126536010 Dental Ceramics

8/16/2019 126536010 Dental Ceramics

1/55

Seminar -3

DENTAL CERAMICS DENTAL CERAMICS

CONTENT

IntroductionHistoryStructureClassificationCompositionPropertiesStrengt ening of dental porcelainCondensation of dental porcelain!iring procedure

Stages of maturityMetal "ceramicAll ceramicsApplication of ceramicsConclusionReferences

INTRODUCTION :Man as #een o#sessed $it duplicating% restoring and replacing &arious lost #ody parts li'et e lim#s% ear% nose and eyes $it artificial prost esis and teet #eing no e(ception)

T e *uest for an artificial prost esis similar to t e natural toot % #ot in function andaest etics% in t e oral en&ironment still remains as a foremost concern to t e dentist% $ icas led to t e use of CERAMICS in dentist)

WHAT ARE CERAMICS?

T e term ceramic is deri&ed from t e +ree' $ord ,'eramos%- $ ic means ,potter- or,pottery)- T is is related to a Sans'rit term meaning ,#urned eart %- #ecause t e #asiccomponents $ere clays from t e eart t at $ere eated to form pottery) .

Ceramic is an inorganic compound $it non"metallic properties typically composed ofmetallic /or semi metallic0 and non"metallic elements /e(ample AI 12 3% Ca20

" Kenneth J. Anusavice

1


2/55

Seminar -3

Dental ceramic is an inorganic compound $it non"metallic properties typically consistingof o(ygen and one or more metallic or semi metallic elements /e)g) Al% Ca% Li% Mg% 4% Si%

Na% Sn% Ti and 5r0 t at is formulated to produce t e $ ole or part of a ceramic #ased dental prost esis)

HISTORICAL EVOLUTION OF CERAMICS :

Till .6t Century dental tec nologie remian unde&eloped )• T e candidate material for artificial teet during t ese days $ere 7

• Human teet• Animal teet t at $ere car&ed to si8e and s ape of uman teet #ut t ey $ere

unsta#le to$ards coorosi&e agents in sali&a• I&ory 7 elep ant i&ory and #one contained pores $ ic got stained easily) 1

• T e current dental ceramics are far from t e early ceramics t at started #eing usedo&er 199 years ago)

• Early records of t e first ceramics used as dental materials date #ac' to .::;% $ enfrenc apot ecary ale(is duc ateau and parisian dentist Nic olas du#ois DeC eamnat manufactured t e first complete ceramic denture)

Nic olas du#ois De C eamnat

• T e initial use of ceramics materials in dentistry $as in t e o#tention of completedentures)

• Early in t e .


3/55

Seminar -3

+iuseppangelo !on8i

• T e restoration of indi&idual ceramic teet in t e oral ca&ity $as delayed until t elate .699s% $ en Logan constructed ceramic teet fused to t e metallic post so t att ese posts could function as an intra radicular for t e restoration)

• During last ;9 years %researc as foccused on impro&ing metal free systems andde&eloping superior materials regarding est etics and clinical performances to offer

patients se&eral alternati&es to restore missing or damaged teet ) 3

• .ceramic restoration in t e .


4/55

Seminar -3

Many dental ceramics contains a crystal p ase and a glass p ase #ased on silica structure)

T is structure is c aracteri8ed #y a silica tetra edran in $ ic a Si;

cations is positionedat t e center of a tetra edran $it 2 " anions at eac of t e four corners)

T e resulting structure is not closely pac'ed and as #ot co&alent and ionicc aracteristics)

T e regular dental porcelain% #eing glassy in nature% is largely non crystalline% and e( i#itsonly s ort range order in atomic arrangement% $ ic is referred to as dental glass

ceramics) T e only true crystalline ceramic used at present in restorati&e dentistry isalumina /Al1230% $ ic is ardest and strongest o(ide 'no$n) ;

CLASSIFICATION :

1. ased on c emical composition1) According to type3) According to use;) According to firing temp rature=) According to firing tec ni*ue?) According to su#strate metal:) Microstructural classification

4


5/55

Seminar -3

6) Processing tec ni*ue

.) BASED ON COMPOSITION:

A0 SILICATE CERAMICS7

C aracteri8ed #y an amorp ous glass p ase $it porous structure)

T e main components are Si2 1 $it small addition of crystalline Al 12 3% Mg2% 5r21 and or ot er o(ides)

Dental porcelain falls in t is category)

0 2FIDE CERAMICS7

Contain principal crystalline p ase /e)g)% Al 12 3% Mg2% T 21 or% 5r210 $it eit er no glass p ase or a small content of glass p ase )

C0 N2N 2FIDE CERAMICS7

T ese are impractical for use in dentistry #ecause of ig processing temperatures%comple( processing met ods or unest etic color and opacity)

D0 +LASS CERAMICS7

T ese are types of ceramics containing a glass matri( p ase and atleast one crystal p ase) ;

2. ACCORDING TO TYPE

a0 !eldspat ic porcelain #0 Leucite reinforced porcelainc0 Aluminous porcelaind0 +lass infiltrated aluminouse0 +lass infiltrated spinellf0 +lass ceramics ;

. ACCORDING TO !SE

a0 Ceramic for artificial teet #0 Gac'et cro$n% inlay and onlay ceramicc0 Metal ceramic

d0 Anterior #ridge ceramic

5


6/55

Seminar -3

". ACCORDING TO #IRING TEMPERAT!RE a$ Hig fusing " .399 C%$Medium fusing " ..9. t9 .399Cc$ Lo$ fusing " 6=9"..9.C

&$ ltra lo$ fusing " J6=9C;

'. ACCORDING TO #IRING TEC(NI)!E

.) Air fired /at atmosp eric pressure01) Kacuum fired /at reduced pressure03) Diffusi#le gas firing

*. ACCORDING TO S!BSTRATE META+

.) Cast metal

1) Sintered metal3) S$aged metal;) +lass ceramics=) CAD CAM) ;

:) METAL CERAMICS /P2RCELAIN ! SED T2 METAL0METAL !REE CERAMICS /ALL CERAMICS0

6) MICROSTR!CT!RA+ C+ASSI#ICATION At a microstructural le&el% ceramics can #e defined #y t eir composition of glass"to"crystalline ratio) T ere can #e infinite &aria#ility of t e microstructures of materialsBo$e&er% t ey can #e di&ided into four #asic compositional categories $it a fe$su#groups7a0 C m! "iti n Cate# r$ 1:

+lass"#ased systems /mainly silica0

#0 C m! "iti n Cate# r$ %:

+lass"#ased systems /mainly silica0 $it fillers% usually crystalline/Typically Leucite or a different ig "fusing glass0

c0 C m! "iti n Cate# r$ &: Crystalline"#ased systems $it glass fillers /mainly alumina0

d0 C m! "iti n Cate# r$ ': Polycrystalline solids /alumina and 8irconia0

COM(OSITION CATE)OR* 1:

)la""+,a"e- S$"tem" Am r!/ 0" )la""

• est mimic t e optical properties of enamel and dentin)

6


7/55

Seminar -3

• Deri&ed from group of mined minerals called feldspar and are #ased on y silicondio(ide /also 'no$n as silica or *uart80% and alumina /aluminium o(ide0)

• Aluminosilicates occurs naturally% and contain &arious *uantities of potassium andsodium% are 'no$n as feldspars)

• +lasses #ased on feldspar areResistance to crystalli8ation/de&itrification0Ha&e lo$ firing ranges

#iocompati#le

COM(OSITION CATE)OR* %

)la""+,a"e- S$"tem" it/ 2iller"

• !iller particles are added to t e glass composition to impro&e mec anical properties)And to control optical effects suc as opalescence %color% and opacity

• It is furt er su#di&ided into t ree groups)T e glass composition is similar to t e pure glass Category .) T edifference is &arying amounts of crystal types a&e eit er #een added to orgro$n in t e glassy matri()

• T e primary crystal types today are leucite% lit ium disilicate% or fluorapatite)

+eucite i s created in dental porcelain #y increasing t e 412 /potassium o(ide0 content oft e aluminosilicates glass) T is filler $as added to create porcelain t at could #esuccessfully fired on to t e metal su#structures)

+ithiu, &isi-icate crystals are made #y adding Li12 /lit ium o(ide0 to t ealuminosilicates glass) It also acts a flu(% lo$ering t e melting temperature of t e material)

)

S03cate# r$ %.1 Low-to-Moderate Leucite-Containing Feldspathic GlassT ese materials a&e #een called feldspat ic porcelains #y default)

Leucite

coefficient of t ermal e(pansion /CTE0%In i#it crac' propagation% t ere#y impro&ing t e material s strengt )T e amount of Leucite may #e ad@usted in t e glass #ased on t e type ofcore and re*uired CTE

S03cate# r$ %.%Hig "Leucite containing glass

7


8/55

Seminar -3

• +lassy p ase is #ased on an alumino"silicate glass)• T ese materials a&e #een de&eloped in #ot po$der li*uid% mac ina#le% and

pressa#le forms)• T e most $idely used &ersion is t e original iPs empress /i&oclar Ki&adent%

Am erst% ny0 #ut t ere are se&eral ot er products in t is category)• T is material is called a glass ceramic% $ ic as ad t e crystalline p ase gro$n

$it in t e glass matri( #y a process called ,controlled crystalli8ation of glass)-

S03cate# r$ %.& Lithium-Disilicate Glass-CeramicsIt is a ne$ type of glass ceramic% $ ere t e aluminosilicates glass as lit ium o(ide added)

E)g) IPS Empress II /no$ called as IPS e)ma(0%

COM(OSITION CATE)OR* &:

Cr$"talline+3a"e- "$"tem" it/ #la"" 2iller" co&er t e $ide scope of all"ceramic restorations% including &eneers% inlays% onlay% andanterior posterior cro$ns and #ridges)

E)g In"Ceram Spinell /alumina and magnesia matri(0 is t e most translucent% $itmoderately ig strengt and is used for anterior cro$ns)

In"Ceram Alumina /alumina matri(0 as ig strengt and moderate translucency and isused for anterior and posterior cro$ns)

In"Ceram 5irconia /alumina and 8irconia matri(0 as &ery ig strengt and lo$ertranslucency and is used primarily for t ree"unit posterior #ridges)

COM(OSITION CATE)OR* ':

( l$cr$"talline S li-"

• Ha&e no glassy componentB all atoms are densely pac'ed toget er$it out any inter&ening matri( to form a dense% air"free% glass"free polycrystallinestructure)

• T is structure ma'es difficult to dri&e crac' t roug atoms compared to atoms int e less dense and irregular net$or' found in glasses)

• T ese are relati&ely opa*ue and ence t ese ig strengt ceramics are used assu#structure material upon $ ic glassy ceramics are &eneered to ac ie&e pleasingaest etics)

• Se&eral processing tec ni*ues allo$ t e fa#rication of eit er a solid"sinteredaluminous o(ide /alumina% Al1230 or 8irconium o(ide /5r210 frame$or' =)

8


9/55


10/55

Seminar -3

• T e remaining slip is discarded% and t e frame$or' can #e remo&ed from t e moldafter partial sintering to impro&e t e strengt to a point $ ere t e frame$or' cansupport its o$n $eig t)

• Ceramics fa#ricated #y slip casting can a&e ig er fracture resistance t an t ose produced #y po$der condensation #ecause t e strengt ening crystallineParticles form a continuous net$or' t roug out t e frame$or')

• E)g) glass infiltration /In"Ceram% Kita 5a nfa#ri'0)• Limited application is #ecause of complicated series of steps% $ ic pro&ide a

c allenge to ac ie&ing accurate fit may result in internal defects t at $ea'en t ematerial from incomplete glass infiltration

• T e original In"Ceram and some partially sta#ili8ed 8irconia #loc's are fa#ricated #ased on slip casting of alumina or 8irconia)

(re""a3le

• Lost $a( met od is used to fa#ricate molds for pressa#le dental ceramics)• A&aila#le from manufacturers as prefa#ricated ingots made of crystalline particles

distri#uted t roug out a glassy material)• Pressa#le ingots are eated to a temperature at $ ic t ey #ecome a ig ly &iscous

li*uid% and t ey are slo$ly pressed into t e lost $a( mold)• Ad&antage is its good accuracy of fit

• sed only as core and frame$or' materials)• Pressa#le may #e used for inlays% onlay% &eneers% and single"unit cro$ns• E)g) IPS e)ma( 5irPress /I&oclar"Ki&adent0

CAD4CAM

• CAD"CAM ceramics are a&aila#le as prefa#ricated ingots• CAD"CAM ceramics are a&aila#le as prefa#ricated ingots ?

C m! "iti n:

Dental porcelains% to a large e(tent% are glassy materials)

+lasses are super"cooled li*uids non"crystalline solids $it only a s ort"range order int eir atomic arrangement) During cooling% molten glass solidifies $it a li*uid structureinstead of a crystalline structure) Suc a structure is called &itreous and t e process offorming it is 'no$n a" 5itri2icati n ) T e principal anion present in all glasses is 2 1 ion%$ ic forms &ery sta#le #onds $it small multi&alent cations suc as silicon% #oron%

10


11/55

Seminar -3

p osp orous etc) /e)g)% in silicon glasses% Si2 ; tetra edral are formed $ ic areresponsi#le for t e random net$or' of glass0) T ese ions are termed as glass formers)

!or dental applications% only t$o glass forming o(ides > silicon o(ide and #oron o(ide are

used to de&elop t e principal net$or')

Additional properties li'e lo$ fusion temperature% ig &iscosity% color and resistance tode&itrification is o#tained #y t e addition of ot er o(ides li'e potassium% sodium% calcium%

#oron or aluminium o(ides to t e glass forming lattice% Si2 ; )

(IG( #!SING PORCE+AINS

• Traditionally% t e #asic ingredients of t ese types of porcelains are feldspar 'aolin/clay0 and *uart8)

• !eldspar is t e primary constituent% and all porcelains #ased on feldspar are referred toas !ELDSPATHIC P2RCELAINS)

• Natural feldspars can #e eit er sodium feldspar /al#ite0 or potassium feldspar/ort oclase microline0 $ ic are minerals composed of potas /4 120% Soda /Na120Alumina /Al 12 30 and silica /Si2 10) T ese are necessary to increase t e t ermale(pansion compati#le $it metal coping)

• !or dental purposes% lig t potassium #ased feldspar is generally selected #ecause of itsincreased resistance to pyroplastic flo$ and an increased &iscosity) T e pyroplasticflo$ of dental porcelain s ould #e lo$ in order to pre&ent

rounding of margins%loss of toot from and2#literation of surface mar'ings)

• !eldspars are present in concentrations of := to 6=Q and undergo incongruent melting

at temperatures #et$een ..=9 °C and .=39 °C) Incongruent melting is t e process #y$ ic one material melts to form a li*uid plus a different crystalline material) Hence aglassy p ase is formed and suspended inside it are crystalline potassium aluminosilicate crystals 'no$n as Leucite)

• KAOLIN / CLA

11


12/55

Seminar -3

4aolin clay /Al 12 3% 1Si21% 1H120 ser&es as a #inder) en mi(ed $it $ater% it forms astic'y mass% $ ic allo$s t e unfired porcelain to #e easily $or'ed and molded) 2neating% it reacts limitedly $it feldspar /'no$n as pyroc emical reaction0 and t ere#y

pro&ides rigidly) It also ad eres to t e frame$or' of *uart8 particles and s rin'sconsidera#ly during firing) nfortunately% pure 'aolin is $ ite in color and reduces t etranslucency of porcelain) Conse*uently% it is included only in small concentrations of ; to=Q)

P RE ART5 Pure *uart8 is used porcelain as a strengt ener) T e main function of *uart8 /silica0

is to impart more strengt and firmness% and a greater translucency) Silica remainsunc arged at t e usual firing temperatures and ence contri#utes sta#ility to t e mass

during eating #y pro&iding a frame$or' for ot er constituents) It is present inconcentrations of .3 to .;Q) Traces of iron may #e present as impurities in t e *uart8 andmust #e remo&ed to pre&ent discoloration of porcelain)

MEDI!M/ +O0 AN !+TRA +O0 #!SING PORCE+AINST e lo$ and medium fusing porcelain po$ders are glasses $ ic a&e #een ground

from #loc's of matured porcelain) !or t is% t e ra$ ingredients are mi(ed and fused% andt e fused mass is t e *uenc ed in $ater) T e rapid cooling induces stresses in t e glass tot e e(tent t at considera#le crac's and fractures occur) T is process is referred to as!RITTIN+ and t e product so o#tained is called a frit) T e #rittle material is t en groundto a fine po$der of almost colloidal dimensions) During su#se*uent firing% little or no

pyroc emical reaction occurs% #ut t e glass p ase softens and flo$s slig tly) T issoftening allo$s t e po$der particles to coalesce toget er /sintering0 and form a densesolid) Ho$e&er% t e temperature must #e controlled to minimi8e t e pyroplastic flo$)T e ra$ ingredients for t e lo$ and medium fusing porcelains are #asically t e same asfor t e ig fusing porcelain po$ders #ut in addition contain #alancing o(ides flu(es)T ese additions tend to modify t e properties #y interrupting t e glass net$or' and enceare also 'no$n as glass modifiers) :

G+ASS MODI#IERS • T e sintering temperature of silica is too ig for use in &eneering est etic layers

#onded to metal su#structureB at suc ig temperature metal $ill melt) In additiont e t ermal contraction of coefficient of crystalline silica is too lo$ for t e alloys)

• ond #et$een t e silica tetra edral can #e #ro'en #y addition of al'ali metal ionsuc as Na%4 and Ca)

12


13/55

Seminar -3

• T ese al'ali decreases t e amount of cross"lin'ing #et$een t e o(ygen and t eglass forming elements li'e silica i)e)% t ey disrupt t e continuity of t e Si2 ; net$or')

• T ese #rea'age results inIncreased fluidityLo$er softening temperatureIncreases t ermal e(pansion

• T e modifier concentration s ould not #e too ig %ecause if too many tetra edral are disrupted% t ere may occur crystalli8ationduring t e porcelain firing operationsreduce t e c emical dura#ility /resistance to attac' #y $ater %acids andal'alis0

• T e most commonly used glass modifiers are potassium% sodium and calciumo(ides) T ese are introduced as car#onates t at re&ert to o(ides on eating) 2t ero(ides added lit ium o(ide% magnesium o(ide% p osp orous pento(ide etc 6

INTERMEDIATE O1IDES • T e addition of glass modifiers not only lo$ers t e softening temperature #ut also

reduces t e &iscosity of t e glass)• To o&ercome t is pro#lem intermediate o(ides lie aluminium o(ide /Al 12 30% are

added ):

BORIC O1IDE • oric o(ide / 12 30 ser&es as a glass modifier as $ell as a glass former)• Decreases &iscosity• Lo$ers softening temperature• !orms o$n glass net$or' 6

O(ACIF*IN) A)ENTS

• T e translucency of porcelain can #e decreased #y using an opacifying agent)• An opacifying agent is generally a metal o(ide"ground to a &ery fine particle si8e of

J= µm)• 5irconium o(ide is t e most common opacifiers• T e difference #et$een t e refracti&e indices of t e glass and t e opacifiers is t e

#asic mec anism #e ind opalescence)• Different $a&elengt of &isi#le lig t are scattered differently #y t e opacifying

particles)

13


14/55

Seminar -3

• T is effect depends upon t e si8e as $ell as t e &olume distri#ution of t e particles)

Particles in t e si8e range 9); to 9)6 µm generate a #lue tinge in reflecting lig t andturn yello$is red in transmitted lig t)

• Prefera#ly% t e si8e of t e particle s ould #e nearly t e same as t e $a&elengt of&isi#le lig t) :

CO+O!RING AGENTS • Pigmenting or colouring o(ides are added to o#tain &arious s ades needed to simulate

natural teet )• T ese pigments are produced #y fusing metallic o(ides toget er $it fine glass and

feldspar and t en regrinding to a po$der)• T is po$der is #lended $it t e un"pigmented porcelain po$der to o#tain t e proper

ue and c roma)• T e different colouring pigments used in dental porcelain are gi&en in t e ta#le #elo$)

6

Di e3ent c4-43in5 6i5,ents use& in &enta- 643ce-ain!erric o(ide /#lac'0% platinum gray +ray

C romium o(ide% Copper o(ide +reen

Co#alt Salts lue

!errous o(ide% Nic'el o(ide ro$n

Titanium o(ideellowish !rown

Manganese o(ide La&ender

C romium"tin% C romium"alumina Pin'

Indium ello$ I&ory

STAINS AND CO+OR MODI#IERSStains are generally lo$ fusing colored porcelains used to imitate mar'ings li'e

enamel c ec' lines% calcification spots% fluoresced areas etc) Stains in finely po$deredform are mi(ed $it $ater or glycerine and $ater or any ot er special li*uid) T e $et mi(is applied $it a #rus eit er on to t e surface of porcelain #efore gla8ing% or #uilt into t e

porcelain /internal staining0) Internal staining is prefera#le as it gi&es more lifeli'e results

and also pre&ents direct damage to t e stains #y t e surrounding c emical en&ironment)Color modifiers on t e ot er and are less concentrated t an stains and are used to o#tain

14


15/55

Seminar -3

gingi&al effects or ig lig t #ody colours% and are #est used at t e same temperature as t edental porcelain) :

G+A7ES AND ADD8ON PORCE+AIN

• +la8ing is done so to produce enamel li'e lustre after occlusal and morp ologiccorrections a&e #een made in a porcelain restoration) It also seals pores on t esurface of fired porcelain) :

• T e aim of gla8ing isSealing of open pores in t e surface of fired porcelain)Pro&ides trans&erse strengt

• ngla8ed porcelainlead to a#rasi&e $ear of t e opposing dentition or

increase t e rate of pla*ue accumulation <

+la8ing can #e of t$o types7

Self gla8ing /auto gla8ing0Add"on gla8ing)

• Sel2+#la6in# Defined as a &itrified layer t at forms on t e surface of a dental porcelain ceramiccontaining a glass p ase $ en t e ceramic is eated to a gla8ing temperature for a

specified time)gla8ing occurs at temperatures of


16/55

Seminar -3

o Difficult to apply e&enly and almost impossi#le to attain adetailed surface c aracteri8ation) 6

• Many ceramists prefer polis ing instead of gla8ing to control t e surface Iustre) <

• Studies a&e s o$n t at porcelain $it ig ly polis ed surface a&e compara#lestrengt $it gla8ed porcelain) T is o#ser&ation is of clinical importance #ecauseafter t e porcelain prost esis is cemented in t e mout % as clinician $ill ad@ust t eocclusion #y grinding t e surface of t e porcelain $it diamond #ur% $ ic remo&est e gla8e and mar'edly $ea'ens t e porcelain and surface is left in a roug condition) 6

• iley /.


17/55

Seminar -3

:) T e #rittleness → 9).Q deformation is sufficient to fracture porcelain #eforefracture)

6) ranium o(ide cerium o(ide is added to matc t e fluorescence of porcelain tot at of t e natural toot )

as it pre&ents pla*ue addition)f) Solu#ility is less) :

STREN)THENIN) OF DENTAL (ORCELAIN MET(ODS

.) De&elopment of residual compressi&e stresses1) Interruption of crac' propagation

DE9E+OPMENT O# RESID!A+ COMPRESSI9E STRESSES:

• Strengt ening is gained #y &irtue of t e face t at t e residual stresses must first #enegated #y de&eloping tensile stresses #efore any net tensile stress de&elops) T ere

are se&eral tec ni*ues for introducing t ese residuals compressi&e stresses into t esurfaces of ceramic articles) T ree of t ese met ods are discussed #elo$)

Ion e(c angeT ermal tempering

The3,a- C4,6ati%i-it :

I4n E;chan5e:

• T e tec ni*ue also called c emical tempering)

• T is process in&ol&es t e e(c ange of larger potassium ions for t e smaller sodiumions% a common constituent of a &ariety of glasses) If a sodium"containing glassarticle is placed in a #at of molten potassium nitrate% potassium ions in t e #ate(c ange places $it some of t e sodium ions in t e surface of t e glass article)

• T e potassium ion is a#out 3=Q larger t an t e sodium ion) T e s*uee8ing of t e potassium ion into t e place formerly occupied #y t e sodium ion creates largeresidual compressi&e stresses /roug ly :99 Mpa .99%999 psi0 in t e surfaces ofglasses su#@ected to t is treatment) T ese residual compressi&e stresses produce a

pronounced strengt ening effect)

17


18/55

Seminar -3

• Ho$e&er% t is process is #est used on t e internal surface of a cro$n% &eneer% or inlay #ecause t is surface is protected from grinding and e(posure to acids)

• 2ne study as s o$n t at grinding of only .99 µm from an e(ternal surface reducest e strengt of t e treated structure to its original &alue) !urt ermore% contact $itacidulated p osp ate fluoride o&er a cumulati&e time of 3 ours remo&es most of t eion"e(c anged layer as $ell)

• Not all ceramics are amena#le to ion e(c ange) !or e(ample% alumina core materials%DIC2R glass"ceramic core material% and some con&entional feldspat ic porcelain t atare ig ly enric ed $it potas feldspar /4 12% Al12 3)?Si2 10 cannot #e sufficiently ione(c anged $it potassium to $arrant t is treatment)

The3,a- Te,6e3in5:

• T e most common met od for strengt ening glass is #y t ermal tempering)• T ermal tempering creates residual surface compressi&e stress #y rapidly cooling

/*uenc ing0 t e surface of t e o#@ect $ ile it is ot and in t e softened /molten0 state)T is rapid cooling produces a s'in of rigid glass surrounding a soft /molten0 core) Ast e molten core solidifies% it tends to s rin'% #ut t e outer s'in remains rigid) T e pullof t e solidifying molten core% as it s rin's% creates residual tensile stresses in t e coreand residual compressi&e stresses $it in t e outer surface)

• !or dental applications% it is more effecti&e to *uenc ot glass"p ase ceramics insilicone oil or ot er special li*uids rat er t an using air @ets as it may not uniformlycool t e surface)

The3,a- C4,6ati%i-it :

• Most metals e(pand linearly $it temperature up to t e melting range) T us% ametal e(pands appro(imately t e same amount $ en eated from =9 oC to ?9 oC as itdoes from 199 oC to 1.9 oC)

• Dental porcelains #e a&e differentlyB t ey a&e different &alues in differenttemperatures ranges% and% as a result% t e t ermal e(pansion or contraction of t e porcelain cannot #e precisely matc ed to t at of t e alloy)

• Ideally% t e porcelain s ould #e under slig t compression in t e final restoration)T is o#@ecti&e is accomplis ed #y selecting an alloy t at contracts slig tly moret an t e porcelain on cooling to room temperature)

• Consider t ree layers of porcelain7t e outer t$o of t e same composition and t ermal contraction coefficient T e middle layer of a different composition and a ig er t ermal contractioncoefficient)

18


19/55

Seminar -3

en t e layers are #onded toget er and t e #onded structure is allo$ed tocool to room temperature)T e inner layer as a ig er coefficient of t ermal contraction and t uscontracts more as it cools) Hence% on cooling to room temperature% t e innerlayer produces compressi&e stresses in t e outer layers as pre&iouslydescri#ed for t ermal tempering)

• A similar rationale applies to porcelains and alloys for metal"ceramic restorations)• T e metal and porcelain s ould #e selected $it a slig t mismatc in t eir t ermal

contraction coefficients /t e metal t ermal contraction coefficient is slig tly larger0%so t at t e metal contracts slig tly more t an t e porcelain on cooling from t efiring temperature to room temperature) T is mismatc lea&es t e porcelain inresidual compression and pro&ides additional strengt for t e restoration) 6

INTERRU(TION OF CRAC7 (RO(A)ATION Dis3u6ti4n 4 C3ac< P346a5ati4n :

A furt er% yet fundamentally different% met od of strengt ening glasses andceramics is to reinforce t em $it a dispersed p ase of a different material t at is capa#leto indering a crac' from propagating t roug t e material) T ere are t$o different typesof dispersions used to interrupt crac' propagation) 2ne type relies on t e toug ness of t e

particle to a#sor# energy from t e crac' and deplete its dri&ing force for propagation) T eot er relies on a crystal structural c ange under stress to a#sor# energy from t e crac')T ese met ods of strengt ening are descri#ed later

Dis6e3si4n 4 a C3 sta--ine Phase:

en a toug % crystalline material suc as alumina /Al 12 30 in particulate form is added toa glass% t e glass is toug ened and strengt ened #ecause t e crac' cannot penetrate t ealumina particles as easily as it can t e glass) T e tec ni*ue as found application indentistry in t e de&elopment of aluminous porcelains /A. 12 3 particles in a glassy

porcelain matri(0 for PGCs) Anot er ceramic dental material t at uses reinforcement of aglass #y a dispersed crystalline su#stance is Dicor glass"ceramic) T e cast glass cro$n issu#@ected to a eat treatment t at causes micron"si8ed mica crystals to gro$ in t e glass)en glass"ceramic restorations are su#@ected to ig tensile stresses% t ese microscopic

crystals $ill disrupt crac' propagation% t ere#y strengt ening t e cro$n) In mostinstances% t e use of a dispersed crystalline p ase to disrupt crac' propagation re*uires aclose matc #et$een t e t ermal contraction coefficients of t e crystalline material and t esurrounding glass matri()

T3ans 43,ati4n T4u5henin5:

19


20/55

Seminar -3

A ne$ tec ni*ue for strengt ening glasses in&ol&es t e incorporation of a crystallinematerial t at is capa#le of undergoing a c ange in crystal structure $ en placed understress) T e crystalline material usually used is termed partially sta#ili8ed 8irconia /PS50)T e energy re*uired for t e transformation of PS5 is ta'en from t e energy t at allo$s t ecrac' to propagate) E(perimental $or' as s o$n t at transformation toug ening may #ea &ia#le met od for strengt ening dental porcelains) 2ne dra$#ac' of PS5 is t at itsinde( of refraction is muc ig er t an t at of surrounding glass matri() As a result% t e

particles of PS5 scatter lig t as it passes t roug t e #ul' of t e porcelain% and t isscattering produces an opacifying effect t at may not #e aest etic in most dentalrestorations)

CONDENSATION OF DENTAL (ORCELAIN

T/e !r ce"" 2 3rin#in# t/e !article" cl "er an- 2 rem 5in# t/e li80i- 3in-er i"9n n a" c n-en"ati n.

• Distilled $ater is t e li*uid #inder used most commonly) Ho$e&er% glycerin% propylene glycol or alco ol as also #een tried)

• T e aim of condensation Is to pac' t e particles as close as possi#le in order toreduce t e amount of porosityS rin'age during firing) 6

• T$o important factors% $ ic determine t e effecti&eness of condensation% areT e si8e and s ape of t e po$der particles) If only one"si8e particles are used% e&en t e greatest condensation ise(pected to lea&e a &oid space of ;= percent #et$een t e particles)it t$o si8ed particles% t e &oid space is reduced to1 = percent% and $itt ree or more si8ed particles% t e &oid space comes do$n to 11 percent) System t at uses t ree si8es of po$der is 'no$n as t e gap gradingsystem)

T e s ape of t e po$der particles also go&erns t e pac'ing density)Round particles produce #etter pac'ing compared $it angular particles ) :

• Se&eral met ods of condensation are employed/.0 Vi3rati n met/ - B t e paste is applied on to t e platinum matri( and &i#ratedslo$ly) T is #rings t e e(cess $ater on to t e surface% $ ic is t en dra$n a$ay$it a fine #rus or clean tissue) T e condensation occurs to$ards t e #lotted or

#rus ed area) E(cessi&e &i#ration s ould #e a&oided as it can cause slumping of t emass

20


21/55

Seminar -3

/10 S!at0lati n met/ - % a small spatula is used to apply and smoot t e $et porcelain) T e smoot ening action distur#s t e particles #ringing t em closer andalso t e $ater rises to t e surface% $ ic is remo&ed as descri#ed earlier)/30 Dr$ 3r0"/ tec/ni80e in&ol&es placement of dry po$der onto t e $et surface)T e po$der is placed #y a #rus to t e side opposite from an increment of $et

porcelain) As t e $ater is dra$n to$ards t e dry po$der% t e $et particles are pulledtoget er) 6

/;0 W/i!!in# met/ - % a large soft #rus is mo&ed in a lig t dusting action o&er t e$et porcelain) T is #rings e(cess $ater to t e surface and t e same #rus can #eused to remo&e any course surface particles along $it t e e(cess $ater)/=0 A com#ination of t e &i#ration and t e $ ipping met ods can also #e used)

T e mi( is first &i#rated and t en $ ipped $it a #rus )• T e most important factor in condensation is t e effect of surface tension) As t e

li*uid is $it dra$n% surface tension causes t e po$der particles to pac' closelytoget er) Ho$e&er% sufficient amount of li*uid s ould #e present so as to $et all t e

po$der particles) :

• CERAMOSONIC CONDENSOR

• T roug its ultrasonic function% it imparts lo$ amplitude% ig fre*uency &i#rationena#ling Condensation of moist porcelain particle)

• Impro&es su#structure of t e porcelain dispense trapped air • increase density

• Less s rin'age during firing

• En anced surface and strengt

FIRIN) (ROCEDURE4 SINTERIN) (ROCEDURE• Defined as process of eating closely pac'ed particles to ac ie&e interparticle

#onding and sufficient diffusion to decrease t e surface area or increase density oft e structure) T e partial fusion or compaction of glass is referred to as sinte3in5

• Most of t e t ermo c emical reactions in porcelain are completed during t emanufacturing process)

• T e role of firing is simply to sinter t e particles of porcelain po$der toget er toform a dense restoration)

• STA+ES ARE• (REHEATIN)

T e condensed mass is placed in front of or #elo$ t e muffle of a pre eated

furnace at an appro(imately ?=9 C /.199 !0 for lo$ fusing porcelain) T is

21


22/55

Seminar -3

permits remo&al of e(cess $ater and pre&ent t e sudden production of steamt at could result in &oids or fractures After pre eating for appro( = min% t e porcelain is placed into t e furnace andfiring cycle is initiated)

• FIRIN) Can #e fired #y follo$ing met odsTemperature controlled met od7furnance temperature is raised at a constant rateuntil a specified temperature is raisedTemperature >time control met od7 furnace temperature is raised at a gi&en rateuntil a preset temperature is reac ed% after $ ic temperature is maintained forspecific time till t e reaction is completed )preferred met od as produces uniformrestoration)

At t e initial firing temperature t e &oids are occupied #y t e atmosp ere of t efurnace) As t e sintering of t e particles #egins% t e porcelain particles #ond att eir points of contact )as temperature is raisedB t e sintered glass gradually flo$sto fill up t e air spaces) Second c ange occurs $it a furt er rise in temperature$ en t e particles fuse toget er #y sintering) As a continuous mass is formed%t ere occurs a decrease in &olume referred to as firing s rin'age /31"3:Q for lo$fusing and 16)3;Q for ig fusing0) After t e mass as #een fired% it is cooled&ery slo$ly #ecause rapid cooled mig t result in surface crac'ing and cra8ing)

Different media can #e employed for firing li'e7

A0 Air 0 Kacuum

C0 Diffusi#le gas

AIR #IRING PROCED!RE:ene&er air"firing met ods are employed% a &ery slo$ maturation period is

preferred to allo$ for t e ma(imum amount of entrapped air to escape) During firing slo$eating is done )t e porcelain is sintered $it in a range of atleast 39 oC to =9 oC #elo$ t ema(imum firing temperature) Suc a temperature $ill mature porcelain $it out loss ofcolor and ig densities can #e ac ie&ed)

"O#O$I%

u##les or &oids in t e fired porcelain are caused #y inclusion of air during firing or insome cases as a #y"product of &itrification of feldspar) Porosity reduces #ot translucencyand strengt of dental porcelain) Translucency depends on t e num#er and si8e of t eentrapped air #u##les) Large si8ed particles a&e fe$er #ut larger air &oids #et$een t em

22


23/55

Seminar -3

compared to small si8ed particles) !e$er #u##les% e&en of large si8e% gi&e impro&edtranslucency) 2n t e ot er and% fine si8ed particles a&e multiple small air #u##les

present in #et$een t em% $ ic ma'e t em ig ly opa*ue) It is% t erefore% clear t at porcelain po$ders fired in air must #e of necessarily coarse nature)

9AC!!M #IRING T is tec ni*ue is used to reduce porosity in dental porcelains) It $or's on t e #asis

of remo&ing air or atmosp ere from t e interstitial spaces #efore surface sealing occurs)Alt oug t e &acuum /:?9 torr0 remo&es most of t e air from interstitial spaces% some of itis left #e ind) it t e increase in temperature and #ecause of surface tension% t eremaining air spaces assume a sp erical appearance) en air at normal atmosp eric

pressure is allo$ed to enter t e furnace% it e(erts a compressi&e effect on t e surface s'in%

$ ic furt er compresses t e internal &oids to one tent of t eir original si8e) T is resultsin &ery dense porcelain $it &ery fe$ remaining #u##les and t at too of e(tremely smallsi8e)

#act43s t4 %e


24/55

Seminar -3

occurs #ecause t ese gases diffuse out$ard t roug t e porcelain or actually dissol&e in porcelain) :"6

VARIOUS STA)ES OF MATURIT*Se&eral stages of dental porcelain a&e #een identified $ en it is Usintered or Ufired ) T ecommon terminology used for descri#ing t e surface appearance of ungla8ed porcelain isU#is*ue )

+4= %is>ue:

T e surface of porcelain is *uite porous) T e grains of porcelain #egin to soften andUlense at t eir contact points) S rin'age is minimal and t e fired #ody is e(tremely $ea'or fria#le)

Me&iu, %is>ue:

Pores still e(ist on t e surface of porcelain% #ut t e flo$ of glass grains is increased) As aresult% any entrapped furnace atmosp ere t at could not escape &ia t e grain #oundaries

#ecomes trapped and sp ere s aped) A definite s rin'age is e&ident)

(i5h %is>ue:

T e flo$ of glass grains is furt er increased% t ere#y completely sealing t e surface and presenting smoot ness to t e porcelain) In t e case of non"!eldspat ic porcelains% a slig ts ine appears at t is stage) T e fired #ody is strong and any corrections #y grinding can

#e made prior to final gla8ing at t is stage) :"6

METAL CERAMICS:

T e c ief o#@ection to t e use of dental porcelain as a restorati&e material is its lo$strengt under tensile and s ears stress conditions)

T e met od #y $ ic t is disad&antage can #e minimi8ed is to #ond t e porcelain directlyto a cast alloy su#structure made fit t e prepared toot )

To fa#ricate t is restoration% a metal su#structure is $a(ed% cast% finis ed and eat treated/o(idi8ed0)a t in layer of opa*ue porcelain is fused to t e o(idi8ed metal surface toesta#lis porcelain" metal #ond and mas' t e color of su#structure) T en enamel anddentine porcelains referred as incisal and #ody porcelains% are fused to t e opa*ue

porcelain% s aped% staine to impro&e t e est etic appearance and gla8ed) 6

T*(ES OF METAL CERAMIC S*STEMS

24


25/55

Seminar -3

A large num#er of metal"ceramic systems a&e #een de&eloped for t e use in dentistry andt ey may #e classified as follo$s7

N2 LE METAL ALL2 S STEM7

HI+H +2LD 7

.) +old >platinum"palladium alloys1) +old >platinum"tantalum alloys

L2 +2LD .) +old >palladium"sil&er alloys

+2LD !REE7 .)Palladium sil&er alloys

ASE METAL ALL2 S STEM7

.) Nic'el c romium alloy1) Co#alt >c romium alloys .9

THE NATURE OF METAL CERAMIC ,OND

THE success of metal >ceramic cro$ns and fi(ed #ridges depends upon t e firmness oft e #ond #et$een metal and ceramic)

T erefore metal porcelain #ond can #e classified into 3 main components7

.) Mec anical1) Compressi&e3) C emical

MECHANICAL RETENTION 7

Depends upon good $etting of t e metal or metal o(ide surface #y t e porcelain)

Roug surface en ances t e #ond resistance against induced s ear stresses especially for #ase metal alloy system)

Ad&antages of an air a#raded surface o&er smoot surface for no#le metal alloys and #asemetal alloys are7

.) En ancement of $etta#ility of t e metal su#strate #y porcelain1) Some additi&e #ond strengt #ecause of mec anical interloc'ing of porcelain under

compression)3) Increased surface area for porcelain c emical #onding

Disad&antages are7

25


26/55


27/55

Seminar -3

.) METAL >P2RCELAIN7T e interfacial fracture occurs lea&ing a clean surface of metal%seen $ enMetal surface is completely depleted of o(ide prior to t e #a'ing of porcelain or$ en no o(ides are a&aila#le)

May also #e due to conyaminated or porous metal surfaces)1) Metal >o(ide porcelain7

T e metal o(ide porcelain at t e metal o(ide surface lea&ing t e o(ide firmlyattac ed to t e metal)Common in #ase metal alloy system)

3) Metal >metal o(ide7T is is an interfacial fracture in $ ic t e metal oside #rea's a$ay from t e metalsu#strate an d is left attac ed to t e porcelain)Common in #ase metal alloy system $ en t ere is o&er production of c romium and

nic'el o(ide at e interface);) Metal o(ide > metal o(ide7

T is fracture occurs t roug t e metal o(ide at t e interface and results from ano&er production of t e o(ide causing sand$itc effect #et$een metal and porcelain)

=) Co esi&e $it in metalT is type of fracture $ould only occur in cases for eg) ere t e @oint areas in t e

#ridges #rea's) Most unli'ely type of fracture for t e indi&idual metal >ceramiccro$n)

?) Co esi&e $it in t e porcelain7T is is t e optimum type of fracture in $ ic tensile failure occurs $it in t e

porcelain)in t is case t e #ond strengt e(ceeds t e strengt of porcelain)An ideal situation is created $ en t e o(ide film is only a fe$ molecules t ic' andforms a solid solution $it t e porcelain)t is is t e most common frature in t e iggold content alloys) .9

ALL CERAMIC S*STEMS

T e term of ,All ceramic- refers to any restorati&e material composed e(cessi&ely ofceramic% suc as !eldspat ic porcelain% glass ceramic% alumina core systems and certaincom#ination of t ese materials "

&' (sthetic Dent )**+, * . 012

A-5anta#e"

V Increased translucency

V Impro&ed fluorescence

27


28/55

Seminar -3

V +reater contri#ution of color from t e underlying toot structure

V Inertness

V iocompati#ility

V Resistance to corrosion

V Lo$ temperature electrical conducti&ity

C+ASSI#ICATION ?

. C4nventi4na- 64=&e3 s-u33 ce3a,ic• Hi Ceram > Alumina reinforced porcelain

• 2ptec HSP > Leucite reinforced porcelain

• Duceram L!C > Hydrot ermal lo$ fusing ceramic2. P3essa%-e ce3a,ic

• IPS Empress

• 2ptec Pressa#le ceramic. In i-t3ate& ce3a,ic

• In"Ceram". Casta%-e ce3a,ic

DIC2R Cera Pearl

'. Mechina%-e ce3a,ic• Cerec Kita#locs Mar' I and II

• Celay loc's

• DIC2R M+CACCORDIN) TO Cri"!in 1 ' R "en3l0m an- Sc/0lman 1 ;


29/55

Seminar -3

ACCORDIN) TO "0!! rtin# "tr0ct0re =Van N rt %>>%<• Reinforced ceramic core systems7

T e support for t e aest etic ceramic is pro&ided #y anot er ceramic material%$ ic as t e necessary ig strengt and toug ness #ut may lac' t e desiredaest etics /In"Ceram% Cerec% Celay% Procera All" Ceram0)

• Resin"#onded ceramic systems7T e support of t e ceramic is pro&ided #y t e toot structure itself% #y #onding t e

aest etic ceramic directly to t e enamel and dentine) In t is instance t e ceramic pro&ides t e necessary aest etics and t e strengt is pro&ided #y t e a#ility to #ond tot e toot tissues) T e materials a&aila#le for resin" #onded ceramic restorations are&arieties of glass >ceramics)

C4nventi4na- 64=&e3 s-u33 ce3a,ic

ALUMINA REINFORCED (ORCELAIN

It $as introduced #y McLean and H +ES in .


30/55

Seminar -3

• oric acid• Strengt and opacity of aluminous porcelain is dependent on alumina crystal7

• Si8e• S ape• Concentration

SI E OF ALUMINA CR*STALS 7

Finer t/e #rain "i6e 7 greater is strengt % #ut results in increased opacity% due to

ig difference in refracti&e inde( of t e t$o component %$ ic causes increased

scattering of lig t% defeating t e est etics)

C ar"e #rain "i6e 7 reduces strengt #ecause of t e ,notc ed effect- created on glass

#oundaries) T ey are opa*ue) +rain si8e on a&erage s ould #e 1= Wm /ma() #eing3: Wm0 t at$ould allo$ lig t transmission of atleast .9".=Q on . mm t ic' discs and fine enoug to gi&esufficient strengt s)

S/a!e 7 rounded grains are prefera#le o&er angular ones as latter interface $it t e flo$ of t eglass P ase producing fla$s around grains and reducing strengt )

C ncentrati n of alumina crystals s ould range from ;9"=9Q #y $eig t)

Hig er concentration Pre&ent complete flo$ and $etting #y t e glass matri()

Commercially a&aila#le product is Hi+Ceram =Vita


31/55

Seminar -3

sed #ot for incisal and #ody portions #eing more aest etics

A-5anta#e":

• Lac' of metal or opa*ue su#structure %good translucency

• Moderate fle(ure strengt % ig er t an con&entional !eldspat ic porcelains• A#ility to #e used $it out any special la# e*uipments

Di"a-5anta#e":

• Margins inaccuracy caused #y porcelains sintering s rin'age• Potential to fracture in posterior teet• Hig $ear of opposing toot due to ig Leucite content

No clinically pu#lis ed studies on 2ptec HSP

DUCERAM LFC:

• Also 'no$n as ydrot ermal lo$ fusing ceramics)• It is a lo$ fusing ceramic% composed of an amorp ous glass containing ydro(yl ions)• Properties7 compared to !eldspat ic porcelain

+reater densityHig er fle(ure strengt+reater fracture resistanceLo$er ardness

• ecause of t e a#sence of Leucite crystals% t e ardness of t e materials and its a#ilityto a#rade t e opposing natural toot structure is reduced)

• It is t en strengt ened #y ion e(c ange mec anism in&ol&ing ydro(yl ions t usdecreases t e surface micro fla$s and increase fracture resistance)

• Ho$e&er% t ere are no clinical studies to su#stantiate t e manufactures claim t at t ematerial is less a#rasi&e t an feldspat ic porcelain) Ho$e&er% t e result of . yearclinical study recently conducted for manufacture r seems to indicate t at t e material$ears at a rate e*ui&alent to t at of natural toot enamel / S o$t$ell G% eard CC% Lang%Lang R%unpu#lis ed data .


32/55

Seminar -3

USES: Ceramics inlays% &eeners% and full contour cro$ns

(RESSA,LE )LASS CERAMIC

IPS empress 2ptec pressa#le ceramics

A glass ceramics is material t at is formed into desired s ape as a glass% and t en su#@ectedto a eat treatment to induce partial de&itrification /t at is loss of glassy structure #ycrystalli8ation of t e glass0)

T e crystalline particles% needles or plates formed during t is ceramming process ser&e to

interrupt t e propagation of t e crac's in t e material $ en intraoral force is applied%causing increased strengt and toug ness .

ADVANTA)ES :

• Lac' of metal• Translucent ceramic core• Moderately ig fle(ure strengt• E(cellent fit

• E(cellent aest etics

DISADVANTA)ES:

• Potential to fracture in posterior areas• se of resin cement to #ond cro$n micromec anically to toot structure• Re*uire special e*uipment)/pressing o&en and die material)0

I(S EM(RESS :

• A leucite"reinforced glass"ceramic material $as first descri#ed #y o l$endand Sc arer .1

T is type of !eldspat ic porcelain is supplied in t e ingot form)T e ingot are eated and molded under pressure to produce t e restoration)A full contour cro$n is $a(ed% in&ested and placed in speciali8ed mold t at as analuminium plunger)T e ceramic ingots are placed under t e plunger% t e entire assem#ly is eated to..=9C and t e plunger presses t e molten ceramic into t e mold)T e final s ade of t e cro$n is ad@usted #y staining or &eneering)

32


33/55

Seminar -3

In t e &eneering tec ni*ue% t e original $a( >up is cut #y a#out 9)3 mm)After molding and #a'ing as descri#ed% feldspat ic porcelain is added to t e surfaceto o#tain full contour and t e correct s ade)

O(TEC (RESSEA,LE CERAMIC :

Type of !eldspat ic porcelain $it increased lecucite content% processed #y moldingunder pressure and eat)sed for >

!ull contour restoration 7 inlays% &eneers% full cro$ns)Can #e used as core material% for &eenering con&entional po$der alurrytec ni*ues $it ig Leucite content !eldspat ic porcelain% similar to2ptec HSP porcelain)

Crystalline Leucite particle si8e is reduced and content is increased $ ic result inincrease in fle(ural strengtecause of ig Leucite content a#rasion of opposing natural teet is ig ) :%6%..

INFILTERED CERAMICS:

IN+CERAMSAD2 N de&eloped INCERAM in .


34/55

Seminar -3

= &ol Q porosity .1

T e microstructure consists of #loc'y alumina grains of &arious si8es and s apes)E&idence of grain pull"out% #ridging and crac' deflection $as reported $it t is type ofceramic indicati&e of efficient crystalline reinforcement% and accounting for mec anical

properties in t e range of eat"pressed lit ium disilicate glass"ceramics)It as also #een suggested t at t e coefficient of t ermal e(pansion mismatc

#et$een t e alumina crystals and t e infiltration glass could contri#ute to strengt eningdue t ermal residual stresses) T e presence of large alumina crystals $it a igrefracti&e inde(% and a non"negligi#le amount of porosity% account for some degree ofopacity in t is all"ceramic system) Spinel"#ased slip"cast ceramics offer #ettertranslucency % similar to t at of lit ium disilicate eat"pressed ceramics% at t e e(penseof mec anical properties

irc nia+t 0#/ene- al0mina "li!+ca"t ceramic" comprise3; &ol Q alumina and33 &ol Q of .1 mol Q ceria"sta#ili8ed 8irconia /.1Ce"T5P0)T e glass p ase represents appro(imately 13 &ol Q of t e final product% $it a#out 6&ol Q residual porosity )T e dual crystalline reinforcement in t is system allo$s t$o types of strengt eningmec anisms7/.0 T e stress"induced transformation in 8irconia grains produces compressi&e stresses$it in t e transformed grains and surrounding glassy matri(% as $ell ascircumferential tensile stresses around t e grains% accompanied #y micro crac'nucleation) Transgranular fracture is difficult in 8irconiaB t is represents an efficientstrengt ening mec anism)/10 Crac' deflection% contact s ielding and crac' #ridging are e(pected from t e presenceof large alumina grainsT e com#ination of t ese t$o strengt ening mec anisms e(plains $ y alumina"8irconiaslip"cast ceramics offer t e ig est fle(ural strengt and fracture toug ness of all slip"castceramics)

INDICATION:

In+ceram "!innel:

Anterior single unit inlays%onlays cro$ns and &eeners)

In clinical situations $ ere ma(imum translucency is needed

In ceram al0mina:

Anterior and posterior cro$ns

34


35/55

Seminar -3

Anterior 3 unit prost esis

Inceram 6irc nia:

ecause of ig strengt and fracture toug ness it is indicated for posterior cro$nsand !PD)

#a%3icati4n P34ce&u3eAn All"Ceramic restoration system INCERAM is #ased on t e slip casting of an

alumina core $it its su#se*uent glass infusion) After t e impression is ta'en t e die is poured $it special gypsum supplied $it INCERAM% t en t e INCERAM AL MINA isapplied onto t e die)

T e alumina po$der is mi(ed $it deioni8ed $ater supplied in pre"measured container)Dispensing agent is added to create a omogenous mi( of alumina in $ater) T is mi(tureis sonicated in KITAS2NIC t us initiating t e dispersion process) T en &acuum is appliedto remo&e t e air #u##les)

T is solution of alumina is referred to as ,slip- $ ic is t en painted onto t e gypsum die$it a #rus ) T e alumina is #uilt up to form a core for t e ceramic toot ) T e $ater isremo&ed #y t e capillary action of t e porous gypsum% $ ic pac's t e particles into arigid net$or')

T e aluminous core is t en placed in t e IN"CERAMET furnace and sintered) T e cyclein&ol&es a slo$ eating of appro(imately 1 oC min to ..19 oC for 1 ours to produceappro(imation of t e particles $it minimal compaction and minimal s rin'age ofalumina) Sintering is only a#out 9)1Q t us an interconnected porous net$or' is createdconnecting pores on t e outer surface $it t ose on t e inner surface)

Lo$ &iscosity lant anum aluminosilicate glass is used to fill t e pores in t e alumina) T eglass is mi(ed $it $ater and placed on a platinum > gold alloy s eet) T e e(ternal

surface of t e core is placed on t e glass% $ ic is eated in t e IN"CERMET to ..99 oCfor ;"? ours) T e glass #ecomes molten and flo$s into t e pores #y capillary diffusion)T e e(cess glass is remo&ed #y sand#lasting $it alumina particles)

T e last step is fa#rication of INCERAM restoration in&ol&es application ofaluminous porcelain to t e core to produce t e final form of restoration) T e lo$ &iscositylant anum glass is used to infiltrate t e alumina core in INCERAM) T is s ould #e in airen&ironment as recommended #y t e manufacture) T e INCERAM aluminous glassceramic produced #y lant anum glass infiltration is a#out =9Q translucent as dentin)

35


36/55

Seminar -3

In clinical situations $ ere t ere is a discolored preparation or a cast post and core t isincreased opacity o&er t e dentin is ad&antageous $ere as $ en ma(imum translucency isnecessary INCERAM AL MINA is pro#lematic)

CASTA,LE )LASS CERAMICT e first commercially a&aila#le casta#le ceramic material for dental use% DIC2R% $asde&eloped #y corning glass $or's and mar'eted #y Dentsply international .

Cla""i2icati n 2 Ca"ta3le Dental )la"" Ceramic":

!lucoromicas DicorApatite glass ceramics pearl 2t er glass ceramics Lit ia %Calcium P osp ate

DICOR A Polycrystalline glass ceramic is a material t at is formed into t e desired s ape asa glass and su#se*uently eat"treated under controlled conditions to induce partialde&itrification)T e fa#rication met od uses lost $a( and centrifugal casting tec ni*ue similar tot ose used to fa#ricate alloy castings)A full contour transparent glass cro$n is cast at .3=9 C t en is eat treated at .9:=C for .9 ours) T is eat treatment is 'no$n as ceramming causes partialcrystalli8ation /==Q0 of tetrasilic mica li'e crystals)T ese crystals function in 1 $ays7

T ey create a relati&ely opa*ue material out of t e initially transparentcro$n and increase t e fracture resistance and strengt of t e ceramic)Crystals are also less a#rasi&e to opposing toot structure)

P346e3tiesT e p ysical properties of DIC2R are gi&en in t e ta#le)

(RO(ERT* DICOR ENAMEL

FELDS(ATHIC(ORCELAIN

Density% g)cm3 1): 3)9 1);

Translucency 9)=? 9);6 9)1:

Modulus of rupture psi 11999 .=99 ..999

36


37/55

Seminar -3

Compressi&e strengt % psi

.19999 =6999 1=999

Modulus of Elasticity%

psi(.9?

.9)1 .1)1 .1)9

Micro ardness 3?1 3;3 ;=9

Esthetic )ua-itiesDIC2R restorations are ig ly est etic #ecause of t eir translucency% $ ic closely

matc es t at of natural toot enamel) T e numerous small mica crystals t at constitutecasta#le ceramic closely matc t e inde( of refraction to t e surrounding glass p ase) Inaddition% t e casta#le ceramic permits a one"piece restoration made entirely of t e samematerial% and no opa*ue su#structure e(ists to impede lig t scattering) A c ameleon effectis seen $it DIC2R restorations in $ ic t e restoration ac*uires a part of t e color fromad@acent teet and fillings as $ell as t e underlying cement lute) Application of ane(ternal coloring system allo$s independent control o&er ue% c roma and &alue)Ho$e&er% as mentioned #efore% t ere are c ances of losing t is e(ternal layer t ere#ydefeating t e #est of est etics)

P3ecisi4n O #it

T e resistance of DIC2R to c emicals and staining agents also compares fa&oura#ly$it con&entional feldspat ic porcelains) Little $ear of t e cast ceramic or t e opposingdentition occurs $ en using DIC2R restorations) T$o reasons for t is property are7

a) Closely matc ing ardness #et$een t e cast ceramic material and natural enamel) #) T e DIC2R s ading porcelains contain minimal a#rasi&e opacifying agents)

Tissue Acce6tanceDIC2R is c emically inert and as s o$n to pass all t e #iocompati#ility tests) T e

periodontal tissue reaction to DIC2R is considered *uite fa&ora#le #ecause.) T ere is no need for opa*ue porcelains to mas' t e metal su#structure) T esecoarse grained opa*ue porcelains generally promote t e ad erence of pla*ue)

1) T e a#sence of an opa*ue layer allo$s t e tec nician to o#tain natural contouringoften found in metal ceramic restorations)

Little discomfort occurs on contact $it ot or cold foods #ecause of its e(tremely lo$t ermal conducti&ity and a coefficient of t ermal e(pansion% $ ic closely matc es t at of natural enamel)

37


38/55

Seminar -3

Ra&i453a6hic )ua-itiesT e radiograp ic density of DIC2R is similar to t at of enamel allo$ing proper

e&aluation of t e underlying structures and t e margins) A&vanta5es

.) E(cellent marginal fit1) Relati&ely ig strengt3) Surface ardness and occlusal $ear is similar to enamel;) Can reproduce $a( patterns precisely #y using t e lost $a( tec ni*ue=) Simple uncomplicated fa#rication from $a( up to casting% ceramming and colouring?) Ease of ad@ustment:) E(cellent aest etics resulting from natural translucency6) In erent resistance to pla*ue accumulation /se&en times less t an on t e natural

toot surfaces0) Disa&vanta5es

.) C ances of losing lo$ fusing feldspat ic s ading porcelains% $ ic a&e #eenapplied for good colour matc ing)

!sesInlays% onlay% complete cro$ns and possi#ly partial toot co&erage restorations) It is

not indicated for fi(ed partial denture or remo&a#le partial denture a#utments $it deeprests or internal attac ments)

CERA PEAR+Casta#le apatite ceramic $as first de&eloped #y Ho#o and ioceram +roup asCa2"P 12 ="Mg2"Si2 1 glass ceramic)Cera Pearl is composed of Ca2% P 12 =% Mg2% Si21 and traces of ot er elements)Ca2/;=Q0 and P 12 = /.=Q0 are t e main ingredients in glass formation) T ey areessential for formation of ydro(ylapatite crystals as $ell) Mg2 /=Q0 elps in t eformation of ydro(yapatite and along $it Ca2 decreases t e &iscosity of t e

compound $ en melted) Si2 1/3;Q0 in com#ination $it P 12 = forms t e matri()!urt er Si2 1 regulates t e t ermal properties)

ecause t e crystalline constituent is similar to natural enamel% Cera Pearl is *uite #iocompati#le) T e oung s modulus% tensile strengt and compressi&e strengt of CeraPearl are apprecia#ly ig er t an con&entional porcelains)

(/$"ical !r !ertie"

V Coefficient of t ermal e(pansion7 ..)9 ( .9"? oC)

V oung s modulus > .93 +pa

38


39/55

Seminar -3

V Casting s rin'age > 9)=3Q

V !le(ural strengt similar to Dicor

V iological properties > Dense material% c emically sta#le% PH similar tonatural enamel

V Non to(ic #iocompati#le

Lit/ia 3a"e- #la"" ceramic

De&eloped #y rgu

C m! "iti n: It contains mica crystals and eta spodumene crystals of Li2% A. 12 3);Si2 1after eat treatment)

Calci0m !/ "!/ate #la"" ceramic

V Reported #y 4i ara and ot ers

V Com#ination of calcium p osp ate and p osp osus pento(ide plus traceelements

V Cast at .9=9ZC in gypsum in&estment mold

V Clear cast cro$n is con&erted to a crystalline ceramic #y eat treating at?;=ZC for .1 ours

Di"a-5anta#e"

V ea'er t an ot er casta#le ceramics

V 2pacity reduces t e indication for use in anterior teet

SHRIN7 FREE CERAMICCEREST2RE

It is a s rin'"free alumina cro$n de&eloped #y t e Coors iomedical Co) and latersold to Go nson Go nson) It is fa#ricated using lost $a( tec ni*ue and t en in@ectionmolding to produce a coping) MgAl 12 ; spinell and an alp a"alumina o(ide ma'e t e corereplaced #y Alceram) T e use of a s rin'"free ceramic coping formed on an epo(y die

#y a transfer molding process o&ercomes t e limits and firing s rin'age of con&entionally

39


40/55

Seminar -3

produced aluminous porcelain @ac'et cro$ns) T e Cerestore coping is &eneered $itcon&entional aest etic porcelain)

!le(ural strengt 7

It is appro(imately .=9 Mpa)

MACHINA,LE CERAMICS:

,rie2 /i"t r$:

De&elopment of CAD"CAM /Computer Assisted Design"Computer AidedManufacturing0 system for t e dental profession #egan in .


41/55


42/55

Seminar -3

DCS (RECIDENT:

Comprises of a Preciscan laser Scanner and Precimill CAM multitool milling centre)

T e DCS soft$are automatically suggests connector si8es and pontic forms for #ridges) Itcan scan .; dies simultaneously and mill up to 39 frame$or's unit in one fully automatedoperation) It is one of t e fe$ systems t at can mill titanium and fully dense sintered8irconia) An in &itro study s o$ed t at marginal discrepancies of alumina and8iroconia #ased posterior fi(ed partial denture mac ined #y t e DCS system $as #et$een?9 Wm to :9Wm

CERCON:

Commonly referred to as a CAM system% it does not a&e a CAD component) T e systemscans t e $a( pattern and mills a 8irconia #ridge coping from presintered 8irconia

#lan's% $ ic is sintered at .%3=9ZC for ?"6 rs) Keneering is done $it a lo$fusing% leucite free cercon Ceram to pro&ide est etic contour) Marginal adaptation forcercon all ceramic cro$ns and fi(ed partial dentures $as reported 3.)3Wm and 1


43/55

Seminar -3

milled occlusal surface and a mac ined ig strengt ceramic core) T e aim ofCICER2 is to mass produce ceramic restoration at one integrated site) It includesrapid custom fa#rication of ig strengt alumina coping and semi finis ed cro$ns to

#e deli&ered to dental la#oratories for porcelain layering finis ing .

LAVA CAD4CAM S*STEM

Introduced in 1991% used for fa#rication of 8irconia frame$or' for all ceramicrestorations) T is system uses yttria sta#ili8ed tetragonal 8irconia poly crystals / "T5P0 $ ic a&e greater fracture resistance t an con&entional ceramics) La&asystem uses a laser optical system to digiti8e information) T e La&a CADsoft$are automatically finds t e margin and suggests a pontic) CAM produces an enlargedframe$or' to compensate s rin'age) A partially sintered 8iroconia #loc' is selectedfor milling) Milled frame$or' undergoes sintering to attain final dimensions%density and strengt ) Studies on marginal adaptation of "T5P #ridges processed $itLa&a system for 1 milling times /:= mins Ks =? mins0 did not affect t e marginaladaptation /?. 1= Wm Ks =< 1. Wm 0 .?

CAD4CAM Re"t rati5e Tec/ni80e: .=

Consists of Hand eld scanning de&ice t at digitally records t e form and margins of t e preparation)T e scanners re*uire a dry field and soft tissue t at must #e t oroug ly separateat t e le&el of t e margin from t e ard tissue)T e soft tissue diode laser /2dyssey Na&igator% I&oclar Ki&adentB +ENTLEray


44/55

Seminar -3

SOFT TISSUE DIODE LASER

Alternati&e soft tissue management tec ni*ues include electro surgery and standardmanual retraction tec ni*ue .

Depending on t e system used% t e clinician can see t e preparation magnified ont e computer screen as t e scan is #eing processed)T$o #asic tec ni*ues can #e utili8ed for CAD CAM restorations)

Chai3si&e @ a sin5-e8visit techni>ue Inte53ate& Chai3si&e -a%43at43 CAD CAM P34ce&u3e )

Chai3si&e CAD CAM Techni>ue:T e c airside tec ni*ue in&ol&es scanning t e preparation and t en fa#ricating t erestoration in t e milling de&ice /CEREC 3% SironaB E;D% D;D TECH0)Prior to scanning% a &ery t in layer of po$der is distri#uted o&er t e preparationusing t e CEREC system)During scanning% t e clinician must ensure t at all margins of t e ca&ity arecaptured #y t e scan and &isuali8ed) T e CEREC 3 uses still images% $ ile t e E;D uses a laser in t e and eldscanning de&ice A t ird system% CICER2% $as de&eloped in T e Net erlands and used a pressing%

sintering% and milling tec ni*ue prior to la#oratory finis ing of t e restoration)!or C airside CAD CAM restorations% an est etic% strong material re*uiringminimal post"milling est etic ad@ustment to minimi8e C airside time is needed)

• Leucite"reinforced glass ceramics /IPS Empress CAD% I&oclar Ki&adentBParadigm C% 3M ESPE0

• lit ium disilicate glass ceramics /IPS e)ma(% I&oclar Ki&adent0

A-5anta#e"

2ne"&isit fi(ed restorati&e procedure No impression ma'ing No temporary restoration re*uiredReduced potential for toot sensiti8ation

No la#oratory costs No model or die pouringAccuracyLess opportunity for error compared to traditional tec ni*ue

Aids prep &isuali8ationPro@ects a state"of"t e"art image

44


45/55

Seminar -3

Di"a-5anta#e"

Less conser&ati&e t an direct composite fillingsSlig tly less e(acting fit t an la#oratory"made

Est etic capa#ilities are limited 1'

Soft tissue management more critical t an $it traditional tec ni*ueDepending on t e material and patient% customi8ation may #e re*uiredHig learning cur&eHig er production re*uired to co&er capital in&estment

CASE 1. ANTERIOR ESTHETIC ONE 1@

Ma(illary incisor pretreatment CAD CAMmilled finis ed restoration

!inis ed CAD CAM restoration placed

CASE %. RE(LACEMENT OF FAILIN) AMAL)AMS

CAD CAM conser&ati&e preparation design preser&es more of t e natural toot structurecompared $it a cro$n and offers t e clinical longe&ity of gold $it out t e est etic

45


46/55

Seminar -3

dra$#ac's) en using t e current generation #onding ad esi&es according to t emanufacturer s instructions% t e CEREC ceramic $ill recreate a toot li'e strengt

Amalgam restoration and caries pre"treatment preparation)

Completed est etic CAD CAM restoration /IPSempress CAD 0

INTE)RATED CHAIRSIDE LA,ORATOR* CAD4CAM TECHNIBUE

• Re*uires t$o &isits)• T e clinician eit er can scan t e preparation directly and t en send t e scan to t e

la#oratory% or can ta'e a traditional impression% after $ ic a stone model is pouredand t e la#oratory scans t e stone model)

46


47/55


48/55

Seminar -3

Ca"e (re"entati n: Inte#rate- C/air"i-e La3 rat r$ Tec/ni80e

Preoperati&e &ie$7 discolored central incisor cro$n and &eneer preparation

$it disparity in color

Scanning image from dental office impression milled usingCAD CAM

In la# image of cro$n In la# image of &eneer design

48


49/55

Seminar -3

Poured model and CAD milled $a( CAD ceramic #loc's used for t erestoration

Milled restoration ceramic layering in process

!inal seated cro$n and &eneer

COM(ARISON OF THE ALL CERAMIC S*STEMS: 11

1. STREN)TH:All systems a&e ade*uate strengt for single units #ut significantly less t an t atof ceramic metal cro$ns)A#ility of #onding to toot structure pro&ides additional strengt ening

mec anism)

49


50/55

Seminar -3

Dicor is strengt ened t roug t e partial recrystalli8ation of t e glass t roug aceramming process)In"ceram as ig est fle(ural strengt &alues for all t e ceramic system and can

#e used for multiple unit #ridges)IPS Empress and 2ptec pressa#le ceramic% strengt ened #y dispersion of Leucitecrystals t roug out t eir internal structure)

Duceram L!C% strengt ened #y an ion e(c ange mec anism in&ol&ing ydro(ylions)

%. !A RICATI2N TECHNI ES7it e(ception of 2ptec HSP and Duceram system% all ceramic system usespecialciali8ed e*uipments and tec ni*ues) So can #e considered disad&antage

#ecause of t e added cost of fa#rication)

&. MAR+INAL !ITit e(ception of t e mac ined ceramics restoration% t e fit of t e all ceramiccro$ns to t e underlying toot structure is e(tremely accurate)Compenstion fordiscrepancy or gaps can #e made #y using resin cements)

'. EAR 2! 2PP2SIN+ T22TH STR CT RE7 All of t e Leucite containing all ceramic materials $ears opposing natural

toot ) IPS Empress 2ptec HSP 2ptec 2PC Dicor Duceram

ALL+CERAMIC (OSTS AND CORES:

Endodontically treated teet often need a post and core as foundation for t e finalrestoration)] T e restoration of anterior non&ital teet $it metal posts and cores andall"ceramic restorations may lead to compromised aest etics #ecause of t e semitranslucence of ceramics and t e opacious metal su#structure of t e underlying post

and core) Depending on t e t ic'ness and t e opacity of t e luting cement and t eall"ceramic restoration% t e metal post and core may s ine t roug or at least decreaset e dept of translucency of t e restoration)] In addition% metal posts may also s inet roug in t e cer&ical root areas% t us altering t e appearance of t in gingi&al tissue)]]!urt ermore% especially $ en nonprecious alloys are used for post"and"corefa#rication% corrosion products may deposit in t e gingi&al tissues or cause rootdiscoloration) Almost simultaneously $it t e introduction of t e current all"ceramicsystems% t e use of t e all posts and cores $as suggested as an alternati&e to sol&e

t e est etic pro#lems t at metal posts and cores e( i#it)

50


51/55

Seminar -3

ADKANTA+ES7

• Dentine li'e s ade it is related to t e deeper diffusion and a#sorption of t etransmitted lig t in t e ceramic core mass

• An all ceramic restorations transmits a certain percentage of t e incident lig t tot e ceramic core and t e post on $ ic it as #een placed t us t e color of t efinal restorations $ill #e deri&ed from an internal s ade similar to optical

#e a&ior of t e natural teet• Does not reflect intensi&ely t roug t in gingi&al tissues) It pro&ides an

essential dept of translucency in t e cer&ical root areas• E(cellent #iocompati#ility and does not e( i#it gal&anic corrosion

DISADKANTA+E7

• Relati&ely lo$ fracture strengt and fracture toug ness)

Dental Ceramic material 0"e- 2 r all ceramic ! "t an- c re

^ Con&entional dental ceramics

^ Hig toug ness ceramic " In ceram)

^ Dense sintered alumina ceramic " Procera)

^ 5irconium o(ide ceramics

Tec/ni80e" r c n"tr0cti n 2 all ceramic ! "t an- c re it/ /i#/ t 0#/ne"" ceramicmaterial"

^ Slip casting tec ni*ue

^ Copy milling tec ni*ue

^ T$o piece tec ni*ue

Heat press tec ni*ue

SLIP CASTIN+ TECHNI E7

• descri#ed #y 4em and 4node in .


52/55

Seminar -3

• sed only in $ide root canals $it out a crucial reduction of t e circumferentialdentin structure)

C2P MILLIN+ RECHNI E7

t e glass"infiltrated alumina ceramic% In"Ceram% and its fa#rication process a&e #eenadapted to t e Celay copy"milling met od /Mi'rona0% as an alternati&e to t e slip"casting tec ni*ue) T e Celay system in&ol&es a rnanually guided copy"milling

process in $ ic a predesigned resin pattern is surface traced and copied in ceramic)T e ceramic su#structures are prefa#ricated #lan's made of presintcrcd aluminumo(ide ceramic /Celay Alumina lan's% Kita 5a nfa#ri'0% In"Ceram ceramicrestorations made $it t e Celay met od present a .9Q ig er fle(ural strengt/a#out =99 iKlPa0 t an do con&entional In"Ceram restorations)

T is met od can #e used for inlay% onlay% &eneer%and cro$n"and"#ridge frame$or'fa#rication%as $ell as for copy"milled In"Ceram posts and cores)

T 2"PIECE TECHNI E7

ecause t e fracture strengt of In"Ceram posts and cores is less t an t at of metal posts and cores% In" Ceram posts and cores a&e only #een recommended

for $ide root canals)_ T e cases of regular root canals /smaller t an IS2 ..90% In"Ceram ceramic does not seem to pro&ide a sufficient strengt B for t at reason% until presently% an all"ceramic post and core $as not recommended for suc eases) Aftert e recent de&elopment of 8irconia ceramic posts% it #ecame possi#le to com#ine

#ot materials) !or a 1"piece post"and" core construction a post made of yttriumo(ide"partially sta#ili8ed 8irconia /ER"Cerapost% rasseler0 is used in con@unction $itan all"ceramic core made of alumina or alumina"magnesia]"` ceramics% fa#ricatedeit er #y t e copy"milling or t e slip"casing tec ni*ue) T e 8irconia ceramic posts are

commercially a&aila#le in t ree IS2 si8es /9=9% 9


53/55

Seminar -3

is eat" pressed o&er a prefa#ricated 8irconium dio(ide post /Cosmo Post% I&oclar0%and t erefore #ot materials are fused into a solid post"and"core restoration) .:

OTHER A((LICATION OF CERAMICS

Ceramic" in Me-ical A!!licati n"

Ceramics are employed in a $ide range in t e medical specialty suc as repair andreplacement of uman ips% 'nees% and ot er #ody parts %diseased eart &al&es) T eapplications are #ased on t e fact t at $ en used as implants or e&en as coatings to

metal replacements% ceramic materials can stimulate #one gro$t % promote tissueformation and pro&ide protection from t e immune system)

Moreo&er% modern ceramic materials play an important role in gadgets used formedical diagnosis including #ot ultrasonic and F"ray computed tomograp y /CT0systems) Transducers utili8ing lead 8irconate titanate /P5T0 #ased pie8oelectric ceramicsare t e eart of ultrasonic systems) T ese transducers generate t e ultrasonic acoustic$a&es and detect t e reflected signals to form t e image)

)a-#et" 2 r Dental A!!licati n" )

Karious recently introduced diagnostic and $or'ing tools of $ ic ceramics play anintegral part include7

Radio Kisio +rap y /RK+0 Pulp tester Ape( locators .st generation " resistance #ased) 1 nd generation " impedance #ased 3rd generation " fre*uency #ased)

"ie3o Ceramics

Pie8oelectricity can #e defined as pressure electricity $ ic is a property of certainclasses of crystalline materials including natural crystals of uart8% Roc elle salt andTourmaline plus manufactured ceramics suc as arium Titanate and Lead 5irconateTitanates /P5T0) en mec anical pressure is applied to one of t ese materials% t ecrystalline structure produces a &oltage proportional to t e pressure) Con&ersely% $ en anelectric field is applied% t e structure c anges s ape producing dimensional c anges in t ematerial) T e pie8oelectric materials use polycrystalline ceramics instead of natural

pie8oelectric crystals) T ey are more &ersatile $it p ysical% c emical and pie8oelectric

c aracteristics a#le to #e tailored to specific applications) T e ard% dense ceramics can #e

53


54/55

Seminar -3

manufactured in almost any gi&en s ape or si8e% $ ic are c emically inert and immune tomoisture and ot er atmosp eric conditions)

,i ceramic"

ioceramics are a group of ceramics% $ ic are #iologically acti&e materials ric incalcium and p osp ate) Hydro(yapatite and tricalcium p osp ate are similar incomposition to #one and teet and can #e used for augmentation of al&eolar ridges andfilling #ony defects) T ey are manufactured and are a&aila#le in #loc'% granular andin@ecta#le forms) T ese #ioacti&e materials are pac'ed in t e re*uired site pro&iding ascaffold for ne$ #one gro$t and are 2sseo"inducti&e in nature) T e &arious forms of

#ioceramics are Single crystals /Sapp ire0% Polycrystalline /Hydro(yapatite0 +lass/ ioacti&e glass0 +lass ceramics /Cera&ital0 Composites /Stainless steel reinforcedioglass0

T$!e" 2 ,i ceramic"

T ere are a#out four types of #ioceramics7

INERT7 Attac ed #y compact morp ological fi(ation) e)g% Alumina% Car#on

P2R2 S7 Attac ed #y &ascularisation t roug pores) e)g% Porous Alumina)

S R!ACE ACTIKE7 Directly attac #y c emical #onding $it #one)e)g% ioglass%Hydro(yapatite

RES2R A LE Designed to #e slo$ly replaced #y #one)e)g% Tricalcium P osp ate ;

CONCLUSION:

T ere as #een a re&olution in t e pro&ision of ceramics for dental restorations in t e last.= years% suc t at no$ all"ceramic restorations can #e used #ot anteriorly and

posteriorly)T ere is no dou#t t at ne$ materials and processing routes $ill continue to #ede&eloped and t at ceramics $ill play a gro$ing role in t e pro&ision of aest eticrestorations) T erefore need for dental practitioners to #e a$are of t e rapidly c angingeld of dental ceramics to ensure t at t e correct c oice is made for eac patient)

REFERNCES

54


55/55

Seminar -3

.) C u S% A mad I) Historical perspecti&es of synt etic ceramics and traditional!eldspat ic porcelain)Pract Proced Aest et Dent 199=B .:/

126536010 Dental Ceramics

Documents

Transcript of 126536010 Dental Ceramics