Three-Rooted Mandibular First Molars

ORIGINAL ARTICLE 263

Saurabh S. Chandra, Supriya Chandra Three-rooted mandibular ﬁrst molars – prevalence among an Indian population

Saurabh S. Chandra, MDS Assistant Professor, Department of Conservative Key words dental anomalies, mandibular molars, radix entomolaris Dentistry and Endodontics, SDS, Sharda University, Greater Noida, India Aim: This study aims to evaluate the prevalence of three-rooted permanent mandibular first molars Supriya Chandra, in an Indian population. MDS Materials and methods: The intraoral periapical radiographs of 616 patients of Indian ethnicity pos- Senior Lecturer, Department of Periodontology, sessing bilateral mandibular first molars were screened under optimal conditions. A total of 1232 Sree Bankey Bihari Dental mandibular first molars were evaluated, and the prevalence of three-rooted mandibular first molars College, Ghaziabad, India and the correlation between left and right side occurrence and between either gender was recorded. Correspondence to: Dr Saurabh S. Chandra Results: The prevalence of three-rooted mandibular first molar was 16.07% of the patient’s ex- Dept. of Conservative amined and 11.52% of the teeth examined. There was neither a statistically significant difference Dentistry and Endodontics, SDS, Sharda University, amongst the gender nor on the side of occurrence (P > 0.05). The bilateral incidence of a symmetrical Greater Noida, India distribution was 43.43%. Mob: 091-9990525400 Email: saurabhchandra@ Conclusion: Based on the results of the study, the prevalence of this anatomic macrostructure in an yahoo.com Indian population was 11.52%.

Introduction ported in related literature by Carabelli in 1844, and termed ‘radix entomolaris’ (RE)2. Rarely, a third root The principal objective of endodontic treatment may be found on the mesiobuccal side and is called comprises of meticulous cleaning and shaping of the ‘radix paramolaris’3. The RE can be found on the root canal system followed by a three-dimensional first, second and third mandibular molar, occurring obturation. The inability to identify and locate ad- least frequently on the second molar4. Studies have ditional roots and canals often leads to treatment shown that this supernumerary root can be separate failure. Clinicians must have a sound knowledge of from or partially fused to other roots. It is typically anatomical variations and must carefully evaluate smaller than the mesial and distobuccal roots and is radiographs prior to initiation of root canal therapy. usually curved, requiring special attention when en- As the earliest permanent posterior tooth to erupt, dodontic intervention is considered2-3,5,6. The coronal the mandibular first molar is considered to be the one part of RE is completely or partially fixed to the distal most frequently involved tooth in endodontic pro- root and its dimension can vary from short conical cedures. It displays considerable anatomic variation to a root of normal length and root canal3. Carlsen and abnormalities regarding the number of roots and and Alexandresen5 described four different types of root canals1. Mandibular molars featuring an addi- RE while De Moor et al6 suggested a classification tional distolingually located third root were first re- with three different types of RE; Type I refers to a

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Table 1 Literature review on the prevalence of three-rooted mandibular first molars in straight root, Type II to an initially curved entrance different populations. that continues as a straight root, and Type III to an initial curve in the coronal third of the root canal and Author Year Population /Ethnic Group a second curve beginning in the middle and continu- Percentage of RE (%) ing to the apical third. Huang et al found a higher magnitude of periodontal and clinical attachment Taylor35 1899 United Kingdom 3.4 Bolk36 1915 Dutch 1.1 loss at the distolingual site of molars that presented Tratman11 1938 Chinese 5.8 with three roots, as compared to molars with two 7 Tratman11 1938 Eurasian 4.2 roots . Although the exact aetiology is unclear, the Tratman11 1938 Malaysian 8.6 unique morphological features of the distolingual Tratman11 1938 Japanese 1.2 root may lead to increased pocket depth leading to Laband12 1941 Malayans 8.2 serious periodontal destruction. Evidence suggests Harada et al37 1969 Japanese 18.8 that the presence of the RE contributes to the for- Skidmore et al38 1971 Caucasian 2.2 mation of distal furcation, which can be complex. Turner14 1971 Aleutian Eskimo 32 A review of the relevant endodontic literature Curzon et al15 1971 Keewatin Eskimo 27 revealed that the prevalence of three-rooted man- 14 Turner 1971 American Indian 5.8 dibular molars has a genetic and ethnic predilection 13 1971 Canadian Indian 15.6 Somogyl-Csizmazia (Table 1). It is seldom found in European, Caucasian De Souza - Freitas et al32 1971 Japanese 17.8 and African populations, but appears to be more De Souza - Freitas et al32 1971 European 3.2 common in races of Mongoloid origin. In these Curzon10 1974 Baffin Eskimo 21.7 populations, RE is regarded as a normal racial and Hochstetter16 1975 Guam 14.3 morphological variation rather than as an abnormal- Jones17 1980 Chinese 13.4 Jones17 1980 Malaysian 16 ity and can be seen as an Asiatic trait. Virtually, all Reichart et al8 1981 Thai 19.2 reports focused on the actual occurrence of three- Walker and 1985 Hong Kong Chinese 14.6 rooted mandibular first molars based simply on the Quackenbush18 extracted teeth that were examined for different 31 Steelman 1986 Hispanic 6.4 races of individuals8-28. 19 1988 Hong Kong Chinese 15 Walker The aim of this study was to investigate the fre- 39 1989 Japan (Hindu) 1 Onda et al quency of occurrence of three-rooted permanent Loh20 1990 Singaporean Chinese 7.9 mandibular first molars in an Indian population using Younes et al40 1990 Egyptian 0.7 digital intraoral periapical radiographs (IOPA). Younes et al40 1990 Saudi Arabia 2.3 Ferraz et al41 1993 Japanese 11.4 Ferraz et al41 1993 Brazilian 4.2 Yew et al30 1993 Chinese 21.5 Materials and methods Suarez-Feito42 1995 Spanish 0 Rocha et al43 1996 Brazil 5.2 A group of patients between the age group of 18– Zaatar et al44 1998 Kuwait 0 72 years were evaluated for the presence of ‘three- Sperber & Moreau45 1998 Senegal 3.1 rooted’ mandibular first molars. This investigation was Al-Nazhan46 1999 Saudi Arabia 6 done at the Department of Conservative Dentistry Gulabivala et al21 2001 Burmese 10.1 and Endodontics, School of Dental Sciences, Sharda Gulabivala et al22 2002 Thai 12.7 University, Greater Noida, India between June 2010 Tu et al24 2007 Taiwanese 17.8 and May 2011. A total of 616 patients (348 males and 47 Ahmed et al 2007 Sudanese 3 268 females) with bilateral permanent mandibular first 48 2007 Unspecific 53.7 Furri et al molars (1,232 mandibular first molars) were consid- Huang et al7 2007 Taiwanese 21.7 ered in the study. The patients were informed about 49 2008 Sri Lankan 3 Peiris et al the study design and a written consent was obtained. Reuben et al50 2008 Indian 0 Ethical clearance was obtained both from the Ethical 51 Pattanshetti et al 2008 Kuwaiti & Non Kuwaiti 3.6 review board committee of SDS, Sharda University,

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Greater Noida. Personal details of each patient includ- Table 1 (cont.) Literature review on the prevalence of three-rooted mandibular first molars in different populations. ing age, sex and ethnicity were recorded. The criteria for subject selection were the following: Author Year Population /Ethnic Group i Each subject had to have fully erupted perma- Percentage nent mandibular first molars bilaterally. of RE (%) 33 2009 German 0.68 ii Subject had to be of Indian origin. Schäfer et al Al-Qudah & Awawdeh52 2009 Jordanian 3.9 iii The permanent mandibular first molars had to have Chen et al53 2009 Taiwanese 19.7 fully formed apexes with no root canal fillings. Rwenyonyi et al54 2009 Uganda 0 Chen et al53 2009 Taiwanese 9.9 Each patient was digitally radiographed using the Chen et al53 2009 Taiwanese 19.7 Satelec RVG (Acteon; Bordeaux, France) system and Tu et al55 2009 Taiwanese 25.6 examined using the SOPIX imaging software (Ac- Garg et al27 2010 Indian 5.97 teon). Two periapical radiographs were taken from Gu et al56 2010 Chinese 32 two different horizontal angles; one taken in ortho- Huang et al57 2010 Taiwanese 25.3 radial position and the other taken 30 degrees mesi- Song et al58 2010 Korean 24.5 ally. The stored digital radiographs were displayed Chandra et al28 2011 South Indian 13.3 on a 17-inch LCD monitor (LG Electronics, Seoul, South Korea) and investigated for the presence of a third root by two authors. Disagreement in the interpretation of images was discussed between the two total number of 1,232 permanent mandibular first clinicians until a consensus was reached. The criteria molars were evaluated. The occurrence of three for the indication of an extra root were adopted from roots in the mandibular first molar was 14.4% recent studies18,24-26 and the presence of an extra (50/348 patients) for men and 18.3% (49/268 pa- root was justified by the crossing of the translucent tients) for women. No statistical gender-related dif- lines defining the pulp space and periodontal liga- ference was found for the incidence of three-rooted ment in the mandibular first molars. mandibular first molars by a binary logistic regres- Disagreement in the interpretation of radio- sion test (P > 0.05). Overall, the incidence of pa- graphs was discussed between the two investiga- tients who presented with such teeth was 16.07% tors until a consensus was arrived upon (Figs 1 to (99/616 patients) and 11.52% (142/1232) of the 4). The total prevalence of three-rooted mandibular teeth examined. Table 2 shows tabulated results first molars and the ratio of the occurrence in gen- individually for both males and females, as well as der of such teeth were assessed. The prevalence of collectively. There was no statistical difference seen the bilateral and unilateral appearance of such teeth in the side of occurrence of the three-rooted man- and the comparison of right- to left-side occurrence dibular first molar (P > 0.05). Subsequently, it was of these three-rooted mandibular first permanent inferred that 43.43% (43/99) of the three-rooted molars were also estimated. Comparison of the oc- mandibular first molars occurred bilaterally. currence of such three-rooted mandibular first molars according to gender was analysed by means of a binary logistic regression test and the correlation Discussion between left- and right-side occurrences were de- termined by the Pearson Chi-square test. The study of root canal anatomy is important for dental practice and has immense anthropologic sig- nificance25. The aetiology behind the formation of a Results third root is unclear. In dysmorphic, supernumerary roots, its formation can be related to external factors The intraoral periapical radiographs of 616 patients during odontogenesis or to penetrance of an atavis- (348 males and 268 females) with an average age tic gene or polygenetic system3. In eumorphic roots, of 37.7 + 4.7 years were screened in this study. A racial genetic factors influence the more profound

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Fig 1 Three-rooted mandibular left ﬁrst molar. Fig 2 Three-rooted mandibular left ﬁrst molar.

Fig 3 Postoperative radiograph of a right three- Fig 4 Postoperative radiograph of a left three-rooted man- rooted mandibular ﬁrst molar. dibular ﬁrst molar.

Table 2 Results showing the percentage of three-rooted permanent mandibular ﬁrst molars.

No. of Unilateral Bilateral Total patients Left Right No. % No. % No. % No % Male 348 15 4.3 11 3.2 24 6.9 50 14.4 Female 268 16 6.0 14 5.2 19 7.08 49 18.3 Total 616 31 5.03 25 4.05 43 6.9 99 16.07 Total no. of teeth examined 1232 31 2.5 25 2.02 86 6.9 142 11.52

expression of a particular gene that results in the in Eurasian and Indian populations the frequency more pronounced phenotypic manifestation8,9. is less than 5%11. In populations with Mongoloid Curzon suggested that the “three rooted molar” traits (Malay, Chinese, Eskimo and American Indi- trait has a high degree of genetic penetrance as ans) the frequency of occurrence has been 5% to its dominance was reﬂected in the fact that the 40%6,11. prevalence of the trait was similar in both pure According to the results obtained from this inves- Eskimo and Eskimo/Caucasian mixes10. In African tigation, the occurrence of the third root was found populations a maximum of 3% is found3,6, while to be 16.07% (99/616) of all patients examined

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and 11.52% (142/1232) of all the teeth examined. ing canal morphology in vivo. Nevertheless, these This macrostructure has been particularly an Asi- radiographs are not completely reliable because of atic trait and its prevalence has been reported to inherent limitations such as the distortion and the be 1.2% to 21.5%. Turner reported the prevalence super-imposition of dental structures that can occur of RE in American Indians to be 5.8% while Somo- in the images taken. This certainly is a limitation in gyl-Csizmazia reported a 15.6% prevalence rate in evaluating extra roots; therefore two or more peri- Canadian Indians13,14. Garg et al examined 586 pa- apical radiographs taken at two different horizontal tients of Indian origin and reported the prevalence of angulations are recommended for proper identifica- three-rooted mandibular molars to be 5.97%27. The tion of three-rooted mandibular molars. The Buccal significant difference between these results could object rule with two radiographs and different hori- be due to the methodology. Two radiographs (one zontal angulations may be sufficient to determine each in orthoradial position and at 30 degree mesial the position of a lingual root. shift) were taken in the present study. Studies have Although 0 to 20 degree angulations have been shown that angled radiographs reveal more details suggested, a 30 degree mesial horizontal beam an- about the root anatomy and root canal morphology, gulation was recommended to provide additional which may be missed or not seen in orthoradial ra- details of the root canal anatomical configuration diographs due to overlapping of structures1. Chan- of mandibular first molars in in vitro and clinical dra et al reported the prevalence of RE in South evaluations1. Nevertheless, according to Walker and Indian population to be 13.3%, where both con- Quackenbush, the accuracy of a correct diagnosis of ventional radiograph films and digital radiographs three-rooted mandibular molars is about 90% even were used28. However the results obtained from the when using only panoramic radiographs18. In the present study showed a lower prevalence rate than present study, digital periapical radiograph images that found in people of Thai, Japanese, Taiwanese were investigated. The replacement of traditional and Chinese descent. Pablo et al in a systematic re- radiography with digital radiography offers many view on mandibular molars reported an overall 13% advantages. prevalence of mandibular with three roots and this Researchers have concluded that digital sensors feature was strongly related to the ethnicity of the equal analogue film for diagnostic tasks with the studied population29. added benefits of instantaneous image acquisition, The prevalence of the third root in mandibular image feature enhancement, magnification of spe- molars according to either gender did not appear cific areas and increased security of offsite archiv- to show any statistical significance in the present ing34. Conventional film provides a finer grade of study. There was no significant difference accord- detail through continuous shades of greyscale im- ing to the side of occurrence. Some authors have ages, rather than the discrete pixels of individual reported that this anatomic variation occurred fre- grey levels used by digital systems. However, with quently on the right side24,26, while others reported advances in digital imaging, such as improved reso- that it is seen on the left21,23. Some studies reported lution, enhanced digital subtraction radiography and a bilateral occurrence of the three-rooted man- active surfaces approaching those of film, the digital dibular molars from 50% to 69%18,24,30-32. Schäfer image quality may surpass that of film34. et al failed to find any bilateral occurrence in their study of 1024 mandibular first molars in a German population33. Conclusion In previous studies, there have been two main methods used to assess the prevalence of this an- The results of this study corroborate an 11.52% atomic macrostructure. Some authors studied this prevalence of mandibular first molars presenting aberration directly from extracted teeth11,15,17,20-22 with three roots in an Indian population, thus war- while others have chosen a radiographic ap- ranting comprehensive radiological assessment pre- proach13,16,18,24,27,28,33. Conventional intraoral peri- ceding endodontic treatment. apical radiographs are an important tool for assess-

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