Journal of Conservative Dentistry
Home About us Editorial Board Instructions Submission Subscribe Advertise Contact e-Alerts Login 
Users Online: 335
Print this page  Email this page Bookmark this page Small font sizeDefault font sizeIncrease font size

Table of Contents   
Year : 2020  |  Volume : 23  |  Issue : 1  |  Page : 51-56
To assess the occurrence of middle mesial canal using cone-beam computed tomography and dental operating microscope: An in vitro study

1 Department of Conservative Dentistry and Endodontics, Chettinad Dental College and Rsearch Institute, Kancheepuram, Tamil Nadu, India
2 Department of Conservative Dentistry and Endodontics, A. B. Shetty Memorial Institute of Dental Sciences, Mangalore, Karnataka, India

Click here for correspondence address and email

Date of Submission24-Oct-2019
Date of Decision05-Jul-2020
Date of Acceptance18-Jul-2020
Date of Web Publication10-Oct-2020


Introduction: Failures of root canal treatments are mainly attributed to missed canals and ignorance about the complex anatomy of the root canal system. One such example of anatomic variation is the middle mesial canal (MMC) in mandibular molars which is often missed, and literature on methods for identifying them is limited.
Aim: This in vitro study aimed to assess the occurrence of MMCs with cone-beam computed tomography (CBCT) and then under magnification in the mandibular first and second molars.
Materials and Methodology: A total of 120 extracted intact human permanent mandibular first and second molars were selected. These were subjected to CBCT imaging and magnification for the detection of MMCs. The percentage of incidence in the detection of MMC was compared between these two methods.
Results: The incidence of MMC detected in mandibular molars using CBCT was 13.33% (16 of 120 teeth), while using a dental operating microscope, the incidence was 18.33% (22 of 120 teeth) and the comparison between the two methods was statistically not significant.
Conclusions: Since the incidence of MMC was higher with the use of a microscope, it is preferred to use simpler, chairside aids like magnification and ultrasonic troughing. On the other hand, one should be judicious while subjecting a case to preoperative CBCT evaluation owing to its ionizing radiation.

Keywords: Accessory canal; cone-beam computed tomography; mandibular molar; microscope; middle mesial canal

How to cite this article:
Honap MN, Devadiga D, Hegde MN. To assess the occurrence of middle mesial canal using cone-beam computed tomography and dental operating microscope: An in vitro study. J Conserv Dent 2020;23:51-6

How to cite this URL:
Honap MN, Devadiga D, Hegde MN. To assess the occurrence of middle mesial canal using cone-beam computed tomography and dental operating microscope: An in vitro study. J Conserv Dent [serial online] 2020 [cited 2023 Oct 3];23:51-6. Available from:

   Introduction Top

Clinical endodontics encompasses a wide range of treatments with the common objective of preventing and treating microbial contamination of the pulp, root canal systems, and periradicular tissues.[1]

It is imperative that the clinician has comprehensive knowledge about aberrant anatomy. A potential error at this phase unleashes a plethora of complications leading to compromised treatment prognosis. For example, failure to locate all the canals may provide a persistent source of microbial contamination, altering long-term success of endodontic therapy.[2]

Karabucak et al. evaluated missed canal prevalence in endodontically treated teeth with the help of cone-beam computed tomography (CBCT); they concluded that the missed canal increases the possibility of developing a lesion in a tooth by 4.38 times.[3]

Mandibular molars are the most frequently treated teeth,[4] showing variations in anatomical forms such as C-shaped canals, isthmus, and an additional third canal in the mesial root, i.e., the middle mesial canal (MMC).[5],[6] There is a high incidence of intercanal and intracanal communications in mandibular molars, reaching 83%,[7] but success in accessing and negotiating the MMC is poor, ranging from 1% to 25%.[8],[9] Despite being the most commonly treated tooth with a wide range of anatomic variations, the published literature available on the identification of MMC is scarce and thus was a choice in our study.

A detailed preoperative and intraoperative assessment of landmarks[5],[10],[11] would minimize the number of missed canals and therefore improve the percentage of clinical success.[5],[10]

CBCT-based imaging technology overcomes many of the disadvantages of dental radiography. In this method, the operator can visualize the anatomy of the specimen in three-dimensional slices without destruction of specimen with greater image accuracy and resolution[12] offering a minimal X-ray dose and decreasing in imaging errors such as artifacts and superimposition.[13],[14]

The resolution power of human unaided eye is 0.2 mm, which means two objects situated closer than 0.2 mm will appear as one. Optical aids such as dental operating microscopes (DOMs) (×3.5–25) can enhance the resolution of human eye by many orders of magnitude.

The studies discussing and comparing these preoperative CBCT assessment and intraoperative microscopic assessment methods for recording the incidence of MMCs are scarce; thus, we aimed to record the incidence of these MMCs in mandibular first and second molars using CBCT and DOM.

   Materials and Methodology Top

Thisin vitro study was carried out in the Department of Conservative Dentistry and Endodontics, A. B. Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangaluru, on 120 human intact permanent mandibular first and second molars extracted for periodontal reasons. Teeth with no developmental anomalies, absence of root canal fillings, and root decay were included in the study, while teeth with root resorption and fractured roots were excluded from the study.

Step 1 Assessment of middle mesial canals using cone-beam computed tomography scan

The selected mandibular molars were embedded into customized horseshoe-shaped blocks of modeling wax to simulate the form and shape of a human jaw for mounting on the CBCT machine with 15 sets of 8 specimens in each block [Figure 1], [Figure 2], [Figure 3]. The parameters used during CBCT exposure are mentioned in [Table 1].
Figure 1: Cone-beam computed tomography machine (PLANMECA PROMAX 3D mid)

Click here to view
Figure 2: Teeth mounted in modelling wax to simulate jaw15 sets of 8 specimen teeth in each

Click here to view
Figure 3: Mounted teeth on cone-beam computed tomography machine for scanning

Click here to view
Table 1: Specifications followed during cone-beam computed tomography scan

Click here to view

Analysis of cone-beam computed tomography volumes

The CBCT volumes were analyzed in axial sections for locating the canals by using imaging software (Software Planmeca Romexis 3.4.0.R, Helsinki Finland) following the manufacturer's guidelines [Figure 4]. The enlarged view of axial section shown in [Figure 5].
Figure 4: Axial sections as viewed in cone-beam computed tomography software (PLANMECA ROMEXIS version 3.4.0.R) Inset showing presence of three canals in the mesial root of the mandibular moalar (mesiobuccal, mesiolingual, and middle mesial canal)

Click here to view
Figure 5: Enlarged view of axial section showing middle mesial canal

Click here to view

The volumes were observed by two evaluators; Cohen's kappa value was determined for interobserver reliability. The volumes were observed by two evaluators; Cohen's kappa value was determined for inter-observer reliability. There was a strong agreement between the two observers, κ = 0.784 (P < 0.001).

There was a strong agreement between the two observers, κ = 0.784 (P < 0.001).

Step 2 For intraoperative location of middle mesial canals using dental operating microscope

All teeth were demounted from the wax models used for CBCT scan and embedded in rectangular wax blocks [Figure 6] and [Figure 7]. Standard endodontic access cavities based on the principles stated by Krasner and Rankow in 2004[15] were prepared using airotor handpiece with an Endo Access bur.
Figure 6: Dental operating microscope Carl Zeiss OPMI Pico

Click here to view
Figure 7: Sample preparation for endodontic access under microscope

Click here to view

The teeth in which mesial subpulpal groove was located, the preparation was further modified using standardized guided troughing method. The ultrasonic tips were used to perform the guided troughing. [Figure 8] and [Figure 9] at the expense of the mesio-axial wall. This was done by moving the entire isthmus away from the furcation region mesially and apically to detect the presence of MMCs [Figure 10] which were negotiated using#8 and #10 K-files.
Figure 8: Satellac P5 Ultrasonic Unit

Click here to view
Figure 9: Ultrasonic tip Proultra

Click here to view
Figure 10: A photomicrograph taken using dental operating microscope at ×6 magnification showing the presence of three canals in the mesial root of the mandibular molar (mesiobuccal, mesiolingual, and middle mesial canal)

Click here to view

Analysis access cavities for the detection of middle mesial canals

If MMCs were found, they were confirmed radiographically [Figure 11].
Figure 11: Radiovisiographic image showing the presence of three canals (mesiobuccal, mesiolingual, and middle mesial canal) in the mesial root of the mandibular molar

Click here to view

Statistical analysis

The data for the occurrence of MMC were tabulated systematically to compare the two methods, i.e., DOM and CBCT, the data were subjected to nonparametric McNemar test. The statistical significance was set at P < 0.05.

   Results Top

The incidence of middle mesial canal detected using dental operating microscope was found to be 18.33% while using CBCT it was found to be 13.33% [Table 2] [Graph 1]. Statistical analysis was carried out using Mc Nemar test [Table 3], but significant difference was noted between the two diagnostic aids [p<0.05].
Table 2: Incidence of middle mesial canal using cone-beam computed tomography and DOM

Click here to view
Table 3: Statistical analysis using McNemar test between cone-beam computed tomography and DOM

Click here to view

   Discussion Top

In the presentin vitro study, the incidence of MMCs in 120 mandibular molars was observed using two methods: imaging by CBCT and guided troughing done under DOM.

The incidence of MMCs detected using an operating microscope showed a higher percentage (18.33%) than that of CBCT (13.33%) [Table 2], which was statistically not significant [Table 3].

This is in agreement with anin vitro study on the incidence of MMCs in mandibular molars by Karapinar-Kazandag et al.[9] using DOM which showed an incidence of 18% and 22% in the first and second mandibular molars, respectively. In the present study the the incidence of MMcs detected using CBCT was 13.3%. A study conducted by Akbarzadeh et al.,[16] showed comparable incidence of MMCs to be 14.7%.

The frequency of MMCs in anin vivo study observed using DOM by Sherwani et al.[17] on different age groups of 11–30 years, 31–50 years, and patients >50 years was 36.6%, 22.6%, and 18.4%, respectively. Although the overall incidence of 28.3%, which was higher than the present study, our results were similar to the incidence seen in the elderly age group.

The results of our study are not in agreement with anotherin vivo study conducted by Azim et al.[8] which showed a higher incidence of 46.2% of MMCs in mandibular molars after guided troughing under magnification using DOM. This may be due to thein vivo design of the study which included mandibular teeth from younger age group in contrast to the relatively aged teeth evaluated in ourin vitro study.

Mostin vivo studies include molars from all age groups including teeth from younger individuals, whilein vitro studies are conducted mainly on molars extracted for periodontal reasons in the elderly age group. The location of MMCs in molars decreases in incidence due to the progressive age-related calcification process,[9],[11] making it difficult to visualize, locate, and negotiate the accessory canals.

Our results are also in agreement with anin vitro study by De Toubes et al.[7] which compared the efficacy of four diagnostic methods of clinical examination, digital radiography, DOM, and CBCT. Higher incidence of MMCs was detected using DOM (30%) compared to (27%) CBCT.

The MMC orifice is usually small[18] with a mean minor diameter being three times smaller (0.16 mm) than the main mesial canals (0.50 mm) that lies underneath the dentinal projections which needs to be uncovered and hence is a technical challenge. The operator must frequently explore the mesial subpulpal groove and troughing in apical direction to visualize the mesial isthmus to detect and negotiate this accessory canal with an endodontic instrument.

Troughing of the mesial subpulpal groove when done under the guidance of magnified visualization by DOM not only helps in the location of the orifice of MMCs but also mapping its relation to the main mesial canal (mesiobuccal and mesiolingual) which can be used by clinicians as a navigation guide for searching MMC in routine cases which must be the reason for more MMCs detected by DOM in our study.[8]

The gold standard methods to study the anatomy of root canals are mainly destructive experimental methods performed in a laboratory[19] which are not applicable in clinical scenarios. Hence, in our study to simulate the clinical scenario, we selected a preoperative and an intraoperative method of assessment for the detection of MMC which can be clinically executed.

Successful management of endodontic disease is reliant on preoperative assessment using diagnostic imaging techniques to provide critical information about the teeth and their surrounding anatomy. Periapical radiograph is one of the most common choices for preoperative assessment, but it carries certain limitations like compression of three-dimensional structures to two-dimensional imaging, geometric distortion, and anatomical superimposition.[20]

In the past few decades, newer and more accurate methods have been introduced[20] to enable the nondestructive evaluation of the anatomical variations and morphological characteristics of the roots; one of them is CBCT. It facilitates the clinician to preoperatively assess the anatomy of the tooth in different planes with the feasibility of manipulating the images; hence, this contemporary radiological imaging technique was included in our study because of its reliability over other traditional preoperative assessment methods of radiographic evaluation.[21]

DOM is another device that can enable the visualization and location of root canals as a result of its clear magnification, illumination, and significant field of view.[22] It facilitates improved intraoperative accessory canal identification and evaluation of root canal systems which gives it an edge over other routinely used methods such as clinical examination, dye tracing, or magnification using loupes.[22]

Troughing in the pulp chamber floor with visualization via DOM has been suggested by many authors to improve accessory root canal identification, and hence, troughing with the magnification was the method of choice in our study.[2],[4],[6],[9] Ultrasonic tips were selected for troughing over the access modification burs because troughing in the floor of the pulp chamber at this level requires specialized instrument, clear visual field, precision, and caution to avoid perforating the floor and its complications.[23]

In our study, we chose anin vitro model as it is important to carry the novel methods in experimental conditions before testing in patients, especially when ionizing radiation is involved. However, there are certain drawbacks involved in anin vitro experiment as it cannot fully recreate thein vivo clinical conditions.

   Conclusions Top

Although our study showed a lower incidence of MMC with the use of CBCT compared to DOM, the use of CBCT to study morphologic visualization of the canal trajectory cannot be disputed. This holds true specifically in the mid and apical thirds of the roots where visualization with DOM is limited only to the straight portion of the canal. However, it has been suggested[24] that not all canals can be detected with CBCT; thus, it should be used as an auxiliary method in identification rather than as a replacement for careful clinical scouting techniques.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Hargreaves KM, Berman LH. Cohen's Pathways of the Pulp expert consult. Elsevier Health Sciences; 2015.  Back to cited text no. 1
Song M, Kim HC, Lee W, Kim E. Analysis of the cause of failure in nonsurgical endodontic treatment by microscopic inspection during endodontic microsurgery. J Endod 2011;37:1516-9.  Back to cited text no. 2
Karabucak B, Bunes A, Chehoud C, Kohli MR, Setzer F. Prevalence of apical periodontitis in endodontically treated premolars and molars with untreated canal: A cone-beam computed tomography study. J Endod 2016;42:538-41.  Back to cited text no. 3
Yousuf W, Khan M, Mehdi H. Endodontic procedural errors: frequency, type of error, and the most frequently treated tooth. International journal of dentistry. 2015 Aug 10;2015.  Back to cited text no. 4
Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol 1984;58:589-99.  Back to cited text no. 5
Gulabivala K, Aung TH, Alavi A, Ng YL. Root and canal morphology of Burmese mandibular molars. Int Endod J 2001;34:359-70.  Back to cited text no. 6
De Toubes KM, Côrtes MI, Valadares MA, Fonseca LC, Nunes E, Silveira FF. Comparative analysis of accessory mesial canal identification in mandibular first molars by using four different diagnostic methods. J Endod 2012;38:436-41.  Back to cited text no. 7
Azim AA, Deutsch AS, Solomon CS. Prevalence of middle mesial canals in mandibular molars after guided troughing under high magnification: Anin vivo investigation. J Endod 2015;41:164-8.  Back to cited text no. 8
Karapinar-Kazandag M, Basrani BR, Friedman S. The operating microscope enhances detection and negotiation of accessory mesial canals in mandibular molars. J Endod 2010;36:1289-94.  Back to cited text no. 9
Cantatore G, Berutti E, Castellucci A. Missed anatomy: Frequency and clinical impact. Endodontic Topics 2006;15:3-31.  Back to cited text no. 10
Ahmed, Abbott PV. Accessory roots in maxillary molar teeth: A review and endodontic considerations. Aust Dent J 2012;57:123-31.  Back to cited text no. 11
Patel S, Dawood A, Ford TP, Whaites E. The potential applications of cone beam computed tomography in the management of endodontic problems. Int Endod J 2007;40:818-30.  Back to cited text no. 12
Cotton TP, Geisler TM, Holden DT, Schwartz SA, Schindler WG. Endodontic applications of cone-beam volumetric tomography. J Endod 2007;33:1121-32.  Back to cited text no. 13
Matherne RP, Angelopoulos C, Kulild JC, Tira D. Use of cone-beam computed tomography to identify root canal systems in vitro. J Endod 2008;34:87-9.  Back to cited text no. 14
Krasner P, Rankow HJ. Anatomy of the pulp-chamber floor. J Endod 2004;30:5-16.  Back to cited text no. 15
Akbarzadeh N, Aminoshariae A, Khalighinejad N, Palomo JM, Syed A, Kulild JC, et al. The association between the anatomic landmarks of the pulp chamber floor and the prevalence of middle mesial canals in mandibular first molars: AnIn vivo analysis. J Endod 2017;43:1797-801.  Back to cited text no. 16
Sherwani OA, Kumar A, Tewari RK, Mishra SK, Andrabi SM, Alam S. Frequency of middle mesial canals in mandibular first molars in North Indian population-Anin vivo study. Saudi Endodontic J 2016;6:66.  Back to cited text no. 17
Versiani MA, Ordinola-Zapata R, Keleş A, Alcin H, Bramante CM, Pécora JD, et al. Middle mesial canals in mandibular first molars: A micro-CT study in different populations. Arch Oral Biol 2016;61:130-7.  Back to cited text no. 18
Neelakantan P, Subbarao C, Subbarao CV. Comparative evaluation of modified canal staining and clearing technique, cone-beam computed tomography, peripheral quantitative computed tomography, spiral computed tomography, and plain and contrast medium-enhanced digital radiography in studying root canal morphology. J Endod 2010;36:1547-51.  Back to cited text no. 19
Patel S, Kanagasingam S, Mannocci F. Cone beam computed tomography (CBCT) in endodontics. Dent Update 2010;37:373-9.  Back to cited text no. 20
Assadian H, Dabbaghi A, Gooran M, Eftekhar B, Sharifi S, Shams N, et al. Accuracy of CBCT, digital radiography and cross-sectioning for the evaluation of mandibular incisor root canals. Iran Endod J 2016;11:106-10.  Back to cited text no. 21
Baldassari-Cruz LA, Lilly JP, Rivera EM. The influence of dental operating microscope in locating the mesiolingual canal orifice. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;93:190-4.  Back to cited text no. 22
Krupp C, Bargholz C, Brüsehaber M, Hülsmann M. Treatment outcome after repair of root perforations with mineral trioxide aggregate: A retrospective evaluation of 90 teeth. J Endod 2013;39:1364-8.  Back to cited text no. 23
Miller L. How cone beam computed tomography increases endodontic success. J Mass Dent Soc 2016;65:20-2.  Back to cited text no. 24

Correspondence Address:
Dr. Manjiri Nagesh Honap
TVH Ouranya Bay, Tower 4, Flat 4252, Padur OMR, Chennai - 603 103, Tamil Nadu
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCD.JCD_462_19

Rights and Permissions


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]

  [Table 1], [Table 2], [Table 3]

This article has been cited by
1 Age and experience with dental operating microscope: Do these factors influence on the post space preparation and adhesion of glass fiber posts?
Mariana Porciuncula, Adriana P. Teixeira, Thais M. Duque, Marina C. Prado, Renata A. Simão, Maíra Prado
Microscopy Research and Technique. 2022;
[Pubmed] | [DOI]
2 Three mesial root canals of mandibular second molars: Two case reports
Hui-Zi Zeng, Qi-Jun Dai, Wei-Qun Guan
Asian Journal of Surgery. 2022;
[Pubmed] | [DOI]
Suman Kar, Swarupananda Bera, A. B. Maity, Progyna Paramita Pal, Gargi Das, Anjali Singh
[Pubmed] | [DOI]
4 Endodontic management of permanent mandibular first molar with middle mesial canal: A case report
HadiRajeh Alfahadi, FawazHamad Alkazman, Ahmed Bamanie, MesferSaleh Alwadai
Saudi Journal of Oral Sciences. 2021; 8(1): 53
[Pubmed] | [DOI]


    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Email Alert *
    Add to My List *
* Registration required (free)  

    Materials and Me...
    Article Figures
    Article Tables

 Article Access Statistics
    PDF Downloaded116    
    Comments [Add]    
    Cited by others 4    

Recommend this journal