Basic Research—Technology

Detection of Horizontal Root Fracture with Small-volumeCone-Beam Computed Tomography in the Presence andAbsence of Intracanal Metallic PostFelipe Ferreira Costa, DDS, Bruno Felipe Gaia, DDS, Otavio Shoiti Umetsubo, DDS, MS,and Marcelo Gusm~ao Paraiso Cavalcanti, DDS, MS, PhD

Abstract

Introduction: The aim of the present study was to testthe accuracy of small-volume cone-beam computedtomography (CBCT) scanning in the detection of hori-zontal root fractures and to assess the influence ofa metallic post. Methods: Forty teeth were dividedinto four groups based on the presence of metallic postsand horizontal root fracture. The teeth were examined bysmall-volume CBCT scanning at 0.2-mm voxel resolu-tion. Three observers analyzed the samples for the pres-ence of a horizontal root fracture. Sensitivity andspecificity were calculated. Results: High values foraccuracy (73%–88%) were obtained in the groupswithout a metallic post, and statistically significantdifferences were found when the group with a metallicpost has been observed (55%–70%). Intraobserveragreement also showed statistically significant differ-ences in the groups with a metallic post. Conclusions:Small-volume CBCT scanning showed high accuracy indetecting horizontal root fracture without a metallicpost. However, the presence of a metallic post signifi-cantly reduced the specificity and sensitivity of thisexamination. (J Endod 2011;37:1456–1459)

Key WordsCone-beam computed tomography scanning, diagnosis,horizontal root fracture

From University of S~ao Paulo, S~ao Paulo, S~ao Paulo, Brazil.Supported by Conselho Nacional de Desenvolvimento

Cient�ıfico e Tecnol�ogico (CNPq) National Council for Research,Research Productivity Scholarship grant No. 303847/2009-3,and Universal Research Project grant No. 472895/2009-5(M.G.P.C.) and Coordenac~ao de Aperfeicoamento de Pessoalde N�ıvel Superior (CAPES) PhD Scholarships (F.F.C. andB.F.G.) and Master Degree Scholarship (O.S.U.).

Address requests for reprints to Dr Felipe Ferreira Costa,Av Professor Lineu Prestes, 2227 Cidade Universit�aria, FOUSP,CEP 05508-900, S~ao Paulo, Brazil. E-mail address: felipecosta@usp.br0099-2399/$ - see front matter

Copyright ª 2011 American Association of Endodontists.doi:10.1016/j.joen.2011.05.040

1456 Costa et al.

Accurate diagnosis of horizontal root fractures is of fundamental importance inendodontics. However, it is still a challenge because of the restrictions of the clinical

examination. Although x-ray examination is indicated for this purpose, bidimensionaltechniques have limitations. They are caused by distortion and superimposition of otherstructures that preclude root fractures to be visualized.

Cone-beam computed tomography (CBCT) scanning was adapted for use indentistry by Arai et al (1) in 1999. This three-dimensional technique has several appli-cations in endodontics (2–7), such as the detection of root fractures (8). One of themajor advantages of CBCT scans over computed tomography (CT) scans is the signif-icantly lower effective radiation dose (9).

The restoration of teeth submitted to endodontic treatment often requires theinsertion of an intracanal post. Metallic objects can cause artifacts that seriously impairthe quality of CT images and are represented by radiopaque, radiolucent, and brighttracks that can overlap the teeth root and mimic root fractures. It can occur in bothCT and CBCT examinations, sometimes making them diagnostically unusable. This isbecause of the fact that x-rays are composed of photons with a range of energies.Because polychromatic radiation passes through an object, its energy increases inthe spectrum because low-energy photons are absorbed more frequently than high-energy photons. Therefore, the aims of the present study were to (1) test the accuracyof small-volume CBCT scanning in detecting horizontal root fracture and (2) investigatethe influence of a metallic post in the visual detection of horizontal root fracture. Thenull hypothesis was that no significant difference exists between small-volume CBCTobservations of fracture in teeth with or without metallic posts.

Materials and MethodsPreparation of Samples

Extracted single-rooted human premolar teeth (n = 40) with no root reabsorp-tion, crack, caries, or fracture were selected. The anatomic crowns of all teeth weresectioned perpendicularly to the long axis at the cementoenamel junction by usingwater-cooled diamond burs propelled by an air turbine (300,000 rpm).

For all teeth, the same operator, who was not involved in interpreting the images,performed endodontic treatment (using Gates Glidden drills sizes 2 and 3 and Nitiflexfiles; Dentsply Maillefer, Ballaigues, Switzerland) and obturation (Pulp Canal Sealer;Sybron Endo, Orange, CA). All fillings were removed from the root canals up to twothirds of their length. Subsequently, a post was modeled within each root canal.

Root fracture was then caused in the teeth (n = 20) by applying amechanical forceon their horizontal plane. A hammer was used for this purpose, and the teeth wereplaced on a soft foundation as previously described by Hassan et al (8) and Wenzeland Kirkevang (10). Both fragments were then assembled and glued without displace-ment. Teeth roots (n = 6) that were broken in more than two fragments were replacedaccording to the inclusion criteria. The entire sample was kept hydrated during theprocess except during the fracture induction.

Image AcquisitionA water-filled plastic recipient was used as the head phantom to be imaged. A CBCT

(PaX Uni3D; Gnatus/Vatech, Suwon, Korea) scan was performed for each tooth

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Basic Research—Technology

individually placed in the empty mandibular sockets of 20 human drymandibles. The limits of the imaging area consisted of a 50-mm heightand 50-mm diameter cylinder. The voxel size was 0.2 mm, and the gray-scale range of the acquired images was 16 bits. The region of interestwas positioned at the center of the field of view (FOV). Subsequently,the metallic posts were inserted into the root canals, and the teethwere scanned again following the same protocols.

Thus, 40 CBCT scans of roots with a metallic post and an equalnumber of images of roots without a metallic post (each group contain-ing 20 teeth with fracture and 20 without fracture) were obtained. Thosescans were coded and divided into four groups of teeth: without botha metal post and fracture (G1), without a metal post and with horizontalroot fracture (G2), with a metal post and without fracture (G3), andwith both a metal post and a horizontal root fracture (G4). Therefore,each of the three double-blinded observers, experienced oral andmaxillofacial radiologists who were also trained and calibrated ontomographic features of horizontal root fracture, analyzed 80 CBCTscans in each observation.

After image acquisition, data were stored in a Digital ImagingCommunication in Medicine (DICOM) file format and imported intoa specially designed open-source DICOM viewer for MacOS X AppleComputer OsiriX 3.8.1 version (Pixmeo, Geneva, Switzerland; http://www.osirix-viewer.com/). The entire volume of each sample wasanalyzed by the observers who used multiplanar reconstructed axial,coronal, and sagittal images. Subsequently, parasagittal and circumfer-ential images (slice thickness: 0.2 mm; interval between slices: 0.4 mm)were observed. They could use the visualization tools options (contrast,magnification, and window width and level) available. The sequence ofobservations was randomized by software (Randomness 1.5.2; AndrewMerenbach, Los Angeles, CA) (Fig. 1).

The interpretation time was not restricted, and the same imagewas analyzed repeatedly in a 2-week interval. This was performed

Figure 1. Circumferential CBCT images: (A) a sample with a horizontal root fractuwith a radiolucent image caused by a metallic artifact (arrow), and (C) a sample

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because the observers did not remember the previous image interpre-tation. The presence of a fracture line was diagnosed by a dichotomous(yes/no) evaluation: correct identification of a nonfractured root (truenegative [TN]) and a fracture in a fractured root (true positive [TP])and the identification of a fracture in a nonfractured root (false posi-tive [FP]) and failure to identify a fracture in a fractured root (falsenegative [FN]). Then, sensitivity = (TP/TP) and specificity = (TN/TN) + FP were calculated. Statistical analyses were performed usingthe validity and kappa tests. The k coefficients were calculated toassess the degree of intra- and interobserver agreement and scoredas weak (0.20–0.39), moderate (0.40–0.59), and relevant (0.60–0.79) (11). It allowed us to check the agreement between the tomo-graphic diagnosis and the gold standard. The level of significance wasset at a = 0.05. Data were analyzed using SPSS software (v 17.0.0;SPSS Inc, Chicago, IL).

ResultsTable 1 shows the overall TP and FP and TN and FN results for

the diagnosis of horizontal root fracture. The values for sensitivity andspecificity on the diagnosis of horizontal root fracture in teeth withoutand with metallic posts are shown in Table 2. Significant values foraccuracy (P < .05) were observed in teeth of groups 1 and 2(73%–88%) in which the metallic post was not present. However,accuracy rates were significantly reduced (P < .05) in teeth ofgroups 3 and 4 (55%–70%) in which the metallic post was present(Table 2).

The values for intraobserver agreement on the diagnosis of hori-zontal root fractures in teeth of groups G1 and G2 (without a metallicpost) varied from moderate to very high (k: 0.56–0.82); in teeth ofgroups G3 and G4 (with a metallic post), the values for intraobserveragreement varied from weak to moderate (k: 0.36–0.39) (Table 2).

re (arrow) and a metallic post, (B) a sample without a horizontal root fracturewith a horizontal root fracture (arrow) without a metallic post.

Horizontal Root Fracture in CBCT 1457

TABLE 1. The Number of True (T) and False (F) Diagnoses of Horizontal RootFractures as Identified in Each Group Performed without and with MetallicPosts

Groupsof teeth

Observer 1 Observer 2 Observer 3 Total

T F T F T F T F

G1 27 13 39 1 30 10 96 24G2 32 8 24 16 37 3 93 27G3 20 20 22 18 29 11 71 49G4 27 13 28 12 19 21 74 46

G1, group without both a metal post and a fracture; G2, group without a metal post and with a hori-

zontal root fracture; G3, group with a metal post and without a fracture; G4, group with both a metal

post and a horizontal root fracture.

Basic Research—Technology

The interobserver agreement on the diagnosis of horizontal root frac-ture in teeth of groups G1 and G2 was considered moderate to relevant(k: 0.543–0.645). However, when teeth of groups G3 and G4 wereanalyzed, the interobserver agreement was considered weak tomoderate (k: 0.157–0.453).

DiscussionSubtle fractures without separation of the adjacent segments are

sometimes not detectable using intraoral radiography because of clin-ical conditions overlapping anatomic structures and artifacts that canmimic or hide the fracture lines (12). For this reason, in thisin vitro study, the root fragments were glued in their original positionafter induced horizontal fracture. This procedure made the appearanceof the fracture lines similar to that observed in immediate post-traumacases and thus difficult to be detected. Recent studies (13, 14) haveshown that small-volume CBCT scanning has a high sensitivity and spec-ificity for the detection of root fractures. The influence of FOV duringCBCT scan is important. This selection is directly related to the voxelsize and influences spatial and contrast resolution (15). Large FOVprovides less resolution and contrast in comparison with small FOV(13, 16). This observation confirms our results that showed highaccuracy in samples without a metallic post.

However, the intraobserver agreement found in samples withoutmetallic post values was moderate to very high. This variation can beexplained by the difficulty of diagnosing this fracture, where there isno separation of fragments, even in a small-volume CBCT examination.Other studies such as those of Wenzel et al (15) and Kamburoglu et al(17) compared different voxel sizes, and they also found better resultsin diagnostic accuracy when the smallest voxel size of CBCT was used.Studies taking into account the interference of metallic objects in small-volume CBCT scans were not yet published. A metallic artifact, especially

TABLE 2. Sensitivity and Specificity Coefficients and Accuracy Rates Calculated on thMetallic Posts

First reading

Observer 1 Observer 2 Observe

SensitivityG1 e G2 0.70 0.65 0.85G3 e G4 0.65 0.65 0.40

SpecificityG1 e G2 0.60 0.95 0.90G3 e G4 0.60 0.45 0.85

Accuracy (%)G1 e G2 73 80 88G3 e G4 63 55 63

1458 Costa et al.

a ‘‘beam hardening’’ or x-ray ‘‘hardening’’ effect, is responsible for theappearance of dark bands and lines between two dense objects in radio-graphic images. High values for accuracy rates were found in the groupsin which a metallic post was not present. The values for accuracy ingroups G1 and G2 are similar to those found in the in vivo study ofYoussefzadeh et al (18), who analyzed 42 teeth of patients with a radic-ular fracture by CT scans.

The values of accuracy found in the present study were slightlylower than those found in the in vitro studies of Kamburoglu et al(12), Wenzel et al (15), and Ozer (19). A possible cause for this differ-ence is that in the present study, a water-filled plastic cylinder 150 mmin diameter� 100 mm high and the samples were immersed before theCBCT examination. This device, which was also used in other studies(20–22), was intended to cause beam attenuation, and, thus, it islikely that its use has leveled those values to the clinic levels.

The values for accuracy rates were significantly reduced in groupsG3 and G4 and exhibited statistically significant differences relative tothose in groups G1 and G2. These results are similar to those foundin the studies of Iikubo et al (14) and Youssefzadeh et al (18) in whichconventional periapical radiographs were used. In addition, the exami-nation of teeth in these groups was shown to lead to diagnoses with loweraccuracy than in other studies (10, 12, 17, 23) in which digital periapicalradiograph systems were used. This is due to artifacts caused by metallicposts that made it difficult to distinguish the ‘‘beam hardening’’ effectcaused by the metallic material inserted within the root from the linesof horizontal fracture in CBCT examination.

In addition to radiographic images, other signals (eg, a change inspace corresponding to the periodontal ligament, root-associatedbone loss, and sensitivity during mastication) that can lead to the diag-nosis of radicular fracture have to be taken into account in clinicalconditions. Draenert et al (24) stated that the OsiriX software isable to produce good-quality images of cancellous bones in theirin vivo and in vitro study. After comparison among similar software,Yamauchi et al (25) considered OsiriX a highly functional DICOMviewer, which is an important tool for preoperative planning in spinesurgery. No study was performed with this software in the analysis ofradicular fractures.

ConclusionOur study confirmed that small-volume CBCT has good accuracy in

the detection of horizontal root fracture without metallic posts (valuesranging from 73% to 88%). However, their presence significantlyreduced the accuracy (55%–63%). This research found statisticallysignificant differences between small-volume CBCT observations of frac-ture in teeth with or without metallic posts. For this reason, the nullhypothesis was rejected.

e Diagnosis of a Horizontal Root Fracture in Groups of Teeth without and with

Second reading

r 3 Observer 1 Observer 2 Observer 3

0.90 0.55 10.70 0.75 0.55

0.75 1 0.600.40 0.65 0.60

75 78 8055 70 58

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AcknowledgmentsThe authors deny any conflicts of interest related to this study.

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