Clinical Research

Prevalence of Three-rooted Mandibular Permanent FirstMolars among the Indian PopulationAmit Kumar Garg, BDS (Lko), MDS (Lko),* Rajendra K. Tewari, BDS (Lko), MDS (Lko),*

Ashok Kumar, BDS (Lko), MDS (Lko),* Sarwat H. Hashmi, BDS (Lko), MDS (Lko),†

Neha Agrawal,‡ and Surendra K. Mishra, BDS (Lko), MDS (Lko)*

Abstract

Introduction: The aim of this retrospective study wasto determine the prevalence of three-rooted mandibularpermanent first molars among the Indian population byusing periapical radiographs. Methods: Five hundredeighty-six patients (320 females and 266 males) wereselected, with at least 1 mandibular first molar. A totalof 1054 periapical radiographs of mandibular firstmolars, comprising 526 right side and 528 left side,were included. The radiographs were taken at 30-degree mesial angulation and were evaluated by usingthe magnifying lens. The incidence, gender, andsymmetry of three-rooted mandibular first molars wererecorded and analyzed by using the c2 test. Results:The prevalence of three-rooted mandibular first molarswas 5.97% for all patients and 4.55% for all teeth,respectively. The incidence of bilateral symmetricaldistribution was 37.14%. The incidence was 6.88% forfemale patients and 4.89% for male patients (c2 =1.02, P > .05) and 4.94% for the right side and 4.17%for the left side, respectively (c2 = 0.36, P > .05). Nostatistically significant differences were found betweenfemale and male patients and between the right-sideand left-side occurrences. Conclusions: Cliniciansshould be aware of the high racial prevalence of thisunusual root morphology in mandibular first molarsamong the Indian population before and during theroot canal treatment of three-rooted mandibular firstmolars. (J Endod 2010;36:1302–1306)

Key WordsRadix entomolaris, radix paramolaris, supernumeraryroot, three-rooted mandibular first molars

From the *Department of Conservative Dentistry andEndodontics and †Department of Oral and MaxillofacialSurgery, Dr. Z. A. Dental College, Aligarh Muslim University, Ali-garh (U.P.), India; and ‡Department of Preventive and Commu-nity Dentistry, M. S. Ramaiah Dental College and Hospital,Bangalore (Karnataka), India.

Address requests for reprints to Dr Amit Kumar Garg, Assis-tant Professor, Department of Conservative Dentistry andEndodontics, Dr. Z. A. Dental College, Aligarh Muslim Univer-sity, Aligarh 202002 (U.P.), India. E-mail address:amit_kgdu@rediffmail.com.0099-2399/$0 - see front matter

Copyright ª 2010 American Association of Endodontists.doi:10.1016/j.joen.2010.04.019

1302 Garg et al.

The main objective of root canal treatment is thorough mechanical and chemicaldebridement of all root canals and their complete obturation with an inert filling

material and a coronal filling, preventing the ingress of microorganisms (1). One ofthe main reasons for the failure of root canal treatment is the inadequate removal ofpulp tissue and microorganisms from the root canal system. Root canal anatomy andthe confounding nature of the human pulpal system pose significant challenges inrendering endodontic treatment. Therefore, it is imperative that the aberrant anatomyis identified before and during the root canal treatment of three-rooted mandibular firstmolars.

It is known that mandibular first molars might display several anatomical varia-tions, because the number of root canals and number of roots might also vary (2).The major variant in this tooth is the presence of a supernumerary root that can be founddistolingually. This macrostructure, first mentioned by Carabelli, is called radix entomo-laris (RE) (3). An RE can be found in the first, second, and third mandibular molars,occurring the least frequently in the second molar (4). An additional root at the mesio-buccal side is called radix paramolaris (RP). The RE mostly has Vertucci type I canalconfiguration (5). The RE, which in general is smaller than distobuccal and mesialroots, can be separate from or partially fused with these other roots (6, 7). De Mooret al (1) have classified the RE into 3 types according to the buccolingual variations;type I refers to a straight root, type II to an initially curved entrance that continues asa straight root, and type III to an initial curve in the coronal third of the root canal, fol-lowed by a second curve beginning in the middle and continuing to the apical third (1).

This supernumerary root in the mandibular first molar is associated with certainethnic groups as follows: European, 3.4%–4.2% (8–11); African, 3% (12); Eurasianand Indian, less than 5% (13); Europeans, 4.2% (1, 6, 14); Asians, such as Chinese,Eskimo, and American Indians have 5% to more than 30% (15–18), and the overallincidence in German patients was 1.35% (19), and among Taiwanese it was about21% (20) (Table1). Because of its high frequency in mongoloid populations, the REis considered to be a normal morphologic variant or eumorphic root morphology(6) and can be seen as the Asiatic trait (16). Among Caucasians, RE is not very common(21, 22) and is considered to be an unusual or dysmorphic root morphology.

In dysmorphic supernumerary root, its root formation is related to external factorsduring odontogenesis (6) or is due to penetration of atavistic gene or polygenic system(6, 17). In eumorphic roots, racial genetic factors influence the profound expression ofa particular gene that results in a more profound phenotypic expression (6). Midtbøand Halse (23) concluded that X chromosome deficiency influences root formation.

To the best of our knowledge few studies such as ours have been undertaken in thecontext of the Indian population. This retrospective study was done to evaluate the inci-dence of three-rooted mandibular permanent first molars, their gender and side-related differences among the Indian population, by using periapical radiographs.The results should be of interest to clinical dentists, dental morphologists, and dentalanthropologists.

Materials and MethodsA total of 586 patients’ retrospective periapical radiographs recorded in the

Department of Oral Medicine and Radiology, Dr. Z. A. Dental College, Aligarh Muslim

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TABLE 1. Survey of Available Studies by Extracted Teeth and Periapical Radiographs on the Prevalence of Three-rooted Mandibular First Molars

Periapical radiographs

No. of teeth/person 3% RM1

Authors Year Area of origin Sample Gender(M/F) 3% RM1 Gender(M/F) Right Left Bilateral Total

Tratman (13) 1938 Chinese 1615 5.80Malay 475 8.60Javanese 110 10.9Indians* 453 0.20Eurasians 262 4.20Japanese 168 1.20

Laband (24) 1941 Malaysian 134 8.20Somogyl-Csizmazia and Simons (25) 1971 Canadian Indians† 250 15.6Souza-Freitas et al (9) 1971 European descent 422 3.20Skidmore and Bjorndahl (10) 1971 White 45 2.2

Japanese descent 233 135/98 17.8 1.65/1 9.87 12.88 22.75Turner (26) 1971 Aleutian Eskimo 263 32.0

American Indians† 1983 5.80Curzon and Curzon (15) 1971 Keewatin Eskimo 98 27.0Curzon (27) 1974 Baffin Eskimo 69 21.7Hochstetter (28) 1975 Guam 400 14.3 2/1Jones (29) 1980 Chinese 52 13.4

Malaysian 149 16.0Reichart and Metah (17) 1981 Thai 364 19.2Walker and Quackenbush(18) 1985 Hong Kong Chinese 213 14.6Steelman (11) 1986 Hispanic children 156 73/83 1.50/1 2.60 0.60 3.20 6.40Walker (30) 1988 Hong Kong Chinese 100 15.0Harada et al(31) 1989 Japanese 2331 18.8Loh (14) 1990 Singaporean Chinese 304 7.9Ferraz and Pecora (22) 1992 Japanese descent 105 1/1 11.4

Negro 106 2.80White 117 4.20

Yew and Chan (16) 1993 Chinese 179 21.5Gulabivala (32) 2001 Burmese 139 10.1Gulabivala (33) 2002 Thai 118 13.0Huang et al (34) 2007 Taiwanese 332 21.7 26.9Tu et al (20) 2007 Taiwanese 332 79/87 17.77 0.75 4.22 2.41 14.46 21.09Schafer et al (19) 2009 Germans 524 264/260 0.68 1.33 0.57 0.76 1.34

3% RM1, % of 3-rooted mandibular 1st molars.

*Indian subcontinent.†Native American Indians.

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TABLE 2. Number and Percentage of Three-rooted Mandibular First Molars

No. of three-rooted mandibular first molars

Right Left Bilateral Total

No. of patients and teeth No. % No. % No. % No. %

Female 320 10 3.13 6 1.88 6 1.88 22 6.88Male 266 3 1.13 3 1.13 7 2.63 13 4.89Total patients 586 13 2.22 9 1.54 13 2.22 35 5.97No. of all right first molars examined 526 13 2.47 — — 13 2.47 26 4.94No. of all left first molars examined 528 — — 9 1.71 13 2.46 22 4.17Total teeth 1054 13 1.23 9 0.85 26 2.47 48 4.55

Clinical Research

University, Aligarh, India from December 2008–December 2009 werescreened and examined. The bilateral eccentric periapical radiographs(30-degree mesial angulation with protractor) of patients who visitedthe Department of Conservative Dentistry and Endodontics for treatmentof either pain or caries in the mandibular molars were obtained. Each ofthese patients had at least 1 mandibular first molar and was of Indianorigin. Demographic details including age, sex, and race of all thesepatients were recorded.

The x-ray machine used for tooth identification was EndosAC (VillaSistemi Medicali Spa, Buccinasco, Italy) (70 kV and 8 mA). Periapicalradiographs were taken with Kodak Ultraspeed films (Eastman Kodak

Figure 1. Periapical radiographs of three-rooted mandibular first molars showingon the left side unilaterally, (C) the mesiobuccal root on the right side unilaterally

1304 Garg et al.

Ultra-speed film; Kodak, Rochester, NY). A total of 1054 periapicalradiographs of mandibular first molars of 586 patients (320 femalesand 266 males) were selected for the study. The radiographs wereplaced on a viewing box, and the light surrounding the radiographwas blocked. Each radiograph was independently studied by 2 authors(G.A. and T.R.) by using magnifying lens (3�). Any disagreement in theinterpretation of images was discussed by 2 endodontists, anda consensus was reached (19, 20). The criteria for the indication ofan extra root were justified by crossing the translucent lines, definingthe pulp space and the periodontal ligaments in the mandibular firstmolars (18–20). The overall incidence of three-rooted mandibular first

(A) the distolingual root on the right side unilaterally, (B) the distolingual root, and (D) the mesiobuccal root on the left side unilaterally.

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Clinical Research

molars in the patients and their correlations between female and malepatients and between the right-side and left-side occurrences wereanalyzed by using the c2 test (19, 20). The bilateral incidence ofthese three-rooted mandibular first molars was also evaluated.

ResultsPeriapical radiographs of 586 patients, 320 females and 266

males, with age range of 15–75 years and average age of 30.3 �12.5 years, were studied. The periapical radiographs of 35 patients,22 females and 13 males, had three-rooted mandibular first molars.A total of 1054 periapical radiographs of mandibular first molarscomprising 526 right and 528 left molars were evaluated (Table 2).Of these three-rooted mandibular first molars, 26 were found on theright side and 22 on the left side. The prevalence of patients withthree-rooted mandibular first molar was 5.97% (35 of 586 patients),6.88% (22 of 320) for female patients and 4.89% (13 of 266) formale patients (Table 2). The prevalence of three-rooted mandibularfirst molars from all teeth examined was 4.55% (48 of 1054), 4.94%(26 of 526) for the right side and 4.17%(22 of 528) for the left sideoccurrences (Table 2). There was no statistical significant differencein the incidence of three-rooted mandibular first molars betweenfemale and male patients (c2 = 1.02, P > .05) and between theright-side and left-side occurrences (c2 = 0.36, P > .05) (Table 2,Fig. 1). The bilateral incidence of symmetrical distribution was 37.14%.

DiscussionIn the present study, the prevalence of three-rooted mandibular

first molars among the Indian population was 5.97% of all patientsand 4.55% of all teeth examined (Table 2). This figure is higher thanthe result of the study by Tratman (13) (0.20%) among Asiatic Indiansand similar to the result of the study by Turner (26) (5.8%) amongAmerican Indians and less than the study by Somogyl-Csizmazia andSimons (25) among Canadian Indians (15.6%) (Table1). In this study,there was no significant difference according to gender (P > .05),which is similar to the recent studies (19, 20). There was also nosignificant difference according to the side occurrence (right versusleft side, P > .05), which was also similar to the recent study (19).However, some studies reported that three-rooted mandibular firstmolars occurred more frequently on the right side than on the leftside (11, 20), whereas there are also studies showing that thesethree-rooted mandibular first molars occurred more frequently onthe left side (21, 32).

The bilateral occurrence of three-rooted mandibular first molarswas 37.14% (13 of 35), which was more than the recent study (19)among the German population (0%) and lower than several studieson the Asiatic descent population (56.6%–67%) (9, 11, 16, 18, 20).These contradictory variations might be explained by markeddifferences in the sample size, case selection, and the methods used.Thus, further investigations are necessary to clarify the issue. Acomparison of the previous reports is presented in Table 1.

There have been several studies of extracted permanent mandib-ular first molars (13–15, 22, 29, 32, 33), but it is impossible tocompare the results of these studies related to gender and bilateraloccurrences. The present noninvasive study used 2-dimensionalimages (periapical radiographs) of patients’ mandibular first molaras a tool for studies related to gender and side-related differences.

The presence of RE has clinical implications in endodontic treat-ment. An accurate diagnosis of these supernumerary roots can avoidcomplications or missing a canal during the root canal treatment(34). Apart from complicating the root canal procedure, RE hasbeen found to be a contributing factor to localized periodontal destruc-

JOE — Volume 36, Number 8, August 2010 Prevalence of Three

tion (35). In addition, reports correlate significantly higher probingdepths with attachment loss at the distolingual aspect of three-rootedmolars (2, 35).

According to Walker and Quackenbush (18), normally a thirdroot should readily be evident in about 90% of cases radiographically,but occasionally it might be difficult to see because of its slender dimen-sions. In addition, a file placed in such a root might give an artifactualappearance of a perforation. In such instances, an angled view (verti-cally and horizontally) is always beneficial (25). With the distolinguallylocated orifice of RE, a modification of the classic triangular openingcavity to a trapezoidal form to locate and access the root canal betteris essential; the straight line access must be established (1, 6).

ConclusionWith the frequency of occurrence of 5.97% among the Indian pop-

ulation, every possible effort should be made for locating an extra rootin mandibular first molars because it might be useful for successfulendodontic treatment. Clinicians should be aware of the high racialprevalence of this unusual root morphology in mandibular first molarswhile treating Indian patients.

AcknowledgmentsThe authors thank Prof. Aziz Khan (Department of Community

Medicine, AMU, Aligarh) and Prof. A. R. Kidwai (Director, UGCAcademic Staff College, AMU, Aligarh) for their guidance and thetime and effort they devoted to this study.

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