Original Article

Prevalence of C-Shaped Canals in Anterior and Posterior Teeth of Iranian Population Using Cone Beam Computed Tomography

Citation: Ostevar Rad F, Mousavi E, Musapoor N, Maleki D, Khatibi N. Prevalence of c-shaped canals in anterior and posterior teeth of Iranian population using cone beam computed tomography. Avicenna J Dent Res. 2020;12(2):58-62. doi: 10.34172/ajdr.2020.12.

Background

Highlights

• C-shaped canal system has the predilection for mandibular second molars.

• There was no correlation between gender and the occurrence of C-shaped canals.

• Besides, this study showed no correlation between age and C-shaped root canal configuration.

• The high incidence of the C-shaped canal in the Iranian population requires clinical awareness.

Lack of information about root anatomy and canal morphology is the second prevalent reason for failed endodontic therapy (1). Therefore, the preoperative recognition of canal morphology and root anatomy leads to more effective cleaning, shaping, and obturation procedures, thereby improving the long-term prognosis of the treatment (1-4).

The root canal system reveals different morphological variations such as C-shaped canal which is reported to cause clinical challenges and to complicate endodontic treatment (5). C-shaped canals were primarily pictured by Keith and Knowles in 1911 and were later defined by Cooke and Cox in 1979 (4,6). This anatomical variation is named C-shaped because of the presence of fin or web connecting the individual canals, leading to a configuration that resembles the letter “C” in a transverse section (4-6). The failure of Hertwig’s epithelial root sheath to fuse on buccal or lingual root surface is claimed to be the main cause of this anatomic variation (4,7,8).

Different techniques were introduced for evaluating the canal morphology and root anatomy including decalcification and cleaning technique, sectioning technique, radio-opaque contrast, modeling method, and imaging (9). Radiography is an easy, practical, and non-invasive technique to study the root anatomy and canal morphology especially in non-extracted teeth (10).

Panoramic radiographs and intraoral radiographs are two-dimensional images (11). Due to the absence of the third dimension in these images, the diagnosis of dentin between the roots in C-shaped root systems is very difficult (6,11). Additionally, it is hard and unreliable to clinically predict whether the C-shaped morphology continues throughout the root canal. CBCT (cone beam computed tomography) is an accurate 3D image with high resolution which provides better vision and understanding of anatomy and morphology of C-shaped canals (1,4,6,11).

Since the C-shaped canal is considered to have a genetic predisposition and this anatomic configuration can influence the successful endodontic treatment, in this study, the occurrence of the C-shaped roots in permanent anterior and posterior teeth of the Iranian population was determined using CBCT scans to provide better knowledge in this field.

Materials and Methods

In this descriptive cross-sectional study, 1408 teeth resulting from 250 CBCT images of patients were assessed. This study was designed based on STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines.

Anterior and posterior teeth with fully developed apices were included in the current study. The teeth with caries, restoration, or previous root canal therapy were excluded.

Cranex 3D Mid (Tuusula, Finland) was used to prepare the CBCT images using the following operating parameters: 90 kV and 10 mA, a field of view (FOV) of 6.8 × 6.8 cm, and a voxel size of 200 µm x 200 µm x 200 µm. The CBCT imaging was taken as a part of the patients’ diagnostic objectives irrelevant to the current study.

Two of the researchers evaluated the CBCT images. The two researchers were trained on the observation of tomography slices and exclusion of the required data from the images. To measure the inter-observer agreement, the Cohen’s unweighted kappa coefficient was used. Estimation of the inter-observer agreement between the two researchers showed that both researchers agreed on all 40 cases. The 40 CBCT images used for assessing the inter-observer agreement were not included in the study. If any controversy occurred during the study, the third researcher assisted in making the decision.

Each tooth was examined in axial sections with the thickness of 0.5 mm, and 5 different levels were identified as coronal (2 mm below the canal orifice), medium (middle distance between canal orifice and radiographic apex), apical (2 mm coronal of radiographic apex), 1/3 (middle distance between medium and coronal) and 2/3 (middle distance between medium and apical (12).

The canal shapes were categorized based on the modified Melton’s method presented by Fan et al as follows (13):

• Category 1 (CI): A continuous C-shaped canal with no division or separation;

• Category 2 (CII): The canal orifice resembles a semicolon, where a C-shaped canal is present buccally or lingually, separated from another distinct canal by a dentine wall;

• Category 3 (CIII): Two or three separate and discrete canals;

• Category 4 (CIV): A single oval or round canal;

• Category 5 (CV): No canal orifice was found.

• SPSS version 24.0 was used to analyze the data. The chi-square test was utilized to compare the frequencies. The significance level was adjusted to 5%.

Results

Out of 250 CBCT images, the data of 234 images were analyzed. Sixteen CBCT images were excluded from the study according to exclusion criteria. The mean age of the patients was 35.98 years old. The youngest patient was 11 years old and the oldest one was 76 years old. Additionally, 41.9% (98) of patients were male and 58.1% (136) were female.

Of a total of 1408 canals which were evaluated, 7.81% (110) were confirmed to be C-shaped and 92.19% (1298) were not C-shaped.

Of1408 teeth, 36.3% (511), 26.3% (370), and 37.4% (527) were anterior teeth, premolars, and molars, respectively (Table 1). The occurrence of the C-shaped canal was considerably higher in molars compared to premolars and anterior teeth (P < 0.0001).

Of 1408 teeth, 47.3% (667) were recorded as mandibular teeth and 52.7% (741) as maxillary teeth. In the current study, C-shaped canals were found in 10.04% (67) of mandibular teeth and in 5.81% (43) of maxillary teeth. The occurrence of the C-shaped canal was significantly higher in mandibular teeth compared to maxillary teeth (P < 0.001).

Of the 1408 evaluated teeth, the most common C-shaped canal category was C1 (57.27%) followed by C2 (42.73%). In the current study, C3, C4, and C5 were not observed.

There was no statistical difference in the prevalence of the C-shaped canal between males and females (P = 0.585) (Table 2). Additionally, the correlation between the C-shaped canal and age was not significant (P = 0.562).

Discussion

There are numerous studies on the anatomic configuration of the root canal system of mandibular second molars with diverse results. It is thought that one of the determinants of C-shaped canal configuration is the genetic factor, as most of the population having C-shaped canal is found in the Asian population (1,4,6). In East Asia, the maximum occurrence was reported in South Korea (44.5%) and China (39%) (14,15). In the Middle East, the highest occurrence was reported in Lebanon (19.14%) and the lowest was reported in Iran (7.2%) (16,17). In a Turkish population, the reported occurrence was 8.9% (16). In the Indian population, the occurrence of C-shaped canal configuration ranged from 7.4% to 13.12% (2,18). The occurrence in a Saudi Arabian population varied from 9.1 to 14.4% (4,19).

In different studies, the occurrence of C-shaped canals in mandibular second molars ranged from 2.7 to 44.6% (4). The frequency of C-shaped root canal configuration in mandibular second molars in the studies conducted by Janani et al (10) and Madani et al (20) was 21.4% and 17.6%, respectively. The occurrence was also different in the studies conducted by Weine et al (21) (2.7%), Cooke and Cox (22) (8%), Jin et al (14) (44.6%), and Seo and Park (23) (32.7%). In the current study, the C-shaped canal was found in 7.81% of the samples. Despite the difference in occurrence rate which results from having different ethnic groups, all the above-mentioned studies claim that the C-shaped canal system has the predilection for mandibular second molars (4,10,14,20-23). This finding is also consistent with reports of Mirzaie and Zaban (24), Nielsen and Shahmohammadi (25), Victorino et al (26), Sandhya et al (27), and Rwenyonyi et al (28).

The current study reported no C-shape canal in premolars, which is consistent with the findings of Hajihassan et al (1) and Vega-Lizama et al (5). On the contrary, Zare Jahromi et al (29) observed C-shaped canal in 0.44% of premolars. Additionally, other studies reported the occurrence of the C-shaped canal configuration in premolars (30-33). This controversy may be due to different canal identification techniques or different races.

Only a few articles studied the occurrence of C-shaped canal in maxillary teeth. In the current study, C-shaped canal configuration was only reported in 5.8% of maxillary teeth, and in a study conducted by Jo et al, it was reported in 1.8% of maxillary teeth (34). De Moor et al (35) reported the occurrence of C-shaped canals to be 0.091% in maxillary first molars and Yang et al (36) estimated the occurrence to be 4.9% in maxillary second molars. Ethnic background, sample size, and methodology may be the cause of these differences.

The findings of this study indicated that the occurrence of C1 was higher than C2. Moreover, Duman et al (6), Janani et al (10), Zheng et al (15), Helvacioglu-Yigit and Sinanoglu (16), and Kim et al (37) found similar results. However, Kim et al (11), Pawar et al (2), and Seo and Park (23) found that the most common C-shaped canal type was C2. On the contrary, Alfawaz et al (4) and Bahammam (19) found that the most common C-shaped canal configuration was C3. The variations in C-shaped canal configurations among the researches are attributed to various sample sizes and different studied teeth.

Many studies did not assess the effect of gender on the occurrence of C-shaped canals (17,23,38). However, Martins (12), Zuben et al (39), Duman et al (6), Kim et al (37), and Alfawaz et al (4) studied this relationship and indicated that there is a noticeably higher occurrence of C-shaped canals in females compared to males. On the contrary, the studies conducted by Helvacioglu-Yigit and Sinanoglu (16), Janani et al (10), Zheng et al (15), Jin et al (14), Ladeira et al (40), and the current study found no correlation between gender and the occurrence of C-shaped canals.

Besides, this study showed no correlation between age and C-shaped root canal configuration. These data are in agreement with the results of the studies conducted by Janani et al (10), Kim et al (11), Zheng et al (15), Helvacioglu-Yigit and Sinanoglu (16), Kim et al (37), and Ladeira et al (40).

The small sample size is the limitation of the current study. Further studies should be carried out to study the prevalence of C-shaped canals in different countries and races.

CBCT is a useful instrument to evaluate C-shaped root canal morphology. The high incidence of the C-shaped canal in the Iranian population requires clinical awareness.

Conflict of Interest Disclosures

There were no conflicts of interest.

Ethical Statement

There was no ethical statement.

Authors’ Contribution

FOR, EM, NM, DM, NK:, Conceptualization,Data curation, Methodology, Project administration, Resources, Software

FOR, EM: Funding acquisition, Supervision, Validation,Visualization

FOR, EM, NK: Formal analysis, Investigation:

Writing - original draft: DM

Writing - review & editing: EM,DM

Funding

None.

References

1. Hajihassani N, Roohi N, Madadi K, Bakhshi M, Tofangchiha M. Evaluation of root canal morphology of mandibular first and second premolars using cone beam computed tomography in a defined group of dental patients in Iran. Scientifica (Cairo) 2017; 2017:1504341. doi: 10.1155/2017/1504341 [Crossref] [ Google Scholar]
2. Pawar AM, Pawar M, Kfir A, Singh S, Salve P, Thakur B. Root canal morphology and variations in mandibular second molar teeth of an Indian population: an in vivo cone-beam computed tomography analysis. Clin Oral Investig 2017; 21(9):2801-9. doi: 10.1007/s00784-017-2082-6 [Crossref] [ Google Scholar]
3. Abdulmajeed KR, Mustafa NS, Kashmoola MA, Jabbar OA, Ab Razak LS, Noor SN. The diagnosis and determination of C-shaped canal in lower second molar. J Int Dent Med Res 2018; 11(3):810-8. [ Google Scholar]
4. Alfawaz H, Alqedairi A, Alkhayyal AK, Almobarak AA, Alhusain MF, Martins JNR. Prevalence of C-shaped canal system in mandibular first and second molars in a Saudi population assessed via cone beam computed tomography: a retrospective study. Clin Oral Investig 2019; 23(1):107-12. doi: 10.1007/s00784-018-2415-0 [Crossref] [ Google Scholar]
5. Vega-Lizama EM, Tiesler V, Chi-Keb JR, Ramírez-Salomón M, Hernández-Mejía A, Cucina A. Root canal morphology of the mandibular first premolars in a Yucatecan population using cone beam computed tomography: an in vitro study. Int J Morphol 2018; 36(4):1216-21. doi: 10.4067/s0717-95022018000401216 [Crossref] [ Google Scholar]
6. Duman SB, Duman S, Bayrakdar IS, Yasa Y, Gumussoy I. Cone-beam computed tomography evaluation of C-shape canals and longitudinal grooves of mandibular first and second molar teeth. Ann Med Res 2019; 26(12):2853-8. doi: 10.5455/annalsmedres.2019.09.581 [Crossref] [ Google Scholar]
7. Kantilieraki E, Delantoni A, Angelopoulos C, Beltes P. Evaluation of root and root canal morphology of mandibular first and second molars in a Greek population: a CBCT study. Eur Endod J 2019; 4(2):62-8. doi: 10.14744/eej.2019.19480 [Crossref] [ Google Scholar]
8. Nejaim Y, Gomes AF, Rosado LPL, Freitas DQ, Martins JNR, da Silva E. C-shaped canals in mandibular molars of a Brazilian subpopulation: prevalence and root canal configuration using cone-beam computed tomography. Clin Oral Investig 2020; 24(9):3299-305. doi: 10.1007/s00784-020-03207-6 [Crossref] [ Google Scholar]
9. Datta P, Zahir S, Kundu GK, Dutta K. Different methods of studying root canal morphology of human tooth: a review. Bangladesh J Dent Res Educ 2015; 5(2):59-63. doi: 10.3329/bjdre.v5i2.24718 [Crossref] [ Google Scholar]
10. Janani M, Rahimi S, Jafari F, Johari M, Nikniaz S, Ghasemi N. Anatomic features of C-shaped mandibular second molars in a selected Iranian population using CBCT. Iran Endod J 2018; 13(1):120-5. doi: 10.22037/iej.v13i1.17286 [Crossref] [ Google Scholar]
11. Kim HS, Jung D, Lee H, Han YS, Oh S, Sim HY. C-shaped root canals of mandibular second molars in a Korean population: a CBCT analysis. Restor Dent Endod 2018; 43(4):e42. doi: 10.5395/rde.2018.43.e42 [Crossref] [ Google Scholar]
12. Martins JNR, Mata A, Marques D, Caramês J. Prevalence of C-shaped mandibular molars in the Portuguese population evaluated by cone-beam computed tomography. Eur J Dent 2016; 10(4):529-35. doi: 10.4103/1305-7456.195175 [Crossref] [ Google Scholar]
13. Fan B, Cheung GS, Fan M, Gutmann JL, Fan W. C-shaped canal system in mandibular second molars: Part II--Radiographic features. J Endod 2004; 30(12):904-8. doi: 10.1097/01.don.0000136206.73115.93 [Crossref] [ Google Scholar]
14. Jin GC, Lee SJ, Roh BD. Anatomical study of C-shaped canals in mandibular second molars by analysis of computed tomography. J Endod 2006; 32(1):10-3. doi: 10.1016/j.joen.2005.10.007 [Crossref] [ Google Scholar]
15. Zheng Q, Zhang L, Zhou X, Wang Q, Wang Y, Tang L. C-shaped root canal system in mandibular second molars in a Chinese population evaluated by cone-beam computed tomography. Int Endod J 2011; 44(9):857-62. doi: 10.1111/j.1365-2591.2011.01896.x [Crossref] [ Google Scholar]
16. Helvacioglu-Yigit D, Sinanoglu A. Use of cone-beam computed tomography to evaluate C-shaped root canal systems in mandibular second molars in a Turkish subpopulation: a retrospective study. Int Endod J 2013; 46(11):1032-8. doi: 10.1111/iej.12094 [Crossref] [ Google Scholar]
17. Rahimi S, Shahi S, Lotfi M, Zand V, Abdolrahimi M, Es’haghi R. Root canal configuration and the prevalence of C-shaped canals in mandibular second molars in an Iranian population. J Oral Sci 2008; 50(1):9-13. doi: 10.2334/josnusd.50.9 [Crossref] [ Google Scholar]
18. Sherwood IA, Gutmann JL, Kumar S, Evangelin J, Nivedha V, Sadashivam V. CBCT analysis of the anatomy of C-shaped root canals in mandibular second molars from a southern Indian population in Tamil Nadu. ENDO 2019; 13(1):61-70. [ Google Scholar]
19. Bahammam LA. Prevalence of C-Shaped root canals in mandibular second molars in a sample population of Saudi Arabia. Pak Oral Dent J 2018; 38(3):377-80. [ Google Scholar]
20. Madani ZS, Mehraban N, Moudi E, Bijani A. Root and canal morphology of mandibular molars in a selected Iranian population using cone-beam computed tomography. Iran Endod J 2017; 12(2):143-8. doi: 10.22037/iej.2017.29 [Crossref] [ Google Scholar]
21. Weine FS, Pasiewicz RA, Rice RT. Canal configuration of the mandibular second molar using a clinically oriented in vitro method. J Endod 1988; 14(5):207-13. doi: 10.1016/s0099-2399(88)80171-7 [Crossref] [ Google Scholar]
22. Cooke HG 3rd, Cox FL. C-shaped canal configurations in mandibular molars. J Am Dent Assoc 1979; 99(5):836-9. doi: 10.14219/jada.archive.1979.0402 [Crossref] [ Google Scholar]
23. Seo MS, Park DS. C-shaped root canals of mandibular second molars in a Korean population: clinical observation and in vitro analysis. Int Endod J 2004; 37(2):139-44. doi: 10.1111/j.0143-2885.2004.00772.x [Crossref] [ Google Scholar]
24. Mirzaie M, Tork Zaban P, Mohammadi V. Cone-beam computed tomography study of root canals in a Hamadani population in Iran. Avicenna J Dent Res 2012; 4(2):25-31. [ Google Scholar]
25. Nielsen CJ, Shahmohammadi K. The effect of mesio-distal chamber dimension on access preparation in mandibular incisors. J Endod 2005; 31(2):88-90. doi: 10.1097/01.don.0000137635.54668.9d [Crossref] [ Google Scholar]
26. Victorino FR, Bernardes RA, Baldi JV, Moraes IG, Bernardinelli N, Garcia RB. Bilateral mandibular canines with two roots and two separate canals: case report. Braz Dent J 2009; 20(1):84-6. doi: 10.1590/s0103-64402009000100015 [Crossref] [ Google Scholar]
27. Sandhya R, Velmurugan N, Kandaswamy D. Assessment of root canal morphology of mandibular first premolars in the Indian population using spiral computed tomography: an in vitro study. Indian J Dent Res 2010; 21(2):169-73. doi: 10.4103/0970-9290.66626 [Crossref] [ Google Scholar]
28. Rwenyonyi CM, Kutesa AM, Muwazi LM, Buwembo W. Root and canal morphology of maxillary first and second permanent molar teeth in a Ugandan population. Int Endod J 2007; 40(9):679-83. doi: 10.1111/j.1365-2591.2007.01265.x [Crossref] [ Google Scholar]
29. Zare Jahromi M, Mehdizade M, Shirazizade Z, Poursaeid E. Evaluation of mandibular premolars root canal morphology by cone beam computed tomography. Caspian J Dent Res 2018; 7(1):58-63. doi: 10.22088/cjdr.7.1.58.[Persian] [Crossref] [ Google Scholar]
30. Yu X, Guo B, Li KZ, Zhang R, Tian YY, Wang H. Cone-beam computed tomography study of root and canal morphology of mandibular premolars in a western Chinese population. BMC Med Imaging 2012; 12:18. doi: 10.1186/1471-2342-12-18 [Crossref] [ Google Scholar]
31. Liao Q, Han JL, Xu X. [Analysis of canal morphology of mandibular first premolar]. Shanghai Kou Qiang Yi Xue 2011; 20(5):517-21. [ Google Scholar]
32. Shetty A, Hegde MN, Tahiliani D, Shetty H, Bhat GT, Shetty S. A three-dimensional study of variations in root canal morphology using cone-beam computed tomography of mandibular premolars in a South Indian population. J Clin Diagn Res 2014; 8(8):ZC22-4. doi: 10.7860/jcdr/2014/8674.4707 [Crossref] [ Google Scholar]
33. Khademi A, Mehdizadeh M, Sanei M, Sadeqnejad H, Khazaei S. Comparative evaluation of root canal morphology of mandibular premolars using clearing and cone beam computed tomography. Dent Res J (Isfahan) 2017; 14(5):321-5. doi: 10.4103/1735-3327.215964 [Crossref] [ Google Scholar]
34. Jo HH, Min JB, Hwang HK. Analysis of C-shaped root canal configuration in maxillary molars in a Korean population using cone-beam computed tomography. Restor Dent Endod 2016; 41(1):55-62. doi: 10.5395/rde.2016.41.1.55 [Crossref] [ Google Scholar]
35. De Moor RJ. C-shaped root canal configuration in maxillary first molars. Int Endod J 2002; 35(2):200-8. doi: 10.1046/j.1365-2591.2002.00461.x [Crossref] [ Google Scholar]
36. Yang ZP, Yang SF, Lee G. The root and root canal anatomy of maxillary molars in a Chinese population. Endod Dent Traumatol 1988; 4(5):215-8. doi: 10.1111/j.1600-9657.1988.tb00324.x [Crossref] [ Google Scholar]
37. Kim SY, Kim BS, Kim Y. Mandibular second molar root canal morphology and variants in a Korean subpopulation. Int Endod J 2016; 49(2):136-44. doi: 10.1111/iej.12437 [Crossref] [ Google Scholar]
38. Seo DG, Gu Y, Yi YA, Lee SJ, Jeong JS, Lee Y. A biometric study of C-shaped root canal systems in mandibular second molars using cone-beam computed tomography. Int Endod J 2012; 45(9):807-14. doi: 10.1111/j.1365-2591.2012.02037.x [Crossref] [ Google Scholar]
39. von Zuben M, Martins JNR, Berti L, Cassim I, Flynn D, Gonzalez JA. Worldwide prevalence of mandibular second molar C-shaped morphologies evaluated by cone-beam computed tomography. J Endod 2017; 43(9):1442-7. doi: 10.1016/j.joen.2017.04.016 [Crossref] [ Google Scholar]
40. Ladeira DB, Cruz AD, Freitas DQ, Almeida SM. Prevalence of C-shaped root canal in a Brazilian subpopulation: a cone-beam computed tomography analysis. Braz Oral Res 2014; 28:39-45. doi: 10.1590/s1806-83242013005000027 [Crossref] [ Google Scholar]