|Year : 2021 | Volume
| Issue : 4 | Page : 298-306
|Root anatomy and canal configuration of human permanent mandibular second molar: A systematic review
Poonam Shamkant Joshi1, Rajesh Shetty1, Gargi S Sarode2, Vini Mehta3, Damini Chakraborty4
1 Department of Conservative Dentistry and Endodontics, Dr. D.Y. Patil Dental College and Hospital, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India
2 Department of Oral Pathology, Dr. D.Y. Patil Dental College and Hospital, Dr. D.Y. Patil Vidyapeeth, Pune, Maharashtra, India
3 Department of Public Health Dentistry, People's College of Dental Sciences and Research Centre, Bhopal, Madhya Pradesh, India
4 General Dentist, Dr. Bhowal's Dental and Implant Clinic, Newtown, WB, India
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|Date of Submission||23-Dec-2020|
|Date of Decision||10-Feb-2021|
|Date of Acceptance||19-Feb-2021|
|Date of Web Publication||13-Jan-2022|
| Abstract|| |
The objective of the study was to review the literature on root anatomy and canal configuration in permanent mandibular second molar based on Vertucci classification. Online electronic databases such as PubMed-Medline, Embase, Scopus, and Cochrane Library were searched using appropriate keywords from the earliest available date till 10th February 2021 restriction on language. Additional sources such as Google Scholar, major journals, unpublished studies, conference proceedings, and cross-references were explored. Information curated for data extraction included methodology, population, sample size (number of teeth), number of root canals, and type of root canal configuration (RCC). Thirty-seven articles were selected with a total of 12,393 permanent mandibular second molar teeth. In the mesial root, Type IV canal configuration with 37.3% was more frequent, having two canals with 70.4%. In the distal roots, one canal was more prevalent with 77% occurrence, and Type I canal configuration was more frequent with 85.2%. Comprehensive knowledge of tooth anatomy and root canal morphology is crucial to root canal treatment. Therefore, an understanding of the canal configuration and anatomy is necessary for the dentist to enhance successful endodontic treatment. Our systematic review findings reveal a wide variety of possible canal configurations among permanent mandibular second molar, while the number of canals ranged from 1 to 5 in number. The evidence is intended to help dental practitioners to avoid mishaps such as perforation and missing canals and anticipation of potential complications during treatment.
Keywords: Canal configuration; permanent mandibular second molar; root canal; Vertucci classification
|How to cite this article:|
Joshi PS, Shetty R, Sarode GS, Mehta V, Chakraborty D. Root anatomy and canal configuration of human permanent mandibular second molar: A systematic review. J Conserv Dent 2021;24:298-306
|How to cite this URL:|
Joshi PS, Shetty R, Sarode GS, Mehta V, Chakraborty D. Root anatomy and canal configuration of human permanent mandibular second molar: A systematic review. J Conserv Dent [serial online] 2021 [cited 2022 May 18];24:298-306. Available from: https://www.jcd.org.in/text.asp?2021/24/4/298/335755
| Introduction|| |
Endodontic treatment's primary goal is to provide curative measures for pulpal inflammatory responses, causing pain and discomfort. Root canal therapy aims to thoroughly clean and shape all pulp spaces and their complete obturation with a biocompatible filling material. However, the root canal anatomy complexity presents clinical challenges and difficulties that often jeopardize such therapy's primary goal., Root canal treatment (RCT) involves a series of steps for its successful elimination and prevention of microbial contamination.
From the reported reasons for root canal therapy failure in the literature, one explanation for failure could be the existence of an untreated canal. A canal can be left unnoticed because of the dentist's ignorance and lack of experience. It can be due to the complexity of the root canal morphology. Thus, before undertaking endodontic therapy, it is essential to visualize and know the internal anatomy relationships. It becomes a necessity to evaluate the case through periapical radiographs at different angles. Peters et al. reported that the type of canal geometry before cleaning and shaping procedures holds more influence in treatment success than the instrumentation technique alone.
Whether it is an old dated work by Hess and Zurcher or the latest studies reported, all have presented data on the complexity of root canals' anatomical structure. It is well known to the practitioners that a root with a single tapering canal terminating in one foramen, according to the law, remains an exception. Instead, studies have shown numerous additional canals, deltas, loops, intercanal connections, fins, multiple foramina, and C-shaped canals increasing the difficulty level of the treatment and compromising the treatment success.
The pulp canal system is complex, and it can branch, split, and rejoin canals. To date, many classifications have been listed based on the canal morphology. Weine classified the network of root canals into four specific forms in any root. Using the clearing technique, Vertucci in 1984 divided the root canal structures into eight forms. Another study reported on Burmese teeth added seven forms to preceding classifications. Sert and Bayirli introduced 15 different types of root canal systems to the Vertucci list and ended up with 23 types of root canal systems in total.
While understanding the canal morphology, it becomes essential to look into the technique used for assessing this information. Many studies have employed various techniques to determine root canal morphology, including clearing technique, radiography, micro-computed tomography (micro-CT), and cone-beam computed tomography.(CBCT) To date, voluminous studies have been published reporting data on the canal morphology according to Vertucci classification. According to Vertucci classification, a systematic review was conducted considering both, in vitro and in vivo studies on permanent mandibular second molar to have a pooled prevalence on the canals and classification type.
- P – Population: Human permanent mandibular second molar
- O – Outcomes: Root canal morphology according to Vertucci classification
- S – Study Design: In vitro and in vivo studies.
What is the prevalence of root anatomy and canal configuration in permanent mandibular second molar based on Vertucci classification?
An exhaustive literature search was conducted to identify root anatomy and canal configuration in permanent mandibular second molar based on Vertucci classification. Online electronic databases such as PubMed-Medline, Embase, Scopus, and Cochrane Library were searched from the earliest available date till February 10, 2021 without restriction on language. Additional sources such as Google Scholar, major journals, unpublished studies, conference proceedings, and cross-references were explored. Contact with authors was done for any unpublished studies. A detailed search strategy is given in [Figure 1] and tailored to each database when necessary.
- All in vitro and in vivo studies including root anatomy and canal configuration of human permanent mandibular second molar based on Vertucci classification were included
- Case reports, letters, and reviews were not included in the search
- Studies assessing root anatomy and canal configuration according to classifications other than Vertucci were excluded.
Screening and selection
The papers were independently scanned by two reviewers (VM and PJ), first by the title and abstract. Reviews, commentary, or clinical trials were not included in the search. If the search keywords were present in the title and/or the abstract, the papers were selected for full-text reading. Papers without abstracts but with titles suggesting that they were related to the objectives of this review were also selected to screen the full text for eligibility. After selection, full-text papers were read in detail by two reviewers (VM and PJ). Those papers that fulfilled all of the selection criteria were processed for data extraction. Two reviewers (VM and PJ) hand searched the reference lists of all selected studies for additional relevant articles. Disagreements between the two reviewers were resolved by discussion. If a disagreement persisted, the judgment of a third reviewer (RJ) was considered decisive.
Risk of bias
Two reviewers (VM and PJ) assessed the quality of the included studies. Checklist for Reporting In vitro Studies Guidelines were used to assess risk of bias. Any disagreement was resolved by consensus.
Information curated for data extraction included methodology, population, sample size (number of teeth), number of root canals, and type of root canal configuration (RCC).
The systematic review was registered with the International Prospective Register of Systematic Reviews on January 23, 2021, which was in accordance with the guidelines (Registration Number CRD42021227881).
| Results|| |
The reporting is based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses algorithm.
Search selection and results
The PubMed-Medline, Embase, Scopus, Cochrane Library, and additional sources identified 461 search results, of which 345 were duplicates. The remaining 116 unique studies were screened for the titles and abstracts, and fifty articles were selected for full-text screening [Figure 2]. A total of 37 articles,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, that matched the eligibility criteria, were processed for data extraction.
|Figure 2: Flowchart summarizing the article selection process. n: Number of studies|
Click here to view
Thirty seven studies,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, identified a total of 12,393 permanent mandibular second molar teeth among varied populations. Eighteen studies were in vivo,,,,,,,,,,,,,,,,,, while the rest 19 were in vitro/ex vivo studies.,,,,,,,,,,,,,,,,,, Nineteen studies used CBCT technique,,,,,,,,,,,,,,,,,,, two studies used micro-CT,, and other studies used various clearing techniques in their methodology.,,,,,,,,,,,,,,, Gender comparison was done in eight studies.,,,,,,, In contrast, one study used the age group as a comparing factor. Two studies used different population subgroups to compare the anatomy of the molars between different ethnicity., Seven studies,,,,,,51] were divided based on the number of roots present in the permanent mandibular second molar and three studies reported the presence of additional root.,, In comparison, six studies presented data according to the anatomical variation in root shape.,,,,, One study presented with single-rooted mandibular molars [Table 1].
All the 37 studies presented data on canal configuration of mandibular second molar based on Vertucci classification.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Out of which, 34 studies,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, reported frequency of occurrence of RCC separately for mesial root and distal roots. The concurred data for most of these studies included both the percentage of occurrence as well as the number of cases for such canal types seen in the sample. For few studies, only the percentage of occurrence was given, and the exact value of the number of teeth for each specific canal type was calculated from the given percentage and sample size (number of teeth) taken for the study. Our results demonstrate Vertucci Type IV as the most common RCC for mesial root with 37.3% occurrence, followed by Type II with 34.6%. For the distal root, Type I was most common, with 85.2%. All other types of RCC in distal root were infrequent [Table 2].
|Table 2: Root canal configuration based on vertucci classification in mesial and distal root separately|
Click here to view
Studies,,,,,,,,,,, reported findings where the percentage of various types of RCC for mandibular molar are given in totality and not segregated for each root. One rooted molar with Type I canal configuration is seen most commonly in all of them [Supplementary Table 1].
Twenty-one studies,,,,,,,,,,,,,,,,,,,, presented with the findings on the [Supplementary Table 2] shows number of canals in permanent mandibular second molar. Nine studies,,,,,,,, with a total of 4480 teeth presented data on number of roots separated for mesial and distal roots. In the mesial root, two canals were most commonly seen with 70.4%, followed by one canal with 11.5%. In the distal root, 1 canal was most prevalent with 77% [Table 3].
Fifteen studies had canal configuration other than the eight types of Vertucci classification.,,,,,,,,,,,,,, The findings in these studies were random, and no distinct pattern was noted. The frequency of occurrence of these RCC outside of Vertucci classification was low. These variations were seen more in certain groups of the population. It was noted that the Chinese population had a maximum percentage of occurrence of RCC, which could not be classified by Vertucci classification [Supplementary Table 3].
| Discussion|| |
For successful RCT, prior knowledge of anatomy is essential. The morphology of root anatomy can vary depending on the age, population, ethnicity, gender, number of teeth, and methodology. The selected articles' reporting presented diverse population groups with different characteristics and sample sizes. The study designs showed a near equal trend for both in vivo as well as in vitro studies. While comparing the methodologies, it was noted that clearing technique and staining were used as a methodology by in vitro studies. In contrast, contemporary studies were mostly in vivo and used three-dimensional (3D) imaging techniques commonly. No distinct difference was noted in the findings due to variation in methodology.
The most common feature reported by available literature on mandibular molar was its canal configuration. In 34 studies,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, the data for each root was presented in the form of percentages according to the sample size (number of teeth) of the study. Thus, a study with a smaller sample size (number of teeth) showed a higher percentage for a particular type even though the actual number of the said type was low. Vice-versa occurred in studies with a large sample size (number of teeth). Hence, it would have been difficult to draw a definite conclusion among the myriad of data extracted from the studies. Thus, to interpret the data properly, each type's total percentage was calculated for mesial and distal roots separately. The calculated percentage showed Type IV as the most frequent RCC, closely followed by Type II for mesial roots. The distal root presented a higher prevalence of Type I. Gaêta-Araujo et al. and Plotino et al. in their study reported a similar finding of higher prevalence of type IV followed by type II for mesial and type I for distal roots., However, the study by Zare Jahromi et al. revealed type III as the most prevalent RCC for mesial root followed by type II; however, the prevalent RCC for distal root was type I, same as in our study.
The similar theme of prevalence in the findings of the studies gives us an overall insight into the canal configuration of mandibular second molars. However, our review also reports other canal configuration types even though they are infrequent. Thus, to get a comprehensive idea about mandibular second molars' canal configuration, these findings should also be considered. The occurrence of type VIII canal configuration was rare and noted in only a few studies on the Chinese, Burmese, Turkish, Jordan, Indian, and Iranian populations.
RCC undefined by Vertucci classification was also found in several studies. The different RCCs were more in occurrence for single-rooted and third rooted molars. Even though such RCCs were in small percentages and were very low compared to the other canal configuration, it explains how varied the canal configuration of permanent mandibular second molar can be and warrants further investigation [Supplementary Table 3].
[Supplementary Table 3] displays the occurrence of these RCCs according to the population. The studies on Chinese, Turkish, and Thai people reported maximum cases indicating a wide variation in RCC. The Chinese population showed the highest percentage in RCC variation, with more than 20% of the population lying outside the Vertucci classification. An overview of the global map [Figure 3] demonstrates the correlation between varied RCC presence outside of Vertucci classification with the geographical location of specific populations. This provides us with an insight into variation in RCC based on demographics. However, it should be acknowledged that these values can also be influenced by the gender, age, and sample size (number of teeth) collected.
|Figure 3: Geographic incidence of root canal configuration undefined by Vertucci classification in human permanent mandibular second molar|
Click here to view
Among anatomical variations in shape, canals with C, O, and conical shapes were being reported. The occurrence of C-shaped canals was most frequent. This finding commensurate with the results of a study by Roy et al. that C-shaped canals are one of the most common reported variations in mandibular second molar. Shemesh et al. reported that C-shaped canals were reported rarely in teeth other than the second mandibular molar, and the prevalence of C-shaped canals in their study was 4.6%. According to the study conducted by Wadhwani et al., prevalence of C-shaped canals in mandibular second molars was found to be 9.7%; slightly greater than the mandibular third molars. Roy et al. in their research noted a great variability in C-shaped canal configuration according to ethnicity and gender.
The presence of a number of canals was the most common finding reported in the studies. A strategy similar to RCC was followed to find the number of canals most frequently occurring in the mandibular second molar. For mesial root, two canals were found to be most frequent and one canal for distal root. Thus, in a two rooted permanent mandibular second molar, three canals are noted, 2 in mesial and 1 in distal. Manning reported similar results in their study stating that, in two rooted mandibular molars, more than 90% of distal roots have one canal and more than 70% of mesial roots have two canals.
Most studies reported two rooted mandibular second molars. Only a few reported a third root or an additional root. Zare Jahromi et al. and Manning report a similar finding with mandibular molars having two roots frequently., Three rooted molars showed mostly Vertucci type I configuration. Single-rooted mandibular molars were noted to have only one canal but with anatomic variations in the root shape and RCC of which C-shaped roots and type 1 canal configuration were most frequently occurring.
Lack of knowledge of internal structure can lead to failure in endodontic treatment. Thus, every tooth should be judiciously analyzed based on ethnicity, race, and population, keeping in mind the peculiarities in the population around us. Gaêta-Araujo et al. in their study on RCT errors revealed that technical errors were most likely, for type IV RCC. This was due to two-dimensional imaging adopted for RCT that can cause overlap of the two canals causing clinicians to confuse it with type I. Moreover, as RCC's complexity increased chances of RCT errors also increased. Mandibular second molar presents with the high frequency of C-shaped canals, and a wide range of unclassified complex RCC variation. Furthermore, its mesial root most frequently occurs in type IV canal configuration. Thus, every tooth should be judiciously analyzed and approached with prior knowledge carefully.
No exclusion criteria were kept for the type of method used in the study, and all study's findings of both in vivo and in vitro/ex vivo methodology have been discussed in this review. Thus, a discrepancy in reporting of the anatomy could be present between clearing techniques and 3D techniques. Furthermore, the included were not about a specific population, ethnicity, or geographic distribution, but across the globe, so the changes in the findings may be present due to certain genetic predispositions. The sample size (number of teeth) of the studies was also varied. Hence, the percentages of studies with a small sample size (number of teeth) were higher even though we tried to get a conclusive finding by calculating the percentages. Some studies did not segregate the data into mesial and distal roots.
| Conclusion|| |
Comprehensive knowledge of tooth anatomy and root canal morphology is crucial in the success of RCT. Therefore, an understanding of the canal configuration and anatomy is necessary for the dentist to enhance the chance of successful endodontic treatment. Our systematic review findings reveal a wide variety of possible canal configurations among permanent mandibular second molar, while the number of canals ranged from 1 to 5 in number. No noted difference was seen in the comparative studies. Among the various population, type IV was commonly seen in mesial roots, and type I in distal roots. Most mandibular molars were two rooted and had three canals present. Mesial roots had two canals, while distal roots contained only 1 canal. Rarely, canal configuration other than Vertucci type was noted, and the majority of different types were seen among Chinese population groups. The evidence is intended to help dental practitioners to avoid mishaps such as perforation and missing canals and anticipation of potential complications during treatment.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr. Vini Mehta
Department of Public Health Dentistry, People's College of Dental Sciences and Research Centre, Bhopal, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]