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Three-Dimensional Cone-Beam Computed Tomography Assessment of Additional Canals of Permanent first Molars: A Pinocchio for Successful Root Canal Treatment

Aims and Objectives: The objective of this study was to estimate the prevalence of additional canals in the first permanent molars of the participants of Saudi, Jordanian, and Egyptian population using cone-beam computed tomography (CBCT). Materials and Methods: In this retrospective study, CBCT scans of 139 patients were collected who were implant treated at College of Dentistry, Al Jouf University, Saudi Arabia, from October 2016 to March 2017. The images were analyzed using On-Demand 3D software. A pilot study was done to prevent intra-examiner error, and two calibrated examiners independently assessed 20% randomly selected CBCT images. Gender and racial disparities were analyzed using Chi-square test. P <0.05 was considered statistically significant. Results: The prevalence of additional canal in U16, U26, L36, and L46 of Saudi population was 41.80%, 41.80%, 17.30%, and 19.10%, respectively. In Jordanian participants, no additional canals were found in both mandibular first molars whereas only one participant from Egypt had additional canal in both mandibular first molars. Moreover, significant associations were found between L36 (P = 0.015) and L46 (P = 0.008) with gender. Conclusion: In conclusion, the results of this study provide the information about the prevalence of additional canal in the first permanent molars, which will help and guide the clinicians while performing root canal treatment and also may help them increase the success rate of root canal treatment of the first permanent molars.


Introduction
R oot and root canal morphology plays the key role of successful outcome of root canal treatment therapy. During root canal therapy, canals could be left untreated if clinicians do not detect properly the presence of additional root canal in the tooth. [1] Therefore, clinicians need to be always conscious of the normal as well as abnormal anatomical or structural disparities in root canal morphology. Lack of consideration of the root canal morphology may result in unsuccessful treatment. Maxillary first molar is the largest tooth in size having the most complexity of root canal morphology. Thus, the failure rate of endodontic treatment is also high in the maxillary first molar tooth. [2] Commonly acceptable In dentistry, radiographs are one of the most important and reliable diagnostic apparatus of observation and determination of the oral structures. Especially in the field of endodontics, most of the diagnosis and treatment procedures are dependent on radiographic findings. [7] There are different types of radiographs such as conventional radiographs and digital radiographs and more recently computed tomography (CT), spiral CT, micro-CT, and cone-beam CT (CBCT) techniques by which we can detect and analyze the root canal morphology. [8] Tachibana and Matsumoto first introduced the use of CBCT in endodontic field in 1990. [9] CBCT is a cone-shaped beam of radiation and produces a three-dimensional (3D) image of the object which gives a clear idea about the object to the clinician. CBCT revealed itself as a reliable and efficient method to determine the root morphology compared with the gold standard of physical sectioning of the specimen. [9][10][11] In recent years, many studies have been done to determine the prevalence of additional canal in molar teeth in different populations worldwide. However, most of these studies indicate the prevalence of additional canal of one tooth. [2,7,8,[12][13][14][15][16] Kim et al. [17] observed 976 participants of the mandibular first molar and found that 50.36% of participants had additional canals. Recently, Zhang et al. [2] sectioned 1008 maxillary first molars and reported that 85.4% of the maxillary first molars had additional canal in the mesiobuccal root. A few studies have been conducted alike our study among Taiwanese and Chile people in very recently. [18,19] However, no study has been done three population together. We have, therefore, given particular attention to evaluating additional canals in mesiobuccal root (MB2) of all four permanent first molars using CBCT. Based on this, the prime objectives of this study were to: 1. Evaluate the prevalence of MB2 of U16, U26, L36, and L46 of Saudi, Jordanian, and Egyptian populations 2. Determine the prevalence of MB2 of U16, U26, L36, and L46 between males and females 3. Present the global data and present study of MB2 of the first permanent molar tooth. Written consent was taken from each patient before taking CBCT. In this retrospective study, we evaluated MB2 of the first molars from the CBCT scans of 139 patients who were treated at College of Dentistry, Al Jouf University, from October 2016 to March 2017. Identification of patients was not exposed, only the information (age, sex, and race) was provided. The samples were chosen using systematic random sampling technique. Among the sample group, 92 were male and 47 were female. In regard to race, 110 patients were Saudis, 15 Jordanians, and 14 Egyptians, with the age range of 34.42 ± 12 years (mean ± standard deviation).
If the absolute precision is 10%, the sample size required is 139. incluSion criteria 1. Age between 20 and 65 years old 2. Root formation has been completed. excluSion criteria 1. Metallic restoration 2. Intra-radicular post or endodontic filling 3. Rehabilitated using fixed prosthesis 4. Canal calcification, evidence of radectomy, or periapical surgery 5. Maxillary molars with developmental anomalies.

three-dimenSional aSSeSSment of mb2 in firSt molarS
The carefully chosen 139 images were analyzed using On-Demand 3D software [ Figure 1].

StatiStical analySiS
Data were statistically analyzed using IBM Statistical Package for the Social Science (SPSS), Version 22.0 (SPSS, Chicago, IL, USA). Gender disparities and racial disparities were analyzed using Chi-square test. P < 0.05 was considered statistically significant. a b Figure 2: Distribution of additional canal in the maxillary first permanent molar according to gender A pilot study was done to prevent intra-examiner error. Randomly selected 20% CBCT images were evaluated by two researchers, 2 weeks after the initial survey to determine the reliability of diagnosis of MB2. Kappa statistics were used to determine intra-and inter-examiner agreements. There was 100% intra-and inter-examiner agreement between the investigators.

error of the Study
Intra-class correlation coefficients were performed to assess the reliability of the measurements, and the coefficients of reliability of the measurements were between 0.91 and 0.98.  Table 2]. No significant associations were found among races in all molars. Figure 2 shows the distribution of MB2 in the maxillary first permanent molar according to gender. Significant associations were found between L36 (P = 0.015) and L46 (P = 0.008) between males and females. However, there was no significant association found between upper first molars.

Discussion
In this study, we analyzed CBCT images which is one of the most recent radiographic methods by which we can procure 3D images of an object with a relatively lower dose of radiation.    In a study, Oboro-Onuora et al. [12] analyzed the presence of additional canal in Nigerian population. Among 50 participants, they found that 34% of patients had MB2 in U16 and U26. Not only that, they also confirmed in in vitro study and finally concluded that the incidence of additional canal is comparatively higher in their population than the previous study. Studies performed in different populations demonstrate that the presence of additional canal is common phenomenon.
Anatomical variation in the root morphology of molar teeth is quite common in dentistry. Especially in the field of endodontics, knowledge of anatomic variations and detection of additional root canal are must for satisfactory treatment outcome because untreated root canal leads to the treatment failure. A canal may be left untreated due to the lack of proper identification of its presence. Most of the previous studies have been done by analyzing only single tooth or single jaw like only the upper molars or the lower molars. Zheng et al. [8] found that more than 50% of participants had MB2 in U16 and U26 in a Chinese population study. Guo et al. [13] revealed that 68.2% of participants had MB2 in U16 and U26 in a North American population study. Similar results were reported by Peeters et al. [14] in an Indonesian population. They also found that 68.8% of participants had MB2 in U16 and U26. However, our results showed that 41.8% and 33.3% of participants had MB2 in U16 and U26 in Saudi and Jordan, respectively. On the other hand, among the Egyptian participants, 35.7% showed MB2 in U16 and only 1% showed MB2 in U26. Another study done on Saudi subpopulation found that 55.6% of participants had MB2 in U16 and U26. [15] Regarding the mandibular first molars, in an Indian population, 36% of participants showed MB2. [16] In our study, percentage of the presence of MB2 is comparatively low. However, the prevalence of MB2 in our study was higher on maxillary first molars than mandibular first molars among all the three populations. Similar findings were reported by Kim et al. [20] Their results also revealed the higher prevalence of MB2 in the upper first molars like our study. Table 4 shows the prevalence of MB2 in different population groups. In this study, the presence of MB2 was higher in males compared to females [ Figure 1]. However, significant association was only found in the mandibular first molars L36 (P = 0.015) and L46 (P = 0.008) between males and females. However, a study done in the South Korean population reported no significant association in the mandibular first molars between males and females. [20] Similar findings also reported by Zhang et al. [2] On the  [13] North American CBCT U16, U26 Additional canals are detected 68.2% Peeters et al., 2011 [14] Indonesian Clearing U16, U26 Additional canals are detected 68.5% Al-Shehri et al., 2017 [15] Saudi CBCT U16, U26 55.6% of participants had additional canal Chourasia et al., 2012 [16] Indian Clearing L36, L46 36% of participants had additional canal Kim et al., 2013 [17] South  [21] found the difference between males and females; the presence of MB2 was higher in males compare to females in Pakistani population.
In a prospective study, larger sample size would deliver better depth to the current hypothesis and results which might provide clinicians a better understanding about the presence of additional canal in the first molar teeth and on root canal treatment of these teeth. More longitudinal studies including participants from several institutions are also recommended to issue standardized guidelines.

financial Support and SponSorShip
Nil.

conflictS of intereSt
There are no conflicts of interest.