The occurrence of C-shaped root canal in Malaysian population

The occurrence of C-shaped root canal in Malaysian population Nie YK, Bakar WZW, Alam MK Abstract Background: The recognition of unusual canal’s configurations and variations are essential for successful endodontic diagnosis and treatment. This study was aimed to investigate the occurrence of Cshaped root canal in Malaysian population. Design: This is an in vitro study whereby 241 extracted human first and second molars with intact root were collected from several dental clinics in Malaysia. Materials and Methods: The roots were sectioned at three levels: subpulpal level, 3mm from apical tip and middle level between the first and last level. The appearance of the root canal sections were assessed using stereomicroscope (Leica, Germany) and pictures were taken. Data were analyzed statistically using Fisher’s Exact and Binomial test with p<0.05 indicates statistically significant difference. Results: The occurrence of Cshaped canal among molars collected is 3.73%. Hundred percent of the molars with Cshaped root canal configuration are mandibular molars and 77.8% are belonged to Chinese racial. Conclusion: The findings show that Cshaped root canals do occur among Malaysian people especially Chinese racial. Besides, all the teeth that possess Cshaped root canal configuration are lower molars.


Introduction
The study of root anatomy of teeth has an endodontic as well as anthropological significance.A successful endodontic treatment very much depends on endodontist's ability to recognize unusual root canal anatomy, successful intra-radicular reproduction, obturation and so on 1 .Most of teeth have shown accessory canals, multiple foramina, fins and deltas.In 1984, Vertucci also reported that the clinician must treat the tooth by assuming there is presence of accessory root canals unless proven otherwise 2 .A great deal of variations can present especially the canal configuration of mandibular second molar.Mandibular second molars usually have two roots and three root canals but variations in the number of roots as well as canal morphology are not uncommon.In 1979, Cooke and Cox first described the term C-shaped root canal 3 .They reported three cases where the root canals were like the English capital letter 'C', in which canals were connected by a continuous slit.C-shaped canals are commonly found in permanent mandibu-lar second molars but they can also be found in maxillary first molars, maxillary second molars, and mandibular first and second premolars, third molars and mandibular first molars [4][5][6][7] .The mandibular second molars with C-shaped root canals vary in their configurations and many methods have been used to classify such canals 2 .
C-shaped root canal was classified into 3 categories by Melton (1991) which were: Type I that is continuous C-shaped canal; Type II that is emicolon-shaped canal, orifice in which dentine separates a main C-shaped canal from one mesial distinct canal, and Type III which is 2 or more separate canals.
The shape and the number of roots are determined by Hertwig's epithelial sheath, which bends in a horizontal plane below the amelocemental junction and fuses in the centre leaving openings for roots 9 .
Fused roots may form either by coalescence owing to cementum deposition with time, or as a result of failure of Hertwig's epithelial sheath to develop or fuse in the furcation area 10 .A C-shaped canal appears when fusion of either the buccal or lingual aspect of the mesial and distal roots occurs.This fusion remains irregular and the two roots stay connected by an interradicular ribbon 11 .The pulp chamber has a single ribbon-shaped orifice with a 180º arc from the distal to mesial canal 12 .The floor of the pulp chamber is deep and has an unusual anatomical appearance 11 .Two or three canals may be found in the C-shaped groove, or the C-shape may be continuous throughout the length of the root.
This study was undertaken to determine the frequency of C-shaped root canals in Malaysian population as there is no study has been reported.It is important to be familiar with variations in tooth anatomy and characteristic features in various racial groups since such knowledge can aid location and negotiation of canals, as well as their subsequent management.
Result of this study could give an overview of how regular the occurrence of C-shaped canal in Malaysia, and therefore dentist can take early strategies and improve the technique to maximize the rate of success.

Materials and Methods
A total numbers of 241 extracted molars which follow the criteria were collected from several dental clinics of several states in Malaysia in this in vitro study.The inclusion criteria was first and second maxillary and mandibular extracted human molars with an intact root, and the exclusion criteria was teeth with fractured or broken root.Sample size was calculated with standard deviation of 11.87 following previous similar study by Jafarzadeh and  Wu (2007) with conventional Z value of 1.96 for 95% confidence interval 13 .
Teeth collected were cleaned using scalers and kept in 0.1% Thymol solution 14 .Roots for each tooth were sectioned at three levels: subpulpal level, 3mm from apical tip and middle level between the first and last level and pictures were taken using stereomicroscope (Leica, Germany).The presence of C-shaped canal was determined by two independent examiners.Data were collected and was analyzed for report writing using SPSS

Results
In this study, 241 extracted molars were sectioned and assessed.As shown in Table 2, most of the C-shaped canal were found in Chinese racial with 7 cases (77.8%) out of total 9 cases, followed by Malay and others racial with 11.1% respectively.Table 3 shows that C-shaped canal is statistically significant to be more commonly found in the Chinese racial than the non-Chinese racial.All the three types of C-shaped canal were observed (Figure 1, 2 and 3) and frequency was shown in Table 5. Type III has the highest frequency which is 4 cases (44.4%), followed by Type II (33.3%) and lastly Type I (22.2%).

Discussion
The report of teeth with C-shaped canal has drawn attention of dental practitioner especially endodontist due to the lower success rate of root canal therapy.Clearly, the root canal anatomy cannot always be predicted, and this can be the source of failure.
A solid understanding of the tooth anatomy including the number and course of various root canals represents the basic for successful endodontics therapy.
In the present study, the total occurrence of Cshaped canal among the 241 extracted human molars is 9 cases or 3.73%.The low percentage of occurrence can be explained by inclusion of all the molars, which is both maxillary and mandibulars in this study to prevent bias, although Bolger  (1988) reported that it is only common to be found in mandibular second molars 15 .Nevertheless, 100% of C-shaped canals were only found in lower molars with fused root which may form either by coalescence owing to cementum deposition with time, or as a result of failure of Hertwig's epithelial sheath to develop fusion in the furcation area 10 .
C-shaped canal appears when fusions of either the buccal or lingual aspect of the mesial and distal roots occur.These fusions remains irregular, and two roots stay connected by an interradicular rib-    Apart from that, there is a very high occurrence in Chinese racial, that is 14.6%, compare to that of non-Chinese racial, 1.04% and among the Cshaped canal that were found, there are All three types of C-shaped canals were found in this study, which were by Type I (continuous Cshape canal); Type II (semicolon-shaped canal) and Type III (comprises 2 or more separate canals) as mentioned by Melton et al. (1991).Among these three types, Type III has the highest frequency and followed by Type II and lastly Type I 8 .Melton also commented on the large amount of debris in instrumented canal space found in histological sections of these teeth, for which many authors agree on using ultrasonic files to facilitate their removal.Accordingly, ultrasonic irrigation with 1.26% sodium hypochlorite and 17% EDTA was used alternatively to remove the smear layer and to enhance the penetration of the plasticized gutta percha.

Conclusion
The findings from this study demonstrated that Cshaped root canals do occur among Malaysian people, and is more commonly to be found in the Chinese population compare to other races.Besides, all the teeth that possess C-shaped root canal configuration are lower molars.Hence, such unusual configuration of the root canal should be recognized earlier and precaution or referral to endodontist should be made.
The occurrence of C-shaped root canal in Malaysian population

Figure 3 :
Figure 3: Example of Type III (C-shaped canal with two or more separate canals)

Table 4
showed that there is almost equal occurrence of C-shaped canal among the different age group.In other words, there is no significant relationship between C-shaped canal and the age group they were found in.

Table 3 : Comparison of the occurrence of C-shaped canal in Chinese and non-Chinese population
Frequency = f; Percentage = %

Table 5 : Frequency of different types of C-shaped canal
7 out of 9 cases or 77.8% in Chinese racial, and this finding is consistent with what reported in previous study byYang et al. (1988)where high prevalence of Cshaped canal was found in Chinese population in 17ported byZheng et al. (2011)that the prevalence of C-shaped canal did not differ with age17.