Apical Anatomy of Maxillary First Premolars in an Iraqi Sub-Population: A Micro Computed Tomographic Study

Apical Anatomy of Maxillary First Premolars in an Iraqi Sub-Population: A Micro Computed Tomographic Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Apical Anatomy of Maxillary First Premolars in an Iraqi Sub-Population: A Micro Computed Tomographic Study Abdullah Mohammed Aljawhar, Norliza Ibrahim, Azwatee Abdul Aziz, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8744979/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives To investigate the apical root canal anatomy of maxillary first premolars in an Iraqi sub-population using micro-computed tomography (micro-CT). Materials and Methods A total of 151 extracted maxillary first premolars were collected and scanned using micro-CT. Images were segmented and three-dimensionally (3D) reconstructed using Mimics software. The apical constriction (AC) for each canal was located and distances were measured from the AC to the major apical foramen (MAF), to the anatomic apex (AA) and from MAF to AA. The longest and shortest canal diameters at AC were also measured. The cross-sectional canal shape at the AC and the direction of the MAFs were determined. Qualitative data were analysed using the Chi-Square test while quantitative data were analysed with the Independent-Samples T-test and One-Way ANOVA with Bonferroni post hoc tests and respective non-parametric tests at a significance level of 0.05. Results Out of the 151 included maxillary first premolars, 82 (54.3%) were double rooted and 69 (45.7%) were single-rooted. The mean AC-MAF, AC-AA and MAF-AA distances were 0.49 mm ± 0.32 mm, 1.13 mm ± 0.56 mm and 0.74 mm ± 0.49 mm, respectively. The AC to AA and MAF to AA distances were significantly larger in the palatal canals compared to both the buccal and single canals ( P < 0.05). The mean shortest and longest canal diameters at the AC were 0.18 mm ± 0.06 mm and 0.25 mm ± 0.1 mm, respectively, with 89.8% of the canals having oval cross-sectional shapes at AC. The two diameters were significantly smaller in the buccal canals compared to the palatal and single canals ( P < 0.05). In 74.2% of the canals, the MAFs were deviated to one of the root sides, mostly to the palatal and distal aspects. Conclusions The apical anatomy of maxillary first premolars is complex and variable in the studied Iraqi population. The majority of the canals had oval cross-sectional shapes at the AC with majority of MAFs showing deviation from the root axis. Health sciences/Anatomy Health sciences/Health care Health sciences/Medical research Apical anatomy Apical constriction Iraqi population Maxillary first premolar Micro-computed tomography Figures Figure 1 Figure 2 Figure 3 Introduction A crucial aspect in the success of the root canal shaping and cleaning procedures depends on understanding the anatomical characteristics of the apical part of the root canal system [ 1 ]. The complexity of the apical third anatomy has been demonstrated since the beginning of the last century [ 2 , 3 ]. However, Kuttler [ 4 ] deeply analysed and investigated the morphology of the apical region of the root. He described the apical anatomy as the root canal tapering from the canal orifices to the apical constriction which refers to the part of the root canal with the smallest diameter. Beyond the apical constriction, also referred to as minor apical foramen, the canal widens as it goes out through the major apical foramen which is the end opening of the root canal on the outer root surface. The distance between the apical constriction and the major foramen is generally about 0.5–1.5 mm, with the shape described as hyperbolic, morning glory flower or funnel-shaped [ 5 ]. The apical constriction has gained particular interest in anatomical studies because it is generally regarded as the reference point mostly used by dental practitioners as the apical limit for shaping, cleaning and obturation procedures [ 5 ]. By evaluating apical and peri-radicular tissues following root canal treatment Ricucci, Langeland [ 6 ] found that the most favourable prognosis noticed in the procedures terminated at the apical constriction while the worst prognosis was found when working beyond the apical constriction. However, they acknowledged that it is difficult to locate the apical constriction clinically. Normally, the major apical foramen is not located at the anatomical apex of the root, which is the morphological tip or the end of the root, but is about 0.5–3.0 mm offset [ 5 ]. This discrepancy is more noticeable in teeth of older individuals as a result of cementum apposition. Studies have revealed that the major apical foramen coincides with the anatomical apex 6.7–46% of the time [ 7 – 11 ]. Currently, micro-CT imaging modality is considered the gold standard for studying dental anatomy in ex vivo , providing a detailed quantitative and qualitative description of the teeth's external and internal anatomy [ 12 – 14 ], and overcoming the shortcomings of the other methods [ 15 ]. Even though the maxillary first premolars are thought to have one of the most complex apical anatomies [ 16 , 5 ], there is little evidence examining their apical foramina using micro-CT. Therefore, this study aimed to use micro-CT to investigate the apical root canal anatomy of maxillary first premolars in an Iraqi sub-population, determining the distance of apical constriction with regard to the major apical foramen and anatomical apex, measuring the canal diameters at the apical constriction and determining the directions of major apical foramina. Materials and methods - Ethical approval All methods were carried out in accordance with relevant guidelines and regulations. An informed consent was obtained from all subjects and/or their legal guardian(s), for both study participation and publication of identifying information images in an online open-access publication. The Scientific Committee of the College of Dentistry in University of Basrah as well as the Medical Ethics Committee of the Faculty of Dentistry in UNIVERSITI MALAYA had granted the approvals to conduct this study (approval no. 7/54/1706 and no. DF RD2207/0033 (L), respevtively). - Samples size calculation The sample size of this study was calculated using an online sample size calculator ( https://www.calculator.net/sample-size-calculator.html ). According to the Central Statistical Organization of Iraq [ 17 ], the Iraqi population is estimated to be around 35.5 million people, with the exception of the Kurds in the Kurdistan region in the north of Iraq. The sample size was estimated to be approximately 151 teeth using an 8% margin of error and a 95% level of confidence [ 18 ]. - Teeth collection and inclusion and exclusion criteria The required number of teeth was collected randomly from specialized dental centres and dental care clinics in the city of Basrah in the south of Iraq which is inhabited mainly by a population of Iraqi Arab ethnicity. The reasons for extraction were mainly for orthodontic treatments and were unrelated to this study. The patients’ ages and gender were unknown [ 18 ]. After extraction, the teeth were stored in 10% formalin solution and then washed with tap water, disinfected with 5.25% sodium hypochlorite for 30 minutes and cleaned with an ultrasonic scaler to remove calculus and periodontal tissue remnants then stored in distilled water at room temperature until the scanning date. Only fully developed maxillary first premolars with intact roots were included in the study. Teeth with open apices, root fracture, root resorption or previous root canal treatment were excluded from this study [ 18 ]. - Micro-CT scanning The collected teeth were scanned using a micro-CT system (ZEISS Xradia 520 Versa 3D X-ray microscope, Carl Zeiss, Germany, Department of Geology, Faculty of Science, Universiti Malaya) with a voxel size of 25.1 µm, at 80 kV, 88 µA, source-RA distance 56.1 mm, detector-RA distance 93.5 mm, with a degree of rotation of 360° and 0.4° step. Every three teeth were included together in one scan with their longitudinal axis fixed perpendicular to the frame using modelling wax [ 18 ]. The acquired 2D images were converted to DICOM format and utilized by the Mimics software (Mimics research 21, Materialise, Leuven, Belgium) for segmentation, 3D reconstruction and qualitative and quantitative evaluations [ 18 ]. - Investigating the Apical Anatomy The apical part of each canal, specifically 2 mm from the major apical foramen (MAF) was evaluated to determine the location of the Apical Constriction (AC) using the centerline algorithm in the Mimics software. Initially, and after centerline fitting, the canal’s cross-sectional areas were traced to determine the apical sections having the smallest sectional area. Subsequently, the circumference of these sections was checked to determine the sections with the smallest circumference, as illustrated in Fig. 1 a. This process ensured that the sections with the smallest cross-sectional area and the smallest circumference were selected to represent the AC. Then, the most coronal section of AC was used as a reference for measuring distances to the MAF and anatomic apex (AA). Using the distance measurement tool in the Mimics software, the following distances were measured for each canal: from AC to MAF, AC to AA and MAF to AA (Fig. 1 b). The root was then sectioned at the level of the coronal extent of AC perpendicular to the long axis of the canal (Fig. 1 c) and the shortest and longest canal diameters at the AC were measured using the ellipse measurement tool in the Mimics software (Fig. 1 d). The aspect ratio, defined as the ratio of the longest to the shortest canal diameters, was then calculated and used to classify the geometric cross-sectional shape of the root canals at the AC. The canals were categorized as: round-shaped when the aspect ratio is 1, oval-shaped canal when the aspect ratio is between 1 and 2, long oval canal when the aspect ratio is between 2 and 4, and flattened canal when the aspect ratio is higher than 4 [ 19 ]. Additionally, the direction of the MAF opening was determined for each canal and recorded as either centrally located or deviated to one of the root sides. - Statistical analysis The data was analysed using the SPSS software version 26 (IBM SPSS Statistics, Armonk, NY, USA). The Independent-Samples T-test was used to test the differences between the buccal and palatal canals in double-rooted teeth and between the buccal and palatal canals in single with those in the double-rooted teeth regarding the canal diameters and AC-MAF, AC-AA and MAF-AA distances, and the Mann-Whitney test was used for the non-normally distributed data. One-way ANOVA test with Bonferroni post hoc test was used to test the differences in the canal diameters and AC-MAF, AC-AA and MAF-AA distances within the buccal, palatal and single canals in single-rooted teeth, and the Independent-Samples Kruskal-Wallis test was used for the non-normally distributed data. The Chi-square test was used to test the differences in the cross-sectional shape of the canals at AC and the direction of apical foramen across the different canals in maxillary first premolars. The level of significance was set at 0.05 ( P = 0.05). Results A total of 151 maxillary first premolar teeth were examined in this study; 82 (54.3%) had two roots and 69 (45.7%) were single-rooted. The mean distances from AC to MAF, AC to AA and MAF to AA were 0.49 mm ± 0.32 mm, 1.13 mm ± 0.56 mm and 0.74 mm ± 0.49 mm, respectively (Table 1 ). Detailed results for these distances in the different canals of double and single-rooted teeth are presented in Tables 2 and 3 , respectively. Statistically, there were no significant differences between the buccal and palatal canals in the double-rooted teeth ( P > 0.05). However, in single-rooted teeth, the AC to MAF distance was significantly larger in the palatal canals compared to the single canals ( P 0.05). However, the AC to AA and MAF to AA distances were significantly larger in the palatal canals compared to both the buccal and single canals ( P < 0.05) (Table 3 ). Table 1 Descriptive statistics of apical foramens parameters of maxillary 1st premolars Apical anatomy parameters Minimum Maximum Median Mean Std. Deviation AC shortest diameter 0.03 0.42 0.17 0.18 0.06 AC longest diameter 0.05 0.70 0.23 0.25 0.10 Distance of AC - MAF 0.00 1.83 0.39 0.49 0.32 Distance of AC -AA 0.19 3.39 1.01 1.13 0.56 Distance of MAF -AA 0.07 3.08 0.64 0.74 0.49 Table 2 Comparing means of apical foramens parameters between buccal and palatal canals in double rooted maxillary 1st premolars Apical anatomy parameters canal N Median Mean Std. Deviation P. values AC shortest diameter B 78 0.16 0.17 0.06 0.002 a P 78 0.19 0.19 0.05 AC longest diameter B 78 0.22 0.23 0.10 0.026 b P 78 0.23 0.25 0.07 Distance of AC - MAF B 78 0.49 0.56 0.37 0.574 a P 78 0.53 0.59 0.32 Distance of AC -AA B 78 0.99 1.11 0.55 0.845 a P 78 1.02 1.09 0.45 Distance of MAF -AA B 78 0.56 0.65 0.40 0.409 a P 78 0.49 0.60 0.35 a Independent-Samples T-test b Mann-Whitney Test Table 3 Comparing means of apical foramens parameters between the different canals of single rooted maxillary 1st premolars Apical anatomy parameters Canal N Median Mean Std. Deviation P values AC shortest diameter B 46 0.14 0.15 0.06 B vs. P = .030 a B vs. S = .001 a P vs. S = .292 a P 46 0.18 0.18 0.06 S 17 0.20 0.21 0.07 Total 109 0.16 0.17 0.07 AC longest diameter B 46 0.21 0.22 0.08 B vs. P = .034 b B vs. S < 0.001 b P vs. S = .111 b P 46 0.27 0.27 0.11 S 17 0.33 0.36 0.15 Total 109 0.25 0.26 0.11 Distance of AC - MAF B 46 0.30 0.35 0.30 B vs. P = .075 a B vs. S = .887 a P vs. S = .023 a P 46 0.44 0.48 0.26 S 17 0.26 0.28 0.13 Total 109 0.33 0.39 0.27 Distance of AC -AA B 46 0.89 0.91 0.42 B vs. P = 0.001 b B vs. S = 1 b P vs. S = .004 b P 46 1.24 1.31 0.57 S 17 0.86 0.83 0.31 Total 109 0.98 1.06 0.52 Distance of MAF -AA B 46 0.59 0.63 0.31 B vs. P = .002 b B vs. S = 1 b P vs. S = .027 b P 46 0.86 0.95 0.50 S 17 0.53 0.61 0.33 Total 109 0.71 0.76 0.43 a Bonferroni Post Hoc Test b Independent-Samples Kruskal-Wallis Test The mean shortest and longest canal diameters at the apical constriction for all canals were 0.18 mm ± 0.06 mm and 0.25 mm ± 0.1 mm, respectively (Table 1 ). In the double-rooted teeth, both diameters were significantly greater in the palatal canals compared with the buccal canals (P < 0.05) (Table 2 ). In single-rooted teeth, the two diameters were significantly smaller in the buccal canals compared to the palatal and single canals (P 0.05) (Table 3 ). Regarding the cross-sectional shape of the root canals at the AC, the majority of the canals (89.8%) were oval-shaped at the AC and only 1.4% of the root canals had round cross-sectional shapes at AC. The Chi-square test showed no significant difference in the canals’ cross-sectional shape in the different root canal types of maxillary first premolars (P > 0.05). However, the single canals showed a higher prevalence of long-oval and flattened canals compared to buccal and palatal canals (Table 4 ). Table 4 Root canal cross-sectional shapes at the AC in the different canals of maxillary first premolars. Cross-sectional shape Total Flattened Long_Oval Oval Round canal B Count 1 10 113 1 125 % within canal 0.8% 8.0% 90.4% 0.8% 100.0% DB Count 0 1 7 1 9 % within canal 0.0% 11.1% 77.8% 11.1% 100.0% MB Count 0 2 7 0 9 % within canal 0.0% 22.2% 77.8% 0.0% 100.0% P Count 0 8 125 2 135 % within canal 0.0% 5.9% 92.6% 1.5% 100.0% S Count 1 3 13 0 17 % within canal 5.9% 17.6% 76.5% 0.0% 100.0% Total Count 2 24 265 4 295 % of Total 0.7% 8.1% 89.8% 1.4% 100.0% Regarding the direction of the MAF, the present data revealed that only 25.8% of the canals had centrally located foramina while in 74.2% of the cases, the foramina were deviated to one side of the root, most commonly toward the palatal and distal sides (Table 5 ). The Chi-square test revealed a significant difference in the direction of the apical foramen between the buccal and palatal canals in the double-rooted teeth (P < 0.05). The palatal canals were more likely to have centrally located foramina compared to the buccal canals. However, no significant difference was found in the direction of apical foramen between the canals in the single-rooted teeth (P > 0.05). Table 5 Directions of apical foramina in the different canals of maxillary first premolars. Canal Direction of MAF Central Deviated Total B P D DB DP M MB MP B 26 19.5% 14 10.5% 21 15.8% 43 32.3% 1 0.8% 2 1.5% 20 15.0% 3 2.3% 3 2.3% 133 100% DB 0 0 1 20% 4 80% 0 0 0 0 0 5 100% MB 2 40% 0 1 20% 0 0 0 2 40% 0 0 5 100% P 42 31.1% 4 3% 46 34.1% 14 10.4% 1 0.7% 4 3% 18 13.3% 1 0.7% 5 3.7% 135 100% S 6 35.3% 1 5.9% 3 17.6% 2 11.8% 0 4 23.5% 1 5.9% 0 0 17 100% Total 76 25.8% 19 6.4% 72 24.4% 63 21.4% 2 0.7% 10 3.4% 41 13.9% 4 1.4% 8 2.7% 295 100% 219 (74.2%) Discussion Apical constriction is frequently regarded to be the optimal endpoint for root canal treatment procedures, given that there is a natural narrowing of the root canal almost at its terminus. This is supposedly where an apical stop can be established and the root canal filling materials get packed [ 20 , 21 , 5 ]. According to the American Association Glossary of Endodontic Terms (2020), the AC has been defined as the apical portion of the root canal having the narrowest diameter; its position may vary but is usually 0.5–1.0 mm short of the centre of the major apical foramen [ 22 ]. However, it does not clarify whether the narrowest diameter should be measured from the long or short axis of the canal to determine the AC since the root canal cross-sectional shape is not round most of the time to have only one diameter and it has been reported that the root canal cross-sectional shape in the apical thirds of maxillary first premolars is mainly oval and long oval [ 23 ]. This definition may be based on the traditional studies of apical anatomy that identified the AC by evaluating the longitudinal root canal sections that reveal only one canal diameter, which can be the buccolingual or the mesiodistal diameter. It has been shown that the longitudinal sections yield different forms and locations of the constriction in the same canal and therefore provide inconsistent results compared to cross-sectional analysis [ 24 ]. This suggests that a more reliable method for determining the AC involves cross-sectional analysis that accounts for both long and short canal diameters, as well as the overall sectional area and circumference. This approach provides a more accurate and comprehensive understanding of the canal morphology at the AC, which is critical for effective cleaning, shaping, and obturation in root canal therapy. ElAyouti et al. [ 25 ] and Chang et al. [ 26 ] located the AC by comparing cross-sectional areas along the path of the canal and considering the apical cross sections having the smallest area as the narrowest part of the canal or the constriction. However, their methods diverged in terms of measurement of reference point: ElAyouti et al (2014) used the most apical section of the constriction as a reference for distance measurements, while Chang et al (2022) used the coronal extent of the AC to measure the distance to the MAF. On the other hand, Piasecki et al. [ 27 ] used a different approach by measuring the canal’s perimeter or circumference to detect the AC using the most coronal slice as a reference for its location. Given these varying methodologies and to improve accuracy, the authors considered both the sectional area and circumference to determine the AC. The coronal section of AC was used as a reference for measuring distances to the MAF and to the AA so as not to violate the narrowest part of the canal since the rationale for using AC as the endpoint for intra-canal procedures is to preserve the narrowest zone of the canal which facilitate creating an apical stop to avoid overfilling and minimizing irritation and wound area of the periapical tissues. This study revealed that the AC is located at variable distances from the MAF (Fig. 2 ), with a mean distance measured at 0.49 mm, which is found to be in agreement with the results reported by Dummer et al. [ 20 ] in maxillary premolars which was 0.53 mm, and with the results reported by Kuttler [ 4 ] in the young age group which was about 0.52 mm without specifying the teeth type. However, the AC-MAF distance recorded in this study was greater than that reported by ElAyouti et al. [ 25 ] in which the measured AC-MAF distance was reported to be 0.2 mm in their micro-CT study. This discrepancy may be attributed to the different types of teeth used (maxillary first premolars vs. maxillary and mandibular molars), as well as to the different reference points used for measuring distances since ElAyouti et al. [ 25 ] used the apical extent of AC while the coronal AC extent was used in this study. The mean distance from the AC to AA measured in this study was 1.13 mm. These results were consistent with those reported by Shimizu et al. [ 28 ] in a study of maxillary first premolars from Japanese patients. A slightly shorter AC-AA distance of maxillary premolars was reported by Dummer et al. [ 20 ] with an average of 0.95 mm. Nevertheless, a consensus can be observed in the findings of different anatomic studies regarding the mean AC-AA distance to be fluctuating around 1 mm [ 25 , 29 , 30 , 13 ], which is in accordance with the results recorded in this study. The mean distance of MAF to AA measured in this study was 0.74 mm, and this is in agreement with the findings of several studies [ 31 , 16 , 25 ]. For instance, Martos et al. [ 31 ] reported that the mean MAF-AA distance in maxillary premolars was 0.67 mm, however, they measured the distance from the AA to the most apical point of the MAF not to the centre of MAF as was the case in this study. Morfis et al. [ 16 ] reported that the mean distance from AA to the centre of MAF was about 0.82 mm in maxillary premolars. A mean MAF-AA distance of 0.7 mm has been reported by ElAyouti et al. [ 25 ] in a study of ninety human maxillary and mandibular molars. However, a shorter MAF to AA distance of about 0.48 mm in young patients and about 0.6 mm in older patients had been reported by Kuttler [ 4 ] and a mean MAF-AA distance of about 0.42 mm had been reported by Dummer et al. [ 20 ]. These minor differences can be partially attributed to the various approaches employed in measuring the distances as well as the likely usage of varying reference points [ 7 ]. Additionally, it has been reported that racial differences between populations may contribute to these discrepancies [ 32 ]. Knowing the probable diameters of the apical constriction or the minor apical foramen can help practitioners in getting a proper apical preparation which should be performed while avoiding excessive enlargement to the constriction [ 33 , 34 ]. The results of this study revealed that the mean shortest or minimum diameter of the constriction was 0.18 mm and the mean longest or maximum diameter was 0.25 mm. These findings were lower than those reported by Shimizu et al. [ 28 ] and by Abarca et al. [ 1 ], while in agreement with the findings of other studies [ 35 , 36 , 30 ]. The most common canal cross-sectional shape at the AC was oval (89.8%), and this is in agreement with several studies [ 35 , 1 , 36 ]. This information can help in the decision-making process regarding the initial and final apical file size [ 37 ]. Before root canal enlargement, the initial apical file size can be estimated based on the AC minimum diameter. Since the majority of canals have an oval cross-section, the final file size should be large enough to touch every canal wall during the preparation procedures. Put another way, the master apical file size should match the longest diameter of AC to shape the canal round [ 35 ]. The results of this study revealed that the difference between the longest and shortest canal diameters was equal to or less than 0.15 mm in about 90% of the canals and was equal to or less than 0.20 mm in about 95% of the examined canals. According to these data, preparing the canals to 3 and 4 instrument sizes larger than the initial apical file size will turn the apical constriction into a round shape in 90% and 95% of the cases, respectively. When the MAF is not located at the anatomical root apex tip, it is referred to as a foramen deviation, which can be resulted from both pathological and physiological conditions [ 29 ]. The frequency of deviated MAF in this study was 74.2%; mostly to the palatal and distal sides. These results were in close agreement with those reported by Blasković-Subat et al. [ 29 ] and Sert, Bayirli [ 38 ]. Higher frequencies of deviated MAF had been reported by Vertucci, Gegauff [ 39 ] (88%) and by Burch, Hulen [ 7 ] (92.4%). However, lower frequencies of about 40% and 15% also had been reported by Awawdeh et al. [ 40 ] and Senan et al. [ 41 ], respectively. These discrepancies between the various studies could be the consequence of using various definitions and methodologies, as well as the different population groups that each study examined [ 40 , 29 ]. The discrepancies in different reported data about the position of apical foramina may also be attributed to patient age and sample size [ 40 ]. Kuttler [ 4 ] reported that the percentage of deviated foramina in older age patients (55 years and older) was 80%, whereas the percentage in younger age patients (18–25 years) was 68%. According to Stein, Corcoran [ 42 ], there is a positive correlation between age and the deviation and diameter of the foramen opening as a result of apical cementum thickening. The results of our study, as well as those of previous studies, have revealed that the frequency of deviated MAF opening is high. This is not usually detectable on radiographic examination, especially when this deviation occurs toward the buccal or palatal root surface (Fig. 3 ). For this reason and in order to prevent periodontal ligament damage, clinicians should consider this when performing root canal therapy. Root canal working length is better determined by the use of the electronic foramen locaters in combination with tactile and radiographic evaluation. This study is among the few that have utilized the innovative micro-CT technology to investigate the apical anatomy of maxillary first premolars and the first to be held in the Iraqi population, although, this kind of teeth was reported to possess one of the most complex and variable root canal apical anatomy [ 16 , 5 ]. However, the cost and technical limitations of the micro-CT technology were the main challenge for the sample size of the study. Furthermore, the patients’ ages and the apical pathologic conditions of the collected teeth were unknown, and these may affect the location and size of the apical foramina. Therefore, conducting future studies taking into account the age and the pathologic history of the collected teeth would be valuable in providing a more comprehensive understanding of the apical anatomy. Conclusion This study revealed that the apical anatomy of maxillary first premolars is variable in the studied Iraqi population and the AC is located at variable distances from the MAF with an average distance of about 0.5 mm. The MAFs deviated in 74.2% of examined root canals mostly to the palatal and distal side. The cross-sectional shape of the root canal is predominantly oval. Furthermore, shaping the canals to 4 sizes larger than the initial apical file size will turn the AC round in 95% of the examined canals. Declarations Funding This study was financially supported by UNIVERSITI MALAYA DPRG grant no. UMG002E-2022. Acknowledgements The authors would like to acknowledge Dr. Hijaz Kamal Hasnan, Department of Geology, Faculty of Science, University of Malaya, Malaysia for his efforts in sample scanning. Authors' contributions A.M.A.: design, data analysis & interpretation, writing and revision. N.H.A.: design, data analysis & interpretation writing and revision. H.M.A.A.: design, data analysis & interpretation writing and revision. N.I.: design, data analysis & interpretation and revision. A.A.A.: design, data analysis & interpretation and revision. Competing interests The authors declare no competing interests. Data availability The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request. References Abarca, J. et al. Morphology of the Physiological Apical Foramen of Maxillary Premolars. Int. J. Morphology ; 36 (1). (2018). Hess, W. 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A., Basrani, B. & Sousa-Neto, M. D.) The Root Canal Anatomy in Permanent Dentition. Cham: Springer International Publishing; 31–46. (2019). Dummer, P. M., Mcginn, J. H. & Rees, D. G. The position and topography of the apical canal constriction and apical foramen. Int. Endod. J. 17 (4), 192–198 (1984). Wu, M-K., Wesselink, P. R. & Walton, R. E. Apical terminus location of root canal treatment procedures. Oral Surgery, Oral Medicine, Oral Pathology. Oral Radiol. Endodontology . 89 (1), 99–103 (2000). AAE. Glossary of Endodontic Terms. Tenth Edition ed. Chicago, IL 60601 (American Association of Endodontists, 2020). Liu, X., Gao, M., Ruan, J. & Lu, Q. Root canal anatomy of maxillary first premolar by microscopic computed tomography in a Chinese adolescent subpopulation. BioMed Research International. ;2019. (2019). Schell, S. et al. Validity of longitudinal sections for determining the apical constriction. Int. Endod. J. 50 (7), 706–712 (2017). ElAyouti, A. et al. Apical constriction: location and dimensions in molars—a micro–computed tomography study. J. Endod. 40 (8), 1095–1099 (2014). Chang, J. W. W. et al. Morphotypes of the apical constriction of maxillary molars: a micro-computed tomographic evaluation. Restor. Dentistry Endodontics ; 47 (2). (2022). Piasecki, L. et al. The use of micro–computed tomography to determine the accuracy of 2 electronic apex locators and anatomic variations affecting their precision. J. Endod. 42 (8), 1263–1267 (2016). Shimizu, Y., Hara, T. & Ide, Y. A Morphological Study of the Apical Third of the Root Canal in the Maxillary First Premolar using Micro-CT. J. Oral Biosci. 46 (1), 1–10. https://doi.org/10.1016/S1349-0079(04)80007-0 (2004). Blasković-Subat, V., Maricić, B. & Sutalo, J. Asymmetry of the root canal foramen. Int. Endod J. 25 (3), 158–164. 10.1111/j.1365-2591.1992.tb00779.x (1992). Marroquín, B. B., El-Sayed, M. A. & Willershausen-Zönnchen, B. Morphology of the physiological foramen: I. Maxillary and mandibular molars. J. Endod . 30 (5), 321–328. 10.1097/00004770-200405000-00005 (2004). Martos, J., Ferrer-Luque, C., González‐Rodríguez, M. & Castro, L. Topographical evaluation of the major apical foramen in permanent human teeth. Int. Endod. J. 42 (4), 329–334 (2009). Saeed, M. S. Apical foramen position in relation to proximal root surfaces of the premolar teeth in Kurdistan region of Iraq: A retrospective CBCT assessment. Turkish Endodontic J. (TEJ) . 8 (3), 116–122 (2023). Schilder, H. Cleaning and shaping the root canal. Dental Clin. N. Am. 18 (2), 269–296 (1974). Buchanan, L. The standardized-taper root canal preparation–Part 1. Concepts for variably tapered shaping instruments. Int. Endod. J. 33 (6), 516–529 (2000). Arora, S. & Tewari, S. The morphology of the apical foramen in posterior teeth in a North Indian population. Int. Endod. J. 42 (10), 930–939 (2009). Ayranci, L. B., Yeter, K. Y., Arslan, H. & Kseoğlu, M. Morphology of apical foramen in permanent molars and premolars in a Turkish population. Acta Odontol. Scand. 71 (5), 1043–1049 (2013). Vanni, J. R. et al. Influence of cervical preflaring on determination of apical file size in maxillary molars: SEM analysis. Braz. Dent. J. 16 , 181–186 (2005). Sert, S. & Bayirli, G. S. Evaluation of the root canal configurations of the mandibular and maxillary permanent teeth by gender in the Turkish population. J. Endod . 30 (6), 391–398. 10.1097/00004770-200406000-00004 (2004). Vertucci, F. J. & Gegauff, A. Root canal morphology of the maxillary first premolar. Journal of the American Dental Association 1979;99(2):194-8. (1939). Awawdeh, L., Abdullah, H. & Al-Qudah, A. Root form and canal morphology of Jordanian maxillary first premolars. J. Endod. 34 (8), 956–961 (2008). Senan, E. M., Alhadainy, H. A., Genaid, T. M. & Madfa, A. A. Root form and canal morphology of maxillary first premolars of a Yemeni population. BMC Oral Health . 18 (1), 1–10 (2018). Stein, T. J. & Corcoran, J. F. Anatomy of the root apex and its histologic changes with age. Oral Surg. Oral Med. Oral Pathol. 69 (2), 238–242. 10.1016/0030-4220(90)90334-o (1990). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8744979","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":593598006,"identity":"e630fc32-ce37-4300-95fb-cc8e8c90e145","order_by":0,"name":"Abdullah Mohammed Aljawhar","email":"","orcid":"","institution":"University of Basrah","correspondingAuthor":false,"prefix":"","firstName":"Abdullah","middleName":"Mohammed","lastName":"Aljawhar","suffix":""},{"id":593598007,"identity":"97bdd46b-7302-4980-aa54-72358259795f","order_by":1,"name":"Norliza Ibrahim","email":"","orcid":"","institution":"Universiti Malaya","correspondingAuthor":false,"prefix":"","firstName":"Norliza","middleName":"","lastName":"Ibrahim","suffix":""},{"id":593598009,"identity":"7818137c-3987-4ce4-89d7-7425da0d6119","order_by":2,"name":"Azwatee Abdul Aziz","email":"","orcid":"","institution":"Universiti Malaya","correspondingAuthor":false,"prefix":"","firstName":"Azwatee","middleName":"Abdul","lastName":"Aziz","suffix":""},{"id":593598011,"identity":"f416d5cc-d560-493e-89a8-72e21b297c56","order_by":3,"name":"Hany Mohamed Aly Ahmed","email":"","orcid":"","institution":"Universiti Malaya","correspondingAuthor":false,"prefix":"","firstName":"Hany","middleName":"Mohamed Aly","lastName":"Ahmed","suffix":""},{"id":593598014,"identity":"22b3bc26-a019-4cf5-9b61-9ca2f95e1de6","order_by":4,"name":"Noor Hayati Azami","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5UlEQVRIiWNgGAWjYDACCSTywAcwlUCMlgSIloMzSNACYTPzEKPFXLr5mcTPHxby8u2nEw/btm1j4GfPMWC62YZbi+WcY2aSPQkSho09uRsO57bdZpDseWPAnItHi8GNBDMJngQJxmYGqBaDGzmEtKR/k/yTIGHfxv92w2FLoBZ7wlpyzKSBtiT2SABtYQTZIkFYS7G1TJpE8gyJtxsO9py7zSNx5lnB4ZxzeB228eYbmzrb+f25mz/8KLstx9+evPFxThluLUDAIoHMA0fNAUY2vFqYP2AR/INXyygYBaNgFIwsAACdM1SKZ7Ui6gAAAABJRU5ErkJggg==","orcid":"","institution":"Universiti Malaya","correspondingAuthor":true,"prefix":"","firstName":"Noor","middleName":"Hayati","lastName":"Azami","suffix":""}],"badges":[],"createdAt":"2026-01-30 21:38:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8744979/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8744979/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103175987,"identity":"618485ec-7e46-4594-bee9-ac487bcd9a85","added_by":"auto","created_at":"2026-02-22 16:29:17","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1007510,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) \u003c/strong\u003eDetermining the location of apical constriction, (\u003cstrong\u003eb)\u003c/strong\u003e Measuring the distances between AC-MAF, AC-AA and MAF-AA, (\u003cstrong\u003ec)\u003c/strong\u003e Root cutting at the level of the coronal extent of AC perpendicular to the long axis of the canal, (\u003cstrong\u003ed)\u003c/strong\u003eMeasuring the longest and shortest canal diameters at AC.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8744979/v1/e360968fad681a65ae859ebd.png"},{"id":103505194,"identity":"f7717e76-9e05-4aa9-81ab-91e27f9fd091","added_by":"auto","created_at":"2026-02-26 13:27:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":536978,"visible":true,"origin":"","legend":"\u003cp\u003eVarious locations of AC in the different root canals of maxillary first premolars.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8744979/v1/2f7583bdfbad219be9a01d01.png"},{"id":103175985,"identity":"7e1f0135-f05b-4ba7-a4c5-0eb45d3de5d2","added_by":"auto","created_at":"2026-02-22 16:29:17","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":171632,"visible":true,"origin":"","legend":"\u003cp\u003eDifferent directions of the MAF as viewed from the buccal side of the roots\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8744979/v1/5b90f75dfbac167417b750b5.png"},{"id":109437242,"identity":"3c3f390d-f49a-406e-9cb1-8606ea5399fc","added_by":"auto","created_at":"2026-05-18 06:25:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2153519,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8744979/v1/dc638221-dff9-44b2-8073-e93908851b27.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Apical Anatomy of Maxillary First Premolars in an Iraqi Sub-Population: A Micro Computed Tomographic Study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eA crucial aspect in the success of the root canal shaping and cleaning procedures depends on understanding the anatomical characteristics of the apical part of the root canal system [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The complexity of the apical third anatomy has been demonstrated since the beginning of the last century [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. However, Kuttler [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] deeply analysed and investigated the morphology of the apical region of the root. He described the apical anatomy as the root canal tapering from the canal orifices to the apical constriction which refers to the part of the root canal with the smallest diameter. Beyond the apical constriction, also referred to as minor apical foramen, the canal widens as it goes out through the major apical foramen which is the end opening of the root canal on the outer root surface. The distance between the apical constriction and the major foramen is generally about 0.5\u0026ndash;1.5 mm, with the shape described as hyperbolic, morning glory flower or funnel-shaped [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe apical constriction has gained particular interest in anatomical studies because it is generally regarded as the reference point mostly used by dental practitioners as the apical limit for shaping, cleaning and obturation procedures [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. By evaluating apical and peri-radicular tissues following root canal treatment Ricucci, Langeland [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] found that the most favourable prognosis noticed in the procedures terminated at the apical constriction while the worst prognosis was found when working beyond the apical constriction. However, they acknowledged that it is difficult to locate the apical constriction clinically.\u003c/p\u003e \u003cp\u003eNormally, the major apical foramen is not located at the anatomical apex of the root, which is the morphological tip or the end of the root, but is about 0.5\u0026ndash;3.0 mm offset [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This discrepancy is more noticeable in teeth of older individuals as a result of cementum apposition. Studies have revealed that the major apical foramen coincides with the anatomical apex 6.7\u0026ndash;46% of the time [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCurrently, micro-CT imaging modality is considered the gold standard for studying dental anatomy in \u003cem\u003eex vivo\u003c/em\u003e, providing a detailed quantitative and qualitative description of the teeth's external and internal anatomy [\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and overcoming the shortcomings of the other methods [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Even though the maxillary first premolars are thought to have one of the most complex apical anatomies [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], there is little evidence examining their apical foramina using micro-CT. Therefore, this study aimed to use micro-CT to investigate the apical root canal anatomy of maxillary first premolars in an Iraqi sub-population, determining the distance of apical constriction with regard to the major apical foramen and anatomical apex, measuring the canal diameters at the apical constriction and determining the directions of major apical foramina.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e- Ethical approval\u003c/h2\u003e \u003cp\u003e All methods were carried out in accordance with relevant guidelines and regulations. An informed consent was obtained from all subjects and/or their legal guardian(s), for both study participation and publication of identifying information images in an online open-access publication. The Scientific Committee of the College of Dentistry in University of Basrah as well as the Medical Ethics Committee of the Faculty of Dentistry in UNIVERSITI MALAYA had granted the approvals to conduct this study (approval no. 7/54/1706 and no. DF RD2207/0033 (L), respevtively).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e- Samples size calculation\u003c/h3\u003e\n\u003cp\u003eThe sample size of this study was calculated using an online sample size calculator (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.calculator.net/sample-size-calculator.html\u003c/span\u003e\u003cspan address=\"https://www.calculator.net/sample-size-calculator.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). According to the Central Statistical Organization of Iraq [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], the Iraqi population is estimated to be around 35.5\u0026nbsp;million people, with the exception of the Kurds in the Kurdistan region in the north of Iraq. The sample size was estimated to be approximately 151 teeth using an 8% margin of error and a 95% level of confidence [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003e- Teeth collection and inclusion and exclusion criteria\u003c/h3\u003e\n\u003cp\u003eThe required number of teeth was collected randomly from specialized dental centres and dental care clinics in the city of Basrah in the south of Iraq which is inhabited mainly by a population of Iraqi Arab ethnicity. The reasons for extraction were mainly for orthodontic treatments and were unrelated to this study. The patients\u0026rsquo; ages and gender were unknown [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. After extraction, the teeth were stored in 10% formalin solution and then washed with tap water, disinfected with 5.25% sodium hypochlorite for 30 minutes and cleaned with an ultrasonic scaler to remove calculus and periodontal tissue remnants then stored in distilled water at room temperature until the scanning date. Only fully developed maxillary first premolars with intact roots were included in the study. Teeth with open apices, root fracture, root resorption or previous root canal treatment were excluded from this study [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003e- Micro-CT scanning\u003c/h3\u003e\n\u003cp\u003eThe collected teeth were scanned using a micro-CT system (ZEISS Xradia 520 Versa 3D X-ray microscope, Carl Zeiss, Germany, Department of Geology, Faculty of Science, Universiti Malaya) with a voxel size of 25.1 \u0026micro;m, at 80 kV, 88 \u0026micro;A, source-RA distance 56.1 mm, detector-RA distance 93.5 mm, with a degree of rotation of 360\u0026deg; and 0.4\u0026deg; step. Every three teeth were included together in one scan with their longitudinal axis fixed perpendicular to the frame using modelling wax [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The acquired 2D images were converted to DICOM format and utilized by the Mimics software (Mimics research 21, Materialise, Leuven, Belgium) for segmentation, 3D reconstruction and qualitative and quantitative evaluations [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003e- Investigating the Apical Anatomy\u003c/h3\u003e\n\u003cp\u003eThe apical part of each canal, specifically 2 mm from the major apical foramen (MAF) was evaluated to determine the location of the Apical Constriction (AC) using the centerline algorithm in the Mimics software. Initially, and after centerline fitting, the canal\u0026rsquo;s cross-sectional areas were traced to determine the apical sections having the smallest sectional area. Subsequently, the circumference of these sections was checked to determine the sections with the smallest circumference, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea. This process ensured that the sections with the smallest cross-sectional area and the smallest circumference were selected to represent the AC. Then, the most coronal section of AC was used as a reference for measuring distances to the MAF and anatomic apex (AA). Using the distance measurement tool in the Mimics software, the following distances were measured for each canal: from AC to MAF, AC to AA and MAF to AA (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The root was then sectioned at the level of the coronal extent of AC perpendicular to the long axis of the canal (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec) and the shortest and longest canal diameters at the AC were measured using the ellipse measurement tool in the Mimics software (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). The aspect ratio, defined as the ratio of the longest to the shortest canal diameters, was then calculated and used to classify the geometric cross-sectional shape of the root canals at the AC. The canals were categorized as: round-shaped when the aspect ratio is 1, oval-shaped canal when the aspect ratio is between 1 and 2, long oval canal when the aspect ratio is between 2 and 4, and flattened canal when the aspect ratio is higher than 4 [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Additionally, the direction of the MAF opening was determined for each canal and recorded as either centrally located or deviated to one of the root sides.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e- Statistical analysis\u003c/h2\u003e \u003cp\u003eThe data was analysed using the SPSS software version 26 (IBM SPSS Statistics, Armonk, NY, USA). The Independent-Samples T-test was used to test the differences between the buccal and palatal canals in double-rooted teeth and between the buccal and palatal canals in single with those in the double-rooted teeth regarding the canal diameters and AC-MAF, AC-AA and MAF-AA distances, and the Mann-Whitney test was used for the non-normally distributed data. One-way ANOVA test with Bonferroni post hoc test was used to test the differences in the canal diameters and AC-MAF, AC-AA and MAF-AA distances within the buccal, palatal and single canals in single-rooted teeth, and the Independent-Samples Kruskal-Wallis test was used for the non-normally distributed data. The Chi-square test was used to test the differences in the cross-sectional shape of the canals at AC and the direction of apical foramen across the different canals in maxillary first premolars. The level of significance was set at 0.05 (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.05).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 151 maxillary first premolar teeth were examined in this study; 82 (54.3%) had two roots and 69 (45.7%) were single-rooted. The mean distances from AC to MAF, AC to AA and MAF to AA were 0.49 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 mm, 1.13 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.56 mm and 0.74 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49 mm, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Detailed results for these distances in the different canals of double and single-rooted teeth are presented in Tables\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, respectively. Statistically, there were no significant differences between the buccal and palatal canals in the double-rooted teeth (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, in single-rooted teeth, the AC to MAF distance was significantly larger in the palatal canals compared to the single canals (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), but not significant when compared to the buccal canals (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, the AC to AA and MAF to AA distances were significantly larger in the palatal canals compared to both the buccal and single canals (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDescriptive statistics of apical foramens parameters of maxillary 1st premolars\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApical anatomy parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMinimum\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMaximum\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStd. Deviation\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAC shortest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAC longest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC - MAF\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDistance of MAF -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparing means of apical foramens parameters between buccal and palatal canals in double rooted maxillary 1st premolars\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApical anatomy parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ecanal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStd. Deviation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003eP.\u003c/em\u003e values\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eAC shortest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.002\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eAC longest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.026\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC - MAF\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.574\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.845\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.45\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eDistance of MAF -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.65\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.409\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003ea\u003c/sup\u003eIndependent-Samples T-test\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003eb\u003c/sup\u003eMann-Whitney Test\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparing means of apical foramens parameters between the different canals of single rooted maxillary 1st premolars\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eApical anatomy parameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCanal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStd. Deviation\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e values\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eAC shortest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eB vs. P = .030\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eB vs. S = .001\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eP vs. S = .292\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eAC longest diameter\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eB vs. P = .034\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eB vs. S\u0026thinsp;\u0026lt;\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eP vs. S = .111\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC - MAF\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eB vs. P = .075\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eB vs. S = .887\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eP vs. S = .023\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.27\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eDistance of AC -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eB vs. P\u0026thinsp;=\u0026thinsp;0.001\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eB vs. S\u0026thinsp;=\u0026thinsp;1\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eP vs. S = .004\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eDistance of MAF -AA\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.59\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eB vs. P = .002\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eB vs. S\u0026thinsp;=\u0026thinsp;1\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eP vs. S = .027\u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.43\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003ea\u003c/sup\u003eBonferroni Post Hoc Test\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003e\u003csup\u003eb\u003c/sup\u003eIndependent-Samples Kruskal-Wallis Test\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe mean shortest and longest canal diameters at the apical constriction for all canals were 0.18 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 mm and 0.25 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 mm, respectively (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). In the double-rooted teeth, both diameters were significantly greater in the palatal canals compared with the buccal canals (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). In single-rooted teeth, the two diameters were significantly smaller in the buccal canals compared to the palatal and single canals (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05), however, there was no significant difference in AC diameters between the palatal and single canals (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eRegarding the cross-sectional shape of the root canals at the AC, the majority of the canals (89.8%) were oval-shaped at the AC and only 1.4% of the root canals had round cross-sectional shapes at AC. The Chi-square test showed no significant difference in the canals\u0026rsquo; cross-sectional shape in the different root canal types of maxillary first premolars (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05). However, the single canals showed a higher prevalence of long-oval and flattened canals compared to buccal and palatal canals (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eRoot canal cross-sectional shapes at the AC in the different canals of maxillary first premolars.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c7\" namest=\"c4\"\u003e \u003cp\u003eCross-sectional shape\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFlattened\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLong_Oval\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eOval\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eRound\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"9\" rowspan=\"10\"\u003e \u003cp\u003e\u003cb\u003ecanal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e113\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e125\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% within canal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e90.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eDB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% within canal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e77.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e11.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% within canal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e22.2%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e77.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e125\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e135\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% within canal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e92.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% within canal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e17.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e76.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c2\" namest=\"c1\" rowspan=\"2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCount\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e265\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e295\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e% of Total\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e89.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eRegarding the direction of the MAF, the present data revealed that only 25.8% of the canals had centrally located foramina while in 74.2% of the cases, the foramina were deviated to one side of the root, most commonly toward the palatal and distal sides (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The Chi-square test revealed a significant difference in the direction of the apical foramen between the buccal and palatal canals in the double-rooted teeth (P\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The palatal canals were more likely to have centrally located foramina compared to the buccal canals. However, no significant difference was found in the direction of apical foramen between the canals in the single-rooted teeth (P\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDirections of apical foramina in the different canals of maxillary first premolars.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"11\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eCanal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"10\" nameend=\"c11\" namest=\"c2\"\u003e \u003cp\u003eDirection of MAF\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCentral\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c10\" namest=\"c3\"\u003e \u003cp\u003eDeviated\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eDB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eDP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMB\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eMP\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26\u003c/p\u003e \u003cp\u003e19.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14\u003c/p\u003e \u003cp\u003e10.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21\u003c/p\u003e \u003cp\u003e15.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e43\u003c/p\u003e \u003cp\u003e32.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e0.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e1.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e20\u003c/p\u003e \u003cp\u003e15.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e3\u003c/p\u003e \u003cp\u003e2.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e3\u003c/p\u003e \u003cp\u003e2.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e133\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eDB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e20%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e80%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMB\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e40%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e20%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e40%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eP\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e42\u003c/p\u003e \u003cp\u003e31.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e46\u003c/p\u003e \u003cp\u003e34.1%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14\u003c/p\u003e \u003cp\u003e10.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e0.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e18\u003c/p\u003e \u003cp\u003e13.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e0.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e3.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e135\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003cp\u003e35.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e5.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003cp\u003e17.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e11.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e23.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e5.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e17\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e\u003cb\u003eTotal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e76\u003c/p\u003e \u003cp\u003e25.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19\u003c/p\u003e \u003cp\u003e6.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e72\u003c/p\u003e \u003cp\u003e24.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e63\u003c/p\u003e \u003cp\u003e21.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e0.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e10\u003c/p\u003e \u003cp\u003e3.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e41\u003c/p\u003e \u003cp\u003e13.9%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e1.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e8\u003c/p\u003e \u003cp\u003e2.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e295\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"8\" nameend=\"c10\" namest=\"c3\"\u003e \u003cp\u003e219 (74.2%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eApical constriction is frequently regarded to be the optimal endpoint for root canal treatment procedures, given that there is a natural narrowing of the root canal almost at its terminus. This is supposedly where an apical stop can be established and the root canal filling materials get packed [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the American Association Glossary of Endodontic Terms (2020), the AC has been defined as the apical portion of the root canal having the narrowest diameter; its position may vary but is usually 0.5\u0026ndash;1.0 mm short of the centre of the major apical foramen [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, it does not clarify whether the narrowest diameter should be measured from the long or short axis of the canal to determine the AC since the root canal cross-sectional shape is not round most of the time to have only one diameter and it has been reported that the root canal cross-sectional shape in the apical thirds of maxillary first premolars is mainly oval and long oval [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. This definition may be based on the traditional studies of apical anatomy that identified the AC by evaluating the longitudinal root canal sections that reveal only one canal diameter, which can be the buccolingual or the mesiodistal diameter. It has been shown that the longitudinal sections yield different forms and locations of the constriction in the same canal and therefore provide inconsistent results compared to cross-sectional analysis [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This suggests that a more reliable method for determining the AC involves cross-sectional analysis that accounts for both long and short canal diameters, as well as the overall sectional area and circumference. This approach provides a more accurate and comprehensive understanding of the canal morphology at the AC, which is critical for effective cleaning, shaping, and obturation in root canal therapy.\u003c/p\u003e \u003cp\u003eElAyouti et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] and Chang et al. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] located the AC by comparing cross-sectional areas along the path of the canal and considering the apical cross sections having the smallest area as the narrowest part of the canal or the constriction. However, their methods diverged in terms of measurement of reference point: ElAyouti et al (2014) used the most apical section of the constriction as a reference for distance measurements, while Chang et al (2022) used the coronal extent of the AC to measure the distance to the MAF. On the other hand, Piasecki et al. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] used a different approach by measuring the canal\u0026rsquo;s perimeter or circumference to detect the AC using the most coronal slice as a reference for its location. Given these varying methodologies and to improve accuracy, the authors considered both the sectional area and circumference to determine the AC. The coronal section of AC was used as a reference for measuring distances to the MAF and to the AA so as not to violate the narrowest part of the canal since the rationale for using AC as the endpoint for intra-canal procedures is to preserve the narrowest zone of the canal which facilitate creating an apical stop to avoid overfilling and minimizing irritation and wound area of the periapical tissues.\u003c/p\u003e \u003cp\u003eThis study revealed that the AC is located at variable distances from the MAF (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), with a mean distance measured at 0.49 mm, which is found to be in agreement with the results reported by Dummer et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] in maxillary premolars which was 0.53 mm, and with the results reported by Kuttler [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] in the young age group which was about 0.52 mm without specifying the teeth type. However, the AC-MAF distance recorded in this study was greater than that reported by ElAyouti et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] in which the measured AC-MAF distance was reported to be 0.2 mm in their micro-CT study. This discrepancy may be attributed to the different types of teeth used (maxillary first premolars vs. maxillary and mandibular molars), as well as to the different reference points used for measuring distances since ElAyouti et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] used the apical extent of AC while the coronal AC extent was used in this study.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mean distance from the AC to AA measured in this study was 1.13 mm. These results were consistent with those reported by Shimizu et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] in a study of maxillary first premolars from Japanese patients. A slightly shorter AC-AA distance of maxillary premolars was reported by Dummer et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] with an average of 0.95 mm. Nevertheless, a consensus can be observed in the findings of different anatomic studies regarding the mean AC-AA distance to be fluctuating around 1 mm [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], which is in accordance with the results recorded in this study.\u003c/p\u003e \u003cp\u003eThe mean distance of MAF to AA measured in this study was 0.74 mm, and this is in agreement with the findings of several studies [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. For instance, Martos et al. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] reported that the mean MAF-AA distance in maxillary premolars was 0.67 mm, however, they measured the distance from the AA to the most apical point of the MAF not to the centre of MAF as was the case in this study. Morfis et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] reported that the mean distance from AA to the centre of MAF was about 0.82 mm in maxillary premolars. A mean MAF-AA distance of 0.7 mm has been reported by ElAyouti et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] in a study of ninety human maxillary and mandibular molars. However, a shorter MAF to AA distance of about 0.48 mm in young patients and about 0.6 mm in older patients had been reported by Kuttler [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] and a mean MAF-AA distance of about 0.42 mm had been reported by Dummer et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. These minor differences can be partially attributed to the various approaches employed in measuring the distances as well as the likely usage of varying reference points [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Additionally, it has been reported that racial differences between populations may contribute to these discrepancies [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eKnowing the probable diameters of the apical constriction or the minor apical foramen can help practitioners in getting a proper apical preparation which should be performed while avoiding excessive enlargement to the constriction [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The results of this study revealed that the mean shortest or minimum diameter of the constriction was 0.18 mm and the mean longest or maximum diameter was 0.25 mm. These findings were lower than those reported by Shimizu et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] and by Abarca et al. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], while in agreement with the findings of other studies [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The most common canal cross-sectional shape at the AC was oval (89.8%), and this is in agreement with several studies [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. This information can help in the decision-making process regarding the initial and final apical file size [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Before root canal enlargement, the initial apical file size can be estimated based on the AC minimum diameter. Since the majority of canals have an oval cross-section, the final file size should be large enough to touch every canal wall during the preparation procedures. Put another way, the master apical file size should match the longest diameter of AC to shape the canal round [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The results of this study revealed that the difference between the longest and shortest canal diameters was equal to or less than 0.15 mm in about 90% of the canals and was equal to or less than 0.20 mm in about 95% of the examined canals. According to these data, preparing the canals to 3 and 4 instrument sizes larger than the initial apical file size will turn the apical constriction into a round shape in 90% and 95% of the cases, respectively.\u003c/p\u003e \u003cp\u003eWhen the MAF is not located at the anatomical root apex tip, it is referred to as a foramen deviation, which can be resulted from both pathological and physiological conditions [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The frequency of deviated MAF in this study was 74.2%; mostly to the palatal and distal sides. These results were in close agreement with those reported by Blasković-Subat et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] and Sert, Bayirli [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Higher frequencies of deviated MAF had been reported by Vertucci, Gegauff [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] (88%) and by Burch, Hulen [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] (92.4%). However, lower frequencies of about 40% and 15% also had been reported by Awawdeh et al. [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] and Senan et al. [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e], respectively. These discrepancies between the various studies could be the consequence of using various definitions and methodologies, as well as the different population groups that each study examined [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The discrepancies in different reported data about the position of apical foramina may also be attributed to patient age and sample size [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Kuttler [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] reported that the percentage of deviated foramina in older age patients (55 years and older) was 80%, whereas the percentage in younger age patients (18\u0026ndash;25 years) was 68%. According to Stein, Corcoran [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e], there is a positive correlation between age and the deviation and diameter of the foramen opening as a result of apical cementum thickening. The results of our study, as well as those of previous studies, have revealed that the frequency of deviated MAF opening is high. This is not usually detectable on radiographic examination, especially when this deviation occurs toward the buccal or palatal root surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). For this reason and in order to prevent periodontal ligament damage, clinicians should consider this when performing root canal therapy. Root canal working length is better determined by the use of the electronic foramen locaters in combination with tactile and radiographic evaluation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThis study is among the few that have utilized the innovative micro-CT technology to investigate the apical anatomy of maxillary first premolars and the first to be held in the Iraqi population, although, this kind of teeth was reported to possess one of the most complex and variable root canal apical anatomy [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, the cost and technical limitations of the micro-CT technology were the main challenge for the sample size of the study. Furthermore, the patients\u0026rsquo; ages and the apical pathologic conditions of the collected teeth were unknown, and these may affect the location and size of the apical foramina. Therefore, conducting future studies taking into account the age and the pathologic history of the collected teeth would be valuable in providing a more comprehensive understanding of the apical anatomy.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study revealed that the apical anatomy of maxillary first premolars is variable in the studied Iraqi population and the AC is located at variable distances from the MAF with an average distance of about 0.5 mm. The MAFs deviated in 74.2% of examined root canals mostly to the palatal and distal side. The cross-sectional shape of the root canal is predominantly oval. Furthermore, shaping the canals to 4 sizes larger than the initial apical file size will turn the AC round in 95% of the examined canals.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was financially supported by UNIVERSITI MALAYA DPRG grant no. UMG002E-2022.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to acknowledge Dr. Hijaz Kamal Hasnan, Department of Geology, Faculty of Science, University of Malaya, Malaysia for his efforts in sample scanning.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA.M.A.: design, data analysis \u0026amp; interpretation, writing and revision. N.H.A.: design, data analysis \u0026amp; interpretation writing and revision. H.M.A.A.: design, data analysis \u0026amp; interpretation writing and revision. N.I.: design, data analysis \u0026amp; interpretation and revision. A.A.A.: design, data analysis \u0026amp; interpretation and revision.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbarca, J. et al. Morphology of the Physiological Apical Foramen of Maxillary Premolars. \u003cem\u003eInt. J. Morphology\u003c/em\u003e ;\u003cb\u003e36\u003c/b\u003e(1). 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Root form and canal morphology of maxillary first premolars of a Yemeni population. \u003cem\u003eBMC Oral Health\u003c/em\u003e. \u003cb\u003e18\u003c/b\u003e (1), 1\u0026ndash;10 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStein, T. J. \u0026amp; Corcoran, J. F. Anatomy of the root apex and its histologic changes with age. \u003cem\u003eOral Surg. Oral Med. Oral Pathol.\u003c/em\u003e \u003cb\u003e69\u003c/b\u003e (2), 238\u0026ndash;242. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/0030-4220(90)90334-o\u003c/span\u003e\u003cspan address=\"10.1016/0030-4220(90)90334-o\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e (1990).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Apical anatomy, Apical constriction, Iraqi population, Maxillary first premolar, Micro-computed tomography","lastPublishedDoi":"10.21203/rs.3.rs-8744979/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8744979/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjectives\u003c/h2\u003e \u003cp\u003eTo investigate the apical root canal anatomy of maxillary first premolars in an Iraqi sub-population using micro-computed tomography (micro-CT).\u003c/p\u003e\u003ch2\u003eMaterials and Methods\u003c/h2\u003e \u003cp\u003eA total of 151 extracted maxillary first premolars were collected and scanned using micro-CT. Images were segmented and three-dimensionally (3D) reconstructed using Mimics software. The apical constriction (AC) for each canal was located and distances were measured from the AC to the major apical foramen (MAF), to the anatomic apex (AA) and from MAF to AA. The longest and shortest canal diameters at AC were also measured. The cross-sectional canal shape at the AC and the direction of the MAFs were determined. Qualitative data were analysed using the Chi-Square test while quantitative data were analysed with the Independent-Samples T-test and One-Way ANOVA with Bonferroni post hoc tests and respective non-parametric tests at a significance level of 0.05.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eOut of the 151 included maxillary first premolars, 82 (54.3%) were double rooted and 69 (45.7%) were single-rooted. The mean AC-MAF, AC-AA and MAF-AA distances were 0.49 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32 mm, 1.13 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.56 mm and 0.74 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49 mm, respectively. The AC to AA and MAF to AA distances were significantly larger in the palatal canals compared to both the buccal and single canals (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The mean shortest and longest canal diameters at the AC were 0.18 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06 mm and 0.25 mm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 mm, respectively, with 89.8% of the canals having oval cross-sectional shapes at AC. The two diameters were significantly smaller in the buccal canals compared to the palatal and single canals (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In 74.2% of the canals, the MAFs were deviated to one of the root sides, mostly to the palatal and distal aspects.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe apical anatomy of maxillary first premolars is complex and variable in the studied Iraqi population. The majority of the canals had oval cross-sectional shapes at the AC with majority of MAFs showing deviation from the root axis.\u003c/p\u003e","manuscriptTitle":"Apical Anatomy of Maxillary First Premolars in an Iraqi Sub-Population: A Micro Computed Tomographic Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-22 16:29:12","doi":"10.21203/rs.3.rs-8744979/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"928e1a6e-8b16-430b-b6ad-c7741cafc34d","owner":[],"postedDate":"February 22nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":63219815,"name":"Health sciences/Anatomy"},{"id":63219816,"name":"Health sciences/Health care"},{"id":63219817,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2026-05-18T06:24:24+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-22 16:29:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8744979","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8744979","identity":"rs-8744979","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}