Journal of Indian Academy of Oral Medicine and Radiology

: 2021  |  Volume : 33  |  Issue : 3  |  Page : 242--247

Prevalence and morphological assessment of bifid mandibular canal using cone beam computed tomography among a group of yemeni adults

Nabil Qaid, Abdulwahab Aldilami, Khaled AL-Jawfi, Anas Shamala 
 Department of Preventive and Biomedical Science, Faculty of Dentistry, University of Science and Technology, Sanaa, Yemen

Correspondence Address:
Dr. Anas Shamala
Department of Preventive and Biomedical Science, Faculty of Dentistry, University of Science and Technology, Sanaa


Objectives: The study aimed to assess the prevalence and morphology of bifid mandibular canal (BMC) using cone beam computed tomography (CBCT) among a group of Yemeni adults. Materials and Methods: The presence and type of BMC were evaluated among 400 CBCT images. Prevalence rate of BMC was also determined according to gender. Further, the diameter and length of BMCs were measured using Ez3D plus software. Chi-square analysis and the analysis of variance (one-way ANOVA) were used. Results: The study concluded that BMCs were found in 60 (15%) of total cases. There was no significant correlation between gender and BMC prevalence. Forward BMC was the most common type (48.3%), followed by retromolar BMC (35.0%) then dental BMC (16.7%); while not even one case of buccolingual BMC was observed. There was a significant difference in the mean diameter of BMC (P value = 0.016). There was a significant difference in the mean length of BMC (P = 0.001). Conclusion: The prevalence of BMCs in Yemeni adults is relatively high, and forward BMC was the most common type. Detecting BMCs by using CBCT imaging is highly recommended prior to any mandibular surgery.

How to cite this article:
Qaid N, Aldilami A, AL-Jawfi K, Shamala A. Prevalence and morphological assessment of bifid mandibular canal using cone beam computed tomography among a group of yemeni adults.J Indian Acad Oral Med Radiol 2021;33:242-247

How to cite this URL:
Qaid N, Aldilami A, AL-Jawfi K, Shamala A. Prevalence and morphological assessment of bifid mandibular canal using cone beam computed tomography among a group of yemeni adults. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Nov 29 ];33:242-247
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Full Text


The Mandibular canal (MC) is a bilateral bony canal. Its origin starts in the mandibular foramen and passes downward in the ramus of the mandible, then directs anteriorly toward the mental foramen.[1] MC is present as a single canal in most individuals. But it may vary according to the shape (oval, round, or pear-shaped) and may also present as double or bifid MCs in some individuals, so it could be identified radiographically.[2]

The term “bifid” is a Latin word that implies the separation of the object into two parts or branches. The bifid mandibular canal (BMC) originates at the mandibular foramen or in any area in the mandibular ramus or even in the mandibular body. In addition, each of BMC have detached neurovascular bundles.[3] BMC is considered as a relevant anatomical variation that may be injured during the surgical procedures in the posterior mandible, including the extraction of lower third molars, dental implants placement, and osteotomies.[4],[5],[6],[7],[8]

There are many imaging techniques available to identify the MC and its variation, such as conventional panoramic radiography, multi-slice computed tomography (MSCT), and cone beam computed tomography (CBCT).[9] CBCT imaging is an excellent diagnostic technique that gives a better observation of the diameter and accurate direction of BMC particularly in the bucco-lingual position because it provides 3D images with high resolution and does not cause any overlap of the adjacent structures, deformations, and superimposition accompanied with 2D conventional radiography imaging.[10],[11]

Considerable studies were conducted in different countries for evaluating the prevalence of BMCs in different countries, ethnics, sampling methods, several systems of radiographs resolution, and interpretation of images, ranging from 2.7 to 65%.[12],[13],[14],[15],[16],[17],[18] Several authors have studied different anatomical aspects and pathways of BMCs. Furthermore, they documented the classification with respect to the differences of BMCs. [12],[19],[20]

Up to the authors' knowledge, no study published showed the BMC prevalence and morphology within Yemeni people. The present study aimed to assess the prevalence, morphology, types, diameter, and length of BMC among the Yemeni sample. In addition, gender and age-related anatomical variations was also assessed.

 Materials and Method

Study sample

It was a cross-sectional retrospective study. The sample was taken from the database of a private radiology imaging center at Sana'a city, Yemen. The center was selected because of the availability of complete patients' records, and the staff performing the scans at that center were well trained.

The images were taken by a CBCT system unit (PaX-Flex3D P2, Vatech, Korea). CBCT images were taken from 500 patients who had visited the center within a time interval between January 2012 and December 2018 for diagnostic purposes.

Sample size estimation

The minimum sample size was calculated as 281 power of 80% alpha level of P = 0.05. The final sample size was 400 CBCT images considering prevalence of 5% and a 95% level of confidence using the OpenEpi sample size calculator (Open Source Epidemiologic Statistics for Public Health, USA).

Ethical approval

Prior to the study, ethical approval to carry out this study was granted from the ethical committee of the Faculty of Medicine and Health Sciences, University of Science and Technology (MECA No.: EAC/UST148) in accordance with the declaration of Helsinki.

Inclusion and Exclusion criteria

Inclusion criteria included bilateral and unilateral mandibular images of male and female adult patients; CBCT images of patients aged between 18 and 70 years old; with high quality that are easily diagnosed; and full view of MC from the ramus area to the premolar area (FOV = 13 cm). Whereas exclusion criteria included CBCT images of patients aged <18 and >70 years of old; with pathologic lesions or congenital malformations in the posterior mandible; or history of craniofacial malformation, syndrome, trauma, orthognathic surgery, and presence of any lesion in the retromolar area, severely atrophied mandibular arch, and false BMC.

Evaluation of the BMCs classification using CBCT images

BMCs were classified consistently by two observers according to the classification of Naitoh et al. (2009)[19] into four types based on the origin site and the direction of bifurcated canal from the main mandibular canal (MMC) as follows: Forward BMC in which the branch arises from the superior wall of the main canal; Buccolingual BMC in which the branch arises from buccal or lingual wall of the main canal; Dental BMC in which the end of the bifurcated canal reaches the root apex of the molars; and Retromolar BMC in which the branch arises from the main canal, opening at the retromolar foramen.

Measurements of length and diameter of BMCs

Measurements of BMC lengths were conducted on the two sides of the MC. It was measured in mm on the sagittal view [Figure 1], starting from the point of the BMC bifurcation from MMC to the point where the clarity of bifid canal had been diminished.[11] The measurements used EZ3D Plus Software of CBCT system through two measurement methods.[11],[14],[20],[21]{Figure 1}

The methods were to draw a curved line along the curved canal, which harmonized with the curvature of the curved bifid canal without making any multiple points or with the polygonal lines by creating a curve specified by a sequence of multiple points along the curved bifid canal. The curve consists of the line segments connecting the consecutive vertices. The diameters of BMCs were measured on the cross-sectional image through the coronal plane [Figure 2], immediately at the widest portion of the BMC.[11]{Figure 2}

Reliability of measurements

To verify the accuracy of measurements of BMCs, a comparison was conducted between the first measurement and the second measurement to determine the inter-examiner reliability of measurements using Alpha Cronbach's coefficient [Table 1].{Table 1}

Data collection and statistical analysis

After data entry, they were statistically analyzed by the Statistical Package of Social Science (SPSS) (version 22) for statistical analysis. Significant differences in the prevalence rate of BMCs according to gender were evaluated by a Chi-square test. The measurements of BMC including mean and diameter were examined using analysis of variance (ANOVA). Differences were considered significant when the P value is < 0.05.


The study evaluated MCs of 400 CBCT images among Yemeni patients [Males = 238 (59.5%), Females = 162 (40.5%)] [Table 2]. The mean age was 49 years (SD ± 12.2). Out of the 400 CBCT images, the BMCs observed in males were 40 (10%), which were higher than those observed in females, 20 (5%) [Table 3]. The highest frequency of BMCs was observed in the age group between 51 and 60 years' old which contained 23 BMCs (5.75%), followed by the age group between 41 and 50 years old that contained 14 BMCs (3.5%). Whereas the lowest frequency was observed in the age group between 31 and 40 old years that contained 7 BMCs (1.75%) [Table 3].{Table 2}{Table 3}

There was no statistically significant correlation between the prevalence of BMCs with respect to gender (P value = 0.22) [Table 4]. [Table 5] shows that the most common type of BMCs was the forward BMCs representing 48.3% (n = 29) of the total BMCs [Figure 3] and [Figure 4].{Table 4}{Table 5}{Figure 3}{Figure 4}

Out of the 29 forward BMCs, 21 BMCs were bifurcated in the ramus area and 8 BMCs in the mandibular body, below the third molar region. All of them were bifurcated from the superior border of the MMC and continued as dependent canals without confluence with or rejoining the MMC.

Of the total 10 dental BMCs [Figure 5], 3 BMCs extended to the root apex of the first molars and 7 BMCs extended to the root apex of the second molars. All the 21 retromolar BMCs were bifurcated from the MMC in the mandibular ramus area and opened into the retromolar foramen in the retromolar area [Figure 6].{Figure 5}{Figure 6}

The mean diameter of BMCs was 2.08 ± 047 mm, whereas the mean diameters of BMC types the forward, dental, and retromolar BMCs were 2.17 ± 0.47 mm, 2.29 ± 0.48 and 1.85 ± 0.38, respectively [Table 6]. There was a statistically significant difference regarding the diameter of each type of BMCs (P value = 0.016).{Table 6}

The mean length of BMCs was 13.3 ± 10.66 mm, whereas BMC types [Table 6] were illustrated as follows: The mean lengths of the forward, dental, and retromolar BMCs were 18.30 ± 3.23 mm, 8.46 ± 2.05 mm, and 8.25 ± 2.26 mm, respectively. There was no significant difference regarding the lengths of the retromolar and dental BMCs. However, there was a statistically significant difference between the mean length of forward BMCs and the lengths of dental and retromolar BMCs (P value = 0.001).


The main reason for conducting this research was because there were no previous studies that have been conducted on the Yemeni population according to the read-through of data archived in the records of the national library. Therefore, this study can be used as a guide to provide primary information about the anatomy of MC and its variation as BMC. The other reason was because the number of practitioners with limited experiences who carry out dental implant surgeries has increased significantly over the last 7 years. Moreover, such practitioners would accept more complex cases which consequently is expected to increase surgical complications.

Comparing between the anatomical and radiographic investigations, some authors believed that the panoramic radiographs underestimate the prevalence of BMCs and anatomical variations.[22]

Identification of BMCs using panoramic radiography is difficult by ghost shadows formed by the opposing semi-mandible, and overlapping with pharyngeal airway, soft palate, and uvula.[19] Moreover, the false image could be observed because of sclerotic lines caused by the insertion of the mylohyoid muscle into the lingual surface of the mandible.[23] Another factor that could mislead the diagnosis of a BMC is the presence of a dense trabecular structure around it.[24] Unlike panoramic radiography, CBCT can provide a multi-planar image suitable for identifying the BMC, without a ghost image and false appearance of the BMC.[25] It was reported that CBCT is considered as a suitable modality for detailed evaluation of BMCs.[26]

On the one hand, there are several studies that evaluated the anatomical location and configuration of BMC using panoramic radiography. They reported that the BMCs prevalence rates represented 0.95%, 0.08%, 8.3%, 0.08%, and 0.4%, respectively.[3],[27],[28] On the other hand, there are also several studies that evaluated the BMCs prevalence using CBCT imaging including those conducted by Orhan et al., Rashsuren et al., Naitoh et al., Zhang et al., Kuribayashi et al., Sisman et al., and Yang et al.[1],[10],[19],[20],[26],[29],[30],[31] They reported that BMCs prevalence rates represented 15.6%, 65.0%, 26.7%, 46.5%, 30.6%, 22.6%, 26.7%, 31.1%, and 13.2%, respectively. Therefore, studies that used CBCT imaging revealed higher rates of BMCs prevalence than those that used panoramic radiography, indicating that the conventional panoramic radiographs may be unreliable in identifying the tiny anatomical variations.

When comparing the findings of the previous studies which used CBCT imaging with the findings of the current study, the rate of BMCs prevalence in the current study was 15%. It was higher than that of Zhang et al. (13.2%)[20] and Nithya and Aswath (10.3%),[6] relatively similar to that of Naitoh et al. (15.6%),[19] and less than that of other studies (65.0%, 26.7%, 30.6%, 22.6%, 40%, 46.5%, 26.7%, and 31.1%, respectively.[1],[5],[10],[26],[29],[30],[31],[32]

Furthermore, the current study revealed that there was no significant difference in the prevalence of BMCs with regard to gender which is similar to those recorded by previous studies.[1],[5],[8],[19],[20],[25],[30],[31],[33],[34] Besides, the forward BMC was found to be the most common type of BMCs. This finding is similar to those reported by other studies.[1],[5],[19],[31],[35]

In the present study, no buccolingual BMCs were detected. This result coincides with those reported by other studies,[11],[20] but the current results are not in line with other studies that reported incidence of 9.7% and 14.3%, respectively.[5],[6] BMCs, especially retromolar and dental BMCs are clinically important. Therefore, when using the retromolar region as a donor site for harvesting a block graft or mandibular bone augmentation, determining the retromolar BMC is largely important prior to harvesting the block graft from the retromolar region. In addition, identifying the dental canal clinically is very important prior to dental implant placement in molar areas or in cases of over instrumentation during root canal treatment in the posterior teeth.[19]

The present study concluded that the mean diameter and mean length of BMCs were 2.08 ± 0.47 mm and 13.3 ± 10.66 mm, and there were statistically significant differences regarding the diameters and lengths of BMC types. These results were relatively in line with those reported by previous studies.[11],[19],[25],[32],[35] In addition, the study found that the mean lengths of the dental and retromolar BMCs were significantly shorter than that of the forward BMCs. This result was similar to that reported by another study.[25] No trifid canals were detected in the current study that they in line with reported studies by a previous study,[6] On the other hand, the present study is in disagreement with a previous study[5] that revealed as the trifid canal was (2.4%).

Limitations and future prospects

The sample size was limited and taken only from one of the three X-ray centers in Yemen due to the incomplete availability of patients' records in the other two radiology centers. In addition, the lack of extensive experience of the observers in may have made errors in the identification and measurement of the study variables. However, training obtained from one of the observers from the manufacturer (PaX- Flex3D P2, Vatech, Korea) may have resulted in the minimization of potential random measurement errors.

There is a need to do further studies utilizing a larger sample size that should be taken from different study areas to evaluate the BMC prevalence using an advanced imaging modality (CBCT imaging), and to study the anatomical features of BMC and its relationship with the third molar. In addition, a prospective clinical study needs to be conducted to investigate the genetic predisposition and the correlation of radiographic data with the clinical findings during/after performing the surgical procedures on the mandible.


It may be concluded that the prevalence of BMCs among a group of Yemeni adults was relatively high (15%). No statistical correlation was found between the prevalence of BMCs and gender. BMCs were detected more frequently in males than females. The forward BMC was the most common type of BMCs, followed by retromolar and then dental BMCs. Detecting BMCs by using CBCT imaging is highly recommended prior to any mandibular surgery.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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