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ORIGINAL ARTICLE
Year : 2017  |  Volume : 7  |  Issue : 3  |  Page : 156-160

Root canal morphology of mandibular first molars in a North Indian subpopulation: An in vitro clearing study


1 Department of Conservative Dentistry and Endodontics, ITS Dental College, Greater Noida, India
2 Department of Conservative Dentistry and Endodontics, Dr. Z. A. Dental College, AMU, Aligarh, Uttar Pradesh, India
3 Department of Chemistry, Faculty of Sciences, AMU, Aligarh, Uttar Pradesh, India

Date of Web Publication21-Aug-2017

Correspondence Address:
Osama Adeel Khan Sherwani
Department of Conservative Dentistry and Endodontics, ITS Dental College, Greater Noida - 201 306, Uttar Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1658-5984.213480

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  Abstract 

Introduction: Limited information is available about the canal morphology of mandibular first molars in North Indian population. The purpose of this study was to evaluate the root canal morphology of North Indian mandibular first molars by clearing and staining technique.
Materials and Methods: A total of 863 mandibular first molars collected from various places in North India were subjected to canal staining and decalcification procedures. Access cavities were prepared, and pulp tissue dissolved with sodium hypochlorite. Indian ink was injected into the root canals aided by negative pressure applied at the root tips. The stained teeth were decalcified with 7% hydrochloric acid. Instead of ascending concentrations of alcohol, a nonalcohol-based drying agent (anhydrous calcium chloride) was used to remove traces of acid and water from the specimens. The dried specimens were immersed in methyl salicylate to render them transparent. The following features were observed under operating microscope at ×6 magnification: (i) Number of root canals per tooth, (ii) number of root canals per root, (iii) root canal configuration in each root (Vertucci's classification), and (iv) lateral canals, intercanal communications, and their location.
Results: Majority had two roots (85%) with three (61%) and four (30%) canals. Three roots were present in 15% of the specimens. Type IV (49%) and type I (48%) were the most common configurations in mesial and distal roots, respectively.
Conclusion: First molars with two roots and three canals are a common feature in North Indian patients. Both roots showed wide variations in canal anatomy with type IV and type I configurations predominating in mesial and distal roots, respectively.

Keywords: Canal staining, decalcification, mandibular first molar, North Indian population, root canal morphology


How to cite this article:
Sherwani OA, Kumar A, Tewari RK, Mishra SK, Tabassum S, Andrabi SM, Sharma R. Root canal morphology of mandibular first molars in a North Indian subpopulation: An in vitro clearing study. Saudi Endod J 2017;7:156-60

How to cite this URL:
Sherwani OA, Kumar A, Tewari RK, Mishra SK, Tabassum S, Andrabi SM, Sharma R. Root canal morphology of mandibular first molars in a North Indian subpopulation: An in vitro clearing study. Saudi Endod J [serial online] 2017 [cited 2017 Sep 23];7:156-60. Available from: http://www.saudiendodj.com/text.asp?2017/7/3/156/213480


  Introduction Top


Endodontic treatment is aimed at the removal of microorganisms and necrotic tissue from the root canal spaces. This requires thorough cleaning and shaping followed by three-dimensional obturation of the entire root canal system. A clinician can achieve proper disinfection only when he has appropriate knowledge about the canal morphology and the aberrancies associated with it. The study of root canal anatomy has anthropological significance.[1] It is well accepted that genetics influences the root canal morphology with some features being more common in certain races while absent in others. The root and canal anatomy of mandibular first molars has been extensively studied with wide variations reported among different populations.[2] This can be attributed not only to the racial divergence but also to the differences in study designs.

Diaphonization or clearing is an established technique to study the internal anatomy of human teeth. It allows for three-dimensional evaluation of the intricacies of the root canal system.[3],[4],[5],[6],[7] However, the traditional clearing technique uses alcohol as a drying agent [8] which is time-consuming requiring 5–10 days in achieving proper results. This makes the procedure lengthy, especially when the specimen number is large. In the current study, a nonalcohol-based drying agent (anhydrous calcium chloride [CaCl2]) was used in place of ascending concentrations of alcohol that made the procedure simple and yielded transparent specimens in a relatively short period of time.

Limited information is available regarding the canal morphology of mandibular first molars in North Indian population.[9],[10] Hence, there was a need to study the peculiarities in the canal morphology of North Indian mandibular molars. Thus, the aim of the current study was to evaluate the root canal anatomy of two- and three-rooted mandibular first molars in North Indian subpopulation by clearing and staining technique.


  Materials and Methods Top


The study was conducted in the Department of Conservative Dentistry and Endodontics, Dr. Z. A. Dental College, AMU, Aligarh, over a period of 9 months starting from February 2015 to October 2015. A total of 863 mandibular first molars were collected from different places in North India and stored in 4% sodium hypochlorite (Fischer Scientific, Mumbai, India) until collection was complete. It was ensured that the teeth belonged to indigenous North Indians. The age, gender, and cause of extraction were not recorded.

Access opening was done, and the pulp tissues removed by immersing in 4% sodium hypochlorite (Fischer Scientific, Mumbai, India) for 1 h. The teeth were rinsed under running water and allowed to dry for 8–10 h. A 30-gauge endodontic irrigation needle (BU Kwang Medical Inc., Seoul, Korea) was used to inject Indian ink (Sigma-Aldrich, Mumbai, India) into the root canal system with the root apex attached to the central suction system. The injection and evacuation of the ink were repeated thrice at 1-min interval until all the ink exited through apical foramina. The ink was allowed to dry for 4–5 h. Green inlay wax (GC Corporation, Tokyo, Japan) was used to seal the access cavity to prevent or minimize ink dissolution during decalcification.

The specimens were demineralized in 7% hydrochloric acid (Merck Limited, Mumbai, India) for 30–36 h. The acid was stirred after every 5–6 h. The point of optimal decalcification was confirmed by periodic radiographic assessment at 6 h interval and insertion of a needle in the crown portions. The teeth were washed in running water to remove acid residues and dried overnight at room temperature. The decalcified specimens were placed in methyl salicylate (Fischer Scientific, Mumbai, India) for 1 min and then subjected to dehydration in anhydrous CaCl2 (RFCL Limited, New Delhi, India) for 2 h. The dehydrated samples were then placed in methyl salicylate for 6–8 h to render them transparent. The samples were monitored every 3–4 h for transparency and were removed from the oil when they were considered cleared enough to obtain relevant information about their root canal morphology.

The transparent specimens were examined under operating microscope (Seiler IQ, Chicago, IL, USA) at ×6 magnification for the following features: (i) Number of root canals per tooth, (ii) number of root canals per root (defined as highest number of canals visualized in one root of a transparent specimen), (iii) root canal configuration in each root, and (iv) lateral canals, intercanal communications, and their location. The canal configurations were classified according to Vertucci's classification.[4] All additional configurations were noted and categorized [Figure 1].
Figure 1: Cleared roots with different canal configurations: (a) Type I, (b) Type II, (c) Type III, (d) Type IV, (e) Type V, (f) Type VI, (g) Type VIII, (h) Type 3-2, (i) Type 4-2-3-2, (j) Type 2-3-2-1, (k) Type 4-3-1

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  Results Top


[Table 1] and [Table 2] represent the root and canal morphologies of 863 specimens.
Table 1: Mandibular first molar: Number of roots and canals

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Table 2: Mandibular first molar: Root canal configuration, intercanal communications, and lateral canals

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Number of roots and root canals

Two and three separate roots were found in 85% and 15% of the first molars, respectively. The third root was exclusively found on the lingual aspect of distal roots. The majority had three (61%) and four (30%) canals while rest had two (1.5%) and five (7.5%) canals.

Root canal configuration

Most of the mesial roots had two canals (86%) with type IV (49%) and type II (24%) being the most common configuration. Nearly half of the distal (48%) and all the distolingual (100%) roots had one canal. Type I (48%) followed by type II (28%) and type IV (15%) was the most common configurations found in distal roots.

Lateral canals and intercanal communications

Lateral canals and intercanal communications were more common in mesial roots. In the mesial roots, intercanal communications were more common in cervical (14%) and middle thirds (12%). In the distal roots, cervical third (6%) had more intercanal communications compared to middle (3%) and apical thirds (4%). Lateral canals were more common in the apical third of mesial (6%) and distal roots (10%).


  Discussion Top


The root canal anatomy is a widely studied subject right from the 19th century. The first detailed and comprehensive description of the root canal anatomy was published in 1842 in the form of drawings of sectioned teeth.[11] A wide variety of techniques have been employed in understanding the canal morphology including radiographic examination,[12],[13] sectioning of roots,[14],[15] staining and clearing techniques,[3],[4],[5],[6],[7],[8] computed tomography,[14] spiral computed tomography,[16] cone-beam computed tomography (CBCT),[17] and micro-computed tomography (micro-CT).[18]

Although contemporary studies have reported an increased use of three-dimensional imaging systems such as CT, CBCT, and micro-CT,[14],[15],[16],[17],[18] canal staining and clearing has been the most commonly used technique evaluating the canal morphology.[2] These newer radiographic techniques help in proper visualizing the canal anatomy in an easy and noninvasive manner. Nevertheless, the staining technique has always stood the test of the times in providing valuable results. The traditional technique uses ascending concentrations of alcohol to remove acid and water from the specimens.[8] This step requires at least 24–36 h to achieve optimal drying of specimens. In our study, alcohol was replaced by anhydrous CaCl2 which is hygroscopic in nature and tends to absorb moisture. However, care must be exercised in preventing CaCl2 from coming in contact with the air as it rapidly absorbs water from the air. It must always be kept in an airtight container. It is worth mentioning that the specimens were immersed in methyl salicylate for 1 min before the dehydration step to prevent over-desiccation that may distort the original anatomy of the tooth and yield false results.

The mandibular first molar frequently requires endodontic treatment with the success rate lower (81.48%) than that for other teeth (87.79%).[19] This may be attributed to a high incidence of variations including additional canals,[10],[20] the presence of isthumi,[18] C-shaped roots,[21] and separate distolingual roots.[22] Ethnicity plays an important role in determining the number of roots in mandibular molars with Mongoloid, Native American, Eskimo, and Chinese populations having a higher prevalence of three roots compared to others.[2] In the current study, the prevalence of three roots was found to be 15%, which was in agreement with some of the previously published studies.[5],[23] However, it was higher than a similar study done in an Indian population.[9] This could be attributed to some extent to a large number of teeth included in this study.

The majority of first molars had three (61%) and four (30%) canals. In the mesial roots, type IV (49%) and type II (24%) configurations were more commonly found. These findings were consistent with those of Gulabivala et al. in a Thai population [5] and Skidmore and Bjorndal in Caucasians.[24] Type III, type VI, and type VIII configurations were found in approximately 09%, 05%, and 07% of the specimens. Cleaning and shaping of type II and IV canals is relatively simple owing to their separate orifices and course up to the apical third or apical foramen. However, cases in which canals branch in middle and apical thirds (type III, type V, type VI, and type VII) require a more aggressive approach in terms of locating, negotiating, cleaning, and shaping of the entire root canal system. Such canal morphologies could probably be responsible for some of the unexplained treatment failures despite radiographically esthetic root canal obturation.

Nearly half of the distal roots had type I (48%) followed by type II (28%) and type IV (15%) configurations. These findings were consistent with those of Al-Qudah and Awawdeh in a Jordanian population [7] and Pattanshetti et al. in a Kuwaiti population.[25] Two canals were present in approximately 49% of the specimens; however, only 17% exited through separate apical foramina. The distal root is round than the mesial one which could partially account for the low percentage of two foramina found in distal roots.

Intercanal communications were noted in 35% of mesial and 14% of the distal roots similar to the findings of Al-Qudah and Awawdeh [7] and Gulabivala et al.[5] The lateral canals were more frequently found in the apical thirds of both the roots. The lateral canals and intercanal communications harbor necrotic tissues and microbial products that must be effectively cleaned for the success of root canal therapy. However, it is not always possible to debride and fill these ramifications adequately. In such cases, irrigation plays an important role in the removal of microbes from the uninstrumented areas.[26] Moreover, thermoplasticized gutta-percha can be used to seal such communications satisfactorily.[27]


  Conclusion Top


Fifteen percent of the specimens had three roots which can be considered as a mongoloid trait. In the mesial and distal roots, type IV and type I configurations were more commonly found, respectively. The changes in the traditional clearing technique yielded better results in a relatively small period of time.

Acknowledgement

The authors would like to thank Dr. Craig Barrington DDS, United States for his help and support in modifying the traditional clearing technique.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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    Figures

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    Tables

  [Table 1], [Table 2]



 

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