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 Table of Contents  
Year : 2020  |  Volume : 32  |  Issue : 2  |  Page : 72-75

Retrospective analysis of the occurrence and distribution of radix entomolaris in mandibular first molars: A hospital-based study

Department of Conservative Dentistry and Endodontics, KVG Dental College and Hospital, Sullia, Karnataka, India

Date of Submission30-Sep-2019
Date of Decision12-Jan-2020
Date of Acceptance01-Feb-2020
Date of Web Publication18-Jun-2020

Correspondence Address:
S Karthika Raj
Department of Conservative Dentistry and Endodontics, KVG Dental College and Hospital, Kurunjibag, Sullia DK - 574 327, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/endo.endo_66_19

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Aim: This study aimed to evaluate clinically the prevalence of radix entomolaris (RE) in mandibular first molars in Dakshina Kannada population.
Materials and Methodology: Proper clinical records and soft copies of radiographs of patients who had reported to the department of conservative dentistry and endodontics in a private dental college and hospital in Dakshina Kannada to seek root canal treatment from January 2015 to July 2019 were collected for the study. The occurrence and distribution of RE revealed by periapical radiographs and clinical case records were analyzed, and the comparison of the occurrence between males and females, and between the right and left sides, was done. Statistical analysis was done using the Chi-square test and binary logistic regression test with a statistically significant level set at P ≤ 0.05.
Results: Among 1093 treated mandibular first molars, 52 teeth were RE. There was a significant difference in the prevalence of RE between males and females, but there was no significant difference between right and left sides' occurrence.
Conclusions: Clinicians must be familiar with RE and its variations to reduce endodontic failures caused by missing canal.

Keywords: Distolingual root, endodontic management, mandibular first molars, morphologic variation, radix entomolaris

How to cite this article:
Kumar K N, Prasada L K, Raj S K. Retrospective analysis of the occurrence and distribution of radix entomolaris in mandibular first molars: A hospital-based study. Endodontology 2020;32:72-5

How to cite this URL:
Kumar K N, Prasada L K, Raj S K. Retrospective analysis of the occurrence and distribution of radix entomolaris in mandibular first molars: A hospital-based study. Endodontology [serial online] 2020 [cited 2020 Oct 24];32:72-5. Available from: https://www.endodontologyonweb.org/text.asp?2020/32/2/72/287072

  Introduction Top

Thorough chemomechanical debridement and proper obturation relies on the better knowledge of the morphology and anatomy of the root and its canal, which would benefit clinicians in locating, negotiating, and cleaning canals in routine dental practice.[1]

Endodontic therapy of mandibular molars has always been an endodontic dilemma as it has shown several anatomic and morphologic variations. Carabelli in 1844 first mentioned one such major variation as the presence of a supernumerary root on the distolingual position of mandibular molars and later in 1922, Mihlay Lenhossek called it as radix entomolaris (RE). If an extra root is present on mesiobuccal area, then it is called radix paramolaris (RP). As per literature, RE is more frequent than RP.[2],[3] Previous studies proved that its prevalence varies in different ethnic groups. When compared with other populations, Asians showed a traditionally higher prevalence, with the incidence of < 5% in Indians.[4],[5],[6]

RE is associated with many morphologic traits such as crown dimension, the interorifice distance of canals, periodontal destruction, and the distance to the buccal cortical bone.[7]

Various methodologies such as the use of clearing technique, cross-sectioning technique, analysis of extracted teeth, conventional radiography, and cone-beam computed tomography (CBCT) have been employed to assess the root and root canal morphology.[5] Even though CBCT is seemed to be superior in identifying the anomalies of root morphology than periapical radiographs, it is not practical in daily dental practice.[2]

Given the known ethnic variations in supernumerary roots and the lack of data on contemporary populations in Dakshina Kannada, the present study followed a retrospective design to assess the prevalence of RE in the Dakshina Kannada population.

Aims and objectives of study

  1. To find out the prevalence of RE in the Dakshina Kannada population
  2. To assess the ratio of occurrence of RE in males and females
  3. To compare right- to left-side occurrence of RE.

  Materials and Methodology Top

The study design was retrospective in nature. Proper clinical records and soft copies of radiographs of patients who had reported to the department of conservative dentistry and endodontics in a private dental college and hospital in Dakshina Kannada to seek root canal treatment from January 2015 to July 2019 were collected for the study. The entire study was done in the hospital. Case records were collected by an independent observer.

Inclusion criteria

  1. Participants had to be of Dakshina Kannada origin
  2. Root canal treatment should be done for at least one mandibular first molar.

Exclusion criteria

  1. Absence of proper clinical and radiographic records of the treated teeth.

Screening of all the data was done as per the inclusion and exclusion criteria. Personal details, including sex and address, were analyzed from the clinical records collected. Soft copies of radiographs taken with a mesial angulation of 30° were analyzed by two independent observers.

The presence of an extra root was justified by the crossing of the translucent lines defining the pulp space and periodontal ligament, originating in the upper half of the distal root in the mandibular first molar. The total prevalence and the ratio of occurrence of RE in males and females were assessed. The comparison of right- to left-side occurrence of RE was also estimated.

Statistical analysis

The prevalence, side specificity, and the ratio of the occurrence in both genders of RE were assessed statistically using SPSS version 23 (Amonk, IBM Corp., NY) with statistical significance level set at P ≤ 0.05. To find out the statistical difference in the occurrence of RE on gender basis, the binary logistic regression test was used. The side specificity difference between the right and left sides was analyzed by Pearson's Chi-square test.

  Results Top

Of the 1124 clinical records and radiographs initially examined, 1093 were qualified for further analysis. Among these examined records, 642 (58.7%) were male and 451 (41.3%) were female. The prevalence of RE was 4.8% (52/1093 teeth) [Flowchart 1]. The frequency of distribution was 44.23% (23/52 teeth) and 55.77% (29/52 teeth) for men and women, respectively [Table 1]. In the frequency distribution of RE in terms of right to left side, specificity was 2.2% (24/52) to 2.6% (28/52), respectively. However, this difference was not statistically significant [Table 2]. Logistic regression model for gender was statistically significant, which is given in [Table 3].
Table 1: Association between the presence of radix entomolaris and gender

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Table 2: Association between radix entomolaris and side

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Table 3: Binary logistic regression - Gender

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  Discussion Top

Walker proposed RE as a genetic trait rather than a developmental aberration, and it is also considered to be a morphologic variant seen as an Asiatic trait.[4],[8] It was claimed that external factors affecting dentin formation or presence of an atavistic gene could result in the formation of supernumerary roots.[7] Mu et al. had done mutational analysis of genes involved in tooth root formation and tooth development such as axin inhibition protein 2, msh homeobox 1, and paired box gene 9 in different ethnicities.[9],[10]

The prevalence of RE reported in literature was 3% in African population, < 5% in Eurasian and Indian populations, 5%–40% in Mongoloid traits (Malay, Chinese, Eskimo, and American Indian).[6] Our results found the prevalence of RE as 4.8%. It is close to reports from other regions of India.[10],[11] However, it is low when compared with data reported for Asian races such as 24.5% in Koreans, 32% in Chinese, and 25.6% in Taiwanese.[8] Ahmed et al. reported a prevalence of 3% of RE in Malaysian population also.[6]

Side and gender specificity in RE showed several variations in literature. Our findings were similar to those of previous studies by Schäfer et al. and Peiris et al. They found that there was no significant difference between sides in the prevalence of RE. At the same time, some authors already reported that RE can occur more on the left side.[12],[13],[14],[15]

In retrospective studies conducted by Shemesh et al. and Esaghet al., the authors found that there was no significant difference in the prevalence of RE among sexes.[7],[8] However, another study done by Colak et al. in Turkish population found an almost equal distribution between males and females.[7]

Our study found that females had 1.849 times more chance of having radix compared to males. However, currently, there is no explanation for the greater prevalence of RE in females. Additional evidence is required to evaluate the high prevalence of RE in females even though genetic factors have considerations.[5]

Radiography has an inevitable role in the success of endodontic treatment. In order to avoid inaccurate diagnosis in RE due to superimposition as distobuccal roots lie in same buccolingual plane, parallax technique should be preferred.[6],[16]

The replacement of traditional radiography with digital radiography, microcomputed tomography scans, and CBCT gave more accurate diagnosis in RE. With a good understanding of the law of symmetry, various methods such as visualizing the dentinal map and canal bleeding points using loupe, intraoral camera, or dental microscope, ultrasonic tips, staining the chamber floor with 1% methylene blue dye, and performing champagne bubble test will also help in the identification of extra orifice.[8],[17]

However, the preliminary diagnosis is always done with the conventional radiographic techniques. In this study, we preferred periapical radiographs rather than techniques such as CBCT as CBCT is not practical in routine practice. Moreover, 90% accuracy is shown by conventional radiography in detecting RE.[4],[18]

The orifice of the RE is usually located distolingually to mesiolingually from the main canal or distal root canal. Hence, extending the triangular access cavity to a more rectangular or trapezoidal outline form distolingually diagnoses RE accurately in clinical situations.[4] As per Tu et al., the mean interorifice distances from the distolingual canal to the distobuccal, mesiobuccal, and mesiolingual canals of the RE were 2.7, 4.4, and 3.5 mm, respectively.[19] A dark line on the pulp chamber floor can also be a hint toward the precise location of the RE canal orifice.[20] Due to the complicated anatomy of RE, furcal or strip perforation, vertical root fracture, root canal transportation, and instrument fractures can often occur while doing instrumentation. Special attention should be given to avoid these complications. Especially, clinicians should be very careful in removing dentin from the lingual side of the cavity and orifice of the RE.[16],[21]

  Conclusions Top

With the known variations in the prevalence of RE in different populations, this study confirms 4.8% prevalence of RE in the Dakshina Kannada population. This gives the necessity of proper radiological assessment before the initiation of endodontic therapy. During endodontic practice, it is essential to find all the canals as missed canals can cause earlier endodontic failure. Moreover, De Moore et al.[22] studied the morphology of RE and concluded that root curvature is the main challenge of RE. Thus, special attention should be given while treating RE.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Gupta A, Duhan J, Wadhwa J. Prevalence of three rooted permanent mandibular first molars in Haryana (North Indian) population. Contemp Clin Dent 2017;8:38-41.  Back to cited text no. 1
[PUBMED]  [Full text]  
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López-Rosales E, Castelo-Baz P, De Moor R, Ruíz-Piñón M, Martín-Biedma B, Varela-Patiño P. Unusual root morphology in second mandibular molar with a radix entomolaris, and comparison between cone-beam computed tomography and digital periapical radiography: A case report. J Med Case Rep 2015;9:201.  Back to cited text no. 3
Ratnakar P, Saraf PA, Patil TN, Karan S. Endodontic management of radix entomolaris: Two case reports. Endodontology 2018;2:163.  Back to cited text no. 4
Wu YC, Su CC, Tsai YC, Cheng WC, Chung MP, Chiang HS, et al. Complicated root canal configuration of mandibular first premolars is correlated with the presence of the distolingual root in mandibular first molars: A cone-beam computed tomographic study in Taiwanese individuals. J Endod 2017;43:1064-71.  Back to cited text no. 5
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Mu YD, Xu Z, Contreras CI, McDaniel JS, Donly KJ, Chen S. Mutational analysis of AXIN2, MSX1, and PAX9 in two Mexican oligodontia families. Genet Mol Res 2013;12:4446-58.  Back to cited text no. 9
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Duman SB, Duman S, Bayrakdar IS, Yasa Y, Gumussoy I. Evaluation of radix entomolaris in mandibular first and second molars using cone-beam computed tomography and review of the literature. Oral radiology. 2019:1-7.  Back to cited text no. 16
Baranwal HC, Kumar N, Singh A. Radix entomolaris: An endodontic challenge-a case report. J Adv Med Dent Sci Res 2019;7:29-31.  Back to cited text no. 17
Bains R, Bains VK, Loomba K, Loomba A. Prevalence of radix entomolaris and fused roots in mandibular permanent molars of a North Indian population: A hospital-based retrospective radiographic study. Indian J Oral Sci 2016;1:19.  Back to cited text no. 18
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Calberson FL, De Moor RJ, Deroose CA. The radix entomolaris and paramolaris: Clinical approach in endodontics. J Endodont 2007;33:58-63.  Back to cited text no. 21
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  [Table 1], [Table 2], [Table 3]


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