cements in orthodontia

8/3/2019 Cements in Orthodontia

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Presented by

Dr.K.R.SAKTHIPRIYA


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DEFINITION;Cements are substance that hardens to act as a

base,liner,filling material or adhesive to bonddevices or prosthesis to tooth structure or to each

other.

CraigSkinner

E.C combe

ADA specification

2

Classification;


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CRAIG;Classification is based on use of cements

Final cementation

Temporary cementation

High strength bases

Temporary fillings

Low strength bases

Liners

Varnishes


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SKINNERZinc phosphate

Zinc phosphate with silver or copper salts

Copper phosphateZinc oxide eugenol

Zinc polycarboxylate

Silicate

Silico phosphateGic

Resin cements

Calcium hydroxide


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E.C.COMBEAcid base reaction cements

Polymerisation cements1. Cyano acrylates

2. Dimetha acrylate polymers

3. Polymer ceramic composites


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ADA SPECIFICATION:TYPE I- fine grain for cementation

TYPE II- medium grain for bases,orthodontic purpose

Zinc phosphate

Zinc polycarboxylate

GIC

Resin cements

Composite resin

CEMENTS USEDINORTHODONTIA


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ZINC PHOSPHATE: THER NAMES:

Crown and bridge

Zinc oxyphosphate

CLASSIFICATION:

TYPE I:fine grained for luting-25mTYPE II:medium grained for luting and filling-40m


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COMPOSITION

POWDER:

Zinc oxide-90.2% -principal ingredient

Magnesium oxide-10%-reduces temperature of calcination process

Silicon dioxide-1.4%-active filler Bismuth dioxide-0.1%-impart smoothness of freshly mixed cement

Tanin flouride-source of flouride

Ingredients heated for a temperature of 1000-1300c for

4-8 hrs

Calcination-fused sintered mass ground andpulverised fine powder


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LIQUID:Ortho phosphoric acid free-38.2%

Ortho phosphoric acid with Aland zinc-16.2%Aluminium-2.5%

Zinc-7%

Partial neutralisation of phosphoric acid byaluminium and zinctempers the reactivity ofliquid and is called buffering

Buffering reduces rate of reaction and helps to establish a smooth,non granular, workable cement mass with proper setting time andmechanical properties.


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MANIPULATIONManner in which reaction occurs determines the working

characteristics and properties of cements

MIXING SLAB:

A properly cooled,thick glass slab dissipates heat of the

reactionTemperature should be low enough to effectively cool the

cement mass but must not be below dew point

Frozen slab technique temperature of 18-24c indicated

when room humidity permitsMoisture contamination below dew point contaminates

mix diluting the liquid and shortens setting time


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Increased P/L ratio provides more desirable properties

incorporate as much powder as possible to obtain a particularconsistency.

zinc phosphate cement liquid,Absorbs water at humid atmosphere

Looses water-at dryatmosphere

Increased water-decreases setting time

Decreased water-increases setting time

Keep liquid bottle tightly closed when not dispensing

Polyethylene squeeze bottles do not require removal ofadropper and eliminates tendency for gain or loss of waterfrom liquid

P/LRATIO:

CAREOFLIQUID:


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MIXING:

Incorporate small portion of powder to liquid sominimum heat is liberated and easily dissipated

Heat is dissipated when cement is mixed over alargearea

Long ,narrow, bladed stainless steel to spread cementacross large area

Temperature 1/mixing time

Largevolume of powder is carried to liquid allat once

rather than spatulated over alarge area,temperaturebecomes higher speeds the reactions and hinderscontrol over consistency

INITIALLY,


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Middle of mixing period large amount of powderincorporated to saturate the liquid with newly forming zincphosphates

Unreacted acid is lost prior neutralisation gained fromsmall increments

Finally, smaller increments are incorporated so ultimateconsistency of cement is not exceeded

MIXINGTIME-60-90SECONDS

LONGMIXINGTIME-WEAKENED CEMENTMATRIX


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FROZENSLABMETHOD:

Used in cementation of orthodontic bracketsAllows cementation of many bands

Glass slab cooled to 6 or -10c

No attempt made to prevent moisture from

condensing on the slabMixing made untill correct consistency is reached

Amount ofpowder incorporated is 50-70% morethan normal procedures.

Increases working time-4-11 min

Shortens setting time-20-40%less

ADVANTAGES:


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CHARACTERISTIC PROPERTIES:Ansi ADA specification no.96 (iso 9917) for dental water

based cements,

Film thickness maximum-25m

Settting time-2.5-8 minCompressive strength-70mpa

Acid erosion(mm/hr)-0.1

Compressive strength-96-133mpa

Tensile strength-3.1-4.5

Elastic modulus-9.3-13.4

P/L ratio-1.4gm/0.5ml


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CONSISTENCY ANDFILMTHICKNESSTwo arbitrary consistencies termed as inlay seating

/luting and cement base/ filling

Third consistencies which lies midway between lutingand filling is used for retention of orthodontic bands

and termed asBAND SEATING CONSISTENCY}

Consistency quantified by measuringviscosity

Increases in higher temperatures

Delay in cementation-increases film thickness andinsufficient seating of restoration

Viscosity:


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SETTING

TIME

Sufficient setting time needed to seat and adapt themargins and adjust a series of ortho bands

Slightly shotter than inlay seating because of greaterquantity of powder used to establish heavierconsistency


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FAC

TORS

GOVER

NINGS

ETTINGCONTROLLED CONTROLLEDBYMANUFACTURER BYOPERATORPowder composition p/l ratioDegree of calcination rate of powder

incorporationParticle size mixing temperatureBuffering ofliquid manner of spatulationWater content ofliquid water contamination or loss

ofliquid


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SOLUBILITY ANDDISINTEGRATIONPremature contact of incompletely set cement with

water -dissolution and leaching

Prolonged contact even of well hardened cementdemonstates erosion

ANSI/ADA SPECIFICATIONNO.96,ALLOWSMAXIMUM RATEOFEROSIONOF0.1MM/HRWHENCEMENTISSUBJECTEDTOLACTIC ACIDEROSIONBYIMPINGINGJETTECHNIQUE

Greater resistance to solution and disintegration-increasing powder liquid ratio


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DIMENSIONALSTABILITY:

shrinks on hardening -0.04%-0.06% in 7 days

ACIDITY:

4.2-8 min6-1hr end7-48hrs

APPLICATIONINORTHO;1.Cementation of ortho bands2.orthodontic consistencylies between luting and base consistency

3.most important requirement is working time and longer workingtime is achieved by frozen slab method


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ZINC POLYCARBOXYLATEThis was the first cement system developedwith a potential for adhesion to toothstructure

Introduced by smith

Combines the properties of both zinc oxideeugenol and zinc phosphate


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COMPOSITION:POWDER:Zinc oxide-basic ingredient

Mg oxide-principle modifier

Bi and aluminium oxides-smallamounts

Stannous flouride increases strength,modifies setting

time,imparts anti cariogenic properties

LIQUID:Polyacrylic acid

Copolymer ofacrylic acid with other unsaturated acidslike itaconic,maleic,tricarballylic acid.

Acid concentration -40% by weight

Molecular weight-22000-50000


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WATERSETTABLECEMENTS:

Polyacid is freeze dried and that powder ismixed with cement powder

Water is used as aliquidWhen powder is mixed with water

polyacrylic acid goes in to solution and thereaction proceeds


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SETTING REACTION;Set cement is zinc polycarboxylate ionic gel which

unites unreacted zinc oxide particles

Gel bound to polyanion chains by electrostaticinteractions rather than by stronger specific ionbinding

Setting reaction retarded by cool

environment,accelerated bya warm environment


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MANIPULATION:P/L ratio of 1:1 to 2:1Consistency of the mix is creamy

Mixed cement is pseudo plastic that isviscosityincreases as shear rate increases

Dispense liquid before mixing to prevent evaporation

Mixing time 30-60 sec

Working time extended to 10-15 min by mixing on a

glass slab chilled to 4 degree c


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ADA SPECIFICATION REQUREMENTSFilm thickness-25m

Net setting time-2.5-8min

Compressive strength-70Acid erosion max 2.0mm/hr


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STRENGTH:2

4 hour compressiv

e strength of poly

acry

late for

luting islower than that of zn phosphate cements

98-133mpa

BONDSTRENGTH:

Interesting feature of polyacrylate cement is its bonding toenameland dentin - ability of carboxylate group in thepolymer molecule to chelate with calcium.

Bond strength to enamel is 3.4-13 mpa and to dentin is

2.1mpaOptimum bonding requires clean surface

Sand blasting or electrolytic etching optimum bonding


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STRENGTH;

24 hour Compressive strength for luting is lower thanzinc phosphate cements 98-133mpa however tensile

strength of polyacrylate cement is about 40% higherthan zn phosphates

Modulus of elasticity is 1/3 of zn phosphates


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DIMENSIONALSTABILITYZN polyacrylate shows alinear contraction when

setting at 37 degree c

Amount of contractionvaries from 1% for wetspecimen at 1 day to 6%for dry specimen at 14 days

ACIDITY:More acidicwhen mixed but acid is weakely

dissociated and penetration of high molecularweight towards pulpal tissue is minimal


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APPLICATIONS

Used primarily for luting permanent alloy restorationsand as bases

Also used in orthodontia for cementation of bands


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GLASSIONOMER CEMENTGIC is a tooth coloured restorative material.Development of the glass-ionomer cements (GICs)

was first announced byWILSON AND KENTin 19721972

First marketed in Europe in 1975 and was available inthe United States in 1977

Glass ionomers are hybrids of the SILICATE cementsand the POLYCARBOXYLATEcement.


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Combines characteristics of bothsilicate cements -translucencyand fluoride release

polycarboxylate cements-ability to chemically bondto tooth structure and kindness to the pulp.

Need to overcome disadvantages ofSilicate-pulp irritant nature

disintegration in oral cavity

opaque on drying

Polycarboxylate-opaque to presence of unreactedzinc


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COMPOSITION:

POWDER:The typical glass in a glass ionomer is made byfusing quartz, alumina, cryolite, fluorite, aluminumtri fluoride, and aluminum phosphate

CalciumCalcium flourideflouride(CaF(CaF22))--1515..77--2020..11%%

Silicon dioxide (SiO2)-35.235.2--41.9%41.9%

Aluminum oxide (Al2O3)-20.120.1--28.6%28.6%

Aluminum phosphate (AlPO4)-3.83.8--12.1%12.1%

Aluminum fluoride (AlF3)-1.61.6--8.9%8.9%

Sodium fluoride (NaF)-4.14.1--9.3%9.3%


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LIQUID:

copolymers of polyacrylic acid.

Earlyliquids were made solely ofa50%aqueous

solution of polyacrylic acid.These solutions were unsatisfactory because they

gelled in 10 to 30 minutes.

Scientists thought the liquid formed hydrogenbonds between the polyacid chains

It was later discovered that using copolymerscontaining acrylic and itaconic acid improvesboth stabilityand shelflife


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TYPESOFGIC:There are three types of GICThere are three types of GIC

1.1. HydrousHydrous: In this type of GICall the: In this type of GICall the polyacrylicpolyacrylic acid is in liquidacid is in liquidcomponent, this is how GIC were first introduced. These cements arecomponent, this is how GIC were first introduced. These cements are

-- HighlyviscousHighlyviscous-- Less initialacidityLess initialacidity

-- Rarelyassociated with tooth sensitivityRarelyassociated with tooth sensitivity

ADVANTAGES:ADVANTAGES:

-- LessLess pulpalpulpal sensitivitysensitivity-- Faster initial set and lower solubilityFaster initial set and lower solubility

DISADVANTAGES:DISADVANTAGES:

--ThickerThicker-- more difficult to seat castingmore difficult to seat casting--Long term solubility is greaterLong term solubility is greater--Powder /liquid ratio is lowerPowder /liquid ratio is lower-- poorer physical propertiespoorer physical properties--Shorter shelflifeShorter shelflife


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ANHYDROUS:

TheThe polyacrylicpolyacrylic acid is freeze dried ,added to the glass powder and thenacid is freeze dried ,added to the glass powder and thenmixed with water or tartaric acid to reconstitute themixed with water or tartaric acid to reconstitute the polyacrylicpolyacrylic acidacid--longer shelflifelonger shelflife

The resulting mix is thinner and can be mixed to higher P/L ratio, henceThe resulting mix is thinner and can be mixed to higher P/L ratio, henceimproving physical propertiesimproving physical properties

Cement has higher initialacidity ,hence higher incidence of postCement has higher initialacidity ,hence higher incidence of post--operative sensitivityandoperative sensitivityand pulpalpulpal deathdeath

Some anhydrousSome anhydrous ionomersionomers use 30%tartaric aciduse 30%tartaric acidSome use 5Some use 5-- 10% tartaric acid10% tartaric acid

Advantages:Advantages:

-- Lessviscous, makes crown seating easierLessviscous, makes crown seating easier-- Least long term solubilityLeast long term solubility-- Improved shelflifeImproved shelflife

Disadvantages:Disadvantages:-- LessLess pulpalpulpal kindnesskindness-- Slower initial setSlower initial set


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SEMIHYDROUS:

Semihydrous glass ionomers contain polyacrylic acid in both theirliquid and their powder. They usually have an intermediate amount oftartaric acid in their liquid.

ADVANTAGES:

- Intermediate initial acidityand postoperative sensitivity;

- Intermediateviscosity.

DISADVANTAGES:

- higher initialacidity than hydrous systems

-more postoperative sensitivity

-slightly thicker than anhydrous cements.


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CLASSIFICATION:ACCORDING TOWILSON AND MCLEAN,

TYPEI luting cements

TYPEII-restorative cements

-restorativeaesthetic

-restorative reinforced

ACCORDING TOMCLEAN,

1.GIC(TRADITIONAL)

2.RESIN MODIFIED GIC3.POLYACID MODIFIED


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ACCORDING TOAPPLICATION:G.I.C canbeclassifiedintoninetypesG.I.C canbeclassifiedintoninetypes

Type 1Type 1--LutingLutingagent;autocuredagent;autocured

Type 2Type 2--restorativerestorativematerial;autocuredmaterial;autocured andavailablein differentandavailablein differentshadesandlargerfilmthicknessshadesandlargerfilmthickness

Type 3Type 3--linersandlinersandbases;autocuredbases;autocured

Type 4Type 4--metalmodified;metalmodified;autocuredautocured

Type 5Type 5--lightcuredlightcured

Type 6Type 6--corebuildcorebuildup;autoup;auto curedcured

Type 7Type 7--pitandfissurepitandfissuresealent;autosealent;auto curedcured

TypeType88--cementationoforthodonticbandsandbracketscementationoforthodonticbandsandbrackets

Type 9Type 9--forforatraumaticatraumatic restorativetreatmentrestorativetreatment


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LIGHTCURED GIC:

RESTORATIVE GIC:


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METAL MODIFIED GIC

GICCORE BUILTUP


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MANIPULATION:To achieve long lasting results the following conditions for

GIC have to be satisfied.

Surface of prepared tooth must be clean and dry.

Consistency of mixed cement must allow complete coatingof the surface.

excess cement must be removed at right time.

Surface must be finished without excessive drying.

Protection of restoration surface must be ensured toprevent cracking and dissolution

PREP R T N F THE M TER L


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PREPARATION OF THE MATERIAL


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PREPARATIONOFTOOTHSURFACEClean surface is important for proper adhesion.Clean surface is important for proper adhesion.

Etching with phosphoric acid 34%Etching with phosphoric acid 34%--37%.37%.

OrOr polyacrylicpolyacrylic acid 10%acid 10%--20% for 1020% for 10--20 sec,20 sec,followed by 10followed by 10--20 sec of water rinsing time20 sec of water rinsing time

After preparation the surface must be dried butAfter preparation the surface must be dried butnot unduly desiccatednot unduly desiccated


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PRECONDITIONING SURFACE

POSTCONDITIONING SURFACE


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The powder liquid ratio recommended by theThe powder liquid ratio recommended by themanufacturer followed.manufacturer followed.The mix should be thick shinyand provide adequateThe mix should be thick shinyand provide adequateworking time.working time.Due to difficulty in getting consistent mix, GIC is alsoDue to difficulty in getting consistent mix, GIC is also

available in capsule form.available in capsule form.A paper pad is usedA paper pad is usedPowder and liquid are dispensed on the paper pad justPowder and liquid are dispensed on the paper pad justbefore mixingbefore mixingProlonged exposure to moisture can alter theProlonged exposure to moisture can alter thewater/acid ratio of the liquidwater/acid ratio of the liquid

The powder should be incorporated in the liquidThe powder should be incorporated in the liquidrapidly using a stiff spatula for restorative applicationsrapidly using a stiff spatula for restorative applicationsand plastic spatula forand plastic spatula for lutinglutingMixing is done byMixing is done byFOLDINGMETHODFOLDINGMETHODMixing time should beMixing time should be 4545--60SEC60SECMix should have aMix should have aGLOSSYGLOSSYappearance after mixingappearance after mixing

PREPARATIONOFMATERIAL


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GIC is also supplied in capsules, containing preGIC is also supplied in capsules, containing pre--portioned powder and liquid .portioned powder and liquid .

Mixing is accomplished in amalgamator.Mixing is accomplished in amalgamator.

Capsule has a nozzle so that the mix can beCapsule has a nozzle so that the mix can bedirectlyapplied to the prepared toothdirectlyapplied to the prepared tooth

The advantages are convenience, consistentThe advantages are convenience, consistentcontrol of P/L ratio and elimination ofvariationscontrol of P/L ratio and elimination ofvariationsassociated with hand mixing.associated with hand mixing.

PREPROPORTIONED CAPSULES


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SETTING REACTION:

GlassGlass ionomerionomer undergoes three distinct and overlappingundergoes three distinct and overlappingsetting reactionssetting reactions

Immediate leaching phaseImmediate leaching phaseHydrogelHydrogel set phaseset phasePolysaltPolysalt gelgel phase,finalphase,final set phaseset phase

SETTING TIMESETTING TIMETYPEITYPEI-- 44-- 5MINUTES5MINUTES

TYPEIITYPEII-- 7MINUTES7MINUTES


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IONLEACHABLEPHASEThe aqueous solution ofThe aqueous solution of polyacidpolyacid coco--polymerspolymers

and tartaric acid accelerators attack the ionand tartaric acid accelerators attack the ionleachableleachable AluminoAlumino --silicate powder and dissolvesilicate powder and dissolvethe outer glass surfacethe outer glass surface

Hydrogen ions from the tartaric andHydrogen ions from the tartaric and polyacrylicpolyacrylicacid releaseacid release ca+andca+and al+ ions from the glassal+ ions from the glasssurfacesurface

These react with fluoride ions to formThese react with fluoride ions to form cafcafandand alfalf

As the acidity increasesAs the acidity increases cafcaf reacts with acrylicreacts with acryliccoco--polymer to form more stable complexpolymer to form more stable complex

Heat of 30Heat of 30--70c is liberated70c is liberated


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APPEARANCEGIC reacts with tooth surfaceGIC reacts with tooth surfaceAppears shiny or glossy due toAppears shiny or glossy due to unreactedunreacted matrixmatrix

placement should be done in this phase because maximumplacement should be done in this phase because maximumamount of free polyacid matrix is available for reactionamount of free polyacid matrix is available for reaction

At the end of this phase matrix reacts with glass and is less able toAt the end of this phase matrix reacts with glass and is less able toreact to tooth structurereact to tooth structure


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HYDROGELPHASE

This phase begins 5-10 min after cement mixing,causes initial setCa ions are more rapidly released and react with

negatively charged poly-ionic poly-acid chains to formionic cross links

Reduced mobility ofaqueous polymer chains, causing

initial gelation of ionomer matrixIonomer should be protected from moisture and

dissection in this phase

APPEARANCE

G.I.C in this phase appears rigid and opaqueOpacity is due to large difference between refractory

index of filler and matrixThis phase is transient and disappears in the final set

phase


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POLYSALTGELPHASEOccurs when material reaches final set, continues

for several months.

Matrix matures when al ions which are releasedmore slowly, form poly salt hydrogel to surroundun-reacted glass filler

Glass looks more tooth like because index of

refraction of silica gel is more similar to matrix,hence reducing light scattering and opacity.


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SETTING RECTION


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MECHANICALPROPERTIESMECHANICALPROPERTIES

Compressive strengthCompressive strength--150Mpa150MpaTensile strengthTensile strength --6.66.6 MpaMpaHardnessHardness --4949 khnkhn

ADVANTAGESADVANTAGESForms rigid substance on settingForms rigid substance on setting

Good fluoride release (Good fluoride release (bacteriostaticbacteriostatic inhibit caries)inhibit caries)ReRe--chargeable fluoride componentchargeable fluoride componentLow exothermic reaction on settingLow exothermic reaction on settingLess shrinkage than polymerizing resinsLess shrinkage than polymerizing resinsResistant to microResistant to micro--leakageleakageNon irritant to pulpNon irritant to pulpGood marginal integrityGood marginal integrityAdheres chemically to enameland dentinAdheres chemically to enameland dentinCoefficient of thermal expansion similar to dentinCoefficient of thermal expansion similar to dentin


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Sensitivity to moisture at placementSusceptibility to dehydration over life time.Poor abrasion resistant

Average estheticsLess tensile strength than compositesTechnique sensitive P/L ratio &mixingLess color stability than resinsContra-indicated for class 4 &other stressbearing restorations

DISADVANTAGES


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MODIFICATIONSOFGICGlass metal ionomer mixturesCeramic metal ionomer mixturesResin modified ionomersCompomer

METALREINFORCEDG.I.CG.I.Clack strength, hence cannot withstand high stressconcentration, hence can be reinforced by

1.Physically incorporating glass powder with silver allow

powder, silver alloyadmix-MIRACLE MIX2.Fusing glass powder with silver particles through sintering-CERMET


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METALMODIFIED:

TYPES:SILVER ALLOY ADMIX/MIRACLEMIX:

physically incorporating silver alloy powder with

glass powder.CERMET:

fusing of glass powder to silver particle throughsintering.


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METALMODIFIED-PROPERTIES

Both systems released fluoride initially ,but magnitudeBoth systems released fluoride initially ,but magnitudedecreased substantially with time, as a portion of glassdecreased substantially with time, as a portion of glassparticle is metal coatedparticle is metal coated

Presence of metal fillers made the material grey , radioPresence of metal fillers made the material grey , radio--opaqueopaqueThey set rapidlyand can be finished in a short timeThey set rapidlyand can be finished in a short time


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Acid base reactionAcid base reactionPolymerizablePolymerizable functional groups can be added to impart morefunctional groups can be added to impart morerapid curing when activated bylight or chemicalsrapid curing when activated bylight or chemicals

These products are considered to be dualThese products are considered to be dual--cure if only onecure if only one

polymerization mechanism is usedpolymerization mechanism is usedIf both are used then triIf both are used then tri--curedcuredTheyare classified as resin modified or hybridTheyare classified as resin modified or hybrid ionomersionomers

PowderPowder--ionion--leachableleachable flouroaluminosilicateflouroaluminosilicate glassglass

initiators for light/chemical curinginitiators for light/chemical curingLiquidLiquid--

waterwaterpolyacrylicpolyacrylic acid modified withacid modified with methacrylatemethacrylate andand hydroxyethylhydroxyethyl

methacrylatemethacrylate

RESINMODIFIEDGIC


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PROPERTIES

Improved translucency due to inclusion ofImproved translucency due to inclusion ofmonomersmonomersFluoride release same as that of conventional GICFluoride release same as that of conventional GICHigher tensileHigher tensile strenghstrengh

Bond strength to tooth structure can be higherBond strength to tooth structure can be higherthan conventional GICthan conventional GICBiocompatibility is comparable to conventionalBiocompatibility is comparable to conventionalGICGIC

DISADVANTAGESDISADVANTAGESPolymerization results in greater degree ofPolymerization results in greater degree ofshrinkage upon settingshrinkage upon settingIncreasedIncreased microleakagemicroleakage


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PROPERTIESCompressivestrength (MPa)

Tensilestrength

(MPa)

Knoop

hardness

(KHN)

ConventionalGIC 150 6.6 48

cermet 150 6.7 39

Hybrid GIC 105 20 40


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COMPOMERSpolyacidpolyacid modified composites, COMPOMERmodified composites, COMPOMER

Combines propertiesCombines properties gicgic and resin base compositesand resin base composites

one paste light curable material for restorative applicationsone paste light curable material for restorative applications

Consists of silicate glass particles, sodium fluoride andConsists of silicate glass particles, sodium fluoride and polyacidpolyacidmodified monomer without any watermodified monomer without any water

Setting is initiated by photoSetting is initiated by photo--polymerization of the acidic monomerpolymerization of the acidic monomer

The set material starts to absorb water in saliva that contributesThe set material starts to absorb water in saliva that contributesacid base reaction between acidic functional groups within matrix anacid base reaction between acidic functional groups within matrix anglass particlesglass particles--releasesreleases flourideflouride

Because ofabsence of water in the formulation the cement is notBecause ofabsence of water in the formulation the cement is notselfadhesive ,thus separate dentin bonding agent is neededselfadhesive ,thus separate dentin bonding agent is needed


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MECHANISMOFADHESION

The mechanism by which GIC bonds to tooth surface hasThe mechanism by which GIC bonds to tooth surface hasnot been clearly identifiednot been clearly identified

primarily involvesprimarily involves chelationchelation of carboxyl groups of theof carboxyl groups of the

polypoly--acids with the calcium in the apatite of the enamelandacids with the calcium in the apatite of the enamelanddentin.dentin.

The bond strength of enamel to dentin is higher because ofThe bond strength of enamel to dentin is higher because ofgreater inorganic content of enamelgreater inorganic content of enamel


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Study was done to evaluate the effects of two concentrationsStudy was done to evaluate the effects of two concentrationsofof polyacidspolyacids(10&25%),on three treatments (untreated, passive(10&25%),on three treatments (untreated, passiveconditioning and active conditioning).conditioning and active conditioning).passive conditioning the dentin surface was treated withpassive conditioning the dentin surface was treated withpolyacrylicpolyacrylic acid for 30 secacid for 30 secactive conditioning the treatment for 30 sec &rubbing theactive conditioning the treatment for 30 sec &rubbing thesurface with spongesurface with sponge

The resultswereThe resultswereUntreateddentinUntreateddentin--bond strengthbond strength--19.0to 21.7 Kg/cm19.0to 21.7 Kg/cm22

Active conditioningwit

h10% acid

Active conditioningwit

h10% acid--23.5 to 44.0 Kg/cm23.5 to 44.0 Kg/cm

22

Active conditioningwith 25%acidActive conditioningwith 25%acid--21.7 to 38.0 Kg/cm21.7 to 38.0 Kg/cm22


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RESIN CEMENTS:Based on methyl methacrylate and are essentiallylow

viscosity

Widely used for cementation of orthodontic bracketsand resin bonded restorations

APPLICATIONS:

For bonding of orthodontic brackets to acid etchedenamel

Cementation of porcelain laminates and inlays

Cementation ofall porcelain crowns and FPDS

Cementation of etched cast restoration


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CLASSIFICATION:Based on curing system

chemical cure-used for all type of restoration

light cure-use is limited to thin ceramic restorationswhich allows passage oflight like inlays,ceramic or

plastic orthodontic brackets

dual cure-used when material being bonded allowssome degree oflight penetation.Resin around margins

are cured using light to initiate setting and portionswhere light cannot penetrate cure subsequentlybychemical reaction.


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SUPPLIED AS,Chemical curedtwo paste system containing base and acceleratorsingle paste system with activator in the bonding liquid

Light cured-single paste system

COMPOSITIONComposition similar to mordern composites

Filler content has to be lowered and diluent monomeradded to adjust theviscosity


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POLYMERISATION

Chemically by peroxide amine systemLight activation

Both chemicaland light activation (dual cure)

PROPERTIES:COMPRESSIVE STRENGTH-180MPA

TENSILE STRENGTH-30 MPA

FILM THICKNESS-10-25m

IRRITANT TO PULPINSOLUBLE IN ORAL FLUIDS

HIGH POLYMERISATION SHRINKAGE

DO NOT ADHERE TO TOOTH STRUCTURE


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MANIPULATION:Etching the restoration-in ortho brackets a fine mesh

on the bonding side of bracket improvesretention,cement flows in to mesh and provide its

retention.silica coating can also be used to improvebonding

Etching the tooth surface-phosphoric acid

Bonding and curing

Removal of excess cement


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BONDING AND CURING

CHEMICALLY ACTIVATED SYSTEMS:2 paste system-2 components are combined by mixing

on a paper pad

single paste system with activator in bonding agent-

bonding agent is painted on the etched tooth surfaceas wellas on to the restoration.

setting occurs when the cement contacts the bondingagent on the tooth.


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DUALCURESYSTEMTwo components are mixed and light cured

Time of exposure should never be less than 40 seconds

Light curing gives high initial strength

Light curing polymerises the exposed cement at themargins of the restoration which is afffected byairinhibition


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COMPOSITESComposite- refers to a 3 dimensional

combination of at least twoor morechemically different materials,insoluble in

each other with a distinct interphase

separating the components

- highly cross linked polymeric materials reinforced bydispersion of glass ,crystalline or resin filler particlesand short fibres bound to the matrix by silanecoupling agents

MatrixFiller

Coupling agent


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CLASSIFICATIONACCORDING TO FILLER SIZE

MACRO FILLED COMPOSITES-8-12m

SMALL PARTICLE COMPOSITE-1-5m

MICRO FILLED COMPOSITE-0.04-0.4m

HYBRID COMPOSITE -0.6-1m

ACCORDING TO METHODOF DISPENSING:

2 PASTE SYSTEM

SINGLE PASTE AND LIQUID SINGLE PASTE SYSTEM

DISPOSABLE CAPSULES


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ACCORDING TO METHODOF ACTIVATION

CHEMICALLY ACTIVATEDCOMPOSITE

INITIATOR BENZOYL PEROXIDE

ACTIVATOR-N-N DIMETHYL PARA TOLUIDINE

LIGHT ACTIVATEDCOMPOSITE

UV- LIGHT ACTIVATED

INITIATOR-BENZOIN METHYL ETHER

ACTIVATOR-UV LIGHT OF WAVELENGTH 360 nm

VISIBLE LIGHT ACTIVATED

INITIATOR CAMPHOROQUININEACTIVATOR VISIBLE LIGHT OF WAVELENGTH (460-

480nm)

ACCELERATOR TERTIARY AMINES


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TYPESOFCOMPOSITES(ADA 27)TYPE I-POLYMER BASED FOR OCCLUSAL SURFACE

TYPE II-OTHER POLYMER BASED

CLASS I SEL

FCURED

CLASS II LIGHT CURED

GROUP I-ENERGY APPLIED INTRAORALLY

GROUP II-ENERGY APPLIED EXTRAORALLY

TYPE III- DUAL CURED


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y

LIGHTACTIVATED COMPOSITESU-VLIGHTACTIVATED:

activated byu-vlight ofwavelength 360nm a photoinitiator benzoin methyl ether undergoes photo

fragmentationwith

formation ofpolymerisationinitiating radicals and sets byaddition

polymerisation

VISIBLELIGHTACTIVATED:

Visible light is used for activation .diketone combines

with reducing agent tertiaryamine to form an excitedcomplex then breaks down to free radicals and reactioninitiated ,and undergo addition polymerisation


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PLASMA ARC CURINGLAMPS:

Uses xenon gas that is ionised to produce a plasmawhich is a high intensity white light ofa singlewavelength of 490nm and is filtered to remove heatand to allow blue light

ARGONLASERLAMPS:High intensity oflight radiation ofa single wavelength

of 490nm

Most widely used is quartz-tungsten halogen lamps


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COMPOSITIONOLIGOMERS- BISGMA(BOWENS RESIN),

UDMA,TEGDMA

FILLERS-GLASS,SILICA,ALUMINIUMSILICATE,LITHIUM LUMINIUM SILICATE,BORATEGLASSES

COUPLING AGENTS ORGANO SILANES

PACKAGING:

LIGHT CURED

SELFCURED/DUAL CURED


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PROPERTIESSETTING TIME chemically cured-3-5 min

POLYMERISATION SHRINKAGE-0.6-1.4%(HYBRID),2-3%(MICROFILLED)

THERMAL CO-EFFICIENT OF EXPANSION-25-38 *10

WATER SORPTION-0.3-0.6mg/sq.cm

SOLUBILITY-0.01-0.06mg/sq.cm

BOND STRENGTH-enameland dentin -20-30 mpaDEPTH OFCURE-2-2.5mm,40 seconds

ETCHING AND BONDING-34-37% phosphoric acid


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Cementation of ceramic or resin inlays and onlays.

Cementation of ceramicveneers.

Cementation of orthodontic bands.Direct bonding of orthodontic brackets.

Cementation ofall metal castings.

USESOFCOMPOSITERESIN


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ARTICLES

Trends Biomater. Artif. Organs, Vol 18 (2),

January 2005 http://www

1.Glass Ionomer Cement The Different GenerationsNagaraja Upadhya P and Kishore G.

2.Advances in glass-ionomer cementsCarel L. Davidson

JOURNAL OF MINIMUM INTERVENTION DENTISTRY

3.Bondingofhybrid ionomers and resin cements tomodifiedorthodontiband materials

Virginia a meyer,peter neuman,john m.powers.AJO-DO FEB 1999

cements in orthodontia

Documents