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ORIGINAL ARTICLE
Year : 2022  |  Volume : 12  |  Issue : 2  |  Page : 186-194

Cone-beam computed tomographic study of root morphology, canal configuration, and bilateral symmetry of mandibular first and second molars in a Qatari population


Hamad Dental Center, Hamad Medical Corporation, Doha, Qatar

Date of Submission26-Aug-2021
Date of Decision17-Oct-2021
Date of Acceptance05-Nov-2021
Date of Web Publication20-Apr-2022

Correspondence Address:
Dr. Fatima A Al-Sheeb
Hamad Dental Center, Hamad Medical Corporation, P.O. Box 3050, Doha
Qatar
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/sej.sej_176_21

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  Abstract 

Introduction: Identifying root and canal morphology are essential for successful endodontic treatment. The study aimed to identify the anatomical variation and the bilateral symmetry of mandibular first and second molars among the Qatari population using cone-beam computed tomography (CBCT).
Materials and Methods: Two endodontists reviewed 544 CBCT images of Qatari patients. Age, gender, root morphology, and canal configuration according to Vertucci classification, were recorded. A descriptive analysis was implemented to provide a detailed characterization of the root morphology, root canal configuration, and symmetry between right and left teeth. Kappa agreement analysis was performed to assess the intra- and inter-examiner agreement.
Results: A total of 195 mandibular first molar (MFM) and 255 mandibular second molar (MSM) were included in this study. The most commonly observed number of roots in both molars was two in 96.4% of MFMs and 92.9% of MSMs. The majority of MFMs and MSMs had three canals, 79% and 74.2%, respectively. The most common root canal configuration of the mesial root was type IV, found in 66.5% of MFM and 57.8% of MSM. Type I was the most common root canal configuration of the distal roots in 56.9% of MFM and 87.3% of MSM. The symmetrical analysis revealed a high symmetry in the number of the roots. However, the symmetry of the number of canals per root drops to around 75%.
Conclusions: Mandibular first and second molars had predominantly two roots with three canals. Variations such as single, three, or four roots and C-shaped canal morphology were also detected and were associated mainly with mandibular second molars.

Keywords: Cone-beam computed tomography, mandibular molar, Qatar, root canal morphology, symmetry


How to cite this article:
Al-Sheeb FA, Diab HI, Al Obaid MM, Diab AI, Lari MG, Mahmoud NM. Cone-beam computed tomographic study of root morphology, canal configuration, and bilateral symmetry of mandibular first and second molars in a Qatari population. Saudi Endod J 2022;12:186-94

How to cite this URL:
Al-Sheeb FA, Diab HI, Al Obaid MM, Diab AI, Lari MG, Mahmoud NM. Cone-beam computed tomographic study of root morphology, canal configuration, and bilateral symmetry of mandibular first and second molars in a Qatari population. Saudi Endod J [serial online] 2022 [cited 2022 Nov 30];12:186-94. Available from: https://www.saudiendodj.com/text.asp?2022/12/2/186/343553


  Introduction Top


The endodontic treatment's success depends on thorough biomechanical instrumentation, effective chemical debridement, and adequate obturation of the root canal system with biocompatible material. The root canal system is complex, and it varies not only between different teeth but also in one particular tooth among different individuals. Identifying root and canal morphology, which is thought to be racially and genetically determined, is essential for successful endodontic treatment.[1] Incorrect identification of the root morphology and the number of canals is the second-most-important cause of treatment failures after wrong diagnosis and treatment planning.[2]

The first permanent tooth to erupt is the mandibular first molar (MFM), making it more vulnerable to be affected with dental caries and, consequently, require endodontic treatment with its complex anatomy. In Qatar, the maxillary and mandibular molars exhibited the highest incidence of dental caries among 12–14 years old school children,[3] which indicates high demand for endodontic therapy. Thus, it is essential to know the molars' root morphology and canal configuration for better endodontic management and to increase success rate of the therapy.

In general, mandibular first and second molars have two roots with two canals in the mesial root and one in the distal root.[4] However, variations like single, three, and four roots with a different number of canals have been demonstrated in many studies.[4],[5],[6] While the incidence of single-rooted MFMs is uncommon (0.2%–1.7%), a higher incidence was observed associated with MSMs (1.5%–46.8%) especially in the Asian population.[5] Three-rooted mandibular molars are more prevalent in MSMs.[4] According to the literature, a third root is a very common anatomical characteristic of the Mongoloid and the Asian populations.[6] Contrariwise, Saudi, Kuwaiti, and Jordanian populations have a low incidence of three-rooted mandibular molars, 5.97%, 4%, and 4%, respectively.[7],[8],[9] C-shaped canal morphology is another variation observed in mandibular molars. The prevalence of C-shaped canals in MFMs ranged from 0% to 1.7%, while MSMs varied extensively among different regions (0.4% to 44%).[5],[10],[11]

Numerous methods have been used to analyze the root and root canal morphology, such as canal staining and tooth clearing, sectioning, and modified root canal staining techniques.[4] Conventional radiographs, digital radiographs, and radiographic assessment enhanced with contrast media have also been used.[12],[13],[14] More recently, cone-beam computed tomography (CBCT) and micro-computed tomography (micro CT) have been valuable tools for studying root morphology.[15] Micro CT is an advanced radiologic technique used for the ex vivo study of dental anatomy; it can provide a detailed quantitative and qualitative description of the teeth' external and internal anatomy.[4],[16]

To the best of our knowledge, no studies have evaluated the root morphology of permanent mandibular molars in the Qatari population. Therefore, this study aims to identify the variations in the root morphology and the canal configuration of the first and second mandibular molars among the Qatari population using CBCT images. In addition, the bilateral symmetry of these teeth will be evaluated.


  Materials and Methods Top


Sample selection

This retrospective descriptive study was performed with the approval of the Medical Research Center and the Institutional Review Board at Hamad Medical Corporation (ethical approval number: 17228/2017). The study sample was made up of Qatari patients referred for dental treatment from 23 Primary Health Care Centers in different regions of the State of Qatar. A total of 544 CBCT records of Qatari patients between 2014 and 2016 were included in the sample. The CBCT images were all performed by expert radiologists for different treatment purposes such as examination, diagnosis, or treatment planning.

Cone-beam computed tomography and image analysis

A D I-CAT scanner (Imaging Sciences International, Hatfield, Pennsylvania, United States) was used for CBCT imaging. It was operated with 120 kVp (eff) tube voltage, 20 mA tube current, for 14.7 s, with a Voxel size of 0.4–0.2 mm, and a field of view of 160 mm × 40 mm. The CBCT images were reviewed by two endodontists with more than 10 years of clinical experience independently. The images were scrutinized through the sagittal, coronal, and axial views. Three-dimensional reconstruction of the jaws was applied when required, using Infinite software (Infinitt, Seoul, South Korea), version 11.4, and Xelis Dental 3D Viewer software, version 1.0. As an initial step, 20% of the sample was viewed by each endodontist separately to measure the inter-examiner agreement. After 3 weeks, the sample was viewed with the same endodontist again to measure the intra-examiner agreement.

Data collection

Each patient was given a code to protect their identities. The data collected were as follows: The age and gender of the patient; inclusion or exclusions and the reason for exclusion; tooth type and location; the number of roots; the number of canals in each root; canal configuration type according to Vertucci classification.[17] Any additional types were recorded as complex anatomy and referred to as numbers of canals. For example, 1-3-1 means that the canal started as one, then split into three canals, and then finally joined at the end into one canal. The teeth included in this study were selected according to the following criteria: (1) permanent teeth with fully formed roots; (2) no intracanal or extra radicular restorations; (3) no apical pathosis; (4) no calcification of the canals or resorption; (5) clear CBCT images with no artifact. When the teeth were excluded, the reason for their exclusion was mentioned.

Statistical analysis

The statistical analysis was performed using SPSS, version 20 (SPSS Inc., Chicago, IL, US). A descriptive analysis was implemented to provide a detailed characterization of the root morphology and root canal configuration. This analysis included frequency, percentages, mean and standard deviation. A descriptive analysis was also used to compare the right teeth to the left. A Kappa agreement analysis was performed to assess the inter-examiner and intra-examiner agreement.


  Results Top


A total of 544 CBCT records were evaluated. The inter-examiner agreement result was 91.5%, and the intra-examiner agreement was 91.7%.

Mandibular first molar

A total of 1088 MFMs were evaluated. Only 195 teeth met the inclusion criteria (17.9%). Among them, 123 teeth (63.1%) belonged to females, and 72 (36.9%) belonged to males. The patients' age ranged from 11 years to 76 years, with an average of 32.8 years. The teeth were excluded mainly due to tooth loss (386, teeth), restorations (197), and 105 teeth were root canal treated.

Root morphology

The number of the roots most frequently observed in the MFM was two, in 188 teeth (96.4%). The presence of three roots was only observed in seven teeth (3.6%). The extra root detected was located in the distolingual side in six of the teeth. Only one tooth was found to have an extra root extending from the mesial root [Figure 1].
Figure 1: Axial view of cone-beam computed tomography image showing example of three rooted mandibular first molar. (a) Showing the extra distolingual root (radix entomolaris) and (b) showing the extra mesial root (radix paramolaris)

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Number of canals per root

The number of the canals most commonly observed in the two-rooted teeth was two canals in 176 mesial roots (90.3%) and one canal in 166 distal roots (85.1%). Four canals were detected in 22 teeth (11.3%) with two roots and 6 teeth (3.1%) in three-rooted teeth. Single canal in the mesial roots was only observed in 12 teeth (6.2%). One of the three-rooted teeth had a single canal in each root (0.5%).

Root canal configuration

In the two-rooted teeth, the root canal configuration observed was mainly type IV Vertucci in the mesial root of 125 teeth (66.5%) [Figure 2]. Type II Vertucci was also observed in 45 teeth (24.1%). The presence of other Vertucci types in the mesial roots was rare, as shown in [Table 1]. Vertucci type I configuration predominated in the distal roots in107 teeth (56.9%), followed by type III in 41 teeth. In the three-rooted MFMs, Vertucci type I was observed in all the roots except for six mesial roots. Three had Vertucci type II, and three had type IV [Table 1].
Table 1: The classification of the mandibular first molar root canal configuration according to Vertucci classification (n=195)

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Figure 2: Coronal view of cone-beam computed tomography image showing mesial root of mandibular left first molar with class IV Vertucci canal configuration (2-2)

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Symmetry between left and right mandibular first molar

The sample included 57 patients with both right and left MFMs. Of these, 54 patients (94.7%) had a symmetrical number of roots in both right and left First Molar. The symmetrical teeth predominantly had two roots, found in 52 patients. Only two patients had three roots. The number of canals per root was symmetrical in 45 patients out of 57 (78.9%). Thirty-eight patients (84.4%) had two canals in the mesial roots and one canal in the distal roots. Four patients (8%) had two canals in both mesial and distal roots, and one patient (2.2%) had a single canal in both mesial and distal roots. Two patients (4.4%) had two canals in the mesial root and a single canal in the distobuccal and distolingual roots.

The root canal configuration was symmetrical in 24 of the 57 patients (42.1%). Most of these patients, 20 out of the 24, had Vertucci type IV in the mesial root, and the other four had Vertucci type II. Thirteen patients had Vertucci type I in the distal root, five patients had type III, two had type IV, one had type V, and another one had type II. Two patients had Vertucci type I in the distobuccal and the distolingual roots. More than half of the patients, 33 (57.9%), had asymmetrical root canal configuration in the right and left first molar.

Mandibular second molar

The number of MSMs that met the inclusion criteria was 255 teeth (23.4%) out of 1088. One hundred forty-seven teeth (57.6%) belonged to females, and 108 (42.4%) were males. The patients' age ranged from 12 years to 76 years, with an average of 34.4 years. The teeth were excluded mainly due to tooth loss (304 teeth), followed by restorations (234), the tooth was not fully scanned (167), and 81 teeth were root canal treated.

Root morphology

The most common number of the roots observed was two, found in 237 teeth (92.9%). One, three, and four roots were rarely observed, only in 13 (5.1%), 4 (1.6%), and one tooth (0.4%), respectively. Two of the four three-rooted teeth had extra root on the distolingual side, and the other two had the extra root extending from the mesial root [Figure 3].
Figure 3: Axial view of cone-beam computed tomography image showing example of three and four rooted mandibular second molar. (a) Showing the extra mesial root (radix paramolaris), (b) showing the extra distolingual root (radix entomolaris) and (c) showing the four roots

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Number of canals per root

The number of canals most commonly observed was two in the mesial roots of 192 teeth (75.3%) and one canal in the distal roots of 229 (89.8%) of the two-rooted teeth. Four canals were detected in 8 teeth (3.1%). The three-rooted teeth had a single canal in each root, except for one tooth, which had two canals in the mesial root. Four canals were detected in the four-rooted tooth (0.4%). One canal was detected in five (2%) single-rooted teeth. Only seven of the teeth (2.8%) had C-shaped canals [Figure 4].
Figure 4: Axial view of cone-beam computed tomography image showing C-shaped canal configuration of mandibular right second molar

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Root canal configuration

The root canal configuration most commonly observed in the two-rooted MSM's mesial root was type IV Vertucci, found in 137 teeth (57.8%), followed by type II Vertucci, in 55 teeth (23.2%) [Figure 5]. Other types were also detected in a lesser number, as shown in [Table 2]. Vertucci type I configuration predominated in the distal roots of 207 teeth (87.3%). Type I Vertucci was observed in all the roots of the three-rooted MSMs, except for one mesial root, which had type II, and one distal root had type III. In the four-rooted MSMs, type I Vertucci was observed in all the roots. Different canal configuration was observed in the single-rooted MSM [Table 2]. Two of them had complex anatomy [Figure 6].
Table 2: The classification of the mandibular second molar root canal configuration according to Vertucci classification (n=255)

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Figure 5: Coronal view of cone-beam computed tomography image showing mesial root of mandibular left second molar with class II Vertucci canal configuration (2-1)

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Figure 6: Coronal view of cone-beam computed tomography image showing mesial root of mandibular left second molar with “complex anatomy” (2-1-2-1-2-1)

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Symmetry between left and right mandibular first molar

Out of 88 patients, 82 (93.2%) had a symmetrical number of roots in both the mandibular right and left second molars. The symmetrical teeth had mainly two roots (80, 97.6%), and two patients had one root (2.4%). The number of the canals per root was symmetrical in 63 patients (71.6%). The symmetrical teeth were found mainly to have two canals in the mesial roots and one in the distal roots (52, 82.5%). Seven of them had one canal in the mesial and distal roots (11.1%). Two had two canals in the mesial and distal roots (3.1%). One had two canals (1.6%), and another one had a single canal (1.6%).

Forty-three of the patients (48.9%) were found to have a symmetrical root canal configuration in the mandibular left, compared to the mandibular right second molar. In the mesial roots, 31 out of 43 patients had type IV Vertucci, eight patients had type II, and two patients had type III. In the distal roots, 38 out of 43 patients had type I, two patients had type III, and one patient had type II. One patient had Vertucci type I, and another one had Vertucci type II in a single-rooted mandibular right and left second molar. Forty-five of the patients (51.1%) had asymmetrical root canal configuration in the mandibular right compared to the left second molar.


  Discussion Top


This study used CBCT to provide a detailed report on the root morphology and the root canal configuration of mandibular first and second molars in the Qatari population. The recent use of CBCT has made it possible to conduct a comprehensive 3D analysis of the root and canal system. This makes it a useful tool to study the anatomy of the root canal system that could not be detected using conventional radiographs or clinical techniques.

Prior knowledge of root and canal morphology of mandibular molars facilitates the accurate detection of all root canals during endodontic treatment. The failure to detect, debride or fill a canal leads to a poor outcome because of residual intracanal infection.[18] This might eventually lead to tooth loss. In the current study, 688 of the MFMs and 619 of the MSMs were not included because of tooth loss, restorations, and root canal treatment. This highlights the importance of prior knowledge of root and canal morphology to increase the success rate of root canal therapy.

The most common frequent number of roots of the mandibular molars in the Qatari population was two, with two canals in the mesial root and one canal in the distal root. These results agree with those evaluated by CBCT in Brazilian, Chilean, Turkish, and Chinese populations.[19],[20],[21],[22] The same results, using different methodologies, were also reported in Egyptian, Saudi, Kuwaiti, Sudanese, Jordanian and other populations, as reported in a systematic review and meta-analysis, which included 65 studies.[4]

The most common canal configuration in the mesial root of mandibular molars in the present study was type IV Vertucci, followed by type II. Similar findings were reported by different investigators.[6],[21],[23]

According to Tomaszewska et al., type I Vertucci was the most common root canal configuration of the distal root of mandibular molar teeth.[4] Similar findings were observed in the Qatari population. While Tomaszewska et al. and other studies reported that Vertucci type II was the second most common configuration of the distal roots.[4],[6],[19],[24],[25],[26],[27] Vertucci type III was the second most common root canal configuration in the Qatari population. Caputo et al. reported similar findings.[20] These differences in the findings may be related to the differences in the geographical region and ethnicity.

A third root is an expected anatomical characteristic of Mongoloid, Native American, Eskimo, and Chinese populations.[6] The association of ethnicity with the number of roots was investigated in the literature. It was found that the highest prevalence of three-rooted MFM was in Asia, 12.2%, compared to 3.2% in Africa and 3.2% in Europe.[4] The third root might be present in the lingual side, named radix entomolaris (RE), or in the buccal side named radix paramolaris (RP).[28] In the present study, RE was found on six MFMs (3.6%) and two MSMs (1.6%) while RP was found on one MFM and two MSMs [Figure 1] and [Figure 3]. Similar values were reported by Riyahi et al. in a sample of the Saudi population, 3.5% and 1.48%, respectively.[28] A slightly higher prevalence of three roots in MFM, which reach up to 6.0%, was reported in other studies on the Saudi population.[9] In the Kuwaiti population, Zaatar et al. reported that three-rooted MFM was found in 2.7%, compared to 4%, which was reported by Pattanshetti et al.[7],[12] Similar findings were reported in Jordanian, Iranian and Turkish populations: 4%, 3.5%, and 3.6%, respectively.[8],[19],[29] The highest prevalence of a third root in MFM was reported in the Korean population (24.5%), while in MSM of the same population, it was the lowest (0.7%).[30]

The frequency of single-rooted mandibular molars ranges from 0% to 45% and it is associated more with MSMs. A systematic review reported that the highest prevalence of single-rooted MSMs was associated with the Asian population. It might reach 45.4% in Chinees, Taiwanese, Indian, or Korean populations.[5] In the Iranian subpopulation, the prevalence of single-rooted MSMs was found to be 15.2% and none was found in MFMs.[29] No single-rooted MFM was recorded in this study, and the prevalence of a single root was low in the MSM, in only 5.1%. These results were slightly lower compared to the Jordanian population.[8] They reported that the single root prevalence was 1% in MFM and 7% in MSM.[8] Single-rooted mandibular molars in a Turkish population were reported to be low in both MFM (0.2%) and MSM (1.5%).[19],[31] These variations of the frequency of the single-rooted lower molars are most likely to be linked to genetic, racial, and ethnic backgrounds.

The prevalence of four-rooted mandibular molars is scarce in the literature, less than 1%. Two studies on the Turkish population reported the presence of four-rooted mandibular molars in their samples.[19],[31] One study found four-rooted mandibular molars in only 0.2% of MFM and 0.9% of MSM, while the other found that only 0.2% MSMs were four-rooted, and none in MFM.[19],[31] In the Chinese population, it was reported that 0.3% of MFM and 0.6% of MSM had four roots.[21] Similarly, in England, the presence of four-rooted mandibular molars was low (0.3%) in MSM.[32] Only eight cases of MSM with four roots have been reported in the literature. These cases were from Siri Lanka, Portugal, and the remaining six were from India.[33],[34] The prevalence of the four-rooted mandibular molars in the Qatari population was also rare; it was only found in one MSM (0.4%).

The presence of C-shaped canals in MFM ranged from 0% to 1.7%, while in MSM, it varied extensively among different regions.[10],[35] It could be as low as 0.4%, as reported in the Korean population,[30] and as high as (44%), as reported in the Asian population.[5],[32] Few C-shaped canals were found in the Qatari population sample in the present study; it was only associated with seven MSMs (2.8%), and none were found in MFMs. This might be because of the small sample size. In the Jordanian population, no C-shaped canals were observed in the MFMs, but a higher percentage was found in the MSMs (10.4%), compared to the present study.[8] The presence of the C-shaped canal configuration in a Saudi population was also higher in the MSMs (9.1%).[36]

The current study showed that the symmetry of the number of roots and canals between right and left mandibular molars was 78.9% in MFMs and 71.6% in MSMs. Similar results were reported by Felsypremila et al. on the Indian population, where the symmetry of MFMs was 78.6%, and the symmetry of MSMs was higher, at 82.1%.[37] Similar findings were reported in the Italian population[38] and Iranian subpopulation.[29] The results reported in Saudi population regarding the symmetry of the number of canals in MFMs was less compared to the present study and other studies (56.4%).[23]

The sample in this study is considered a good representative of the Qatari population. It was obtained from three leading dental hospitals, which provide treatment for patients from different regions of the country. However, in the current study, the high number of excluded teeth because of root canal treatment, extraction, or poor quality CBCT images, which left us with 195 MFMs and 255 MSMs, is considered a limitation. A larger sample size is required to study the association between the gender/age of the patients and the number of the roots/canals, and the canals configuration in mandibular molars. It will also provide us with more accurate data about the prevalence of rare root and canal variations.

In the literature, Vertucci's classification is the most common classification used to describe root canal morphology. The current study used the same classification too. However, not all the canal configurations found could be categorized using Vertucci's classification. Therefore, they were described as complex anatomy. More recently, a classification proposed by Ahmed et al. is getting more popular to categorize root and root canal configuration.[39] It is accurate, simple, and reliable. It can provide detailed information on the tooth number, the number of the roots, and root canal configuration type. Using this classification for future studies on the root and canal morphology is recommended.


  Conclusions Top


To achieve successful root canal therapy, the dentist should have a thorough knowledge of root canal morphology, its variation, and complexity. The number of roots could vary from one to four roots, and there is a possibility of the presence of C-shaped canals or Radix Entomolaris. Proper diagnosis using preoperative angled periapical radiographs facilitates the endodontic procedures and will help to avoid missed canals. The results of the present study have shown that in this sample of the Qatari population;

  1. The most commonly observed number of roots in the mandibular molar was two roots
  2. The mesial root was frequently presented with two canals
  3. Types IV and II were the most common configurations
  4. The most common root canal configuration in the distal root was type I, followed by type III
  5. A third root (mesial or distolingual) was found in 3.6% of MFM and 1.6% of MSM
  6. C-shaped canal configuration was detected in only 2.8% of MSM.


Financial support and sponsorship

This work was supported by Hamad Research Center (grant number 17228,2017); Hamad Medical Corporation, Doha-Qatar.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

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