correlation between clinical scoring of secondary caries at crown

Fixed crowns have been used for decades to restoredecayed teeth1–3 and may be considered a standard

procedure in dentistry. Based on several studies, the

longevity of fixed prosthodontics is well docu-mented.4,5 After 5 years, 98.5% of the investigatedcrowns were still in situ.6 Failures may be caused bypoor esthetic performance of the restoration.Furthermore, technical complications such as corro-sion of the metal framework or fractures of the ve-neering material may lead to a replacement of therestoration. However, biologic complications, in-cluding marginal periodontitis, endodontic complica-tions, and especially secondary caries, are the mainreasons for rating fixed prosthodontics as unaccept-able.7 In most epidemiologic studies, the ratingschemes for caries lesions localized at the crown mar-gin differentiate between presence/absence of sec-ondary caries,8–10 early/deep caries,11 or accept-able/not acceptable margins.7 The reliability of theclinical secondary caries diagnosis in describing thehistologic outcome has not been investigated. Basedon current quality criteria for fixed prosthodontics,12

The International Journal of ProsthodonticsVolume 13, Number 6, 2000 453

Purpose: The aim of this study was to propose a new clincial diagnostic rating index forsecondary caries lesions at crown margins and to correlate this index with histologicevaluations. Materials and Methods: Based on criteria for the evaluation of root caries, amodification for secondary caries lesions at the crown margin (SC index) was applied; thelesion characteristics were described as SCO to SC4. A total of 16 crowned teeth exhibitingsecondary caries were randomly selected. The teeth were rated and grouped according totheir clinical SC grades (SC1 to SC4). After embedding in Technovit, the teeth were seriallysectioned and histologic caries scores were given for each section. Results: Fifty-twopercent of the prepared margins were in cementum/dentin. Crown margins with no carieslesions were mainly found in teeth clinically rated as SC1 and exhibiting localizeddiscolorations, whereas deep lesions were found histologically at teeth rated SC4. Thenonparametric test according to Spearman’s rank correlation coefficient (rho) confirmed ahighly significant correlation between the clinical SC index and the histologic evaluation(rho = 0.87, 95% confidence interval = 0.67 to 0.96, P < 0.01). SC1 discolorationsoverestimate caries lesions, whereas SC2 and SC4 lesions are well correlated to thepercentage of histologically evaluated caries extension into all sections of a tooth. Lesionsrated SC3 demonstrated a high variability of caries penetration into the dentin. Conclusion:The depth of discolorations and circular lesions is clinically not well predictable. Clinicaldiagnosis for localized superficial caries and deep caries lesions at the crown margincorrelated well with the histologic caries rating. Int J Prosthodont 2000;13:453–459.

aChairman, Department of Prosthodontics, School of DentalMedicine, University of Witten/Herdecke, Witten, Germany.bProfessor, Clinic for Periodontology and Fixed Prosthodontics,School of Dental Medicine, University of Berne, Switzerland.cUndergraduate Student, School of Dental Medicine, University ofWitten/Herdecke, Witten, Germany.dProfessor, Dean, and Chairman, Department of ConservativeDent i s t ry , School o f Denta l Medic ine, Univers i ty o fWitten/Herdecke, Witten, Germany.

Reprint requests: Dr Axel Zoellner, School of Dental Medicine,University of Witten/Herdecke, Alfred Herrhausen Strasse 50,58448 Witten, Germany. Fax: + 49 2302-926661. e-mail: [email protected]

This article was presented at the International Association forDental Research general session, Washington, DC, 5–9 April 2000.

Correlation Between ClinicalScoring of Secondary Caries at

Crown Margins and HistologicallyAssessed Extent of the Lesions

Axel Zoellner, Dr Med Denta

Urs Brägger, Dr Med Dent, PhDb

Vitali Fellmannc

Peter Gaengler, Dr Sc Medd

clinical studies concerning root caries,13,14 and histo-logic investigations of such lesions at the root sur-face,15–17 a new diagnostic rating index has been de-veloped.15 The aim of this study was to correlate theclinicial diagnosis of secondary caries lesions using thisindex with the features of the histologic evaluation.

Materials and Methods

Patients of the Department of Prosthetic Dentistry atthe University of Witten/Herdecke, Germany were in-cluded in this retrospective in vitro study. The patientswere 34 to 60 years old. Sixteen vital teeth with sin-gle crowns and different types of preparation were in-vestigated.

Following the oral examination of the patients,further treatment, including the extraction of prog-nostically poor abutment teeth, was planned. Thoseteeth were extracted because of periodontal reasonsor caries progression. The collection of the specimenswas carried out until each of the 4 SC grades was rep-resented by 4 teeth. The crowns had been in situ for5 to 20 years. The sample included complete veneercrowns with metal margins on 2 central incisors, 4 ca-nines, and 5 premolars. Five molars had been treatedwith complete metal crowns. Immediately after ex-traction, the teeth were stored in saline containing0.1% thymol. After extraction, all caries lesions at thecrown margin were photographed, radiographed,and classified according to the proposed SC criteria(Table 1). For scoring according to the SC index, theteeth were dried in an air stream for 5 seconds.Discolorations were evaluated visually, and cavita-tions at the margin were diagnosed by using a probe(DA 409, Aesculap). Based on the already-existingroot caries index, 4 new categories were defined forrating caries lesions at the crown margin; lesionswere ranked from 1 to 4 according to their severity.

The extracted teeth were embedded in Technovitresin (Heraeus-Kulzer) and serially sectioned to a

thickness of 100 µm (Leica 1600 diamond saw) in alongitudinal direction. The substance loss betweenthe sections was 300 µm. A total of 214 sectionswere evaluated (Leitz DMRM microscope).

Microscopic Evaluation Parameters

In the histologic analysis several findings were noted:

1. The location of the prepared margin was diag-nosed to be in enamel/dentin or cementum/dentin.

2. The integrity of the luting cement layer betweenrestoration and tooth was rated semiquantitativelyand included assessment of (1) homogeneous lut-ing cement layer, (2) inhomogeneities less than 1mm from prepared margin, and (3) inhomo-geneities extending more than 1 mm from theprepared margin.

3. The histologic evaluation of caries progression in-cluded the diagnoses (1) caries free; (2) cariesinitialis, lesion localized in enamel; (3) caries su-perficialis, early dentin lesion; (4) caries media, le-sion not extending past the orthodentin; and (5)caries profunda, deep caries lesion extendingnear to the pulp chamber.

4. The linear quantitative measurement (in mm) ofvideo-based pictures of each section (Sony KX-14P1 screen; CF11/1 camera) included (1) thevertical and horizontal extent of secondary carieslesions, (2) the extent of lesions undermining thecrown margin, and (3) the vertical and horizon-tal gap between the crown margin and the pre-pared margin.

Statistical Analysis

For the description of the homogeneity of the lutingcement layer mean values were used. The frequencyof different histologic findings of all sections of eachof the 4 clinical SC grades was rated as a percentage.For the statistical correlation of the clinical caries di-agnosis (SC grades) with the results of the histologiccaries evaluation, the diagnosis of each section wasnumerically coded as shown in Fig 1. Caries-freesections without any pathologic signs were scored0%, whereas deep caries lesions documented themost severe finding and were rated as 100%. Allother lesions were scored in increments of 25%,characterizing the increasing destruction of enameland dentin caused by caries progression. The meanvalue of all percentage scores of one tooth repre-sented the coded individual severity of tooth decay,taking into account localized as well as circular le-sions of different caries extension into the dentin. Anonparametric test—Spearman’s rank correlation

Volume 13, Number 6, 2000The International Journal of Prosthodontics 454

Zoellner et alClinical Caries Scoring and Histologic Assessment

Table 1 Definition of the Secondary Caries Index(SC) as a Modification of the Root Caries Index15

SC grade Characteristics

1 Discoloration at the crown margin because ofcarious, erosive, or abrasive reasons; no cavitation

2 Cavitation; superficial dentin softening; localized to one site; includes maximum of 25% of the margin

3 Cavitation; 2 or more sites; tendency toward circumferential lesion

4 Cavitation; deep caries lesion; likely to penetrate the pulp chamber

coefficient (rho)—was applied for the correlation ofthe clinical caries diagnosis with the coded histologiccaries diagnosis. Finally, the maximum values forthe extent of secondary caries were calculated.

Results

Forty-eight percent of the 418 evaluated crown mar-gins in ground sections were located in enamel or at

Clinical Caries Scoring and Histologic AssessmentZoellner et al


Single section

Serial sections

x x

x x xx x

xx

x

Caries freeCaries initialisCaries superficialisCaries mediaCaries profunda

Caries diagnosis

0 0Caries free (0%)Caries initialis (25%)Caries superficialis (50%)Caries media (75%)Caries profunda (100%)

Caries

Caries

Filling

Crown

Crown

Pulp

a b

c

d

e

Luting cement layer

rating section 1 (left + right) + rating section 2 (left + right) + rating section n (left + right)

2 · (number of sections)Mean value =

Fig 1 For statistical purposes the histologic findings are coded. After serial sectioning of the tooth(a), a caries diagnosis is scored (b), and noted (c) for each section. Each histologic caries diag-nosis is numerically coded according to its severity (d), and finally, a mean value representingthe individual grade of caries decay of a tooth is calculated (e).

the cementoenamel junction; 52% were in the ce-mentum. The mean vertical gap of the crown marginswas 237 ± 347 µm. The mean horizontal gap was334 ± 295 µm. In 50% of the crowned teeth ex-hibiting a discoloration next to the crown marginwithout clinical cavitation (SC1), irregularities of the luting cement layer appeared up to 1 mm fromthe prepared margin. With an increased clinicalcaries score (SC4), the destruction of the luting ce-ment layer exceeded 1 mm in 28% of the cases(Table 2).

Table 3 summarizes the results of the clinical cariesdiagnosis and the histologic evaluation of the lesion ex-tension into dentin. In 2% of the ground sections ofcrowned teeth with discolorations at the margin, ini-tial caries was diagnosed; in 3%, superficial caries wasdiagnosed (Fig 2). With a clinically scored localizedcavitation (SC2; Fig 3), superficial caries increased to29%; a localization of the lesion leading to the diag-nosis caries media was found only in 4%. In teeth re-vealing a nearly circumferential extension of the sec-ondary caries, medium lesions were documented in



Table 2 Distribution of Severity of Secondary Caries(SC Grade) According to Homogeneity of LutingCement Layer (%)

Luting SC gradecement layer 1 2 3 4

Homogeneous 40 14 23 23Inhomogeneous < 1 mm 50 80 47 49

from prepared marginInhomogeneous > 1 mm 10 6 30 28

from prepared margin

Table 3 Relationship Between Secondary Caries (SCGrade) and Histologic Findings (%)

Histologic SC grade*caries diagnosis 1 2 3 4

Caries free 95 40 46 27Caries initialis 2 27 14 21Caries superficialis 3 29 6 8Caries media 0 4 25 2Caries profunda 0 0 10 42No. of sections 59 111 121 132*Percentage of histologic caries diagnoses evaluated in all sections ineach grade.

Fig 2 Complete metal crown on maxillary left third molar, 20years in situ. Ground section reveals a superficial caries lesion ona root surface not covered by cementum. (Original magnification! 6.25.)

Fig 3 Double crown on maxillary left canine, 13 years in situ.The caries progression spreads into the dentin (caries media).The cement film exhibits no inhomogeneities. (Original magni-fication ! 16.)

25% of the ground sections; extended lesions pene-trating deep into the dentin were found in 10% of theSC3 sections (Fig 4). In clinically diagnosed deep carieslesions (SC4), caries profunda was the predominatingfeature in 42% of the ground sections (Fig 5).

The histologic findings of each section were codedaccording to their severity (0 to 100); the index rep-resented the mean value of all sections of one tooth.The increasing mean values were related to ranks; theindex value 0 was correlated to rank 1, and the high-est index value (61) was correlated to rank 14. (Theranks 1 and 9 occurred twice.) The nonparametric cor-relation of the coded histologic findings with the clin-ical diagnosis was statistically significant (rho = 0.87,95% confidence interval = 0.67 to 0.96, P < 0.01;Table 4). Figure 6 is based on the clinical SC gradesand the calculated ranks for the histologic findingscoded as mentioned above. The curve represents anearly linear correlation for SC grades 1, 2, and 4.Only secondary caries graded 3 exhibited more vari-ability of histologic findings compared to other grades.

Taking into account the extension of secondarycaries lesions beneath the crown margin, a lesion di-agnosed as SC1 may have already undermined thecrown by up to 1.0 mm horizontally and 1.3 mmvertically and still be completely hidden. With in-creased severity of the secondary caries, the lesion

undermined the crown margin by up to 2.6 mm(Table 5).

Discussion

In comparison to sound tooth surfaces, the crown mar-gin is considered a locus minoris resistentiae for newcaries lesions, with nearly unknown demineralizationand remineralization processes18 leading to failure offixed prosthodontics after 5 to 10 years because of sec-ondary caries in 5% to 15%.7,19 Both the untreated, ac-tive caries lesion and the removal and replacement ofthe crown will cause further loss of the hard tissue ofthe tooth and lead to additional degenerative changesof the endodontium.20,21 A reliable clinical evaluationand defined diagnostic protocol are prerequisites foran appropriate treatment decision including not onlynoninvasive treatment strategies but also repair of theaffected area or replacement of the crown.

Current quality criteria relate the presence of sec-ondary caries to changes in color. The depth of thesoftened dentin is mainly diagnosed by probing.12 Adiscoloration at the margin between the restorationand the tooth structure is considered to be acceptable,whereas discoloration caused by penetrating cariesalong the margin of the restorative material in a pul-pal direction or caries contiguous with the margin of



Fig 4 Ceramic-veneered crown on mandibular left first pre-molar, 20 years in situ. A circular lesion undermines the crownmargin. (Original magnification ! 16.)

Fig 5 Complete metal crown on maxillary left second molar, 9years in situ. Deep dentin caries (caries profunda) extends to-ward the pulp chamber. (Original magnification ! 6.25.)

the restoration is regarded as unacceptable.22 Probingas the only criterion is also a poor parameter to di-agnose caries in nonrestored teeth,23 and it is evenmore difficult to apply at teeth exhibiting restora-tions with different marginal gap sizes. As secondarycaries occurs not only supragingivally but also sub-gingivally,24 there is no means other than probing toidentify lesions covered by gingiva.

Radiographs may be beneficial for detecting re-current caries at the crown margin. The reliability ofradiographic diagnosis of caries is well investigatedfor unrestored teeth,25,26 but is still not well knownfor lesions affecting the crown margin. From a diag-nostic point of view, supragingivally located sec-ondary caries should be regarded separately and asits own entity. Our results document that the major-ity of crown margins was in the cementum, justify-ing the use of criteria for the evaluation of root caries.The proposed SC criteria are therefore based on agrading scheme for root caries.13,14

Secondary caries diagnosed as SC1 proved to over-estimate the presence of caries lesions. On the otherhand, undermining caries did occur in this type of le-sion. As they are a typical feature of active cementumcaries and early dentin root caries in nonrestoredroot surfaces,16 discolorations at the crown margins

may also be considered early active lesions. The con-version of active into inactive lesions is a well-knownphenomenon in coronal caries27 and root caries,28

and the beneficial role of fluorides for remineraliza-tion has been well investigated.29–31 An appropriatenoninvasive treatment should comprise not only fre-quent recall and reevaluation of the lesion charac-teristics but also the permanent bioavailability of flu-orides. It is not certain to what extent an active lesioncan remineralize. The electron microscopic featuresof arrested lesions are crystals actively synthesized bythe odontoblast processes32 and deposited in thedentin tubules, leading to dentin sclerosis. Therefore,the conversion of an active to an arrested lesionshould also depend on the integrity of the layer ofodontoblasts. But the number of odontoblastprocesses is reduced in crowned teeth, especially inthe area adjacent to the prepared margin.33

A clinically diagnosed localized cavitation at thecrown margin correlates well with moderate butnot widespread dentin caries. Removal of the carieswith repair of the affected crown margin using dif-ferent materials, like the gold foil described byKamann et al34 for this indication, may be consid-ered. Further studies need to prove acceptable long-term results of this or other filling techniques. The



Table 4 Relationship Between Clinical Caries Diagnosis (SC Grade) and CodedHistologic Index (Index)

SC1 SC2 SC3 SC4(teeth 1–4) (teeth 5–8) (teeth 9–12) (teeth 13–16)

Index Rank Index Rank Index Rank Index Rank

0 1 26 7 38 9 58 132 2 15 5 61 14 56 120 1 31 8 38 9 54 114 3 23 6 12 4 47 10

Table 5 Maximum Extent of Caries Lesions andDistance Undermining the Crown Margin (mm)

Horizontal Vertical Distanceextent extent undermined

SC1 0.7 1.0 1.3SC2 1.1 2.2 1.3SC3 3.7 5.5 2.6SC4 3.9 4.5 2.6

SC grade1

024

68

10

1214

1 1 1 2 2 2 2 3 3 3 3 4 4 4 4

Fig 6 Graph demonstrates the correlation between the sec-ondary caries (SC) grade and the ranks of scored histologic find-ings.

depth of circular lesions (SC3) is clinically not wellpredictable. The treatment indication should there-fore not be correlated to the extent but to the depthof the lesion by means of SC grades 1, 2, and 4.However, little is known about the etiology of cir-cular caries. For future epidemiologic studies it maybe beneficial to include this lesion characteristic asa separate grade. Deep caries lesions located at thecrown margin (SC4) may interfere with the integrityof the pulp.35

Within the limits of the uncertainty of the SC grades1 and 3, the suggested SC grades are an additionalclinical quality criterion for the diagnosis of sec-ondary caries in daily practice. They rely mainly onthe standardized visual estimation of caries lesions atthe crown margin with no costly technical prerequi-sites and using only a probe. Differentiation among4 severity grades may be beneficial for selecting theappropriate treatment strategy for such lesions and forfuture epidemiologic studies of dental caries locatedat the root surface or crown margin.

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correlation between clinical scoring of secondary caries at crown

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