The Prevalence of a Second Mesiobuccal Canal of Maxillary First and Second Molars Using CBCT Among Egyptian Population: A Cross-Sectional Study
Conditions: Second Mesiobuccal Canal, Maxillary First and Second Molars
Sponsor: Cairo University

The Prevalence of a Second Mesiobuccal Canal of 
Maxillary First and Second Molars Using 
CBCT among Egyptian Population: A Cross-
Sectional Study 
 
 
Protocol submitted to the Faculty of Dentistry 
 Cairo University 
In partial fulfilment of the requirements for Master Degree in 
Oral and Maxillofacial Radiology 
Research Code: Rad2:5:1 
Clinical Trials.gov ID: NCT03225573 
Presented by: 
Yomna Mohammad Gamal EL-Din Saadi 
Faculty of Dentistry 
Misr International University 
B.D.S 2012 
6 July 2017 
 
 
 

Supervisors 
 
 
Dr. Nashwa Salah 
Professor of Oral and Maxillofacial Radiology  
 
Faculty of Dentistry 
 
Cairo University 
 
Dr. Farid Medhat 
Lecturer of Oral and Maxillofacial Radiology  
 
Faculty of Dentistry 
 
Cairo University 
 
 
 
 

1 
 
Introduction 
 
Knowing the proper root and canal morphology is of paramount importance 
to avoid failures of endodontic treatment. (Altunsoy et al 2014). Root canal 
morphology is also important during post-core and crown restorations because post 
preparation can result in root canal deviation or root canal perforation. 
Therefore, clinicians should recognize the common root canal morphologies 
and possible anatomic variations. The clinician should be aware of the possibility 
of having additional canals in order to minimize the risk of treatment failure (Weine 
et al 1969 and Vertucci 2005). 
The internal complexities of root canals are genetically determined and carry 
definitive importance in anthropology (Neelakantan et al 2010, Silva et al 2014). 
It is necessary to consider racial differences during clinical treatment. 
The Root canal anatomical variations due to genetic and ethnic differences 
have been discussed in many studies (Chen & Tong 2004; Weng et al 2009; 
HosseinpourSepanta et al 2016 and Naseri et al 2016). 
Many studies investigated the morphology of the maxillary permanent 
molars focusing on the presence of a second mesiobuccal root canal in the mesial 
root (Pecora et al 1992; Sert & Bayirli 2004; Cleghorn et al 2006). They reported 
varying prevalence of the second mesiobuccal canal of maxillary first and second 
molars. 
The maxillary molars have a complex morphology (Silva et al 2014).  Based 
on the published results, it was recognized that most maxillary first molars have 3 
roots and 4 canals. Most studies reported prevalence of a second canal (MB2) in 
the mesiobuccal (MB) root in over 50% of the cases. 
 

2 
 
Different cross-sectional tomograms, CT and lately, dental cone beam CT 
(CBCT) examinations have been used to study endodontic anatomy. (Gahleitner 
et al 2003 and Kiarudi et al 2015). 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

3 
 
Rational of the Study 
 
Prevalence of a second mesiobuccal canal in the mesial root of first and 
second maxillary molars is not clearly studied in Egyptian population. The 
prevalence rate will direct the attention of endodontists to its presence and will 
justify additional investigations to search for it. 
Statement of the Problem 
 
A high percentage of treatment failures is due to the impossibility of 
detecting the presence and location of the secondary mesiobuccal canal (MB2), 
located in the mesiobuccal root of the 1st maxillary molars and the 2nd maxillary 
molars (Blattner  et al 2010), which prevents the correct implementation of 
biomechanical instrumentation, irrigation and obturation (Fig. 1).  
 
 
Fig. 1 
Maxillary molar with 4 canals: first mesiobuccal canal (MB1), secondary mesiobuccal canal (MB2), 
distobuccal canal (DB) and palatal canal (P). A Maxillary molar with joining mesiobuccal canals. B 
Maxillary molar with two separate mesiobuccal canals (Betancourt et al 2016) 

4 
 
Its location in clinical practice is highly complex due to the excessive dentin 
deposited in the opening of the canal and to the difficulty in visually accessing 
maxillary molars. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

5 
 
Review of literature 
 
List of main databases used in search: 
- Pubmed  
- Google Scholar 
 Keywords: 
- Second mesiobuccal canal  -  CBCT  -  Prevalence  -  Population 
Maxillary first and second molars have been investigated because of their 
complex root and canal morphologies (Calis et al 1995; Ng et al 2001; Alavi et al 
2002; Sert & Bayirli 2004; Weng et al 2009; Degerness & Bowles 2010; 
Neelakantan et al 2010; Zheng et al 2010; Kim et al 2012; Rouhani et al 2014; 
Silva et al 2014). According to previous results, most maxillary first molars exhibit 
3 roots and 4 canals, including a mesiobuccal root with 2 canals and distobuccal 
and palatal roots with a single canal each (Zheng et al 2010; Neelakantan et al 
2010; Sert & Baiyrli 2004; Lee et al 2011; Badole 2014). 
Many studies investigated the morphology of the maxillary permanent 
molars focusing on the presence of a second mesiobuccal root canal in the mesial 
root (Pecora et al 1992; Sert & Bayirli 2004; Cleghorn et al 2006; Nikoloudaki 
et al 2015). They reported varying prevalence of the second mesiobuccal canal of 
maxillary first and second molars. Cleghorn et al 2006 found that the majority of 
maxillary first molars (95.9%) present 3 roots. The prevalence of a second 
mesiobuccal root canal in the mesial root varies between 26% (Pecora 1992) and 
93.5% (Sert & Bayirli 2004). Nikoloudaki et al 2015 attributed these variations 
to the different methods that were used. The prevalence of two canals in laboratory 
studies is higher (60.5%) to that reported in clinical studies (54.7%) (Cleghorn et 
al 2006). From the previous studies, Nikoloudaki et al 2015 concluded that the 
incidence of the second canal (MB2) in the mesial root is higher than 50%. 
Ferguson et al 2005 report the presence of a third canal in the mesial root. Christie 

6 
 
et al 1991 in a retrospective study reported a second canal in the palatal root. 
Badole et al 2012 found two individual palatal roots (mesiopalatal and distopalatal) 
with their own separate canals in one case. Tian et al 2016 found additional canals 
in first and second molars in a Chinese Population using CBCT in 67.8% and 29.7% 
of mesiobuccal roots. They found also that the mesiobuccal root canal number 
showed bilateral symmetry between 79% of first molars and 82.3% of second 
molars, with a concurrence rate of 59.8% between adjacent molars. 
Methods used to evaluate the inner morphology of a root:  
Numerous methods have been used to examine root and canal morphologies, 
including: 
 Histologic sections  
 Canal staining and tooth clearing (Ng et al 2001)  
 Sectioning (Weine et al 1969)  
 Conventional and digital radiography (Pattanshetti et al 2008, Silva et al 
2014) 
 In vitro macroscopic examination (ex vivo using extracted teeth) 
 Root canal treatment with magnification (Zheng et al 2010) 
 The modified canal staining and clearing technique (Weng et al 2009) 
 Computed tomographic imaging  
 Contrast medium–enhanced digital radiography (Neelakantan et al 2010-2) 
 Cone-beam computed tomographic (CBCT) imaging (Neelakantan et al 
2010, Kim et al 2012 and Rouhani et al 2014). 
Baratto Filho et al 2009 used three methods to evaluate the root canal 
morphology in maxillary first molars which are ex vivo, clinical, and cone beam 
computed tomography (CBCT) analysis and found that CBCT imaging was a useful 
diagnostic tool for this purpose as it can be used as a good method for initial 
identification of maxillary first molar internal morphology. It is also a non-

7 
 
destructive tool which offers a higher spatial resolution at lower effective radiation 
doses and lower costs compared with computed tomographic imaging. In addition 
it provides a 3 dimensional images of root canal morphology assessment. 
In vitro methodologies include various sectioning techniques (sectioning of 
the root perpendicular or vertically to the long axis of the tooth), root canal 
impression using low viscosity resin (Carns et al 1973), root canal staining, and 
tooth clearing as described by Vertucci 1984 and Barker et al 1969. A main 
drawback of these techniques is that the samples are irreversibly destructed, thus 
the results cannot be reproduced. 
Clinical studies can evaluate the incidence of additional canals under 
magnification using loupes or dental operating microscope and by analyzing 
clinical patients’ records or previously treated teeth (Stropko 1999). The above-
mentioned techniques are unable to reveal in detail the irregularities of the root 
canal system owing to their inherent limitations. Information gained by peri-apical 
radiographic images are limited due to superimposition of adjacent teeth and hard 
tissues of the oro-facial region. Three-dimensional anatomic irregularities can be 
missed due to the two-dimensional depicting potential and the possible geometric 
distortion of the image (Patel et al 2007 and Cotton et al 2007).  
Cone beam-computed tomography (CBCT) imaging techniques offer an 
effective way to overcome the above limitations .This is feasible by constructing 
detailed three-dimensional images of the teeth and the surrounding dental and 
alveolar structures. This information may be utilized for planning and intra-
operative guidance (Nikoloudaki et al 2015). 
Many studies analyzed the anatomic variations of maxillary molars using 
CBCT technology. Nikoloudaki et al 2015 reported on the root and canal 
configurations of maxillary permanent molars in Greek population. In addition, 
several articles have used cone beam computed tomography (CBCT) to study the 

8 
 
morphology of the maxillary molars and to ascertain its ability to visualize the 
second mesiobuccal canal (MB2). Betancourt et al 2016 have examined the 
geometric location in depth. They described in vivo the prevalence and location of 
the MB2 in the mesiobuccal root of the first maxillary molar (1MM) and the second 
maxillary molar (2MM) through CBCT imaging. In the 1MM protocol, the 
prevalence of the MB2 canal was 69.82% and was more frequent in women (p = 
0.005). They concluded that CBCT is a high-precision diagnostic tool for not only 
detecting but also locating in vivo the MB2 canal in the mesiobuccal root of upper 
molars. 
 
 
 
 
 
 
 
 
 
 
 

9 
 
Aim of the Study 
The aim of the study is to estimate the prevalence of a second mesiobuccal canal 
of maxillary first and second molars in Egyptian population. 
Population: Egyptian population 
Outcome Variable: Presence or absence of a second mesiobuccal canal of     
maxillary first and second molars 
 
 
Outcome 
Measured 
Measuring Device Measuring Unit 
 
 
Primary Outcome 
Presence of a 
second mesiobuccal 
canal of maxillary 
first and second 
molars 
 
CBCT Software 
 (On Demand 3D®) 
 
Binary System 
(Yes/No) 
Secondary 
Outcome 
Prevalence in the 
whole sample 
(females and 
males) 
 
 
Percentage 
 
Research question: 
What is the percentage of presence of a second mesiobuccal canal in Maxillary First 
and Second Molars among Egyptian Population? 
 

10 
 
Materials and Methods 
 
Study Design: Cross-sectional Study 
Setting and Location:  
1- The data collection will be obtained from the data base available at a private 
radiographic centre ORASCAN Oral & Maxillofacial Imaging Centre 
located in Cairo, Egypt. 
2- CBCT images will be obtained from Egyptian patients who had CBCT 
examination as part of their dental examination, diagnosis or treatment 
planning during the years 2015-16-17. 
Participants: 
A total of 196 CBCT scans of Maxillary first and second permanent molars 
belonging to Egyptian individuals will be included.  
Images of the first and second maxillary permanent molars are selected 
according to the following Inclusion criteria: 
 First and second maxillary permanent molars of Egyptian patients starting 
from 15 years, males or females 
 Intact roots without fractures or cracks 
 Molars without posts or previous root canal treatment 
 CBCT scans of maxillary first and second molars using 8 × 6 FOV, 0.2 voxel 
resolution 
Exclusion criteria: 
 Evidence of apicectomy or periapical surgery 
 Odontogenic or non-odontogenic pathology 
 Maxillary molars with developmental anomalies 

11 
 
 External or Internal Root resorption 
 Canal Calcification  
 Previous root canal treatment 
 Extensive coronal restorations 
 Posts or crown restorations 
 Root caries specially reaching the trifurcation area 
 Tomographic images of poor quality or artifacts interfering with the 
detection of root canals 
Variables:  
1. Number of root canals in mesiobuccal root of first and second maxillary 
molars 
2. Sex of the patient will be identified and addressed as the prevalence of the 
second mesiobuccal canal may show sex predilection 
Data Sources / Measurements: 
Retrospective Data Analysis will be performed after the CBCT images are 
pooled from the computer database. 
All the CBCT examinations were scanned using Cranex® 3D SOREDEX, 
0.2 voxel resolution, 8 × 6 cm FOV, 90 kVp, 10 mA and 6 seconds exposure time. 
CBCT images will be analysed in the 3 planes; first the sagittal and coronal 
sections will be oriented parallel to the long axis of the root, and then sections will 
be obtained on the axial plane for detection of the 2nd mesiobuccal canal 
(Betancourt et al 2016). 
CBCT images will be interpreted by three oral radiologists independently; 
blinded from demographic data of the patients and from the results of each other. 

12 
 
Each one will evaluate the images separately twice with a period of two 
weeks between the two reading sessions. 
Then inter-observational and intra-observational variability between the 
observers will be evaluated. 
The sex of the patient will be identified from the patient’s demographic data 
available on the patient’s file on the database of the private radiographic centre. 
Bias:  
No source of bias. 
Study Size: 
The aim of the study is to assess the prevalence of a second mesiobuccal 
canal of maxillary first and second molars in Egyptian population. Based on the 
previous paper by Nikoloudaki et al, 2015, the prevalence of Second Mesiobuccal 
Canal of Maxillary First and Second Molars was 89 and 85%. Using a precision of 
5, a design effect set at 1 with 95% CI (confidence interval), a total sample size of 
196 will be sufficient. The sample size was calculated by Epi info. 
Sampling Strategy: The sample will be collected by simple random 
sampling. 
Quantitative Variables: 
The number of CBCT scans of Egyptian individuals with second 
mesiobuccal canal will be counted to estimate the prevalence of the second 
mesiobuccal canal. 
 
 
 

13 
 
Statistical Methods: 
1- Data will be analysed using IBM SPSS advanced statistics (Statistical 
Package for Social Sciences), version 21 (SPSS Inc., Chicago, IL). Numerical data 
will be described as mean and standard deviation or median and range. Categorical 
data will be described as numbers and percentages. Comparisons between male and 
females for normally distributed numeric variables will be done using the Student’s 
t-test while for non-normally distributed numeric variables will be done by Mann-
Whitney test. Comparisons between categorical variables will be performed using 
the chi square test. A p-value less than or equal to 0.05 will be considered 
statistically significant. All tests will be two tailed. 
2- If the patient’s age couldn’t be found in the patient’s file, the dental age will 
be used. 
3- If the patient’s sex couldn’t be found in the patient’s file, the patient’s name 
will be used to indicate the sex. Patients with mixed name will be excluded. 
 
 
 
 
 
 
 
 
 

14 
 
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