Restorative Dentistry

Secondary caries: A literature reviewwith case reports

IvarA. Mjor, BDS, MSD, MS, DrOdontVFabioToffenetti, MD,

The clinicai diagnosis of secondary caries is by far the most common reason for repiacenient of restora-tions, but the scientific basis tor the diagnosis is meager. The purpose of this atliclG is to review the litera-ture on secondary (recurrent] caries and present case reports to document the problems encountered inthe clinicai diagnosis ot secondary caries. The literature on secondary caries was criticaliy reviewed andsubdivided into ciinical diagnosis, location ot secondary lesions, h i sto pathology, microieakage, and micro-bioiogy. The case reports included restorations that were scheduled to be replaced because of secondarycaries or stained margins of composite restorations. The lesions were photographed preoperatively andpostoperatively. Based on the limited literature avaiiabie, secondary caries appears to be a iocaiizediesion simiiar or identical to primary caries. It is most otten iocaiized gingivally on restorations. Narrowgaps, crevices, ditches, and "microieakage" do not lead to secondary caries, but wide voids may.Secondary caries is difiicull to diagnose clinically. Consistency or hardness and discoloration of dentin andenamel are the best parameters. Secondary caries is the same as primary caries located at the margin ofa restoration. (Quintessence Int 2000:31:165-179)

Key words: crevice, microleakage, replacement ol restorations, secondary caries, void

Secondary (recurrent) caries is not a well-definedentity, either clinicaily or histopathologically, and

meager information is available on its microbiology. Anumber of definitions from dictionaries and dentalpublications have been reviewed by Özer and Thyi-strup.' JVlany of the definitions focus on the spread ofcaries at the dentinoenamel junction (DEJ). Othersinclude failure to remove all diseased tissues in thedeep part and/or at the margin of cavity preparations.Some definitions include marginal defects of any sort.Lesions on previously unrestored surfaces of a restoredtooth is also sometimes referred to as secondary caries.Thus, no clear differentiation is made among secondarycaries, marginal defects, and residual or remainingcaries. This lack of a precise definition has resulted inuncertainty and confusion, not only among clinicalpractitioners, but also among the scientific community.

'Professor, Academy 100 Eminent Scfioiar, College of Dentistry, Universityof Florida. Gainesvilie, Fionda

'Private Practice, Gallarate, llaiy.

Reprint requests : Dr ivar A. fuljör, University of Fiorida, Coliege ofDentistry. Box 10041S, Gainesvilie, Fiorida 32610. E-maii: mjor@dentai.

ufi.edu

In the present review, the term secondary carieswill be limited to lesions at the margin of existingrestorations. The article wili focus on the clinical diag-nosis of secondary caries followed by a discussion ofits histopathoiogy and microbiology'. Following the lit-erature review, case reports will be presented. Thereviewed literature will be critically analyzed. The casereports involve restorations that were scheduled forreplacement because of secondary caries or stainedmargins of resin-based composite restorations. Thepreoperative diagnosis was followed by a clinicalassessment of the lesion after the restoration had beencarefully removed. The lesions were photographedpre- and postoperatively.

CLINICAL DIAGNOSIS

Numerous studies, since the early days of dentistry,have reported secondary caries as the mosf commonreason for replacement of restorations. The "rebegin-ning or recurrence of decay" at cavity margins, asdescribed by Black,- led to the "extension for preven-tion" principle of amalgam cavity preparations.Retrospectively, it is hard to understand the universalacceptance of this principle. It did emphasize the need

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to place cavit>' margins in areas accessible to inspec-tion and tTiechanical oral hygiene measures, such astoofhbrushing. The principle of extension for preven-tion implied that removal of tissue would prevent orreduce recurrence of lesions, but it discounted the factthat tissue removed is tissue lost and, therefore, notsubject to preventive measures. It was believed that, bymaking the restoration lTiargins accessible, extensionwould reduce the potential for new caries at cavitymargins in patients at a high risk for caries. SoiTie evi-dence has indicated that extensive Class II restora-tions with margins occlusal to the contact areadevelop more secondary caries than do those endinggingivally to the contact area.^ However, primarycaries usually develops just below the contact point,and, therefore, what is diagnosed as secondary cariesmay be primary caries left in situ.

Removal of healthy tissue in the name of preven-tion is not, and never should have been, consideredjustifiable in patients with a low caries risk or when-ever preventive measures can be effective. Becauseeffective measures to prevent caries are availabletoday, the extension for prevention principle cannotbe justified even in individuals at a high risk for caries.

Ample evidence has been presented from variousparts of the world during the last 50 years to confirmthat the clinical diagnosis of secondary caries is themost common reason for replacement of restorationsin general dental practice. "' Most studies have beendevoted to amalgam replacements, ie, the most com-mon restoration, but surveys of the reasons forreplacement of other types of direct restorations dur-ing the last 20 years have confirmed that all types ofdirect restorations, including glass-ionomers, are mostfrequently replaced because of the clinical diagnosis ofsecondary caries. Indirect restorations are also com-monly replaced because of secondary caries."""

Reports of SO /o to 60% secondary caries forrestorations scheduled for replacement are typical incross-sectional studies in general dental pracfices. Thishigh prevalence of secondary caries is not found incontrolled clinical trials, where 1% to 4% secondarycaries has been reported.'""-' However, the condifionsfor controlled clinical trials are different from those ina typical general dental practice. The use of speciallytrained and calibrated operators and assistants, work-ing without time constraints and often on a selectedclientele who practice optimal oral hygiene, tends tomask operator effects and technique sensitivity."These conditions generally provide results with ahigher specificity than do those in practice-basedresearch, which reinforces the importance of soundclinical practice and a concerned operator. Thus, whatappears to be a conflict in results is primarily a differ-ence in design and goals of the studies."' -*

However, the uncertainty and lack of consistency inthe diagnosis of secondary caries prevails.-' fnisview is substantiated by the observation t':i' ''"^ man-ner in which quesfions are asked and thi ' "^ Pro-vided for answers may affect the outcomi • .Lirveys ofreasons for replacement. For example, in a 'idy wherethe primary aim was to record the locai 'in of sec-ondary caries associated with individual restorations,only 2 alternatives as reasons for replacement wereprovided, "secondary caries" and "other reasons," ' andan exceptionally high percentage of secondary caries(72''/n) was recorded for amalgam restorafions in per-manent teeth. Furthermore, in a study of marginal fail-ures of amalgam and resin composite restorations, thepractitioners were asked to describe the clinicalappearance of the secondary caries after the restora-tions had been removed. Many clinicians omitted thispart of the study and those who did include it providedvague descriptions.'^

Thus, several questions arise: Do we really knowwhat is included in the diagnosis of secondary earies?Were dentists ever taught what the clinical diagnosisof secondary caries entails? If textbooks in operativedentistry reflect the teaching in dental schools, itmust be concluded that meager knowledge is avail-able for teachers and students to discuss. In textbooksseveral hundred pages long, from 1 or 2 sentences upto a half a column of text, based largely on empiri-cism, are all that is devoted to this major issue inoperative dentistry.''•^•' Not even textbooks on cariol-ogy devote significant text to this important area ofcariology.'='^ One book devotes part of a chapter torecurrent caries,^" but many of the concepts presentedhave been challenged." These observations are sur-prising, because the clinical diagnosis of secondarycaries represents billions of dollars in retreatmentcost per year worldwide. In fact, up to half of alloperative dentistry performed on adults involves thereplacement of restorations based on the diagnosis ofsecondary caries.

Few studies have attempted to differentiate betweenactive and arrested secondary caries, as is commonlydone in the assessment of primary caries. Kidd et al,'in a microbiologie study of caries, differentiatedbetween active and arrested secondary caries based onclinical criteria and the use of caries-detecting dyes.They found no difference in the microñora of primaryand secondary caries. Ozer'f outlitied detailed criteriato differentiate between early active and arrested sec-ondary earies. The proposed classification focused onenamel translueency, cavitation, color, and consis-tency of the dentin. Such subdivision of caries isimportant because active lesions may require opera-tive treatment, while arrested lesions do not, exceptfor esthetic reasons.

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LOCATION OF SECONDARY CARIES

Since Black's fundamental text was published,- it hasbeen recognized that secondary caries is prevalent gin-givally on Class 11 restorations. Its gingival location onClass II, III, IV, and V restorations has been con-firmed in several studies by clinically subdividing thesite of secondary caries adjacent to restorations intogingival, occlusal, or other sites '-^-^" or into moredetailed and well-defined sites. * Thus, special atten-tion should be given to the gingival margin of all typesof restorations. A number of factors may predispose arestoration to the development of gingival secondarycaries and they may be summarized as follows: clinicaltechnique, material properties, and oral hygiene.

Ciinicai technique

Moisture control, including rubber dam application, ismore difficult at the gingival margin of Class II, 111, IV,and V cavity preparations than in any other areas,especially if the gingival cavosurface margin is locatedsubgingivally. Visual inspection of the gingival floor isalso difficult at times, and the proper use of a matrix isimportant. Wedging of the matrLx interproximally mayalso be difficult and, if inadequate, overhangs tnightresult; these tend to act as plaque traps, leading to sec-ondary caries. * The gingival part of Class V restora-tions is at times challenging because of the proximityto the gingiva. As soon as a direct restorative materialis inserted, vision is obscured by the restorative mater-ial, and appropriate inspection cannot occur until thematerial has set and the matrix has been removed.

Finishing of cavosurface margins, voids, and porosi-ties may also affect the quality of restorations. Theseeffects are to some extent dependent on the propertiesof the restorative material and will be briefly discussedin the next section. Thus, a number of ciinicai factorsmay predispose the gingival margins of restorations tothe development of secondary caries.

Materiai properties

Application of pressure to triturated amalgam acceler-ates the setting,-" Therefore, condensation of a largemass of soft amalgam will result in an inhomogenousmass that soon hecomes difficult to handle- Voids andporosities often result, especially in corners and irregu-larities of the eavosurface margin of the preparation.-' -''Therefore, small increments of amalgam should heinserted quickly and firmly condensed into place imme-diately after trituration. A gradual buildup of an amal-gam restoration in this manner secures optimal qualityof the amalgam. Proper adaptation of the amalgam tothe cavity walls is especially important in the gingival

area of the restoration. Excess, voids, and porositiestnay act as plaque traps and lead to secondary caries.

Resin-based materials have the inherent problem ofcontraction on polymerization. This polymerizationcontraction tends to pull the material away from thecavosurface margins. Light-cured material will firstpolymerize where the light source hits the material.The gingival interproximal portion of Class II, III, andIV restorations will, therefore, cure last and tend topull away from the margin. This problem becomesacute if metal matrixes are used for Class II resinrestorations when the interproximal box is filled andthe curing ligbt is introduced occlusally. Clear matrixesand clear interproximal wedges that will spread thecuring light to the gingival cavosurface margin shouldhe employed to prevent gingival gaps."'''

Fluoride-releasing restorative materials havereceived attention during the last 20 to 30 years.Numerous studies have shown that fluoride leachesfrom glass-ionomer materials and fluoride-containingamalgams and resin composites in vitro''^"'" and invivo."'""' In vitro studies have also shown that fluoridemay be found in cavity walls that had been exposed toglass-ionomer cements and fluoride-containing amal-gam, -" ^ but these findings have been cballenged.^*Furthermore, the concentration of fluoride required toprevent secondary caries has not heen determined,and it can vary, depending on several factors. Thus,the presence of fluoride per se does not necessarilyresult in caries reduction. In fact, studies of reasonsfor replacement of restorations in general practiceindicate limited or no additional anticariogenic effectof fluoride released by glass-ionomer materials,^'-^*although controlled clinical trials with 3- to 5-yearobservation periods have indicated a low incidence ofsecondary caries*"- ' and a reduction of caries on teethadjacent to giass-ionomer restorations.^^

Recent studies have also shown that fluoride fromglass-ionomer cements can prevent secondary cariesin vitro but not in vivo."^-' If these restorations areused in patients with xerostomia who do not complywith the prescribed fluoride gel regimen, the glass-ionomer material may prevent secondary caries.However, if used in combination with intensive fluo-ride treatment, severe and detrimental degradation ofthe restoration may

Oral hygiene

Oral hygiene involves more than keeping the teethphysically clean by toothbrushing and interdentalflossing. An important part of toothbrushing is theapplication of fluoride present in the toothpaste.Development and progression of primary caries arelargely a result of inadequate plaque removal and lack

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of fluoride. Secondary caries has been shown todiminish at a rate similar to that of primary caries,mainly as a result of topical tluoricle availability,^ ' 'A significant correlation between the nimibers ofdecayed, missing, and filled teeth and secondary carieshas also been sbown.'' Any additional effect of fluo-ride from fluoride-releasing materials may, therefore,be difficult to demonstrate, especially because the flu-oride release may be of sbort duration.''^ Thus, rein-forcement of oral hygiene instructions specificailyfocusing on the gingival part of restorations should bean integral part of operative dentistry.™

HISTOPATHOLOGY

The first histopathologic examination of secondarycaries was carried out on teeth with amalgam restora-tions in vitro.'' Polarizing light microscopy revealed 2areas of secondary caries, an outer lesion and a walllesion that joined at the cavosurface margin. Furtherin vitro studies have confirmed the presence of these 2parts of secondary carious lesions.'-"'-' The outer lesionwas considered to be caused by plaque accumulationin a manner similar to tbe initiation of primary lesion,while the wall lesion was thought to be tbe result of"microleakage."'' Microleakage will be discussed in aseparate section.

The outer lesion has the characteristic features ofprimary caries: ie, the first clinical appearance wouldbe a typical white-spot lesion, including the opacity ofthe enamei. The opaque white color of early sec-ondary caries contrasts well with the shiny gloss ofintact enamel, but it may be affected by the color orcomponents of the adjacent restorative material, eg,components or degradation products of dental amal-gam. The early outer lesion will progress through thecharacteristic histologie stages. These stages are recog-nized on the basis of the size of pores developing inenamel as a result of demineraiization.'^ As the lesionprogresses, the surface layer breaks down, and a cavi-tated lesion will appear adjacent to the restoration.

The spread of secondary caries at the DEJ has heenassumed to occur in much the same way as it wasbeheved to occur witb primary caries, underminingthe enamel.'^ However, the extent of primary caries atthe DE| has been shown to correspond to the size ofthe enamel lesion and, therefore, it is not a lateralspread"; the same occurs with secondary caries, asshown by Ozer.'" Because tbe spread of both primarycaries'' and secondary caries'" in enamel follows tbeenamel rods, the existence of a wall lesion per seshould be questioned. It is likely that the direction ofthe enamel rods in relation to the tooth-restorationinterface will determine if a wall lesion will he present

and its extent. Thus, if the rods from a surface lesionreach the tooth-restoration interface, they will :;ive theappearance of a wall lesion. However, tli • ¡'"ii'io ot thelesion is at the enamel surface and not y •" °' ieali-age at the tooth-restoration interface. / issessmentof the marginal failures of amalgam an : compositerestorations with and without caries alsc ied to theconclusion that the outer lesion of secondary caries isthe most clinically important.^' Therefore, a review ofthe bistopathoiogic evidence presented for the exis-tence of a wall lesion in vivo^"^''^''^ should be per-formed in light of the recent findings presented.

The outer lesion of secondary caries on tbe rootsurface is considered to develop in tbe same way asprimary caries, but differential o ti between marginalstaining and caries is difficult.*° Root surface cariesstarts off as a subsurface lesion.' As demineralizationprogresses, the surface becomes soft and dark yellowor brown, depending on extrinsic factors.

MICROLEAKAGE

Leakage, usually referred to as microleakage, at thetooth-restoration interface has been considered to bethe cause of the development of wall lesions.'^ It hasalso become an established term in pulpal studies,especially related to the histologie demonstration ofbacteria at the toot h-rest oration interface."*""

Leakage refers to the act of letting fluid in or outaccidentally. Micro refers to something small orminute. Thus, microleakage means minute amounts offluid passed in or out. The terrn microleakage in rela-tion to secondary caries and pulpal studies focuses onthe presence of bacteria and tbeir nutrients in tbe fluidat the tootb-restoration interface. Altbough most ofthe oral bacteria arc nonpatbogenic, their presencehas a negative connotation in these contexts becausethey may lead to pulpal inflammation and secondarycaries. Hundreds of articles have been published onmicroleakage related to restorations. Microleakagestudies are commonly carried out in vitro by usingdyes, radioactive isotopes, and air pressure. Pulpalstudies that are not leakage studies per se focus on tbehistologie demonstration of bacteria at the tooth-restoration interface, which, indirectly, is consideredas evidence of leakage.

Extrapolation of in vitro data to in vivo situations isoften difficult and may lead to erroneous clinical con-clusions for a variety of reasons. The lack of a biofiimor pellicle of precipitated proteins from saliva, gingivalfluid, or dentinal fluid on surfaces and in crevices invitro is probably the main difference from the in vivocondition. Great caution is needed to interpret anyclinical significance of in vitro-induced caries.''^'' The

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microbial environment and the complex interactionshetween tooth and dental plaque arc characteristics ofin vivo caries, while in vitro caries is hasically a detnin-eralization process. Although the end results mayappear similar, the development is fundamentally dif-ferent. It is understandahle. therefore, that no or poorcorrelation has been found hetween the presence ofcrevices and the presence of secondary caries '" ^ ''- ^and ihat, as pointed out by Newbrun,'*' the validity,predictive value, and specificity of crevices for detec-tion of secondary caries are poor compared to findingsafter the restorations have heen removed-' or after theteeth have been sectioned.-"

Jorgensen and Wakumoto' -' claitned that gaps ofless than 35 to 50 pm at the tooth-restoration inter-face do not predispose to secondary caries but largergaps do; ie, mieroleakage would not tend to lead tosecondary caries. However, their in vitro study of sec-ondary caries lacked controls. After exatnining 9 loca-tions on the occiusal surface at a magnification of x70,they noted that a correlation between gap size andsecondary caries was only found at fissure sites, ie,where primary caries was likely to have been present.Thus, the study probably recorded remaining primarycaries rather than secondary caries.

In a recent study of secondary caries, Ozer '* foundthat the size of the gap between the tooth and therestoration has no influence on the initiation of caries,unless the gap size exceeds 250 pm, and then only if thegaps are not accessible to physical forces, including oralhygiene measures to clean the defects. Thus, no associa-tion appears to exist between wall lesions and so-calledmieroleakage. Plaque accumulation on the surface atthe site of development of secondary caries was consid-ered by Ozer " to be the decisive factor. Such accumula-tions are most often associated with gingival overhangson Class II amalgam restorations.'" It is also a commonclinical ohservation that secondary carious lesions areoften associated with fractured and mobile restorationsand under cemented cast restorations.

Radiography is of limited value in the diagnosis ofsecondary caries because of the shadowing effect ofthe restorative material.*' *'« Hewlett et al,*' in a radio-graphic study involving intact and defective restora-tions, claimed that the incidence of secondary caries is3-foid higher for defective restorations than for intactrestorations. However, they did not differentiatebetween secondary and residual caries.

MICROBIOLOGY

Considering the magnitude of the problem, it is sur-prising that the microbiology of secondary caries hasnot received more attention. In a study by Iiidd et al, ^

sampling the DEJ associated with amalgam restora-tions, more total bacteria, mutans streptococci, andlactobacilli were found in soft lesions than in hard ormedium-hard lesions. No difference was foundbetween samples derived from secondary caries lesionsand those from primary lesions. In more recent studiesof the margins of amalgam restorations,*" it was shownthat wide ditches or gaps (> 0,4 mm) contain morebacteria, tiiutans streptococci, and lactobaeilli than dointact margins or margins with narrower gaps. Theyconcluded that wide gaps indicate a need for replace-ment of the restoration. Narrow gaps should not beconsidered a reason for replacement of restorations.Color changes In the enamel alone could not berelated to the degree of infection of dentin, and suchchanges should not result in restoration replacement.'**

¡n a clinical and microbiologie study of margins oftootb-colored restorations, bactériologie samples weretaken at the restoration margin and at the DEJ afterthe restorations were removed,'^ The margins wereclassified as stained or stain free and as being intact orbaving a narrow or a wide ditch. Samples from siteswith frank caries were used for comparison. None ofthe elinieal criteria could predict the presence of softinfected dentin. Only frank caries at the margin of therestoration was considered a reliable indication of sec-ondary caries, and fewer than a quarter of these lesionshad soft dentin at the DEJ.

An inherent problem with microbiologie studies ofsecondary caries is differentiating it from remainingcaries, as in the investigation by Fitzgerald et al, '*where caries subjacent to intact amalgam restorationswas studied and referred to as "recurrent dental caries."The authors did, however, call for more focused stud-ies. Mertz-Fairhurst et al-' published 10-year resultsthat showed no progression of extensive occlitsal cariessealed without removal of any tooth tissue exceptbeveling of the enamel margins surrounding thelesions. Thus, it appears that active caries may becomeinactive or arrested if it is adequately sealed from theoral environment.

It is the opinion of the atJthors that the conclusionby Özer " that secondary caries is primary caries adja-cent to restorations is correct, which is in conformity'with the conclusion of Kidd and Beighton.** However,because the pellicle on restorative materials varies, " ^it is likely that the initial plaque at restoration marginswill difter. Svanberg ct aF have shown that the plaquesamples from amaigam, composite, and glass-ionomerrestoration margins differ in bacterial composition,including the proportion of mutans streptococci. Alow number of mutans streptococci in saliva does notpreclude a high concentration of these microorganismsin plaque from the margin of individual restorations.'^Further microbiologie studies of restoration margins

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and plaque on restorative materials are therefore indi-cated, with particular attention to the composition ofthe pellicle on restorative materiais.

CONCLUSION BASED ON LITERATURE REVIEW

Recent evidence indicates that the initiation and pro-gression of secondary caries is a localized phenome-non similar to that causing primary caries. Evidencehas been presented to show that secondary caries canbe prevetited by measures such as tluoride availabilityand plaque control. The microbiology of secondarycaries is similar or identical to that of primary caries.

Gaps, crevices, and ditches that do not exhibit char-acteristic changes associated with caries, ie, softening oftissues, color changes, and/or cavitation, are not aloneindications for replacement of restorations, except pos-sibly for esthetic reasons. Ditching is a common charac-teristic of the occiusai surface, and secondary caries isonly rarely found in this location. Much attention mustbe paid to the gingival part of restorations during cavitypreparation and during insertion, carving, and finishingof restorations. Microieakage may cause unsightly mar-ginal discoloration of footh-colored restorations, whichmay call for repair or replacement but is not an indica-tion for replacement of restorations with the intent toprevent secondary caries. It does not lead to walllesions, ie, caries at the tooth-restoration interface.Secondary caries is primary caries adjacent to arestoration. It may be active or arrested and should betreated accordingly.

Cavitation, consistency or hardness, and color ofdentin and enamel are considered to be the best clini-cal parameters for determining the activity and extentof both primary and secondary caries. Discoloration ofthe enamel and dentin may assist in the diagnosis,provided that the restorative material has not affectedthe tissue, as amalgam often does. However, hardnessof the tissue supersedes color in the final determina-tion of the extent and activity of caries.

CASE REPORTS

The clinical implication of the concluding remarks wasassessed in a project in which the preoperative diag-noses of secondary caries and marginal staining ofcomposite restorations had been noted. The restora-tions were photographed preoperativeiy and after theircareful removal; special care was taken not to removeany tooth tissue from the caidty wall at the site wheresecondary cañes or stain was diagnosed. The sites werethen clinically inspected, evaluated, and photographed.Selected representative cases will be described and

illustrated. Cases that were difficult to assesif avA thatdid not lead to a clear conclusion related ti . ndarycaries or its relationship to stained margii. • iH alsobe presented.

Case 1

The preoperative diagnosis in this case was simple (Figla). Extensive secondary caries adjacent to the gingi-val half of a poorly condensed, pitted, and corrodedClass V amalgam restoration called for replacement ofthe restoration. The amalgam was carefully removedso that a thin rim was left incisally (Fig lb). The cariesextended in some areas to the pulpal floor of the cav-ity. There was no evidence of spread of caries at thecavity floor or subjacent to the amalgam or the basethat had been used.

Case 2

A localized secondary carious lesion was noted gingi-val to a Class V composite restoration (Eig 2a). Theentire margin was discolored to a variable degree, withpossible secondary caries along the stained margin.After careful removal of the restoration, in which thesubjacent base was left partially in situ (Fig 2b), nei-ther a wall lesion nor any extension of the cariesunder the base material couid be noted.

Case 3

Secondary caries was diagnosed gingivaily adjacent toa Class V composite restoration (Fig 3a), The carieswas discolored and soft gingivally, but the incisai partof the restoration was intact. The restoration wasremoved, leaving part of the base in situ (Fig 3b). Nowail lesion could be found. Some surface discolorationwas still present. The cavity preparation was extendedto include the discolored tissue and acid etched (Fig3c). The final composite restoration satisfied all estheticrequirements (Eig 3d).

Retrospectively one may wonder if the dissection ofthe dark brown line gingivally to the restoration, cou-pied with a superficial dentinoplasty, followed by arepair, also would have provided a satisfactory result.Such an approach would have saved a considerableamount of tooth tissue.

Case 4

Secondary caries was diagnosed on the niesioincisalmargin of a Class ill composite restoration in a max-illary right canine (Fig 4a). The restoration extendedbuccally into the Class V area. Apart from the mesialsecondary caries, the restoration was judged to be

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Case 1

Fig l a Ciass V amalgam restoration with extensive sec-ondary caries gingivaily. The carious tissue is yellowishbrown and soti

Fig 1b The 'es'.oialion shown in Fig la has been carefuliylemoved so tnai some amalgam on the occlusal eavosur-face margin and part of the base material are ieft in situ.There is no indication of the spread of the carious tissuesubjacent to the restoration. Gingivaiiy. the carious lesionextends the tuli depth of the restoration.

Case 2

Fig 2a Ciass V composite resrarationa localized discolored, soft carious lesiongingivaily. The entire cavosurfaoe margin isdiscolored.

Fig 2b Tfie restoration shown in Fig 2a hasbeen carefuliy removed without touching theadjaoent tooth, tvlost of the base materiai isstiil intact. The light brown, soft tissue pre-sent gingivaiiy is weii iocalized and is acharacteristic surface lesion adjacent to arestoration. No so-cailed wail lesion can bediscerned.

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Fig 3a Class V composite restoration witha stained gingival margin, suspected to becarious.

Fig 3b The restoration shown in Fig 3a hasbeen removed without touohing the cavo-surface margin. Stained, but hard, tissueremains oh the surface beyond the cavosur-face margin. Some t:ase material remains,but there is no sign of a wali iesion.

Fig 3c The cavity preparation shown in Fig3ti has been compieted and aoid etched.The oavity preparation is larger than therestoration in Fig 3a,

Fig 3d A new Class V composite restora-tion has lepiaced the restoration shown inFig 3a.

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Case 4

Fig 4a Class III composite restoration extending into theClass V area ot the maxillary right canine. The localizedstained margin can be penetrated by a stiarp explorer.

Fig 4b The resin composite adjacent to ttie stained marginshown ih Fig 4a was removed, resulting in the completeremoval ot the stain. No wall lesion can be discerned, andthe stain did hot extend deep into (he tooth-resto ration inter-face.

Fig 4c The small defect shown in Fig 4b has beenrepaired after acid etching, priming, and bonding accordingto the usual restoration procedures.

Fig 4d The results of the repair are satisfaotory.

clinically acceptable. Enough of the restorative mate-rial was removed to determine the extent of tbelesion. No caries was found on the cavity wall adja-cent to the lesion, and the stain was removed (Fig4b). The light yellow-brown dentin exposed by thepreparation was bard. Undercuts were prepared inthe composite material, and the defect was repairedby restoring it in a conventional manner with com-posite (Fig 4c). The final result was considered satis-factory by the patient, the dental student clinician,and the instructor (Fig 4d).

Cases

Two adjacent composite restorations on central andlateral incisors were esthetically unacceptable, andsecondary caries was suspected at the gingival floor ofboth restorations (Fig 5a). After both restorations werecarefully removed, no visible carious lesion could bedetected on the cavity margins. The walls of the cavityin the lateral incisor were considered to be caries free(Fig 5b). Tbe orange-brown dentin at the cervicobuc-cal margin and at the DE| on tbe central incisor washard and considered to be arrested residuai caries.

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Case 5

Fig 5a Mesiai and distal disooiored composite restorationsin 2 incisors, both with suspected gingival secondaryoaries.

Fig 5b Botin restorations shown in Fig 5a have been care-(uily removed, i o carious lesions oan be discerned gingi-vaiiy. Some base material remains in the iaterai incisor, Tiiestained dentinoenamei junction and stained dentin on tiiegingival and puipai tioor ot the centrai inoisor are hard andconsidered to be arrested oaries.

Case 6

Fig 6a Ciass iii resin oomposite restoration in the caninethat oauses a "catch" with the explorer Seoondary caries issuspected.

Fig 6b Ttie composite restoration shown in Fig 6a liasbeen caretuliy removed. No carious tissue oan be detectedgingivaliy.

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Case 7

Fig 7a Class HI composite re^A-i' i-ion :r, lino roiated lateralincisor, diagnosed as having secondary canes gingivallyThe canine is missing.

Fig 7b The composite restoration stiown \r\ Fig 7a hasbeen removed No caries is noted on the gingival margin.

Case 6

A defective composite restoration on the distal aspectof a maxillary canine was judged to have secondarycaries gingivally (Eig 6a). Removal of the restorationrevealed no caries on the cavity margin or on the cav-ity wall (Eig 6b). The stained dentin at the DE] in someareas was hard and considered to be arrested caries.

Case 7

A large Class III composite restoration on a maxillarylateral incisor was diagnosed with secondary caries atthe distocervical margin (Fig 7a). The canine wasmissing. After careful removal of the restoration, nosecondary caries could be detected on the cavity mar-gin or on the cavity walls (Eig 7b).

Cases

The patient complained of sensitivity in the region ofthe maxillary second premolar and first molar.Radiographs of the area indicated possible cariesunder the restoration in the second premolar and aprimary lesion mesially on the first molar (Fig 8a).Clinically, the second premolar showed a dull gray dis-coloration through the enamel buccally, which is char-acteristic of secondary caries or remaining canes dis-colored by amalgam (Fig 8b),

After removal of the amalgam restoration in thesecond premolar, a wail lesion was noted at the DEJ(Eig 8c). Recause the gingival floor appeared intact, itis likely that this iesion represented remaining cariesfrom the previous treatment that had become discol-ored by the amalgam or mere discoloration of themantle dentin (which is normally less mineralizedthan the adjacent dentin). The dark color indicatedthat it was arrested caries, but the semihard consis-tency called for its removal. After the mesial portion ofthe occlusal amalgam restoration in the first molarwas removed, orange-stained, soft caries was found inthe mesial box of the cavity (Eig 8d). The access to themesial iesion of the molar also revealed a distal pri-mary lesion on the premolar that had not been radio-graphically diagnosed (Eig öa). Tlie discolored primarycaries was visible in the distai box of the premolar, justextending into the peripheral dentin.

CLINICAL REMARKS

The S case reports presented illustrate the difficultiesencountered in clinical diagnosis of failing restora-tions. Stained margins are obvious when they are asso-ciated with tooth-colored restorations, and they do notseem to predispose the restoration to the developmentof secondary caries. If the discolored margin is limitedin extent, it should be repaired by dissecting away the

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Cases

Fig 8a Radiograph of a maxiiiary molar and premolarregion of a patient who compiained of sensitivity m the sec-ond premoiar and first molar region. Tfie radiograph indi-cates possibie secondary and/or remaining caries in thesecond piemciar and a probable pnmary lesion mesially enthe first molar.

Fig 8b Clinical situation of the region shown in Fig 8a. Thebluish-gray discoloration on the mesiobuccal aspect of thesecond premolar may be indicative of secondary caries ordisccioration of the tissues by the amalgam

Fig 8c Removal of the amalgam restoratioh in the seccndpremoiar reveals a narrow line of demineralized ¡opaquewhite) enamel on the gingival lloor and sott carious tissue inthe distal box of the Class II preparation, Indicative olremaining caries and development ol a carious lesion gingi-vaily.

Fig 8d Later stage of the operative procedure ot the teethpresented in Figs 8a to 8c. Note the distinct carious iesion onthe first molar and a smail iesion just reaohing into dentin inthe distal box of the premolar Ttie latter lesion was notdefected radiographically.

stain; the focus should be on removal of minimal toothtissue by gaining access through the restorative mate-rial. This approach is also congruent with the nowcommonly accepted view that ditched amalgam mar-gins should be smoothed by grinding or polishing,repaired with amalgam, or sealed with a fissure sealantrather than replaced. The case reports presented andclinical experience support the view that replacementof restorations based on the suspicion of secondarycaries or microleakage is not justified.

Difficulties in the differentiation among stainedrestoration margins, secondary caries, and residualcaries are well-known. This situation, coupled withthe dilemma of clinically discriminating betweenactive and arrested caries, calls for studies to increasethe knowledge and improve diagnosfic criteria for sec-ondary caries. Ciinical experience, verified by thecases presented, indicates that secondary caries doesnot extend along the restoration-tooth interface toundermine the enamel or the restoration per se. When

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soft and discolored dentin is found subjacent to arestoration, it is usually caries left behind during theprevious restorative procedure or it is associated witha surface lesion that can be diagnosed clinicallyand/or radiographically. The fate of residual cariesmay be dependent on the sealing of the restoration.The recent study in which gross occlusal caries wasintentionally sealed in^° indicated that remainingcaries may be arrested following restoration.

ACKNOWLEDGMENTS

This review was supported in part by N;nitinal Institutes of Health/NaiLOnat Institute of Denial Resear[;h grant 2P50 DE 09Î07-09.

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! Answers to Ql 12/99 Questionsi

1. A2. A3. D4. B

5. C6. B7. D8. D

9. A10. D11. C12. A

13.14.15.16.

DCBA

Quintessence internationai 179