5comparacion caries en orto bite y retro

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RESEARCH

A comparison of the diagnostic accuracy of bitewing, periapical,unfiltered and filtered digital panoramic images for approximal

caries detection in posterior teeth

ZZ Akarslan*,1, M Akdevelioglu1, K Gungor1 and H Erten2

1Department of Oral Diagnosis and Radiology, Gazi University School of Dentistry, Turkey; 2Department of Operative Dentistryand Endodontics, Gazi University School of Dentistry, Turkey

Objectives: The aim of this study was to investigate the diagnostic accuracy of conventionalbitewing, periapical radiographs, unfiltered and filtered digital panoramic images for theassessment of approximal carious lesions in posterior teeth.Methods: 20 patients who required bitewing, periapical and panoramic radiographsparticipated in the study. The digital panoramic images were treated with the ‘‘sharpen’’,‘‘smooth’’ and ‘‘emboss’’ filters. Three experienced observers evaluated the bitewing andperiapical radiographs, and the unfiltered and filtered digital panoramic images for thepresence or absence of approximal carious lesions according to a 5-point confidence scale.Intra- and interobserver reliability was analysed with the Cronbach alpha test and diagnosticaccuracy was evaluated using receiver operating characteristic (ROC) analysis.Results: According to the results, the intra- and interobserver agreement levels were foundto be almost perfect. The highest diagnostic accuracy was found for the bitewing, followed bythe periapical and panoramic images. Compared with the unfiltered panoramic images, thefiltered images had an almost equal or slightly higher diagnostic accuracy. The largestincrease in diagnostic accuracy was observed for those images filtered with the emboss filter.

Conclusions: The accuracy of unfiltered and filtered digital panoramic images is lower thanconventional bitewing and periapical radiographs. The filtration of the digital panoramicimages, especially the emboss filter, may have some value for the detection of approximalcarious lesions.Dentomaxillofacial Radiology (2008) 37, 458–463. doi: 10.1259/dmfr/84698143

Keywords: approximal caries, bitewing, periapical, digital panoramic

Introduction

Bitewing, periapical and panoramic radiographic ima-ging techniques are routinely used in dentistry.

Although the bitewing and periapical radiographs havebeen shown to be superior to conventional panoramicimages due to the projection geometry and imageresolution, it has been proposed that the imageresolution of panoramic radiography has increasedwith technological improvements and become compar-able with intraoral radiography for the diagnosis of dental caries.1,2

Panoramic images could be obtained with film-basedconventional techniques and direct digital imaging

systems. Compared with conventional film-based tech-niques, direct digital panoramic imaging systems havesome advantages, such as image enhancement, whichmay enhance their diagnostic value or facilitate thediagnostic interpretation.3–6

Controversial results have been reported for imageenhancement facilities for caries detection in intraoraldigital radiography. Some of the authors have reportedthat contrast enhancement and filtering increase thediagnostic accuracy for the detection of caries,7,8 whilesome have reported the contrary.9,10

Studies have evaluated the efficacy of bitewing,periapical and panoramic images in the diagnosis of

*Correspondence to: Dr Zuhre Zafersoy Akarslan, Gazi Universit esi Dis

Hekimligi Fakultesi Oral Diagnoz ve Radyoloji BD, 8 Cadde, 84 Sok, Emek,

Ankara, Turkiye; E-mail: dtzuhre@yahoo. com

Received 31 August 2007; revised 11 December 2007; accepted 11 December

2007

Dentomaxillofacial Radiology (2008) 37, 458–463’ 2008 The British Institute of Radiology

http://dmfr.birjournals.org



approximal carious lesions,1,11 but to our knowledge acomparison between conventional intraoral radio-graphic techniques, unfiltered and filtered digitalpanoramic images has not been assessed to date. Asradiographic techniques are widely used for approximalcaries diagnosis on posterior teeth and there is a rapiddevelopment and increase in adopting digital panora-mic systems, we aimed to evaluate the efficacy of digitalimages and the effect of different filters on cariesdetection in posterior teeth, and compare them withconventional film-based bitewing and periapical radio-graphic techniques.

Materials and methods

Image acquisition20 patients who had no missing posterior or canineteeth in all quadrants (except third molars), requiringposterior bitewing, periapical and panoramic radio-graphic investigation were included in this study.

The bitewing and periapical radiographs were takenwith double-packed Ektaspeed Plus films on a radio-graph machine (Trophy CCX, Vincennes, France)operating at 70 kVp and 8 mA, having 2.5 eq alumi-nium filtration and a 0.860.8 mm focal spot, accordingto the manufacturer’s exposure recommendations, withthe bisecting angle technique to obtain duplicateradiographs. The radiographs were processed in anautomatic roller transport processor machine (VelopexExtra-X Medivance Instruments Ltd, London, UK)with fresh chemicals. The digital panoramic images

were taken with the Orthoralix 9200 DDE machine(Gendex Dental Systems, Milan, Italy). The digitalpanoramic images were taken at 70–74 kVp, 4–10 mAand 12 s according to patient size in order to maintainconsistent radiographic density from the unit. Thedigital images were taken at 16-bit greyscale levels andsaved as TIFF files.

One set of the bitewing and periapical radiographswas placed in the patient’s dental charts and the secondset was used in the study. The posterior bitewing,periapical radiographs and digital panoramic imageswere taken by one trained investigator to provideconsistency in the radiographic techniques.

The digital panoramic images consisted of oneunfiltered and three filtered images with the ‘‘sharpen’’,‘‘smooth’’ and ‘‘emboss’’ filters. A total of four kinds of digital panoramic images were evaluated. The filters arepresent as both pull-down menus and as icons localizedabove the images. The use of the filter icons is easy asthey can be applied to the images using the mouse. Thesharpen filter is a high pass filter which enhancesthe edges, with an increased grainier appearance, andthe smooth filter is a low pass spatial filter providingsmooth blurring. The emboss filter is a filter providinga simulated three-dimensional (3D) image. After theapplication of each of the filters to the unfiltered image,screenshots using the Windows screen print function

were taken, imported from the clipboard to MS paint(MicrosoftH Paint v5.1; Microsoft Corporation,Redmond, WA) and saved in files corresponding tothe patient’s bitewing and periapical radiographs.

Observation sessionsThe bitewing and periapical radiographs were maskedand evaluated by each observer separately in the sameroom, on a view box under subdued lighting, indifferent viewing sessions. Approximately 2 weeksseparated the viewing sessions of both radiographs.

The digital panoramic images were displayed on a17 inch Super VGA monitor with a screen resolution of 10246768 pixels. The contrast and brightness of theimages were set to 100 and 0, respectively. Thecomputer was an Intel PentiumH having 256 MB of RAM. The operating system of the computer wasWindows XP (Microsoft, v2002) and the digitalimaging software used for the Orthoralix DDE images

was VixWin Pro (Gendex Dental Systems, v1.5). Allunfiltered and filtered digital panoramic images wereevaluated under subdued lighting conditions and theviewing distance was kept at approximately 70 cm.

All of the conventional radiographs, unfiltered andpanoramic images were evaluated by three experiencedradiologists. All observers were instructed on thedefinition of the rating scale before the examinationsessions. The observers examined the approximalsurfaces of the teeth according to a 5-point confidencescale as follows: 15 caries definitely absent; 25 cariesprobably absent; 35 equal chance of caries beingpresent or absent; 45 caries probably present; 55 car-

ies definitely present. This made it possible to performreceiver operating characteristics (ROC) analysis. Acarious lesion was defined as any amount of decalci-fication present on the approximal surface of atooth.12

The observers were blinded to each other duringevaluation sessions of the bitewing, periapical andpanoramic images. The observers did not know whichbitewing, periapical, unfiltered digital and filteredimages belonged to which patient. All images wereevaluated randomly. Approximately 2 weeks elapsedbetween the examination sessions of the bitewing,periapical, unfiltered and filtered panoramic images.

Intraobserver reliability was assessed 1 month later

with the examination of all radiographic images takenfrom ten of the patients.

2 months later, after all of the evaluation sessionswere completed, the true disease status of the teeth wasdetermined with the consensus of the three observers’simultaneous interpretation of all evaluated bitewing,periapical, unfiltered and filtered panoramic digitalimages.

Statistical analysisIntra- and interobserver agreement levels were analysedwith the calculation of Cronbach’s alpha values. Thediagnostic accuracy of each imaging modality was

Approximal caries detection and radiographyZZ Akarslan et al 4

Dentomaxillofacial Radio



analysed with the ROC analyses (a test in the diagnosticefficacy of an imaging method is compared with

chance) and asymptotic 95%

confidence intervals. Themean of the area under ROC curves (AUC) wascalculated for each observer for each imaging modality,using SPSS 10.0 statistical program.

Results

Out of 640 surfaces, 160 were excluded as they had arestoration; therefore, 480 surfaces were used in thepresent study. A total of 282 sound surfaces and 198carious surfaces were detected according to the truedisease status, determined by the consensus of the three

observers. The depth of the lesions localized on theenamel, on the outer half of the dentin and the innerhalf of the dentin were determined as 60 (30.2%), 113(56.8%) and 26 (13.1%), respectively. The frequenciesand percentages of the sound and carious surfaces areshown in Table 1.

Cronbach’s alpha values for intraobserver reliabilitywere calculated as 0.918, 0.929 and 0.957 for the first,second and third observers, respectively. TheCronbach’s alpha value for interobserver agreementwas calculated as 0.940, indicating an almost perfectagreement level.

All of the approximal surfaces of the maxillary,mandibular molar and premolar teeth which had no

restoration could be assessed with both bitewing andperiapical radiographs. Some of the surfaces could not

be assessed with the normal and filtered panoramicradiographs. A high number of the surfaces of themaxillary premolar teeth (n572) could not be evaluatedwith the panoramic radiographs due to superimpositionof the approximal surfaces. Most of the approximalsurfaces of the premolar teeth which could be evaluatedwith the panoramic images were rated to have cariouslesions. Following this dental region, 32 surfaces of themandibular premolars, 6 surfaces of the maxillarymolars and 4 surfaces of the mandibular molars couldnot be assessed. Details are shown in Table 2.

The highest mean AUCs were calculated for thebitewing, followed by periapical radiographs for alldental regions. The AUCs calculated for the normaland filtered panoramic radiographs were lower than thebitewing and periapical radiographs.

The dental regions affected the diagnostic accuracyof all imaging modalities. According to the mean of the

a b c

d e f

Figure 1 All images belong to the same site in the same patient. Arrows show the approximal caries. (a) Bitewing radiograph used in the study.(b) Periapical radiograph used in the study. (c) Cropped unfiltered panoramic image. (d) Cropped panoramic image, filtered with the ‘‘sharpen’’filter. (e) Cropped panoramic image, filtered with the ‘‘smooth’’ filter. (f) Cropped panoramic image, filtered with the ‘‘emboss’’ filter. Thebitewing and periapical radiographs were obtained by scanning conventional radiographs, and the panoramic images were captured from thecomputer screen using a digital camera

Table 1 Numbers and percentages of sound and carious surfaces

Sound n (%) Carious n (%)

Maxillary premolar 76 (63.3) 44 (36.7)Maxillary molar 69 (57.5) 51 (42.5)Mandibular premolar 68 (56.7) 52 (43.3)Mandibular molar 69 (57.5) 51 (42.5)Total 282 (58.8) 198 (41.3)

Approximal caries detection and radiography460 ZZ Akarslan et al

Dentomaxillofacial Radiology



AUCs, the highest diagnostic accuracy was calculatedfor the mandibular molar teeth with the bitewing,periapical, unfiltered and filtered digital panoramicimages. The lowest diagnostic accuracy was calculatedfor the maxillary molar region with bitewing, periapicaland panoramic images treated with the sharpen filter,and for the mandibular premolar region with theunfiltered panoramic and panoramic image treatedwith the smooth and sharpen filter. According to the

mean AUCs, the application of the sharpen and smoothfilters slightly changed the diagnostic accuracy of theunfiltered panoramic images. On the other hand, theemboss filter led to a high increase in the diagnosticaccuracy in the maxillary molar region. Details areshown in Table 3.

The highest AUCs were calculated for the bitewing,followed by periapical radiographs for all observers.The AUCs decreased for the unfiltered panoramicradiograph for all observers compared with bitewingand periapical radiographs. Other than the secondobserver, the diagnostic accuracy of the unfiltered andfiltered panoramic images was statistically significant

from chance (P ,

0.05), indicating that they were allsuitable imaging modalities for the detection of approximal carious lesions. For the second observer,the unfiltered panoramic images’ diagnostic accuracydecreased in the mandibular premolar region and thiswas not statistically significant from chance (AUC0.585; P . 0.05), indicating that it had no value forapproximal caries diagnosis in this region. With the useof the sharpen and emboss filters, the AUCs increasedsignificantly (AUC 0.647; AUC 0.628; P , 0.05) and

with the use of the smooth filter the AUCs significantlydecreased compared with the bitewing, periapical,panoramic image treated with the sharpen and embossfilters for this observer (AUC 0.605; P . 0.05). Withthe application of the emboss filter to the unfilteredpanoramic images, an increase in the AUCs wasobserved for most of the regions for all observers.

Discussion

According to the mean AUCs, the highest diagnosticaccuracy was calculated for the bitewing, followed byperiapical radiographs for all dental regions. Comparedwith the bitewing and periapical radiographs, theunfiltered and filtered digital panoramic images had alower accuracy in all dental regions. It is reported thatconventional film-based bitewing radiography is super-ior to conventional film-based panoramic radiography

for the detection of approximal carious lesions.1,13 Our

results show consistency with these results.Compared with the unfiltered digital panoramic

images, the diagnostic accuracy of the filtered imagesfor approximal carious lesion detection was almostequal to or only slightly increased in some cases.According to the mean AUCs, the highest increase wasobserved for the emboss filter. The appearance of theimages treated with the sharpen and smooth filters aresimilar to each other and the unfiltered image, but theappearance of the image treated with the emboss filteris different from the unfiltered image. We think that the

Table 3 The mean, minimum and maximum (range) of the area under ROC curves’ values and the upper and lower borders of 95% confidence

interval (CI)for each imaging modality

Region Bitewing Periapical Panoramic Panoramic sharpen Panoramic smooth Panoramic emboss

Maxillary premolar Mean 0.979 0.956 0.738 0.746 0.736 0.776Range 0.966–0.989 0.929–0.969 0.702–0.787 0.723–0.785 0.726–0.745 0.751–0.795CI 0.928–1.013 0.875–1.005 0.704–0.998 0.776–1.006 0.625–0.898 0.715–0.896

Maxillary molar Mean 0.923 0.905 0.693 0.698 0.717 0.828Range 0.901–0.946 0.885–0.929 0.608–0.843 0.620–0.839 0.646–0.815 0.790–0.886CI 0.838–0.993 0.822–0.979 0.493–0.922 0.506–0.919 0.533–0.900 0.719–0.954

Mandibular premolar Mean 0.928 0.907 0.682 0.708 0.678 0.693Range 0.889–0.949 0.858–0.943 0.585–0.760* 0.647–0.760 0.605–0.761* 0.628–0.771CI 0.833–0.990 0.871–0.992 0.466–0.861 0.533–0.861 0.487–0.862 0.511–0.870

Mandibular molar Mean 0.986 0.970 0.838 0.853 0.845 0.859Range 0.983–0.991 0.964–0.976 0.797–0.914 0.797–0.924 0.798–0.911 0.825–0.912CI 0.968–1.002 0.936–1.003 0.699–0.982 0.699–0.990 0.699–0.981 0.736–0.982

*P . 0.05, indicating not significant from chance

Table 2 Number of proximal surfaces that could and could not be examined with each imaging modality in all dental regions

Imaging modality

Maxillary premolar Maxillary molar Mandibular premolar Mandibular molar

E NE E NE E NE E NE

Bitewing 120 0 120 0 120 0 120 0Periapical 120 0 120 0 120 0 120 0

Panoramic 48 72 114 6 88 32 116 4E, number of surfaces that could be evaluated; NE, number of surfaces that could not be evaluated





higher increase in accuracy is due to the differentappearance of the image, leading to a better visualiza-tion. We could not compare our results directly as wecould not find a similar study made with digitalpanoramic imaging systems, but studies have shownthat digital contrast enhancement and filtering may

increase diagnostic accuracy for the detection of cariouslesions in digital intraoral radiography.7,8,14 In thepresent study, the observers were not permitted tochange the contrast of the images as we wanted tostandardize the experiment conditions, letting only theassessment of the effect of the filters. In further studies,the effect of contrast enhancement and filters could beevaluated.

There is no standardized terminology in digitalsoftware programs. This makes it very difficult tocompare the efficacy of different kinds of filters used indifferent studies. In the future, standardized terminol-ogy of image processing should be provided in dentistry

to allow a more accurate comparison between theresults of different studies.15

The diagnostic accuracy of digital panoramic imagesdiffered according to the examined dental region. Theaccuracy for molar teeth was higher from premolarteeth. Akkaya et al1 reported that the diagnosticaccuracy of conventional panoramic images for themolar region in approximal carious lesion detectionwas higher than that for premolar teeth. Our resultsare similar to that study. In rotational panoramicradiography it is generally accepted that markedoverlapping of the tooth crowns occurs frequently,resulting in difficulties in the assessment of approximalcarious lesions.16 This situation is particularly promi-

nent in the premolar region. In our study, nearly two-thirds of the examined maxillary premolar teeth couldnot be assessed due to overlapping of the approximalsurfaces from the digital panoramic radiograph;therefore, digital panoramic radiography is not asuitable tool for the examination of the approximalsurfaces of premolar teeth. In most of the cases, as thedepth of the lesions increased, they could be detectedin the digital panoramic images even when over-lapping was present.

The true disease status should be stated according tohistological examination in studies in which the

comparison of different methods for caries detectionis assessed. However, in some clinical studies, the styleof the clinical setting does not make it possiblefor histological evaluation.17 Although assessment of the radiographs without clinical examination is not anappropriate procedure, the consensus diagnosisobtained from experienced observers is used for thecomparison of different radiographic methods.1,18 Wetherefore used the consensus of the three experiencedobservers for the determination of the actual diseasestatus of the examined teeth. In such a study design, itwas not possible to perform histological examination of the teeth, therefore the AUCs calculated for thebitewing and periapical radiographs were over 0.90and greatly inflated due to the gold standard as theyprovided most of the evidence of the disease comparedwith the panoramic images.

The depth of the lesions is reported to have an impacton the radiographic detectability, so lesions localized on

the inner half of dentin are detected with radiographsmore often than those localized on the enamel. Theaccuracy of the detection of small approximal lesionshas been reported to be almost equal to chance.19 In thepresent study, the majority of the lesions were localizedon the inner half of dentin.

ROC analysis provides the most meaningfulapproach to compare the diagnostic performance of two or more different radiographic imaging modalitiesbecause it distinguishes between the inherent capacitiesof the observers to under- and over-read wheninterpreting imaging and is used in many studies.1,9

The analysis is made by comparing significant differ-

ences between the areas under the ROC curves thatrepresent the competing modalities.20 For these rea-sons, we used the ROC analysis for the comparison of the methods.

In conclusion, the diagnostic accuracy of the digitalpanoramic images was lower than conventional filmbased bitewing and periapical radiographs, but it didhave a value in the detection of posterior approximalcarious lesions, especially for the mandibular molarteeth. The filtration of the digital panoramic imageswith the emboss filter has some value for the detectionof approximal carious lesions in posterior teeth.

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