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A comparative analysis of periapical radiography and cone beam computerized tomography for the evaluation of endodontic obturation length
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A comparative analysis of periapical radiography and cone beam computerized tomography for the evaluation of endodontic obturation length

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  • 1. A comparative analysis of periapical radiography and cone-beam computerized tomography for the evaluation of endodontic obturation length Li Cheng, MD,a Ru Zhang, MD,a Xuan Yu, MD,a Yuanyuan Tian, MD,a Hu Wang, PhD,b Guangning Zheng, PhD,b and Tao Hu, PhD,b Chengdu, China STATE KEY LABORATORY OF ORAL DISEASE, WEST CHINA COLLEGE OF STOMATOLOGY, SICHUAN UNIVERSITYObjective. The aim of this study was to determine the consistency and inconsistency between the periapicalradiography (PR) and cone-beam computerized tomography (CBCT) in evaluating the length of root canal obturations(RCOs) in vivo.Study design. Thirty-six maxillary and mandibular first and second molars yielding 109 obturated root canals withavailable PR and CBCT images were analyzed. The inclusion criterion was that the RCO extended 0-2 mm short of theradiographic apex on PR images. Teeth having root canal calcification, apical resorption, or poor quality PR/CBCTimages were excluded. Agreement and disagreement between the 2 imaging modalities for obturation length wereanalyzed using the ␹2 test.Results. A total of 30.3% of the RCOs evaluated by PR as having adequate length were diagnosed by CBCT to haveinadequate length. Among these, 13.8% were overextended and 16.5% underextended as diagnosed by CBCT. Whenthe distance from the filling tip to the radiographic apex was 0.5 to 1 mm on the PR image, the discordance rate wasthe lowest (11.1%) in all evaluated distance groups, significantly lower than with distances of 0-0.5 mm and 1.5-2 mm(P Ͻ .01). When RCOs were diagnosed as terminating at the facial/lingual side, overextension was the main evaluationresult by CBCT in the disagreement evaluation with PR and significantly more frequent than those at the mesial/distal/central side (P Ͻ .01).Conclusions. CBCT evaluated 30.3% of the RCOs with radiographically adequate length as inadequate. When theRCOs radiographically terminated 0.5-1 mm short of the apex, the evaluation rated adequate for obturation length wascomparatively reliable. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:383-389)One of the keys to successful root canal therapy is to ingly has minimal contact with periapical tissue.13,14adequately obturate the prepared root canal space.1,2 It has However, the CDJ is merely a histologic location andbeen suggested that the apical extension of the root filling cannot be identified under current clinical circumstanc-is significant in determining the success of endodontic es.15-17 The apical constriction (minor foramen), thetherapy.3-6 Underextension may leave space for coloniza- apical portion of the root canal having the narrowesttion and proliferation of bacteria, whereas overextension diameter,18 has been advocated by most researchers asmay become a constant source of irritation, causing an the end point of treatment.19-22 However, some studiesinflammatory response in the periapical tissue.3,4,7-9 Either show that the apical constriction has several morpho-could lead to failure of the endodontic treatment.7,10 The logic variations,23 and it is often absent,24,25 especiallylevel of termination of root canal instrumentation after instrumentation. It is generally agreed that instru-and obturation is one of the controversies of end- mentation and obturation should be limited to withinodontic therapy. Many researchers hold that root the root canal system.3,16 Thus, the apical (major) fo-canal treatment should terminate at the cementoden- ramen, the most apical opening of the canal, is alsotinal junction (CDJ),11,12 which often coincides with considered a useful landmark for terminating the root canal obturation (RCO).26 Periapical radiography (PR)the pulp and periodontal tissue junction and accord- is the most commonly used method in clinical practice to evaluate the quality of RCO. However, neither thea Graduate Student. apical constriction nor the apical foramen is discernibleb Professor. on the PR. The only measuring point that can be viewedReceived for publication Dec. 5, 2010; returned for revision Apr. 11, on PRs is the anatomic (radiographic) apex.27,282011; accepted for publication Apr. 14, 2011.1079-2104/$ - see front matter Generally, RCO is considered to be clinically satis-© 2011 Mosby, Inc. All rights reserved. factory and designated to be adequate if the tip of thedoi:10.1016/j.tripleo.2011.04.025 filling material is 0-2 mm short of the radiographic apex 383
  • 2. OOOOE384 Cheng et al. September 2011in postoperative radiographs.29,30 Nevertheless, it is Table I. Number of teeth and root canals for differentwell known that the anatomic location of the apical tooth typesforamen varies between individuals.18,31,32 A predeter- Jaw Tooth type No. of teeth No. of root canalsmined distance range hardly reflects the true individual Maxilla First molar 8 27anatomy. In reality, an obturation classified as satisfac- Second molar 4 10tory by radiographic determination might have filling Mandible First molar 20 62materials beyond or short of the apical foramen because Second molar 4 10 Total 36 109of individual anatomic variation. On the other hand,because the PR is a 2-dimensional (2D) representationof a 3-dimensional (3D) structure, radiographic estima-tion of RCO is challenging for the difficulty of distin-guishing superimposed features. the filling material was 0-2 mm short of the radio- Recently, cone-beam computerized tomography graphic apex on the PR image. Exclusion criteria were:(CBCT) was introduced to endodontics as a noninva- 1) evidence of root canal calcification, apical resorp-sive tool for disease diagnosis and morphologic evalu- tion, immature root apices, root perforation or fracture;ation.33,34 It can produce 3D images of dentoalveolar and 2) poor-quality PR or CBCT images. Approval byregions at a lower radiation dose and cost and at a the Ethics Committee of the West China College ofhigher resolution than conventional computerized to- Stomatology and an informed consent from each pa-mography.35,36 Many studies have demonstrated its ac- tient were obtained before the investigation.curacy in diagnosing and measuring. Simon et al.37 There were 14 women and 22 men, with a mean ageindicated that CBCT might provide a more accurate of 35 years (range 17-60 years) in this study. Wediagnosis than biopsy when evaluating large periapical analyzed 36 teeth representing 109 root canals. Thelesions (e.g., granuloma vs. cyst). Michetti et al.38 distribution of teeth types is presented in Table I.registered a strong to very strong correlation betweenthe data related to areas and Feret diameters acquired Radiographic techniquesby using CBCT and histology. Blattner et al.39 reported PR images were taken by an experienced operatorthat there was no significant difference in the ability of using a paralleling technique with a film holder (XCP;CBCT scanning to detect the second mesiobuccal canal Rinn, Elgin, IL). Silicone rubber impression materialcompared with the criterion standard of clinical sec- (Exafine putty type; GC, Tokyo, Japan) was used totioning (P Ͼ .5). Accordingly, as a 3D imaging tech- ensure that a reproducible radiograph could be taken.nique, CBCT is expected to be valuable in accurately All radiographs were taken with a dental x-ray machineevaluating the length of endodontic obturations. (Gendex Expert; DC, Des Plaines, IL) operating at 65 The purpose of the present study was to determine the kV and 7 mA and an exposure time of 0.25 seconds forconsistency and inconsistency between PR and CBCT in maxillary and 0.20 seconds for mandibular teeth. Den-the evaluation of endodontic obturation length in vivo. tal intraoral E-Speed films (Kodak; Carestream Health, Rochester, NY) were used. All films were uniformlyMATERIALS AND METHODS processed in an automatic processor (Periomat Plus;Patients Dürr Dental, Bietigheim-Bissingen, Germany) with Thirty-six consecutive patients who had recently un- fresh Kodak processing solutions for 5 minutes at 24°Cdergone root canal therapy for their maxillary or man- according to the manufacturer’s instructions.dibular first or second molars in the Department of The CBCT images were taken by an experiencedOperative Dentistry and Endodontics at the West China operator using a 3D Accuitomo Tomograph (Morita).College of Stomatology, Sichuan University, Chengdu, Operating parameters were 80 kV and 5.0 mA andChina, between October 2009 and April 2010 were exposure time 17.5 seconds. The voxel size wasenrolled in this investigation. The Root ZX (J. Morita, 0.125 mm and the slice thickness 1.0 mm. ScansTokyo, Japan), an electronic apex locator, was used were made according to the manufacturer’s recom-according to the manufacturer’s instructions in con- mended protocol.junction with PRs to determine the working length. Theroot canals were then filled to the adjusted working Evaluation of imageslength with gutta-percha cones and AH Plus (Dentsply The PR films were viewed with ϫ3.6 magnifica-DeTrey, Konstanz, Germany) using a lateral condensa- tion on a standard viewing box in a dark room.tion technique. Inclusion criteria were that: 1) the teeth Distances between the tip of the RCOs and the ra-involved had been examined with both PR and CBCT diographic apex for each root canal were measuredafter completing endodontic therapy; and 2) the tip of with the use of a digital caliper. The E-like markers
  • 3. OOOOEVolume 112, Number 3 Cheng et al. 385Fig. 1. A-C, Periapical radiographic images showing root canal obturations (RCOs) as satisfactory (arrows). A1-C3, Cone-beamcomputerized tomographic (CBCT) images in (1) axial, (2) coronal, (3) sagittal planes. A1-A3, CBCT shows RCO asoverextended (arrows). B1-B3, CBCT shows RCO as underextended (arrows). C1-C3, CBCT shows RCO as flush (arrows).on the films were used to calibrate the measurement canal space between the root end of the RCO and theof the PR images to compensate for elongation and apex in Ͼ1 of the image planes; or C) flush, definedforeshortening. When the distances were 0-2 mm, the as the root end of RCO terminating at the apex, withRCOs were evaluated as adequate and the subjects neither overextension nor underextension. The flushwere enrolled in the study. According to the numeric RCOs were evaluated as adequate and the overex-values of the distances, the RCOs were classified into tended and underextended RCOs as inadequate. In4 groups: 1) 0-0.5 mm; 2) 0.5-1 mm; 3) 1-1.5 mm; or addition, according to the location of the point where4) 1.5-2 mm. the obturation terminated at the apex, the position of The CBCT images were analyzed with the built-in the RCO could be divided into 1 of 3 classes: 1)software (I-Dixel, one-volume viewer 1.5.0) using a central; 2) mesial or distal; or 3) buccal or lingual.Dell Precision T5400 workstation (Dell, Round Evaluations were carried out by 3 observers (2Rock, TX) and a 32-inch Dell LCD screen with a endodontists and 1 radiologist) under the same view-resolution of 1,280 ϫ 1,024 pixels in a dark room. ing conditions. Before starting, the observers wereContrast and brightness of images was adjusted with trained using sample PR and CBCT images of RCOsthe image-processing tool of the software to ensure with various apical extensions. The investigated im-optimal visualization. For 3D images, tomographicsections in 3 planes (axial, coronal, and sagittal) ages were assessed in the following sequence: ses-were presented, and the observers were able to align sion 1: all PR images; session 2: all CBCT images (inthe 3 planes at any point by clicking a location of random order); and session 3: 18 PR (presenting 54interest on any of the planes.40 This allowed the RCOs) and 18 CBCT images (presenting 55 RCOs)location of the root end of the canal space and randomly picked out and reevaluated to assess in-obturation to be determined in the 3 planes. From the traobserver agreement. There was a Ն2-week inter-CBCT images, we classified each RCO into 1 of 3 val between sessions. In each assessment, the observ-categories (Fig. 1): A) overextension, defined as the ers evaluated the images independently and thenvisible extension of the root end of RCO beyond the discussed their findings to reach consensus. The ob-root apex surface in Ͼ1 of the image planes; B) servation time and number of times for measuringunderextension, defined as the visible presence of were not restricted.