Prevalence of mesiobuccal 2 canal in first maxillary molar: A retrospective radiographic study

Finding two mesiobuccal root canals named MB1and MB2 in maxillary first molar is not uncommon. Mesio-buccal-2 (MB2) canal orifice located palatally to the mesio buccall orifice and buccally as well as mesially to palatal orifices. A complete understanding of MB2 root canal morphology can contribute to the successful outcome of root canal treatment. This study conducted on CBCT scans with age ranged from 15 to 60 years which was further divide into group I (15-30 years), group II (30-45 years) and group III (45-60 years). Unilateral as well as bilateral prevalence of MB2 canal in maxillary first molar in both the genders and prevalence of MB2 canal in maxillary first molar in accordance with age were determined. Results showed overall prevalence of MB2 canal in maxillary first molar was 60.7%. In age wise distribution, group II showed greater prevalence than group I and group III showed least prevalence than others. The results were statistically significant between age groups. There was no statistical significance obtained between gender and quadrant wise. Conventional diagnostic aids such as radiographs play an important role in assessment of complex root canal morphologies. These modalities, however, do not provide detailed information of the complexity as a result of their inherent limitations. Shifting from 2D radiographic techniques to 3D radiographic techniques provides better visualization and location of these small and difficult structures. © This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Introduction
Root canal therapy is one of the routinely carried out procedure in dentistry applicable on teeth with irreversible pulpitis and periapical pathologies in order to preserve the natural dentition. A detailed knowledge and awareness of complex anatomy of the root canals is utmost important for success of endodontic treatment. 1 Amongst all the causes of root canal treatment failures for example inadequate canal debridement due to anatomical complexities and canal preparation, the failure to locate the accessory canals also leads to unfavorable treatment.
The maxillary first molar teeth usually possess a great anatomical variation in terms of number of root canals, size and shape of canal. Very often an accessory root canal is present lingual/palatal to the mesiobuccal canal of theses molar, which is commonly not negotiated by practioner may further lead to root canal treatment failure. This canal is known as the mesiolingual canal of the mesiobuccal root, mesiopalatal canal, or MB2. 2 The presence of such root canals was first reported by Hess in 1925. 3 Christie WH (1991) and Fogel HM (2017) reported variation in distobuccal root canal and palatal canals of maxillary molars. 4,5 According to Witherspoon DE (2013), 44% of retreatment in maxillary first molars is due to missed canals and 93% of these missed canals are identified in the mesiobuccal-2 root canal. 6 Cone beam computed tomography (CBCT) imaging is an invaluable radiographic modality which shows the root canal system in three dimensions with superior contrast and resolution compared to 2D radiographic techniques. It provides better understanding of anatomical complexities and guides the clinician to more efficient treatment procedures.

Aim
The aim of this retrospective radiographic study is to estimate the prevalence of MB2 canal in maxillary first molar in both the gender and in different age groups using cone beam computed tomography (CBCT) images in North Indian population.

Objectives
The objective of this study is to investigate the following features using Cone Beam Computerized Tomography:-1. Unilateral as well as bilateral prevalence of MB2 canal in maxillary first molar in both the genders. 2. Prevalence of MB2 canal in maxillary first molar in accordance with age.

Materials and Methods
This retrospective radiographic study conducted on 135 patients (73 males and 62 females). Their CBCT scans were obtained by Kodak CS 9300 digital imaging system (Tube Focal spot-0.7mm,Tube Voltage-60-90 Kvp Tube Current (mA)-5-15mA). The age of patients ranged from 15 to 60 years which was further divide into group I (15-30 years), group II (30-45 years) and group III (45-60 years), they were subjected to various measurements in cognizance with objectives of the study. The inclusion and exclusion criteria were defined as follows:

Inclusion criteria
Patients above the age of 15 years with healthy maxillary permanent first molar teeth on both sides. The maxillary first molars with complete root formation.

Exclusion criteria
Maxillary first molar with developmental anomalies, open apices, root fractures, internal or external resorption and pulp calcifications.
The floor of the pulp chamber of maxillary first molar was first determined in sagittal section. By using liner measurement tool of the CBCT software, a 2mm line drawn from the floor towards apical end. The axial section 2mm below the pulpal floor was taken as standardize observation point of the MB2 canal and presence or absence of MB2 canal was then noted in the axial view (Figures 1, 2 and 3). This geometric position was according to the protocol described by Gorduysus et al. 7 and Betancourt et al. 8 The data was correlated with age, gender and side. For suitable and appropriate statistical analysis, SPSS version 16.0 has been used. A 5% level of significance has been chosen and the p-value of less than 0.05 has been considered as statistically significant and less than 0.001 has been considered as highly significant.

Results
This study showed the prevalence of MB2 canal in different age groups. Out of total 135 scans, 82 patients (45 males and 37 females) showed presence of MB2 canal in maxillary first molar. The overall prevalence of MB2 canal in maxillary first molar was 60.7%. In age wise distribution, group I showed 57%(22), group II showed 66% (43) and group III showed 53% (17) prevalence of MB2 canal (Table 1). There results were statistically significant between age groups.
Gender wise unilateral and bilateral presence of MB2 canal in maxillary first molar showed that in males, bilateral MB2 canal in 17(37.7%) cases and unilateral in 28(62.2%) cases and in females, bilateral MB2 canal in 14(37.8%) cases and unilateral in 23(62.1%) cases. Side  wise distribution showed that right side had greater number of MB2 canal than the left side in both the gender. There were no statistical significance obtained between gender and quadrant wise.

Discussion
The results of our study indicated that CBCT helps clinician to better understand the morphological variations of root canal due to its high diagnostic accuracy and thereby increasing the chances of endodontic treatment success. Our study reported statistically significant results between age groups and the prevalence of MB2 canal in maxillary first molar was 60.7%. The prevalence obtained by Kewalramani R (2019) 9 was 61.9% which was similar to our study. In contrast, Neelakantan P et al. 10 9 in which group<20 years(50.6%) and>40 years(57.5%) showed less prevalence compared to 20-40 years(67.4%). The low prevalence in age group I can be due to presence of single wide mesiobuccal orifice. In age group III, decreased prevalence was observed in our study and it may be due to obliteration of canal because of secondary dentine formation leading to dentinal sclerosis and pulpal recession. The results were also consistent with the studies of Reis et al. 13 and Lee et al. 14 Our study findings suggest that in patients within the 30-45 age group requires attention in negotiating MB2 canal by careful troughing and magnification but not beyond the furcation.
In our study, there were no statistical significance obtained between gender and quadrant wise, although side wise distribution showed that right side had greater number of MB2 canal than the left side in both the gender. The prevalence of MB2 canal was 92% for permanent first maxillary molar teeth in the first quadrant, 87% for permanent first maxillary molar teeth in the second quadrant in both gender in a study done by Fernandes NA (2019) 15 and also did not show a significant association between patient gender. Similar studies in the literature showed same results. 13,16

Conclusion
Root canal morphology is commonly assessed on periapical (PA) radiographs which is a 2D radiographic modality and hence provides inadequate visualization of presence of extra canals, such as MB2 which leads to incomplete treatment and symptoms of pulpal infection remains even after root canal treatment of the tooth. CBCT reveal more accurate internal anatomy of root canals especially MB2 canals which can be easily neglected by clinician in two dimensional radiography.

Source of Funding
None.

Conflict of Interest
The authors declare that there is no conflict of interest regarding the publication of this article.