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Authors: Dr. Poonam, Dr. Manoj Kumar Hans

Abstract

Aims and objectives: The aim of the study was to determine the prevalence of extra roots in mandibular first molars, their gender and side-related differences aided with cone beam computed tomography (CBCT). Materials and methods: Screening of CBCT images of 2022 mandibular first molars in 1011 patients possessing bilateral mandibular first molars was done. The prevalence of extra roots on mandibular first molars in the patients; their correlations between the right-side and the left-side occurrences and between female and male patients were analyzed by using the chi-square test. Results: The prevalence of extra roots in the mandibular first molars was 4.58% for female patients and 1.77% for male patients. The overall prevalence of extra roots on the mandibular first molars was 2.86% for all patients and 2.27% for all teeth. No stastically significant difference was found between right and left side. Conclusion: The prevalence of extra root was low in this study but clinicians should be aware of the morphological variations of the tooth like additional roots, root canals and their incidence.

Keywords:

Cone beam computed tomography; extra roots; prevalence; radix entomolaris.

Introduction

The prevention or healing of endodontic pathology depends on a thorough chemomechanical cleansing and shaping of the root canals before a dense root canal filling with a hermetic seal. An awareness and understanding of the presence of unusual root canal morphology can thus contribute to the successful outcome of root canal treatment. The majority of Caucasian first molars are two-rooted with two mesial and one distal canal. The major variant in this tooth type is the presence of an additional third root; a supernumerary root which can be found lingually. This macrostructure, which is first mentioned in the literature by Carabelli (1844), is called Radix Entomolaris (RE).1 RE was classified into three type according to the buccolingual variations. Type I refers to a straight root, Type II to an initially curved entrance than continues as a straight root, and Type III to an initial curve in the coronal third of the root canal, followed by a second curve beginning in the middle and continuing to the apical third.2 Recently, RE was further classified into 5 types according to their morphological characteristics. Two additional types are Type IV (small type), where root length less than half that of the distobuccal root, and type v(conical type), which is a cone-shaped extension with no root canal.3 Recently, cone-beam computed tomography (CBCT) has emerged as a useful tool to aid in the diagnosis of teeth with complex root anatomies. It is an imaging method employing tomography to generate a three-dimensional reconstruction of the entire tooth at different levels from a single imaging procedure. The advantages of CBCT imaging are that it completely eliminates the superimposition of structural images outside the area of interest and provides a high-contrast resolution and data from a single computed tomography imaging process.4 Moreover, the images can be viewed in a coronal, sagittal, or even an oblique or curved image planes—a process referred to as Multiplanar Reformation (MPR).In addition, CBCT data is amenable to reformation in a volume, rather than a slice, providing three dimensional images in the axial, coronal, or sagittal planes.5 The purpose of this study was to determine the prevalence of extra roots in mandibular molars, their gender and side-related differences aided with cone beam computed tomography.

Materials and Methods

Screening of 1011 CBCT images from Soumitra dental imaging solutions during the period December 2012 - June 2014 was done. The age, sex and side (left or right ) of each patient were recorded. CBCT images of 2022 mandibular first molars in 1011 patients ( 618 male and 393 female) possessing bilateral mandibular first molars were taken. CBCT images were obtained using Simulix Evolution ; Nucletron, Chennai, India Pvt Ltd with a tube voltage 100 kV and a tube current of 8 mA. Selection criteria was as follows:1) presence of bilateral fully erupted permanent mandibular first molars; 2) the permanent mandibular first molars had to have fully formed apexes, no root canal fillings, posts, or crown restorations. The prevalence of extra roots on mandibular first molars in the patients; their correlations between the right-side and the left-side occurrences and between female and male patients were analyzed by using the chi-square x2 test. The bilateral prevalence of extra roots on mandibular first molars was also enumerated.

Results

1011 patients (618 males and 393 females) aged between 18-45 years were screened in this study. A total of 2022 mandibular first molars were evaluated and the results were tabulated (Table 1). Gender-related difference (x2 = 5.793, p = 0.0161) found to be statistically significant for the prevalence of extra roots on mandibular first molars. The prevalence of extra roots on the mandibular first molars was 4.58% for female patients and 1.77% for male patients (Table 2). The overall prevalence of extra roots on the mandibular first molars was 2.86% for all patients and 2.27% for all teeth. No stastically significant difference was found between right and left side (x2=0, p=1) (Table 3). Of the unilateral occurring teeth the prevalence on the left side was found to be 0.24% and right side was 0.34% (Figure1a, b, c). The bilateral prevalence of all teeth was found to be 1.68% (Figure 2a, b, c)



Tables

Table 1: depicting the numbers and percentages of patients with extra root according to gender, side related (unilateral and bilateral) and total occurrence.


NO. OF PATIENTS

UNILATERAL
RIGHT       %        LEFT    %

BILATERAL
NO.            %

TOTAL
NO.                  %

Females (393)

4              (1.01)       3   (0.75)

11            (2.79)       

17                 (4.32)

Males(618)

3             (0.48)       2    (0.32)

6              (0.97)

12                 (1.91)

Total no of patient(1011)

7             (0.69)       5    (0.49)

17            (1.68)              

29                 (2.86)

No. Of pts examined

7             (0.34)      5     (0.24)   

34            (1.68)

46                 (2.27)              


Table 2: depicting the significant difference between male and females.

 

Presence of extra root

Absence of extra root

Total cases

Male

11

607

618

Female

18

375

393

Total

29

982

1011

x2=5.793, d.f=1, p=0.0161 significant


Table 3: suggesting the side related difference (left and right side).

 

Presence of extra root

Absence of extra root

Total cases

Right side

24

987

1011

Left side

22

989

1011

Total

46

1976

2022

x2=0, d.f.=1, p=1 not significant

 
 
 

Table 4: studies of the prevalence of extra roots in mandibular molars.


Author

Year of study

Prevalence (%)

Ethnic groups

Tratman7

1938

 5.8

Chinese

Loh14

1990

7.9

Chinese ( Singapore)

Yew and Chan10

1993

21.5

Chinese

Sperber and Moreau6

1998

3.0

Senegalese

Gulabivala et al15

2001

10.1

Burmese

Ali & Abdul–Haq16

2006

8.1

Iraqi

Ruwan & Thomas17

2007

26.4

Chinese(Hong Kong)

Ming-Gene et al18

2009

33.3

Taiwanese

Garg et al19

2010

5.97

Indian

Zhang et al20

2011

29

Chinese


Discussion

The present study used CBCT method to determine the prevalence of extra root in mandibular first molars in north-western Indian population and found it to be 2.86%. Significant difference was found between the males and females. No significant side (left and right) related difference was seen. In Black populations, the maximum frequency found is 3%,6 while in Caucasians and Indians, the occurrence is lower than 5%.7 In Chinese, Eskimos, and American Indian population, studies have shown that radix entomolaris occurs in a constancy ranging from 5% to more than 30%.8 The prevalence of permanent mandibular first molars with 3 roots, as detected in periapical radiographs, is reportedly high among Chinese populations (21.1%–26.9%).9-11 Dental variants have been found more frequently on the left side in Singaporean Chinese and British white subjects.12,13 Several studies have reported prevalence of extra roots in mandibular molars in the range of 3.0-33.3% (Table 4).14-20 Some studies report a bilateral occurrence of the RE from 50 to 67%.21 The RE is located distolingually, with its coronal third completely or partially fixed to the distal root. The dimensions of the RE can vary from a short conical extension to a ‘mature’ root with normal length and root canal. In most cases the pulpal extension is radiographically visible. In general, the RE is smaller than the distobuccal and mesial roots and can be separate from, or partially fused with, the other roots.2 Conventional intraoral periapical radiography is an important diagnostic tool in endodontics for assessing the canal configuration. Nevertheless, it is not completely reliable owing to its inherent limitations. Recently newer diagnostic methods, such as computed tomography, have been valuable in overcoming the disadvantages of conventional radiography by producing a three-dimensional image and have emerged as a powerful tool for the evaluation of root canal morphology.22

Tachibana and Matsumoto studied the applicability of computerised tomography to endodontics. They concluded that this method allowed the observation of the morphology of the root canals, the roots and the appearance of the tooth in every direction.

23

CBCT is an accurate, noninvasive, and practical method to reliably compare the results of studies relating to gender and bilateral occurrence of permanent three-rooted mandibular first molars among different ethnic groups. It offers relatively high resolution, isotropic images for effective evaluation of root canal morphology. CBCT images can also reveal the true nature of the tooth structures in 3 dimensions and allow for reliable angulation and distance estimates.

24

 
 
Conclusion

Clinicians should be aware of the morphological variations of the tooth like additional roots, root canals and their incidence. The morphological variations of the radix entomolaris and paramolaris in terms of root inclination and root canal curvature demand careful, adapted clinical approach to avoid procedural errors during endodontic therapy. Careful interpretation of the radiograph, using different horizontal cone projections and advanced tools such as CBCT, may facilitate their recognition.

References
  1. Calberson FL, De Moor RJ, Deroose CA. The radix entomolaris and paramolaris: clinical approach in endodontics. J Endod. 2007;33(1):58-63.
  2. De Moor RJ, Deroose CA, Calberson FL. The radix entomolaris in mandibular first molars: an endodontic challenge. Int Endod J. 2004;37(11):789-99.
  3. Song JS, Choi HJ, Jung IY, Jung HS, Kim SO. The prevalence and morphologic classification of distolingual roots in the mandibular molars in a Korean population. J Endod. 2010;36(4):653-7.
  4. Attam K, Nawal RR, Utneja S, Talwar S. Radix entomolaris in mandibular first molars in Indian population: a review and case reports. Case Rep Dent. 2012;2012:595494.
  5. Kırzıoglu Z, Karayılmaz H, Baykal B. Value of Computed Tomography (CT) in Imaging the Morbidity of Submerged Molars: A Case Report. Eur J Dent. 2007;1(4):246-50.
  6. Sperber GH, Moreau JL. Study of the number of roots and canals in Senegalese first permanent mandibular molars. Int Endod J. 1998;31(2):117-22.
  7. Tratman EK. Three-rooted lower molars in man and their racial distribution. Br Dent J. 1938;64:264-74.
  8. Walker T, Quakenbush LE. Three rooted lower first permanent molars in Hong Kong Chinese. Br Dent J. 1985;159:298-9.
  9. Tu MG, Tsai CC, Jou MJ, Chen WL, Chang YF, Chen SY, Cheng HW. Prevalence of three-rooted mandibular first molars among Taiwanese individuals. J Endod. 2007;33:1163–6.
  10. Yew SC, Chan K. A retrospective study of endodontically treated mandibular first molars in a Chinese population. J Endod. 1993;19(9):471-3.

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