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  • 1. Clinical ResearchA New Periapical Index Based on Cone BeamComputed TomographyCarlos Estrela, DDS, MSc, PhD,* Mike Reis Bueno, DDS, MSc,†Bruno Correa Azevedo, DDS, MSc,‡ José Ribamar Azevedo, DDS,§ andJesus Djalma Pécora, DDS, MSc, PhDʈAbstractThe purpose of this study was to evaluate a newperiapical index based on cone beam computed tomog-raphy (CBCT) for identification of apical periodontitis P eriapical radiography is an essential resource in endodontic diagnosis, because it offers important evidence on the progression, regression, and persistence of apical periodontitis (AP) (1, 2). It is known that periapical radiolucencies might not be visible(AP). The periapical index proposed in this study (CBCT- radiographically, although they exist clinically (3–5). Moreover, radiographs are 2-di-PAI) was developed on the basis of criteria established mensional representations of 3-dimensional structures, and certain clinical and bio-from measurements corresponding to periapical radi- logic features might not be reflected in radiographic changes. Clinical and radiologicolucency interpreted on CBCT scans. Radiolucent im- criteria are frequently used to assess the status of endodontic treatment and itsages suggestive of periapical lesions were measured by correlation with AP (6 –14), but morphologic variations, surrounding bone den-using the working tools of Planimp software on CBCT sity, x-ray angulations, and radiographic contrast can influence radiographic in-scans in 3 dimensions: buccopalatal, mesiodistal, and terpretation (12, 13).diagonal. The CBCTPAI was determined by the largest With the great technological advances of recent years, new imaging modalitieslesion extension. A 6-point (0 –5) scoring system was have been added to dental radiology as viable diagnostic tools, namely digital radiog-used with 2 additional variables, expansion of cortical raphy, densitometry methods, cone beam computed tomography (CBCT), magneticbone and destruction of cortical bone. A total of 1014 resonance imaging, ultrasound, nuclear techniques (13, 15–23), providing detailedimages (periapical radiographs and CBCT scans) origi- high-resolution images of oral structures and permitting early detection of bone lesions.nally taken from 596 patients were evaluated by 3 CBCT has been used for several clinical and investigational purposes in endodon-observers by using the CBCTPAI criteria. AP was iden- tics (15, 16, 18 –20). According to a recent study (16), the specific endodontic appli-tified in 39.5% and 60.9% of cases by radiography and cations of cone beam volumetric tomography (CBVT) are being identified as this tech-CBCT, respectively (P Ͻ .01). The CBCTPAI offers an nology becomes more prevalent, but its potential indications include diagnosis ofaccurate diagnostic method for use with high-resolu- pathosis from endodontic and nonendodontic origins, assessment of root canal mor-tion images, which can reduce the incidence of false- phology, evaluation of root and alveolar fractures, analysis of external and internal rootnegative diagnosis, minimize observer interference, and resorption and invasive cervical resorption, and presurgical planning in root-end sur-increase the reliability of epidemiologic studies, espe- geries. Scarfe et al. (21) have stated that important innovations of imaging systemscially those referring to AP prevalence and severity. involve the change from analog to digital imaging and advances in imaging theory and(J Endod 2008;34:1325–1331) volume-acquisition data, allowing detailed 3-dimensional imaging. Investigations (22, 23) have demonstrated that a cyst could be distinguished from periapical granulomasKey Words by CBCT because it shows a marked difference in density between the content of the cystApical periodontitis, cone beam computed tomography, cavity and granulomatous tissue, thus favoring a noninvasive diagnosis. At this point indiagnostic imaging, endodontic diagnosis, radiography time, scientific consensus has been reached to the fact that AP is correctly detected by histologic analysis (24). Previous studies (1, 8, 10) have referred to the periapical index (PAI) as a scoring system for radiographic assessment of AP. The PAI represents an ordinal scale of 5 From the *Federal University of Goiás, Goiânia, GO, Brazil; scores ranging from no disease to severe periodontitis with exacerbating features and is† University of Cuiabá, Cuiabá, MT, Brazil; ‡Department ofDental Diagnostic Science, University of Texas, San Antonio, based on reference radiographs with confirmed histologic diagnosis originally pub-Texas; §Dental and Radiological Institute of Brasília, Brasília, lished by Brynolf (8). Ørstavik et al. (1) applied the PAI to both clinical trials andDF, Brazil; and ʈUniversity of São Paulo, Ribeirão Preto, SP, epidemiologic surveys and might be transformed into success and failure criteria byBrazil. defining cutoff points on the scale for a dichotomous outcome assessment (13). Address requests for reprints to Prof Dr Carlos Estrela, Centrode Ensino e Pesquisa Odontológica do Brazil (CEPOBRAS), Rua Given the limitations of conventional radiography for detection of AP and theC-245, Quadra 546, Lote 9, Jardim América, CEP: 74.290-200, availability of new emerging 3-dimensional imaging modalities, the development of newGoiânia, GO, Brazil. E-mail address: estrela3@terra.com.br. periapical indices seems to be a necessity. The purpose of this study was to evaluate a0099-2399/$0 - see front matter new PAI based on CBCT for identification of AP. Copyright © 2008 American Association of Endodontists.doi:10.1016/j.joen.2008.08.013 Material and Methods Cone Beam Computed Tomography Periapical Index The Cone Beam Computed Tomography Periapical Index (CBCTPAI) proposed in this study was developed on the basis of criteria established from measurements cor- responding to periapical radiolucency interpreted on CBCT scans. The sizes of radiolu-JOE — Volume 34, Number 11, November 2008 Computed Tomography Periapical Index 1325
  • 2. Clinical ResearchFigure 1. Clinical case of mandibular molar showing the axial (A), sagittal (B), and coronal (C) planes. The CBCTPAI was determined by the largest extension of thelesion.TABLE 1. Cone Beam Computed Tomography Periapical Index Scores cent images suggestive of periapical lesions were delimited and mea- sured by using the working tools of Planimp software (CDT Computing, Quantitative Bone Alterations in Mineral Score Cuiabá, MT, Brazil) on CBCT scans in 3 dimensions: buccopalatal, me- Structures siodistal, and diagonal (Fig. 1). The CBCTPAI was determined by the 0 Intact periapical bone structures 1 Diameter of periapical radiolucency Ͼ 0.5–1 mm 2 Diameter of periapical radiolucency Ͼ 1–2 mm 3 Diameter of periapical radiolucency Ͼ 2–4 mm 4 Diameter of periapical radiolucency Ͼ 4–8 mm 5 Diameter of periapical radiolucency Ͼ 8 mm Score (n) Expansion of periapical cortical bone ϩ E* Score (n) Destruction of periapical cortical bone ϩ D**The variables E (expansion of cortical bone) and D (destruction of cortical bone) were added to eachscore, if either of these conditions was detected in the CBCT analysis.Figure 2. Schematic representation of molars CBCTPAI. Figure 3. Schematic representation of premolars CBCTPAI.1326 Estrela et al. JOE — Volume 34, Number 11, November 2008
  • 3. Clinical Research Imaging Methods and Evaluation The periapical radiographs were taken with Max S-1 x-ray equip- ment (J. Morita Mfg Corp, Kyoto, Japan) with 0.8 mm ϫ 0.8 mm tube focal spot and with Kodak Insight film-E (Eastman Kodak Co, Rochester, NY) according to the parallel radiographic technique. All films were processed in an automatic processor and developed by using standard- ized methods. CBCT images were obtained with 3D Accuitomo XYZ Slice View Tomograph (model MCT-1; J. Morita Mfg Corp) voxel size of 0.125 ϫ 0.125 ϫ 0.125 mm, 12 or 8 bits. Images were examined by using specific software (3D Tomo X version 1.0.51) in a PC workstation running under Microsoft Windows XP professional SP-1 (Microsoft Corp, Redmond, WA). Three calibrated blinded observers evaluated all digital images by using the CBCTPAI criteria described in Table 1. The level of interob- server agreement was assessed by kappa statistics in 10% of the sample (25). Data were analyzed statistically by the ␹2 test to determine signif- icant differences among the imaging methods for detection of AP. Sig- nificance level was set at ␣ ϭ 1%. Results Table 2 shows the prevalence of AP identified by periapical radi- ography and CBCT by using the CBCTPAI. AP was detected in 39.5% and 60.9% of cases by periapical radiography and CBCT, respectively (P ϽFigure 4. Schematic representation of canines CBCTPAI.largest extension of the lesion. A 6-point (0 –5) scoring system wasused. In addition, considering that CBCT provides 3-dimensional im-ages, with depth being added as a new plane of analysis in relation to2-dimensional radiography, 2 variables were included in the scoringsystem as appropriate, expansion of cortical bone (E) and destructionof cortical bone (D) (Table 1 and Figs. 2–7).Patients One thousand fourteen images (periapical radiographs and CBCTscans) originally taken from 596 patients (241 men and 355 women;mean age, 54 Ϯ 17 years) between May 2004 and August 2006 wereselected from the Dental and Radiological Institute of Brasília (IORB,Brasília, DF, Brazil) database. All patients had 1 or more teeth withhistory of endodontic treatment. Some of the teeth in question radio-graphically displayed an AP. The involved teeth were mandibular molars(n ϭ 126), maxillary molars (n ϭ 203), mandibular premolars (n ϭ183), maxillary premolars (n ϭ 226), mandibular canines (n ϭ 11),maxillary canines (n ϭ 99), mandibular incisors (n ϭ 13), and max-illary incisors (n ϭ 153). The study design was independently reviewed and approved by theInstitutional Ethics in Research Committee. Figure 5. Schematic representation of incisors CBCTPAI.JOE — Volume 34, Number 11, November 2008 Computed Tomography Periapical Index 1327
  • 4. Clinical ResearchFigure 6. Clinical cases of maxillary incisors CBCTPAI showing all scores used and 2 additional variables (expansion of cortical bone and destruction of corticalbone)..01). Table 3 presents the results of the diagnostic imaging tests by using When both diagnostic methods were analyzed by all observers, theyCBCTPAI kappa values for interobserver agreement, considering the agreed that the CBCT images provided clinically relevant additional in-CBCTPAI scores ranged from 0.86 – 0.96 for periapical radiographs formation not found in the periapical films. The capacity of computedand CBCT scans. Figs. 2–7 show the schematic representation and clin- tomography to evaluate a region of interest in 3 dimensions might ben-ical cases of groups of mandibular and maxillary teeth corresponding to efit both novice and experienced clinicians alike. The advantages in-CBCTPAI. clude increased accuracy, higher resolution, scan-time reduction, and lower radiation dose (16). Discussion The use of conventional radiography for detection of AP should be CBCT was more accurate than periapical radiography for AP done with care because of the great possibility of false-negative diagno-diagnosis. AP was identified in nearly 40% of the cases by using sis. The benefits of using CBCT in endodontics refer to its high accuracyperiapical radiographs and in almost 61% of the cases by using in detecting periapical lesions even in its earliest stages and aiding inCBCT scans (Table 2). differential diagnosis as a noninvasive technique (5). The accuracy of CBCT scans compared with periapical radio- Simon et al. (23) compared the differential diagnosis of largegraphic images is in accordance with the findings of previous studies (5, periapical lesions (granuloma versus cyst) with traditional biopsy by16, 18, 19, 21–23, 26). Lofthag-Hansen et al. (26) compared intraoral using CBCT. Seventeen large periapical radiolucencies (equal to orperiapical radiography and a 3-dimensional imaging system (3D Accui- greater than 1 ϫ 1 cm) were scanned to determine densities, and atomo) for the diagnosis of apical pathology in 36 patients (46 teeth). preoperative CBCT diagnosis was made. The lesions were then removed1328 Estrela et al. JOE — Volume 34, Number 11, November 2008
  • 5. Clinical ResearchFigure 7. Clinical cases of maxillary molars CBCTPAI showing all scores used and 2 additional variables (expansion of cortical bone and destruction of corticalbone).surgically and sent for histopathologic examination. In 13 of 17 cases, The CBCTPAI proposed hereby has some advantages for clinicalthe biopsy report and CBCT diagnosis coincided. In 4 of 17 cases, the applications. CBCTPAI scores are calculated by analysis of the lesion inCBCT read cyst, whereas the oral pathologist’s diagnosis was chronic 3 dimensions, with CT slices being obtained in mesiodistal, buccopala-AP. These results suggest that CBCT might provide a faster method to tal, and diagonal directions. The measurement of lesion depth contrib-differentially diagnose a solid from a fluid-filled lesion or cavity, without utes significantly to the diagnosis and consequently to improve caseinvasive surgery and/or waiting a long time to see whether nonsurgical prognosis. The addition of the variables expansion of cortical bone andtherapy is effective. destruction of cortical bone to CBCTPAI scoring system permits the analysis of 2 possible sequels to AP that might be missed by periapical radiography. Detection of these conditions will alter the diagnostic hypothesis and theTABLE 2. AP Prevalence in Endodontically Treated Teeth as Determined byPeriapical Radiography and CBCT, by Using CBCTPAI (n ϭ 1014) treatment plan. The goal of this new index is therefore to offer a method based on the interpretation of high-resolution images that can provide a Periapical P more precise measurement of AP extension, minimizing observer interfer- CBCT Radiography Value* ence and increasing the reliability of research results. Presence of AP 401 (39.5%) 618 (60.9%) Ͻ.001 The PAI as indicated by Ørstavik et al. (1) ranges from health to Absence of AP 613 (60.5%) 396 (39.1%) severe periodontitis on the basis of the interpretation of 2-dimensionalAP, apical periodontitis; CBCT, cone beam computed tomography. radiographic images, whereas CBCTPAI scores have been established*␹2 test. according to the interpretation of 3-dimensional CBCT scans. These 2 peri-JOE — Volume 34, Number 11, November 2008 Computed Tomography Periapical Index 1329
  • 6. Clinical ResearchTABLE 3. Results of Imaging Diagnostic Tests with CBCTPAI, on the Basis of Criteria Established from Measurements Corresponding to Periapical Radiolucency(Ͼ0.5–1 mm to Ͼ8 mm), with 2 Additional Variables, Expansion of Cortical Bone (E) and Destruction of Cortical Bone (D) (n ϭ 1014) CBCT n 0 1 2 E D 3 E D 4 E D 5 E D Total Periapical radiography 0 386 53 83 16 1 42 21 3 45 25 4 4 3 1 613 1 10 26 44 6 — 10 3 — 4 1 2 1 — — 95 2 — 3 51 14 1 58 33 5 44 22 8 4 2 1 160 E — — — — — — — — — — — — — — — D — — — — — — — — — — — — — — — 3 — — — — — 22 14 2 48 32 7 17 8 7 87 E — — — — — — — — — — — — — — — D — — — — — — — — — — — — — — — 4 — — 1 — — — — — 33 17 8 13 6 6 47 E — — — — — — — — — — — — — — — D — — — — — — — — — — — — — — — 5 — — — — — — — — — — — 12 6 5 12 E — — — — — — — — — — — — — — — D — — — — — — — — — — — — — — — Total 1014CBCTPAI, Cone Beam Computed Tomography Periapical Index.apical indices thus have different scoring systems as a result of the charac- 3. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental le-teristics of each target image (conventional periapical radiograph or CBCT sions in bone I. J Am Dent Assoc 1961;62:152– 60. 4. Bender IB, Seltzer S. Roentgenographic and direct observation of experimental le-scan). The scope of the present study is to evaluate a new PAI that is based sions in bone II. J Am Dent Assoc 1961;62:708 –16.on an imaging modality that allows detection of lesions that are not visible 5. Estrela C, Bueno MR, Leles CR, Azevedo BC, Azevedo JR. Accuracy of cone beamradiographically. Considering the clinical history, the relation between computed tomography, panoramic and periapical radiographic for the detection ofhealth and disease in CBCTPAI can be begun by stage 1, without detection of apical periodontitis. J Endod 2008;34:273–9.cortical bone expansion or destruction of the cortical bone. 6. Strindberg LZ. The dependence of the results of pulp therapy on certain factors: an The limitations of periapical radiography to identify AP support the analytical study based on radiographic and clinical follow-up examinations. Actaneed to review the epidemiologic studies conducted in different popu- Odontol Scand 1956;14:1–175. 7. Grossman LI, Sheprd LI, Pearson LA. Roentgenologic and clinical evaluation of end-lations worldwide. A considerable discrepancy among the imaging odontically treated teeth. Oral Surg Oral Med Oral Pathol 1964;17:368 –74.methods used to diagnose AP, especially with a new baseline value, 8. Brynolf I. A histologic and roentgenologic study of the periapical region of humancertainly might reduce the influence of radiographic interpretation and upper incisors. Odontol Revy 1967;18:1–176.the possibility of false-negative diagnosis. 9. Goldman M, Pearson AH, Darzenta N. Reliability of radiographic interpretations. Oral In the present study, the kappa values for CBCTPAI scores ranged Surg Oral Med Oral Pathol 1974;38:287–93.from 0.86 – 0.96 for periapical radiographs and CBCT scans, which 10. Reit C, Grøndahl HG. Application of statistical decision theory to radiographic diag- nosis of endodontically treated teeth. Scand J Dent Res 1983;9:213– 8.indicate that a very good interobserver agreement was reached. High 11. Halse A, Molven O. A strategy for the diagnosis of periapical pathosis. J Endodkappa values (0.80 – 0.95 range) have also been observed in previous 1986;12:534 – 8.studies that examined periapical radiographs (27, 28). 12. Molven O, Halse A, Fristad I. Long-term reliability and observer comparisons in the In spite of the dental imaging technique, care should be taken to radiographic diagnosis of periapical disease. Int Endod J 2002;35:142–7.avoid misinterpretation. The presence of intracanal metallic posts, for 13. Huumonen S, Ørstavik D. Radiological aspects of apical periodontitis. Endod Topicsexample, might lead to equivocated interpretations as a result of artifact 2002;1:3–25. 14. Estrela C, Leles CR, Hollanda ACB, Moura MS, Pécora JD. Prevalence and risk factorsformation in CBCT images. Metallic objects can be present in either the of apical periodontitis in endodontically treated teeth in a selected population oftooth of interest or an adjacent one and hinder the analysis of CBCT Brazilian adults. Braz Dent J 2008;19:34 –9.images (26), although in current days the influence of this artifact has 15. Arai Y, Tammisalo E, Iwai K, Hashimoto K, Shinoda K. Development of a compactbeen reduced. This artifact has been found to be closely related to the computed tomographic apparatus for dental use. Dent Maxillofac Radiol 1999;28:type of tissue or object (ie, computed tomography value) and the x-ray 245– 8.energy applied (29). 16. Cotton TP, Geisler TM, Holden DT, Schwartz SA, Schindler WG. Endodontic applica- tions of cone beam volumetric tomography. J Endod 2007;33:1121–32. Under the tested conditions and within the limitations of this study, 17. Nair MK, Nair UP. Digital and advanced imaging in endodontics: a review. J Endodit might be concluded that AP detection was considerably higher with 2007;33:1– 6.CBCT than with periapical radiography. The PAI proposed in this study 18. Nielsen RB, Alyassin AM, Peters DD, Carnes DL, Lancaster J. Microcomputed tomography:(CBCTPAI) offers an accurate diagnostic method for use with high- an advanced system for detailed endodontic research. J Endod 1995;21:561– 8.resolution images, which can reduce the incidence of false-negative 19. Patel S, Dawood A, Pitt Ford T, Whaites E. The potential applications of cone beamdiagnosis, minimize observer interference, and increase the reliability computed tomography in the management of endodontic problems. Int Endod J 2007;40:818 – 823.of epidemiologic studies, especially those referring to AP prevalence 20. Yajima A, Otonari-Yamamoto M, Sano T, et al. Cone beam CT (CB Throne) applied toand severity. dentomaxillofacial region. Bull Tokyo Dent Coll 2006;47:133– 41. 21. Scarfe WC, Farman AG, Sukovic P. Clinical applications of cone-beam computed References tomograghy in dental practice. J Can Dent Assoc 2007;72:75– 80. 1. Ørstavik D, Kerekes K, Eriksen HM. The periapical index: a scoring system for 22. Trope M, Pettigrew J, Petras J, Barnett F, Tronstad L. Differentiation of radicular radiographic assessment of apical periodontitis. Endod Dent Traumatol 1986;2: cyst and granulomas using computerized tomography. Endod Dent Traumatol 20 – 4. 1989;5:69 –72. 2. Nair PNR, Sjögren U, Figdor D, Sundqvist G. Persistent periapical radiolucencies of 23. Simon JHS, Enciso R, Malfaz JM, Rogers R, Bailey-Perry M, Patel A. Differential root-filled human teeth, failed endodontic treatments, and periapical scars. 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  • 7. Clinical Research24. Laux M, Abbott PV, Pajarola G, Nair PNR. Apical inflammatory root resorption: a 27. Nicopoulou-Karayianni K, Bragger U, Patrikiou A, Stassinakis A, Lang NP. Image correlative radiographic and histological assessment. Int Endod J 2000;33: processing for enhanced observer agreement in the evaluation of periapical bone 483–93. changes. Int Endod J 2002;35:615–22.25. Landis JR, Koch GG. The measurement of observer agreement for categorical data. 28. Weiger R, Hitzler S, Hermle G, Löst C. Periapical status, quality of root canal fillings Biometrics 1977;33:159 –74. and estimated endodontic treatment needs in an urban German population. Endod26. Lofthag-Hansen S, Hummonen S, Gröndahl K, Gröndahl H-G. Limited cone-beam CT Dent Traumatol 1997;13:69 –74. and intraoral radiography for the diagnosis of periapical pathology. Oral Surg Oral 29. Katsumata A, Hirukawa A, Noujeim M, et al. Image artifact in dental cone-beam CT. Med Oral Pathol Oral Radiol Endod 2007;103:114 –9. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:652–7.JOE — Volume 34, Number 11, November 2008 Computed Tomography Periapical Index 1331