A new periapical index based on cone beam computed tomography

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New Periapical Index Based on Cone Beamomputed Tomography

arlos Estrela, DDS, MSc, PhD,* Mike Reis Bueno, DDS, MSc,†

runo Correa Azevedo, DDS, MSc,‡ José Ribamar Azevedo, DDS,§ andesus Djalma Pécora, DDS, MSc, PhD�

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bstracthe purpose of this study was to evaluate a neweriapical index based on cone beam computed tomog-aphy (CBCT) for identification of apical periodontitisAP). The periapical index proposed in this study (CBCT-AI) was developed on the basis of criteria establishedrom measurements corresponding to periapical radi-lucency interpreted on CBCT scans. Radiolucent im-ges suggestive of periapical lesions were measured bysing the working tools of Planimp software on CBCTcans in 3 dimensions: buccopalatal, mesiodistal, andiagonal. The CBCTPAI was determined by the largest

esion extension. A 6-point (0 –5) scoring system wassed with 2 additional variables, expansion of corticalone and destruction of cortical bone. A total of 1014

mages (periapical radiographs and CBCT scans) origi-ally taken from 596 patients were evaluated by 3bservers by using the CBCTPAI criteria. AP was iden-ified in 39.5% and 60.9% of cases by radiography andBCT, respectively (P � .01). The CBCTPAI offers anccurate diagnostic method for use with high-resolu-ion images, which can reduce the incidence of false-egative diagnosis, minimize observer interference, and

ncrease the reliability of epidemiologic studies, espe-ially those referring to AP prevalence and severity.J Endod 2008;34:1325–1331)

ey Wordspical periodontitis, cone beam computed tomography,iagnostic imaging, endodontic diagnosis, radiography

From the *Federal University of Goiás, Goiânia, GO, Brazil;University of Cuiabá, Cuiabá, MT, Brazil; ‡Department ofental Diagnostic Science, University of Texas, San Antonio,exas; §Dental and Radiological Institute of Brasília, Brasília,F, Brazil; and �University of São Paulo, Ribeirão Preto, SP,razil.

Address requests for reprints to Prof Dr Carlos Estrela, Centroe Ensino e Pesquisa Odontológica do Brazil (CEPOBRAS), Rua-245, Quadra 546, Lote 9, Jardim América, CEP: 74.290-200,oiânia, GO, Brazil. E-mail address: [email protected]/$0 - see front matter

Copyright © 2008 American Association of Endodontists.oi:10.1016/j.joen.2008.08.013

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OE — Volume 34, Number 11, November 2008

eriapical radiography is an essential resource in endodontic diagnosis, because itoffers important evidence on the progression, regression, and persistence of apical

eriodontitis (AP) (1, 2). It is known that periapical radiolucencies might not be visibleadiographically, although they exist clinically (3–5). Moreover, radiographs are 2-di-ensional representations of 3-dimensional structures, and certain clinical and bio-

ogic features might not be reflected in radiographic changes. Clinical and radiologicriteria are frequently used to assess the status of endodontic treatment and itsorrelation with AP (6 –14), but morphologic variations, surrounding bone den-ity, x-ray angulations, and radiographic contrast can influence radiographic in-erpretation (12, 13).

With the great technological advances of recent years, new imaging modalitiesave been added to dental radiology as viable diagnostic tools, namely digital radiog-aphy, densitometry methods, cone beam computed tomography (CBCT), magneticesonance imaging, ultrasound, nuclear techniques (13, 15–23), providing detailedigh-resolution images of oral structures and permitting early detection of bone lesions.

CBCT has been used for several clinical and investigational purposes in endodon-ics (15, 16, 18 –20). According to a recent study (16), the specific endodontic appli-ations of cone beam volumetric tomography (CBVT) are being identified as this tech-ology becomes more prevalent, but its potential indications include diagnosis ofathosis from endodontic and nonendodontic origins, assessment of root canal mor-hology, evaluation of root and alveolar fractures, analysis of external and internal rootesorption and invasive cervical resorption, and presurgical planning in root-end sur-eries. Scarfe et al. (21) have stated that important innovations of imaging systemsnvolve the change from analog to digital imaging and advances in imaging theory andolume-acquisition data, allowing detailed 3-dimensional imaging. Investigations (22,3) have demonstrated that a cyst could be distinguished from periapical granulomasy CBCT because it shows a marked difference in density between the content of the cystavity and granulomatous tissue, thus favoring a noninvasive diagnosis. At this point inime, scientific consensus has been reached to the fact that AP is correctly detected byistologic analysis (24).

Previous studies (1, 8, 10) have referred to the periapical index (PAI) as a scoringystem for radiographic assessment of AP. The PAI represents an ordinal scale of 5cores ranging from no disease to severe periodontitis with exacerbating features and isased on reference radiographs with confirmed histologic diagnosis originally pub-

ished by Brynolf (8). Ørstavik et al. (1) applied the PAI to both clinical trials andpidemiologic surveys and might be transformed into success and failure criteria byefining cutoff points on the scale for a dichotomous outcome assessment (13).

Given the limitations of conventional radiography for detection of AP and thevailability of new emerging 3-dimensional imaging modalities, the development of neweriapical indices seems to be a necessity. The purpose of this study was to evaluate aew PAI based on CBCT for identification of AP.

Material and Methodsone Beam Computed Tomography Periapical Index

The Cone Beam Computed Tomography Periapical Index (CBCTPAI) proposed inhis study was developed on the basis of criteria established from measurements cor-
esponding to periapical radiolucency interpreted on CBCT scans. The sizes of radiolu-
Computed Tomography Periapical Index 1325

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Figure 2. Schematic representation of molars CBCTPAI. F

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score, if either of these conditions was detected in the CBCT analysis.

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ent images suggestive of periapical lesions were delimited and mea-ured by using the working tools of Planimp software (CDT Computing,uiabá, MT, Brazil) on CBCT scans in 3 dimensions: buccopalatal, me-iodistal, and diagonal (Fig. 1). The CBCTPAI was determined by the

ronal (C) planes. The CBCTPAI was determined by the largest extension of the
igure 1. Clinical case of mandibular molar showing the axial (A), sagittal (B), and co
ABLE 1. Cone Beam Computed Tomography Periapical Index Scores

Score Quantitative Bone Alterations in MineralStructures

0 Intact periapical bone structures1 Diameter of periapical radiolucency � 0.5–1 mm2 Diameter of periapical radiolucency � 1–2 mm3 Diameter of periapical radiolucency � 2–4 mm4 Diameter of periapical radiolucency � 4–8 mm5 Diameter of periapical radiolucency � 8 mm

Score (n)� E*

Expansion of periapical cortical bone

Score (n)� D*

Destruction of periapical cortical bone

The variables E (expansion of cortical bone) and D (destruction of cortical bone) were added to each

igure 3. Schematic representation of premolars CBCTPAI.

JOE — Volume 34, Number 11, November 2008

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argest extension of the lesion. A 6-point (0 –5) scoring system wassed. In addition, considering that CBCT provides 3-dimensional im-ges, with depth being added as a new plane of analysis in relation to-dimensional radiography, 2 variables were included in the scoringystem as appropriate, expansion of cortical bone (E) and destructionf cortical bone (D) (Table 1 and Figs. 2–7).

atientsOne thousand fourteen images (periapical radiographs and CBCT

cans) originally taken from 596 patients (241 men and 355 women;ean age, 54 � 17 years) between May 2004 and August 2006 were

elected from the Dental and Radiological Institute of Brasília (IORB,rasília, DF, Brazil) database. All patients had 1 or more teeth withistory of endodontic treatment. Some of the teeth in question radio-raphically displayed an AP. The involved teeth were mandibular molarsn � 126), maxillary molars (n � 203), mandibular premolars (n �83), maxillary premolars (n � 226), mandibular canines (n � 11),axillary canines (n � 99), mandibular incisors (n � 13), and max-

llary incisors (n � 153).The study design was independently reviewed and approved by the

igure 4. Schematic representation of canines CBCTPAI.

nstitutional Ethics in Research Committee. F


maging Methods and EvaluationThe periapical radiographs were taken with Max S-1 x-ray equip-

ent (J. Morita Mfg Corp, Kyoto, Japan) with 0.8 mm � 0.8 mm tubeocal spot and with Kodak Insight film-E (Eastman Kodak Co, Rochester,Y) according to the parallel radiographic technique. All films wererocessed in an automatic processor and developed by using standard-

zed methods. CBCT images were obtained with 3D Accuitomo XYZ Sliceiew Tomograph (model MCT-1; J. Morita Mfg Corp) voxel size of.125 � 0.125 � 0.125 mm, 12 or 8 bits. Images were examined bysing specific software (3D Tomo X version 1.0.51) in a PC workstationunning under Microsoft Windows XP professional SP-1 (Microsoftorp, Redmond, WA).

Three calibrated blinded observers evaluated all digital images bysing the CBCTPAI criteria described in Table 1. The level of interob-erver agreement was assessed by kappa statistics in 10% of the sample25). Data were analyzed statistically by the �2 test to determine signif-cant differences among the imaging methods for detection of AP. Sig-ificance level was set at � � 1%.

ResultsTable 2 shows the prevalence of AP identified by periapical radi-

graphy and CBCT by using the CBCTPAI. AP was detected in 39.5% and0.9% of cases by periapical radiography and CBCT, respectively (P �

igure 5. Schematic representation of incisors CBCTPAI.


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01). Table 3 presents the results of the diagnostic imaging tests by usingBCTPAI kappa values for interobserver agreement, considering theBCTPAI scores ranged from 0.86 – 0.96 for periapical radiographsnd CBCT scans. Figs. 2–7 show the schematic representation and clin-cal cases of groups of mandibular and maxillary teeth corresponding toBCTPAI.

DiscussionCBCT was more accurate than periapical radiography for AP

iagnosis. AP was identified in nearly 40% of the cases by usingeriapical radiographs and in almost 61% of the cases by usingBCT scans (Table 2).

The accuracy of CBCT scans compared with periapical radio-raphic images is in accordance with the findings of previous studies (5,6, 18, 19, 21–23, 26). Lofthag-Hansen et al. (26) compared intraoraleriapical radiography and a 3-dimensional imaging system (3D Accui-

igure 6. Clinical cases of maxillary incisors CBCTPAI showing all scores usedone).

omo) for the diagnosis of apical pathology in 36 patients (46 teeth). p

328 Estrela et al.

hen both diagnostic methods were analyzed by all observers, theygreed that the CBCT images provided clinically relevant additional in-ormation not found in the periapical films. The capacity of computedomography to evaluate a region of interest in 3 dimensions might ben-fit both novice and experienced clinicians alike. The advantages in-lude increased accuracy, higher resolution, scan-time reduction, andower radiation dose (16).

The use of conventional radiography for detection of AP should beone with care because of the great possibility of false-negative diagno-is. The benefits of using CBCT in endodontics refer to its high accuracyn detecting periapical lesions even in its earliest stages and aiding inifferential diagnosis as a noninvasive technique (5).

Simon et al. (23) compared the differential diagnosis of largeeriapical lesions (granuloma versus cyst) with traditional biopsy bysing CBCT. Seventeen large periapical radiolucencies (equal to orreater than 1 � 1 cm) were scanned to determine densities, and a

additional variables (expansion of cortical bone and destruction of cortical
and 2
reoperative CBCT diagnosis was made. The lesions were then removed


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urgically and sent for histopathologic examination. In 13 of 17 cases,he biopsy report and CBCT diagnosis coincided. In 4 of 17 cases, theBCT read cyst, whereas the oral pathologist’s diagnosis was chronicP. These results suggest that CBCT might provide a faster method toifferentially diagnose a solid from a fluid-filled lesion or cavity, withoutnvasive surgery and/or waiting a long time to see whether nonsurgicalherapy is effective.

ABLE 2. AP Prevalence in Endodontically Treated Teeth as Determined byeriapical Radiography and CBCT, by Using CBCTPAI (n � 1014)

PeriapicalRadiography CBCT P

Value*

Presence of AP 401 (39.5%) 618 (60.9%) �.001Absence of AP 613 (60.5%) 396 (39.1%)

P, apical periodontitis; CBCT, cone beam computed tomography.

igure 7. Clinical cases of maxillary molars CBCTPAI showing all scores usedone).

a�2 test.


The CBCTPAI proposed hereby has some advantages for clinicalpplications. CBCTPAI scores are calculated by analysis of the lesion indimensions, with CT slices being obtained in mesiodistal, buccopala-

al, and diagonal directions. The measurement of lesion depth contrib-tes significantly to the diagnosis and consequently to improve caserognosis. The addition of the variables expansion of cortical bone andestruction of cortical bone to CBCTPAI scoring system permits the analysisf 2 possible sequels to AP that might be missed by periapical radiography.etection of these conditions will alter the diagnostic hypothesis and the

reatment plan. The goal of this new index is therefore to offer a methodased on the interpretation of high-resolution images that can provide aore precise measurement of AP extension, minimizing observer interfer-

nce and increasing the reliability of research results.The PAI as indicated by Ørstavik et al. (1) ranges from health to

evere periodontitis on the basis of the interpretation of 2-dimensionaladiographic images, whereas CBCTPAI scores have been established

additional variables (expansion of cortical bone and destruction of cortical
and 2
ccording to the interpretation of 3-dimensional CBCT scans. These 2 peri-


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pical indices thus have different scoring systems as a result of the charac-eristics of each target image (conventional periapical radiograph or CBCTcan). The scope of the present study is to evaluate a new PAI that is basedn an imaging modality that allows detection of lesions that are not visibleadiographically. Considering the clinical history, the relation betweenealth and disease in CBCTPAI can be begun by stage 1, without detection ofortical bone expansion or destruction of the cortical bone.

The limitations of periapical radiography to identify AP support theeed to review the epidemiologic studies conducted in different popu-ations worldwide. A considerable discrepancy among the imaging

ethods used to diagnose AP, especially with a new baseline value,ertainly might reduce the influence of radiographic interpretation andhe possibility of false-negative diagnosis.

In the present study, the kappa values for CBCTPAI scores rangedrom 0.86 – 0.96 for periapical radiographs and CBCT scans, whichndicate that a very good interobserver agreement was reached. Highappa values (0.80 – 0.95 range) have also been observed in previoustudies that examined periapical radiographs (27, 28).

In spite of the dental imaging technique, care should be taken tovoid misinterpretation. The presence of intracanal metallic posts, forxample, might lead to equivocated interpretations as a result of artifactormation in CBCT images. Metallic objects can be present in either theooth of interest or an adjacent one and hinder the analysis of CBCTmages (26), although in current days the influence of this artifact haseen reduced. This artifact has been found to be closely related to theype of tissue or object (ie, computed tomography value) and the x-raynergy applied (29).

Under the tested conditions and within the limitations of this study,t might be concluded that AP detection was considerably higher withBCT than with periapical radiography. The PAI proposed in this studyCBCTPAI) offers an accurate diagnostic method for use with high-esolution images, which can reduce the incidence of false-negativeiagnosis, minimize observer interference, and increase the reliabilityf epidemiologic studies, especially those referring to AP prevalencend severity.

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n 0 1 2 E

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A new periapical index based on cone beam computed tomography