Effect of bleaching on restorative materialsand restorationsa systematic review

Thomas Attin*, Christian Hannig, Annette Wiegand, Rengin Attin

Department of Operative Dentistry, Preventive Dentistry and Periodontology,Georg-August-Universitat Gottingen, Robert-Koch-Str. 40, D-37075 Gottingen, Germany

Received 6 November 2003; received in revised form 1 April 2004; accepted 6 April 2004

KEYWORDSPeroxide; Bleaching;

Restoration; Bonding;

Composite resin;

Amalgam

Summary Objective: Internal and external bleaching procedures utilizing 335%hydrogen peroxide solutions or hydrogen peroxide releasing agents, such as carbamideperoxide or sodium perborate, can be used for whitening of teeth. The purpose of thereview article was to summarize and discuss the available information concerning theeffects of peroxide releasing bleaching agents on dental restorative materials andrestorations.

Sources: Information from all original scientific full papers or reviews listed inPubMed or ISI Web of Science (search term: bleaching AND (composite OR amalgam ORglass ionomer OR compomer OR resin OR alloy) were included in the review.

Data: Existing literature reveals that bleaching therapies may have a negative effecton physical properties, marginal integrity, enamel and dentin bond strength, and colorof restorative materials as investigated in numerous in vitro studies. However, thereare no reports in literature indicating that bleaching may exert a negative impact onexisting restorations requiring renewal of the restorations under clinical conditions.

Conclusion: Bleaching may exert a negative influence on restorations andrestorative materials. Advice is provided based on the current literature to minimizethe impact of bleaching therapies on restorative materials and restorations.Q 2004 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Introduction

Recent reviews underlined that both bleaching ofdiscolored vital and non-vital teeth has a long andsuccessful history [1,2]. For brightening discoloredteeth, the use of hydrogen peroxide or peroxidereleasing agents, such as carbamide peroxide orsodium perborate, has become a popular treatmentmodality. A recently published review showed thattooth bleaching teeth is comparatively safe interms of potential risk for alteration of dental

hard tissue [3]. This corresponds to the fact thatmacroscopically or clinically visible damage due tovital bleaching has not been described in theliterature so far, although it is reported thatbleaching of non-vital teeth using the walking-bleach-technique involves the risk of developmentof external cervical resorptions [1,4]. Despite thefact that vital bleaching is not regarded as creatingmacroscopically visible defects, there are numer-ous studies which exhibited microstructuralchanges of dental hard tissue induced by bleachingagents, especially when peroxides are appliedin high concentrations [5]. Thereby, alterationof the histological aspects and compositionof bleached enamel has been described [612].

Dental Materials (2004) 20, 852861

www.intl.elsevierhealth.com/journals/dema

0109-5641/$ - see front matter Q 2004 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.doi:10.1016/j.dental.2004.04.002

*Corresponding author. Tel.: 49-551-392884; fax: 49-551-392037.

E-mail address: thomas.attin@med.uni-goettingen.de

It was also reported that slight surface alterations,as assessed by scanning electron microscopy, and adecrease of surface microhardness and fracturetoughness might occur due to bleaching of dentalhard tissues [1322]. These possible effects ondental hard tissues are discussed as being minimaland not relevant provided that the bleaching agentsare applied in a sensible manner and according tothe manufacturers instructions [1,19,20]. Besidethese aspects regarding influence of bleachingagents on dental hard tissues, some clinicians alsoexpress concern about the effect of these agents ondental restorative materials [23,24].

The purpose of the present article is to summar-ize the available information concerning the effectsof bleaching agents on dental restorative materials.All original scientific full papers or reviews listed inPubMed or ISI Web of Science (search term:bleaching AND (composite OR amalgam OR glassionomer OR compomer OR resin OR alloy) wereincluded in the review, but abstracts dealing withthis topic were not taken into consideration. Casereports were included only when they exclusivelyreport observations which were not described inother publications.

The influence of various bleaching agents onphysical properties, surface morphology and colorof different restorative materials, has been inves-tigated in several in vitro-studies simulating theclinical situation as closely as possible. In thosestudies, home-bleaching products (1016% carba-mide peroxide) were generally used within a 24week bleaching simulation with application inter-vals of 48 h per day. Tooth-whiteners designed forin-office-application (3035% hydrogen or carba-mide peroxide) were applied at treatment intervalsof 1560 min (as recommended by the manufac-turers). These different bleaching regimes werepreferably used in the studies reviewed and aretherefore not repeatedly mentioned when describ-ing and discussing the results of the respectivestudies. However, it should be borne in mind thatthe total time period of application was muchhigher for the low concentrated regimes than forthe highly concentrated ones.

Effect of bleaching agents on propertiesof restorative materials

Composite resins

In some scanning electron microscopic studies andprofilometric analysis, it was shown that 1016%carbamide peroxide bleaching gels (i.e. 3.65.76%

hydrogen peroxide) may lead to a slight, butstatistically significant increase in surface rough-ness and amount of porosities of microfilled andhybrid composite resins [2527]. These findingswere not corroborated in a SEM-study applying 6%hydrogen peroxide gel on a hybrid composite in acycling protocol with intermittent storage of thesamples in pooled human saliva [28]. It is con-ceivable that storage in saliva might have modifiedor attenuated the hydrogen peroxide impact byformation of a surface-protection salivary layer onthe restorative material. In microfilled specimensalso, cracking was observed after application of 10%carbamide peroxide for the above mentionedperiod of 4 weeks [27]. Usage of tooth whitenerscontaining 3035% hydrogen peroxide did not effectthe surface texture as revealed with profilometricalanalysis [29,30]. Similar results were describedusing 20 and 35% carbamide peroxide gel for 3 and1 h per day, respectively, during a period of 14 days[31]. However, analysis of surface reflectanceshowed significant changes in microfilled and hybridcomposite resins after application of highly con-centrated tooth whiteners with 3035% hydrogenperoxide [29]. The authors suggested that thechanges in surface reflectance reveal more subtlechanges in the surface and perhaps also in theimmediate subsurface. In this context it should alsobe mentioned that salivary proteins absorbed ontothe surface of composite materials decreased afterbleaching with peroxide containing agents, which issuggested to have an influence on bacterialadhesion of cariogenic bacteria, such as Strepto-coccus sobrinus and Streptococcus mutans, but notof Actinomyces viscosus [32].

There is controversy about the impact of lowconcentrated 1016% carbamide peroxide gels onsurface microhardness of restorative compositematerials. In some investigations softening ofcomposite resins was associated with the appli-cation of home-bleaching gels [27,33]. Otherinvestigations revealed no significant hardnesschanges [34,35] due to application of home-bleaching gels or even an increase in surfacehardness [25,36]. In-office-tooth whiteners (35%carbamide peroxide or 35% hydrogen peroxide) didnot significantly affect hardness and tensilestrength of composite materials [37,38].

For standardized and reproducible evaluation ofcolor changes of restorative materials, colori-meters are used analyzing L*a*b* values accordingto the CIELab-system [39,40]. It has been claimedthat under clinical conditions in the mouth, DEcolor differences have been reported to be relevantand perceptible only when higher than 3.3 [41]or 3.6 [42]. Application of 10% hydrogen peroxide or

Bleaching and restorative materials 853

heated 30% hydrogen peroxide resulted in compo-site color changes which were presumably clinicallydetectable with DEp ranging between 2 and 11 forthe different materials and shades tested [43,44].In contrast, use of 10% carbamide peroxide gel ledto color changes of composite resins less than DEp 2and these were comparable to color changes ofunbleached samples stored in water only [44,45].However, even 10% carbamide bleaching agentswere able to remove extrinsic stains from compo-site restorative materials [46].

Polyacid-modified resin-based composites,resin-modified glass ionomer cements, glassionomer cements and zinc oxide cements

Highly concentrated bleaching regimes inducedsurface degradation, softening, an increase influoride release and changes in the coefficient ofthermal expansion of polyacid-modified resin-basedcomposites (compomers) when those bleachingagents were continuously applied for 15 days[47,48]. In some products, even cracks wereobserved on the surface of the specimens. However,a total of three 30-min bleaching sessions conductedat 1-week intervals, as recommended by themanufacturers, did not result in detrimental effectsof the surface finish of compomers, resin-modifiedglass ionomer cements or glass ionomer cements[30]. In contrast, after treatment with 1016%carbamide peroxide bleaching gels, an increase insurface roughness for some brands of thosematerials were noted, while other gels displayeddecreased surface roughness, suggesting that theeffects of the gels seem to be material dependent[25,26]. Jefferson et al. [49] examined alterationsof atomic weight percentages in glass ionomercement after contact with 10% carbamide peroxidewith pH 4.5 and reported that the matrix of thespecimens showed surface wash-off and corrosionwith the cores of the silica more exposed and adecrease of surface aluminum content. In contrastto these findings, both high and low concentratedbleaching agents did not show any influence onfluoride release of dental materials, such asconventional and resin-modified glass ionomercements [50]. Additionally, it was recently provedthat a low concentrated 6% hydrogen peroxide geldid not cause significant dissolution or increasedwear rate of glass ionomer cements [51].

The occurrence of visible color changes incompomers treated with 10% carbamide peroxidewere, likewise, the changes in surface texture,dependent on the brand tested, whereas treatmentwith 10 and 30% hydrogen peroxide resultedin noticeable color change irrespective of

the compomer material evaluated [44,52]. Super-ficial, extrinsic stain could be removed successfullywith 10% carbamide peroxide from resin-modifiedglass ionomer cement, but not from a polyacid-modified resin-based composite [46]. Microhard-ness of resin-modified glass ionomer cementsincreased [33] or remained stable [36] after treat-ment with 10% carbamide peroxide gels. Utilizinghighly concentrated bleaching regimes, no surfacemicrohardness changes were observed in polyacid-modified resin-based composites or resin-modifiedglass ionomer cements [38].

Feldspathic porcelain

The only investigations on the effect of bleachingagents on ceramic restorative materials wereperformed by Turker and Biskin [25,33], whoevaluated the effects of bleaching agents onfeldspathic porcelain. They observed that 1016%carbamide peroxide gels (applied for 8 h per day for30 days) were able to significantly decrease surfacehardness of the porcelain material tested. How-ever, surface texture was not effected by thebleaching regimen, as also reported in an SEMinvestigation by Schemehorn et al. [28], whenapplying a 6% hydrogen peroxide gel on feldspathicporcelain.

Provisional materials

Jefferson et al. [49] described a decrease inaluminum and an increase in porosity in zinc oxidecement after immersion in acidic 10% carbamideperoxide solutions. Zinc oxide surface levels of IRMfillings were significantly reduced due to influenceof 10% carbamide peroxide, but not after appli-cation of 10% hydrogen peroxide, which, however,led to cracking and expansion of the tested material[53]. The color of provisional restorative materialsdesigned for fabrication of crowns were reported tochange after 14 days of simulated bleaching with10% carbamide peroxide gel dependent on theprovisional material tested. Thereby, methacry-late-based materials showed a shift to orange ordingy, whereas polycarbonate crowns and bis-acrylcomposite resin provisional material were notdiscolored [54].

Amalgam and other dental alloys

Low concentrated hydrogen peroxide gels (6%) donot alter the surface texture of either high-copperamalgam or type III gold alloy [28]. However,evaluation of corrosion current density of variousdental alloys revealed that the application of 10%

T. Attin et al.854

carbamide peroxide solution on non-polished amal-gam samples and nickelchromium specimens maycause corrosion of these materials, but not of noblealloys. In this study, it was also shown that thebleaching agent caused lower corrosion potentialfor the polished amalgam samples compared tonon-polished specimens [55]. Beside this study,revealing the alteration of corrosive potential ofsome dental alloys, various laboratory studies havereported increased release of amalgam com-ponents, such as mercury and silver, from amalgamspecimens exposed to 10% carbamide peroxide or10% hydrogen peroxide preparations [56 58].Active oxidation was held to be responsible forthe increased release of amalgam components andalso for greening of the tooth-amalgam interfaceclinically observed by Haywood [59] duringextended 10% carbamide bleaching. In vitro studiesshowed that the amount of mercury release wasdependent on both the amalgam and carbamideperoxide brand tested [56,57,60]. Also, increasingcarbamide peroxide concentrations led to anincrease in amalgam mercury release. Thereby,the mercury release ranged from 0 to 30 timesas much as compared to the controls whichwere stored in saline or phosphate buffer solutions[58,60,61]. The mercury release from amalgamseems also to be modified by the presence of biofilmon amalgam containing saliva, bacteria and poly-saccharide, since an experimentally induced biofilmcoating on amalgam has shown to reduce mercuryrelease into the surrounding environment [62].However, it should be noted that the abovementioned experiments had been conducted invitro and that the mercury release might be morepronounced than in the in vivo situation.

Reasons for the impact of bleaching agentson properties of restorative materialsand clinical consequences

The alterations in color of the restorative materialshave been attributed to oxidation of surfacepigments and amine compounds, which have alsobeen indicated as responsible for color instability ofrestorative materials over time. Differences incolor change between different materials mightbe a result of different amount of resin anddifferent degrees of conversion of the resin matrixto polymer [43]. Also surface phenomena, such asincrease in porosities, are discussed as a result ofthe deleterious impact of the oxidizing bleachingagents on the polymer-matrix of resin-basedmaterials [37]. Additionally, it was debatedwhether the negative influences of the oxidizingagents on the resin matrix led to water uptake of

the restorative materials with complete or partialdebonding of fillers causing reduced surface integ-rity and loss of hardness of the materials [30].

Unfortunately, in none of the above mentionedstudies were investigated how far the inducedporosities, increased surface roughness andreduction in surface hardness of the testedmaterials led to recommendable need for replace-ment of existing restorations after bleaching toensure longevity of the restorations. Therefore, itremains speculative whether these changes ofsurface texture and hardness are relevant underclinical conditions or if they are barely a surfacephenomenon, which could be removed by simplepolishing of restorations. However, polishing of therestorations after bleaching is advisable at least,since the increased surface roughness is held to beresponsible for increased adherence of certaincariogenic microorganisms to the outer surface oftooth-colored restorative materials after contactwith different bleaching agents as assessed by Moret al. [63].

The oxidizing effect of the bleaching agents isalso held responsible for the observed higher rate ofmercury release from amalgam. In order to reducepatient exposition to amalgam components, polish-ing of amalgam restorations prior to starting of ableaching therapy should be performed to reducecorrosion potential of the amalgam restorations.Additionally, pre-coating of amalgam surfaces witha protective varnish such as copalite (10% copalresin in a combination of ether, alcohol andacetone) seems to be advisable to reduce releaseof mercury into the surrounding environment duringbleaching with 10% carbamide peroxide [57].

Effect of bleaching agents on bondstrength of restorative materialsto enamel and dentin

Bond strength of composite resins to enamel

Numerous studies have addressed the questionwhether various bleaching procedures effect thebond strength of composite resins to enamel speci-mens prepared from bovine or human teeth. Onlyone study was available which considered thisaspect using resin-modified glass ionomer cement[64]. The overwhelming majority of studies utilizing2535% hydrogen peroxide uniformly showed thatboth shear bond strength and tensile bond strengthof all composite restorative materials tested weresignificantly reduced when composite application(including acid-etching pretreatment) was

Bleaching and restorative materials 855

performed immediately, i.e. within 1 day, aftercompletion of bleaching regime [6572].

This was true irrespective of the application time(5, 30 or 60 min, respectively) of the 35% hydrogenperoxide solution during the bleaching procedure[6873]. It was shown that resin tags in bleachedenamel subsequently acid etched with 37% phos-phoric were less defined, more fragmented andpenetrated to a lesser depth than in unbleachedenamel controls [69].

Teixeira et al. [74,75] simulated the walking-bleach-technique by placement of various highlyconcentrated bleaching agents into the pulpchamber of tooth specimens for 4 weeks. Enamelbond strength of composite materials tested onenamel slabs prepared from those teeth was onlyreduced when a mixture of sodium perborate with30% hydrogen peroxide was applied, but not afteruse of either 37% carbamide peroxide or a mixtureof sodium perborate with water. This reduction inshear bond strength was valid until a 7-d-post-bleaching period elapsed before bonding. Studiesinvestigating the appropriate time point for bond-ing of composites to enamel after termination of in-office bleaching with 2535% hydrogen peroxidereported that bond strength returned to normalvalues when the composite was applied on thespecimens 24 h [65] or 2 weeks [72] after bleaching.Other studies also showed that a delay of 1 weekwas not long enough to allow for optimal bonding[66,67,73,76], although peroxide completely lea-ches from 35% hydrogen bleached enamel alreadywithin 7 days after application [77].

Only a single investigation suggested that bondstrength of brackets bonded to acid etched enamelimmediately after in-office bleaching with 35%hydrogen peroxide was not significantly affected[78]. However, failure analysis showed thatunbleached controls primarily failed at thebracket/adhesive interface, whereas bleachedgroups either showed cohesive failures within theadhesive or failed at the adhesive/enamel interfaceas also reported in other investigations [70]. Thisfinding, therefore, also supports the assumptionthat the adhesion of resin to bleached enamel andalso the properties of the adhesively attached resinare negatively affected by the bleaching procedureperformed before bonding.

Also, most of the studies investigating theinfluence of carbamide peroxide gels on adhesive-ness of enamel revealed reduction of enamelcomposite bond strength compared to unbleachedenamel [66,7982]. Thereby, bond strengthreduction was similar for carbamide peroxide gelsconcentrated between 10 and 20% [83]. Only fewstudies did not find a negative impact of carbamide

peroxide (10%) bleaching on composite-enamelbond strength [17,64]. Similar to the bond strengthreduction described above for enamel bleachedwith highly concentrated hydrogen peroxide sol-utions, the bond strength return to normal valueswhen the composite is applied to the enamel after atime lapse. Recommendations for application ofcomposite materials onto carbamide peroxidebleached enamel ranged from 1 day [79], 37 days[66,84], to 3 weeks [83]. The effect of bondingagent on composite bond strength to enamelbleached with carbamide peroxide gel seems todepend on the bonding agent used [85]. However,controversy exists whether acetone-based adhesivesystems are generally able to reverse the negativeeffects of carbamide peroxide bleaching on com-posite enamel bond strength. Sung et al. [85]reported that a significant difference betweenacetone-based adhesive aided bond strength forbleached and unbleached enamel was registered,but not for the alcohol-based adhesive tested. Incontrast, other authors reported that an acetone-based adhesive and also other water-clearingsolvents, such as pure acetone or alcohol, wereable to significantly reduce the adverse effects ofbleaching on composite-enamel bond [82,86].

Only one study dealt with the adhesion of resin-modified glass ionomer cements to pre-bleachedenamel. It was shown that the resin-modified glassionomer cement used for bracket bonding was notaffected by pre-bleaching of enamel with 10%carbamide peroxide at 24 h and 14 days afterbleaching [64].

Bond strength of composite resins and glassionomer cements to dentin

Bond strength of restorative materials to dentin hasnot been investigated intensively. The few studieswhich are available reported unanimously about areduction of dentin bond strength for compositeand glass ionomer cements for both bleaching with3035% hydrogen peroxide and 1021% carbamideperoxide [76,8791]. This finding was true irrespec-tive of the adhesive systems used for bonding ofcomposite materials. In most of the studies,reduction in bond strength was, like the effect inenamel, still present after an elapse of 7 daysbefore application of the tested materials to thebleached dentin specimens [76,87,89]. OnlyDemarco et al. [91] reported that dentin bondstrength of composite was not impaired whenbonding was delayed for 1 week after bleachingtreatment with 30% hydrogen peroxide.

T. Attin et al.856

Reasons for the impact of bleaching agentson bond strength of restorative materialsand clinical consequences

Several aspects are held to be responsible for thereduction in composite bond strength to bleachedenamel and dentin. Bleaching with hydrogen per-oxide or hydrogen peroxide-releasing agents mayresult in significant decrease of enamel calcium andphosphate content and in morphological alterationsin the most superficial enamel crystallites [8,92].Moreover, acid etching of bleached enamel surfaceproduced loss of prismatic form resulting in anenamel surface which appeared to be over-etched[17]. Additionally, it was suggested that the enameland dentin organic matrix was altered by theoxidizing effect of hydrogen peroxide [93,94].These aspects may lead to an enamel surface,which did not allow for formation of a strong andstable bond between the composite applied and thesuperficial etched enamel layer. Furthermore,reduction in bond strength in hydrogen-peroxide-treated enamel and dentin could be caused byresidual oxygen present in enamel and dentin poresafter completion of the bleaching treatment.Liberation of the oxygen could either interferewith resin infiltration into enamel and dentin [66,76] or inhibit polymerization of resins that cure viaa free-radical mechanism [95]. The latter aspectmight result in oxygen-inhibited polymerization ofthe composite components directly in contact withthe dental hard tissues leading to a soft interfacenot able to withstand debonding forces sufficiently.Interestingly, SEM examinations demonstrated thatacid etching following 30% hydrogen peroxide usagedid not totally remove the smear layer on dentinsurfaces [91]. This fact might presumably impairthe interaction between dentin adhesives appliedwith total-etching-technique and dentin. For theglass ionomer cement it is also discussed that thesetting of the cement is inhibited by oxygenremnants [87]. The recommendations for a 13week delay before placement of composite or glassionomer restorations after termination of bleachingtherapy are made under the assumption that theresidual oxygen may have sufficient time to leachfrom the dental hard tissues. To dissolve remnantsof peroxide, cavities can also be cleaned withcatalase or 10% sodium-ascorbate [96 99].However, application of these agents might betime-consuming or expensive, so that furtherinvestigations are needed to optimize their useunder clinical conditions. It is therefore morefeasible to follow the above mentioned recommen-dations to allow for contact time of at least 7 days

with water to avoid the reduction of adhesion ofcomposites to enamel [67,73,77]. Optimal bondingto pre-bleached dental hard tissue could beachieved after a period of about 3 weeks [83,100].

Effect of bleaching agents on marginalquality of restorations

Composite resins

Pre-restorative non-vital, intra-coronal bleachingin the sense of walking-bleach-technique usingmixtures of 37% carbamide peroxide or pastesconsisting of 30% hydrogen peroxide and sodiumperborate leads to a higher rate of microleakage incomposite restorations of both the access cavityand class-V cavities placed immediately aftertermination of bleaching [75,100102]. In class-Vrestorations, the increase of microleakage afterintra-coronal application of 37% carbamide per-oxide was only detected in dentin margins and notin enamel margins [100]. The rate of microleakageof restored access cavities increased with increas-ing duration of the application of the sodiumperborate hydrogen peroxide mixture [102].Thereby, a 7-day application resulted in inferiorsealing compared to a 1- or 4-day application.Short-term use of intracoronal calcium hydroxidemedicament for 7 days after completion of walking-bleach therapy was able to reverse the negativeinfluences of the hydrogen peroxide application onmicroleakage of access cavities [101].

Controversy exists about the influence of pre-operative external bleaching with 10% carbamideperoxide on microleakage of composite restor-ations. Crim [103] reported that 10% carbamideperoxide did not impair the marginal seal of class-Vrestorations placed at the cementoenamel junc-tion. In contrast, in a study by Ulukapi et al. [104],microleakage rates of labial restorations withenamel margins only, were significantly increasedafter 10% carbamide peroxide bleaching. Similarfindings were reported by Turkun and Turkun [96],who observed significant reduction in sealing ofaccess cavities with composite resins up to 1 weekafter application of 10% carbamide peroxide intothe pulp chamber.

Two studies reported that the post-operativecontact of composite restorations with 35% hydro-gen peroxide or 1016% carbamide peroxide geladversely affected the marginal seal at both dentin[105] and enamel [104] margins. In contrast, otherstudies did not find increased microleakage rates atleast at enamel margins [105,106].

Bleaching and restorative materials 857

Polyacid-modified resin-based composites,resin-modified glass ionomer cements,amalgam and temporary materials

Only two studies addressed to the impact of post-operative bleaching (35% hydrogen peroxide or316% carbamide peroxide) on restorations withenamel margins fabricated with polyacid-modifiedresin-based composites, resin-modified glass iono-mer cements or amalgam [104,106]. In bothstudies, no deterioration of marginal seal wasrevealed. Marginal leakage of amalgam restorationswith enamel margins only were also not negativelyinfluenced by pre-operative external bleaching with10% carbamide peroxide [104].

It was indicated that temporary restorativematerials, such as TERM, zinc-oxide-eugenolcement and zinc oxide phosphate cement, did notprovide an optimal seal when used for provisionalrestoration of the access cavity during internalbleaching with the walking-bleach technique usinga mixture of 30% hydrogen peroxide with sodiumperborate as bleaching agent [107,108]. That wasalso true for composite materials applied withoutacid-etching technique when tested for provisionalseal of the access cavity [107]. The most favorableresults with respect to cavosurface seal duringinternal bleaching were demonstrated for hydraulicfilling materials, such as Cavit and Coltosol [107].

Penetration of the pulp chamber bybleaching agents in restored teeth

It was observed that during external bleaching with30% hydrogen peroxide or 1035% carbamideperoxide gel higher levels of hydrogen peroxidepenetrated into the pulp chamber in teeth withrestorations placed in enamel as compared to soundteeth [109,110]. This was true for restorationsfabricated with either composite materials, poly-acid-modified composite resins or resin-modifiedglass ionomer cements. Furthermore, it was shownthat higher concentrated carbamide peroxide gels(35%) lead to distinct higher levels of peroxide inthe pulp chamber compared to low (10%) concen-trated gels [111].

Clinical consequences of the impactof bleaching agents on restorations

The above mentioned studies underline thatpre- and post-operative bleaching procedures maynegatively affect marginal seal of restorations.Moreover, restorations and margins of restorationscould be regarded as a possible pathway facilitating

peroxide penetration into the pulp chamber.Peroxide penetration into the pulp chamber isheld responsible for pulpal reactions, such asincrease in tooth hypersensitivity, during externalbleaching of vital teeth [112,113]. Dentists shouldtherefore examine restorations meticulously beforestarting a bleaching therapy and renew insufficientfillings prior to bleaching in order to achieve anoptimal seal of the pulp chamber and thus reducingthe risk of adverse effects. Future studies mustinvestigate how far the higher rate of microleakageobserved in vitro lead to problems with existingrestorations in the clinical situation.

Conclusions

Bonding of adhesively attached restorations to pre-bleached dental hard tissue is significantly reduced.Therefore, it is recommended to delay placementof restorations after termination of bleachingtherapy for at least 13 weeks. Additionally,bleaching therapies with hydrogen peroxide orhydrogen peroxide releasing preparations mayhave a negative effect on restorations and restora-tive materials as shown in numerous in vitroinvestigations. It remains unclear in how far thoseobservations may result in significant deteriorationof restorations under clinical conditions. However,there are no reports in the literature indicating thatbleaching may exert any negative impact onexisting restorations thereby requiring renewal ofthe restorations. Nevertheless, further investi-gations are necessary to elucidate these aspectmore precisely.

References

[1] Attin T, Paque F, Ajam F, Lennon AM. Review of thecurrent status of tooth whitening with the walking bleachtechnique. Int Endod J 2003;36:31329.

[2] Haywood VB. History, safety, and effectiveness of currentbleaching techniques and applications of the nightguardvital bleaching technique. Quintessence Int 1992;23:47188.

[3] Dadoun MP, Bartlett DW. Safety issues when usingcarbamide peroxide to bleach vital teetha review of theliterature. Eur J Prosthodont Restor Dent 2003;11:913.

[4] Friedman S, Rotstein I, Libfeld H, Stabholz A, Heling I.Incidence of external root resorption and esthetic resultsin 58 bleached pulpless teeth. Endod Dent Traumatol1988;4:236.

[5] Dahl JE, Pallesen U. Tooth bleachinga critical review ofthe biological aspects. Crit Rev Oral Biol Med 2003;14:292304.

[6] Wandera A, Feigal RJ, Douglas WH, Pintado MR. Home-usetooth bleaching agents: an in vitro study on quantitative

T. Attin et al.858

effects on enamel, dentin, and cementum. QuintessenceInt 1994;25:5416.

[7] Crews KM, Duncan D, Lentz D, Gordy FM, Tolbert B. Effectof bleaching agents on chemical composition of enamel.Miss Dent Assoc J 1997;53:201.

[8] Perdigao J, Francci C, Swift EJ, Ambrose WW, Lopes M.Ultra-morphological study of the interaction of dentaladhesives with carbamide peroxide-bleached enamel. AmJ Dent 1998;11:291301.

[9] Potocnik I, Kosec L, Gaspersic D. Effect of 10% carbamideperoxide bleaching gel on enamel microhardness, micro-structure, and mineral content. J Endod 2000;26:2036.

[10] McGuckin RS, Babin JF, Meyer BJ. Alterations in humanenamel surface morphology following vital bleaching.J Prosthet Dent 1992;68:75460.

[11] McCracken MS, Haywood VB. Demineralization effects of10 percent carbamide peroxide. J Dent 1996;24:3958.

[12] Burgmaier GM, Schulze IM, Attin T. Fluoride uptake anddevelopment of artificial erosions in bleached and fluori-dated enamel in vitro. J Oral Rehabil 2002;29:799804.

[13] Bitter NC. A scanning electron-microscopy study of theeffect of bleaching agents on enamela preliminary-report. J Prosthet Dent 1992;67:8525.

[14] Bitter NC, Sanders JL. The effect of four bleaching agentson the enamel surface: a scanning electron microscopicstudy. Quintessence Int 1993;24:81724.

[15] Seghi RR, Denry I. Effects of external bleaching onindentation and abrasion characteristics of human enamelin vitro. J Dent Res 1992;71:13404.

[16] Ernst CP, Marroquin BB, Willershausen-Zonnchen B. Effectsof hydrogen peroxide-containing bleaching agents on themorphology of human enamel. Quintessence Int 1996;27:536.

[17] Josey AL, Meyers IA, Romaniuk K, Symons AL. The effect ofa vital bleaching technique on enamel surface morphologyand the bonding of composite resin to enamel. J OralRehabil 1996;23:24450.

[18] Attin T, Kielbassa AM, Schwanenberg M, Hellwig E. Effectof fluoride treatment on remineralization of bleachedenamel. J Oral Rehabil 1997;24:2826.

[19] Attin T, Muller T, Patyk A, Lennon AM. Influence ofdifferent bleaching systems on fracture toughness andhardness of enamel. Oper Dent 2004;29:18895.

[20] Chng HK, Palamara JE, Messer HH. Effect of hydrogenperoxide and sodium perborate on biomechanical proper-ties of human dentin. J Endod 2002;28:627.

[21] Attin T, Kocabiyik M, Buchalla W, Hannig C, Becker K.Susceptibility of enamel surfaces to demineralization afterapplication of fluoridated carbamide peroxide gels. CariesRes 2003;37:939.

[22] Wiegand A, Otto YA, Attin T. In vitro evaluation oftoothbrushing abrasion of differently bleached bovineenamel. Am J Dent 2004; in press.

[23] Swift Jr EJ, Perdigao J. Effects of bleaching on teeth andrestorations. Compend Contin Educ Dent 1998;19:81520.

[24] Swift Jr EJ. Restorative considerations with vital toothbleaching. J Am Dent Assoc 1997;128(Suppl):60S4S.

[25] Turker SB, Biskin T. Effect of three bleaching agents on thesurface properties of three different esthetic restorativematerials. J Prosthet Dent 2003;89:46673.

[26] Cehreli ZC, Yazici R, Garcia-Godoy F. Effect of home-usebleaching gels on fluoride releasing restorative materials.Oper Dent 2003;28:6059.

[27] Bailey SJ, Swift Jr EJ. Effects of home bleaching productson composite resins. Quintessence Int 1992;23:48994.

[28] Schemehorn B, Gonzalez-Cabezas C, Joiner A. A SEMevaluation of a 6% hydrogen peroxide tooth whitening gel

on dental materials in vitro. J Dent 2004;32(Suppl 1):359.

[29] Bowles WH, Lancaster LS, Wagner MJ. Reflectance andtexture changes in bleached composite resin surfaces.J Esthet Dent 1996;8:22933.

[30] Wattanapayungkul P, Yap AUJ. Effects of in-office bleach-ing products on surface finish of tooth-colored restor-ations. Oper Dent 2003;28:1519.

[31] Langsten RE, Dunn WJ, Hartup GR, Murchison DF. Higher-concentration carbamide peroxide effects on surfaceroughness of composites. J Esthet Restor Dent 2002;14:926.

[32] Steinberg D, Mor C, Dogan H, Zacks B, Rotstein I. Effect ofsalivary biofilm on the adherence of oral bacteria tobleached and non-bleached restorative material. DentMater 1999;15:1420.

[33] Turker SB, Biskin T. The effect of bleaching agents on themicrohardness of dental aesthetic restorative materials.J Oral Rehabil 2002;29:65761.

[34] Nathoo SA, Chmielewski MB, Kirkup RE. Effects of colgateplatinum professional toothwhitening system on micro-hardness of enamel, dentin, and composite resins.Compend Contin Educ Dent Suppl 1994;S62730.

[35] Garcia-Godoy F, Garcia-Godoy A, Garcia-Godoy F. Effectof bleaching gels on the surface roughness, hardness, andmicromorphology of composites. Gen Dent 2002;50:24750.

[36] Campos I, Briso AL, Pimenta LA, Ambrosano G. Effects ofbleaching with carbamide peroxide gels on microhardnessof restoration materials. J Esthet Restor Dent 2003;15:17582.

[37] Cullen DR, Nelson JA, Sandrik JL. Peroxide bleacheseffect on tensile-strength of composite resins. J ProsthetDent 1993;69:2479.

[38] Yap AU, Wattanapayungkul P. Effects of in-office toothwhiteners on hardness of tooth-colored restoratives. OperDent 2002;27:13741.

[39] Buchalla W, Attin T, Hilgers RD, Hellwig E. The effect ofwater storage and light exposure on the color andtranslucency of a hybrid and a microfilled composite.J Prosthet Dent 2002;87:26470.

[40] Inokoshi S, Burrow MF, Kataumi M, Yamada T, Takatsu T.Opacity and color changes of tooth-colored restorativematerials. Oper Dent 1996;21:7380.

[41] Ruyter IE, Nilner K, Moller B. Color stability of dentalcomposite resin materials for crown and bridge veneers.Dent Mater 1987;3:24651.

[42] Johnston WM, Kao EC. Assessment of appearance match byvisual observation and clinical colorimetry. J Dent Res1989;68:81922.

[43] Monaghan P, Trowbridge T, Lautenschlager E. Compositeresin color-change after vital tooth bleaching. J ProsthetDent 1992;67:77881.

[44] Canay S, Cehreli MC. The effect of current bleachingagents on the color of light-polymerized composites invitro. J Prosthet Dent 2003;89:4748.

[45] Monaghan P, Lim E, Lautenschlager E. Effects of homebleaching preparations on composite resin color.J Prosthet Dent 1992;68:5758.

[46] Fay RM, Servos T, Powers JM. Color of restorativematerials after staining and bleaching. Oper Dent 1999;24:2926.

[47] Lee JH, Kim HI, Kim KH, Kwon YH. Effect of bleachingagents on the fluoride release and microhardness of dentalmaterials. J Biomed Mater Res 2002;63:53541.

[48] Jung CB, Kim HI, Kim KH, Kwon YH. Influence of 30%hydrogen peroxide bleaching on compomers in their

Bleaching and restorative materials 859

surface modifications and thermal expansion. Dent MaterJ 2002;21:396403.

[49] Jefferson KL, Zena RB, Giammara B. Effects of carbamideperoxide on dental luting agents. J Endod 1992;18:12832.

[50] Robertello FJ, Meares WA, Gunsolley JC, Baughan LW.Effect of peroxide bleaches on fluoride release of dentalmaterials. Am J Dent 1997;10:2647.

[51] Mair L, Joiner A. The measurement of degradation andwear of three glass ionomers following peroxide bleaching.J Dent 2004;32(Suppl 1):415.

[52] Kwon YH, Kwon TY, Kim HI, Kim KH. The effect of 30%hydrogen peroxide on the color of compomers. J BiomedMater Res 2003;66B:30610.

[53] Rotstein I, Cohenca N, Mor C, Moshonov J, Stabholz A.Effect of carbamide peroxide and hydrogen peroxide onthe surface morphology and zinc oxide levels of IRMfillings. Endod Dent Traumatol 1995;11:27983.

[54] Robinson FG, Haywood VB, Myers M. Effect of 10 percentcarbamide peroxide on color of provisional restorationmaterials. J Am Dent Assoc 1997;128:72731.

[55] Canay S, Cehreli MC, Bilgic S. In vitro evaluation of theeffect of a current bleaching agent on the electrochemicalcorrosion of dental alloys. J Oral Rehabil 2002;29:10149.

[56] Rotstein I, Dogan H, Avron Y, Shemesh H, Steinberg D.Mercury release from dental amalgam after treatmentwith 10% carbamide peroxide in vitro. Oral Surg Oral MedOral Pathol 2000;89:2169.

[57] Rotstein I, Dogan H, Avron Y, Shemesh H, Mor C, SteinbergD. Protective effect of copalite surface coating on mercuryrelease from dental amalgam following treatment withcarbamide peroxide. Endod Dent Traumatol 2000;16:10710.

[58] Robertello FJ, Dishman MV, Sarrett DC, Epperly AC. Effectof home bleaching products on mercury release from anadmixed amalgam. Am J Dent 1999;12:22730.

[59] Haywood VB. Greening of the tooth-amalgam interfaceduring extended 10% carbamide peroxide bleaching oftetracycline-stained teeth: a case report. J Esthet RestorDent 2002;14:1217.

[60] Hummert TW, Osborne JW, Norling BK, Cardenas HL.Mercury in solution following exposure of various amal-gams to carbamide peroxides. Am J Dent 1993;6:3059.

[61] Rotstein I, Mor C, Arwaz JR. Changes in surface levels ofmercury, silver, tin, and copper of dental amalgam treatedwith carbamide peroxide and hydrogen peroxide in vitro.Oral Surg Oral Med Oral Pathol 1997;83:5069.

[62] Steinberg D, Blank O, Rotstein I. Influence of dental biofilmon release of mercury from amalgam exposed to carba-mide peroxide. J Biomed Mater Res 2003;15:62731.

[63] Mor C, Steinberg D, Dogan H, Rotstein I. Bacterialadherence to bleached surfaces of composite resin invitro. Oral Surg Oral Med Oral Pathol 1998;86:5826.

[64] Homewood C, Tyas M, Woods M. Bonding to previouslybleached teeth. Aust Orthod J 2001;17:2734.

[65] Dishman MV, Covey DA, Baughan LW. The effects ofperoxide bleaching on composite to enamel bond strength.Dent Mater 1994;10:336.

[66] McGuckin RS, Thurmond BA, Osovitz S. Enamel shear bondstrengths after vital bleaching. Am J Dent 1992;5:21622.

[67] Titley KC, Torneck CD, Ruse ND, Krmec D. Adhesion of aresin composite to bleached and unbleached humanenamel. J Endod 1993;19:1125.

[68] Torneck CD, Titley KC, Smith DC, Adibfar A. The influenceof time of hydrogen peroxide exposure on the adhesion ofcomposite resin to bleached bovine enamel. J Endod 1990;16:1238.

[69] Titley KC, Torneck CD, Smith DC, Chernecky R, Adibfar A.Scanning electron microscopy observations on the pen-etration and structure of resin tags in bleached andunbleached bovine enamel. J Endod 1991;17:725.

[70] Titley KC, Torneck CD, Smith DC, Adibfar A. Adhesion ofcomposite resin to bleached and unbleached bovineenamel. J Dent Res 1988;67:15238.

[71] Stokes AN, Hood JA, Dhariwal D, Patel K. Effect of peroxidebleaches on resinenamel bonds. Quintessence Int 1992;23:76971.

[72] van der Vyver PJ, Lewis SB, Marais JT. The effect ofbleaching agent on composite/enamel bonding. J DentAssoc S Afr 1997;52:6013.

[73] Torneck CD, Titley KC, Smith DO, Adibfar A. Effect ofwater leaching on the adhesion of composite resin tobleached and unbleached bovine enamel. J Endod 1991;17:15660.

[74] Teixeira EC, Hara AT, Turssi CP, Serra MC. Effect ofnonvital tooth bleaching on resin/enamel shear bondstrength. J Adhes Dent 2002;4:31722.

[75] Teixeira EC, Hara AT, Turssi CP, Serra MC. Effect of non-vital tooth bleaching on microleakage of coronal accessrestorations. J Oral Rehabil 2003;30:11237.

[76] Torneck CD, Titley KC, Smith DC, Adibfar A. Adhesion oflight-cured composite resin to bleached and unbleachedbovine dentin. Endod Dent Traumatol 1990;6:97103.

[77] Adibfar A, Steele A, Torneck CD, Titley KC, Ruse D.Leaching of hydrogen peroxide from bleached bovineenamel. J Endod 1992;18:48891.

[78] Uysal T, Basciftci FA, Usumez S, Sari Z, Buyukerkmen A.Can previously bleached teeth be bonded safely? Am JOrthod Dentofacial Orthop 2003;123:62832.

[79] Titley KC, Torneck CD, Ruse ND. The effect of carbamide-peroxide gel on the shear bond strength of a microfil resinto bovine enamel. J Dent Res 1992;71:204.

[80] Garcia-Godoy F, Dodge WW, Donohue M, OQuinn JA.Composite resin bond strength after enamel bleaching.Oper Dent 1993;18:1447.

[81] Cvitko E, Denehy GE, Swift Jr EJ, Pires JA. Bond strength ofcomposite resin to enamel bleached with carbamideperoxide. J Esthet Dent 1991;3:1002.

[82] Barghi N, Godwin JM. Reducing the adverse effect ofbleaching on compositeenamel bond. J Esthet Dent 1994;6:15761.

[83] Cavalli V, Reis AF, Giannini M, Ambrosano GMB. The effectof elapsed time following bleaching on enamel bondstrength of resin composite. Oper Dent 2001;26:597602.

[84] Miles PG, Pontier JP, Bahiraei D, Close J. The effect ofcarbamide peroxide bleach on the tensile bond strengthof ceramic bracketsan in vitro study. Am J OrthodDentofacial Orthop 1994;106:3715.

[85] Sung EC, Chan SM, Mito R, Caputo AA. Effect of carbamideperoxide bleaching on the sheer bond strength ofcomposite to dental bonding agent enhanced enamel.J Prosthet Dent 1999;82:5959.

[86] Kalili T, Caputo AA, Mito R, Sperbeck G, Matyas J. In vitrotoothbrush abrasion and bond strength of bleachedenamel. Pract Periodontics Aesthet Dent 1991;3:224.

[87] Titley KC, Torneck CD, Smith DC, Applebaum NB. Adhesionof a glass ionomer cement to bleached and unbleachedbovine dentin. Endod Dent Traumatol 1989;5:1328.

[88] Toko T, Hisamitsu H. Shear bond strength of compositeresin to unbleached and bleached human dentine. Asian JAesthet Dent 1993;1:336.

[89] Spyrides GM, Perdigao J, Pagani C, Araujo MA, Spyrides SM.Effect of whitening agents on dentin bonding. J EsthetDent 2000;12:26470.

T. Attin et al.860

[90] Far C, Ruse D. Effect of bleaching on fracture toughness ofcomposite-dentin bonds. J Adhes Dent 2003;5:17582.

[91] Demarco FF, Turbino ML, Jorge AG, Matson E. Influence ofbleaching on dentin bond strength. Am J Dent 1998;11:7882.

[92] Ruse ND, Smith DC, Torneck CD, Titley KC. Preliminarysurface analysis of etched, bleached, and normal bovineenamel. J Dent Res 1990;69:16103.

[93] Kodaka T, Toko T, Debari K, Hisamitsu H, Ohmori A,Kawata S. Application of the environmental SEM in humandentin bleached with hydrogen-peroxide in vitro.J Electron Microsc 1992;41:3816.

[94] Hegedus C, Bistey T, Flora-Nagy E, Keszthelyi G, Jenei A.An atomic force microscopy study on the effect ofbleaching agents on enamel surface. J Dent 1999;27:50915.

[95] Rueggeberg FA, Margeson DH. The effect of oxygeninhibition on an unfilled/filled composite system. J DentRes 1990;69:16528.

[96] Turkun M, Turkun LS. Effect of nonvital bleaching with 10%carbamide peroxide on sealing ability of resin compositerestorations. Int Endod J 2004;37:5260.

[97] Lai SCN, Tay FR, Cheung GSP, Mak YF, Carvalho RM, WeiSHY, Toledano M, Osorio R, Pashley DH. Reversal ofcompromised bonding in bleached enamel. J Dent Res2002;81:47781.

[98] Rotstein I. Role of catalase in the elimination of residualhydrogen-peroxide following tooth bleaching. J Endod1993;19:5679.

[99] Lai SC, Mak YF, Cheung GS, Osorio R, Toledano M, CarvalhoRM, Tay FR, Pashley DH. Reversal of compromised bondingto oxidized etched dentin. J Dent Res 2001;80:191924.

[100] Shinohara MS, Rodrigues JA, Pimenta LAF. In vitromicroleakage of composite restorations after nonvitalbleaching. Quintessence Int 2001;32:4137.

[101] Demarco FF, Freitas JM, Silva MP, Justino LM. Microleak-age in endodontically treated teeth: influence of calciumhydroxide dressing following bleaching. Int Endod J 2001;34:495500.

[102] Barkhordar RA, Kempler D, Plesh O. Effect of nonvitaltooth bleaching on microleakage of resin compositerestorations. Quintessence Int 1997;28:3414.

[103] Crim GA. Prerestorative bleaching: effect on microleakageof class V cavities. Quintessence Int 1992;23:8235.

[104] Ulukapi H, Benderli Y, Ulukapi I. Effect of pre- and post-operative bleaching on marginal effect of leakage ofamalgam and composite restorations. Quintessence Int2003;34:5058.

[105] Crim GA. Post-operative bleaching: effect on microleak-age. Am J Dent 1992;5:10912.

[106] Owens BM, Rowland CC, Brown DM, Covington III JS.Postoperative dental bleaching: effect of microleakage onclass V tooth colored restorative materials. J Tenn DentAssoc 1998;78:3640.

[107] Hosoya N, Cox CF, Arai T, Nakamura J. The walking bleachprocedure: an in vitro study to measure microleakage offive temporary sealing agents. J Endod 2000;26:7168.

[108] Waite RM, Carnes Jr DL, Walker III WA. Microleakage ofTERM used with sodium perborate/water and sodiumperborate/superoxol in the walking bleach technique.J Endod 1998;24:64850.

[109] Gokay O, Tuncbilek M, Ertan R. Penetration of the pulpchamber by carbamide peroxide bleaching agents on teethrestored with a composite resin. J Oral Rehabil 2000;27:42831.

[110] Gokay O, Yilmaz F, Akin S, Tuncbilek M, Ertan R.Penetration of the pulp chamber by bleaching agents inteeth restored with various restorative materials. J Endod2000;26:924.

[111] Benetti AR, Valera MC, Mancini MN, Miranda CB, Balducci I.In vitro penetration of bleaching agents into the pulpchamber. Int Endod J 2004;37:1204.

[112] Hanks CT, Fat JC, Wataha JC, Corcoran JF. Cytotoxicityand dentin permeability of carbamide peroxide andhydrogen-peroxide vital bleaching materials, in vitro.J Dent Res 1993;72:9318.

[113] Robertson WD, Melfi RC. Pulpal response to vital bleachingprocedures. J Endod 1980;6:6459.

Bleaching and restorative materials 861

Effect of bleaching on restorative materials and restorations-a systematic reviewIntroductionEffect of bleaching agents on properties of restorative materialsComposite resinsPolyacid-modified resin-based composites, resin-modified glass ionomer cements, glass ionomer cements and zinc oxide cementsFeldspathic porcelainProvisional materialsAmalgam and other dental alloysReasons for the impact of bleaching agents on properties of restorative materials and clinical consequences

Effect of bleaching agents on bond strength of restorative materials to enamel and dentinBond strength of composite resins to enamelBond strength of composite resins and glass ionomer cements to dentinReasons for the impact of bleaching agents on bond strength of restorative materials and clinical consequences

Effect of bleaching agents on marginal quality of restorationsComposite resinsPolyacid-modified resin-based composites, resin-modified glass ionomer cements, amalgam and temporary materialsPenetration of the pulp chamber by bleaching agents in restored teethClinical consequences of the impact of bleaching agents on restorations

ConclusionsReferences