Luting Agents-raina (2)

8/10/2019 Luting Agents-raina (2)

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INTRODUCTION

The term cement has been applied to powder / liquid materials which are mixed to a paste

consistency.

The word lutin is de!ined as the use o! a moldable substance to seal "oints and cement

two substances toether.

#arious cements are used !or lutin !or example $inc phosphate% $inc silicophosphate%

$inc polycarboxylate% lass ionomer% and $inc oxide euenol and resin cements.

The clinical success o! !ixed prosthesis is hea&ily dependant on the cementation process.

'or a restoration to accomplish its purpose% it must stay in place on the tooth. No cements

that are compatible with li&in tooth structure and the bioloic en&ironment o! the oral

ca&ity possess adequate adhesi&e properties to hold a restoration in place solely throuh

adhesion.

(lthouh the establishment o! optimal resistance and retention !orms in the tooth

preparation are o! primary importance% a dental cement must be used as a barrier aainst

microbial lea)ae% sealin the inter!ace between the tooth and restoration and holdin

them toether throuh some !orm o! sur!ace attachment.


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*RINCI*+,- O' C,,NT(TION

Dental treatments necessitate attachment o! indirect restorations and appliances to

the teeth by means o! a cement. These include metal% resin% metalresin% metal ceramic%

and ceramic restorations% pro&isional or interim restorations0 laminate &eneers !or anterior

teeth0 orthodontic appliances% and pins and posts used !or retention o! restorations. The

word lutin is o!ten used to describe the use o! a moldable substance to seal a space or to

cement two components toether0.

The properties o! &arious cements di!!er !rom each other. 1ence% the choice cement is

mandated to a lare deree by the !unctional and bioloic demands o! the particular

clinical situation. I! optimal per!ormance is to be attained% the physical and bioloic

properties% and the handlin characteristic% such as the wor)in and settin times and ease

o! remo&in excess materials% must be considered in selectin a cement !or a speci!ic

tas).

C1(R(CT,RI-TIC- O' (2UT,NT 3 *RO-T1,-I- INT,R'(C,.

4hen two relati&ely !lat sur!aces are brouht into contact% analoous to a !ixed

prosthesis bein placed on a prepared tooth% a space exists between the substrates on a

microscopic scale.

Typical prepared sur!aces on a microscopic scale are rouh% that is% there are

pea)s and &alleys. 4hen two sur!aces are placed aainst each other% there are only point

contacts alon the pea)s. The areas that are not in contact then become open space. The

space created is substantial in terms o! oral !luid !low and bacterial in&asion. One o! the

main purposes o! a cement is to !ill this space completely. One can seal the space by

placin a so!t material% such as an elastomer% between the two sur!aces that can con!orm

under pressure to the 5rouhness6.

The current approach is to use the technoloy o! adhesi&es. (dhesi&e bondin

in&ol&es the placement o! a third material% o!ten called a cement that !lows within the

rouh sur!ace and sets to a solid !orm within a !ew minutes. The solid matter not only

seals the space but also retains the prosthesis. aterials used !or this application are

classi!ied as Type I cements. I! the third material is not !luid enouh or is incompatible


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with the sur!aces% &oids can de&elop around deep% narrow &alleys and undermine the

e!!ecti&eness o! the cement.

2ONDIN7 ,C1(NI-

Non adhesive luting

Oriinally the lutin aent ser&ed primarily to !ill the ap and pre&ent entrance o! !luids.

8inc phosphate !or example exhibits no adhesion on the molecular le&el. It holds the

restoration in place by enain small irreularities on the sur!ace o! both tooth and the

restoration. The nearly parallel opposin walls o! a correctly prepared tooth ma)e it

impossible to remo&e the restoration without shearin or crushin the minute pro"ections

o! cement extendin into recesses in the sur!aces.

Micromechanical bonding

Resin cements ha&e tensile strenths in the rane o! 9: ;: *a% which is approximately

!i&e times that o! $inc phosphate cement. 4hen used on pitted sur!aces% they can pro&ide

e!!ecti&e micromechanical bondin. The tensile strenths o! such bonds can sometimes

exceed the cohesi&e strenth o! enamel. This allows the use o! less extensi&e tooth

preparation !or restorations such as ceramic &eneers and resin bonded !ixed partial

dentures.

The deep irreularities necessary !or micromechanical bondin can be produced on

enamel sur!aces by etchin with phosphoric acid solution or el% on ceramics by etchin

with hydro!luoric acid and on metals by electrolytic etchin% chemical etchin%

sandblastin or by incorporatin salt crystals into preliminary resin pattern.

Molecular Adhesion

olecular (dhesion in&ol&es physical !orces


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+imited success has been achie&ed in attempts to de&elop resin cements and couplin

aents that will exhibit stron% durable molecular adhesion to tooth structure% base metals

and ceramics. Noble metal alloys are not suited !or direct molecular bondin. 1owe&er% a

thin layer o! silane can be bonded to a old alloy with special equipment ul$er% Ir&ine or Rocatec% ,-*,*remier= to ser&e as a couplin aent by bondin

chemically to resin cements. ,qually e!!ecti&e is a layer o! tin electroplated onto old

alloy.

2y applyin a silane coupler to rouhened porcelain% shear bond strenths in excess o!

the cohesi&e strenth o! the porcelain ha&e been achie&ed. 1owe&er such bonds tend to

become wea)er a!ter thermo cyclin in water. (t this time% molecular adhesion should be

loo)ed upon only as a way to enhance mechanical and micromechanical retention and

reduce micro lea)ae% rather than as an independent bondin mechanism.


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DI-+OD7,,NT O' *RO-T1,-I-

'ixed prostheses can debond because o! bioloic or physical reasons or a

combination o! the two. Recurrent caries results !rom a bioloic oriin. Disinteration o!

the cements can result !rom !racture or erosion o! the cement. 'or brittle prostheses% such

as lassceramic crowns% !racture o! the prosthesis also occurs because o! physical

!actors% includin intraoral !orces% !laws within the crown sur!aces% and &oids within the

cement layer.

In the oral en&ironment cementation aents are immersed in an aqueous solution. In this

en&ironment the cement layer near the marin can dissol&e and erode lea&in a space.

This space can be susceptible to plaque accumulation and recurrent caries0 there!ore% the

marin should be protected with a coatin


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sur!aces or bond enhancin intermediate layers may be used to reduce the potential o!

separation at the inter!ace and maximi$e the e!!ect o! the inherent strenth on the

retention.

4hen a mechanical undercut is the mechanism o! retention% the !ailure o!ten

occurs alon the inter!aces. I! chemical bondin is in&ol&ed% the !ailure o!ten occurs

cohesi&ely throuh the cement itsel!. The prosthesis becomes loose only when the cement

!ractures or dissol&es.

ID,(+ *RO*,RTI,- O' +UTIN7 C,,NT

Described byMcLean and Wilson

@. +ow &iscosity and !ilm thic)ness

A. +on wor)in time with rapid set at mouth temperature

9. 7ood resistance to aqueous or acid attac)

;. 1ih compressi&e and tensile strenth

B. Resistance to plastic de!ormation

. (dhesion to tooth structure and restoration

. Cariostatic

E. 2ioloically compatible with pulp

F. Translucency

@:. Radio opacity


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C1OIC, O' +UTIN7 (7,NT

(n ideal lutin aent is one which has a lon wor)in time% adheres well to both

tooth structure and cast alloys% pro&ides a ood seal% is non toxic to pulp% has adequate

strenth properties% is compressible into thin layers% has a low &iscosity and solubility and

exhibits ood wor)in and settin characteristics. In addition any excess can be easily

remo&ed. Un!ortunately% no such product exists.

Zinc phosphate cement

Is probably still the lutin aent o! choice. Ca&ity &arnish can be used to protect

aainst pulp irritation !rom phosphoric acid and appears to ha&e little e!!ect on the

amount o! retention o! the cemented restoration.

Zinc polycarboxylate cement

This aent is recommended on retenti&e preparation when minimal pulp irritation

is important.

Glass ionomer cement

This has become a popular cement !or lutin cast restoration. It has ood wor)in

properties and because o! its !luoride content% it may pre&ent recurrent caries.

Resin modified glass ionomer cement

Currently amon the most popular lutin aents% Resin modi!ied lass ionomer

cements ha&e low solubility% adhesion and low micro lea)ae. The popularity it

mainly due to percei&ed bene!it o! reduced post cementation sensiti&ity.

Adhesive resin

+onterm e&aluations o! these materials are not yet a&ailable% so they cannot be

recommended !or routine use. +aboratory testin yields hih retention strenth &alues%

but there is concern that stresses caused by polymeri$ation shrin)ae% mani!ied in thin

!ilms% leads to marinal lea)ae. (dhesi&e resin may be indicated when a castin has

become displaced throuh lac) o! retention.


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8INC *1O-*1(T, C,,NT

8inc phosphate cement is the oldest o! the cementation aents and thus has the lonest

trac) record. It ser&es as a standard by which newer systems can be compared. It is atraditional crown and bride cement used !or the alloy restorations. It is supplied as a

powder and liquid% both o! which are care!ully compounded to react with one another

durin mixin to de&elop a mass o! cement possessin desirable physical properties.

CO*O-ITION

Poder

The principal inredient o! the $inc phosphate cement is $inc oxide. anesium oxide%

silicon dioxide% bismuth trioxide% and other minor inredients are used in some products

to alter the wor)in characteristics and !inal properties o! the mixed cement.

8inc oxide


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The powder particle si$e in!luences the settin rate. 7enerally the smaller the particle

si$e% the !aster the set o! the cement.

Li!uid

(ddin aluminum and sometimes $inc% or their compounds% to a solution o!

orthophosphoric acid% produces $inc phosphate cement liquids. (lthouh the oriinal acid

solution contains about EBG phosphoric acid and is a syrupy !luid% the resultin cement

liquid usually contains about one third water

19*O;

19*O;


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amorphous matrix o! $inc aluminophosphate. The set $inc phosphate cement is

amorphous and is extremely porous.

The sur!ace o! al)aline powder is dissol&ed by the acid liquid% resultin in an exothermic

reaction.

(NI*U+(TION

The manner in which the reaction between $inc phosphate cement powder and liquid is

permitted to occur determines to a lare extent the wor)in characteristics and properties

o! the cement mass. Incorporate the proper amount o! powder into the liquid slowly on a

cool slab


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IJIN7 -+(2

( properly cooled thic) lass slab will dissipate the heat o! the reaction. The mixin slab

temperature should be low enouh to e!!ecti&ely cool the cement mass but must not be

below the dew point unless the !ro$en slab technique is used. ( temperature o! @EH to A;H

C is indicated when room humidity permits. The moisture condensation on a slab cooled

below dew point contaminates the mix% dilutin the liquid and shortenin the settin time.

The ability o! the mixin slab to be cooled and yet be !ree o! moisture reatly in!luences

proper control o! the reaction rate o! $inc phosphate cement.

IJIN7 *ROC,DUR,

2y incorporatin small portions o! the powder into the liquid% minimal heat is liberated

and easily dissipated. The heat o! the reaction is most e!!ecti&ely dissipated when the

cement is mixed o&er a lare area o! the cooled slab. Use a relati&ely lon narrow bladed

stainless steel spatula to spread the cement across this lare area to control the

temperature o! the mass and its settin time.

Durin neutrali$ation o! the liquid by the powder% the temperature o! the mixin site is

in&ersely proportional to the time consumed in mixin. Thus a lare &olume o! the

powder is carried to the liquid all at once rather than spatulated o&er a lare area o! the

slab !or a su!!icient time% the temperature at the site o! the reaction becomes hiher.

This temperature rise speeds the reaction and hinders control o&er the consistency.

Durin the middle o! the mixin period% larer amounts o! powder may be incorporated

to !urther saturate the liquid with the newly !ormin complex $inc phosphates. The

quantity o! the unreacted acid is less at this time because o! the prior neutrali$ation

ained !rom initially addin small increments o! powder. The amount o! heat liberated

will li)ewise be less% and it can be dissipated adequately by the cooled slab.

'inally smaller increments o! powder are aain incorporated% so the desired ultimate

consistency o! the cement is not exceeded.

Thus the mixin procedure beins and ends with small increments% !irst to achie&e slow

neutrali$ation o! the liquid with the attendant control o! the reaction and last to ain a

critical consistency.


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Dependin on the product : to F: seconds o! mixin appears adequate to accomplish a

proper $inc phosphate cementin mass.

CONT(CT 4IT1 OI-TUR,

The area near the cement must be )ept dry while the powder and liquid is mixed% durin

insertion into the mouth and durin hardenin. I! the cement is allowed to harden in the

presence o! sali&a some o! the phosphoric acid is lea)ed out and the sur!ace o! the cement

will be dull and easily dissol&ed by oral !luids.

(!ter the cement sets it should not be allowed to dry. Dryin o! the cement results in

shrin)ae and cra$in o! the sur!ace. ( coatin o! &arnish should minimi$e dehydration

as well as pre&ent premature contact with oral !luids.

4OR>IN7 TI, (ND -,TTIN7 TI,

4or)in time is the time measured !rom the start o! the mixin durin which the

&iscosity


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No attempt is made to pre&ent moisture !rom condensin on the slab when it is brouht to

room temperature. ( mix o! cement is made on the cold slab by addin the powder until

the correct consistency is reached. The amount o! powder incorporated with the !ro$en

slab method is B:G to BG more than with the normal procedures. The compressi&e

strenth and tensile strenth prepared by the !ro$en slab method are not sini!icantly

di!!erent !rom those prepared !or normal mixes% howe&er% because incorporation o!

condensed moisture into the mix in the !ro$en slab method counteracts the hiher powder

liquid ratio. This method has been ad&ocated !or cementation o! brides with multiple

pins.

,C1(NIC(+ INT,R+OC>IN7

4hene&er an inlay is seated in a prepared ca&ity the sur!aces o! both the inlay and the

tooth ha&e sliht rouhness and serrations into which the cement is !orced. 'ilm

thic)ness is a !actor !or retention. Thinner the cement better is the cementin action.

8inc phosphate cements are irritatin to the pulp. (lthouh the p1 o! the cement

approaches neutral at A; hours. Thinner mixes are more acidic and remain so !or a loner

period o! time than the standard mixes.

2er)% 1. -tanely said that thin mix 8inc phosphate cements ha&e more pulp response

than thic) mix because 8inc phosphate cements is pushed into dentinal tubules and it

destroys the odontoblast riht in place. The application o! a ca&ity &arnish to a cut tooth

structure can act as a barrier to the penetration o! the acid.

( recent animal study in&ol&in cementation o! crowns reported pulp response to none

when a ca&ity &arnish was applied to the teeth prior to cementation o! crowns. 4ith

respect to the e!!ect o! retention% 'etton showed a coat o! &arnish to ha&e no in!luence in

crown retention.

olta L* said that ca&ity &arnish has been shown to reduce the retention o! cemented pins

and decrease tensile bond between two opposed dentinal sur!ace when 8inc phosphate

cement is used !or lutin.


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C1(R(CT,RI-TIC- *RO*,RTI,-

Physical and biologic properties

Two physical properties o! the cement that are rele&ant to the retention o! the !ixed

prostheses are the mechanical properties and the solubilityMs. The prosthesis can et

disloded i! the underlyin cement is stressed beyond its strenth. 1ih solubility can

induce loss o! the cement needed !or the retention and may create plaque retention sites.

8inc phosphate cement when properly manipulated exhibits a compressi&e strenth o!

@:;*a and a diametral tensile strenth o! B.B *a.

8inc phosphate cement has a modulus o! elasticity o! approximately @9 7*a. Thus it is

quite sti!! and should be resistant to elastic de!ormation e&en when it is employed !or

cementation o! restorations that are sub"ected to hih masticatory stress.

( reduction in the powder liquid ratio o! the mix produces a mar)edly wea)er cement.

( loss or ain in the water content o! the liquid reduces the compressi&e and tensile

strenths o! the cement.

Retention

4hene&er a castin is seated in the prepared tooth% the sur!aces o! both the castin and

the tooth structure ha&e sliht rouhness and irreularities into which the plastic cement

is !orced. -uch extensions many times act as undercuts in pro&idin retention o! the inlay.

The thic)ness o! the !ilm between the castin and the tooth is also a !actor in the

retention. The thinner the !ilm% the better is the cementin action.

"olubility and disintegration

The premature contact o! the incompletely set cement with water results in dissolution

and leachin o! that sur!ace. *roloned contact e&en o! wellhardened cement% with

moisture demonstrates that some erosion and extraction o! soluble material does occur

!rom the cement.

,&en the !illin cement mixes show considerable loss o! material in the mouth o&er a

period o! time% indicatin that $inc phosphate can be rearded only as a temporary !illin

material. 4ear abrasion and attac) o! !ood decomposition products accelerate the

disinteration o! $inc phosphate cements. 7reater resistance to disinteration is achie&ed


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by increasin the powder liquid ratio. ( thic)er mix o! cement exhibits less solubility

than a thinner mix.

#imensional stability

8inc phosphate cement exhibits shrin)ae on hardenin. The normal dimensional chane

when properly mixed cement is brouht into contact with water a!ter it has set is that o!

sliht initial expansion% apparently !rom water absorption. This expansion is then

!ollowed by sliht shrin)ae on the order o! :.:;G to :.:G in days.

$onsistency and film thic%ness

Two arbitrary consistencies o! the cement are used based on their use.

Inlay seatin or lutin and cement base or !illin. ( third consistency which lies midway

between inlay seatin and the cement base% is band seatin consistency used !or retention

o! orthodontic bands.

The inlay seatin consistency is used to retain alloy restorations. (lthouh the

unhardened $inc phosphate cement is somewhat tenacious% the retainin action in its

hardened state is one o! mechanical interloc)in between the sur!ace irreularities o! the

tooth and the restoration.

The !ilm thic)ness o! the $inc phosphate cement reatly determines the adaptation o! the

castin to the tooth and also determines the strenth o! the retention bond.

The maximum !ilm thic)ness is AB m. the hea&ier the consistency0 the reater the !ilm

thic)ness and the less complete the seatin o! the restoration.

The ultimate !ilm thic)ness that a wellmixed% nonranular cement attains depends !irst

on the particle si$e o! the powder and second on the concentration o! the liquid.

The !ilm thic)ness also &aries with the amount o! !orce and the manner in which this

!orce is applied to a castin durin cementation.

(n increased amount o! powder incorporated into the liquid will increase the consistency

o! the cement mass.

The operator must !requently test each mass as the end o! mixin time approaches. The

!inal consistency will be !luid% yet will strin up !rom the slab on the spatula about A9cm

as the spatula is li!ted away !rom the mass.


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( hea&y putty li)e consistency o! $inc phosphate cement is used as a thermal and

chemical insulatin barrier o&er thin dentin and a hih strenth base.

&iscosity

The consistency o! cements can be quanti!ied by measurin &iscosity. ( small but

sini!icant increase in &iscosity is seen at hiher temperatures. ( rapid increase in

&iscosity demonstrates that restorations should be cemented promptly a!ter completion o!

the mixin to ta)e ad&antae o! the lower &iscosity o! the cement. Delays in cementation

can result in considerably thic) !ilm and insu!!icient seatin o! the restoration.

Acidity

Durin the !ormation o! $inc phosphate cement% the union o! $inc oxide powder with

phosphoric acid liquid is accompanied by a chane in p1. In the early staes the p1

increases rapidly% with a standard mix reachin the p1 o! ;.A within 9 minutes a!ter

mixin has started. (t the end o! one hour this &alue increases to about and is nearly

neutral at ;E hours.

In&estiations ha&e shown that the initial acidity o! $inc phosphate cement at the time o!

placement into the tooth may excite pulpal response% especially where only a thin layer o!

dentin exists% between cement and pulp.

'hermal and electrical conductivity

One o! the primary uses o! $inc phosphate cement is an insulatin base under metallic

restorations.


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(**+IC(TION-

8inc phosphate cement is used most commonly !or lutin permanent metal restorations

and as abase.

Other applications include cementation o! orthodontic bands and the use o! cement as a

pro&isional restoration.

(D#(NT(7,-

@. (dequate strenth to maintain the restoration

A. Relati&ely ood manu!acturer properties

9. ixed easily and that they set sharply to a relati&ely stron mass !rom a !luid

consistency.

DI-(D#(NT(7,-

@. Irritatin e!!ect on the pulp

A. +ac) o! anticarioenic properties

9. +ac) o! adhesion to the tooth

;. #ulnerability to acid attac)

B. 2rittleness

. -olubility in acid !luids.

R,(CTION O' *U+* TO C,,NT

The phosphoric acid in 8inc phosphate cement can be the cause o! the pulpal reaction.

The closer it approaches the pulp% the reater is the intensity o! the response. (lso the

ratio o! powder to liquid is important consideration. ( thic) mix o! 8inc phosphate

cement used as a base will enerate a moderate locali$ed response% whereas a thin mix

used to cement on a crown that is placed under reat pressure by patients bitin on a

tonue blade can cause a &ery se&ere reaction.


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8INC -I+ICO*1O-*1(T, C,,NT

They are also called as 8inc silicate% -ilicate $inc cement.

8inc silicophosphate cement is a hybrid resultin !rom the combination o! $inc phosphate

cement and silicate powders.

T*,- O' 8INC -I+ICO*1O-*1(T, C,,NT-

(ccordin to (D( no 3AE


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(D#(NT(7,-

@. 8inc silicophosphate cements ha&e a better strenth and touhness than $inc

phosphate cements

A. -hows considerable !luoride release hence anticarioenic

9. Translucent

;. Under clinical conditions lower solubility and better bondin

B. 2est suited to cement o! ortho bars and restoration on non&ital teeth.

DI-(D#(NT(7,-

@. +ess satis!actory mixin

A. 1iher !ilm thic)ness

9. 7reater pulpal irritation

TR(D, N(,-

'lourathin and +ucent < type I=


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8INC *O+C(R2OJ+(T, C,,NT

In the quest !or an adhesi&e cement that can bond stronly to the tooth structure% 8inc

polycarboxylate cement was the !irst cement system that de&eloped an adhesi&e bond to

tooth structure in @F:.

CO*O-ITION

8inc polycarboxylate cement or $inc polyacrylate cements are supplied as a powder and

liquid or as a powder that is mixed with water.

The cement powder is essentially $inc oxide and manesium oxide that ha&e been

sintered and round to reduce the reacti&ity o! $inc oxide. -tannic acid may be

substituted !or manesium oxide. Other oxides such as bismuth and aluminum can be

added. The powder may also contain small quantities o! stannous !luoride% which modi!y

settin time and enhance manipulati&e properties. It is an important additi&e because it

increases strenth. 1owe&er% the !luoride released !rom this cement is only a !raction. The

cement powder that is mixed with water contains @B G to @EG polyacrylic acid coated on

the oxide particles.

The liquid is a water solution o! polyacrylic acid. ost commercial liquids are supplied

as 9AG to ;AG solution o! polyacrylic acid ha&in molecular weiht o! AB%::: to B:%:::.

The manu!actures control the &iscosity o! the cement liquid by &aryin the molecular

weiht o! the polymer or by ad"ustin the p1 by addin sodium hydroxide. Itaconic and

tartaric may be present to stabili$e the liquid% which can el on extended storae.

-,TTIN7 R,(CTION

The settin reaction o! this cement in&ol&es particle sur!ace dissolution by acid that

releases $inc% manesium% and tin ions% which bind to the polymer chain &ia the carboxyl

roups. These ions react with carboxyl roups o! ad"acent polyacid chains so that a cross

lin)ed salt is !ormed as the cement sets. The hardened cement consists o! an amorphous

el matrix in which unreacted particles are dispersed. The microstructure resembles that

o! $inc phosphate cement in appearance.

4ater settable &ersions o! this cement are a&ailable. The polyacid is a !ree$edried

powder that is then mixed with the cement powder. The liquid is water or a wea) solution


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o! Na1A*O;. 1owe&er the settin reaction is the same whether the polyacid is !ree$e

dried and subsequently mixed with water or i! the con&entional aqueous solution o!

polyacid is used as the liquid.

(NI*U+(TION

Mixing

The cement liquids are quite &iscous. The &iscosity is a !unction o! the molecular weiht

and the concentration o! the polyacrylic acid thereby &aries. 7enerally the powder liquid

ratio is @.B parts o! powder to @ part o! liquid by weiht. The consistency o! the mixes is

creamy compared with that o! $inc phosphate cements. The mixes cement is

pseudoplastic that is the &iscosity decreases as the shear rate increases% or in other terms%

the !low increases as spatulation increases or as !orce is placed on the material. Thecorrect consistency is !ound in a mix that is &iscous but that will !low bac) under its own

weiht when drawn up with a spatula.

The cement liquid should be mixed on a sur!ace that does not absorb liquid. ( lass slab

a!!ords the ad&antae o&er paper pads supplied by the manu!acturers because once it is

cooled it maintains the temperature loner. The cool slab and powder pro&ides !or loner

wor)in time% but under no circumstances should the liquid be cooled in a re!rierator.

ix polyacrylate cements within 9: to : seconds% with hal! to all o! the powder

incorporated at once to pro&ide the maximum lenth o! wor)in time A.B to minutes.

4or)in time can be extended to @:@B minutes by usin a cool slab chilled to ;KC.

The liquid should not be dispensed be!ore the time when the mix is to be made. It loses

water to the atmosphere rapidly and this results in mar)ed increase in &iscosity.

Use the mixed cement only as lon as it appears lossy on the sur!ace. Once the sur!ace

becomes dull% the cement de&elops strininess and the !ilm thic)ness becomes too reat

to seat a castin completely.

I! ood bondin to tooth structure is to be achie&ed% the cement must be placed on the

tooth sur!ace be!ore it loses its lossy appearance. The lossy appearance indicates a

su!!icient number o! !ree carboxylic acid roups on the sur!ace o! the mixture that are

&ital !or bondin to tooth structure.


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"urface penetration and retention

Despite the adhesion o! the cement to tooth structure% polycarboxylate cements are not

superior to $inc phosphate cement in the retention o! cast noble metal restorations.

( comparable !orce is required to remo&e old inlays cemented either with $inc

phosphate cement or with polycarboxylate cement. ,xamination o! !ractured sur!aces

shows that !ailure usually occurs at the cement 3tooth inter!ace with $inc phosphate

cement.

In the case o! polycarboxylate cements% the !ailure occurs usually at the cement metal

inter!ace.

The cement does not bond to the metal in the chemically contaminated condition. Thus it

is essential that this contaminated sur!ace on the castin be remo&ed to impro&e

wettability and the mechanical bond at the cement metal inter!ace. The sur!ace can be

care!ully abraded with a small stone% or it can be sandblasted with hihpressure air and

alumina abrasi&es.

2ecause this type o! cement a!!ords an opportunity to obtain adhesion to tooth structure% a

clean ca&ity sur!ace is necessary to ensure intimate contact and interaction between

cement and the tooth. ( recommended procedure is to apply a @:G polyacrylic acid

solution !or @: to @B seconds !ollowed by rinsin with water.

Removal of excess cement

Durin settin the polycarboxylate cement passes throuh a rubbery stae that ma)es the

remo&al o! the excess cement quite di!!icult. The excess cement that has extruded beyond

the marins o! the castin should not be remo&ed while the cement is in this stae%

because some o! the cement may be pulled out !rom beneath the marins lea&in a &oid.

The excess should be remo&ed when the cement becomes hard. The outer sur!ace o! the

prosthesis should be coated with a separatin medium li)e petroleum "elly% to pre&ent

excess !rom adherin.

(nother approach is to start remo&in excess cement as soon as seatin is completed.


23/68

*RO*,RTI,-

&iscosity

The initial &iscosity o! $inc polycarboxylate cement is hiher than $inc phosphate

cements and a delay o! A minutes in cementation re&erses the situation.

(ilm thic%ness

4hen polycarboxylate cements are mixed they appear to be much &iscous than $inc

phosphate cement. -ince $inc polycarboxylate cement is pseudoplastic cement it

underoes thinnin at an increase shear rate. Clinically% this means that the action o!

spatulation and seatin with a &ibratory action will reduce the &iscosity and yield a !ilm

thic)ness o! AB m or less.

Wor%ing time and setting time

The wor)in time !or polycarboxylate cement is much shorter than phosphate cement that

is A.B minutes. +owerin the temperature o! the reaction can increase the wor)in time

that may be necessary !or !ixed brides. Un!ortunately% the temperature o! the cool slab

can cause the polyacrylic acid to thic)en. The increased &iscosity ma)es the mixin

procedure more di!!icult. It has been suested that only the powder should be

re!rierated be!ore mixin.

The settin time ranes !rom to F minutes.

Mechanical properties

The compressi&e strenth o! polycarboxylate cement is BB pa.

The diametrical tensile strenth is slihtly hiher than that o! $inc phosphate cement.

Its modulus o! elasticity is less than hal!.

2rown stated that an increse in the compressi&e and tensile strenth o! polycarboxylate

cement can be obtained with the addtion o! stainless steel powder or !ibers .

8inc polycarboxylate cement is not as brittle as $inc phosphate cement.

Thus it is more di!!icult to remo&e the excess a!ter the cement has set.


24/68

"olubility

The solubility o! the cement in water is low% but when it is exposed to oranic acids with

a p1 o! ;.B or less% the solubility mar)edly increases.

(lso a reduction in the powder liquid ratio results in sini!icantly hiher solubility and

disinteration rate in the oral ca&ity.

)ond strength

(n interestin !eature o! polyacrylate cement is itMs bondin to enamel and dentin% which

is attributed to the ability o! the carboxylate roups in the polymer molecule to chelate to

calcium. The bond strenth to enamel has been reported to be !rom 9.; to @9 *a and to

that o! dentin is A.@ *a. Optimum bondin requires clean tooth sur!ace. -and blastin

or electrolytic etchin o! the old alloy sur!ace is necessary to achie&e optimum bondin.

#imensional stability

The $inc polyacrylate cement shows a linear contraction when settin at 9 C. the amount

o! contraction &aries !rom @ G !or a wet specimen at @ day to G !or a dry specimen at

@; days. These contractions are more pronounced than those obser&ed !or $inc phosphate

cements and start earlier.

Acidity

8inc polyacrylate cements are slihtly more acidic than $inc phosphate cements when

!irst mixed but the acid is only wea)ly dissociated% and penetration o! the hihly

molecular weiht polymer molecules toward pulpal tissue is minimal.

ortiner noted that !ilm thic)ness is thic)er than $inc phosphate cement.

(ccordin to 4ilson and *addon the cement remains much less brittle and is touher

than silicate% $inc phosphate and lass ionomer cement.

(belson said that the retention o! !ull crown was similar to $inc phosphate.


25/68

(**+IC(TION-

8inc polyacrylate cements are used primarily !or lutin permanent alloy restorations and

as bases. Theses cements ha&e also been used in orthodontics !or cementation o! bands.

(D#(NT(7,-

@. 2iocompatibility with the pulp is excellent. *ostoperati&e sensiti&ity is neliible

when used as a lutin aent

A. (dhesion to tooth and alloy

9. ,asy manipulation.

DI-(D#(NT(7,-

@. Need !or accurate proportionin required !or optimal properties

A. 7reater &iscoelasticity

9. -horter wor)in time

;. +ow compressi&e strenth

B. ore critical manipulation.

TR(D, N(,-

Dertelon


26/68

7+(-- IONO,R C,,NT

7lass ionomer is the eneric name o! a roup o! materials that use silicate lass powder

and an aqueous solution o! polyacrylic acid. The material acquires its name !rom its

!ormulation o! a lass powder and an ionomeric acid that contains carboxyl roups. It is

also re!erred to as polyal)eonate cement.

Oriinally% the cement was desined !or the esthetic restoration o! anterior teeth and it

was recommended !or use in restorin teeth with class III and # ca&ity preparations. (lso

because the cement produces a truly adhesi&e bond to tooth structure.

(**+IC(TION-

The use o! 7IC has broadened to encompass !ormulations as lutin aents% liners%

restorati&e materials% core buildups and pit and !issure sealants.

T*,- O' 7+(-- IONO,R C,,NT

There are three types based on their !ormulations and their potential uses

Type I

+utin applications

*owder liquid ratio is enerally @.B ? @

7rain si$e @B m or less

1ih early resistance to water contamination

Radiopaque !or easy detection o! excess

+imited extension o! wor)in time thru chillin lass slab.

Type II

Restorati&e material

*owder liquid ratio 9?@

ust protect !or A; hours !or best results

Reduced !luoride content to impro&e translucency


27/68

Type III

+iner and base.

*owder liquid ratio &aries accordin to use

+inin requires @.B?@ !or easy

2ase requires 9?@ or reater !or strenth

+iht acti&ated &arieties a&ailable

Type I#

etal modi!ied lass ionomer cement

iracle mix

Cermet cement

+iht curable &ersions o! 7IC are also a&ailable.


28/68

'luoride is an essential constituent o! lass ionomer cement. It lowers the temperature o!

!usion% increases the strenth and impro&es the wor)in characteristics o! the cement

paste.

The liquid !or 7IC was aqueous solutions o! polyacrylic acid in a concentration o! about

B: G. The liquid was quite &iscous and tended to el o&er time. The acid is !orm o! a

copolymer with itaconic% maleic% or tricaboxylic acid. Theses acids tend to increase the

reacti&ity o! the liquid% decreases the &iscosity% and reduce the tendency !or elation.

The copolymeric acids used in modern lass ionomer liquids are more irreularly

arraned than in the homopolymer o! acrylic acid. This con!iuration reduces hydroen

bondin between acid molecules and thus reduces the deree o! ellin. Tartaric acid

present in the liquid impro&es the handlin characteristics and increases the wor)in time

howe&er it shortens the settin time.

One o! the lass ionomer !ormulations consist o! !ree$e dried acid powder and lass

powder in one bottle and water or water with tartaric acid in another bottle as the liquid

component. 4hen the powders are mixed with water% the acid dissol&es to reconstitute

the liquid acid. The chemical reaction then proceeds in the same manner as that

demonstrated by the powder liquid system. This is usually done to extend the wor)in

time. These cements ha&e a loner wor)in time with a shorter settin time. They are

re!erred to as water settable 7ICMs or as anhydrous 7ICMs.

-immons and urray et al say that compressi&e strenth has been !ound to be

sini!icantly increased with the addition o! sil&er alloy powder.

c+ean showed that a simple matrix o! metal powder and alumino silicate lass ionomer

powder !ailed to !orm a su!!icient bond at metal/ polyacrylate inter!ace. The lass

ionomer cement is capable o! establishin a bond with the dentin substrate be!ore

de&elopment start% but the composite start only a!ter stress is started

C1,I-TR O' -,TTIN7

7lass ionomer cement is an acid base reaction cement as de!ined by 4ilson and 4yant.

4hen the powder and liquid are mixed to !orm a paste% the sur!ace o! the lass particles

is attac)ed by the acid. Calcium% aluminium% sodium and !luorine ions are leached into


29/68

the aqueous medium. The polyacrylic acid chains are crosslin)ed by the calcium ions

and !orm a solid mass. 4ithin the next A; hours a new phase !orms in which aluminum

ions become bound within the cement mix. This leads to more riid cement. -odium and

!luorine ions do not participate in the cross lin)in o! the cement. -ome o! the sodium

ions may replace the hydroen ions o! carboxylic roup% where as the rest combines with

!luorine ions% !ormin sodium !luoride uni!ormly dispersed within the set cement. Durin

the maturin process% the crosslin)ed phase is also hydrated by the same water used as

the medium. The unreacted portion o! lass particles are sheathed by silica el that

de&elops durin remo&al o! the cations !rom the sur!ace o! the particles. Thus% the set

cement consists o! an alomeration o! unreacted powder particles surrounded by a silica

el in an amorphous matrix o! hydrated calcium and aluminum polysalts.

RO+, O' 4(T,R IN T1, -,TTIN7 *ROC,--

4ater is a most important constituent o! the cement liquid. It ser&es as the reaction

medium initially% and then it slowly hydrates the cross lin)ed matrix% thereby increasin

the material strenth. Durin the initial reaction period% this water can readily be remo&ed

by desiccation and is called loosely bound water. (s the settin continues% the same water

hydrates the matrix and cannot be remo&ed by desiccation and is then called tihtly

bound water. This hydration is critical in yieldin a stable el structure and buildin the

strenth o! the cement.

I! !reshly mixed cements are )ept !rom the ambient air% the loosely held water will slowly

become tihtly bound water o&er time. This phenomenon results in cement that is

stroner and less susceptible to moisture.

I! the same mixes are exposed to ambient air without any co&erin% the sur!aces will

cra$e and crac) as a result o! desiccation. (ny contamination by water that occurs at this

stae can cause dissolution o! the matrix !ormin cations and anions to the surroundin

areas. This process results in wea) and more soluble cement. (lthouh the dissolution

susceptibility tends to decrease o&er time% the minimum time at which the daner o!

crac)in !rom the exposure to air no loner exists has not been established. The ionomer

cement must be protected aainst water chanes in the structure durin placement and !or

a !ew wee)s a!ter placement i! possible.


30/68

RO+, O' '+UORID,

7lass ionomer cements are bioacti&e. They !orm permanent adhesi&e bonds to dentin and

enamel% hence pre&entin the de&elopment o! secondary caries.

They also release !luoride o&er a proloned period and so can arrest the proress o!

caries.

O! all dental cements they are the most resistant to erosion in the acidic stanation

reions o! the mouth.

(NI*U+(TION-

To achie&e a lon lastin restoration se&eral conditions need to be satis!ied li)e

appropriate ca&ity sur!ace preparation to achie&e the bondin% proper mixin to obtain a

wor)able mixture.

-UR'(C, *R,*(R(TION

Clean sur!aces are essential to promote adhesion. ( pumice wash can be used to remo&e

the smear layer that is produced durin ca&ity preparation. On the other hand oranic

acids such as polyacrylic acids o! &arious concentrations can remo&e the smear layer but

still lea&e the collaenous tubule plu in place. These plus inhibit the penetration o! the

cement constituents and a!!ect the hydrodynamic !luid pressure within dentin.

One wor)able method is to apply a @: G o! polyacrylic acid solution to the sur!ace !or @:

to @B seconds% !ollowed by a 9: second water rinse.tBhe smear layer will be remo&ed but

the tubules remain plued. This procedure o! remo&in the smear layer is called

conditionin.

The purpose o! pumice debridement is to remo&e the !luoride rich layer sur!ace that may

compromise the sur!ace conditionin process.

(!ter conditionin and rinsin o! the preparation% the sur!ace should be dried but it

should not be unduly desiccated. It must remain clean because any !urther contamination

by sali&a or blood impairs bondin o! the cement.


31/68

*R,*(R(TION O' T1, (T,RI(+

7lass ionomer cements mixed with carboxylic acid liquids ha&e a powder liquid ratio o!

@.9? @ or @.9B? @% but it is the rane o! @.AB to @.B o! powder per @ ml o! liquid.

The powder and liquid are dispensed on a paper or a lass slab. ( cool dry lass slab may

be used to slow down the reaction and extend the wor)in time .the slab should not be

used i! the temperature is below dew point% that is% at temperatures that enhance moisture

condensation on the lass slab that can alter the acid water balance needed !or a proper

reaction. 2y waitin !or a !ew minutes% the temperature o! the slab will rise su!!iciently

until water &apor no loner condenses on its sur!ace.

The powder and liquid should not be dispensed onto the slab until "ust be!ore the mixin

procedure is to be started. *roloned exposure to the o!!ice atmosphere alters the precise

acid water ratio o! the liquid. The powder is di&ided into two equal portions. The !irst

portion is incorporated into the liquid with a sti!! spatula be!ore the second portion is

added. The mixin time is 9: to : seconds. (t this time the mix should ha&e a lossy

sur!ace. The shiny sur!ace indicates the presence o! polyacid that has not participated in

the settin reaction. The residual acid ensures adhesi&e bondin to the tooth. I! the

mixin process is proloned% a dull sur!ace de&elops% and adhesion will not be achie&ed.

,ncapsulated products are typically mixed !or @: seconds in a mechanical mixer and

dispensed directly onto the tooth and restoration.

The cement must be used immediately because the wor)in time a!ter mixin is about A

minutes at room temperature. (n extension o! the wor)in time to F minutes can be

achie&ed by mixin on a cool slab%


32/68

*RO*,RTI,-

(ilm thic%ness

The lass ionomer cement is capable o! !ormin !ilms o! ABm or less.

Wor%ing time and setting time

The wor)in time ranes !rom about 9 to B minutes the water settable cements tend to

ha&e somewhat loner wor)in time.

The settin time is usually between B to F minutes. The water added cements ha&e a more

rapid initial set than those that use the polyacid liquid.

2oth wor)in time and settin time can be determined by indentation tests.

The oscillatin rheometer o! 4ilson i&es more in!ormation and is a better measure o!

wor)in time. Its dynamic nature is closer to the clinical than is static indentation test.

"trength

The A;hour compressi&e strenth o! 7lass ionomer cements ranes !rom F: to A9: *a

and is reater than that o! $inc phosphate cement.

Tensile strenth is similar to those o! $inc phosphate cement.

7lass ionomer cements show brittle !ailure in diametral compression tests.

The elastic modulus o! lass ionomer cements is less than that o! $inc phosphate but

more than that o! $inc polycarboxylate cement. The riidity o! lass ionomer cements is

impro&ed by the lass particles and the iononic nature o! the bondin between polymer

chains.

)ond strength

7lass ionomer cements bond to dentin with &alues o! tensile bond strenth reported

between @ and 9 *a. The bond strenth o! lass ionomer cements to dentin is somewhat

lower than that o! $inc polyacrylate cement% perhaps because o! the sensiti&ity o! lass

ionomer cements to moisture durin settin. The bond strenth has been impro&ed by

treatin the dentin with an acidic conditioner !ollowed by an application o! a dilute

aqueous solution o! !erric chloride.


33/68

7lass ionomer cements bond well to enamel% stainless steel% and tin oxide plated platinum

and old alloy.

"olubility

The solubility in water !or the !irst A; hours is hih. It is important that the cement should

be protected !rom any moisture contamination durin this period. (!ter the cement has

been allowed to mature !ully% it becomes one o! the most resistant o! the nonresin

cements to solubility and disinteration in the oral ca&ity.

)iologic properties

The lass ionomer cements bond adhesi&ely to tooth structure and they inhibit in!iltration

o! oral !luids at the cement tooth inter!ace. This particular property plus the less irritatin

nature o! the acid should reduce the !requency o! postoperati&e sensiti&ity.

There are se&eral !actors contributin to the irritant nature. One is the p1 and the lenth

o! time that this acidity persists.

(nother !actor may be the &iscosity. The p1 relate to the thinner mixes used !or

cementation and do not apply to the hiher powder liquid ratio.

7lass ionomer lutin cements may cause proloned hypersensiti&ity% &aryin !orm mild

to se&ere% micro lea)ae has been suested as an explanation% but a recent study showed

no increase in bacterial counts B days a!ter cementation o! crowns with a lass ionomer

cements. These cements may be bacteriostatic or bactericidal because o! !luoride release.

7ra&er says that postcemented micro lea)ae is the cause o! tooth sensiti&ity.

-mith D.C. states the cause o! post cemented sensiti&ity as bacterial in&asion% hydraulic

pressure% acidity in the early settin stae and wash out o! thin mix.

Taywn stated that the hiher the powder liquid ratio the reater is the thermal di!!usi&ity.

(D1,-ION

7lass ionomer has the property o! permanent adhesion to untreated enamel and

dentin under moist conditions o! the mouth. It reacts with the smear layer on cut dentin


34/68

2ondin is o! a chemical rather than a micro mechanical nature. There!ore% no

acid etchin or sur!ace rouhenin procedures is deprecated. (bout E:G o! maximum

bond strenth is de&eloped in @B minutes but strenth slowly increases !or se&eral days

a!ter that.

,C1(NI- O' (D1,-ION TO ,N(,+ (ND D,NTIN,

Chemically% tooth material consists o! apatite% which ma)es up FEG o! enamel

and :G o! dentin by weiht and collaen% which is !ound in dentin alone. The bond o!

lass ionomer cements is better to enamel than to dentine% because bondin to apatite is

the principal mode o! adhesion.

2eech proposed that the interaction between apatite and polyacrylic acid produced

polyacrylate ions% which then !ormed stron ionic bonds with the sur!ace calcium ions o!

apatite in enamel and dentine.

4ilson suested that initially% when the cement paste is applied to tooth material

and is !luid% wettin and initial adhesion is by hydroen bondin pro&ided by !ree

carboxyl roups present in the !resh paste. (s the cement aes% the hydroen bonds are

proressi&ely replaced by ionic bonds. The cations comin either !rom the cement or the

hydroxyapatite. *olymeric polar chains o! polyacid are essential !or the achie&ement o!

adhesion. Their role is thouht to be one o! bridin the inter!ace between the cement

and the substrate.

4ilson et al postulated that durin absorption polyacrylate entered the molecular sur!ace

o! hydroxyapatite% displacin and replacin the sur!ace phosphate. (lso calcium ions are

displaced !rom hydoxypatite alon with phosphate durin this ionic exchane. There!ore%

an intermediate layer o! calcium and aluminium phosphates and polyacrylates would

!orm at the inter!ace between the cement and apatite.

Chain lenth is also an important !actor in adhesion. The polymer chains capable

o! bridin aps between the cement body and substrate.

2ondin to enamel% which is mostly apatite is due to ionic and polar !orces and

bondin to dentine is only to the apatite constituent o! the dentine. There!ore% the

adhesion o! lass ionomer to dentine is wea)er.


35/68

Collaen contains both amino and carboxylic acid roups% so adhesion could be

due to hydroen bondin or cationic brides.

1owe&er% recent absorption studies show that polyacrylic acid and polyacrylate are not

absorbed on collaen.

Cements based on polyacrylic acid appear to bond more stronly than those based

on copolymers o! acrylic acid with itaconic or maleic acids. ,&idence is only

accumulatin that bond strenth to tooth substances depends on the nature o! the polyacid

used.

I! it were pro&ed% then the molecular con!iuration o! the polyacid would become

an important !actor in controllin adhesion.

I*RO#IN7 (D1,-ION

4hen the cement tooth bonds !ractures% it is by cohesi&e !ailure within the cement

rather than adhesi&e !ailure at the inter!ace. There!ore% the strenth o! the bond is limited

by the cohesi&e strenth o! the cement used. The smear layer is considered to be

bene!icial. 1owe&er% sali&ary contamination o! a !reshly prepared dentine sur!ace

reduces bond strenth% but whether this was because o! its water contact or contamination

o! the dentin sur!ace is uncertain.

-UR'(C, CONDITIONIN7

( number o! research wor)ers ha&e souht to impro&e adhesion o! lass ionomer

cements. One way that is common to nearly all adhesi&e technoloies is by pretreatment

o! the sur!ace.

clean and 4ilson !irst used the term sur!ace conditionin !or this treatment in order to

di!!erentiate it !rom acid etchin. -ur!ace conditionin is needed in order to eliminate the

wide &ariation !ound in the structures o! the tooth sur!aces !ollowin cuttin. Rouh

tooth sur!aces are contraindicated. In eneral% the smoother the sur!ace% the stroner is

the bond. 7ood inter!acial contact is important !or adhesion. -moothenin is necessary

to pre&ent air entrapment and to minimi$e sites where stress concentration could occur.


36/68

'+UORID, R,+,(-,

2oth enamel and cementum can absorb !luoride. 'luoride is incorporated within

the mineral structure as !luoridated hydroxy apatite. *lenti!ul !luoride is released in the

early li!e o! the restoration and it radually decreases o&er a period.

'luoride is released !or at least @E months. Thic)ly mixed cements released more

!luoride because they contain proportionately more lasses and there!ore more !luoride.

Not all the !luoride is a&ailable !or release. It is released as sodium !luoride and is

restricted by the sodium and the calcium content o! the lass and not by the total !luoride

content o! the lass. -odium !luoride is released pre!erentially !rom the matrix rather

than the !iller. The rate o! release is proportional to the in&erse o! the square root o! time.

(luminum ions are also released% temporarily and ceases once the cement has !ully

hardened. (luminum ions absorbed by enamel con!er acid resistance upon the tooth.

(CTION O' '+UORID, IN *R,#,NTION O' C(RI,-

The anticaries e!!ect can be due to the upta)e o! !luoride ions by enamel apatite at

hydroxyl sites% and hih !luoride le&el at enamel sur!aces increases resistance to plaque

acids. -ur!ace enery o! apatite is decreased% there!ore% the dental plaque does not adhere

to tooth enamel sur!aces.

R,(CTION O' C,,NT ON *U+*

-e&eral reasons ha&e been postulated as to why 7lass ionomer cement does not

ha&e the same damain e!!ect on the pulp than 8inc phosphate cement.

'irst bein the polycarboxylic acid used is much wea)er than phosphoric acid.

-econd% the acid is a polymer% means that it will ha&e a much hiher molecular weiht

and this will limit di!!usion alon the dentinal tubules towards the pulp.

Thirdly% there is a stron electrostatic attraction between hydroen ions and neati&ely

chared polymer chain and dissociation will less readily ta)e place than with simple

anions.

(**+IC(TION-

7lass ionomer cements are primarily used !or permanent cement% as a base% and as a class

# !illin material.


37/68

The cement has been e&aluated as a pit and !issure sealant and an endodontic sealer.

7lass ionomer cements are bein used clinically !or cementation o! orthodontic bands

because o! their ability to minimi$e decalci!ication o! enamel by means o! !luoride

release.


38/68

12RID IONO,R C,,NT-

-el! cured and liht cured ionomers


39/68

1,( is )nown as a contact alleren there!ore the use protecti&e lo&es and a no touch

technique are recommended.

*RO*,RTI,-

The compressi&e and tensile strenths o! hybrid ionomer cement are similar to lass

ionomer cements.

The !racture touhness is hiher than that o! other water based cements but lower than

composite cements.

The bond strenth to moist dentin ranes !rom @: to @; *a and is much hiher than that

o! most water based cements.

1ybrid ionomer cement ha&e &ery low solubility when tested by lactic acid erosion.

4ater sorption is hiher than resin cements.

'luoride release is similar to lass ionomer cements. The early p1 is about 9.B and

radually rises.

(**+IC(TION-

-el! cured hybrid ionomer cement are indicated !or permanent cementation o! porcelain

!use to metal crowns% brides% metal inlays% on lays% and crowns% post cementation and

lutin o! orthodontic appliances.

(dditional uses include adhesi&e liners !or amalam% bases% pro&isional restorations and

cementation o! speci!ic ceramic restorations.


40/68

8INC OJID, ,U7,NO+ C,,NT

This material has been used to a wide rane applications in dentistry includin its use as

an impression material !or edentulous arches% a surical dressin% a bite reistration paste%

a temporary !illin material% root canal !illin% a cementin medium% and as a temporary

relinin material !or dentures.

8O, cement is one o! the least irritatin o! all the dental materials and pro&ides an

excellent seal aainst lea)ae.

T*,-

(ccordin to (D( speci!ication 9:

Type I 8O, cement 3temporary cementation

Type II 8O, cements 3permanent cementation o! restorations or appliances !abricated

outside o! the mouth

Type III 8O, cements 3temporary restoration and thermal insulatin bases

Type I# 8O, cements 3 ca&ity liner

CO*O-ITION

These materials are dispensed in two separate pastes. One tube contains $inc oxide and

!ixed &eetable or mineral oil acts as a plastici$er and aids in o!! settin the action o! the

euenol as an irritant. The $inc oxide should be !inely di&ided and it should contain only

a sliht amount o! water. Oil o! clo&es% which contains : G to EBG euenol% is

sometimes used in pre!erence to euenol because it reduces the burnin sensation

experienced by patients when it contacts the so!t tissues.

The addition o! rosin to the paste in the second tube apparently !acilitates the speed o! the

reaction% and it yields a smoother% more homoenous product. Canada balsam and *eru

balsam are o!ten used to increase !low and impro&e mixin properties. I! the mixed paste

is too thin or it lac)s body be!ore it sets% a !iller


41/68

'ube no * +base,

8inc oxide E

'ixed &eetable or mineral oil @9

'ube no - +catalyst,

Oil o! clo&es or euenol @A

7um or polymeri$ed resin B:

'iller


42/68

(NI*U+(TION

The mixin o! the two pastes is enerally accomplished on an oil imper&ious paper%

althouh a lassmixin slab can be used. The proper proportion o! the two pastes is

enerally achie&ed by squee$in two strips o! the paste o! the same lenth% one !rom each

tube% onto the mixin slab. ( !lexible stainless steel spatula is satis!actory !or the mixin.

The two strips are combined with the !irst sweep o! the spatula% and the mixin is

continued !or approximately @ minute until a uni!orm color is obser&ed.

Cements intended !or !inal cementation o! restorations carry manu!acturers directions and

measurin de&ices that are important to use% because o! the decepti&e !low qualities o!

these cements% addin powder until the operator !eels the mix is o! suitable consistency

!or cementin a restoration will lead to a cement de!icient in powder and a lowered

strenth in the set cement.

*RO*,RTI,-

"etting time

The initial settin time may &ary between 9 to minutes.

The !inal settin time is the time at which the material is hard enouh to resist penetration

under a load. It can occur within @: minutes !or type I pastes and @B minutes !or type II.

The actual settin time is shorter when the settin occurs in the mouth.

(ilm thic%ness

The !ilm thic)ness should not be more than AB m !or cements used !or permanent

cementation and not more than ;: m !or cements used !or temporary cementation.

$ompressive strength

( maximum &alue o! 9B*a is required !or cements intended !or temporary cementation.

( minimum o! 9B *a is required !or cements intended !or permanent cementation.

The strenth o! the cement !or temporary cementation is selected in relation to the

retenti&e characteristics o! the restoration and the expected problems o! remo&in the

restoration when the time arri&es.


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#isintegration

( maximum &alue o! A.BG is acceptable !or pro&isional cementin materials but a &alue

o! @.B G is required !or the other cements.

*RO#I-ION(+ C,,NT(TION

On many occasions% cementin a restoration pro&isionally is ad&ised not that the

patient and dentist can assess its appearance and !unction o&er a loner time than a sinle

&isit. 1owe&er% this trial cementation should be manaed cautiously. On one hand%

remo&in the restoration !or de!initi&e cementation may be di!!icult% e&en when

temporary 8nO, is used.

To a&oid this problem% the pro&isional cement can be mixed with little petroleum or

silicone rease and applied only to marins o! restoration to seal them while allowin

subsequent remo&al without di!!iculty.

On the other hand% a pro&isionally cemented restoration may come loose durin

!unction.

I! a sinle unit is displaced% it can be embarrassin or uncom!ortable !or the patient.

I! one abutment o! a '*D becomes loose% the consequences can be more se&ere.

I! the pat does not promptly return !or recementation caries may de&elop &ery rapidly.

*ro&isional cementation should not be underta)en unless the patient is i&en clear

instructions about the ob"ecti&e o! the procedures% the intended duration o! the trial

cementation and the importance o! returnin i! an abutment loosens.

T,*OR(R C,,NT(TION

Unmodi!ied 8O, cements are used as a lutin material !or pro&isional restorations in

crown and bride prosthodontics.

Unmodi!ied cements are a&ailable in the compressi&e strenths o! @.;*a to A@*a.

-tudies pro&ed that lutin cements with a compressi&e strenth o! @B to A; *a was the

most appropriate cement based on retention0 taste0 ease o! remo&al0 ease o! cleanin.


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NON,U7,NO+ *(-T,

One o! the chie! disad&antaes o! the 8O, pastes is the possible stinin or burnin

sensation caused by euenol when it contacts so!t tissues. 'urthermore the 8O, reaction

is ne&er completed% with the result that the !ree euenol may leach out. -ome patients

!ind the taste o! euenol extremely disareeable and in patients who wear a surical pac)

!or se&eral wee)s0 a chronic astric disturbance may result.

( material similar to 8O, reaction product can be !ormed by a saponi!ication reaction to

produce an insoluble soap% i! the $inc oxide is reacted with a carboxylic acid. The

reaction is

8nO ARCOO1S


45/68

R,-IN 2(-,D C,,NT

Resin lutin cements ha&e been in existence since the @FB:Ms. The early !ormulations

were lihtly !illed methyl methacrylate resins. 2ecause o! their hih polymeri$ation

shrin)ae% tendency !or pulpal irritation% penchant !or micro lea)ae and poor handlin

characteristics% these resins had only limited use.

1owe&er % with the de&elopment o! composite direct !illin resins with impro&ed

properties acceptance to acid etch and potential to bond to dentin% a &ariety o! resin

cements ha&e become a&ailable.

I-O ;:;F

Describes three classes o! composites !or polymer based !illin% restoration and lutin

materials

Class @ 3 sel! cured materials

Class A 3 liht cured materials

Class 9 3 dual cured materials

R,UIR,,NT- 2(-,D ON I-O ;:;F

Class @%A%9? maximum !ilm thic)ness B: m

Class @%9? minimumwor)in time : seconds

Class @%9? maximum settin time @: minutes

Class A? depth cure :.Bmm


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colloidal silica is that used in micro !illed resins. The resin matrix binds them toether

and bonds them to the tooth structure. 2ecause most o! a prepared tooth sur!ace is dentin%

monomers with !unctional roups that ha&e been used to induce bondin to dentin are

o!ten incorporated in these resin cements. They ha&e oranophosphates% hydroxyethyl

methacrylate


47/68

etched enamel on tooth preparations that would not be retenti&e enouh to succeed with

con&entional cements.

2IO+O7IC *RO*,RTI,-

Resin based cements% "ust li)e composite cements are irritatin to the pulp. Thus% pulp

protection &ia a calcium hydroxide or lass ionomer liner is important when one is

cementin an indirect restoration that in&ol&es bondin to dentin.

(NI*U+(TION

The chemically acti&ated &ersions o! theses cements are supplied as two component

systems a powder and a liquid or two pastes.

The peroxide initiator is contained in one component and the amine acti&ator is contained

in the other. The two components are combined by mixin on a treated paper pad !or A:

to 9: seconds. The time o! excess remo&al is critical. I! it is done while the cement is in a

rubbery state% the cement may be pulled !rom beneath the marin o! the restoration%

lea&in a &oid that increases the ris) o! plaque buildup and secondary caries.

Remo&al o! the excess cement is di!!icult i! it is delayed until the cement has

polymeri$ed. It is best to remo&e the excess cement immediately a!ter the restoration is

seated.

+iht cured cements are sinle component systems "ust as are the liht cured !illin

resins. They are widely used !or cementation o! porcelain and lass ceramic restorations

and !or direct bondin o! ceramic orthodontic brac)ets. The time o! exposure to the liht

that is needed !or polymeri$ation o! the resin cement is dependant on the liht transmitted

throuh the ceramic restoration and the layer o! polymeric cement. 1owe&er the time o!

exposure to the liht should ne&er be less than ;: seconds.

The dual cure cements are two component systems and require mixin that is similar to

that !or the chemically acti&ated systems. The chemical acti&ation is slow and pro&ides

extended wor)in time until the cement is exposed to the curin liht% at which point the

cement solidi!ies rapidly. It then continues to ain strenth o&er an extended period

because o! the chemically acti&ated polymeri$ation.


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DI-(D#(NT(7,-

,xcessi&e cement !ilm thic)ness

arinal lea)ae because o! settin shrin)ae

-e&ere pulpal reactions when applied to cut &ital dentin

Dentin bondin aents ha&e been reported to reduce pulpal response% presumably by

sealin the dentinal tubules and reducin micro lea)ae. (dhesi&e resin was !ound to

produce better marinal seal than $inc phosphate cement.

CO*O-IT, R,-IN --T,

Three types o! composite resin materials are a&ailable !or use in indirect techniques?

micro!illed resins% small particle composite resins and hybrid resins. (ll show excellent

wear resistance% but small particle composite resins and hybrid resins can be etched to

produce micromechanical retention. They can also be silanted to increase the bond

strenth !urther. One manu!acturer o! a rein!orced micro!illed resin inlay/ onlay system

pro&ides a special bondin aent to increase the bond strenth o! its material.

R,-IN 2OND,D 2RID7,-

Theses prosthesis are widely employed as alternati&es to metal ceramic brides.

In this procedure% the preparation o! the abutment teeth is minimal and is con!ined to

enamel o! the linual sur!ace and proximal sur!aces. The tissue sur!aces o! the abutments

are rouhened by electrochemical etchin or other means and the sur!aces o! the prepared

tooth enamel are acid etched to pro&ide mechanical retention areas !or the resin cements.

7+(-- C,R(IC R,-TOR(TION-

These restorations are o!ten translucent and require speci!ic shades o! cementation aent

to maximi$e their esthetic appearance.

Resin cements ha&e been the cementation aents o! choice recently !or all ceramic inlays%

crowns and brides because o! their ability to reduce !racture o! the ceramic structures.


49/68

To achie&e the best retention% the undersur!ace o! the lass ceramic restorations is usually

etched and a silane coatin is applied be!ore cementation.

R,-IN ,T(+ 2ONDIN7

2ondin composites to the metal !ramewor) o! a bride and denture acrylic to a partial

denture !ramewor) can be impro&ed by the use o! silica coatin. *resently there are three

methods o! applyin silica to either noble or base metal alloys.

One method applies pyroenic silica usin a propane !lame.

Other method s use heat in an o&en or ceramic blastin to coat the restoration or

appliance. 2ond strenths o! composites to silica coated (u*dCr2e alloys !rom @ to

AA *a. -ilica coatin o! noble alloys eliminates the need !or tinplatin these alloys to

impro&e adhesion o! composites. The bond strenth o! denture acrylics to NiCr2e

alloys rane !rom to A9 *a when alloy is treated with a silica coatin or primed with

adhesi&e resin cement. +iquid cements based on thiosul!ates ha&e recently become

a&ailable !or treatment o! alloys. Recently% metal primers based on thiophosphate

chemistry ha&e been introduced as a treatment !or resin metal bondin.


50/68

CO*O,R-

Compomer is the resin based cement indicated !or cementation o! cast alloy crowns and

brides% porcelain !used to metal crown and brides and old cast inlays and onlays.

Cementation o! all ceramic crowns% inlays onlays and &eneers The cement should not be

used as a core or !illin material.

Compomers are also )nown as poly acid modi!ied composites.

CO*O-ITION

The cement powder contains strontium aluminum !luorosilicate lass% sodium !luoride

and sel! and liht cured initiators. The liquid contains polymeri$able methacrylate /

carboxylic acid monomer% multi!unctional acrylate / phosphate monomer% diacrylate

monomer and water.

-,TTIN7 R,(CTION

-ettin is the result o! sel! and liht cured polymeri$ation. Once the cement comes into

contact oral !luids an acid base reaction may occur. The carboxylic acid roups

contribute to the adhesi&e capability o! the cement.

(NI*U+(TION

Dry the tooth to be cemented but do not desiccate. The powder liquid ratio is A scoops to

A drops. Tumble the powder be!ore dispensin. ix the powder and the liquid rapidly !or

9: seconds. *lace the mixed cement in the crown only and then seat the crown.

( el state is reached a!ter @ minute% at which time the excess cement is remo&ed with

!loss and a scaler. +iht cure the exposed marins to stabili$e the restoration. -ettin

occurs 9 minutes a!ter start o! mix. Once set% compomer cement is &ery hard.

*RO*,RTI,-

Compomer cement has hiher &alues o! retention% bond strenth% compressi&e strenth%

!lexural strenth and !racture touhness. The cement has low solubility and sustained

!luoride release.


51/68

C,,NT(TION *ROC,DUR,

The permanent cementation o! the restoration is the !inal clinical procedure that mar)s

the success o! our e!!orts.

Our interest is that the permanent cementation should be per!ormed without lon periods

o! temporary cementation. Otherwise the patient may be exposed to a series o! unpleasant

complications such as separation o! the teeth% di!!iculty in achie&in a satis!actory le&el

o! oral hyiene% problems in remo&al o! the restoration% and the possibility o! in!iltration

because the thic)ness o! the temporary cement is without doubt reater than the thic)ness

o! the permanent cement and is much less !luid.

In immediate cementations the conditions o! the healthy periodontium are ideal and

especially in conditions o! complete &isibility o! the entire preparation% cases in which the

pro&isional restoration has been constructed properly% the only practice we !ollow is one

o! isolatin the area% cleanin the preparation and protectin the prepared sur!ace o! &ital

teeth.

I-O+(TION

The per!ormance o! all lutin aents is deraded i! the material is contaminated with

water% blood% or sali&a. There!ore the restoration and the tooth must be care!ully cleaned

and dried a!ter the try in procedure% althouh excessi&e dryin o! the tooth must be

a&oided to pre&ent damae to the odontoblasts. The castin is best prepared by air

bradin the !ittin sur!ace with B:m alumina. This should be done care!ully to a&oid

abradin the polished sur!aces or marins. (lternati&e cleanin methods include steam

cleanin% ultrasonic and oranic sol&ents.

2e!ore initiation o! cement mixin% isolatin the area o! cementation and cleanin and

dryin the tooth is mandatory. 1owe&er the tooth should ne&er be excessi&ely desiccated.

O&er dryin the prepared tooth will lead to postoperati&e sensiti&ity.

-(+I#( CONTRO+

Dependin on the location o! the preparation in the dental arch% se&eral techniques can be

used to create the necessary dry !iled o! operation. In areas where only supraini&al

marins are present% moisture control with a rubber dam is probably the most appropriate


52/68

method. 1owe&er% in most instances a rubber dam cannot be used and absorbent cotton

rolls must be placed at the source o! the sali&a0 an e&acuator must be placed where the

sali&a pools. In the maxillary arch% placin a sinle cotton roll in the &estibule

immediately buccal to the preparation and a sali&a e&acuator in the opposin linual

sulcus is enerally su!!icient.

4hen wor)in on a maxillary second or third molar% multiple cotton rolls must be placed

immediately buccal to the preparation and slihtly anterior to bloc) o!! the parotid duct.

I! a maxillary roll does not stay in position but slips down% it can be retained with a !iner

or the mouth mirror.

(n alternati&e to multiple cotton rolls is placement o! one lon roll 5horseshoe !ashion6

in the maxillary and mandibular muccobuccal !olds.

The use o! moisture absorbent cards is another method !or controllin sali&a !low. These

cards are pressed paper wa!ers co&ered with a re!lecti&e !oil on one side. The paper side

is placed aainst the dried buccal tissue and adheres to it. In addition two cotton rolls

should be placed in the maxillary and mandibular &estibules to control sali&a and displace

the chee) laterally.

-&edopter and -pee"ector 3 !or isolation and e&acuation o! the mandibular teeth% the

metal sali&a e"ector with attached tonue de!lector is excellent. 2y addin !acial and

linual cotton rolls% excellent tonue control and isolation is pro&ided.


53/68

,xcessi&e !orces are not necessary to ma)e crowns seat durin the phase o! cementation.

I! the space !or the cement has been pro&ided by the use o! die spacer% it is not necessary

to exert a reat deal !orce% which can determine a permanent alteration o! the interity o!

the marinal !it. It should be )ept in mind that the cementation load should not exceed B

).

The technique used is )nown as the brush technique and consists o! the application o! a

small quantity o! cement on the incisal ede o! the preparation usin a brush !or the

application.


54/68

The interior o! the crown in the area o! the marins is painted with a small quantity o!

cement% and the crown is placed alon its path o! insertion.

The insertional technique is as !ollows? the crown is inserted slowly to about one hal! the

distances0 it is then withdrawn by a !ew millimeters and is reinserted to almost the !ull

extent o! its lenth. The process is then repeated. 4e use a sliht up and down mo&ement

alon this path to assist the layerin o! the cement. 4hen the operator no loner !eels any

resistance% the crown is pushed to the !inish line and thus to its !inal seatin. It is

necessary to a&oid rotational mo&ements to !ind the correct seatin position. This can be

damain i! porcelain marins are present.


55/68

Once the crown has been inserted the patient is pro&ided with an occlusal support and is

as)ed to close to maintain the position o! the crown durin the settin o! the cement.

In pro!essional practice we pre!er to cement one crown at a time% or at the most two

ad"acent crowns.

Once the cement has hardened we !ollow this procedure? a!ter immersion o! the *.>.

Thomas no. A waxin instrument in a silicone lubricant we enter the "unctional area and

remo&e the excess cement by !ollowin the anatomy o! that area. 4e pre!er to use this

instrument because it has a rounded tip and a cur&ature that are ideal !or !ollowin the

anatomic contour. 4e place it aainst the coronal sur!ace and insert it in the ini&al

sulcus in the "unctional area. 2y applyin liht pressure we !ollow the "unction and

remo&e the cement. The purpose o! this cement is this technique is to remo&e the cement

!ollowin the contour without causin scratches in the area o! crown marin. The same

procedure is repeated on the linual sur!ace and on the interproximal sur!aces% and

because o! the instrument cur&ature0 it results as bein e!!icient and easy to per!orm.


56/68

-ome cements li)e polycarboxylate or resin% tend to pull away !rom the marins i! excess

remo&al is per!ormed too early.

Dental !loss with a small )not in it can be used to remo&e any irritatin residual cement

interproximally and !rom the ini&al sulcus. The sulcus should contain no cement. (!ter

the excess has been remo&ed. The occlusion can be chec)ed once more with ylar shim

stoc).Cements ta)e at least A; hours to de&elop their !inal strenth. There!ore the patient

should be cautioned to chew care!ully !or a day or two.


57/68

*O-TC,,NT(TION

(queous 3 based cements continue to mature o&er time well a!ter they ha&e

passed the de!ined settin time. I! they are allowed to mature in an isolated en&ironment%

that is% !ree o! contamination !rom surroundin moisture and !ree !rom loss o! water

throuh e&aporation% the cements will acquire additional strenth and become more

resistant to dissolution. It is recommended that coats o! &arnish or a bondin aent

should be placed around the marin be!ore the patient is dischared.


58/68

+UTIN7 O' #,N,,R-

(ll ceramic restorations may be cemented with $inc phosphate% lass ionomer or dual

polymeri$in resin cement. The cement comes in !our shades care!ully rinsed under runnin water


59/68

liht !rom the labial


60/68

+UTIN7 O' C,R(IC R,-TOR(TION- 4IT1 R,-IN 2(-,D C,,NT-

The crown should be cleaned% etched and silaned. Remo&e any oranic debris with

ethanol or acetone% !ollowed by placin the restoration in an ultrasonic cleaner. 'urther

cleanin can be accomplished by applyin liquid phosphoric acid etchant. The crown is

silaned with a silane couplin aent. Dispense one drop o! silane primer and one drop o!

silane acti&ator into a dappen dish. -tir the liquid in the dish !or @: @B seconds with a

brush. (pply it to the internal sur!ace o! the crown0 a&oid application on the external

sur!ace o! the crown by co&erin the outside o! the crown with wax. Rinse the crown and

dry it with compressed air.

Clean the tooth preparation with a rubber cup and !lour o! pumice. Ten wash and air dry.

,tch the enamel !or 9: seconds. Rinse and air dry the tooth.

(pply bond adhesi&e o&er the entire preparation with a brush. Thin the bondin aent

with compressed air !or @B seconds. *olymeri$e the adhesi&e.

Dispense equal amount o! base !rom the syrine and catalyst !rom the tube. ix !or @:

A: seconds with a !lat ended plastic mixin stic). (pply a thin layer o! cement to the

internal sur!ace o! the crown. -eat the crown and remo&e the excess to a&oid ditchin the

cement at the marin.

(im the liht cure at the marinal areas !rom !acial% linual and occlusal directions !or ;:

: seconds.

(d"ust the bul)y marins and chec) !or premature contacts. *olish the crown usin

porcelain !inishin )it.


61/68

CONC+U-ION

+utin aents possess &aried% complex chemistries that a!!ect their physical properties%

lone&ity and suitability in clinical situations. It appears a sinle adhesi&e will not su!!ice

in modern day practice. To date% no adhesi&e can completely compensate !or the

shortcomins o! the preparation retention and resistance !orms or ill !ittin% low strenth

restorations. *rosthdontics must be aware o! the &irtues and shortcomins o! each cement

type and select them appropriately.


62/68

REVIEW OF LITERATURE

,dwin. # in @FB@ in his study on mechanism o! dental structure said that the dental

cements act as a bond by )eyin action. Rouhness o! inter!ace between the inlay and

the tooth area in&ol&ed


63/68

results showed that the retenti&e ability o! both cements increased with increasin sur!ace

rouhness. The increase in retention was reater !or bras than !or dentine.

Dorothy cComb


64/68

C.+. Da&idson erby


65/68

immersion in water decreased the width o! both $ones in all cements and mar)edly

lowered the loss o! the sur!ace o! reular lass ionomer cement than other.

4illiam 4. 2rac)et


66/68

REFERENCES

@. (ntony 1. +. T"an? ,!!ect o! &arious cementation methods on the retention o!

pre!abricated L.*.D. 3 @FE0 BE%90 9:F

A. 2utton 7.+. 3 -ur!ace preparation and bond strenth o! castin cement inter!ace.

L.*.D 3@FEB0 B90 @9;E.

9. Chun oonum? The e!!ect o! early water contact on 7. I. Cements. 3

uint. Int.@FFA0 A90 A:F.

;. .Dorothy cComb 3 Retention o! castins with 7.I. cements 3

L.*.D. @FEA0 ;E90 AEB.

B. Da&idson C.+. Destructi&e stress in lutin cements. 3

L. Dent Res? @FF@0 :B% EE:

. De -chepper ,.L. 3 'luoride release !rom 7.I. cements 3

uint? @FF@0 AA0 90 A@B

. ,dwin #. echanism o! dental structures. 3 L.*.D. @FB@%A% 9:@:

E. 7.1. Lohnson 3 ,&aluation and control o! post cementation pulpal sensiti&ity 3

L.(.D.(. @FF90 @A;0 @@0 9E;

F. 7udbrand Oilo 3 Clinical study o! two lutin cements used on students treated

patients 3L.*.D. @FE;0 BA;0 B@E

@:. 7.Oilo The in!luence o! sur!ace rouhness on the retenti&e ability o! two dentallutin cements. 3 L.Oral.Rehab0 @FE B


67/68

@. Richter 4.(. *redictability o! retenti&e &alues o! dental cements.

L.*.D. 0 @F: A; 39AFE

@E. 4illiam 4. 2rac)ett 3 *er!ormance o! 7.I. lutin cements o&er a period o! B yrs.

L.*.D. @FFA0 %@% BFA

@F. 4endi ( +e&ine 3(n e&aluation o! the thic)ness o! resin lutin

Luting Agents-raina (2)

Documents