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Prevalence and Morphology of MB2 Canals in Maxillary Molars by Cone Beam Computed Tomography (CBCT) and Rate of Treatment in Endodontic Practice with Pre-operative CBCT Images

I-Ping Chen, Do Hyeon Kim, Bruce Cha, Jin Jiang
Published: 19 August 2020
Modern Research in Dentistry , Volume 5, pp 506-512; doi:10.31031/mrd.2020.05.000614

Abstract: Do Hyeon Kim1, Bruce Cha2, Jin Jiang2 and I-Ping Chen2* 1Private Practice, Bridgeport, CT, USA 2Department of Oral Health and Diagnostic Sciences, School of Dental Medicine, University of Connecticut Health, Farmington, CT, USA *Corresponding author: I-Ping Chen, D.D.S., Ph.D., Associate Professor, University of Connecticut Health Division of Endodontology, Department of Oral Health and Diagnostic Sciences, 263 Farmington Avenue Farmington, CT 06030-3705, USA Submission: July 28, 2020;Published: August 19, 2020 DOI: 10.31031/MRD.2020.05.000614 ISSN:2637-7764Volume5 Issue3 Thorough understanding of root canal anatomy is a prerequisite for successful endodontic treatment. The failure of root canal treatment of maxillary molars is highly associated with missing the second mesiobuccal (MB2) canals. Aim: we aim to assess the prevalence and morphology of MB2 canals of first (1st) and second (2nd) maxillary molars based on CBCT images. We further compared the treatment rate of MB2 canals to the rate identified from CBCT imaging analysis. Methodology: Pre-operative CBCT images of 400 maxillary 1st molars and 264 maxillary 2nd molars in a cohort of 661 subjects were examined. Parameters studied were: Result: 99% of maxillary 1st and 89.77% of 2nd molars had three separate roots with 2nd molars showing higher morphological variability. MB2 canals were found in 77% of maxillary 1st molars and 46.9% of 2nd In 3-rooted molars, the most common Vertucci classifications for MB canals in 1st molars were Type II (37.63%) and in 2nd molars Type I (47.26%). When MB2 orifices were not at the pulpal floor level (~50% of cases), the average distance below the pulp floor was 0.94mm in maxillary 1st molars and 0.92mm in 2nd molars. Clinically, the rates of MB2 canals being treated of 1st and 2nd molars were 67% and 37.8%, respectively. With MB2 identified in CBCT images, 86.6% were obturated in maxillary 1st and 80.64% in maxillary 2nd molars. Conclusion: Despite the resolution limit, CBCT remains a widely accepted non-destructive tool to study canal morphology and is readily available to many endodontists. When it is beneficial to patients and cost or radiation exposure is not a concern, pre-operative CBCT images should be thoroughly analyzed before treatment to ensure treatment quality and to limit iatrogenic complications. Keywords: CBCT imaging; MB2 canals; Maxillary molars; Fused roots The morphology of maxillary molars has been extensively studied, particularly the prevalence of a second mesiobuccal (MB2) root canal. Despite of this effort, the high failure rate of root canal treated maxillary molars remains tightly associated with untreated MB2 canals. There is a significant increase in the incidence of MB2 canals in retreatment cases, suggesting that these canals are frequently missed in the initial treatment [1]. Moreover, maxillary 1st molars with missed MB2 canals were 4.38 times more likely to be associated with a periapical lesion and, surprisingly, MB2 canals were unfilled in almost half of endodontic cases (46.5%) [2]. To maximize the success rate of root canal treatment, it is important for endodontists to be aware of anatomic variations. Since the first report of MB2 canals in maxillary molars in 1925 [3], the prevalence of MB2 canals has been examined by many techniques, which may explain the variable results between studies. Some commonly used methods include clearing and staining of extracted teeth [4], various sectioning techniques [5,6], conventional/digital radiographs [7,8], root canal treatment under microscope in vitro [9], and micro-computed tomographic imaging [10]. The incidence of MB2 canals in the literature ranges from 18-96% [11]. Studies using clearing and staining techniques of extracted teeth revealed that more than 90% of maxillary molars have multiple canals in MB roots [12,13]. On the other hand, clinical studies reported lower incidence (18-73%) of MB2 canals [14-16]. Such discrepancies could also be attributed to different selection criteria of sample population, such as ethnic background or age. Numerous studies have been conducted to establish a reliable and efficient clinical method to help locate MB2 canals [16-18]. In recent years, 3-dimensional cone-beam computed tomography (CBCT) has been used for identifying root canal configurations [10,19,20]. It can confirm the presence of MB2 canals as well as locate and orient a canal in relation to MB1, distobuccal, and palatal canals [19,21]. As a non-destructive tool, CBCT imaging offers not only high-resolution images in all spatial planes with minimal distortion but also reconstructs the volumetric images [22,23]. The aim of this study is to investigate the root and canal morphology of maxillary 1st and 2nd molars based on pre-operative CBCT images and associate the MB2 detection rate of CBCT with those being treated in clinic. Subjects The protocol of this study was approved by the Pearl Institutional Review Board, Indiana, USA (19-KIM- 101). The study included pre-operative CBCT images of 400 maxillary 1st and 264 maxillary 2nd molars taken from 661 subjects between August 2014 and March 2019 for diagnostic purposes. The number of CBCT scans to be included in the study was determined by a power analysis using a sample size calculator ( with a significant level of 0.05 and 99% power. Inclusion criteria for CBCT images were as follows: Pre-operative evaluation of CBCT images CBCT images were taken with a Carestream CS 9000 3D (Carestream Dental, Atlanta, GA) using the following parameters: 70kVp, 10mA, 10.8 second exposure time, 76mm voxel size, and 50mm x37mm scan field of view. Images were viewed with a 27-inch monitor (Samsung T27B350ND) at a screen resolution of 1920x1080 and luminance of 300cd/m². Serial sagittal, coronal, and axial views of CBCT images were evaluated. In axial view, the axis of slicing was rotated to intersect with the long axis of the root. The presence of additional...
Keywords: Treatment / canals / molars / Mb2 / Beam Computed Tomography / Cone Beam Computed

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