RESEARCH

 

Root and canal morphology of the mandibular first molar: A micro-computed tomography-focused observation of literature with illustrative cases. Part 1: External root morphology

 

 

CH Jonker^I; PJ van der Vyver^II; AC Oettlé^III

^IBChD, Dip Odont (Endo), MSc (Endo), PGCert (ClinEd), AFHEA, PhD student in Anatomy (University of Pretoria), Faculty of Health, Peninsula Dental School, University of Plymouth Ground, Truro Dental Education Facility, Knowledge Spa, Royal Cornwall Hospital, Truro, UK. ORCID: 0000-0002-9110-5208
^IIBChD, PG Dip Dent (Endo), PG Dip Dent (Aesthet Dent), MSc, PhD, Department of Odontology, School of Dentistry, School of Health Sciences, University of Pretoria, Pretoria 0031, South Africa ORCID: 0000-0003-1951-6042
^IIIMBBCh, DTE, MSc, PhD, Department of Anatomy and Histology, School of Medicine, Sefako Makgatho Health Sciences University, Pretoria, South Africa. ORCID: 0000-0002-9389-057X

Correspondence

 

 

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ABSTRACT

The mandibular first molar often requires endodontic intervention, which can be challenging and complex with several variants in the number of canals and roots. Usually, these teeth have a single mesial and distal root, but variants and anomalies have been noted. The incidence of the number of roots can differ between populations. For instance, up to a third of East Asians present with a third root, while the global prevalence is 8.9%. One- and four-rooted first molar teeth are seldom encountered. Over the years different methods have been used to study root and canal morphology, but micro-computed tomography (micro-CT) has provided a non-invasive method to study root and canal morphology in high definition. This paper is the first of two giving an overview of available literature on various aspects of the external and internal root and canal morphology of the mandibular first permanent molar. The aim is to provide an overview of relevant aspects of the external root morphology of the mandibular first molar in different populations. The content is supported by illustrative micro-CT images and a report on clinical cases where anomalies have been treated.

Keywords: Micro-CT, number of roots, radix entomolaris, radix paramolaris

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INTRODUCTION

Root canal treatment involves the removal of irreversibly inflamed or infected tissues from a root canal system.^1,2 The endodontic treatment of molars can be particularly challenging due to their root and root canal complexity.² Variants in roots or canals can easily be overlooked during clinical investigation and if they remain undiscovered could compromise the treatment outcome. These undiscovered roots potentially harbour infected or inflamed root canals, which can cause re-infection and ultimate treatment failure.^2-4

The mandibular first molars are often neglected in the early years, placing them at risk of early carious pulpal involvement leading to root canal treatment.⁵ They often require endodontic intervention, which can be challenging and complex with several variants in the number of canals and roots.^2,6,7 In most populations the mandibular first molars have one mesial (M) and one distal (D) root with either three or four canals.^7-9 The incidence of the number of roots and root canals can differ between populations.^10-13 An additional root can be present on either the buccal or lingual surface. A radix entomolaris (RE) is an extra root on the disto-lingual side (DL); where an additional root is present on the mesiobuccal side it is referred to as a radix paramolaris (RP).^14,15

Micro-computed tomography (micro-CT) is a non-invasive method to study root and canal morphology in high definition.¹⁶ Although micro-CT was not originally intended for use in dentistry, Nielsen et al.¹⁶ first used it to describe the root and root canal morphology of a maxillary first molar. Since then it has been used regularly for morphological studies and reporting on complex detail in human dentition; it has therefore been proposed as the most suitable method to describe complexities and fine morphological detail in dental studies.^7,16-19 In combination with suitable software (for example Avizo), all the components of a tooth can be viewed in different colours and isolated from each other in a segmentation process called the watershed.^20,21 Images can also be magnified and rotated for complete observation.

Figure 1 depicts examples of three-rooted mandibular first molars (RE) viewed through micro-CT and Avizo software, while Figure 2 illustrates two clinical cases of South African patients.

 

 

The aim of this paper is to provide an overview of available literature on root morphology of the mandibular first molar supported by illustrative images in micro-CT and clinical cases. Authors report on different methods and populations that are included in the review, but this paper focuses on the use of micro-CT.

Number of roots

The consensus is that the mandibular first molar has two roots⁷ and the prevalence can range between 73.5%¹² and 100%.⁹ 10% nitric acid, and 99% methyl salicylate. India ink was coronally injected into the pulp chamber and withdrawn apically by suction. The teeth were viewed under a magnifying lens and the numbers of root canals and their configurations, lateral canals, intercanal communications, and multiple apical foramina were recorded, along with the number of roots and their morphology. Student's t test for independent samples was used to assess significant differences in the root canal system. All specimens were tworooted with one mesial and one distal root. Root fusion was more frequent in the second than in the first molar: 3.2% versus 0.4%. Vertucci type IV canal configuration was most frequently recorded in the mesial root of the first (44.6% Figure 1 illustrates the root and canal morphology of a typical mandibular first molar with a single M and D root using micro-CT and Avizo software.

Variants are single-rooted, three-rooted and four-rooted teeth. In a recent meta-analysis of available literature, a group of authors determined that, globally, the prevalence of two-rooted first molars was 90.2% and 8.9% for three-rooted teeth. They also did a geographic analysis of the prevalence of three-rooted first molars and found that the distribution was 12.2% in Asia, 3.2% in Africa and 3.2% in Europe.²² Only a few studies on African subjects could be found in the literature reviewed. Subjects from Uganda, Tanzania and Kenya all had two roots,^9,23,24 10% nitric acid, and 99% methyl salicylate. India ink was coronally injected into the pulp chamber and withdrawn apically by suction. The teeth were viewed under a magnifying lens and the numbers of root canals and their configurations, lateral canals, intercanal communications, and multiple apical foramina were recorded, along with the number of roots and their morphology. Student's t test for independent samples was used to assess significant differences in the root canal system. All specimens were tworooted with one mesial and one distal root. Root fusion was more frequent in the second than in the first molar: 3.2% versus 0.4%. Vertucci type IV canal configuration was most frequently recorded in the mesial root of the first (44.6%^,23,24University of Nairobi\nResults: The mesial root of mandibular first molars had two canals in 96.3% of the teeth in both males and females and type IV canal configuration was most prevalent in the mesial root. The distal root of the mandibular first molar had one canal in 57.7% of the teeth in males and females. There were significant gender variations in the number of canals and canal configurations in the distal root. Two canals were more prevalent in females (53.6% while in Egypt, 99.5% of teeth were two-rooted and 0.5% were three-rooted.²⁵ In a South African study investigating a mixed population, the authors reported an incidence of two roots in 98.7%, 1% of three-rooted first molars, 0.3% for single-rooted teeth and no teeth with four roots.⁸

There are several papers available on the number of roots in different populations and most used cone-beam computed tomography (CBCT), but few authors reported on root numbers in their micro-CT investigations. In a Chinese population where 122 first molars were observed using this technology, Gu et al.²⁶ found 1.6% of teeth were single-rooted, 66.4% were two-rooted and approximately 32% were three-rooted. A prevalence of approximately 2.6% with a third root was reported in a Brazilian population also using micro-CT.²⁷ An overview of investigations that reported on the number of roots in different populations is given in Table I.

Radix entemolaris (RE) and radix paramolaris (RP)

Several studies report different prevalence of RE and RP. The differences in prevalence noted could be ascribed to variations between populations. A number of investigators used CBCT and other techniques used include in vivo radiographic observations^61,62 or in vitro observations of extracted teeth.^29,42,54 Examining literature from different studies using different modalities, a group of authors in 2012 calculated an average of 14.4% of RE.⁶³ A population-specific report published in 2022 found an average prevalence of RE of 5.6% on 23 nations from five continents using CBCT. The findings ranged from 0.9% in Venezuela to 22.4% in China.⁶⁴ On the other hand, a literature review and meta-analysis in the same year (2022) of 72 available studies on 33 populations worldwide focusing on CBCT as the main methodology determined that the RE was present on average in 12.3% of teeth, ranging between 0% and 29% in 72 studies originating from 33 populations. On average, RP was present in 0.1% of teeth ranging between 0% and 2%.⁶⁵ There was also a rare clinical case of a first molar that had both RE and RP.⁶⁶

In Africa there were a few reports on RE or RP. In Ugandan, Tanzanian and Kenyan population groups no teeth had RE or RP.^9,23,2410% nitric acid, and 99% methyl salicylate. India ink was coronally injected into the pulp chamber and withdrawn apically by suction. The teeth were viewed under a magnifying lens and the numbers of root canals and their configurations, lateral canals, intercanal communications, and multiple apical foramina were recorded, along with the number of roots and their morphology. Student's t test for independent samples was used to assess significant differences in the root canal system. All specimens were tworooted with one mesial and one distal root. Root fusion was more frequent in the second than in the first molar: 3.2% versus 0.4%. Vertucci type IV canal configuration was most frequently recorded in the mesial root of the first (44.6% In a Senegalese population a prevalence of 3.1% was noted.⁶⁷West Africa, revealed 15 teeth with three roots (3.12% In Egypt, a prevalence of approximately 0.7% was noted in individuals of African descent,⁶⁸ while a relatively high prevalence of 10.8% was noted in Syrian individuals.⁶⁴ In South Africa a prevalence of 1% and 5.2% respectively has been reported in mixed populations from Pretoria and Durban.^8,64

A limited number of authors reported the presence of RE or RP when using micro-CT investigations. A prevalence of approximately 2.6% was noted²⁷ in a Brazilian population, while the prevalence was approximately 32% in a Chinese study.²⁶ In another example of an East Asian group, using computer tomography scanning, Song et al. report a relatively high prevalence of 24.5% in a Korean population.⁶⁹

Figure 2 depicts examples of three-rooted mandibular first molars (RE) viewed through micro-CT and Figure 3 illustrates two clinical cases of South African patients who presented with RE. A summary of other findings in literature can be found in Table II. It is interesting to note that East Asian groups from China, Taiwan, Japan, Korea and Malaysia, as well as Inuit groups, presented with prevalence often greater than 20% and sometimes over 30%, while other populations from Europe and Africa often presented with prevalence below 10% or even below 5%. It was also noted that different populations within a country can present with variants in prevalence - for example, in China it ranged between 22.1% and 32% and in India between 1% and 13.3%.

 

DISCUSSION

The root morphology of the mandibular first molar is diverse and can differ greatly among populations. A number of factors can influence the incidence, including genetics and geographic distances.^108-110 The differences between individuals or populations are therefore important factors to consider in treatment. Any variations can create difficulties during the diagnostic phase and root or canal morphology that remains undiscovered greatly increases the risk of treatment failure.^2,111

Authors have used a number of techniques to visualise the morphology of the root canal, such as radiographs,¹¹² scanning electron microscopy (SEM)67 and magnification.¹¹³ Three-dimensional techniques, for example CBCT109 and micro-CT,¹¹⁴ have revolutionised the study of root and canal morphology. Micro-CT has become the modality of choice for the investigation of complex root and canal morphology; it can display very fine detail that is easily missed when using other techniques.^114-116

The typical mandibular first molar contains two roots⁷ and the prevalence can range between 73.5% and 100%. The mandibular first molar can also be single-rooted, three-rooted and four-rooted (see Table I). It has also been determined that the global prevalence of two-rooted first molars is 90.2% and 8.9% for three-rooted ones.²² An awareness of the number of roots is important for diagnostic purposes and treatment planning. Any additional roots can create challenges for a treating clinician during endodontics and surgical difficulties once a tooth requires extraction.^2,7,96 An additional root, first described by Carabelli,¹¹⁷ can be a separate morphology or partially fused with other roots.⁶¹ As stated earlier, the additional root can be located DL (RE)¹⁵ or mesio-buccal (RP). These roots are often small and can have a sharp apical hook.¹⁴ They can be challenging to diagnose using traditional radiographs or two-dimensional diagnostic tools.¹¹⁸

Geographic distance between populations affects the prevalence of a third root; for example, it is greater in East Asian populations than in European and African groups. The prevalence can be as high as 33.1%, which was noted in a Korean population.⁸⁹ In most African populations only two roots were present (Tanzania, Uganda and Kenya) in individuals of African descent.^9,23,241 0% nitric acid, and 99% methyl salicylate. India ink was coronally injected into the pulp chamber and withdrawn apically by suction. The teeth were viewed under a magnifying lens and the numbers of root canals and their configurations, lateral canals, intercanal communications, and multiple apical foramina were recorded, along with the number of roots and their morphology. Student's t test for independent samples was used to assess significant differences in the root canal system. All specimens were tworooted with one mesial and one distal root. Root fusion was more frequent in the second than in the first molar: 3.2% versus 0.4%. Vertucci type IV canal configuration was most frequently recorded in the mesial root of the first (44.6% In a Senegalese population of African descent, a prevalence of 3.2% was noted for three-rooted first molars, which could be ascribed to a larger sample size than in the other African studies mentioned. Smaller sample sizes should be interpreted with care.¹¹⁵ In South Africa, Tredoux and co-workers⁸ found a prevalence of 1% for RE. In another mixed population group from South Africa, but in a different region (Durban, KwaZulu-Natal), a prevalence of 5.2% was noted.⁹⁶ In both these South African studies, CBCT was used. In two non-identical worldwide studies on the prevalence of RE in the same year (2022), different prevalences were reported (5.6% and 12.3%). As the prevalence is population-specific, reviews including different populations will report different prevalences. No studies could be found reporting on RE or RP in a South African population group using micro-CT.

In conclusion, the root morphology of the mandibular first molar can show variations between populations. Clinicians should be mindful of root variations or the presence of additional roots, as they can contain additional root canal systems and complicate root canal treatments. Studies focusing on African populations and specifically on South Africa are limited and no micro-CT studies were reported on in the literature researched.

Authors' declaration

The authors declare that there is no financial interest in this paper and that this paper has not been submitted elsewhere for publication. All authors agree with the content of the manuscript. This manuscript did not receive any funding from funding agencies In the public, commercial or not-for-profit sectors.

Conflict of interest

The authors declare there is no conflict of interest.

 

Acknowledgements

The corresponding author would like to extend his gratitude to Dr Charlotte Theye for technical support in preparation of the manuscript. The corresponding author would like to extend his gratitude to Dr Guy Lambourn, colleague and consultant in Prosthodontics, School of Dentistry, University of Plymouth, for his support and encouragement.

 

REFERENCES

1. Wu MK, Wesselink PR, Walton, RE. Apical terminus location of root canal treatment procedures. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000; 89: 99-103. DOI: 10.1016/S1079-2104(00)80023-2        [ Links ]

2. Vertucci FJ. Root canal morphology and its relationship to endodontic procedures. Endod Topics. 2005; 10: 3-29. DOI: 10.1111/j.1601-1546.2005.00129.x        [ Links ]

3. Versiani MA, Ordinola-Zapata R. Root canal anatomy: Implications in biofilm disinfection. In: The root canal biofilm, 1st ed. Heidelberg: Springer, 2015: 155-87        [ Links ]

4. Versiani MA, De-Deus G, Vera J, et al. Mapping of the irrigated areas of the root canal space using micro-computed tomography. Clin Oral Invest. 2015; 19: 859-66. DOI: 10.1007/s00784-014-1311-5        [ Links ]

5. Gutmann JL, Fan B. Tooth morphology, isolation, and access. Cohen's pathways of the pulp, 11th ed. St. Louis: Elsevier, 2016: 130-208        [ Links ]

6. Versiani MA, Ordinola-Zapata R, Keles A, et al. Middle mesial canals in mandibular first molars: A Micro-CT study in different populations. Arch Oral Biol. 2016; 61: 130-37. DOI: 10.1016/j. archoralbio.2015.10.020        [ Links ]

7. Versiani MA, Sousa-Neto MD, Basrani B. The root canal dentition in permanent dentition, 1st ed. Heidelberg: Springer, 2018: 89-240        [ Links ]

8. Tredoux S, Warren N, Buchanan GD. Root and canal configurations of mandibular first molars in a South African subpopulation. J Oral Sci. 2021; 63: 252-56        [ Links ]

9. Rwenyonyi CM, Kutesa A, Muwazi LM, Buwembo W. Root and canal morphology of mandibular first and second permanent molar teeth in a Ugandan population. Odontology. 2009; 97: 92-6        [ Links ]

10. Al-Qudah AA, Awawdeh LA. Root and canal morphology of mandibular first and second molar teeth in a Jordanian population. Int Endod J. 2009; 42: 775-84. DOI:10.1111/j.1365-2591.2009.01578.x        [ Links ]

11. Chen G, Yao H, Tong C. Investigation of the root canal configuration of mandibular first molars in a Taiwan Chinese population. Int Endod J. 2009; 42: 1044-49. DOI:10.1111/j.1365- 2591.2009.01619.x        [ Links ]

12. Wang Y, Zheng Q, Zhou X, et al. Evaluation of the root and canal morphology of mandibular first permanent molars in a Western Chinese population by cone-beam computed tomography. J Endod. 2010; 36: 1786-89. DOI: 10.1016/j.joen.2010.08.016        [ Links ]

13. Chourasia HR, Meshram GK, Warhadpande M, Dakshindas D. Root canal morphology of mandibular first permanent molars in an Indian population. Int J Dent. 2012; 2012: 1-6        [ Links ]

14. Calberson FL, De Moor RJ, Deroose CA. The radix entomolaris and paramolaris: Clinical approach in endodontics. J Endod, 2007; 33: 58-63        [ Links ]

15. Bolk L. Bemerkungen über wurzelvariationen am menschlichen unteren molaren. Z Morphol Anthropol, 1915; 17: 605-10        [ Links ]

16. Nielsen RB, Alyassin AM, Peters DD, Carnes DL, Lancaster J. Microcomputed tomography: An advanced system for detailed endodontic research. J Endod. 1995; 21: 561-68        [ Links ]

17. Grande NM, Plotino G, Gambarini G, et al. Present and future in the use of Micro-CT scanner 3D analysis for the study of dental and root canal morphology. Ann 1st Super Sanita. 2012; 48:26-34        [ Links ]

18. Briseño-Marroquín B, Paqué F, Maier K, Willershausen B, Wolf TG. Root canal morphology and configuration of 179 maxillary first molars by means of micro-computed tomography: An ex vivo study. J Endod. 2015; 41: 2008-13        [ Links ]

19. Ahmed HMA, Ibrahim N, Mohamad NS, et al. Application of a new system for classifying root and canal anatomy in studies involving micro-computed tomography and cone beam computed tomography: Explanation and elaboration. Int Endod J. 2021; 54: 1056-82        [ Links ]

20. Meyer F, Beucher S. Morphological segmentation. J Vis Commun Image Represent, 1990; 1: 21-46        [ Links ]

21. Westenberger P. Avizo - Three-dimensional visualization framework. In: Proceedings of the Geoinformatics 2008 - Data to Knowledge, USGS, 2008, 13-4        [ Links ]

22. Tomaszewska IM, Jarzebska A, Skinningsrud B, Pekala PA, Wronski S, Iwanaga J. An original Micro-CT study and meta-analysis of the internal and external anatomy of maxillary molars -implications for endodontic treatment: Morphology of maxillary molars. Clin Anat. 2018; 31: 838-53. DOI: 10.1002/ca.23201        [ Links ]

23. Muriithi NJ, Maina SW, Okoth J, Gathece LW. Internal root morphology in mandibular first permanent molars in a Kenyan population. East Afr Med J. 2012; 89: 166-71        [ Links ]

24. Madjapa HS, Minja IK. Root canal morphology of native Tanzanian permanent mandibular molar teeth. Pan Afr Med J. 2018; 31: 1-6. DOI: 10.11604/pamj.2018.31.24.14416        [ Links ]

25. Sharaan M, Elrawdy A. An evaluation of mandibular molars root canal morphology using cone-beam computed tomography in an Egyptian subpopulation. Tanta Dent J. 2017; 14: 220-4. DOI: 10.4103/tdj.tdj_50_17        [ Links ]

26. Gu Y, Lu Q, Wang H, Ding Y, Wang P, Ni L. Root canal morphology of permanent three-rooted mandibular first molars - Part I: Pulp floor and root canal system. J Endod. 2010; 36: 990-4, DOI :10.1016/j.joen.2010.02.030        [ Links ]

27. Rodrigues CT, Oliveira-Santos C, Bernardineli N, et al. Prevalence and morphometric analysis of three-rooted mandibular first molars in a Brazilian subpopulation. J Appl Oral Sci. 2016; 24: 535-42. DOI: 10.1590/1678-775720150511        [ Links ]

28. Torres A, Jacobs R, Lambrechts P, et al. Characterization of mandibular molar root and canal morphology using cone beam computed tomography and its variability in Belgian and Chilean population samples. Imaging Sci Dent. 2015; 45: 95-101        [ Links ]

29. Gulabivala K, Aung TH, Alavi A, Ng Y. Root and canal morphology of Burmese mandibular molars. Int Endod J. 2001; 34: 359-70. DOI: 10.1046/j.1365-2591.2001.00399.x        [ Links ]

30. Silva EJNL, Nejaim Y Silva AV, Haiter-Neto F, Cohenca N. 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. DOI: 10.1016/j.joen.2013.04.030        [ Links ]

31. De Oliveira Mantovani V, Gabriel AE, De Silva RG, Savioli RN, Sousa-Neto MD, Cruz-Filho AM. Analysis of the mandibular molar root canal morphology. Study by computed tomography. Braz Dent J. 2022; 33: 1-8.         [ Links ]

32. Abarca J, Duran M, Parra D, Steinfort K, Zaror C, Monardes H. Root morphology of mandibular molars: A cone-beam computed tomography study. Folia Morphol. 2020; 79: 327-32        [ Links ]

33. Zhang X, Xiong S, Ma Y et al. A cone-beam computed tomographic study on mandibular first molars in a Chinese subpopulation. PLoS ONE. 2015; 10, e0134919. DOI: 10.1371/journal.pone.0134919        [ Links ]

34. Martins JNR, Gu Y Marques D, Francisco H, Caramês J. Differences on the root and root canal morphologies between Asian and White ethnic groups analyzed by cone-beam computed tomography. J Endod, 2018; 44: 1096-104. DOI: 10.1016/j.joen.2018.04.001        [ Links ]

35. Monsarrat P, Arcaute B, Peters OA, et al. Interrelationships in the variability of root canal anatomy among the permanent teeth: A full-mouth approach by cone-beam CT. PLoS ONE. 2016; 11: e0165329. DOI: 10.1371/journal.pone.0165329        [ Links ]

36. Kantilieraki E, Delantoni A, Angelopoulos C, Beltes P. Evaluation of root and root canal morphology of mandibular first and second molars in a Greek population: A CBCT study. Eur Endod J. 2019; 4: 62-8        [ Links ]

37. Felsypremila G, Vinothkumar TS, Kandaswamy D. Anatomic Symmetry of root and root canal morphology of posterior teeth in an Indian subpopulation using cone-beam computed tomography: A retrospective study. Eur J Dent. 2015; 09: 500-7. DOI: 10.4103/1305-7456.172623        [ Links ]

38. Shahi S, Yavari HR, Rahimi S, Torkamani R. Root canal morphology of human mandibular first permanent molars in an Iranian population. J Dent Res Dent Clin Dent Prospects. 2008; 2: 203. DOI: 10.5681/joddd.2008.004        [ Links ]

39. Akhlaghi NM, Khalilak Z, Vatanpour M, et al. Root canal anatomy and morphology of mandibular first molars in a selected Iranian population: An in vitro study. Iran Endod J. 2017; 12: 87-91        [ Links ]

40. Madani ZS, Mehraban N, Moudi E, Bijani A. Root and canal morphology of mandibular molars in a selected Iranian population using cone-beam computed tomography. Iran Endod J. 2017; 12: 143-8        [ Links ]

41. 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. DOI: 10.1016/j.joen.2013.09.012        [ Links ]

42. Peiris R. Root and canal morphology of human permanent teeth in a Sri Lankan and Japanese population. Anthropol Sci. 2008; 116: 123-33. DOI: 10.1537/ase.070723        [ Links ]

43. 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. DOI: 10.1016/j.joen.2013.08.015,         [ Links ]

44. Park JB, Kim N, Park S, Kim Y, Ko Y. Evaluation of root anatomy of permanent mandibular premolars and molars in a Korean population with cone-beam computed tomography. Eur J Dent. 2013; 7: 94-101        [ Links ]

45. Deng PU, Halim MS, Sam'an Malik Masudi SA, Shehadat BA. Cone-beam computed tomography analysis on root and canal morphology of mandibular first permanent molars among a multiracial East Coast Malaysian population. Eur J Dent. 2018; 12: 410-6        [ Links ]

46. Mukhaimer R, Azizi Z. Incidence of radix entomolaris in mandibular first molars in a Palestinian population: A clinical investigation. Int Sch Res Notices. 2014; 2014: 1-5        [ Links ]

47. Martins JN, Mata A, Marques D, Caramês J. Prevalence of root fusions and main root canal merging in human upper and lower molars: A cone-beam computed tomography in vivo study. J Endod. 2016; 42: 900-8        [ Links ]

48. Martins JNR, Marques D, Mata A, Caramês J. Root and root canal morphology of the permanent dentition in a Caucasian population: A cone-beam computed tomography study. Int Endod J. 2017; 50: 1013-26. DOI: 10.1111/iej.12724        [ Links ]

49. Mashyakhy M, Chourasia HR, Halboub E, Almashraqi AA, Khubrani Y Gambarini G. Anatomical variations and bilateral symmetry of roots and root canal system of mandibular first permanent molars in a Saudi Arabian population utilizing cone-beam computed tomography. Saudi Dent J. 2019; 31: 481-6. DOI: 10.1016/j.sdentj.2019.04.001        [ Links ]

50. Pérez-Heredia M, Ferrer-Luque CM, Bravo M, Castelo-Baz P, Ruíz-Piñón M, Baca P. Cone-beam computed tomographic study of root anatomy and canal configuration of molars in a Spanish population. J Endod. 2017; 43: 1511-6. DOI: 10.1016/j.joen.2017.03.026        [ Links ]

51. Peiris R, Takahashi M, Sasaki K, Kanazawa E. Root and canal morphology of permanent mandibular molars in a Sri Lankan population. Odontology. 2007; 95: 16-23. DOI: 10.1007/s10266-007-0074-8        [ Links ]

52. Peiris R, Malwatte U, Abayakoon J, Wettasinghe A. Variations in the root form and root canal morphology of permanent mandibular first molars in a Sri Lankan population. Anat Res Int. 2015; 2015: 1-7. DOI: 10.1155/2015/803671        [ Links ]

53. Huang RY, Cheng WC, Chen CJ, et al. Three-dimensional analysis of the root morphology of mandibular first molars with distolingual roots. Int Endod J. 2010; 43: 478-84. DOI: 10.1111/j.1365-2591.2010.01702.x        [ Links ]

54. Gulabivala K, Opasanon A, Ng YL, Alavi A. Root and canal morphology of Thai mandibular molars. Int Endod J. 2002; 35: 56-62. DOI: 10.1046/j.1365-2591.2002.00452.x        [ Links ]

55. Miloglu O, Arslan H, Barutcigil C, Cantekin K. Evaluating root and canal configuration of mandibular first molars with cone beam computed tomography in a Turkish population. J Dent Sci. 2013; 8: 80-6. DOI: 10.1016/j.jds.2012.09.002        [ Links ]

56. Nur BG, Ok E, Altunsoy M, Aglarci OS, Colak M, Gungor, E. Evaluation of the root and canal morphology of mandibular permanent molars in a south-eastern Turkish population using cone-beam computed tomography. Eur J Dent. 2014; 08: 154-9. DOI: 10.4103/1305-7456.130584        [ Links ]

57. Demirbuga S, Sekerci A, Dincer A, Cayabatmaz M, Zorba Y. Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular first and second molars in Turkish individuals. Med Oral Patol Oral Cir Bucal. 2013; 18: e737-e744        [ Links ]

58. Al Shehadat S, Waheb S, Al Bayatti SW, Kheder W, Khalaf K, Murray CA. Cone-beam computed tomography analysis of root and root canal morphology of first permanent lower molars in a Middle East subpopulation. J Int Soc Prev Community Dent. 2019; 9: 458-63        [ Links ]

59. Pham K, Le AL. Evaluation of roots and canal systems of mandibular first molars in a Vietnamese subpopulation using cone-beam computed tomography. J Int Soc Prev Community Dent. 2019; 9: 356-62. DOI: 10.4103/jispcd.JISPCD_52_19        [ Links ]

60. Senan EM, Madfa AA, Alhadainy HA. Root and canal configuration of mandibular first molars in a Yemeni population: A cone-beam computed tomography. Eur Endod J. 2020; 5: 10-7        [ Links ]

61. Garg AK, Tewari RK, Kumar A, Hashmi SH, Agrawal N, Mishra SK. Prevalence of three-rooted mandibular permanent first molars among the Indian population. J Endod. 2010; 36: 1302-6. DOI: 10.1016/j.joen.2010.04.019        [ Links ]

62. Chandra SS, Chandra S, Shankar P, Indira R. Prevalence of radix entomolaris in mandibular permanent first molars: A study in a South Indian population. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2011; 112: e77-e82. DOI: 10.1016/j.tripleo.2011.02.016        [ Links ]

63. Abella F, Patel S, Durán-Sindreu F, Mercadé M, Roig M. Mandibular First molars with distolingual roots: Review and clinical management: Mandibular first molars with disto-lingual roots. In Endod J. 2012; 45: 963-78. DOI: 10.1111/j.1365-2591.2012.02075.x        [ Links ]

64. Martins JN, Nole C, Ounsi HF, et al. Worldwide assessment of the mandibular first molar second distal root and root canal: A cross-sectional study with meta-analysis. J Endod. 2022; 48: 223-33        [ Links ]

65. Aung NM, Myint KK. Three-rooted permanent mandibular first molars: A meta-analysis of prevalence. Int J Dent. 2022; 2022: 1-30        [ Links ]

66. Gladwin L, Patel JA. Rare finding of a radix entomolaris and radix paramolaris in a lower first mandibular molar requiring endodontic treatment: A case report. Dent Update. 2022; 49: 5158        [ Links ]

67. 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        [ Links ]

68. Younes SA, Al-Shammery AR, El-Angbawi MF. Three-rooted permanent mandibular first molars of Asian and Black groups in the Middle East. Oral Surg Oral Med Oral Pathol. 1990; 69: 102-5. DOI: 10.1016/0030-4220(90)90276-X        [ Links ]

69. 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: 6537. DOI: 10.1016/j.joen.2009.10.007        [ Links ]

70. Shaw JCM. The teeth, the bony palate and the mandible in Bantu races of South Africa, 1st ed. London: Bale, Sons & Danielsson, 1931: 32-8        [ Links ]

71. Ferraz JAB, Pecora JD. Three-rooted mandibular molars in patients of Mongolian, Caucasian and Negro origin. Braz Dent J. 1992; 3: 113-7        [ Links ]

72. Da Costa Rocha LF, Manoel DSN, Sandra RF, Wanderly FD, Pécora JD. External and internal anatomy of mandibular molars. Braz Dent J. 1996; 7: 33-40        [ Links ]

73. Corzon MEJ. Miscegenation and the prevalence of three-rooted mandibular first molars in the Baffin Eskimo. Community Dent Oral Epidemiol. 1974; 2: 130-1. DOI: 10.1111/J.1600- 0528.1974.tb01669.x-i1        [ Links ]

74. Curzon ME, Curzon JA. Three-rooted mandibular molars in the Keewatin Eskimo. J Can Dent Assoc (Tor). 1971; 37: 71-2        [ Links ]

75. Somogyi-Csizmazia W, Simons AJ. Three-rooted mandibular first permanent molars in Alberta Indian children. J Can Dent Assoc (Tor). 1971; 37: 105-6        [ Links ]

76. Zhang R, Yang H, Yu X, Wang H, Hu T, Dummer PMH. Use of CBCT to identify the morphology of maxillary permanent molar teeth in a Chinese subpopulation. Int Endod J. 2011; 44: 162-9. DOI: 10.1111/j.1365-2591.2010.01826.x        [ Links ]

77. Yang Y Zhang LD, Ge J, Zhu Y Prevalence of 3-rooted first permanent molars among a Shanghai Chinese population. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010; 110: e98-e101. DOI: 10.1016/j.tripleo.2010.05.068        [ Links ]

78. Curzon MEJ. Three-rooted mandibular permanent molars in English Caucasians. J Dent Res. 1973; 52: 181. DOI: 10.1177/00220345730520011901        [ Links ]

79. Beshkenadze E, Chipashvili N. Anatomo-morphological features of the root canal system in Georgian population - cone-beam computed tomography study. Georgian Med News. 2015; 247: 7-14        [ Links ]

80. Schäfer E, Breuer D, Janzen S. The prevalence of three-rooted mandibular permanent first molars in a German population. J Endod. 2009; 35: 202-5. DOI: 10.1016/j.joen.2008.11.010        [ Links ]

81. Hochstetter RL. Incidence of trifurcated mandibular first permanent molars in the population of Guam. J Dent Res. 1975; 54: 1097. DOI: 10.1177/00220345750540052401        [ Links ]

82. Bansal R, Ajwani P. Prevalence and morphological study of three-rooted mandibular first molar [radix molar] in an Indian population. Int J Hum Anat. 2010; 2: 1-8        [ Links ]

83. Kuzekanani M, Najafipour R. Prevalence and distribution of radix paramolaris in the mandibular first and second molars of an Iranian population. J Int Soc Prev Community Dent. 2018; 8: 240-4        [ Links ]

84. Rahimi S, Mokhtari H, Ranjkesh B, et al. Prevalence of extra roots in permanent mandibular first molars in an Iranian population: A CBCT analysis. Iran Endod J. 2017; 12: 70-3        [ Links ]

85. Shemesh A, Levin A, Katzenell V, et al. Prevalence of 3- and 4-rooted first and second mandibular molars in the Israeli population. J Endod. 2015; 41: 338-42. DOI: 10.1016/j.joen.2014.11.006        [ Links ]

86. Onda S, Minemura R, Masaki T, Funatsu S. Shape and number of the roots of the permanent molar teeth. Bull Tokyo Dent Coll. 1989; 30: 221-31        [ Links ]

87. Walker RT. Three-rooted lower first permanent molars in Hong Kong Chinese. Br Dent J. 1985; 159: 298-9        [ Links ]

88. Walker RT. Root form and canal anatomy of mandibular first molars in a Southern Chinese population. Dent Traumatol. 1988; 4: 19-22. DOI: 10.1111/j.1600-9657.1988.tb00287.x        [ Links ]

89. Song JS, Kim SO, Choi BJ, Choi HJ, Son HK, Lee JH. Incidence and relationship of an additional root in the mandibular first permanent molar and primary molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2009; 107: e56-e60. DOI: 10.1016/j.tripleo.2008.09.004        [ Links ]

90. Zaatar EI, Al-Kandari AM, Alhomaidah S, Yasin IMA. Frequency of endodontic treatment in Kuwait: Radiographic evaluation of 846 endodontically treated teeth. J Endod. 1997; 23: 453-6. DOI: 10.1016/S0099-2399(97)80302-0        [ Links ]

91. Pattanshetti N, Gaidhane M, Kandari AMA. Root and canal morphology of the mesiobuccal and distal roots of permanent first molars in a Kuwait population - a clinical study. Int Endod J. 2008; 41: 755-62. DOI: 10.1111/j.1365-2591.2008.01427.x        [ Links ]

92. Pan JYY, Parolia A, Chuah SR, Bhatia S, Mutalik S, Pau A. Root canal morphology of permanent teeth in a Malaysian subpopulation using cone-beam computed tomography. BMC Oral Health. 2019; 19: 1-15. DOI: 10.1186/s12903-019-0710-z        [ Links ]

93. Al-Nazhan S. Incidence of four canals in root-canal-treated mandibular first molars in a Saudi Arabian sub-population: Root canal morphology. Int Endod J. 1999; 32: 49-52. DOI: 10.1046/j.1365-2591.1999.00188.x        [ Links ]

94. Loh HS. Incidence and features of three-rooted permanent mandibular molars. Aust Dent J. 1990; 35: 434-7. DOI: 10.1111/j.1834-7819.1990.tb05426.x        [ Links ]

95. Drennan MR. The dentition of the Bushmen tribe. Ann S Afr Museum. 1929; 24: 61-87        [ Links ]

96. Martins JN, Nole C, Ounsi HF, et al. Worldwide assessment of the mandibular first molar second distal root and root canal: A cross-sectional study with meta-analysis. J Endod. 2022; 48: 223-33        [ Links ]

97. Peiris HRD, Pitakotuwage TN, Takahashi M, Sasaki K, Kanazawa E. Root canal morphology of mandibular permanent molars at different ages. Int Endod J. 2008; 41: 828-35. DOI: 10.1111/j.1365-2591.2008.01428.x        [ Links ]

98. Ahmed HA, Abu-bakr NH, Yahia N, Ibrahim YE. Root and canal morphology of permanent mandibular molars in a Sudanese population. Int Endod J. 2007; 40: 766-71. DOI: 10.1111/j.1365-2591.2007.01283.x        [ Links ]

99. Tu MG, Tsai CC, Jou MJ, et al. Prevalence of three-rooted mandibular first molars among Taiwanese individuals. J Endod. 2007; 33: 1163-6. DOI: 10.1016/j.joen.2007.07.020        [ Links ]

100. Huang RY, Lin CD, Lee MS, et al. Mandibular disto-lingual root: A consideration in periodontal therapy. J Periodontol. 2007; 78: 1485-90. DOI: 10.1902/jop.2007.060419        [ Links ]

101. Yew S, Chan KA. Retrospective Study of endodontically treated mandibular first molars in a Chinese population. J Endod. 1993; 19: 471-3. DOI: 10.1016/S0099-2399(06)80536-4        [ Links ]

102. Tu MG, Huang HL, Hsue SS, et al. Detection of permanent three-rooted mandibular first molars by cone-beam computed tomography imaging in Taiwanese individuals. J Endod. 2009; 35: 503-7. DOI: 10.1016/j.joen.2008.12.013        [ Links ]

103. Chen YC, Lee YY, Pai SF, Yang SF. The morphologic characteristics of the distolingual roots of mandibular first molars in a Taiwanese population. J Endod. 2009; 35: 643-5. DOI: 10.1016/j.joen.2009.01.020        [ Links ]

104. Reichart PA, Metah D. Three-rooted permanent mandibular first molars in the Thai. Community Dent Oral Epidemiol. 1981; 9: 191-2. DOI: 10.1111/j.1600-0528.1981.tb01053.x        [ Links ]

105. Steelman R. Incidence of an accessory distal root on mandibular first permanent molars in Hispanic children. ASDC J Dent Child. 1986; 53: 122-3        [ Links ]

106. Skidmore AE, Bjorndal AM. Root canal morphology of the human mandibular first molar. Oral Surg Oral Med Oral Pathol. 1971; 32: 778-84. DOI: 10.1016/0030-4220(71)90304-5        [ Links ]

107. Taylor AE. Variations in the human tooth-form as met with in isolated teeth. J Hum Anat Physio. 1899; 33: 268-72        [ Links ]

108. Kuzekanani M, Najafipour R. Prevalence and distribution of radix paramolaris in the mandibular first and second molars of an Iranian population. J Int Soc Prev Community Dent. 2018; 8: 240-4        [ Links ]

109. Buchanan GD, Gamieldien MY Tredoux S, Vally ZI. Root and canal configurations of maxillary premolars in a South African subpopulation using cone-beam computed tomography and two classification systems. J Oral Sci. 2020; 62: 93-7. DOI: 10.2334/josnusd.19-0160        [ Links ]

110. Cleghorn BM, Christie WH, Dong CCS. Root and root canal morphology of the human permanent maxillary first molar: A literature review. J Endod. 2006; 32: 813-21        [ Links ]

111. Cantatore G, Berutti E, Castellucci A. Missed anatomy: Frequency and clinical impact. Endod Topics. 2006; 15: 3-31        [ Links ]

112. Castellucci A. Access cavity and endodontic anatomy. Endodont. 2004; 1: 245-329        [ Links ]

113. Chavda SM, Garg SA. Advanced methods for identification of middle mesial canal in mandibular molars: An in vitro study. Endodontology. 2016; 28: 92-6        [ Links ]

114. Ahmed HMA. A critical analysis of laboratory and clinical research methods to study root and canal anatomy. Int Endod J. 2022; 55: 229-80        [ Links ]

115. Ordinola-Zapata R, Martins JN, Plascencia H, Versiani MA, Bramante CM. The MB3 canal in maxillary molars: A Micro-CT study. Clin Oral Investig. 2020; 24: 4109-121        [ Links ]

116. Ahmed HMA, Versiani MA, De-Deus G, Dummer PMH. A new system for classifying root and root canal morphology. Int Endod J. 2017; 50: 761-70        [ Links ]

117. Carabelli G. Systematisches handbuch der zahnheilkunde, 2nd ed. Georg OLMS: Verlag, 1844. ISBN 3-487-41399-X        [ Links ]

118. De Moor RJG, Deroose CAJG, Calberson FLG. The radix entomolaris in mandibular first molars: An endodontic challenge. Int Endod J. 2004; 37: 789-99. DOI: 10.1111/j.1365-2591.2004.00870.x        [ Links ]

 

 

Correspondence:
Name: Dr CH Jonker
Tel: +44 1872 258104
Email: casper.jonker@plymouth.ac.uk

 

 

Author's contribution
1 . Casper H Jonker: Principal author, manuscript layout and write-up -60%
2 . Peet J van der Vyver: Treated patients and clinical images, manuscript layout and proofreading - 25%
3 . Anna C Oettlé: Proofreading and layout - 15%