Keywords

C-Shape Canal; Canal Variation; Mandibular Second Molar.

Introduction

In endodontics, root canal treatment of a tooth with variable anatomy is a rule rather than an exception [1, 2]. One such anatomic variation is the C-shaped root canal system, although most commonly seen in mandibular second molars have also been observed in mandibular premolars, maxillary first molars, and maxillary and mandibular third molars [3, 5]. Historically, various authors have done numerous investigations on the prevalence and ethnic variation of such canal systems [6, 7]. Initially, named as “gutter-” shaped canals by Nakayama and horseshoe reduction forms, the term C shaped was originally described by Cooke and Cox in endodontic literature in the year 1979 [8-10]. Manning postulated that the reason for the occurrence of C-shape canal was the failure of hertwig's epithelial root sheath to fuse. It is usually characterized by presence of a fin or wels connecting the individual mesial and distal canals having C-shape axial section [11-14]. Roots containing C-shape canals often have a square or conical shape configuration [15, 16].

The main goal of endodontic therapy is to prevent or heal apical periodontitis, this means cleaning, shaping, disinfection and three-dimensional obturation of the root canal system [17, 18]. Many early and recent studies showed that a root with single tapering canal is an exception rather than the rule [19-22].

The complexity of the root canal anatomy presents clinical challenges during the treatment, so knowledge of pulpal anatomy and its variations are essential for long term success of endodontic treatments [23-26].

C-shape canals are among these variations that were first described by cooke and cox [9, 27]. The name comes from C-shape cross sectional morphology of the root and root canal. In such cases, several discrete orifices are not seen, instead, the pulp chamber has a single ribbon shaped orifice with 189 degree arc- In mandibular molars, the arc originates from the mesiolingual line angle, continues towards buccal and terminates at the distal aspect of pulp chamber [28].

The variation of C-shape root canal system appears to be genetically determined, and it has some relationship with ethnic origin6. It could be found throughout the world but the incidence is much higher in Asian population [29-31]. Incidence studies have been reported in Chinese, Indian, and Iranian population, with the highest frequency being reported in the Chinese population (29.7%) in case of mandibular premolars. The C-shaped canal anatomy has also been reported in maxillary first molars (0.12%), maxillary third molars (4.7%), mandibular third molars (3.5%- 4%), and mandibular second premolars (1%) [32].

The objective of this study is to assess the prevalence of C-shape canal variation in mandibular second molar in the south indian population.

Materials And Methods

The study was undertaken after ethical approval was obtained from the institutional review boards. Data was retrospectively collected from the case records patients who visited the Department of Conservative Dentistry and Endodontics at Saveetha Dental College. Patients who had undergone root canal treatment in mandibular second molar were included in the study. Patients who were undergoing root canal treatment in teeth other than 37 and 47 were excluded from the study. 5000 plus case sheets of patients who underwent root canal treatment were reviewed and from that, 475 patients who fulfilled the criteria were included in the study. Simple random sampling was done to minimise the sampling bias. Data verification was done based on the age, gender, teeth number, canal variation. Data was entered in the excel sheet in a methodical manner and was imported to SPSS. Incomplete or uncensored data was excluded from the study. IBM SPSS 20.0 Software was used for data analysis. Independent variables include – age, gender and dependent variables include canal variation and teeth number. Descriptive and inferential statistics was used. Inferential test includes the chi-square test.

Results And Discussion

Out of 475 patients who underwent root canal treatment in mandibular second molar, 5.89% were reported to have C-shape canal [figure-1] with maximum prevalence in the age group 14-34 years and slightly more in females than males. Coming to the age group, the maximum number of patients with C-shape canal is 14-34years (2.95%; n=14) followed by 35-54 years(2.74%; n=13) and least in 55-74years(0.21%; n=1).[figure-2]. Figure 3 shows the gender distribution of C-shape canal. Out of 475 patients, 55.5% were males and 44.5% were females where C-shape canal was prevalent in females(3.58%; n=17) than in males(2.32%%; n=11). Hence, when comparing both the genders, it was observed that females were slightly more prevalent for C-shape canal variation than males. While observing distribution of C-shape canal in left and right lower second molar, it was seen that C-shape canal variation was prevalent in 47 (left side)(3.16%; n=15) than in 37(right side)(2.74%%; n=13).

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Figure 1:

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Figure 1. Bar graph represents number of patients who underwent topical application of fluoride. X-axis represents fluoride application and Y-axis represents the total number of patients. Among 700 patients, 94 patients(13.45%) had undergone fluoride application.

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Figure 2:

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Figure 2. bar chart depicts distribution of canal anatomy in mandibular second molar according to age group. X-axis represents the age group and Y-axis represents the number of patients with canal anatomy. It shows that C-shape canal (green) is most prevalent in 14-34years followed by 35-54 years and least in 55-74years. Using chi-square test p value = 0.239(>0.05) is statistically non significant.

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Figure 3:

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Figure 3. Bar chart depicts the association between gender and canal anatomy in mandibular second molar. X-axis represents gender and Y-axis represents canal anatomy. Blue bar represents normal canal anatomy and green bar represents C-shape canal. Graph 3 shows that the C-shape canal was prevalent in females than in males. Using the chi-square test, p value= 0.074(>0.05) is statistically non significant.

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Figure 4:

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Figure 4. Bar chart depicts the association between teeth number and canal anatomy in mandibular second molar. X-axis represents teeth number i.e right lower second molar(37) and left lower second molar(47); and Y-axis represents number of patients with canal anatomy. Blue bar represents normal canal anatomy and green bar represents C-shape canal. Graph 4 shows that C-shape canal(green) was prevalent in 47 (left side) than in 37(right side) Using the chi-square test, p value= 0.096>0.05 is statistically non-significant.

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The data for this retrospective study was based on south indian residents in seeking treatment at Saveetha Dental College. Currently there are no existing studies investigating the prevalence of C-shape canal anatomy in mandibular second molar in South India. Since all the data available was included without a sorting process, no bias was accepted in selection of patients. The current study aims to shed light on the current scenario of prevalence of root canal therapy in C-shape canal so that different treatment approaches can be introduced. The severity of C-shape canal can be understood from the study.

A high incidence of C-shaped roots and root canal system in mandibular second molars has been reported in several studies conducted on japanese [33], chinese [34, 35], lebanese [36], korean [31], thai [37] populations all revealing higher prevalence of C-shape canal configuration among asians. The findings of this study differ from study conducted in Portugese population where the higher prevalence of C-shaped anatomy was found among 45- 54 years group with 11.1% [38] whereas the maximum prevalence of C-shape canal was seen in 14-34 years in the present study. However, the prevalence C-shape canal in mandibular second molar very according to the region of the globe.

No statistical difference was seen in the distribution of C-shape canal between gender, and between molars on the left and right side of the mandible. These results are also in agreement with a similar work done in Chinese population [39].

A study done by Wadhwani.S [40] et.al shows that prevalence of C-shape canal in mandibular second molar is 9.7% in North Indian population whereas in the present study, the prevalence of C-shape canal in mandibular second molar is 5.8% in South indian population. This statistical difference can be due to limited sample size.

This study has some other limitations too that may have affected the results. For example, the data collection period could have been longer, different populations could have been taken for comparison.

Despite the high prevalence of C-shape canal, not all dentists are confident in approaching this variation. The current study shows that despite its drawbacks C-shape canal variation is prevalent in mandibular second molar in patients in Chennai. This suggests the need to spread awareness among dentists in India to obtain knowledge on C-shape canal and use different treatment modalities. Extensive research can be done further by observing the prevalence of different levels of C-shape canal in different populations.

Conclusion

Within the limitations of this study, it was found that 94.11% of the population has normal canal anatomy and the prevalence of C-shape canal was only 5.8% in the mandibular second molar. C-shape canal was more prevalent in the age group 14-34 years when compared to other age groups and slightly more in females than males (p>0.05) in the south indian population. Considering the drawbacks of this study, it can be concluded that there exists a need for more extensive research to be done in this area to spread awareness among dentists and develop their knowledge on this canal variation and help them understand it’s severity.

Acknowledgement

This research was supported by Saveetha Dental College and Hospital. We thank the department of Conservative Dentistry and Endodontics, Saveetha dental college for providing insight and expertise that greatly assisted this research.

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