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Year : 2020  |  Volume : 23  |  Issue : 4  |  Page : 534-538

Prevalence of middle mesial and middle distal canals in mandibular molars in an Egyptian subpopulation using micro-computed tomography

1 Department of Oral Radiology, Faculty of Dentistry, Umm AlQura University, Makkah, K.S.A
2 Department of Oral Biology and Diagnostic Science, Augusta University, Georgia, USA; Department of Fixed Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt
3 Department of Periodontics, Dental College of Georgia, Augusta University, Georgia, USA; Department of Endodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt

Date of Submission10-Oct-2019
Date of Acceptance20-Dec-2019
Date of Web Publication4-Apr-2020

Correspondence Address:
Dr. M M Elashiry
Department of Periodontics, Dental College of Georgia, Augusta University, 1120 15th Street, CB 2717, Augusta, GA. 30912 Georgia

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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/njcp.njcp_550_19

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Objectives: To study the prevalence of middle mesial and middle distal canals in permanent mandibular molars in Egyptian subpopulation using micro-computed tomography. Materials and Methods: Two hundred and forty extracted mandibular permanent molars of Egyptian patients were scanned using micro-computed tomography, then the images were reconstructed to allow for the detection of the middle mesial (MM) and middle distal (MD) canals of the molars examined. The path of each extra canal was studied to determine the configuration of each canal. Data were analyzed statistically using the Chi-square test with a level of significance set at P< 0.05. Results: The evaluation of three-dimensional (3D) images of this study showed that no significant difference was found between the percentage of MM (27.5%) and MD canals (22.5%) (P = 0.2064); however, there was a significant difference between the percentage of teeth having both extra canals (10%) and teeth having only one of these canals (P < 0.05). The confluent configuration (71%) was significantly higher than the other configurations (P < 0.05). Conclusion: A higher percentage of MM canal was detected followed by the MD canal. The least significant was both canals occurring within the same molar. The percentage of the confluent configuration was the highest. The apt knowledge of the variations of the root canal system anatomy and the respect of the discrepancies associated with diverse demographic areas will ensure the proper management of each tooth with endodontic involvement and its long-term success.

Keywords: Canal configuration, middle distal canal, middle mesial canal, micro-computed tomography

How to cite this article:
Alashiry M K, Zeitoun R, Elashiry M M. Prevalence of middle mesial and middle distal canals in mandibular molars in an Egyptian subpopulation using micro-computed tomography. Niger J Clin Pract 2020;23:534-8

How to cite this URL:
Alashiry M K, Zeitoun R, Elashiry M M. Prevalence of middle mesial and middle distal canals in mandibular molars in an Egyptian subpopulation using micro-computed tomography. Niger J Clin Pract [serial online] 2020 [cited 2022 Aug 17];23:534-8. Available from:

   Introductıon Top

Thorough knowledge of the pulp space morphology and variations improves the ability for locating, and subsequent proper debridement and disinfection of all canals in the root canal system.[1] Missed or untreated canals are implicated in inducing apical periodontitis and eventually failure of the endodontic treatment.[2]

Many studies were carried out to study the morphology of mandibular molars.[3],[4],[5],[6] Traditionally, mandibular molars are described as two-rooted teeth with two canals in the mesial root and one or two canals in the distal root.[7] In 1947, a pioneer study by Vertucci and William described the presence of an extra canal in the mesial root.[8] Another study by Baker et al. showed the same trend of the extra canal in the mesial root.[9] The prevalence of the middle mesial (MM) canal was shown to have a range of 0–46% as reported by different studies.[7],[10],[11]

Although MM canal was extensively studied in different populations using various identification techniques fewer studies on the prevalence of middle distal (MD) canals were performed.[12],[13],[14],[15],[16]

The dental operating microscope is useful in locating and negotiating of MM canal in mandibular molars.[17],[18] Although radiographic examination using conventional intraoral periapical views is vital for the evaluation of the canal configuration, limitations to assess the root canal system completely were reported.[19] 3-dimensional radiographic imaging such as cone-beam computed tomography (CBCT), allowed for detailed visualization of the root canal system.[20] One of the main limitations of the CBCT is loss of details and resolution, especially in the apical part of the root.[19] Micro-computed tomography (micro-CT) imaging is a high-resolution research technology that enabled the development of accurate 3-dimensional (3D) models.[21],[22] It overcomes the limitation of the CBCT by providing 3D radiographic images of the root canal system with higher resolution and more details.[23],[24]

According to the best of our knowledge, the frequency of MM canal and MD canal in permanent lower molars in the Egyptian community has not been well addressed. Therefore, the purpose of this study was to show the prevalence of MM canal and MD canal in permanent lower molars in Egyptian subpopulation, using micro-CT.

   Materials and Methods Top

Two hundred and forty human permanent mandibular molars extracted from Egyptian patients due to severe caries or periodontal disease, after obtaining informed consent, were selected. The teeth were collected from oral surgery clinics, Faculty of Dentistry, Ain Shams University Cairo, Egypt after approval of the research ethics committee of the Ain Shams University with the approval no. FDASU-RECID (021607). All molars had no fractured or surgically separated roots and no previous root canal treatment.

The molars were disinfected by immersing them in 5.25% NaOCl for 10 min. They were kept individually in a labeled container with a normal saline solution for the duration of the study period at room temperature. The setting of the right specifications for scanning was done, then each tooth was placed on the sample standard scanned using SkyScan, a high-resolution desktop micro-CT scanner (SkyScan 1174, SkyScan, Bruker, Belgium). The micro-focus X-ray tube was set at 50 kV of acceleration voltage, 800 μA of beam current. Scanning was performed at 32.17 μm resolution and a 0.5 mm aluminum filter were placed ahead of the radiation origin to alter the responsiveness of polychromatic radiation rotation. The rotation step angle was 0.50° with about 4200 s of camera exposure time positioned middle-far. Then, the micro-CT scanning data produced for each sample was reconstructed to be displayed as 3D images by (NRecon) modeling software (SkyScan 1174, SkyScan, Bruker, Belgium) to obtain the complete configuration of the internal microstructure of each tooth. Data were evaluated using the CT-analyzer (CTAn) computer program (SkyScan 1174, SkyScan, Bruker, Belgium) to observe the occurrence of MM canal, MD canal or both [Figure 1], in addition, to investigate the path of these canals from the appearance of their orifices to the roots' apical foramina to determine the configuration of the extra canals detected [Figure 2].
Figure 1: Cross-sectional reconstructed images showing the detection of (a) the MM canal, (b) the MD canal, and (c) both the MM and the MD canal within the same tooth. MB = mesiobuccal, ML = mesiolingual, DB = distobuccal, DL = distolingual, MM = middle mesial, MD = middle distal

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Figure 2: Representative 3D reconstructed images of the root canals of the mandibular molar examined showing the configuration of the extra canals detected: a) the confluent configuration; where two orifices were detected then the extra canal appeared at a lower level then merge to join one of the two main canals, b) the fin configuration; where two orifices were also detected then an extra canal was detected which has its own path beside one of the main canals and exit through its apical foreman

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Statistical analysis

The data were statistically analyzed using the Chi-square test (GraphPad Prism version 7.00 for Windows, GraphPad Software, La Jolla California USA). Statistical significance was pre-set at P < 0.05.

   Results Top

The results are shown in [Table 1]. The percentage of mandibular molars having MM canal was higher than the percentage of the molars with the MD canal; however, there was no significant difference between these percentages (P = 0.2064). Molars with both MM canal and MD canal occurring in the same tooth showed a significantly lower percentage than that of molars containing either MM canal or MD canal (P < 0.05).
Table 1: The number and the percentages of mandibular molars detected with either MM canal or MD canal or containing both canals within the same tooth

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The configuration of the extra canals showed that the confluent configuration was significantly higher than the fin configuration; no independent configuration was clearly detected (P < 0.05). The results are shown in [Table 2].
Table 2: The percentage of the different configurations of the extra canals detected

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   Discussion Top

Root canal treatment is a multistep process, and the success of this process begins initially with the proper knowledge of the anatomical variations of the root canal system. Missed canals have been considered to be one of the main reasons for endodontic treatment failures.[25] Previous studies reported that missing a canal during endodontic treatment decreased the long-term success of this treatment, it was also showed that 42% of failed endodontic cases were due to missed canals.[26],[27] Different tools have been implicated to aid in locating missed or extra canals such as operating dental microscopes and 3D radiographic techniques.[1],[28] In this study, micro-CT has been used owing to its exceptionally high definition and the accurate details of the scans it produces, Acar et al. compared micro-CT and CBCT to detect accessory canals in primary molars and stated that images obtained using micro-CT showed to have higher resolution and details than CBCT.[23] The use of micro-CT is highly recommended and considered the ideal scanning for in vitro studies owing to the superior resolution and details of its scans.[29]

The results of this study showed that (27.5%) of the mandibular molars examined have MM canal. Previous studies carried on the detection of MM canals showed comparable percentages to our study, however, the variations in the prevalence between these different studies may be attributed to the method of detection used or to the different populations from which the samples were collected and examined.[10],[11],[30],[31],[32] There was no significant difference between the percentage of MM canal (27.5%) and the percentage of MD canal (22.5%). However, the percentage of mandibular molars that have both MM and MD (10%) canals were significantly lower than other mandibular molars having either one of these two extra canals. Due to the lack of extensive studies on MD canals, it was difficult to correlate our study regarding the prevalence of MD canal or the prevalence of both canals occurring together with any other study.[33]

Pomeranz et al. classified the MM canal into three possible canal configurations: fin, confluent, or independent, similar configurations were suggested for the MD canal.[34],[35] (i) Fin: the file passes freely between the main mesial canal (ML or MB) and the MM canal (transverse anatomies), (ii) confluent: the MM canal originates as a separate orifice but apically joins the MB or ML canal, and (iii) independent: the MM canal originates as a separate orifice and terminates as a separate apical foramen. The results showed that 71% of all the extra canals in the mandibular molars that were examined in this study have the confluent configuration. These results are nearly similar to what previous studies showed where the confluent configuration was found in a higher percentage than the other two configurations.[10],[11]

The sample size may be considered a limitation in this study; however, the purpose was to initially underline the incidence and the configuration type of these extra canals in this region. We recommend more extensive studies in the field of root canal morphology using the highly innovative, noninvasive micro-CT technique with a larger number of samples.

   Conclusion Top

It was concluded that the prevalence of MM canal was higher than the MD canal; however, the difference was non-significant. The occurrence of both extra canals in the same tooth was less significant than the occurrence of only one of either MM or MD canals. The extra canals detected had a higher percentage of the confluent configuration rather than the fin or the independent configurations.

The familiarity with the anatomical variations of the root canal system and the related factors affecting this variation may ensure the proper management of each case of root canal treatment and the subsequent long-term prognosis of this treatment.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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