A Cross-Sectional Cone-Beam Computed Tomography Study of Root Canal Morphology and Configuration of Mandibular Premolars in Saudi and Sudanese Subpopulations

Abstract Objective  To evaluate and compare the root canal morphology of mandibular premolars in Saudi and Sudanese subpopulations and between males and females within each group using cone-beam computed tomography (CBCT). Materials and Methods  A cross-sectional study was done between May 2022 and July 2023. Six hundred premolars from Saudi and Sudanese subpopulations were evaluated using CBCT for their number of roots, type of root canal configuration based on Vertucci's classification, and average canal length measured from the buccal cusp tip to the root end. Statistical Analysis  Statistical comparisons were made between males and females within each subpopulation and the two subpopulations using the chi-square test for root number and type of root canal configuration and an independent sample t -test for the canal length. Results  Most mandibular premolars in both subpopulations had a single root, with type I root canal configuration. However, Sudanese showed various canal configurations (I, II, III, IV, and V) compared with Saudis, which was statistically significant in the first canal of the first mandibular premolar ( p  < 0.05). Also, there were statistically significant differences in canal length between Saudi males and females ( p  < 0.05) and between Saudis and Sudanese ( p  < 0.05) in the first and second premolars. Conclusion  Although most mandibular premolars in Saudi and Sudanese subpopulations exhibited a single root and type I canal configuration, variations exist between and within the groups, highlighting ethnic and gender differences and emphasizing the need for dentists' attention.


Introduction
The main aim of endodontic treatment is to remove any microbial contamination from the entire root canal system using mechanical and chemical debridement and threedimensionally seal the root canal system to prevent recontamination. 1,2The internal anatomy of the root canal system can affect the mechanical and chemical debridement since a single canal can be divided into several canals and fuse at any point along the length of the root canal system. 3,4The root canal anatomical variations (root canal configuration) were studied and evaluated by Vertucci 5 into eight types according to the number of canals, orifices, and divisions along its course.
Radiographic evaluation of the root canal configuration before endodontic treatment is essential to determine the type of root canal configuration and, hence, the anatomical complexity of the root canal system. 6Periapical radiographs may not provide enough detail about the root canal structure because the three-dimensional anatomy of the radiographed area is compressed into a two-dimensional image, leading to overlapping structures. 7In 1973, Hounsfield developed the first computed tomography device to capture different tissues in a three-dimensional view. 8Cone-beam computed tomography (CBCT) is a type of radiograph that enables the viewing of objects in three dimensions (axial, sagittal, and coronal), hence better visualization of root canal internal anatomy 9 and visualization of accurate geometry of scanned objects. 10ost of mandibular premolars possess single canal and a single periapical foramen. 113][14][15] Proper knowledge of this anatomical variation is critical because it can affect the outcome of root canal treatment, especially in places with different ethnic groups.Saudi Arabia and Sudan are well known for their population mix.7][18] A recent study 18 reviewed the root canal configuration of mandibular premolars in the Saudi subpopulation.They found that most mandibular first premolars had a single root (86.6%), with a single canal (91.5%) and type I root canal configuration (96.9%).
The literature is lacking studies that evaluate the root canal morphology of mandibular premolar in Sudanese population.Therefore, this study aimed to evaluate and compare the number of roots, type of root canal configurations, and the average canal length of mandibular first and second premolars in the Saudi and Sudanese subpopulations using CBCT images.

Materials and Methods
A cross-sectional descriptive study was done between May 2022 and July 2023.The CBCT images were collected from the dental complex at King Faisal University in Al-Hasa (Saudi Arabia) and the 3D Scan Centre, Dental Radiology Centre in Khartoum (Sudan).Ethical approval was obtained from the ethical research committee at King Faisal University, Saudi Arabia (KFU-REC-2023-JUN-ETHICS1008).A written permission was obtained from both centers to access their CBCT image databases.All patients' data were kept anonymous.
The samples were collected using convenience sampling.The inclusion criteria for this study were: Sudanese and Saudis (males and females), !18 years, presence of one of the mandibular premolars on either side (right or left) with no congenital disturbances or anomalies.The exclusion criteria involved the presence of previous root canal treatment, complex restorations, or extensive carious lesions, along with the presence of root resorption or periapical lesions.The collected data included 359 CBCT images.

CBCT Technique
One hundred eighty-three CBCT images were evaluated for the Saudis using I-CT Vision QTM (Imaging Sciences International, Hatfield, Pennsylvania, United States).The CBCT images were captured at a voltage of 120 kV, a current of 5 mA, and a field of view of 13 Â 16 cm with a voxel size of 250 m.The CBCT images were evaluated with the Vision i-CT software program's measurement tool (version 1.9.3.14, Imaging Sciences International).For the Sudanese, 176 CBCT images were evaluated.The images were captured using Planmeca ProMax 3D Classic (Helsinki, Finland) at 90 kV voltage, 12 mA current, 160 m voxel size, and 88 cm field of view.The images were viewed and evaluated using Planmeca Romexis Viewer software (version 6.1.0.997,Helsinki, Finland).

Image Analysis
The total number of premolars evaluated was 600, 300 from the Saudis and 300 from the Sudanese; 150 first and 150 second premolars were evaluated in each subpopulation.The patient's gender was recorded, corresponding to the CBCT image captured.Each premolar was viewed in three different plans (coronal, sagittal, and axial) (►Fig.1) using Vision i-CT software for the Saudis and Planmeca Romexis Viewer software for the Sudanese.Each premolar was evaluated for the number of roots, type of root canal configuration (according to Vertucci's classification), and canal length measured from the buccal cusp tip to the apex (measured with the Vision i-CT software and Planmeca Romexis Viewer software measuring tools).The observers were trained and calibrated with another senior staff from the radiology department.Three observers analyzed each image of each subpopulation.

Statistical Analysis
The data were collected, organized, and analyzed using Statistical Package for Social Sciences (SPSS) software (version 25; IBM, Armonk, New York, United States).A descriptive analysis was performed following data collection.Furthermore, a comparison was made between Saudi and Sudanese regarding the number of roots and type of root canal configuration present in first and second mandibular premolars using the chi-square test.A comparison was also made between the average root canal length of the first and second mandibular premolars in Saudi and Sudanese using the independent sample t-test.

Results
In this study, 600 mandibular premolars were evaluated, 300 from the Saudis and 300 from the Sudanese; 150 first and 150 second premolars were evaluated in each subpopulation.The percentage of male and female participants in the Saudi were 57 and 43%, respectively, and 35 and 65% in the Sudanese, respectively (►Fig.2).
Saudi males had single roots in 95.5 and 98.8% of their first and second mandibular premolars, respectively.However, two roots were observed in 4.5% of male participants' first premolars and 1.2% of male participants' second premolars.Furthermore, females had only one root in their first and second premolars.There was no statistical difference between males and females in the number of roots in the first (p ¼ 0.089) and second mandibular premolars (p ¼ 0.367).In the Sudanese subpopulation, the percentage of single roots observed in the first mandibular premolar was 88.9% in male participants and 95.8% in female participants; 11.1% of male participants had two roots compared with 4.2% of females, with no statistical difference between males and females (p ¼ 0.102).Furthermore, most mandibular second premolars had a single root (92.2% in males and 99% in females), compared with two roots in 7.8% of male participants and only 1% in female participants.There was a statistical difference between Sudanese males and females (p ¼ 0.027) in the number of roots of the second mandibular premolars (►Table 1).Clinically, it is important to consider the possibility of a second root, especially in Saudi male patients and in all Sudanese patients.
When the number of roots was compared based on population, the percentage of single and two roots in the first premolar of the Saudis was 97.3 and 2.7%, respectively, compared with 93.3% (single root) and 6.7% (two roots) in Sudanese.There was no statistical difference regarding the number of roots in the first mandibular premolar between the Saudis and Sudanese (p ¼ 0.101).On the other hand, the second mandibular premolar was single rooted in 99.3% and two roots in 0.7% of Saudis compared with 96.7% (single root) and 3.3% (two roots) in Sudanese.Again, there was no statistical difference regarding the number of roots in the second mandibular premolar between the Saudis and Sudanese (p ¼ 0.099) (►Table 2).
Each root was evaluated for the canal configuration type according to Vertucci's classification.The majority (98%) of mandibular first premolars in the Saudi subpopulation had a type I root canal configuration, followed by type V (1.3%), with type III being the least common (0.7%).Similarly, the second mandibular premolar of the Saudi subpopulation showed type I root canal configuration as a major type observed (98.7%), followed by type V (1.3%).For the Sudanese subpopulation, the root canal configurations of the first mandibular premolar showed type I (82%), III (10.7%),IV (0.7), and V (6.7%) in the first root.The second mandibular premolar showed type I (96%), II (0.7%), III (0.7%), and V. (2.7%) root canal configurations.If a second root was present in the first or second mandibular premolar, type I was the only root canal configuration observed in both subpopulations.When the two subpopulations were compared, there was a statistically significant difference in the types of root canal configurations observed only in the first mandibular premolar (p < 0.05).This finding suggests that dental practitioners should pay greater attention to the unique anatomical characteristics of the Sudanese population when performing root canal treatments in mandibular premolars.Proper identification and management of these variations can help ensure optimal outcomes and reduce the risk of complications.The distribution of different types of canal configurations observed in Saudis and Sudanese based on gender is represented in ►Table 3.
The mean length of the first canal in Saudi's single-rooted first mandibular premolar was 19.4 mm, and 19.5 mm if a second canal was present.In the case of two roots, the second root had a mean canal length of 20.4 mm.The mean length of the second mandibular premolar was 19.9 mm, and 19.8 mm if a second canal was observed in a single-rooted tooth.On the other hand, a second root (if present) had a mean canal length of 21.95 mm.

Discussion
Detection of anatomical variations of the root canal system prior to endodontic treatment is essential and valuable to predict the difficulty of endodontic treatment.Hence, optimal treatment options can be delivered.CBCT is one of the radiographic images that allows an in-depth and better understanding and visualization of the internal and external root anatomy (root canal system) and to detect any periapical pathology in a three-dimensional view. 19,20][15] In this study, it was difficult to standardize the protocol for CBCT images as two different devices were used in Saudi and Sudan, which may compromise the collection of standardized images for comparison.A similar device is recommended in future studies to reduce the possible error during comparison.The CBCT images analyzed in this study represent only a sample of the population attending the two radiological centers at the time of the study, which may be one of the study's shortcomings and may not provide a complete representation of both populations.However, the Fig. 2 The frequency (percentage) of first and second mandibular premolars according to gender among Saudis and Sudanese subpopulation.
Table 1 The distribution (percentage and frequency) of root canal configurations observed in Saudis' and Sudanese's

Fig. 1
Fig. 1 Sagittal view (A) showing two roots of mandibular second premolar, Coronal view (B) showing type III of root canal configuration, and axial (C) views exhibiting two canals of mandibular first and second premolars.
The single-rooted first mandibular premolars in the Sudanese had a mean length of 20.29 mm in the first canal and 20.52 mm in the second canal, if present.The average canal length when a second root was present was 18.98 mm.The mean canal length of a single-rooted second mandibular premolar was 20.54 mm in the first canal, and 21.10 mm if the second canal was present.The mean canal length of the second root (if observed) was 19.87 mm.The mean length of each canal in Saudi and Sudanese males and females is presented in ►Table 4. By comparing the two subpopulations, there was a statistical difference in the root canal length of the first and second mandibular premolars if a single root was observed (p < 0.05) (►Table 5).
Abbreviations: N, number; SE, standard error.a Significant with independent t-test.

Table 2
Comparison between males' and females' root canal length observed in Saudi and Sudanese subpopulations' first and second mandibular premolars Root Canal Morphology of Mandibular Premolars in Saudi and Sudanese Subpopulations Salah et al.
a Significant with independent t-test European Journal of General Dentistry © 2024.The Author(s).

Table 3
The distribution (percentage and frequency) of root canal configurations observed in Saudis' and Sudanese' a Significant with Chi-square test.

Table 4
Comparison between males' and females' root canal length observed in Saudi and Sudanese subpopulations' first and second mandibular premolars