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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 14  |  Issue : 4  |  Page : 220-224

An evaluation of mandibular molars root canal morphology using cone-beam computed tomography in an Egyptian subpopulation


1 Department of Endodontics, College of Dentistry, Suez Canal University, Ismailia, Egypt
2 Department of Oral Radiology, College of Dentistry, Suez Canal University, Ismailia, Egypt

Date of Submission29-Sep-2017
Date of Acceptance04-Nov-2017
Date of Web Publication21-Dec-2017

Correspondence Address:
Marwa E Sharaan
Building No. 533, District No. 6, Ismailia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tdj.tdj_50_17

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  Abstract 

Introduction
The aim of this study was to assess the root canal (RC) anatomy of mandibular permanent molars using cone-beam computed tomography (CBCT) in an Egyptian Ismailia population.
Materials and methods
Four hundred and thirty-six mandibular molars were included in this study. CBCT scans were evaluated by an oral radiologist and an endodontist. Root morphology and number as well as RC number were evaluated. RC configurations were classified according to Vertucci's method. Sex and bilateral symmetry were recorded. For RC configurations, sex and bilateral sides, Pearson's χ2-test was used (P ≤ 0.05).
Results
Two hundred and seventeen mandibular first molars demonstrated two roots configuration. Only one case had an extradistolingual root with type I RC. For the mandibular second molars, majority of the 218 were two roots configuration. Only four cases showed single root configuration. Regarding mandibular first molars, the frequency of Vertucci's classification for the mesial root were type IV (83.94%), type II (11.93%), type III (3.21%) and type VII (0.92%). For the distal root, were type I (62.84%), type II (19.72%), type III (10.55%), type IV (2.75%), type V (3.67%) and type VII (0.46%). Regarding mandibular second molars, the highest frequency of Vertucci's classification for the mesial root were type II (57.71%) then type IV (28.86%), type III (7.46%), type I (5.47%) and type V (0.5%). For the distal root, the most common of Vertucci's classification were type I (95.02%) followed by type II (3.48%), type III (0.99%) and type IV (0.5%). C-shaped canals were noticed in mandibular second molars only. Bilateral symmetry was displayed significantly regarding extra canal. There was significant difference between females and males (<0.05).
Conclusion
Preassessment of the mandibular molars using CBCT imaging provides clear data for the RC morphology that might increase the prognosis of the RC treatment.

Keywords: cone-beam computed tomography, Egyptian subpopulation, mandibular molars, root canal morphology


How to cite this article:
Sharaan ME, Elrawdy AM. An evaluation of mandibular molars root canal morphology using cone-beam computed tomography in an Egyptian subpopulation. Tanta Dent J 2017;14:220-4

How to cite this URL:
Sharaan ME, Elrawdy AM. An evaluation of mandibular molars root canal morphology using cone-beam computed tomography in an Egyptian subpopulation. Tanta Dent J [serial online] 2017 [cited 2018 May 24];14:220-4. Available from: http://www.tmj.eg.net/text.asp?2017/14/4/220/221384


  Introduction Top


Successful root canal (RC) treatment depends mainly on complete cleaning and shaping of all pulp spaces and hermetic seal by thorough obturation. It is crucial that operators should be acquainted by the common RCs morphology and their variations [1]. RC morphology varies from population to another. To study RC morphology in various populations; several techniques were used, such as dye penetration, sectioning, clearing, preoperative and postoperative radiographs, micro-computed tomography (μ-CT) and cone-beam computed tomography (CBCT) [2]. In 1990, CBCT was introduced in the field of endodontics [1],[3]. Because of the complex RC anatomy of the mandibular molars, several studies have been tried to assess the common anatomy and its variation. According to literature most of the mandibular molars have demonstrated two roots with two RCs in mesial root (MR) and one in distal root (DR). However, few of them displayed some anatomical variation [4],[5]. Prevalence of additional distolingual root or radix entomolaris in mandibular first permanent molar was evident as 3.4–4.2% in European populations, 3% in African population, 7.67% in Indians, 5–30% in Chinese, Eskimo and American Indians [4],[5],[6]. There is a significant ethnic variation in the incidence of C-shaped molars that ranges between 10 and 32.7% [7],[8],[9],[10]. Studies for the Egyptian population is very minimal, only one recent study was published this year on maxillary molars [11]. Additionally, there is no published study on the RC anatomy of mandibular molars in the Egyptian Ismailia population. Hence, the goal of this study was to evaluate the RC anatomy of the mandibular molars in this subpopulation using CBCT.


  Materials and Methods Top


The present retrospective study was performed on the CBCT records obtained from the archives of the Outpatient Clinic of the Oral Radiology Department, College of Dentistry, Suez Canal University. Out of respect for patient confidentiality, all personal information concerning the patients other than sex and age was hidden. CBCT images of mandibular molars were obtained during the period January 2015 to July 2017. The study was conducted on 109 CBCT scans of bilateral mandibular sides (436 mandibular first and second molar teeth) of both sexes and ranging in age from 15 to 49 years. The CBCT scans included in the present study had to reveal the entire region of the mandibular molar teeth and be of high quality images free from artifacts caused by metallic objects that may impair pulp chamber visualization. Inclusion criteria also included: absence of extracted mandibular first and second molars: with fully matured apices and without apical periodontitis and no RC fillings, posts, or full-crown restorations.

Cone-beam computed tomography scanning protocol

All CBCT scans used in the present study were obtained using the Scanora 3D Imaging System (Sordex, Helsinki, Finland) using a CMOS flat panel detector with isotropic voxel size 133 μm. The X-ray tube used to scan the patients possess a current intensity 10 mA, 90 kVp and a focal spot size 0.5 mm. The scanning time was 10 s of pulsed exposure resulting in an effective exposure time of 2.4 s to scan field of view of 14 cm height × 16.5 cm width. Field of view adjustment was guided by three laser light beams to centralize the area of interest within the scanning field. The primary reconstruction time for DICOM data set was 2 min. Then, the raw DICOM data set images were imported to the On-Demand software (Cybermed, Seoul, Korea) for secondary reconstruction.

Image analysis and assessment of the root and root canals of mandibular first and second molars

Serial axial, coronal, and sagittal CBCT images were acquired by an experienced radiologist according to the operation instructions. Reformatted images were examined by carefully rolling the toolbar from the pulp chamber to the apex. All the images were assessed by a radiologist and an endodontist, and any disagreement between them was discussed until a consensus was reached. The number and configuration of the roots, the number of RCs, the RC configurations according to Vertucci's classification, the incidence of extra canals in the MR and DR [Figure 1]. The frequency of C-shaped RC and symmetry in the number of RC between adjacent and contralateral molars were also determined [Figure 1]. The examiners assessed the images twice, then a week interval between the two evaluations.
Figure 1: Axial cone-beam computed tomography imaging displaying. (a) three root canals. (RCs) for mandibular first and second molar, (b) two RC for mandibular second molar and three RC for mandibular first molar, (c) C-shaped RC for mandibular second molar, (d) four RC for mandibular first molar.

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Statistical analysis was performed using statistical package for the social sciences software (SPSS, version 20; IBM Corp., Armonk, New York, USA). The relationship between the patients' sex or the sides and the molar configuration was determined using the Pearson's χ2-test. The level of significance was at 0.05 (P ≤ 0.05). The incidence of additional canals was determined by frequency.


  Results Top


CBCT examination of mandibular first and second molars was done for 109 patients, having 64.22% women and 35.77% men (70 females and 39 males).

Root and root canal configuration

CBCT assessment of 218 mandibular first molars revealed one case with three roots (additional distolingual root) on the right side only (radix entomolaris), the 217 teeth had two roots. The number of RC in mandibular first molar was three in 61.42% of the female patients, 26 (66.67%) cases of the male patients on both sides. Four RC were found in 38.57% of the female patients on both sides. For the male patients four RC was found in 30.77% on the right side and 33.33% on the left side. Of the 218 mandibular second molars, there were two (2.86%) cases single-rooted with C-shaped RC for the females on both sides. For the mandibular second molars that had two roots with two RC, one (1.43%) case of the females on both sides. Moreover, for the two-rooted mandibular second molars with three RC, there were 92.3% for the male patients on the right side and 84.28% for the females. For the left side, 94.87% for males and 84.28% for females. Those having four canals, there were 2.56% for the male patients on the right side, 7.14% for the females. For the left side, 2.85% for females. Furthermore, in two rooted mandibular second molars, C-shaped canals were noticed in 5.13%, 4.28% of males and females on the right side respectively. Whereas 5.13%, 8.57% of males and females, respectively, had C shaped canals on the left side. Using Pearson's χ2-test, there was statistically significance between females and males on both sides for the mandibular first and second molars (P ≤ 0.05) [Table 1] and [Table 2]. Additionally, regarding the frequency of the number of RC of the mandibular first and second molars there was no significant difference between right and left sides (P > 0.05) [Table 1] and [Table 2].
Table 1: Root and root canal configuration of mandibular first molars

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Table 2: Root and root canal configuration of mandibular second molars

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Frequency of root canal type

For the mandibular first molars, 26 (11.93%) MR with a type II RC morphology, whereas there were 183 (83.94%) ones with a type IV RC morphology. In addition, seven (3.21%), two (0.92%) with a type III, type VII RC morphology, respectively. One hundred and thirty-seven (62.84%) DR of teeth had a type I RC morphology. Only one (0.46%) of the DR had type VII RC morphology. Forty-three (19.72%) of the DR with a type II RC morphology, whereas there were 23 (10.55%), six (2.75%) and eight (3.67%) with type III, IV, V RC morphology, respectively [Table 3]. Regarding the mandibular second molars, 116 (57.71%) MR with a type II RC morphology, whereas there were 58 (28.86%) ones with a type IV RC morphology. Eleven (5.47%) and 15 (7.46%) of MR of teeth had type I, III RC morphology, respectively. Only one (0.5%) of the MR had type V RC morphology. One hundred and ninety-one (95.02%) of the DR with a type I RC morphology, whereas there were seven (3.48%) with a type II RC morphology. Two (0.99%) and one (0.5%) of DR of teeth had type III, IV RC morphology, respectively [Table 4].
Table 3: Frequency of root canal type of mandibular first molars

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Table 4: Frequency of root canal type of mandibular second molars

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  Discussion Top


Primary objective of the present retrospective study was to assess the RC anatomy of the mandibular molars in addition to the frequency of extra canals in the Egyptian Ismailia subpopulation using CBCT. Several techniques were implicated to study RC anatomy. For example, demineralization and staining techniques were well documented for their accuracy [2],[9],[10],[11]. μ-CT utilizes an accurate and reliable image of the RC morphology. But, some of the previously mentioned techniques are in vitro, so the sample size will be limited. Additionally, the contralateral evaluation in the same time might be inapplicable. Comparing CBCT to μ-CT imaging, both lower radiation dose and cost are of great advantages of CBCT over μ-CT. It was proved the CBCT demonstrated high accuracy which is comparable to canal staining and clearing techniques [12],[13]. In spite of the development of many classifications, Vertucci's remains the gold standard that is widely used whenever there is a description and comparison of RC morphology [2],[9].

It has been documented in many populations that mandibular first molars have one mesial and one DRs [14]. We found that 99.54% of the first molars had two roots located mesially and distally. In the current study, we found only one mandibular first molar had an extra distolingual root or radix entomolaris (0.64%). This frequency was less than that reported in previous studies that ranged from 15 to 29% [13],[14],[15],[16],[17]. However, the prevalence of an extra distolingual root was lower than 5% in some European (British, Dutch, German, Finnish), African (Bushmen, Bantu, Senegalese) and Indian populations [2],[4],[5],[6],[9]. The configuration of the additional distolingual RC in the present study was found to be type I. This result was in accordance with previous studies [2],[13],[18].

In this study, the percentage of two canals in the MR and DR for the first molar was 100 and 37.15%, respectively. Type IV configuration was the most common in MR of the first molars. This result was in agreement with other reports [2],[13],[17],[18],[19],[20]. However, Zaatar et al. [21] and Al-Nazhan [22] reported type II was the most prevalent followed by type IV. Only 2 (0.92%) patients had a type VII configuration in the MR of the first molars, which was in accordance with the study by Chen et al. [17] (0.2–5%). The most common canal configuration of DRs was type I, with a documented frequency ranged between 54 and 72% [2],[9],[13],[15],[20],[22]. In the current study, type I configuration was the most prevalent in the DRs. Furthermore, in this study, type II, type IV, type V and type VII configurations were found to be higher in the DR than those displayed by Demirbuga et al. [13] and Gu et al. [23].

As regard to the mandibular second molars, most of them (98.16%; 214 teeth) had two roots located mesially and distally. This finding is similar to others but they reported lower incidence in Turkish (85.4%) [13], in Burmese (58.2%) [17] and Thai (54%) populations [9]. The second molars had two canals in 94.52 and 4.98% of the mesial and DRs, respectively. This finding is similar to those documented earlier by studies of Turkish and western Chinese populations by using CBCT [13],[19]. The most common RC configuration of second molar in the current study was type II (57.71%) in the MR and type I (95.02%) in the DR. This observation is conversely to those of Demirbuga et al. [13] and Ahmed et al. [24], where they found type IV more prevalent. Furthermore, our finding is in contrast toothers of Gulabivala et al. [9] who displayed type I as the most frequent canal configuration in the MR of the second molar tooth in a Caucasian population. In the current study, type I configuration was the most prevalent in the DRs. Furthermore, in this study, type II and type IV configurations were found to be higher in the DR than those displayed by Demirbuga et al. [13] and Gu et al. [23]. Interestingly, C-shaped canals were noticed only in the second molars with prevalence of 28.83%. This finding with in agreement with previous studies showed high incidence of C-shaped roots and canals (14–52%) [7],[8],[9],[10]. These dissimilarities might be because of the different methodology, population size and/or the regional population variety. Another possible explanation is the variation in interpretation of images and CBCT resolution.

For both mandibular first and second molars, sex did influence the frequency of additional canals on both sides. This finding was not in consistent with others, where there was no significant difference between males and females [19],[24]. Unequally distribution of sexes between groups might be responsible for our finding. The incidence of the number of RC of the mandibular first and second molars did not differ significantly between right and left sides. This finding was in an agreement with previous studies [25],[26]. Nevertheless, there is always confusing results regarding sex, bilateral symmetry and the incidence of extra canals [25],[26].


  Conclusion Top


According to the findings from the present retrospective study we concluded that:

  • For the mandibular first molars, majority of the Egyptian Ismailia subpopulation have revealed type IV of Vertucci's RC classification in the MR followed by II, III, VII.
  • For mandibular second molars, majority of the Egyptian Ismailia subpopulation have displayed type II of Vertucci's RC classification in the MR followed by IV, III, I, V.
  • Distal roots showed variations in the mandibular first and second molars, where type I was noticed more frequently followed by II, III, IV.
  • Distal roots showed additional variations in the mandibular first molars, where type V and VII were displayed.
  • C-shaped canals were noticed in mandibular second molars only.
  • Bilateral symmetry was displayed significantly regarding extra canal.
  • There was significant difference between females and males.
  • Further studies are needed having larger population of patients.
  • Pre-assessment of the mandibular molars using CBCT imaging provides clear data for the RC morphology that will help in increasing the prognosis of the RC treatment.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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