Clinical Research
Prevalence of 3- and 4-rooted First and Second Mandibular Molars in the Israeli Population Avi Shemesh, DMD,* Avi Levin, DMD,* Vered Katzenell, DMD,* Joe Ben Itzhak, DMD,* Oleg Levinson, DMD,† Avraham Zini, PhD, DMD, MPH,‡ and Michael Solomonov, DMD* Abstract Introduction: Three-rooted mandibular molars are 1 of the anatomic variations of mandibular molars. The location of the additional root is distolingual (radix entomolaris) or mesiobuccal (radix paramolaris). The purpose of this retrospective study was to assess the prevalence of 3- and 4-rooted mandibular first and second molars in the Israeli population and to classify them according to dimension, curvature, and location of separation from the main root. Methods: A total of 1020 Israel patients’ cone-beam computed tomographic scans were screened and evaluated. The incidence of 3- and 4-rooted first and second mandibular molars were recorded and analyzed. One thousand four hundred sixty-five mandibular second molars and 1,229 mandibular first molars were evaluated. Results: The overall incidence of patients with 3-rooted mandibular first and second molars was 2.6% and 1.78%, respectively. The bilateral incidence of 3-rooted mandibular first and second molars was 26%. The incidence of 4-rooted mandibular second molar was 0.55%. No significant difference was found regarding sex or side of occurrence. Conclusions: The occurrence of 3-rooted mandibular first molars in the Israeli population was rare, but clinicians should be aware of the special characteristic of this anatomic variation to modify accordingly the form of pulp chamber opening and choose appropriate instrumentation. (J Endod 2015;41:338–342)
Key Words Cone-beam computed tomographic imaging, mandibular molar, radix entomolaris, radix paramolaris
From the *Department of Endodontics, Israel Defense Forces Medical Corps, Tel Hashomer, Israel; †Private Practice, Tel-Aviv, Israel; and ‡Department of Community Dentistry, Hebrew University-Hadassah School of Dental Medicine, Jerusalem, Israel. Address requests for reprints to Dr Avi Shemesh, Department of Endodontics, Israel Defense Forces Medical Corps, Tel Hashomer, Israel. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2014.11.006
338
Shemesh et al.
T
he basis of root canal treatment is a procedure of cleaning, shaping, and obturation (1). Knowledge of root anatomy and canal morphology is essential for successful endodontic treatment (2). The first and second mandibular molars are usually 2 rooted: 1 mesial root and 1 distal root (2). One of the anatomic variations of mandibular molars is an additional root, which was first mentioned in the literature by Carabelli (3) and called radix entomolaris in the distolingual location or radix paramolaris in the mesiobuccal location (4, 5). This variation is well documented in the literature, but most publications deal with first molars with 3 roots. The additional root can be classified by curvature, dimension, and point of separation from the main root (4, 6). The frequency of an additional root in the first mandibular molar is up to 32% in Eskimos, 30% in Chinese, and 18.8% in Japanese. In the European population, a maximum frequency of 3.4%–4.2% has been found (7–13). The frequency of an additional root in the second mandibular molar is up to 3.5% in Brazilians, 1.9% in whites, and 25.8% in Koreans (14–16). Cone-beam computed tomographic (CBCT) imaging is a 3-dimensional (3D) imaging technique that can be useful for diagnosing irregular anatomy (17, 18). Recently, CBCT imaging has been found to be useful and accurate in assessing root canal morphology. CBCT scanning is a noninvasive method that provides for axial and cross-sectional observation of each tooth and makes it easier to diagnose additional roots (19–23). The purpose of the study was to investigate the prevalence of additional roots in the first and second mandibular molars in the Israeli population and to classify them by dimension, curvature, and point of separation from the main root.
Materials and Methods The study was approved by the Ethics Committee of Medical Corps, Israeli Defense Forces (IDF-1258). A total of 1020 patients’ retrospective dental CBCT (Alioth; Asahi Roentgen IND, Kyoto, Japan) records, which had already been recorded in an x-ray institute in Israel from 2009 to 2012, were examined. The patients (447 males and 573 females) were referred to this institute and required a tomographic examination by CBCT imaging as part of their dental examination, diagnosis, and treatment planning. The CBCT images were taken using the ASAHI Alioth CBCT device at 360 x-ray tube head rotation. All CBCT scans were reformatted to standard manufacturer settings; the exposure parameters of each scan were as follows: constant tube voltage of 85 kV, tube current of 6 mA, and field of view of 80 80 mm with a resolution of 0.155 0.155 0.154999 mm. CBCT exposures were performed with the minimum exposure necessary for adequate image quality. Personal details including age and sex of all these patients were recorded. The CBCT images were analyzed with OnDemand3D software (CyberMed, Irvine, CA) in a darkroom. The contrast and brightness of the images were adjusted using the image processing tool in the software to ensure optimal visualization. CBCT images were evaluated by 2 graduate endodontic residents who were calibrated based on the criteria and variants established before their evaluation. CBCT images were analyzed simultaneously to reach a consensus for the interpretation of the radiographic findings. In cases of
JOE — Volume 41, Number 3, March 2015
Clinical Research disagreement, a third, definitive evaluation was conducted by an endodontist with 10 years of experience who was calibrated based on the same criteria and variants. First and second mandibular molars were analyzed using 3 planes (sagittal, axial, and coronal) slices (Fig. 1A and B), and additional roots were classified as follows (Fig. 2A–F): 1. Curvature, straight or curved root 2. Dimension, shorter and conical or normal length compared with other roots 3. Point of separation from the main root, cervical or apical In cases of disagreement, a third, determinate valuation was conducted by an endodontist with 10 years of experience. The reviewers were calibrated on the basis of the criteria and variants established before their evaluation. The Pearson chi-square test was applied to examine any statistically significant difference between sex and the side of occurrence. A P value .05) or side of occurrence (left vs right side, P > .05) (Table 1). Table 2 indicates that 26% (12/46 patients) of the 3-rooted mandibular first molars occurred bilaterally, and all cases of 4-rooted mandibular molars are unilateral (Fig. 4). One of the patients has radix paramolaris in all 4 mandibular molars. Analysis of the 3-rooted mandibular first molars revealed (Table 3) the following:
1. Most of the radix entomolaris roots are curved roots (18/25) with the same length as the main root (17/25) and the point of separation is in the cervical third of the root (23/25). 2. All of the radix paramolaris roots are straight roots (7/7) and have the same length as the main root (7/7). Analysis of the 3-rooted mandibular second molars (Table 3) revealed that most of the radix paramolaris roots are of the same length as the main root (18/20).
Discussion An additional root in mandibular molars is 1 of the anatomic variations of these teeth. The presence of additional roots in mandibular molars is associated with certain ethnic groups (7–16). According to the present results, the occurrence of radix entomolaris roots in mandibular first and second molars in the Israeli population was 2.03% and 0.41% of all teeth examined, respectively. The occurrence of radix paramolaris roots in mandibular first and second molars in the Israeli population was 0.57% and 1.37% of all teeth examined, respectively. This finding is in agreement with a previous report on Europeans but is lower compared with data reported for non-European races (7–16). In the present study, no significant difference was found according to sex or the side of occurrence. However, other studies reported that 3-rooted mandibular first molars occurred more frequently on the right or left side (11, 12, 17, 24, 25). Zhang et al (13) analyzed 232 mandibular first molars and 157 mandibular second molars, and they found one 4-rooted mandibular first molar. In the present study, we found 8 mandibular second molars with 4 roots. Identifying the additional root is critical for successful treatment. Periapical x-rays are 2-dimensional, and the additional root might be hidden behind the main root, especially if the additional root is short or curved. A second radiograph should be taken from a more mesial or distal angle (30 ) and can be useful for the diagnosis (4, 6). The ultimate examination is CBCT imaging, providing 3D observations of the additional root and its exact relation to the pulp chamber. Knowledge of the additional root’s existence and location leads to correct preparation of the access cavity for locating all canals (26). The conventional triangular opening cavity must be modified to a trapezoidal form in order to locate and access the orifice of the additional root better (6). An extension of the access cavity to the orifice location
Figure 1. CBCT images of a first mandibular molar with a radix entomolaris: (A) cross-sectional slice and (B) axial slice.
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Figure 2. CBCT images of mandibular molars with a radix entomolaris or paramolaris. (A) A second molar with a straight radix entomolaris. (B) A second molar with a curved radix paramolaris. (C) A first molar normal length radix paramolaris. (D) A first molar with a short radix paramolaris. (E) A first molar with radix entomolaris with apical separation. (F) A second molar with radix entomolaris with cervical separation.
of the additional root is necessary in order to avoid complications or a ‘‘missed canal’’ during root canal treatment (4). Our results support previous findings that the additional root morphology is variable (4, 6). Compared with the main root, the 340
Shemesh et al.
additional root can be shorter or more curved. We found that radix entomolaris and radix paramolaris roots are different. For example, radix paramolaris in the first mandibular molar is a straight root with the same length as the main root, and the JOE — Volume 41, Number 3, March 2015
Clinical Research TABLE 1. Analysis of Sex and Side Distribution of 3- and 4-rooted Mandibular Molars in the Israeli Population Radix paramolaris (%)
4-rooted tooth
P value*
10 (40) 15 (60)
6 (85.7) 1 (14.3)
0 0
.209
617 613 1229
14 (56) 11 (44) 25 (2.03)
4 (57.1) 3 (42.9) 7 (0.57)
0 0 0
.753
814 651
5 (83.3) 1 (16.7)
12 (60) 8 (40)
4 (50) 4 (50)
.551
743 722 1465 2694
2 (33.3) 4 (66.7) 6 (0.41) 31
10 (50) 10 (50) 20 (1.37) 27
5 (62.5) 3 (37.5) 8 (0.55) 8
.760
No. of teeth First molar Sex Female Male Side Right Left Total Second molar Sex Female Male Side Right Left Total Total
679 550
Radix entomolaris (%)
*Nonparametric Pearson chi-square test.
Figure 3. CBCT axial images of 4-rooted second mandibular molars.
separation from the main root is apical. Radix entomolaris in the first mandibular molar is usually a curved root with coronal separation. These findings may help the clinician to plan his instrumentation and obturation technique if an additional root is identified during root canal treatment. For example, curvature and radius of curvature are important factors that can lead to instrument breakage, so these data help the clinician choose appropriate instruments for safer shaping (27).
TABLE 2. Analysis of the Distribution of Unilateral and Bilateral Occurrences among 46 Patients with 3-rooted Mandibular Molars: Cases in This Study
First molar Unilateral Bilateral Second molar Unilateral Bilateral
Radix entomolaris (%)
Radix paramolaris (%)
Total
13 (68.4) 6 (31.6)
3 (60) 2 (40)
16 8
2 (50) 2 (50)
16 (88.8) 2 (11.2)
18 4
JOE — Volume 41, Number 3, March 2015
Figure 4. CBCT axial images of bilateral radix entomolaris first mandibular molars.
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Clinical Research TABLE 3. Classification of First and Second 3-rooted Mandibular Molars by Dimension, Curvature, and Point of Separation Curvature
First molar Radix paramolaris Radix entomolaris Total Second molar Radix paramolaris Radix entomolaris Total
Dimension
Total
Straight root
Curved root
Same length
Short length
Cervical separation
Apical separation
7 25 32
7 7 14
0 18 18
7 17 24
0 8 8
0 23 23
7 2 9
20 6 26
19 5 24
1 1 2
18 4 22
2 2 4
12 5 18
8 1 10
Conclusion The incidence of additional roots in mandibular molars in the Israeli population is lower than that of other populations. CBCT data can reveal 3D characteristics of an additional root such as dimension, curvature, and exact location of separation and help the clinician during the opening of the pulp chamber and choosing of appropriate instruments.
Acknowledgments The authors deny any conflicts of interest related to this study.
References 1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18: 269–96. 2. Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol 1984;58:589–99. 3. Carabelli G. Systematisches Handbuch der Zahnheilkunde. 2nd ed. Vienna: Braumuller and Seidel; 1844:114. 4. Calberson FL, De Moor RJ, Deroose CA. The radix entomolaris and paramolaris: clinical approach in endodontics. J Endod 2007;33:58–63. 5. Sperber GH, Moreau JL. Study of the number of roots and canals in Senegalese first permanent mandibular molars. Int Endod J 1998;31:117–22. 6. De Moor RJ, Deroose CA, Calberson FL. The radix entomolaris in mandibular First molars: an endodontic challenge. Int Endod J 2004;37:789–99. 7. Turner CG. Three-rooted mandibular first permanent molars and the question of American Indian origins. Am J Phys Anthropol 1971;34:229–41. 8. Yew SC, Chan K. A retrospective study of endodontically treated mandibular first molars in a Chinese population. J Endod 1983;19:471–3. 9. Harada Y, Tomino S, Ogawa K, et al. Frequency of three-rooted mandibular first molars. Shika Kiso Igakkai Zasshi 1989;3:13–8. 10. Taylor AE. Variations in the human tooth form as met with in isolated teeth. J Anat Physiol 1899;33:268–72. 11. Steelman R. Incidence of an accessory distal root on mandibular first permanent molars in Hispanic children. ASDC J Dent Child 1986;53:122–3. 12. Curzon ME. Three-rooted mandibular permanent molars in English Caucasians. J Dent Res 1973;52:181.
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Point of separation
13. Zhang R, Wang H, Tian Y, et al. Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular molars in Chinese individuals. Int Endod J 2011;44:990–9. 14. Plotino G, Tocci L, Grande NM, et al. Symmetry of root and root canal morphology of maxillary and mandibular molars in a white population: a cone-beam computed tomography study in vivo. J Endod 2013;39:1545–8. 15. Silva EJ, Nejaim Y, Silva AV, et al. Evaluation of root canal configuration of mandibular molars in a Brazilian population by using cone-beam computed tomography: an in vivo study. J Endod 2013;39:849–52. 16. Kim SY, Kim BS, Woo J, Kim Y. Morphology of mandibular first molars analyzed by cone-beam computed tomography in a Korean population: variations in the number of roots and canals. J Endod 2013;39:1516–21. 17. Tu MG, Tsai CC, Jou MJ. Prevalence of three rooted mandibular first molars among Taiwanese individuals. J Endod 2007;33:1163–6. 18. Schafer E, Breuer D, Janzen S. The prevalence of three rooted mandibular permanent first molars in a German population. J Endod 2009;35:202–5. 19. Tsiklakis K, Donta C, Gavala S, et al. Dose reduction in maxillofacial imaging using low dose Cone Beam CT. Eur J Radiol 2005;56:413–7. 20. Zhang R, Yang H, Yu X, et al. Use of CBCT to identify the morphology of maxillary permanent molar teeth in a Chinese subpopulation. Int Endod J 2011;44:162–9. 21. La SH, Jung DH, Kim EC, Min KS. Identification of independent middle mesial canal in mandibular first molar using cone-beam computed tomography imaging. J Endod 2010;36:542–5. 22. Neelakantan P, Subbarao C, Subbarao VC. Comparative evaluation of modified canal staining and clearing technique, cone-beam computed tomography, peripheral quantitative computed tomography, spiral computed tomography, and plain and contrast medium–enhanced digital radiography in studying root canal morphology. J Endod 2010;36:1547–51. 23. Neelakantan P, Subbarao C, Ahuja R, et al. Cone-beam computed tomography study of root and canal morphology of maxillary first and second molars in an indian population. J Endod 2010;36:1622–7. 24. Gulabivala K, Aung TH, Alavi A, Ng YL. Root canal morphology of Burmese mandibular molars. Int Endod J 2001;34:359–70. 25. Quackenbush LE. Mandibular molar with three distal root canals. Dent Traumatol 1986;2:48–9. 26. Christie WH, Thompson GK. The importance of endodontic access in locating maxillary and mandibular molar canals. J Can Dent Assoc 1994;60:527–32. 27. Pruett JP, Clement DJ, Carnes DL. Cyclic fatigue testing of nickel-titanium endodontic instruments. J Endod 1997;23:77–85.
JOE — Volume 41, Number 3, March 2015
Prevalence of 3- and 4-rooted First and Second Mandibular Molars in the Israeli Population Avi Shemesh, DMD,* Avi Levin, DMD,* Vered Katzenell, DMD,* Joe Ben Itzhak, DMD,* Oleg Levinson, DMD,† Avraham Zini, PhD, DMD, MPH,‡ and Michael Solomonov, DMD* Abstract Introduction: Three-rooted mandibular molars are 1 of the anatomic variations of mandibular molars. The location of the additional root is distolingual (radix entomolaris) or mesiobuccal (radix paramolaris). The purpose of this retrospective study was to assess the prevalence of 3- and 4-rooted mandibular first and second molars in the Israeli population and to classify them according to dimension, curvature, and location of separation from the main root. Methods: A total of 1020 Israel patients’ cone-beam computed tomographic scans were screened and evaluated. The incidence of 3- and 4-rooted first and second mandibular molars were recorded and analyzed. One thousand four hundred sixty-five mandibular second molars and 1,229 mandibular first molars were evaluated. Results: The overall incidence of patients with 3-rooted mandibular first and second molars was 2.6% and 1.78%, respectively. The bilateral incidence of 3-rooted mandibular first and second molars was 26%. The incidence of 4-rooted mandibular second molar was 0.55%. No significant difference was found regarding sex or side of occurrence. Conclusions: The occurrence of 3-rooted mandibular first molars in the Israeli population was rare, but clinicians should be aware of the special characteristic of this anatomic variation to modify accordingly the form of pulp chamber opening and choose appropriate instrumentation. (J Endod 2015;41:338–342)
Key Words Cone-beam computed tomographic imaging, mandibular molar, radix entomolaris, radix paramolaris
From the *Department of Endodontics, Israel Defense Forces Medical Corps, Tel Hashomer, Israel; †Private Practice, Tel-Aviv, Israel; and ‡Department of Community Dentistry, Hebrew University-Hadassah School of Dental Medicine, Jerusalem, Israel. Address requests for reprints to Dr Avi Shemesh, Department of Endodontics, Israel Defense Forces Medical Corps, Tel Hashomer, Israel. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2015 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2014.11.006
338
Shemesh et al.
T
he basis of root canal treatment is a procedure of cleaning, shaping, and obturation (1). Knowledge of root anatomy and canal morphology is essential for successful endodontic treatment (2). The first and second mandibular molars are usually 2 rooted: 1 mesial root and 1 distal root (2). One of the anatomic variations of mandibular molars is an additional root, which was first mentioned in the literature by Carabelli (3) and called radix entomolaris in the distolingual location or radix paramolaris in the mesiobuccal location (4, 5). This variation is well documented in the literature, but most publications deal with first molars with 3 roots. The additional root can be classified by curvature, dimension, and point of separation from the main root (4, 6). The frequency of an additional root in the first mandibular molar is up to 32% in Eskimos, 30% in Chinese, and 18.8% in Japanese. In the European population, a maximum frequency of 3.4%–4.2% has been found (7–13). The frequency of an additional root in the second mandibular molar is up to 3.5% in Brazilians, 1.9% in whites, and 25.8% in Koreans (14–16). Cone-beam computed tomographic (CBCT) imaging is a 3-dimensional (3D) imaging technique that can be useful for diagnosing irregular anatomy (17, 18). Recently, CBCT imaging has been found to be useful and accurate in assessing root canal morphology. CBCT scanning is a noninvasive method that provides for axial and cross-sectional observation of each tooth and makes it easier to diagnose additional roots (19–23). The purpose of the study was to investigate the prevalence of additional roots in the first and second mandibular molars in the Israeli population and to classify them by dimension, curvature, and point of separation from the main root.
Materials and Methods The study was approved by the Ethics Committee of Medical Corps, Israeli Defense Forces (IDF-1258). A total of 1020 patients’ retrospective dental CBCT (Alioth; Asahi Roentgen IND, Kyoto, Japan) records, which had already been recorded in an x-ray institute in Israel from 2009 to 2012, were examined. The patients (447 males and 573 females) were referred to this institute and required a tomographic examination by CBCT imaging as part of their dental examination, diagnosis, and treatment planning. The CBCT images were taken using the ASAHI Alioth CBCT device at 360 x-ray tube head rotation. All CBCT scans were reformatted to standard manufacturer settings; the exposure parameters of each scan were as follows: constant tube voltage of 85 kV, tube current of 6 mA, and field of view of 80 80 mm with a resolution of 0.155 0.155 0.154999 mm. CBCT exposures were performed with the minimum exposure necessary for adequate image quality. Personal details including age and sex of all these patients were recorded. The CBCT images were analyzed with OnDemand3D software (CyberMed, Irvine, CA) in a darkroom. The contrast and brightness of the images were adjusted using the image processing tool in the software to ensure optimal visualization. CBCT images were evaluated by 2 graduate endodontic residents who were calibrated based on the criteria and variants established before their evaluation. CBCT images were analyzed simultaneously to reach a consensus for the interpretation of the radiographic findings. In cases of
JOE — Volume 41, Number 3, March 2015
Clinical Research disagreement, a third, definitive evaluation was conducted by an endodontist with 10 years of experience who was calibrated based on the same criteria and variants. First and second mandibular molars were analyzed using 3 planes (sagittal, axial, and coronal) slices (Fig. 1A and B), and additional roots were classified as follows (Fig. 2A–F): 1. Curvature, straight or curved root 2. Dimension, shorter and conical or normal length compared with other roots 3. Point of separation from the main root, cervical or apical In cases of disagreement, a third, determinate valuation was conducted by an endodontist with 10 years of experience. The reviewers were calibrated on the basis of the criteria and variants established before their evaluation. The Pearson chi-square test was applied to examine any statistically significant difference between sex and the side of occurrence. A P value .05) or side of occurrence (left vs right side, P > .05) (Table 1). Table 2 indicates that 26% (12/46 patients) of the 3-rooted mandibular first molars occurred bilaterally, and all cases of 4-rooted mandibular molars are unilateral (Fig. 4). One of the patients has radix paramolaris in all 4 mandibular molars. Analysis of the 3-rooted mandibular first molars revealed (Table 3) the following:
1. Most of the radix entomolaris roots are curved roots (18/25) with the same length as the main root (17/25) and the point of separation is in the cervical third of the root (23/25). 2. All of the radix paramolaris roots are straight roots (7/7) and have the same length as the main root (7/7). Analysis of the 3-rooted mandibular second molars (Table 3) revealed that most of the radix paramolaris roots are of the same length as the main root (18/20).
Discussion An additional root in mandibular molars is 1 of the anatomic variations of these teeth. The presence of additional roots in mandibular molars is associated with certain ethnic groups (7–16). According to the present results, the occurrence of radix entomolaris roots in mandibular first and second molars in the Israeli population was 2.03% and 0.41% of all teeth examined, respectively. The occurrence of radix paramolaris roots in mandibular first and second molars in the Israeli population was 0.57% and 1.37% of all teeth examined, respectively. This finding is in agreement with a previous report on Europeans but is lower compared with data reported for non-European races (7–16). In the present study, no significant difference was found according to sex or the side of occurrence. However, other studies reported that 3-rooted mandibular first molars occurred more frequently on the right or left side (11, 12, 17, 24, 25). Zhang et al (13) analyzed 232 mandibular first molars and 157 mandibular second molars, and they found one 4-rooted mandibular first molar. In the present study, we found 8 mandibular second molars with 4 roots. Identifying the additional root is critical for successful treatment. Periapical x-rays are 2-dimensional, and the additional root might be hidden behind the main root, especially if the additional root is short or curved. A second radiograph should be taken from a more mesial or distal angle (30 ) and can be useful for the diagnosis (4, 6). The ultimate examination is CBCT imaging, providing 3D observations of the additional root and its exact relation to the pulp chamber. Knowledge of the additional root’s existence and location leads to correct preparation of the access cavity for locating all canals (26). The conventional triangular opening cavity must be modified to a trapezoidal form in order to locate and access the orifice of the additional root better (6). An extension of the access cavity to the orifice location
Figure 1. CBCT images of a first mandibular molar with a radix entomolaris: (A) cross-sectional slice and (B) axial slice.
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Figure 2. CBCT images of mandibular molars with a radix entomolaris or paramolaris. (A) A second molar with a straight radix entomolaris. (B) A second molar with a curved radix paramolaris. (C) A first molar normal length radix paramolaris. (D) A first molar with a short radix paramolaris. (E) A first molar with radix entomolaris with apical separation. (F) A second molar with radix entomolaris with cervical separation.
of the additional root is necessary in order to avoid complications or a ‘‘missed canal’’ during root canal treatment (4). Our results support previous findings that the additional root morphology is variable (4, 6). Compared with the main root, the 340
Shemesh et al.
additional root can be shorter or more curved. We found that radix entomolaris and radix paramolaris roots are different. For example, radix paramolaris in the first mandibular molar is a straight root with the same length as the main root, and the JOE — Volume 41, Number 3, March 2015
Clinical Research TABLE 1. Analysis of Sex and Side Distribution of 3- and 4-rooted Mandibular Molars in the Israeli Population Radix paramolaris (%)
4-rooted tooth
P value*
10 (40) 15 (60)
6 (85.7) 1 (14.3)
0 0
.209
617 613 1229
14 (56) 11 (44) 25 (2.03)
4 (57.1) 3 (42.9) 7 (0.57)
0 0 0
.753
814 651
5 (83.3) 1 (16.7)
12 (60) 8 (40)
4 (50) 4 (50)
.551
743 722 1465 2694
2 (33.3) 4 (66.7) 6 (0.41) 31
10 (50) 10 (50) 20 (1.37) 27
5 (62.5) 3 (37.5) 8 (0.55) 8
.760
No. of teeth First molar Sex Female Male Side Right Left Total Second molar Sex Female Male Side Right Left Total Total
679 550
Radix entomolaris (%)
*Nonparametric Pearson chi-square test.
Figure 3. CBCT axial images of 4-rooted second mandibular molars.
separation from the main root is apical. Radix entomolaris in the first mandibular molar is usually a curved root with coronal separation. These findings may help the clinician to plan his instrumentation and obturation technique if an additional root is identified during root canal treatment. For example, curvature and radius of curvature are important factors that can lead to instrument breakage, so these data help the clinician choose appropriate instruments for safer shaping (27).
TABLE 2. Analysis of the Distribution of Unilateral and Bilateral Occurrences among 46 Patients with 3-rooted Mandibular Molars: Cases in This Study
First molar Unilateral Bilateral Second molar Unilateral Bilateral
Radix entomolaris (%)
Radix paramolaris (%)
Total
13 (68.4) 6 (31.6)
3 (60) 2 (40)
16 8
2 (50) 2 (50)
16 (88.8) 2 (11.2)
18 4
JOE — Volume 41, Number 3, March 2015
Figure 4. CBCT axial images of bilateral radix entomolaris first mandibular molars.
3- and 4-rooted Molars in the Israeli Population
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Clinical Research TABLE 3. Classification of First and Second 3-rooted Mandibular Molars by Dimension, Curvature, and Point of Separation Curvature
First molar Radix paramolaris Radix entomolaris Total Second molar Radix paramolaris Radix entomolaris Total
Dimension
Total
Straight root
Curved root
Same length
Short length
Cervical separation
Apical separation
7 25 32
7 7 14
0 18 18
7 17 24
0 8 8
0 23 23
7 2 9
20 6 26
19 5 24
1 1 2
18 4 22
2 2 4
12 5 18
8 1 10
Conclusion The incidence of additional roots in mandibular molars in the Israeli population is lower than that of other populations. CBCT data can reveal 3D characteristics of an additional root such as dimension, curvature, and exact location of separation and help the clinician during the opening of the pulp chamber and choosing of appropriate instruments.
Acknowledgments The authors deny any conflicts of interest related to this study.
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JOE — Volume 41, Number 3, March 2015
