Journal of Conservative Dentistry

: 2017  |  Volume : 20  |  Issue : 3  |  Page : 190--193

An in vitro study to find the incidence of mesiobuccal 2 canal in permanent maxillary first molars using three different methods

V Vasundhara, Krishna Prasada Lashkari 
 Department of Conservative Dentistry and Endodontics, KVG Dental College (affiliated by Dental Council of and Rajiv Gandhi University of Health Sciences), Sullia, Karnataka, India

Correspondence Address:
V Vasundhara
Department of Conservative Dentistry and Endodontics, KVG Dental College (affiliated by Dental Council of India and Rajiv Gandhi University of Health Sciences), Sullia - 574 327, Karnataka


Aim: In-vitro study was done to evaluate the incidence of MB2 canals using three different methods (CBCT, CLINICAL ANALYSIS AND DENTAL LOUPES) and to compare the efficacy of the three methods in identifying the incidence of MB2 canals in maxillary permanent first molars. Materials and Methods: The study sample consisted of 120 extracted intact permanent maxillary molars. These extracted teeth were subjected to CBCT. Later the teeth were access opened with naked eye to find the incidence of MB2 canal, and then the teeth were visualised under dental loupe to locate MB2 canal if they were missed under naked eye. Results was statistically analysed by Mc Nemar's tests with Bonferroni correction, Chi square test and Cochran's Q test. Result: CBCT showed high incidence (68.3%) of MB2 canal in maxillary first molars and it showed to be a reliable method in detecting MB2 canal. When compared to dental loupe (52.5%) and naked eye (25%), the dental loupe improved the detection of MB2 canal. Conclusion: Within the parameter of this study in detecting the incidence of MB2 canal, using CBCT dental loupes and naked eye, detection of MB2 canal was significantly higher with CBCT followed by dental loupe and least with naked eye.

How to cite this article:
Vasundhara V, Lashkari KP. An in vitro study to find the incidence of mesiobuccal 2 canal in permanent maxillary first molars using three different methods.J Conserv Dent 2017;20:190-193

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Vasundhara V, Lashkari KP. An in vitro study to find the incidence of mesiobuccal 2 canal in permanent maxillary first molars using three different methods. J Conserv Dent [serial online] 2017 [cited 2022 Jun 25 ];20:190-193
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An adequate cleaning and shaping of all the pulp spaces and its complete filling with an inert material is one of the primary goals of endodontic treatment. It is reported that the maxillary first molars have a root canal anatomy with maximum complexity and variations.[1] Because of this complexity, it has the highest failure rate in endodontic treatment, that often lead to a missed second canal in the mesiobuccal 2 (MB2) root, that remains undetected and therefore untreated.[2]

Incidence of MB2 canal has been researched by numerous authors using various methods. In vivo, clinical studies included examinations of the maxillary first molar during root canal treatment both with and without magnifications and also retrospective assessment of radiographs and records. However, the results were not satisfactory.[3]

Traditional means of determining its presence and location include clinical examination and conventional two-dimensional radiography.[4]

Conventional radiography, while an essential aspect of endodontic treatment, has several limitations that make it less than an ideal tool for locating MB2. Because periapical (PA) radiography shows only a two-dimensional image and the superposition of the subjacent anatomic structure with the cortical density.[5]

Various clinical studies have shown examination of the maxillary first molar during root canal treatment with and without magnification, and also modification of access cavity preparation has been researched by numerous authors by the use of newer technique such as dental computed tomography (CT), cone-beam computed tomography (CBCT), and scanning electron microscopy.

Magnification is critically essential element to consistently identify the MB2 canal orifices. Clinical studies with magnification include dental loupes which provide magnification of ×2.0–×6.0. Magnification helps the practitioner to view the pulp chamber floor and brings minute details into clear view.[6]

CBCT is a relatively recent innovation that overcomes many of the limitations of conventional radiography. It has many applications in endodontics because it's three-dimensional images allow inspection of the tooth in the axial, coronal, and sagittal planes.[7]

The purpose of this study was to evaluate the incidence of MB2 canals using three different methods (CBCT, clinical analysis, and dental loupes) and to compare the efficacy of the three methods in identifying the incidence of MB2 canals in the maxillary permanent first molars. This study may help clinician identifying, negotiating, and treating missed second canals in the permanent maxillary first molar for better prognosis.


One hundred and twenty extracted intact permanent maxillary molars were collected from Department of Oral Surgery, K.V.G Dental College and Hospital, Sullia, and private dental clinics. The collection, storage, sterilization, and handling of 120 extracted teeth were followed according to occupational safety and health administration and the Center for Disease Control and Prevention recommendations and guidelines. The teeth were cleaned of visible blood and gross debris. The teeth were stored in 1% thymol solution for 1 week. The teeth were kept in a well-constructed container with a secure lid to prevent leaking during transport. The container was labeled with biohazard symbol.

The teeth were numbered from 1 to 120. Three teeth were positioned and organized in a wax slab in a row. A gutta-percha cone was placed on the right side of the wax slab to identify in the CBCT image, later each slab was scanned with CBCT (Kodak, 9300c, U.S.A). The voxel of 0.2 mm was used with an exposure of 16 min. The record of the number of canals and their variations was recorded by two examiners, one endodontist, and one radiologist [Figure 1].{Figure 1}

An access cavity was prepared under halogen bulbs using #2 and #4 Endo Access bur (Maillefer, Dentsply, Switzerland). Initial penetration was made in the exact center of the mesial pit, with the bur directed toward the palatal using a high-speed handpiece to the depth of dentin. The bur was directed toward the orifice of the palatal canal. When a drop was felt, the pulp chamber was reached. The larger palatal canal was located first after which safe-ended #0152 Endo-Z bur (Maillefer, Dentsply, Switzerland) was used, keeping it in contact with the floor of the pulp chamber and moved mesiobuccally to the center of the MB cusp. The MB canal was explored beneath the cusp tip, and the bur was moved distally and slightly palatally to locate the distobuccal canal orifice. A conventional triangular access was modified to a trapezoidal shape to improve access to the additional canals. Final finishing and funneling of cavity walls was done with Endo-Z fissure bur. After an adequate access cavity preparation, the contents of the pulp chamber were removed using an endodontic excavator and subsequent irrigation with a 2.5% sodium hypochlorite solution. The pulp chamber floor was explored using an endodontic explorer, DG-16 (Maillefer, Dentsply, Switzerland). Exploration of groove connecting the canal orifice was performed with the use of K-files #6, #8, or #10 (Mani, Japan). Prepared specimens were then explored for MB2 in the following sequence:

Stage 1: Teeth were checked with naked eye (unaided vision) for second canal in the MB root with the help of explorer and then k-files #6 or #8, and ethylenediaminetetraacetic acid was used to negotiate MB2 canal.

If canal was not located by naked eye, samples will be subjected to stage 2.

Stage 2: Teeth failed to locate MB2 canal were examined with dental loupes ×3.5 magnification for the presence of MB2. If MB2 was located with or without magnification, Size 6, 8, and 10 k-file was inserted in MB and MB2 canals [Figure 2]. The results were statistically analyzed by McNemar's tests with Bonferroni correction, Chi-square test, and Cochran's Q test.{Figure 2}


In the present study, 120 extracted teeth were subjected to CBCT, dental loupe, and naked eye to find the incidence of MB2 canal and to evaluate the efficacy of these three methods in finding MB2 canal. MB2 canal was seen with CBCT in 82/120 (68.3%) teeth. With naked eye, it was found in 30/120 (25.0%), whereas in dental loupe, MB2 canal was located in 63/120 (52.5%). This difference in frequency of locating MB2 canal with the help of CBCT, naked eye, and dental loupe is statistically significant (P < 0.001) [Table 1].{Table 1}

With a Cochran's Q test, we found that there exists a significant difference in the ability of the methods to detect the MB2 canal (X2(2) = 8.22, P < 0.05).

A pairwise comparison using McNemar's tests with Bonferroni correction revealed that significantly more number of MB2 canals was detected using CBCT or dental loupes as compared to naked eye (P < 0.001). CBCT was also better than dental loupes in detecting the MB2 canals (P < 0.001).

[Table 2] shows a comparison of CBCT, dental loupe with the naked eye. It was seen that with the help of CBCT and naked eye, thirty (25.0%) MB2 canals were located, 52 (43.3%) MB2 canals were observed in CBCT, but not in naked eye, and 38 (31.7%) MB2 canals were not located either in CBCT or naked eye whereas thirty (25.0%) MB2 canals were located both with naked eye and dental loupe. Thirty-three (27.5%) MB2 canals were located only in dental loupes but not with naked eye and 57 (47.5%) MB2 canals were not located either with naked eye or dental loupe. This difference in locating MB2 canal is statistically significant with CBCT.{Table 2}

In 30 (25.0%) out of 82 (68.3%) extracted first molar teeth, MB2 canal was found with naked eye and the number increased to 63 (52.5%) when dental loupes were used (P < 0.001).


The historical triad states that “debridement, disinfection, and obturation” are important for success of root canal therapy,[8] for which endodontist must have comprehensive knowledge about root canal morphology. If a root canal is not located, it may reduce the chances of treatment success and is one of the main reasons for the failure of root canal therapy.[9]

The present study highlights the importance of recent advancing techniques such as CBCT in determining the root canal morphologies in the maxillary first molar and the use of magnifying loupes for locating canals which are usually missed by naked eye in general practice.

The first maxillary molar is the most bulky teeth in the mouth and presents with numerous anatomical variations such as number and disposition of the canals. Clinically, the MB root contains second MB canal, which can be identified and treated more than 70% of the time.[10] Weine in a study done in 1969 showed higher frequency of MB2 canal in the MB root region. CBCT is a newer diagnostic imaging modality used in endodontics as it demonstrates anatomic features in three dimensions. CBCT provides interrelational images in three orthogonal planes (axial, sagittal, and coronal).

Baratto Filho et al.[11] reported the frequency of finding extra canal in MB root of the maxillary first molars is 92.85% (ex vivo), 95.63% (clinical results), and 95.45% (CBCT results). Michetti et al.[12] compared CBCT reconstructions of root canal systems with histological sections. The authors found a strong correlation between data acquired through CBCT and histological sections.

Dental loupes provide a magnification of better visualization as it enables the clinician to treat cases which were otherwise labeled as having poor prognosis or untreatable. However, limited evidence has been found that the use of a magnification device in any endodontic procedure is related to a better clinical outcome as compared to the same procedure performed without magnifiers.[13]

In a study conducted by Iqbal out of 300 extracted maxillary molars, MB2 canal observed in naked eye was 77 (25.7%), whereas with the use of dental loupe, the number of location of MB2 canal was increased up to 223 (88.3%).[14]

Magnification has been found to increase the detection rate of MB2 canals from 17.2% with the naked eye to 62.5% with loupes and 71.1% using the surgical operating microscope.[15]


In the present study, the detection of MB2 canal with naked eye was 25% and with the use of dental loupes the detection of MB2 canal increased up to 52.5%. This finding showed that magnification increases the clinical ability to locate canals is supportive with the result obtained by above studies.

This study concluded that the incidence of MB2 canal detection was increased by the use of CBCT scans and dental loupe in comparison to naked eye.

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Conflicts of interest

There are no conflicts of interest.


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