lecture 5 & 6 - glass ionomer cements (slides)

8/4/2019 Lecture 5 & 6 - Glass ionomer cements (Slides)

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Direct estheticDirect estheticrestorative materialsrestorative materials

Glass ionomer cementsGlass ionomer cements



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DEFINITIONDEFINITION

Self Self --cured, tooth colored, fluoridecured, tooth colored, fluoridereleasing restorative materials thatreleasing restorative materials that

bond to tooth structure without anbond to tooth structure without anadditional bonding agent.additional bonding agent.



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CLASSIFICATIONCLASSIFICATION

Luting agentsLuting agents

Restorative material (erosion/abrasionRestorative material (erosion/abrasionlesions in permanent dentition, andlesions in permanent dentition, and

restorations in primary teeth)restorations in primary teeth) Liners and basesLiners and bases

Core buildCore build--up materialsup materials Pit and fissure sealantsPit and fissure sealants



GlassGlass

Three main components:Three main components:

Silica SiOSilica SiO22

Alumina Al Alumina Al22OO33

Calcium fluoride CaFCalcium fluoride CaF22

In addition to sodium and aluminiumIn addition to sodium and aluminiumfluorides, and calcium or aluminumfluorides, and calcium or aluminumphosphates.phosphates.

Components are fused at high temperatures,Components are fused at high temperatures,shock cooled then ground to a powder.shock cooled then ground to a powder.Particle size depends on applicationParticle size depends on application



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LiquidLiquid

Liquid: coLiquid: co--polymers of polymers of

polyacrylic acid and waterpolyacrylic acid and water E.g. of copolymers used:E.g. of copolymers used:

Acrylic acid and itaconic acid Acrylic acid and itaconic acid

Acrylic acid and maleic acid Acrylic acid and maleic acid Viscosity of the liquid depends on Viscosity of the liquid depends on

molecular weight and polyacidmolecular weight and polyacid

concentration.concentration.

Tartaric acid influences workingTartaric acid influences working

ad setting timead setting time

Ref. Introduction to dental materials



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DISPENSINGDISPENSING

2 bottle system hand mixed:2 bottle system hand mixed:

PowderPowder LiquidLiquid

Anhydrous cement: powder (glass and freeze Anhydrous cement: powder (glass and freeze

dried polyacid) and distilled waterdried polyacid) and distilled water

Capsules (preCapsules (pre--measured powder and liquid)measured powder and liquid)

mixed using a triturator (mixer). Easy to use,mixed using a triturator (mixer). Easy to use,GIC is directly dispensed into cavity, eliminateGIC is directly dispensed into cavity, eliminate

errors from manual mixing.errors from manual mixing.



8Ref. Phillips science of dental materials



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Setting reactionSetting reaction

Acid base reaction. Three overlapping Acid base reaction. Three overlapping

steps:steps: DissolutionDissolution

GelationGelation HardeningHardening



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SETTING REACTIONSETTING REACTION

Powder and liquid are mixedPowder and liquid are mixed::

Calcium, aluminium and fluoride from theCalcium, aluminium and fluoride from the

glass particles releasedglass particles released Calcium will crossCalcium will cross--link the polyacrylic acidlink the polyacrylic acid

chains.chains.

Calcium will be gradually replaced byCalcium will be gradually replaced by

aluminium over the next 24 hours.aluminium over the next 24 hours.

Role of water?Role of water?

Role of sodium and fluoride?Role of sodium and fluoride?



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Continue,Continue,

Gelation of cement: 2Gelation of cement: 2--3 minutes after3 minutes after

mixing, cannot be manipulated.mixing, cannot be manipulated. Next minute, the material hardens, butNext minute, the material hardens, but

setting and maturation goes on forsetting and maturation goes on forseveral hours.several hours.

Finishing is postponed until after 24Finishing is postponed until after 24hourshours



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Dissolution:Dissolution: Acid attacks the glass. This Acid attacks the glass. This

releases calcium, aluminum, sodium andreleases calcium, aluminum, sodium andfluoride. All is left is silica gel.fluoride. All is left is silica gel.

Gelation:Gelation: free calcium react first withfree calcium react first withcarboxyl groups in the acid leading tocarboxyl groups in the acid leading toinitial setting. At this stage contaminationinitial setting. At this stage contamination

from outer environment may lead to:from outer environment may lead to: Loss of aluminum ionsLoss of aluminum ions

Water lossWater loss The end result is a weak unaestheticThe end result is a weak unaesthetic

materialmaterial



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ContinueContinue

Hardening: can take as long as 7 days.Hardening: can take as long as 7 days.

Aluminum ions provide the final strength Aluminum ions provide the final strengthof the matrix (aluminum salt bridges). Inof the matrix (aluminum salt bridges). In

addition, water is bound to silica gel.addition, water is bound to silica gel.

End result: glass particles eachEnd result: glass particles each

surrounded by silica gel in a matrix of surrounded by silica gel in a matrix of

crosslinked polyacrylic acidcrosslinked polyacrylic acid



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SETTING OF GICSETTING OF GIC

Ref. Introduction to dental materials



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PropertiesProperties

Handling characteristics: previous versionsHandling characteristics: previous versions

of GIC had problems with inappropriateof GIC had problems with inappropriateworking and setting time. Tartaric acidworking and setting time. Tartaric acid

inclusion resulted in:inclusion resulted in:

Tartaric acid reacting with calcium as it wasTartaric acid reacting with calcium as it was

released which extends working time toreleased which extends working time to

reasonable valuesreasonable values Enhances rate of formation of aluminumEnhances rate of formation of aluminum

polyacrylate crosslinks which speeds uppolyacrylate crosslinks which speeds up

setting.setting.



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Adhesion: Adhesion: Chemical bond to enamel &dentine by ionChemical bond to enamel &dentine by ion

exchange (displacing calcium and phosphate ions and creatingexchange (displacing calcium and phosphate ions and creating

an intermediate layer of polyacrylate, phosphate and calcium.an intermediate layer of polyacrylate, phosphate and calcium.

Or binding with CaOr binding with Ca+2+2 in tooth.in tooth.



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Continue,Continue,

Adhesion: bond to dentine maybe by hydrogen Adhesion: bond to dentine maybe by hydrogen

bond to collagen and ionic bond to apatitebond to collagen and ionic bond to apatitecrystals in dentine. The major type of failure iscrystals in dentine. The major type of failure is

cohesive within GIC rather than adhesive withcohesive within GIC rather than adhesive with

tooth surface. so, GIC has a low tensile strengthtooth surface. so, GIC has a low tensile strength(brittle)(brittle)

To obtain a good bond: tooth surface should beTo obtain a good bond: tooth surface should be

cleaned, treated with conditioner to removecleaned, treated with conditioner to removedebris and improve wettabilitydebris and improve wettability



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Aesthetics: glass governs the color of the Aesthetics: glass governs the color of the

material. Pigments maybe added such asmaterial. Pigments maybe added such ascarbon black, ferric oxide.carbon black, ferric oxide.

The major issue is translucency ratherThe major issue is translucency ratherthan color. GIC translucency is morethan color. GIC translucency is more

comparable to dentine.comparable to dentine.

Aesthetically, GIC is inferior to composite, Aesthetically, GIC is inferior to composite,

appear opaque, dull, lifelessappear opaque, dull, lifeless



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Solubility:Solubility: Sensitive to moistureSensitive to moisture&dehydration during setting and maturation&dehydration during setting and maturation

(1(1stst

24 hours). Use varnish (MMA resin,24 hours). Use varnish (MMA resin,nitrocellulose) finishing after 24 hoursnitrocellulose) finishing after 24 hours

Loss of material from GIC maybe due to:Loss of material from GIC maybe due to: Dissolution of immature cementDissolution of immature cement Abrasion (GIC have low abrasion resistance) Abrasion (GIC have low abrasion resistance)

ErosionErosion

Loss of material decreases after it fully setsLoss of material decreases after it fully setswhich usually takes a few dayswhich usually takes a few days



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Fluoride release:Fluoride release: highhigh initial fluoride release,initial fluoride release,then lower continuous release for long time. Fthen lower continuous release for long time. F--

antibacterial, remineralizationantibacterial, remineralization

Biocompatibility:Biocompatibility: Tolerated by surroundingTolerated by surroundingtissue & kind to pulp. However, theytissue & kind to pulp. However, they’ ’ ve beenve beenassociated with postoperative sensitivity, acid pHassociated with postoperative sensitivity, acid pH

initially then neutralinitially then neutral Strength:Strength: Moderate compressive strength, low tensileModerate compressive strength, low tensile

strength. not suitable for stress bearing areasstrength. not suitable for stress bearing areas

Thermal expansionThermal expansion: similar to that of tooth: similar to that of toothstructurestructure

Effect of P:L on strength and solubility?Effect of P:L on strength and solubility?



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Clinical application of GICClinical application of GIC

General notes:General notes:

Tooth surface should be clean and dry but notTooth surface should be clean and dry but notdesiccateddesiccated

Polyacrylic acid should be used if advised byPolyacrylic acid should be used if advised by

manufacturermanufacturer

GIC should be protected with a varnish (resinGIC should be protected with a varnish (resin

dissolved in a volatile solvent) to avoiddissolved in a volatile solvent) to avoidmoisture contamination and dehydrationmoisture contamination and dehydration



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CLINICAL USECLINICAL USE

Luting cements:Luting cements:

Advantages: Advantages: Fluoride releaseFluoride release

Low film thicknessLow film thickness

Kind to pulpKind to pulp

Bond to tooth structureBond to tooth structure

Their use decreasedTheir use decreased

after hybrid ionomersafter hybrid ionomersand resin cementsand resin cements

were introduced sincewere introduced since

they are strongerthey are stronger



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Restorative materials: used in nonRestorative materials: used in non--stress bearingstress bearing

areas:areas: Root cariesRoot caries

Occlusal lesions in primary teethOcclusal lesions in primary teeth

Temporary restorationsTemporary restorations Cervical cavities (abrasion and erosion lesions)Cervical cavities (abrasion and erosion lesions)

Anterior class III when color matching is not an issue Anterior class III when color matching is not an issue



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CLINIAL USECLINIAL USE

Liners and bases: used to protect the pulp from:Liners and bases: used to protect the pulp from:

Temperature changesTemperature changes Chemicals from other restorative materialsChemicals from other restorative materials

Acid etchants Acid etchants

Liners have lower powder: liquid ratio and weak.Liners have lower powder: liquid ratio and weak.

GIC bases are used to rebuild missing toothGIC bases are used to rebuild missing tooth

structure, stronger than liners and have a higherstructure, stronger than liners and have a higherpowder: liquid ratiopowder: liquid ratio



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Ref. Phillip’s science of dental materials



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Clinical applicationClinical application

Preparation of dentinal surfacePreparation of dentinal surface

Depends on the nature of the tooth surfaceDepends on the nature of the tooth surfaceon which GIC will be placed.on which GIC will be placed.

Most importantly, clean surface, use of aMost importantly, clean surface, use of a

conditionerconditioner

Incase of prepared cavities: no need forIncase of prepared cavities: no need for

cleaning with pumice and water but acleaning with pumice and water but aconditioner is needed to remove smear layer.conditioner is needed to remove smear layer.

Patients with sensitive teeth?Patients with sensitive teeth?



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Pulpal protection: maybe necessary inPulpal protection: maybe necessary in

very deep cavities, to prevent directvery deep cavities, to prevent directcontact between GIC with pulp tissue.contact between GIC with pulp tissue.

The liner of choice is calcium hydroxide,The liner of choice is calcium hydroxide,but keep in mind that the maximum areabut keep in mind that the maximum area

of dentine is needed to ensure good bondof dentine is needed to ensure good bond

with GIC.with GIC.



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Dispensing, mixing, insertion:Dispensing, mixing, insertion:

For powder liquid system: ensure accurateFor powder liquid system: ensure accurateratio, and tap powder bottle to loosen up theratio, and tap powder bottle to loosen up the

particles. Gradual incorporation of powderparticles. Gradual incorporation of powder

into liquid, and follow manufacturerinto liquid, and follow manufacturerinstructions in terms of mixing time.instructions in terms of mixing time.

Encapsulated: capsule should be shaken first,Encapsulated: capsule should be shaken first,

then mixed in an amalgamator running atthen mixed in an amalgamator running at

4000 rpm for 10 seconds4000 rpm for 10 seconds



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Finishing and polishing:Finishing and polishing: a matrix maybe useda matrix maybe usedto protect the surface until the material sets,to protect the surface until the material sets,then any excess GIC should be removed after 24then any excess GIC should be removed after 24hours by finishing and polishing. Removal of hours by finishing and polishing. Removal of gross excess maybe done using a sharp bladegross excess maybe done using a sharp bladerather than a carver.rather than a carver.

As a general rule: finishing should be delayed As a general rule: finishing should be delayed

After 24 hours: using fine diamond bur or 12 After 24 hours: using fine diamond bur or 12blade carbide bur with water. Polishing is doneblade carbide bur with water. Polishing is doneusing abrasive discs again with water.using abrasive discs again with water.



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Surface protection: varnishes used:Surface protection: varnishes used:

Solution of natural copal resinSolution of natural copal resin Synthetic resin (cellulose acetate)Synthetic resin (cellulose acetate)

These two maybe dissolved in an organicThese two maybe dissolved in an organicsolvent such as ether, acetone, chloroformsolvent such as ether, acetone, chloroform

Other varnishes: nail varnish, bondingOther varnishes: nail varnish, bonding

agents.agents.



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Lamination orLamination orsandwich technique:sandwich technique:GIC is used as a baseGIC is used as a baseunderneath compositeunderneath compositerestorations, in deeprestorations, in deep

proximal cavitiesproximal cavitieswhere the gingivalwhere the gingivalfloor is on the root.floor is on the root.

GIC in this caseGIC in this caseprovides better sealprovides better sealand releases fluoride.and releases fluoride.

Ref. Dental materials, clinical applications.

Sil tSil t



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Silver cermetsSilver cermets

Have metal particles added to them, e.g.Have metal particles added to them, e.g.silver (particle size 3silver (particle size 3--44 µµm)m) , to improve, to improve

toughness strength and abrasiontoughness strength and abrasionresistance.resistance.

Also contain T Also contain Titanium oxide.itanium oxide.

Liquid is copolymer of acrylic, maleic andLiquid is copolymer of acrylic, maleic and9% tartaric acid9% tartaric acid

Presentation:Presentation: Powder liquid system, or capsulesPowder liquid system, or capsules

Clinical use: small occlusal cavitiesClinical use: small occlusal cavities



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Core build up materials: cermet GICs areCore build up materials: cermet GICs are

usually used for this purpose. They areusually used for this purpose. They areused:used:

In locations were esthetics are not importantIn locations were esthetics are not important

To replace missing tooth structure where theTo replace missing tooth structure where the

permanent restoration is crown.permanent restoration is crown.



35Ref. Phillip’s science of dental materials

CLINICAL USECLINICAL USE (R f D l(R f D l



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CLINICAL USECLINICAL USE (Reference, Dental(Reference, Dental

materials, clinical applications for dental assistantsmaterials, clinical applications for dental assistantsand dental hygienists, chapter 7)and dental hygienists, chapter 7)

Pit and fissurePit and fissuresealants: materialssealants: materials

used to sealused to seal

noncarious pits andnoncarious pits andfissures of deciduousfissures of deciduous

and permanent teeth.and permanent teeth.

Indications for the use ofIndications for the use of



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Indications for the use ofIndications for the use of

sealantssealants Teeth with deep pits and fissures.Teeth with deep pits and fissures.

Sealants are targeted to young children soSealants are targeted to young children so

that susceptible pits and fissures arethat susceptible pits and fissures areprotected.protected.

High caries risk patients (poor oralHigh caries risk patients (poor oral

hygiene, high sugar intake, etchygiene, high sugar intake, etc……))



C i



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Continue,Continue,

The use of GICs as sealants haveThe use of GICs as sealants have

been suggested due to:been suggested due to:

Fluoride release.Fluoride release.

Adhesion to moist tooth Adhesion to moist tooth

structurestructure

Disadvantages:Disadvantages:

Inability to fully penetrateInability to fully penetrate

fissuresfissures

BrittlenessBrittleness

Low wear resistanceLow wear resistance

CCli i l li i



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The tooth should be isolated andThe tooth should be isolated and

20%polyacrylic acid is applied for 1020%polyacrylic acid is applied for 10--1515seconds (or according to manufacturerseconds (or according to manufacturerinstructions.instructions.

GIC is mixed and applied to pits andGIC is mixed and applied to pits andfissures.fissures.

GIC varnish is applied to protect theGIC varnish is applied to protect thesealant from moisture contamination andsealant from moisture contamination anddehydration.dehydration.

Occlusion is checked and adjusted.Occlusion is checked and adjusted.



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Hybrid (resinHybrid (resin modified) GICmodified) GIC



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Hybrid (resinHybrid (resin--modified) GICmodified) GIC

Hydroxyethyl methacrylate (HEMA) resin, isHydroxyethyl methacrylate (HEMA) resin, isadded to GIC to improve physical properties.added to GIC to improve physical properties.

Advantages compared to conventional GIC: Advantages compared to conventional GIC: Improved wear resistanceImproved wear resistance

StrongerStronger

More polishableMore polishable

Resin protects the matrix from moisture,Resin protects the matrix from moisture,

which decreases solubilitywhich decreases solubility Setting reaction?Setting reaction?

R iR i difi d GICdifi d GIC



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ResinResin--modified GICmodified GIC

Composition: the liquid component:Composition: the liquid component:

Hydrophilic monomer is added to the liquidHydrophilic monomer is added to the liquidpolyacrylic acid (HEMA) orpolyacrylic acid (HEMA) or

Polyacrylic acid with pendent methacryloxyPolyacrylic acid with pendent methacryloxy

groups,groups,

In addition to tartaric acid andIn addition to tartaric acid and

photoinitiatorphotoinitiator

S tti tiS tti ti



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Setting reactionSetting reaction

Prolonged and slow acidProlonged and slow acid--base reaction.base reaction.

This will prolong working time. Rapid setThis will prolong working time. Rapid setis provided by light curing. If the materialis provided by light curing. If the material

is not exposed to light it will eventually setis not exposed to light it will eventually set

by acid base reaction in 15 minutes.by acid base reaction in 15 minutes.

Incremental placement maybe necessary,Incremental placement maybe necessary,

issues of polymerization shrinkage maybeissues of polymerization shrinkage maybeencountered.encountered.

P tiProperties



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Long working time and short setting timeLong working time and short setting time

Finishing and polishing maybe doneFinishing and polishing maybe doneimmediatelyimmediately

More resistance to acid attack andMore resistance to acid attack anddehydrationdehydration

Cli i l li tiClinical applications



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Clinical applicationsClinical applications

Direct restorative materials, proved to beDirect restorative materials, proved to be

better than conventional GICs in primarybetter than conventional GICs in primarydentitiondentition

Liners and bases underneath composites,Liners and bases underneath composites,

amalgamsamalgams

Luting agentsLuting agents



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Ref. Phillip’s science of dental materials



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lecture 5 & 6 - glass ionomer cements (slides)

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