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This CBCT‐based study analysed morphometric relationships in Mesio‐Buccal (MB) roots of maxillary first molars (MFM). 133 MFM with two MB canals were assessed and classified using Vertucci's classification. MB roots' length and MB1‐MB2 canals inter‐orifice distances (IOD) were noted. The data were analysed using SPSS software. The most frequently present canal was type IV (59.4%) followed by type II (40.6%). Mean MB roots' length for canals exhibiting type IV was 9.26 ± 0.21 mm and of those exhibiting type II was 12.8 ± 0.42 mm. Statistically significant relationship was found between MB root length and canal type. Mean IOD for type II and type IV canals was 2.4 ± 0.47 and 3.8 ± 0.21 mm, respectively. Statistically significant relationship was found between IOD and canal type. Length of MB root and IOD had a significant association with canal type present in MFM. This knowledge can enhance clinicians' understanding of canal morphology which can increase predictability and success rate of endodontic treatment. [ABSTRACT FROM AUTHOR]

Cone‐beam computed tomography scans exhibiting a second mesiobuccal (MB2) canal were examined. The vertical distance of the MB2 orifice from the pulp floor (depth), inter‐orifice distance (IOD) of MB2 from mesiobuccal (MB) and palatal (P) orifices, the horizontal distance of the MB2 orifice from the line joining MB‐P orifices [mesial deviation (MD)] and root canal configuration (RCC) were evaluated on 330 scans. The Student's t‐test, ANOVA, Spearman's correlation and linear regression analysis were applied. The MB2 depth was 1.69 ± 0.86 mm. IOD (MB‐MB2, MB2‐P) was 2.18 ± 0.58 mm and 4.63 ± 1.06 mm, respectively. MD was 1.02 ± 0.37 mm. The predominant RCC was Vertucci's type II (75.5%). No correlation of depth with IOD of MB‐MB2 (rho = 0.0367, p = 0.506) was observed. Significant correlation of depth with IOD of MB2‐P (rho = 0.696, p < 0.001) and MD (rho = 0.174, p = 0.001) was established. No association of depth with age and IOD (MB‐MB2) was observed on linear regression analysis. However, a significant positive association was established with IOD (MB2‐P) (p < 0.001) and MD (p = 0.001). [ABSTRACT FROM AUTHOR]

We have experimentally investigated granular flow through a quasi-two-dimensional hopper with two symmetric outlets on a flat bottom. The relationship between the flow rate and inter-orifice distance, namely the spacing between two outlets, for the whole range of outlets studied, is well described by an empirical equation we have presented. We have also measured the velocity and packing density profiles in the flow of particles above the outlets. We find that the packing density has a small fluctuation with respect to the inter-orifice distance, which may be considered as a constant based on zero order approximation. On the assumption of continuous flow and a constant packing density, we prove that the relation between the flow rate and the inter-orifice distance is mainly attributed to the velocity above each outlet, which is affected by a repulsive interaction between two outlets. [ABSTRACT FROM AUTHOR]

Background: Failure rates in endodontic treatments are presented in greater percentage in maxillary first molar, due to the non-localization of the second mesiobuccal canal in the mesiobuccal root. Several studies have developed in different populations, but the results cannot be extrapolated to other populations. Objective: The Objective of this research is to determine the incidence of the apical configuration, the interorificial average distance, and the possible relationship between the interorificial distance and the apical configuration, in the mesiobuccal root of first maxillary molar in Colombian population. Methods: Through a study "in vivo " A total of 113 CBCT images of superior molar zone were evaluated. The analysis consisted in measuring the interorificial distance at the floor level of the pulp chamber and determining the type of apical configuration of the MB root of maxillary first molar. This analysis was carried out using CS software for 3D images. A statistical analysis of the data was performed to determine the incidence of each apical configuration, the interorificial average distance, and in addition, the possible relationship between the interorificial distance and the apical configuration. Results: The percentage of incidence for apical configurations II and IV were 41.59 % and 58.40 %, respectively the interorificial average distance for apical configurations II and IV (Vertucci classification) were 2.44 mm and 2.52 mm, respectively. Conclusions: The interorificial average distance proved to be 2.49 mm. The most common anatomical configuration is IV for 58.40 % of the cases. There is no relationship between the interorificial distance and the apical configuration type. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to evaluate the prevalence of three-rooted permanent mandibular first molars (PMFMs) with four canals and their morphological characteristics among a Korean population from using cone-beam computed tomography scans (CBCTs). Materials and methods: Among the 705 CBCTs screened, 472 patient cases possessing at least one PMFM were identified. A total of 780 PMFMs were evaluated in axial section series to determine the number of roots and canals. The incidences of three-rooted PMFMs were compared with regard to gender and location. For distal root(s) with two canals, inter-orifice distances (IOD) between distobuccal and distolingual canals were measured at pulpal floor and furcation levels. The difference of IOD between males and females was also analyzed using chi-square tests. Results: Among the 472 CBCTs of 225 females and 247 males, 84 females and 107 males were found to have at least one three-rooted PMFM. Among the 780 PMFMs, 191 PMFMs (24.5%, 89 of 397 left and 102 of 383 right) were found to have three roots. The prevalence of distal root(s) with two canals was 34.2% (267 of 780). From the molars with two distal canals, the mean IOD between distobuccal and distolingual canals at the pulpal floor level was 3.1 mm in males and 2.9 mm in females ( p = 0.0428). Conclusions: The occurrence of three-rooted PMFMs among a Korean population was 24.5% and was higher than other countries and ethnicities. Understanding the prevalence of PMFMs with a distolingual root and/or canal in a Korean population and the IOD between distobuccal and distolingual canals may be useful for successful endodontic treatments. Clinical relevance: Acknowledgment of potential incidence of three-rooted permanent mandibular first molars with four canals and the distance between two distal canals may increase the success rate of root canal treatment by reducing the missing canal untreated. [ABSTRACT FROM AUTHOR]

This study aimed to characterize Neolithic human maxillary molars from archeological remains at the Jiaojia site, Shandong, China, and compare their ultrastructural features with sex and age-matched modern locals. Maxillary first (n = 86) and second (n = 80) molars in 5000-year-old individuals (n = 50) from the Jiaojia site were scanned by cone-beam computed tomography (CBCT). Sex and age-matched control groups were assigned from oral surgical patients at Shandong University. Images were analyzed for crown size, root length, root morphology, canal inter-orifice distances, mesiobuccal canal morphology, and second mesiobuccal (MB2) canal prevalence and location. Neolithic and modern values were compared statistically using Chi-squared and Mann-Whitney test at p <.05. Crown and root size were smaller, and canal inter-orifice distances were shorter in Neolithic maxillary molars than their modern counterparts. For mesiobuccal roots, Weine's Type I single canals were the most prevalent in Neolithic and modern first and second molars. MB2 canal prevalence were not significantly different (p >.05) in Neolithic (53.3%) or modern (60.5%) first molars, and Neolithic (11.3%) or modern (21.3%) second molars. But, MB2 prevalence was significantly higher for modern than ancient male first (p =.032) and second (p =.005) molars. Additionally, MB2 were located more mesially and closer to MB1 in Neolithic than modern molars. Maxillary molar root and canal morphology of ancient 5000-year-old remains at the Jiaojia site resemble that of local patients. A trend towards larger tooth size, and more dispersed MB2 canals over this short evolutionary period warrants additional investigation. • Crown and root size were smaller in Neolithic maxillary molars than modern clinical cases. • Second mesiobuccal canals were less prevalent in Neolithic maxillary molars than their counterparts, especially in males. • Canal orifice locations were less dispersed in Neolithic than modern maxillary molars. [ABSTRACT FROM AUTHOR]

Objectives: This study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT)., Materials and Methods: A total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at -1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t -test., Results: The prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and -3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar., Conclusions: The angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice., Competing Interests: Conflict of Interest: No potential conflict of interest relevant to this article was reported., (Copyright © 2020. The Korean Academy of Conservative Dentistry.)