Download - 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