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ORIGINAL ARTICLE
Year : 2021  |  Volume : 11  |  Issue : 3  |  Page : 315-320

Root and root canal morphology of permanent mandibular incisors in a Kuwaiti subpopulation: A cone-beam computed tomography study


1 Endodontic Unit, Farwaniya Specialized Dental Center, Dental Administration, Ministry of Health, Kuwait
2 Endodontic Unit, Farwaniya Specialized Dental Center, Dental Administration, Ministry of Health, Kuwait and Restorative Dentistry Department, College of Dentistry, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia
3 Dentistry Department, Al-Wakra Hospital, Hamad Medical Corporation, Al-Wakra, Qatar
4 Department of Oral Medicine and Diagnostic Sciences, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia
5 Director of Quality Assurance and Accreditation Center, Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia

Date of Submission03-Jan-2021
Date of Decision12-Feb-2021
Date of Acceptance06-Mar-2021
Date of Web Publication3-Sep-2021

Correspondence Address:
Dr. Mohammad Ahmad Alenezi
Endodontic Unit, Farwaniya Specialty Dental Center, Dental Administration, Ministry of Health, Kuwait. Postal Box 81004, Farwaniya
Kuwait
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_3_21

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  Abstract 

Introduction: Sound knowledge of the external and internal anatomy of different teeth is an important prerequisite for successful endodontic treatment. The purpose of this in vivo study was to evaluate the root and root canal morphology of permanent mandibular incisors among a Kuwaiti subpopulation using cone-beam computed tomography (CBCT).
Materials and Methods: A total of 600 Kuwaiti patients' CBCT images were screened and evaluated. A total of 1200 mandibular central incisors and 1200 lateral mandibular incisors were studied. The root canal morphology was recorded using Vertucci's classification and the association between the total number of root canals and patient's gender, tooth type (central vs. lateral incisor), and tooth location (right vs. left) were analyzed using Pearson's Chi-square test.
Results: The prevalence of two canals in mandibular central incisors and lateral incisors was 24% and 27%, respectively. In both incisors, Type I root canal configuration was the most common (74.5%) followed by Types III and II. The total number of root canals per tooth was significantly higher in the central (P < 0.00001) and lateral (P = 0.00002) incisors in males compared to females, while tooth type and location had no effect on the number of root canals.
Conclusion: Within the limitations of this clinical study, Type I root canal configuration was the most common root canal configuration of the mandibular incisors. The prevalence of two canals was significantly higher in males compared to females.

Keywords: Cone-beam computed tomography, Kuwaiti population, mandibular incisors, root canal morphology


How to cite this article:
Alenezi MA, Albutaihani FA, Ahmad IA, Aldosimani MA, Al-Omari M. Root and root canal morphology of permanent mandibular incisors in a Kuwaiti subpopulation: A cone-beam computed tomography study. Saudi Endod J 2021;11:315-20

How to cite this URL:
Alenezi MA, Albutaihani FA, Ahmad IA, Aldosimani MA, Al-Omari M. Root and root canal morphology of permanent mandibular incisors in a Kuwaiti subpopulation: A cone-beam computed tomography study. Saudi Endod J [serial online] 2021 [cited 2021 Dec 1];11:315-20. Available from: https://www.saudiendodj.com/text.asp?2021/11/3/315/325408


  Introduction Top


An adequate understanding of the root and root canal anatomy of adult human teeth is essential for successful root canal therapy. The lack of ability to find, prepare or fill the root canal system is a major reason of posttreatment pathosis and treatment failures.[1],[2] Thus, the clinicians should be aware with common and uncommon root canal configuration of different teeth types to improve the outcome of root canal treatment.[3]

The mandibular incisors are the smallest teeth in the oral cavity and although they are infrequently cariously involved, they oftentimes demand endodontic treatment. Through times, many in vivo and in vitro techniques have been used to evaluate the root and root canal morphology of mandibular incisors [Table 1]. The mandibular incisor teeth commonly have a single root and one root canal. Nevertheless, variations in the number of root canals in these teeth have been reported and the prevalence of a second canal ranged from 11% to 62%.[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23] Differences in the results of these studies may be related to the difference of examination technique, patient's age, gender, ethnic background, and sample size of the population.[4],[8],[10]
Table 1: Sample of previous studies reporting on the morphology of mandibular incisors

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During the last decade, the employment of cone-beam computed tomography (CBCT) in endodontic field has increased rapidly worldwide. CBCT is an important noninvasive tool for proper diagnosis of the root canal system and for obtaining more information regarding the complexity nature of root(s) and root canals anatomy.[24]

The state of Kuwait is located in the Middle East region and the population of Kuwait is approximately of 1.4 million. Up to date, only one clinical study investigated the morphology of mandibular incisors in the Kuwaiti population was published using a conventional radiographic technique.[12] The purpose of this clinical study was to examine the root and root canal morphology of permanent mandibular incisors teeth in a Kuwaiti population using CBCT and to determine whether the prevalence of additional canals in these teeth is affected by the patient's gender, tooth type, or location.


  Materials and Methods Top


The approval of this clinical study was obtained through the ethics committee of Riyadh Elm University, Riyadh, Kingdom of Saudi Arabia. The research registration number was FPGRP/43833003/297.

Study sample

A total of 3982 CBCT images of Kuwaiti patients attending to five different specialized dental centers at the Ministry of Health in the State of Kuwait were reviewed. The CBCT images were exposed between 2016 and 2019 for various dental diagnostic and treatment planning purposes and not specifically exposed for this study.

The patients CBCT images were taken using an i-CAT machine (Imaging International Sciences, Hatfield, Pennsylvania, USA) using the following settings: 120 kv, 80 mA, 8.9s exposure time and 0.4 mm voxel size. All CBCT exposures were carried out with the least required exposure dose for adequate image quality.

Inclusion criteria

The CBCT images were included in the analysis if they had good quality without artifacts that prevent correct analysis; had all mandibular central and lateral incisor teeth with fully formed root apices without previous root canal treatment, periapical lesions, carious lesions, and resorption or canal calcification.

Radiographic evaluation

The CBCT images were analyzed using RadiAnt software (Medixant, Poland) by two experienced examiners: An endodontist and an oral and maxillofacial radiologist. The images were numbered and evaluated separately to achieve conformity and avoid any potential sources of bias. In case of disagreement, a joint meeting was made to discuss the cases until a consensus was reached. Three planes (axial, sagittal, and coronal) sections of the CBCT images were displayed in the LCD screen of 32-inch Monitor (HP Inc., USA) with a resolution of 1280 × 1024 pixels. The images were examined in a dark room and adjustments of magnification and contrast were done to ensure optimal visualization and careful examination. The data reliability was previously performed and assessed through an interexaminer calibration based on the anatomic diagnosis of CBCT images.

The included CBCT images were analyzed and the following informations were recorded:

(i) incisor's type (central vs. lateral) and location (right vs. left), (ii) the number of roots per tooth, (iii) the root canal configuration in each tooth according to Vertucci's classification,[1] and (iv) total number of root canals per tooth defined as the largest number of root canal(s) observed in the tooth at any level.

The data were tabulated and analyzed through SPSS version 25.0 (Chicago, IL, USA) software. The root canal configurations and the total number of canals per tooth in the mandibular central and lateral incisors were expressed as frequencies and percentages. Pearson's Chi-square test was used to analyzed if the total number of canals differed significantly between central and lateral mandibular incisors and to evaluate the effect of gender and tooth location on the total number of canals in each of these teeth. For all comparisons, the statistical level of significance was set at P < 0.05.


  Results Top


A total of 2400 mandibular incisors (1200 central and 1200 laterals) from 600 patients (216 males and 384 females) were evaluated. All of the mandibular central and lateral incisors had a single root (100%). [Table 2] summarizes the root canal configurations and the total number of canals observed in this study.
Table 2: Root canal morphology of mandibular central and lateral incisors

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Type I root canal configuration was the most common configuration (76%) in central incisors followed by Types III (15.7%) and II (8.3%). About 73% of lateral incisors had Type I, while 18.7% and 8.3% of them had Types III and II, respectively. There was no significant difference in the total number of canals between the central and lateral incisors (χ2 = 2.82, P = 0.09). [Figure 1] and [Figure 2] illustrate sample of the different root canal morphologies that were found in this study.
Figure 1: Axial planes of n scanning at middle third of mandibular incisors: (a) single root canal and (b) two root canals

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Figure 2: Cone-beam computed tomography images of mandibular incisors: (a) type I; (b) type II; (c) type III

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The associations between the patient's gender and tooth location and the total number of canals in both incisors types were also studied. The results showed that males had a significantly higher prevalence of two canals in both the central (χ2 = 20.71, P < 0.00001) and lateral (χ2 = 18.05, P = 0.00002) incisors than females. On the other hand, the location of the tooth had no effect on the number of canals in both incisors.


  Discussion Top


The previously reported study of Zaatar et al.[12] had two major limitations: Only 21 mandibular incisors (13 central and 8 lateral incisors) were included and the morphology was assessed using the conventional, two-dimensional radiographic technique. The present study attempted to overcome these limitations using the CBCT technique which allows three-dimensional evaluation of the teeth using a relatively larger sample size.

In the current study, all of the mandibular incisors had one root while one root canal was reported in 76% and 73% of central and lateral incisors, respectively. The prevalence of the second canal in these teeth was generally in agreement with a number of previous studies.[7],[14],[16],[21] Other studies reported either a lower[11],[20] or higher[9],[10],[18],[22] prevalence of the second canal. These conflicting results emphasize the importance of interpreting the results of each individual study in the context of its study population, sample size, and the methods used to assess the root canal morphology.

The most common root canal configuration observed in this study was Type I followed by Types III and II. Similar findings were reported by the majority of the studies that evaluated the internal morphology of mandibular incisors.[7],[16],[17],[18],[19] However, it is interesting to point out that some studies have reported more complex root canal configurations including types (V-VIII) as well as other types.[9],[10],[13],[16],[18],[19],[21],[22],[23]

The current study investigated the effect of patient's gender, tooth type (central vs. lateral), and location (right or left) on the total number of canals in mandibular incisors. The results showed that while the number of canals did not differ according to tooth type and location, males had a significantly higher prevalence of a second canal compared to females. These findings are in agreement with previous studies.[17],[18],[19],[21] The age of the patient is another factor that may affect the results of anatomical studies and it has been hypothesized that as the age increases, deposition of secondary dentin on the canal walls may cause obliteration of the root canal space.[25] Unfortunately, the age of the patients involved in the current study was not recorded at the time of radiographic examination and this should be considered as a limitation of this study.

Careful assessment of the preoperative periapical radiographs is essential to evaluate the root canal morphology of the involved teeth. Sudden narrowing or even complete disappearance of the root canal on conventional radiographs taken from the “straight on” view may indicate root and/or root canal division and a second radiograph exposed at a different horizontal angulation may confirm this finding.[26],[27] CBCT may be also helpful in the diagnosis and treatment of teeth with abnormal root canal anatomy as it allows a 3-dimensional assessment of the involved tooth and the surrounding structures.[24]

The voxel size may affect the accuracy of CBCT images. In 2011, Bauman et al.[28] evaluated the effect of changing the voxel size (0.125, 0.2, 0.3, and 0.4 mm) on detection of the second mesiobuccal canal in extracted maxillary molars. They found that the detection of the second canal increased from 60.1% at 0.4 mm voxel size to 93.3% at 0.125 mm voxel size. One of the limitations of the current study is that all the voxel size of the machines in the five specialized centers was fixed at 0.4 mm that might affect the ability to detect more complex anatomical configurations. This should be considered as a limitation while interpreting the results of the current study.

One of the important anatomical features of the mandibular incisors is the discrepancy between the buccolingual and mesio-distal dimensions, with the former being wider than the latter.[6] This discrepancy has important implications on access preparation, biomechanical preparation, and obturation of the entire root canal system. The preparation of the access cavity on the lingual surface should be extended buccolingual from the cingulum of the tooth up to the incisal edge to allow straight-line access to the root canal system.[29] This will help in locating additional root canals which are usually located in the lingual side of the tooth and are likely to be missed with restricted access cavity preparations.[6]

Nowadays, magnification tools such as magnifying loupes or dental operating microscope are recommended as a standard of care in endodontic therapy. In fact, these devices are very helpful in locating and management of anatomical variations such as extra canals and isthmuses and have been shown to significantly improve the clinical outcome of endodontic treatment.[30]

The current study provided important anatomical features on mandibular incisors in the Kuwaiti population. Nevertheless, it is recommended to carry out more clinical studies on the morphology of these teeth using larger sample size and include samples from private dental centers. In addition, it is important to include other variables such as the age of the patient and the level of canal furcation in future publications and use smaller voxel size resolution to enhance the accuracy of CBCT images.


  Conclusion Top


In the present study, Type I root canal configuration was the most common root canal configuration of the mandibular incisors within a Kuwaiti population. About 24% of central and 27% of lateral incisors had two root canals and the prevalence of the second canal was significantly higher in males compared to females.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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