Failures and Management

7/26/2019 Failures and Management

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FAILURES OF COMPOSITE RESTORATIONS AND THEIR

MANAGEMENT

Causes of failure of a restoration:

i. Aor!in" to #ilson $ Fu%%i

Failure

Ne& Disease Te'nial Failure

Caries & Tooth wear Fractured restoration

Periodontal disease Marginal breakdown

Pulpal problems Tooth fracture

Trauma Defective contours

Failure of retention

II. Aor!in" to (en!erson $ Ronin"

Failures of restorations can be characterized as

Secondar caries

Marginal deterioration

Tooth fractures

!oss of anatom

!oss of aesthetics

"estoration fractures

III. Aor!in" to Mount

Failure of tooth structure Failure of restorative material

Failure of enamel margin Failure of margins

Failure of dentin margin Fracture or collapse of material

#ulk loss of tooth structure Total loss of restoration

Split root

!oss of vitalit

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Composite resin placement is a ver techni%ue sensitive procedure and failure

to follow the protocol at an one step often produces compromised results The

potential areas of error have been enumerated below'

( C)S* S*!*CT+,-

Caries rate

,cclusal factors

. +S,!)T+,- ,F T/* ,P*")T+-0 S+T*

1 F)CT,"S "*!)T*D T, T,,T/

*namel %ualit

Dentin %ualit

)ccessibilit

2 F)CT,"S "*!)T*D T, C)3+T4 P"*P)")T+,-

Cavit depth

Cavit configuration

*5tension of cavit on cementum

"etention features

$ F)CT,"S "*!)T*D T, *TC/+-0

Tpe of etchant used

)pplication time

6ualit of the substrate

"insing procedures

Contamination

7 F)CT,"S "*!)T*D T, #,-D+-0

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Dr versus wet bonding

*vaporation of primer

Thickness of bonding agent

)pplication techni%ue

#ond strength of adhesive

Compatibilit of the adhesive with the resin

Contamination

8 F)CT,"S "*!)T*D T, M)T*"+)! )SP*CT ,F T/* "*S+-

Filler particle size

Tpe of composite selected

3iscosit of the material

Polmerization shrinkage

9ear of material

Depth of cure

: F)CT,"S "*!)T*D T, S/)D* S*!*CT+,-

Factors related to light

Factors related to ee

Factors related to shade guide

; F)CT,"S "*!)T*D T, T/* P!)C*M*-T ,F T/* "*S+-

9hether mi5ing is re%uired

+ncremental techni%ue or bulk placement

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Distance between the tip and the resin

Curing steps

(( F)CT,"S "*!)T*D T, C,-T,="+-0 )-D F+-+S/+-0 P",C*D="*S

(. F)CT,"S "*!)T*D T, P)T+*-T M)+-T*-)-C*

FAILURES IN COMPOSITE RESTORATIONS MA) MANIFEST

AS:

( Marginal fracture

. Discoloration

1 Secondar caries

2 Postoperative sensitivit

$ 9eak or missing pro5imal contact

7 +ncorrect shade

8 Poor retention

: 0ap formation

; 9ear

(mentioned manifestations are often coe5istent and interlinked These are

considered in detail subse%uentl

MARGINAL FRACTURE

Marginal integrit of composites is ver good under most circumstances

Clinical appearance is affected b the nature of the margin #utt ?oint margins

emphasize composite wear more than beveled margins #utt ?oint margins of well>

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bonded restorations wear more slowl and create a meniscus appearance against the

enamel /owever@ as beveled margins wear@ thinner edges of material are produced

that are more prone to fracture Microfracture of the enamel margins causes the

appearance of a white line or halo

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The following factors ma be responsible for such a phenomenon'

Traumatic contouring or finishing

)ll instruments should be used wet to contain the inevitable dust that can produce

an e5tremel bitter taste for the patient The wet finishing also avoids the frictional

heat that ma tend to pull up the margin Continuing to polish dr after the margin

has opened sweeps the composite dust under the margins producing the Awhite lineB

The Awhite lineB has also been proposed to result from rela5ation of the

polmerization shrinkage stresses caused b the aggressive finishing techni%ues

The initial cracking of a posterior composite resin is also thought to have been

caused b the contouring and finishing processes +nappropriate sized finishing

instruments probabl generate microcracks b the rapidl rotating blades of the

finishing instrument

+nade%uate etching and bonding of that area

/igh> intensit light> curing resulting in e5cessive polmerization stresses

Marginal ditching is a common finding in composite inlas and onlas #ecause

resin cements tend not to be heavil filled@ the wear more %uickl than the ad?acent

restorations or tooth structure This is particularl true if the marginal fit is poor

Potential solutions include'

Polmerization shrinkage coupled with techni%ue sensitivit can lead to a risk of an

open margin +ncremental techni%ue b adding 1>$ laers of material making sure

that the final laer is over the entire restoration is useful in combating

microfractures This procedure will also avoid staining of the region

"e> etching@ priming and bonding of the area

Conservative removal of the fault and re> restoring

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=sing atraumatic finishing techni%ues eg !ight intermittent pressure

=sing slow> start polmerization techni%ue

"ebonding E glazing

This is an advisable procedure that involves re> etching the enamel margins of a

polished composite restoration and placing a coat of unfilled or lightl filled resin

with subse%uent curing

) .< second re> polmerization of the restoration following final finish is reported

to provide a stronger and longer> lasting finish

*nsure good marginal fit of composite inlas and onlas to reduce the marginal gap

DISCOLORATION

Discoloration is a ma?or failure of a direct tooth colored restorative material +t

results from

Surface staining

Marginal staining due to microleakage

Changes in surface morpholog due to wear

Material deterioration over time

Diet and oral hgiene of patient

The %ualit of surface finish influences the esthetics and longevit of tooth>

colored restoratives The presence of irregularities on the surface of the materials ma

influence the appearance@ staining@ pla%ue retention@ secondar caries risk and

gingival irritation +n addition@ smoother restorations are also more easil maintained

)lthough restorations against a matri5 are not totall devoid of surface imperfections@

the represent the smoothest possible surface for most direct restorations ,ne

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disadvantage of microfilled composite@ as stated b Davidson and emp> Scholte@ is

the tendenc to undergo hgroscopic e5pansion which produces marginal

overhangsin the less motivated patient@ this ma lead to e5cessive staining and

recurrent caries when microfilled composites are used to restore Class $ cavities =se

of some form of magnification ma aid the restorative dentist in placing the desired

margins

SECONDAR) CARIES

Secondar caries is one of the leading causes of failure of the composite resin

restoration and also one of the ma?or reasons for replacement of the same Composite

resin material as such has no resistance at all to recurrent caries )s long as the

margins are well bonded and no marginal fractures occur@ resistance to secondar

caries should be good )lthough not well documented@ most secondar caries seems to

occur along pro5imal and cervical margins where enamel is thin@ less well oriented for

bonding@ difficult to access during restorative procedure@ and potentiall sub?ect to

fle5ural stresses as well ,nl rarel is secondar caries observed along margins on

occlusal surfaces or noncervical aspects of other surfaces

"ecurrent caries ma be due to'

Ino*+lete re*o,al of +ri*ar- aries> Failure to distinguish clinicall between

affected and infected dentin ma lead to some infected dentin remaining behind

ultimatel leading to recurrence of the lesion

Inorret +lae*ent te'niue> the incidence of caries is %uite variable@

depending largel on the degree of technical e5cellence during composite

placement Clinical research studies indicate that for well> controlled insertion

techni%ues the incidence of secondar caries after (< ears can be as low as 1G

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=nder these circumstances@ the primar reason for failure is poor esthetics or

e5cessive wear Cross> sectional studies of dental practices that did not conform to

recommended techni%ues indicate that caries levels as high as .$G to 1 intensit lights compared with halogen

lights ma result in higher microleakage values

Poor finis'in" an! +olis'in" te'niues

Material as+ets

The potential solutions to prevent the occurrence of secondar caries are'

Caries !etetor !-esma be used to ensure complete removal of the infected

dentin /owever@ the are not found to be totall reliable and are advised to be used

with caution

#rannstrom indicated that residual bacteria in a cavit preparation could multipl

from within the smear laer@ even in the presence of a good seal from the oral

cavit /e proposed the use of a,it- !isinfetants prior to placements of

restorations +n a stud the use of Concepsis and Tublicid "ed did not affect the

sealing abilit of Clearfil S* #ond and Prompt !> Pop

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POSTOPERATI/E SENSITI/IT)

) perple5ing problem faced b most restorative dentists is tooth sensitivit

after placement of Class ( and Class . resin restorations )ccording to Christensen@

the following factors should be considered when postoperative sensitivit occurs'

H-+ere*i +ul+ tissue> the pulp condition should be normal as far as can be

determined before starting restorative procedures@ especiall Class ( and Class .

restorations

Cra0e! teet'> sensitivit is often reported in teeth where cracks were detected in

the internal dentin surfaces

A1usi,e uttin" +roe!ures> aggressive cutting procedures and inade%uate water

lavage were found to increase the chances of postoperative sensitivit

C2 fator> the most commonl accepted theor for postoperative sensitivit with

resin restorations is polmerization shrinkage Polmerization shrinkage leads to

gap formation@ which allows bacterial penetration and fluid flow under the

restoration =sing bonded resin> modified glass ionomer cements or compomers to

fill undercuts or large defects in tooth preparation before placing restorative resin

helps to reduce the overall size of the restoration and reduce the damage

Contraction stresses resulting from polmerization shrinkage andE or e5pansion

from water sorption can cause fle5ure of the bonded cusps and produce pain

Ai! et'in"> )ccording to #rannstrom@ it is not the acid used while etching that is

harmful@ but the post> restoration bacterial invasion that results from inade%uatel

sealed margins that causes sensitivit =se of cavit disinfectants disinfectants

should be considered

H-!ration> the dentin should not be allowed to desiccate

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Pri*er +lae*ent> inade%uate primer placement ma cause postoperative

sensitivit due to inade%uate AwettingB

3on!in" a"ent> a nonuniform thickness ma again lead to an inade%uate hbrid

laer formation

Curin" li"'t intensit-> factors related to curing lights are discussed subse%uentl

Inre*ent si%e2 the incremental placement techni%ue has been largel

recommended to reduce the effect of polmerization contraction stress at the

bonding interface 9hen small increments are placed and light cured@ the C> factor

is reduced Some manufacturers of composite materials recentl introduced in the

market@ recommend bulk placements in increments of $mm thickness Pentron and

Caulk /owever@ studies have found lower hardness at the cervical surfaces when

compared to occlusal surfaces This ma be due to the fact that when light passes

through the material@ it is dispersed and the efficac of the polmerization in the

deepest laers is compromised Composition of the resin material ma also

influence the degree of polmerization in the deepest laers of a restoration> heav

microfilled composite was the most affected Darker shades also lead to lower

depths of penetration /owever@ studies have indicated that the opacit or

translucenc of the material ma be more important than the shade

Coeffiients of t'er*al e4+ansion2 composites have a coefficient of thermal

e5pansion .>7 times that of the tooth This means that the composite material

e5pands and contracts at a greater rate than does tooth structure in response to

changes in temperature@ such as when hot coffee or ice> cream is consumed This

mismatch contributes to loss of adhesion and increased microleakage leading to

postoperative sensitivit

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Ina!euate len"t' of ure> after curing each increment for 1 2< seconds as it is

placed@ additional curing of 2 7< seconds each on facial@ occlusal and lingual

surfaces is suggested to ensure optimal care

/oi!s on +eri+'er- of t'e restoration> this has been discussed separatel

A1usi,e finis'in" +roe!ures> resin should be slightl overfilled at the margins

before curing@ leaving onl a small amount of resin to finish !ight finishing touches

with sharp burs are preferred Some form of magnification ma aid the operator in

preventing mutilation of the margins

Olusal e,aluation> this is a prere%uisite before placement of a resin restoration

Posture2 after all the finishing and polishing has been completed@ another minute

of curing should be accomplished on occlusal surface to ensure that the resin has

cured well and to reduce the resin wear during service

#EA5 OR MISSING PRO6IMAL CONTACT

The causes of weak or missing pro5imal contacts in Class .@ Class 1 and Class 2

restorations are'

+nade%uatel contoured matri5 band

+nade%uate wedging@ both pre> operativel and during the composite insertion

Matri5 band movement during composite insertion@ or matri5 band not in

direct contact with the ad?acent pro5imal surface

) circumferential matri5 band used when restoring onl one contact

Tack composite pulling awa from matri5 contact area during insertion

Matri5 band too thick

The potential solutions for the management of cases of weak pro5imal contacts are'

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Proper contouring of the matri5 band

Matri5 band should be in contact with the ad?acent tooth

Firm pre> operative and insertion wedging techni%ue should be used

) matri5 sstem that placed the band onl around the pro5imal surface to be

restored should be used

Speciall designed@ triangular light tips that help to hold the light tip against

the ad?acent tooth while curing should be preferred

) hand instrument should hold the matri5 against the ad?acent tooth while

curing the incremental placements of the composite resin

Careful attention should be placed on the insertion techni%ue

INCORRECT SHADE

+ncorrect shade selection is a commonl occurring problem especiall for the

novice Color matching not onl depends on proper initial color match@ but also on

the relative changes that occur with time #oth the restoration and tooth structure are

known to change in color with age

+ncorrect shade selection could occur due to'

Ina++ro+riate olor li"'tin" &'ile seletin" t'e s'a!e> commonl used

fluorescent light tubes emit light with a green tint that can distort color perception

Seletion of t'e s'a!e &'en t'e toot' is !r-> temporaril dring the tooth

structure makes it appear whiter and lighter in color because of dehdration of the

enamel Presence of the rubber dam can also distort perception

S'a!e ta1 not *at'in" t'e atual o*+osite s'a!e> there ma be a marked

difference@ one noticeable to the ee@ between the color shades and the resin samples

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especiall for the incisal shades and deep dark colors Compounding the difficult

in shade selection are@ according to Makinson@ color changes that develop during

curing /e found that@ in general@ all colors become lighter@ with some becoming

more opa%ue and some transparent

Color auit- an! e-e fati"ue> staring at the tooth and shade tab for too long

causes colors to blend and results in a subse%uent loss of acuit

Color 'an"e &it' a"e> with time@ chemical changes in the matri5 polmer ma

cause the composite to appear more ellow This process is accelerated b e5posure

to =3 light@ o5idation@ and moisture )nterior restorative materials with high matri5

contents that are self> cured are more likel to undergo ellowing *ven if a

composite is relativel color stable@ tooth structure undergoes a change in its

appearance over time because of dentin darkening from aging )ged tooth appears

more opa%ue and darker ellow

Ina!euate +re+aration of t'e a,osurfae *ar"in2 an abrupt bevel results in

less surface area for a well> bonded margin and ma lead to marginal leakage

Marginal leakage leads to accumulation of subsurface interfacial staining that is

difficult or impossible to remove and creates a marked boundar for the restoration

appearance

#ron" s'a!e seletion> in case of Class $ lesions the shadow created b the lip

line tends to emphasize the gra shades Therefore@ gra and translucent shades are

to be avoided when restoring Class $ defects and more opa%ue shades should be

selected for better blending

3lea'in" of teet'> bleaching of teeth complicates the process of tring to

establish and maintain good color match of an anterior restoration to ad?acent tooth

structure

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Potential solutions to obtain an esthetic result are'

-atural light is preferred for shade selection Color> corrected fluorescent tubes that

appro5imate natural dalight are recommended for dental operatories +f this light is

not available@ color selection can be made near a window /owever@ even dalight

varies considerabl from da to da +t is wise to use multiple light sources when the

shade is determined 9hen using the dental operating light@ it should be moved

awa to decrease the intensit@ thus allowing the effect of shadows to be seen

The shade should be selected while the tooth is moist before cavit preparation and

application of rubber dam

+f there is a dilemma while selecting the shade@ especiall in older teeth@ it is better

to err on the barel perceptible darker side to allow for the age related darkening

+n choosing the correct shade@ hold the entire shade guide near the teeth to

determine general color Then select and hold the specific shade tab beside the area

of the tooth to be restored The shade tab should be partl covered with the patientBs

lip or the operatorBs thumb to create the natural effect of shadows The cervical area

of the tooth is usuall darker than the incisal area

) cured tr> in of the shade s that ou have selected offers a good idea of the

color of the final restoration Custom composite shade guides ma somehow

improve shade matching )ppropriate structure of the tooth to be replaced should be

assessed and test shades should be placed in a mock> up to assure ade%uate opacit

and color densit

-ewer sstems that are visible light> cured@ contain higher filler contents@ and are

modified with =3 absorbers and antio5idants are more resistant to color change

The should therefore be preferred to self> cure resins for restorations in the esthetic

zones

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The clinical challenge is to match the rate and tpe of color change of the

restoration with the tooth structure ) color mismatch that appears after several

ears is difficult to avoid Dentin is most likel to change color most rapidl during

middle age 1$> 7< ears old

There should be a gradual transition between the restoration and the tooth to obtain

an esthetic result #eveling the enamel tends to blend an color difference

associated with the margin over appro5imatel often shade selection from one single commercial brand

of composite does not meet the demanding needs of esthetic dentistr +n such a

case@ the restorative dentist is faced with the dilemma of using more than one resin

sstems to achieve an acceptable shade match Contrar to some manufacturersB

claims@ different tpes and brands of composites can be used together The two

common tpes of composites@ bis> 0M) and urethane dimethacrlate@ are

polmerizable b a free radical sstem@ and are capable of high cross> linking #oth

have identical reactive groups +t is probabl best to use laering rather than mi5ing

to integrate shades@ because mi5ing can incorporate air and cause voids in the

polmerized resin

+f bleaching occurs as a treatment of fi5ed duration@ restorative procedures should

be postponed until after teeth have assumed a stable lighter shade the

recommended period is at least 8 das /owever@ continual bleaching or on> and>

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off bleaching Adata bleachingI or Jweekend bleachingI generall makes it

impossible for the restoration shade to perfectl match tooth color -ewer whitening

toothpastes and continual bleaching ma have some effect on restoration surfaces as

well@ but these are not known

POOR RETENTION

The causes of poor retention include'

( Failure to re*o,e all !e1ris fro* e,er- surfae of t'e toot' to 1e restore! >

this ma result in Apeeling offB of the composite@ especiall interpro5imall

. Use of a +ro+'-lati +aste t'at ontains "l-erine an! fluori!e> these ma act

as barriers to etching solutions

7. Ina!euate +re+aration for*

+ncomplete e5cavation of caries

+nappropriate cavit preparation

2 Conta*ination of t'e o+eratin" area> 9ater or oil contamination from

handpiece or air> water sringes compromise the bond strength

$ Poor et'in" an! 1on!in" te'niues>

+nade%uate etching ma lead to incomplete resin tag formation *tching times

should be altered according to the tooth to be treated !onger etching times are

re%uired for sclerosed teeth or teeth with fluorosis +f a patient has a high caries

activit@ the enamel usuall etches ver easil Freshl cut enamel etches faster

than unprepared enamel

+f an etchant gel is used and inade%uate rinsing is performed@ the cellulose

vehicle ma act as a contaminant and reduce the bond strength of the subse%uent

restoration The recommended washing time for a gel etchant is a minimum of $

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seconds 0winnett advocates an e5tra (< seconds of airE water rinsing after use

of a gel etchant

Dring the etched enamel surface with the three>wa sringe is not advocated

due to the possibilit of oil contamination or water contamination from

condensation in the airlines after the compressed air has been dried

,ver dring etched dentin surfaces compromises dentine bonding as a result of

the collapse of the collagen network in the etched dentin surfaces This collapse

prevents optimal primer and adhesive penetration and compromises hbrid laer

formation Thus@ if both enamel and dentin have been etched@ the area should be

left slightl moistened +f dentin walls have been dried@ the ma be re> wetted

with a water> saturated applicator tip

The penetration of the dentine adhesive in sclerotic dentin ma be limited

+nade%uate primer placement> this will result in incomplete AwettingB

+ncomplete evaporation of the solvent also leads to compromised bond

strengths

!ack of uniform laer of bonding agent> pooling of bonding agent in line angles

and point angles ma lead to the appearance of radiolucent spots on the

radiograph which are difficult to differentiate from secondar caries This ma

also interfere with the complete seating of a resin composite inla or onla )ir K

thinning of bonding agent for a prolonged period is also known to compromise

the bond strengths

8. Inter*in"lin" of 1on!in" *aterials fro* !ifferent s-ste*s

8 Ina!euate urin" of t'e o*+osite resin>

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) decrease in output over time ma be attributed to lamp burnout@ bulb

blackening or frosting and reflector degradation all of which mandate lamp

replacement at least ever 7 months

Hordan has recommended that a minimum curing time of 2< seconds should be

used and the distance of the light tip to the composite should be as close as

possible to zero Presence of contamination@ such as composite material residue

on the light tip should also be checked for and eliminated

!ight absorption and scattering in resin composites reduces the power densit

and degree of conversion e5ponentiall with the depth of penetration +ntensit

can be reduced b a factor of (< to ( thick laer of composite

This reduces monomer conversion to an unacceptable level at depths greater

than .> 1mm

For ears@ the standard photoinitiator used in restorative resins has been

camphoro%uinone C6 This compound has an absorption ma5imum of 27$nm@

and the absorption peak ranges from 2$


20/25

: Ino*+ati1ilt- of a!'esi,es an! self9 !ual ure s-ste*s2 growing scientific

evidence demonstrates that simplified acidic adhesive sstems are incompatible

with selfE dual cured composites

; Ino*+ati1le te*+orar- restoration2 a zinc o5ide eugenol based temporar

restoration given prior to a composite resin restoration will lead to poor retention

as eugenol inhibits the polmerization of the resin Similarl@ use of a varnish also

contributes to poor strength

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eep area isolated when etching and bonding

For dring@ air from chip sringe should be used #lowing air from the air sringe

onto a dr surface as a test procedure will demonstrate easil if water contamination

is present ,il filters should be placed on the airlines after the air compressor and

before the sringe or handpiece Filters must be changed fre%uentl as suggested b

the manufacturer

Pooling of the bonding agent especiall at the line angles and point angles should be

avoided

The manufacturerBs instructions should be followed e5plicitl

+ntensit of the lamp should be checked regularl

Curing depth should be limited to .>1 mm unless e5cessivel long e5posure times

are used@ regardless of the lamp intensit

9hen attempting to polmerize the resin through tooth structure@ the e5posure time

should be increased b a factor of .>1 to compensate for the reduction in light

intensit

Do not intermingle bonding materials from different sstems

/igh> intensit@ short e5posure times provide substantial savings in chair time but

there ma be substantial residual stress buildup because insufficient time is allowed

for stress rela5ation@ even when used in combination with incremental buildup and

soft> start curing )t present@ this aspect has not been well investigated and these

tradeoffs should be considered before investing in e5pensive tpes of curing lamps

The clinician should ask for information on the emission spectrum of the curing

light which will enable himE her to determine if the light will cure the composite

being used

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To avoid problems related to incompatibilit@ clinicians are advised to use 1> step

total etch sstem or .> step self> etching adhesives when fabricating cores with

chemical or dual> cure composites

GAP FORMATION

Composite restorations that e5tend on the root surface ma e5hibit gap

formation at the ?unction of the composite and root This contraction gap occurs

because the force of polmerization shrinkage of the composite is greater than the

initial bond strength of the composite to the root dentin C> factor The 3> shaped gap

is composed of composite on the restoration side and hbridized dentin on the root

side The long>term effects of such gaps are not known /owever@ how long the

e5posed hbridized resin laer on the root stas intact is unknown@ and if it

deteriorates in a short time@ the area is left at risk to caries =se of a liner material ma

reduce the effect of the gap formation

#EAR

The principle concern for posterior for posterior composites has been that the

occlusal wear could occur at a high rate and continue over long periods of time@

e5posing underling dentin and leading to secondar caries or sensitivit Composite

wear results from a combination of chemical damage to the surface of the material

and mechanical breakdown The wear rate of composite materials to be used in

posterior restorations should be less than $ width restorations now indicates that the rate of occlusal

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wear tends to decrease over time@ with total wear approaching an average limiting

value of appro5imatel .$ (. months after placement

/OIDS

Porosities in composite resins can be incorporated at man stages of packing

and placement Porosities in a restoration contribute to reduced fatigue strength and

wear resistance and also increase the likelihood of microleakage Some important

points to be considered are'

Self> curing composites generall have a porosit of (> . G +n the case of visible

light cure composite materials@ porosities ma be minimized b vacuum loading of

the sringes

+ncidence of porosit is greater when the materials are placed with a hand

instrument than when the composite resin is in?ected directl

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The presence of pins often proves a difficult for the adaptation of a densel filled

composite resin

Slumping@ which is related to filler content and viscosit of the resin@ appears to be a

crucial factor when incremental placement of the resin is considered Provided that

the resin is given time to gloss over a form of slumping at the microscopic level@

small defects should smooth out@ leaving less opportunit for air incorporation if

another increment is placed over it

Cavities with rounded angles and eas access for resin placement should be

emploed ,ccurrence of porosit at the line angle produced b the gingival floor of

a pro5imal bo5 and the matri5 band could increase the risk of microleakage and

recurrent caries in an area that is particularl vulnerable to such problems because

of inaccessibilit

Stickier resins are more susceptible to porosit from instrument handling

Composite resins that re%uire minimal handling during restoration should be used

The use of Teflon> coated instrument is recommended

+f a void is detected immediatel after insertion of the restoration but before

contouring is initiated@ more composite can be added directl to the void area These

materials will bond because the void area has an o5gen> inhibited surface laer that

permits composite additions /owever@ if an contouring has taken place@ the

o5gen> inhibited laer ma have been removed or altered and the area must be re>

etched and adhesive placed before adding the composite

3UL5 FRACTURE OF COMPOSITE

Fracture through the main bulk of the restorative material is potentiall

dangerous@ particularl if a segment is retained within the cavit after becoming

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mobile "apid caries will develop as a result of pla%ue being admitted under the

mobile segment@ because it will be forced into the dentinal tubules b occlusal

pressure +t is preferable that the entire restoration be lost but the directl placed

plastic restorative materials are often retained because of the cavit design

#ulk fracture of posterior composite restorations is rare )lthough there has

been a persistent rumor that microfill composites are more sub?ect to fracture at the

occlusal contact areas@ there is no published evidence of that fact@ e5cept for a few

restorations 9hereas bulk fracture ma be the most prevalent failure mechanism for

high> copper amalgam restorations@ it is onl rarel observed for intracoronal

composite restorations ) glass ionomer base as a dentin> substitute under the

composite resin restoration has been advocated to reduce the further risk of caries

#ulk fracture is a more common mode of failure with composite inlas and

onlas +t often occurs in areas of cuspal coverage@ particularl if the restorative

material is thinner than .

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Failures and Management