Root canal configuration of permanent maxillary first molar in Khasi population of Meghalaya: An in vitro study.

AIMS AND
OBJECTIVE: To investigate the root canal configuration of permanent maxillary first molar in Khasi population of Meghalaya.
MATERIAL AND METHODS: Sixty (60) permanent maxillary first molars collected from patients of Khasi population of Meghalaya were studied using canal staining and clearing technique. Observations of the number of roots, root canal configuration, lateral canal, apical delta, and presence of the additional type of canals were made.
RESULTS: Based on Vertucci's classification the different types of canal identified are: Mesiobuccal root, Type I (28.3%), Type II (28.3%), Type IV (30.0%), Type V (5.0%), Type VI (6.7%), and an additional type of canal (2-1-2-1-2; 1.7%) were observed. The distobuccal root displayed Type I (95%), Type II (1.7%), Type V (3.3%). The most prevalent canal configuration in the palatal roots is Type I (98.3%), Type II (1.7%).
CONCLUSION: In Khasi population of Meghalaya, the most prevalent root canal configuration in the mesiobuccal root is Type IV followed by Type I and Type II. MB2 canals are present in more than 65% cases. In palatal and distobuccal roots, Type I configuration is present in most cases. Racial divergence may be responsible for such variations.

INTRODUCTION

Knowledge of root canal anatomy is essential for the successful endodontic treatment. The variability of root canal system morphology of multi-rooted teeth represents a continuous challenge to endodontic diagnosis and treatment. Nevertheless the knowledge of the “normal” pulp system and its most frequent changes is basic for a clinical success.[1] Morphology of pulp systems varies greatly in different races and in different individuals within the same race.[2] Internal complexities of the root canal are genetically determined and have definitive importance in anthropology, thereby necessitating the identification of root canal morphologies of different ethnic populations.[3]

The Indian subcontinent has been inhabited by different linguistic groups (Austro-Asiatic, Dravidians, Tibeto-Chinese, and Indo-Europeans) at different time periods. Austro-Asiatic linguistic family in India is represented by 30 tribal populations, representing 3 broad subfamilies, the Mundari, the Khasi-Khmuic, and the Mon-Khmer. The groups speaking Khasi-Khmuic and the Mon-Khmer languages have Mongoloid features are probably of Asian origin, making this linguistic group ethnically more heterogeneous compared to other linguistic groups in India.[4]

There have been no studies of the root canal morphology in such genetically heterogenous population groups. So, the following study was done with the aim to identify the root canal configuration of the permanent maxillary first molar and its variation in the Khasi tribe of Meghalaya.

MATERIALS AND METHODS

Sixty permanent maxillary first molars extracted from indigenous Khasi patients (from Jowai, Nongstoin, and Umsning CHC, Meghalaya) were collected. Teeth were cleaned of calculus and soft tissues and access cavity was prepared. The pulp tissue was removed by immersing teeth in 5% sodium hypochlorite (Endo wash, Novo dental products, Mumbai) for 48 hours followed by rinsing in running water for 2 hours.

The study of the root canal was done by canal staining and clearing technique adopted from the study by Shahriar Shahi et al.[5] Decalcification of teeth was done by immersing in 5% nitric acid for 3 days which was renewed daily. The end point of decalcification was confirmed by using paper pin (penetrating the crown portion easily) and radiographically by the appearance of complete radiolucency.

The decalcified teeth were washed for 4 hours in running water to remove the traces of nitric acid and dried by blowing air with help of a three way syringe.

Indian ink (Hi Media lab, Mumbai) was then injected into the canals with the help of a syringe and 26-gauge needle. The excess dye was wiped off from the tooth surface with the help of the alcohol-soaked gauge. The dehydration of the teeth was done by successive rinses of ethyl alcohol starting with 70% for 24 hours, 80% for 12 hours, 90% for 1 hour, 95% for 1 hour, and then three 100% rinses for 1 hour each. The dehydrated teeth were placed into methyl salicylate for 2 days to make them transparent, i.e., easy to visualize.

The internal anatomical details were examined in all directions using 5× magnifying glass. After evaluation, the teeth were placed immediately in a separate container of methyl salicylate to avoid loss of transparency. The following observations were made (1) number of roots and root canals, (2) root canal configuration in each root, (3) presence and location of intercanal communications, (4) lateral canals, and (5) apical delta. Vertucci's classification[6](with additional modification) was used for identification and classification of root canal anatomy in the study.

Chi-square test was used to compare the frequencies of categorical data. The frequency of occurrence of a particular type of canal in the population studied was compared with data obtained from previous studies in different populations.

RESULTS

Results are shown in Tables 1–7.

Table 1

Number of roots and root canals

Table 7

Apical delta observed in permanent maxillary first molar

Number of roots and canals [Table 1]: Three roots were found in 58 (96.7%) teeth out of which 18 teeth had three canals, 38 teeth had four canals, and in 2 teeth five canals were found. Remaining 2 teeth were two rooted with three canals in each tooth.

Root canal configurations [Table 2] (Vertucci's classification)[6]: As shown in Table 2 mesiobuccal root displayed complex root canal types with Type I (28.3%), Type II (28.3%), Type IV (30.0.%), Type V (5.0%), and Type VI (6.7%). MB2 canals were found in 65% teeth (39 teeth) and had mainly Type II and Type IV configurations [Figure 1].

Table 2

Different types of root canal configuration of maxillary permanent first molars

Figure 1

Different types of root canal configurations observed in permanent maxillary first molar

Distobuccal root had Type I (95.0%), Type V (3.3%), and Type II (1.7) configurations. Palatal root had Type I (98.3%) and Type II (1.7%) configurations.

Intercanal communications [Table 3]: In the mesiobuccal canal intercanal communications were found in coronal third (11.7%), coronal-middle third (10%), middle third (11.7%), and middle-apical third (3.3%) while 63.33% teeth had no intercanal communications.

Table 3

Intercanal communications in mesiobuccal root of maxillary permanent first molar

Lateral canals [Tables 4–6]: In the mesiobuccal root, the apical third had 8.3%, middle third had 5%, coronal third had 1.7%, and middle-coronal third had 1.7% lateral canals. In the distobuccal root, 1.7% lateral canals were found in coronal and middle third. In the palatal root, 117% lateral canals were identified in the apical third, 6.7% in middle third, and 3.3% in coronal-middle third.

Table 4

Lateral canals in the mesiobuccal roots of maxillary permanent first molar

Table 6

Lateral canals in the palatal roots of maxillary permanent first molar

Apical delta [Table 7] was most common in mesiobuccal root (25%) followed by the palatal root (8.3%) and distobuccal root (5%).

The data was analysed using Chi-square test by the Statistical Package for the Social Sciences [(SPSS Inc, Chicago, USA)version 16] statistics software; the significance level of the test was set at P < 0.05. Chi-square value was 42.713 (P < 0.01) for the apical deltas and was highly significant. According to the number of roots [Table 1] lateral canals in mesiobuccal root [Table 4], distobuccal roots [Table 5], and palatal roots [Table 6] the value of P was found to be non-significant.

Table 5

Lateral canals in the distobuccal roots of maxillary permanent first molar

DISCUSSION

The variability of root canal morphology of multi-rooted teeth present a continuous challenge to endodontic diagnosis and treatment.[7] The permanent maxillary first molar is generally considered to be a three rooted tooth with the palatal, distobuccal, and mesio-buccal roots. In the present study, the maxillary first molar is predominantly a three-rooted tooth (96.7%) with only (3.3%) of the two rooted form, where the palatal root is fused with the distobuccal root. Previous studies also reported high incidence of three-rooted maxillary molars. Neg et al.[8] reported all 90 (100%) three-rooted maxillary molars in Burmese population. Pecora et al.[9] found 86.4% three-rooted, 7.9% with Buccal root fused, 5.0% where the Lingual and distobuccal fused together, and 0.7% teeth with all the root fused together out of 140 permanent maxillary first molars. Thomas et al.[10] reported, out of 216 maxillary molars 204 had three roots, 9 in which the distobuccal and palatal roots are joined, and 3 in which the distobuccal and mesiobuccal are joined.

The technique of clearing teeth has considerable value in studying the anatomy of the root canal system because unlike radiographic images, it provides a three-dimensional view of the pulp cavity in relation to the exterior of the teeth. In terms of accuracy only cone-beam computed tomography (CBCT) and peripheral quantitative computed tomography (pQCT) have been found to be comparable to it.[11]

The types of canals observed in the mesiobuccal root are complex. Type I and Type II are 28.3% each. The most prevalent canal is Type IV (30%); other configurations are: Type V (5.0%) and Type VI (6.7%). Variation in the root canal morphology observed is an additional type of canal (2-1-2-1-2). The type of canal configurations of the mesiobuccal root in the present study shows close resemblance with the study of Shahriar Shahi et al.,[5] in an Iranian population which reported Type I (37.96%), Type II (24.08%), Type IV (24.18%) Type V (9.5%), and Type VI (4.38%) configuration.

Similarly a study by Wasti et al.[12] of the maxillary first molar of South Asian Pakistanis (30 samples) reported the root canal system in the mesiobuccal root was Type I (33.3%), Type II (23.3%), Type IV (23.3%), Type V (13.3%), and Type VI (6.8%). Vertucci[6] reported the canal configuration of maxillary first molar (mesiobuccal root) of 100 teeth with Type I (45%), Type II (37%), Type III (0), Type IV (18%), Type V (0), Type VI (0), Type VII (0).

The present findings revealed a difference in the occurrence of Type V and VI canals which were absent in Caucasians population and a higher prevalence of Type IV configuration.

Meanwhile, Weine et al.[13] reported 30.4% (sample of 293 molars) and Alavi et al.[14] reported 44.2% (sample 52) Type IV configurations. This higher prevalence of Type IV may be considered as a Mongoloid trait.

The findings of present study cannot be generalised even within an Indian population. Neelakantan et al.[3] reported the canal morphology of 220 maxillary first molars of an indigenous Indian population. Three-rooted first molars in the mesio-buccal root showed high incidence of Type I configuration (51.8%). Type II were 5.5%, Type-IV (38.6%), and additional canal types (2-3) were 1%.

In the distobuccal root, the most prevalent configuration is Type I, i.e., 95% (57 teeth), Type V (3.3%), and Type II (1.7%). The palatal root has Type I (98.3%) and Type II (1.7%) configurations. Cleghorn et al.[15] mentioned that 98.3% of distobuccal roots displayed one canal; two canals were found in (1.7%). In the palatal root, Type I (99%) with two or more canals in 1 % teeth. In the present study, the types of canal in the distal root are similar to those reported by Weng et al.[16] with Type I 40 (88.9%), Type II 3 (6.7%), Type V 2 (4.4%).

Intercanal communications were observed in mesiobuccal root with coronal third in 7 (11.7%), coronal-middle 6 (10%), middle third 7 (11.7%), middle-apical third 2 (3.3%). The finding are slightly lower than that reported by Khraisat et al.[17] in the Jordanian population (100 molars) with the coronal-third 12 (12.7%), middle-third 16 (16.47%), and apical-third 8 (8.25%).

The lateral canals in the mesiobuccal root are most inapical third 5 (8.3%) followed by middle third (5.0%), middle-coronal third (1.7%), and coronal third (1.7%). In the distobuccal root 1.7% were found in coronal and middle third. In the palatal roots the lateral canals in apical third are 11.7%, middle third 6.7%, and coronal-middle third 3.3%. Ng et al.[8] reported 7.15% lateral canals in apical third. Weng et al.[16] reported the distribution of lateral canals as 35.8% in the mesiobuccal root, palatal root (22.2%), and distobuccal root (18.8%).

The apical deltas found in the present study show the highest incidence in the mesiobuccal root (25%) followed by palatal (8.3%) and distal root (5%).

CONCLUSION

In Khasi population of Meghalaya, the most prevalent root canal configuration in the mesiobuccal root is Type IV followed by Type I and II. MB2 canals are present in more than 65% cases. In palatal and distobuccal roots, Type I configuration is present in most cases. Racial divergence may be responsible for such variations. Further studies with large sample sizes are needed for a more accurate description of root canal anatomy of North-eastern population of India.