Clinical ResearchComparative Analysis of Accessory Mesial CanalIdentification in Mandibular First Molarsby Using Four Diffe...
Clinical ResearchFigure 1. Acrylic template containing 9 holes for CBCT examination (A). Platform of the tomography appara...
Clinical Research                                                                            TABLE 1. Comparison of Result...
Clinical ResearchTABLE 3. Identification Frequency of Possible AMCs Identified and Instrumented in the Mesial Root of Lower ...
Clinical ResearchFigure 4. Possible locations of AMC: close to ML (A); at the center, between MB and ML canals (B); and cl...
Clinical Research 3. Martinez-Berna A, Badanelli P. Mandibular first molars with six root canals. J Endod    19. Vande Voor...
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Comparative analysis of accessory mesial canal identification in mandibular first molars by using four different diagnostic methods


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Comparative analysis of accessory mesial canal identification in mandibular first molars by using four different diagnostic methods

  1. 1. Clinical ResearchComparative Analysis of Accessory Mesial CanalIdentification in Mandibular First Molarsby Using Four Different Diagnostic MethodsK^nia Maria Pereira Soares de Toubes, MS, Maria Ilma de Souza C^rtes, PhD, e oMaria Alice de Abreu Valadares, MS, Luciana Cardoso Fonseca, PhD, Eduardo Nunes, PhD,and Frank Ferreira Silveira, PhDAbstractIntroduction: The objective of the present in vitrostudy was to compare 4 diagnostic methods to identifyaccessory mesial canals (AMCs) in lower first molars. T he morphology of the lower first molar has been assessed by using many different diagnostic methods, with very variable results (1–17). This tooth presents a high rate of intercanals and anastomosis, mainly in the apical 5 mm, which presentsMethods: Forty-four lower first molars were selected a clinical challenge in terms of cleaning and disinfection (16, 17). There isfor assessment with cone-beam computed tomography increasing interest in evaluating methods for identifying the accessory mesial canal(CBCT), digital radiography (DR), clinical inspection (AMC) of the lower first molar. Various studies have reported that the prevalence of(CI), and dental operating microscope (DOM). Initially, AMCs ranges from 1%–18% (1, 4, 6, 12, 14). However, some methods were unableaxial images were obtained by using CBCT, and radio- to identify the presence of such canals (10). It has been hypothesized that the spacegraphs were taken in ortho, mesial, and distal angula- between the mesiobuccal (MB) and mesiolingual (ML) canals is an isthmus that cantions. The images were assessed by 2 independent be cleaned and shaped (8, 12).groups of examiners, and all of the results obtained re- Clinical inspection (CI) and digital radiography (DR) are the traditional methodsmained undisclosed until the end of the experiment. used to identify root canals (18). However, the efficacy of CI is directly dependent on theSubsequently, root canal access was prepared, and the examiner’s knowledge and skills (19, 20), whereas radiography is limited by technicalmesial subpulpal groove was located by using sharp factors such as contrast and angulation (18). Each method has its own unique limita-endodontic explorers. The roots were examined with tions, which contribute to a relatively high rate of unidentified canals, particularly whenDOM, and all identified canals were negotiated and in- canal location and number are atypical (19).strumented by using a ProTaper Rotary System. The A higher-magnification view of the straight segment of the root canal by usingresults were tabulated and statistically analyzed by either magnifying glasses or an operating microscope (DOM) particularly enhancesnonparametric McNemar tests. Results: Twelve AMCs the ability to detect canals that could not normally be observed by CI alone. This has(27.0%) were identified by CBCT, and 58.0% were in- increased the number of published case reports showing unsuccessful endodonticstrumented. No AMCs were visualized in any DR exam- treatment because AMCs are not always visible without the aid of magnificationined. Fifteen potential AMCs (34%) were identified by (1–3, 5, 8).CI, but only 47.0% were confirmed after instrumenta- Cone-beam computed tomography (CBCT) presents a new technologicaltion. Thirteen AMCs (30.0%) were identified by DOM, approach that is noninvasive and overcomes many of the disadvantages of CI, DR,and 84.0% could be negotiated and instrumented. and DOM because the operator can visualize the morphologic characteristics of theConclusions: There were statistically significant differ- sample in 3-dimensional slices without destroying the specimen (21–24). Despiteences between the 4 types of assessments for AMC the limitations imposed by biological, technical, and economic factors, CBCT hasidentification. There was good agreement between been implemented in dental practice and is suggested as an auxiliary means ofDOM and CBCT, whereas DR and CI were not as precise identifying and diagnosing canals and either of the other 2 diagnostic methods. (J Endod Relevant comparative studies that use CBCT for the identification of AMCs in the2012;38:436–441) literature are scarce (25). One study compared CBCT with DR in determining the number of canals in anterior and premolar teeth (26). By using CBCT, Baratto et alKey Words (27) evaluated the presence of MB2 canals in upper molars, and Wang et al (14) eval-Accessory canals, cone beam computed tomography, uated the morphology of the mandibular first molar in the Chinese population. An i-CATdental operating microscope, mandibular first molars device was used to identify the MB2 canal in the upper molars, and the results compared with periapical radiography and transverse clinical sectioning (28). Carvalho and Zuolo (6) determined the number of canals in lower molars with the naked eye and compared From the Department of Dentistry, Pontificial Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Address requests for reprints to Dr Maria Ilma de Souza C^rtes, Pontif Universidade Catlica de Minas Gerais, Departamento de Odontologia, Rua Goncalves Dias, o ıcia o ¸142 –Sala 502, Bairro Funcionrios, Belo Horizonte, MG, Brasil, CEP 30140-090. E-mail address: a0099-2399/$ - see front matter Copyright ª 2012 American Association of Endodontists.doi:10.1016/j.joen.2011.12.035436 Soares de Toubes et al. JOE — Volume 38, Number 4, April 2012
  2. 2. Clinical ResearchFigure 1. Acrylic template containing 9 holes for CBCT examination (A). Platform of the tomography apparatus with template positioned on it (B). Tomographyapparatus (C). Axial image obtained from CBCT with the XoranCat software (D).this with the number determined by using DOM, but they did not use DR molars, as well as in determining their frequency, location, apicalor CBCT. Yoshida et al (7) compared a visual method, magnifying end, and amenability to negotiation and instrumentation.glasses, and DOM in identifying canals in a sample of 260 teeth butdid not report the presence of AMCs. The effectiveness of DOM andmagnifying glasses was recently compared for the identification of Materials and MethodsAMCs in lower molars, including the frequency, location, and amena- Tooth Selection and Preparationbility to exploration (12). However, CBCT was not used, and instrumen- A set of 125 extracted mandibular first molars was collectedtation was not performed. randomly from the Dental Department human tooth bank and then The objective of this in vitro study was to compare CBCT with CI, exposed to digital periapical radiography in the buccolingual direction.DR, and DOM methods in the identification of AMCs in lower first Patient age, gender, and race were not considered. Only teeth withFigure 2. Acrylic template for DR in the mesial (A), ortho (B), and distal (C) positions; teeth positioned on the template (D–F) and digital radiograph (G–I).JOE — Volume 38, Number 4, April 2012 Comparative Analysis of AMC Identification in Mandibular First Molars 437
  3. 3. Clinical Research TABLE 1. Comparison of Results of Different Diagnostic Methods, Obtained by McNemar Test Diagnostic methods Value of diagnostic methods P .05 CI Â CBCT 8.25 P .010 CI Â DOM 7.5 P .010Figure 3. Image of some sections of a tooth scanned from crown to apex, CBCT Â DOM 9.25 P .010identifying dentin interposition between the canals (arrows).complete root formation and 2 canals in the mesial root were included.Teeth that had been subjected to previous endodontic treatment or dis- highly skilled endodontist and 1 imaging expert who worked together.played aberrant curve anatomy, calcified canals, or internal root The groups of examiners were trained and calibrated in a pilot study byresorption were excluded. After careful examination, 44 first molars using images of first molars designed specifically for this study and bywere selected for experiments and stored in 0.01% thymol solution until using identical methodologies. The evaluation criteria for the identifica-use. tion of the AMCs through DR and CBCT were established during the pilot study. An interexaminer kappa test was performed to evaluate the coherence between the 2 examiner pairs.CBCT Five plates of methylmethacrylate monomer (UNIGEL, S~o Paulo, aBrazil), measuring 7.5 cm in width, 7.5 cm in length, and 3.0 cm in CBCT Image Readingheight, were prepared by drilling nine 1.5-cm diameter holes CBCT examination was conducted in a dark room, and the ideal(Fig. 1A). The holes were filled with Adsil silicone (Vigodente, Rio de image contrast had a 12-bit grayscale resolution for a maximum timeJaneiro, Brazil), and the teeth were individually inserted into the sili- of 10 minutes per tooth. The samples were coded, and the codescone at the level of the cementoenamel junction, which had been previ- were kept undisclosed so that the examiners could not identify theously delimited to ensure the stabilization and parallelism of each samples. Images were read in the axial section from the pulp chamberspecimen as well as standardization of the CBCT examination. After floor to serve as a sample reference point for the examiners. In the anal-the material was set, the acrylic template was positioned on the platform ysis of the tomographic sections, the presence of 3 canals was taken intoof the tomography apparatus (i-CAT; Imaging Sciences International, account only when the 3 radiolucent orifices were observed to be inde-Hatfield, PA) (Fig. 1B), which was operated at a field of view of pendent and presented a radiopaque structure, regardless of their loca-6 cm, voxel size of 0.2 mm, and exposure time of 40 seconds, to digitize tion along the root (Fig. 3).the teeth from crown to apex. Image acquisition and analysis were per-formed by using XoranCat software, version 3.0.34 (Xoran Technolo-gies, Ann Arbor, MI) (Fig. 1C). The number of canals in the mesial DR Image Readingroot of the lower first molar was determined by navigation of the axial During the radiographic evaluation, the same groups of examinerstomographic sections (Fig. 1D). observed the DR, following the same methodologic protocol and nondisclosure of the specimen codes. The examiners were instructedDR to consider one canal present only if 75% of the radiolucent structure could be visualized from the pulp chamber floor to the apex. The images Three plates of methylmethacrylate monomer (UNIGEL) were were treated with different filters to improve canal identification. Bothmade for the standardization of the radiographic view in the same angu- groups of examiners used the same filters.lations. These plates measured exactly the size of the digital radio- Data collected during the examinations (CBCT and DR) were tabu-graphic film, with angles of –30 for mesioangulation (Fig. 2A), lated and sent for statistical analysis, while remaining undisclosed to the0 for orthoangulation (Fig. 2B), and +30 for distoangulation 2 groups of examiners and the investigator.(Fig. 2C), respectively. One template of Adsil silicone was made foreach pair of teeth and standardized in accordance with the innermeasurements of the methacrylate plate. The teeth were positioned CIon this template, and a digital film was placed below it. The set (meth- To simulate CI, each sample was positioned and individuallyacrylate plate, digital film, silicone template, and teeth) was exposed at attached to a bench vise (Somar, Joinville, Brazil) for stabilization.–30 (Fig. 2D), 0 (Fig. 2E), and +30 (Fig. 2F) horizontal angula- Conventional endodontic access cavities were completed by nakedtions, and the x-ray unit was at 65 kVp and 8 mA for 0.44 seconds eye and under abundant irrigation by using a 5.2% sodium hypochlorite(Dabi Atlante, S~o Paulo, Brazil). The resulting images were digitized a solution (Lenza Farmac^utica, Belo Horizonte, Brazil) to optimize visi- eby using the Digora Optime System (Soredex, Helsinki, Finland) in bility. The mesial subpulpal groove was explored with sharp endodonticthe mesial (Fig. 2G), ortho (Fig. 2H), and distal (Fig. 2I) positions. explorers (DG 16; Hu-Friedy, Chicago, IL) under illumination from a reflector (Dabi Atlante). When the tip of the explorer became attachedImage Reading to any groove suggesting a canal, it was considered a possible AMC. The tomographic and radiographic images were evaluated by 2 Otherwise, the exploration was finished so that the sample could remainpairs of examiners working independently. Each pair consisted of 1 intact for the next examination. The data are reported.TABLE 2. Number of AMCs Identified by Each Diagnostic Method Agreement between diagnostic methods No. of teeth No. of identified AMCs 1 11 CI, n = 6 CBCT, n = 2 DOM, n = 3 2 7 CI Â CBCT, n = 2 CI Â DOM, n = 2 DOM Â CBCT, n = 3 3 5 CI Â CBCT Â DOM, n = 5438 Soares de Toubes et al. JOE — Volume 38, Number 4, April 2012
  4. 4. Clinical ResearchTABLE 3. Identification Frequency of Possible AMCs Identified and Instrumented in the Mesial Root of Lower First Molars, Including Frequency by DiagnosticMethod Diagnostic No. of possible Relative frequency of Confidence No. of instrumented Relative frequency of method AMCs identified (n) AMC identification (%) interval AMCs (n) instrumented AMCs (%) CBCT 12 27 13.5–40.9 7 58 DR 0 0 0 0 0 CI 15 34 19.5–48.7 7 47 DOM 13 30 15.5–43.6 11 85DOM The result of the interexaminer kappa test for the identification of A DOM (DOM M900; DF Vasconcelos, S~o Paulo, Brazil) at 13Â a AMCs by CBCT was 0.82 (P .001).magnification was used to investigate the mesial subpulpal groove ac- As shown in Table 3, 12 AMCs (27%) were identified by CBCT, andcording to the same criteria used in the CI. The data obtained were re- 58% (n = 7) of these were instrumented. It was not possible to identifycorded. Photographs were taken with a digital camera (NIKON D60; any AMCs by DR. Fifteen possible AMCs (34%) were identified by CI, butNikon, Tokyo, Japan) mounted on the optical microscope by means only 47% (n = 7) were instrumented. On examination with DOM, 13of an adapter (DF Vasconcelos), which also assisted in the visual docu- AMC canals (30%) were identified, and 85% (n = 11) of these canalsmentation. Subsequently, the excess dentin along the subpulpal groove were fully instrumented.was selectively removed by using an ultrasonic tip (TU17; Triniti, S~oa The AMCs identified were located in the isthmus between the MBPaulo, Brazil) that had been mounted on an ENAC ultrasonic device and ML canals, close to the MB (46%), at the center (23%), or close to(Osada, Inc, Tokyo, Japan) at low strength. After isthmus preparation, the ML (31%) (Table 4, Fig. 4). Of the 13 AMCs identified by DOM, 7the mesial root was mapped again, and the results were recorded in canals (54%) were connected to the MB (Fig. 4D), 5 (38%) were con-a table. The AMCs identified were passively emptied according to the nected to the ML (Fig. 4E), and 1 (8%) ended in an independentcrown-down technique until #10 K-file (Dentsply Maillefer, Ballaigues, foramen (Fig. 4F), as shown in Figure 4G.Switzerland) reached patency. A new radiographic examination wasperformed at ortho, mesial, and distal angulations, with the teeth re- Discussionmaining in their respective templates and the files positioned in their Although the identification of AMCs is a technical challengerespective canals. This procedure allowed for the determination of because of the difficulty in locating and visualizing these features withpreparation length and the assessment of the apical end of all identified the naked eye, CI without magnification is still widely used. Adequatecanals. The specimens were instrumented with ProTaper rotary files coronary access and the use of DOM are both crucial to overcoming(Dentsply Maillefer) according to the technique recommended by the this challenge (6, 7, 12, 29, 30). In addition, the use of ultrasonicmanufacturer until the F1 file reached as far apically as possible. tips to clean the cervical isthmus is very important to enable the A kappa test was performed to assess the agreement of DR and identification of the majority of AMCs (3, 5, 6, 12).CBCT results between the 2 groups of examiners, revealing 95% overall Notably, although Corcoran et al (20) reported that the ability toagreement for both studies. Agreement between diagnostic methods was locate root canals depends on the operator’s skills and experience, thealso determined by using kappa as an estimator. The nonparametric present study showed that CI for the identification of AMCs was less reli-McNemar test (Stata, version 11.1; Stata Corporation, College Station, able than DOM or CBCT, even when performed by an experiencedTX) was used to statistically determine the best method of AMC identi- professional. In the present study, many grooves suggestive of AMCfication. were found to be simple spaces in the isthmus after instrumentation. Friedman (31) concluded that the reading of radiographic images can vary because of differences in angulation and contrast as well as the Results examiner’s interpretation. DR was used with the expectation that it Table 1 summarizes the results of the McNemar test comparing the would overcome these inconsistencies and biased radiographic inter-4 proposed diagnostic methods. There was a statistically significant pretations without compromising the results (32, 33), but 2 teams ofdifference between the diagnostic methods used (P .01). experienced endodontists and dentists specializing in imaging did not As shown in Table 2, AMCs were identified by only one diagnostic identify any AMCs by using DR, with the kappa test showing 100%method in 11 specimens (25%). Matching results from 2 and 3 diag- inter-rater agreement. Therefore, it can be concluded from this studynostic methods were observed in 7 (16%) and 5 (11%) specimens, that DR was not an efficient method for the identification of AMCs,respectively. In 21 teeth (48%), it was not possible to identify AMCs even when radiographs were taken at different angulations (34).by any diagnostic method. However, although it cannot be used to identify AMCs, the value of The interexaminer agreement between the 2 groups was 100% for DR should not be underestimated.DR examinations. None of the examiners identified AMCs by using DR, In the present study, CBCT allowed the visualization of thedespite varying the angulations. morphology of the mesial root of the lower first molars, with theTABLE 4. Frequency Distribution of AMC Locations from DOM and Apical Terminus from DR After Instrumentation Variable Frequency Relative frequency Variable Frequency Relative frequency AMC location (N) (%) AMC apical terminus (N) (%) Closer to MB 6 46 Cervical 7 54 Closer to ML 4 31 Mid-apical 5 38 Between MB and ML 3 23 Apical 1 8 Total 13 100 Total 13 100JOE — Volume 38, Number 4, April 2012 Comparative Analysis of AMC Identification in Mandibular First Molars 439
  5. 5. Clinical ResearchFigure 4. Possible locations of AMC: close to ML (A); at the center, between MB and ML canals (B); and close to MB (C). Digital radiographs showing the end of AMCclose to MB (D) and ML (E) canals as well as at an independent foramen (F). Beginning and apical end of AMC in 3 independent foramina (arrows) (G and H).2-mm-thick sections observed from the coronary third to the apex; was that it allowed the morphologic visualization of the canal trajectory,this provided a high-resolution image without compromising the mainly in the mid and apical thirds of the roots, whereas visualizationpreservation of the specimens and was considered the gold standard with DOM was limited to the straight portion of the canal. However,in this study (28). The inter-rater concordance (kappa values) Nance et al (35) stated that not all canals can be identified withbetween the examiners when using CBCT was 0.82. This high kappa CBCT, and they also indicated that CBCT should be used as an auxiliaryvalue shows that the examiners were well-trained in reading the method in identification, rather than as a replacement for careful clin-images, thus eliminating individual experience as an interference ical examination.factor. The AMC was considered a canal when it was the one entirely According to Mortman and Ahn (8) and Karapinar-Kazandag et alsurrounded by dentin (17). It was identified in 12 specimens (12), this finding suggests that the AMC is not actually a canal but an(27.0%) by using CBCT, greater than the number reported by Nav- isthmus with sufficient space to be explored, cleaned, and shaped. Byarro et al (9) (14.81%), probably because of methodologic differ- using CBCT images, it was possible to prove this assertion; it was notences. When comparing CBCT with other diagnostic methods (CI possible to identify any AMC that was totally independent from the DR  DOM), the results from CBCT were most similar to those cervical to apical thirds in any of the specimens. In one specimen,from DOM. the AMC end was totally independent, but it presented in the foramen In the present study, of the 13 canals identified by DOM, 7 (54%) located inside an isthmus between the MB and ML root, rather thanwere connected to either the MB or ML before the mid-third of the root, in the apex.whereas 5 other canals were connected between the mid-third and the Under the conditions of the present study, there were significantapex. One specimen had an AMC with an independent foramen, a rare differences between the 4 methods for the identification of AMCs infinding in the literature (3, 6). These findings corroborate studies by the mesial roots of lower first molars. DOM alone could have identifiedPomeranz et al (1) and Karapinar-Kazandag et al (12). Furthermore, all instrumentable AMCs. CBCT was the next most effective method, andCarvalho and Zuolo (8) and Karapinar-Kazandag et al reported an the other methods were less valuable.increased number of AMCs identified in their studies (7.1% and18%, respectively). However, in this study, AMCs were identified in Acknowledgments30% of the specimens, probably because all canals identified were in- The authors deny any conflicts of interest related to this study.strumented, regardless of their location. In fact, 4 AMCs were foundduring the specimen cleaning and shaping procedures in the presentstudy. This finding confirms that instrumentation is an important step References 1. Pomeranz H, Eidelman D, Goldberg M. Treatment considerations of the middlein identifying AMCs. mesial canal of mandibular first and second molars. J Endod 1981;7:565–8. The results of this study show that CBCT had a lower AMC identi- 2. Fabra-Campos H. Unusual root anatomy of mandibular first molars. J Endod 1985;fication rate compared with DOM. However, the great advantage of CBCT 11:568–72.440 Soares de Toubes et al. JOE — Volume 38, Number 4, April 2012
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