least one hrs to 25 hrs after placement.

Resin modified G I were developed to overcome this problem.

CLINICAL IMPORTANCE

GIC susceptable to dehydration should be coated with varnish during dental procedure .

Contraindicated in mouth breathers and xerostomia patients due to dehydration .

Failure to protect with matrix / varnish / resin bond agent will result in chalky / crazed surface .

Decreased P/L ratio gives chalky surface .

Liquid with PAA not to be refrigerated which increases viscosity.

DISADVANTAGES OF CONVENTIONAL GIC

Short working time

Sensitivity to moisture exposure

Dehydration during setting.

Lower cohesion strength.

Less resistence to abrasion and wear than composite .

MODIFICATION OF GIC

Resin modified GIC .

Metal modified GIC .

Fast setting materials .

Water settable GIC / anhydrous .

Compomers .

RESINMODIFIED GIC

Cement are light cured by adding 5% resin matrix to GIC .

They also retain the acid – base reaction .

RESIN MODIFIED GIC

COMPOSITON

Ion leachable glass ( fluoro alumino

silicate glass )

Polymerisable resin.

Photo initiator or chemical initiator or both .

LIQUID PAA

H2O

Methacrylate monomer .

Hydroxy ethyl methacrylate monomer (HEMA) .

The acid base raction will continue even in the absence of light activation .

Clean lesion with pumice & water

• Condition with 10% poly acrylic acid for 10sec

Apply pressure during placement to minimise porosity & good

wetting of the tooth

Trimming & contouring under air – water spray

PROPERTIES

Microleakage more than GIC due to

polymerization .

Good anticariogenic property due to increased F content.

Pulpal response mild .

Good esthetics .

USES

Class 1

Class 2

Class 5

For repair of cavities .

Class V non carious lesion restored with RMGIC

METAL MODIFIED GIC

Miracle mix Cermet

CERMET

Filler particles are added…………

To improve Strength

Fracture toughness

Resistence to wear

CERMET REPAIR ON BUCCAL CUSP OF BICUSPID HAS BEEN IN PLACE FOR

6years & APPEARS STABLE

Metal modified GIC

MIRACLE MIX

Also called silver alloy admix .

Spherical amalgam alloy powder mixed with type II GIC .

Not used in anterior teeth – due to radio opacity and metallic color .

Miracle mix

CERMET

Ag particles are bonded to glass particles by sintering ( fusion at high temp)

USES

Alternative to amalgam and composite .

In core build up in grossly destroyed teeth .

PROPERTIES

Excellent anticariogenic property due to F ions.

More resistance to wear than GIC.

Poor esthetics –radiopaque and gryeyish in color. .

FAST SETTING MATERIALS

Glass in these cements has been chemically modified during manufacturing to decrease the Ca2+ content and thus limit the production of Ca-poly alkeonate chains which are highly water soluble .

Faster maturation of setting reaction .

Decrease the translucency .

WATER SETTABLE GIC (ANHYDROUS)

Polyacrylic acid co-polymer is freeze dried and coated to powder particles.

The liquid part is water or water with tartaric acid.

When powder is mixed with water the polyacrylic acid goes in to solution to form liquid acid.

Cements undergo chemical reaction.

Cements set faster than normal cement.

Have improved physical properties.

COPOMER (POLYACID MODIFIED RESIN )

Hybridisation of composite and glass ionomer

Composite + ionomer = copomer

Variable degree of dehydrated polyalkenoic acid incoperated with filler .

The setting reaction is light activated .

Subsequent absorption of water from saliva into restoration will release small amount of fluorides

Adhesive system is based on acid etch or resin bond system and no ion exchange adhesion.

Used in children.

Have minimal steps in placement.

Aesthetically pleasing.

Finished case

TUNNEL RESTORATION

First discribed in 1963

Conservative alternative cavity preparation in primary molars.

Indication Small proximal caries with out involvement of marginal ridges

SANDWICH TECHNIQUE

GIC is sandwiched between tooth and composite resin.

Used in case of deep carious lesion.

ADVANTAGE Etching avoided in deep caries- avoid pulpal irritation. Better strength is achieved . Prevent recurrent caries due to F ion release . Chemical bonding to tooth achieved by GIC .

Closed sandwich restoration

Open sandwich

restoration

Lamination with amalgam

• Combination of GIC with amalgam• To with stand heavy occlusal load.• STEP –I , A strong GI base(auto cured

or resin modified) is applied first.• Fine layer of 45% poly acrylic acid

applied over cement – ensure chemical bonding.

• STEP II , Pack amalgam over this.• Mechanical interlocking occure

between two

STEP II……………

…………STEP I

CONCLUTION….

• No one material is universal and it is unlikely that such an ideal material limitations, bt each one , used to its full potential , has aplace in restorative dentistry.there have been 20years of close clinical observationof GIC

Text book of pedodontics - Shobha Tandon

• Preservation &restoration of tooth structure - Graham J Mount

• Text of pediatric dentistry - S.G.Damle

• Pediatric dentistry,infancy through adolescence• - Pinkham • Dentistry for the child & adolescent - Mc Donald,Avery,Dean

• Sturdevant”s Art & Science of Operative Dentistry

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