Abstract
Mandibular incisors and canines show variations in their root canal anatomy. It is imperative to be aware of these variations to lower the frequency of missed canals. The objective was to systematically review the existing studies to recognize the root and root canal anatomy of the mandibular incisors and canines among the population of various geographical locations, as studied by different methods. This systematic review was registered in the International Prospective Register of Systematic Reviews database under the number CRD42020185146. An exhaustive search was undertaken in three electronic databases – MEDLINE PubMed, EBSCOhost, and Google Scholar – along with hand-searching for the identification of studies. Studies were selected following strict inclusion and exclusion criteria. Selected studies were scored using the Joanna Briggs Institute Critical Appraisal tool for prevalence studies to determine the risk of bias. This review included data from 26 countries including the analysis of 71,404 mandibular anterior teeth. The risk of bias of all included studies was either low or moderate. Overall, it was seen that the percentage of second canals was higher in lateral than in central incisors. Mandibular canines occasionally showed the presence of two roots. Deviations in anatomy were high in the Middle Eastern European countries and the Indian subcontinent. Limitations are as follows: lack of homogeneity across data reported in the studies concerning the methods used to study the root canal anatomy. Diversities seen in the root canal configurations of mandibular incisors and canines vary according to ethnicity, and thus, one must have a thorough knowledge before commencing endodontic treatment.
Keywords: Anatomy, canal configuration, mandibular canines, mandibular incisors, root canal systematic review
INTRODUCTION
Human teeth have an extremely complicated pulp space anatomy. Each tooth in the dental arch has unique anatomy which shows high degree of variability among populations. Mandibular incisors and canines are known to have a single root and one or two canals. However, often, they show variations in their root canal anatomy such as the presence of an extra lingual canal. There is a high prevalence of a second canal in the mandibular incisors and canines.[1]
It is critical to know these variations in the anatomy to lower the frequency of missed canals during endodontic treatment, as this can cause the failure of root canal treatment. A periapical lesion is 4.38 times more likely to occur in a tooth with a missed canal.[2] In a vital tooth, a missed canal contains pulp tissue which may cause pain at first and then may get infected. In case of a nonvital tooth, the canal that is missed may be infected and thus would lead to persistence of infection and failure of treatment. Therefore, complete debridement and disinfection of the root canal system is critical to a successful endodontic treatment outcome. The knowledge of canal systems along with their frequent variations is of utmost importance for the success of root canal treatment.
In addition, root canal anatomy configurations may vary according to ethnicity,[3,4] sex,[5,4,5,6,7] and age.[8] Several methods to study the root canal anatomy have been published in the literature which includes radiographic methods such as intraoral periapical (IOPA) radiograph - film[9] digital IOPA,[10] cone-beam computed tomography (CT),[11] and micro-CT,[12] as well as nonradiographic methods such as tooth clearing and canal staining technique,[13] modeling,[14] and the sectioning technique.[10,15]
Root canal anatomy was studied[16] and then classified by various authors to enable standardization and reproducibility.[17,18,19,20] At present, several studies on the different types of root canal anatomy seen in the mandibular incisors and canines are available in the literature. These studies have origins in different countries and use different methods to study root canal anatomy. The systematic review aims to combine these existing studies to understand the variations in the root and root canal configurations of human permanent mandibular incisors and canines among the population of various geographical locations, as studied by different methods.
MATERIALS AND METHODS
This systematic review was registered in the International Prospective Register of Systematic Reviews database under CRD42020185146. It is formulated and written in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines, 2020 [Supplemental Table 1].[21]
Supplemental Table S1.
Filled PRISMA checklist, 2020
| Section and topic | Item # | Checklist item | Location where the item is reported (Page No.) |
|---|---|---|---|
| Title | |||
| Title | 1 | Identify the report as a systematic review. | 1 |
| Abstract | |||
| Abstract | 2 | See the PRISMA 2020 for Abstracts checklist. 21 | 1 |
| Introduction | |||
| Rationale | 3 | Describe the rationale for the review in the context of existing knowledge. | 1 |
| Objectives | 4 | Provide an explicit statement of the objective (s) or question (s) the review addresses. | 2 |
| Methods | |||
| Eligibility criteria | 5 | Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses. | 3 |
| Information sources | 6 | Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted. | 2 |
| Search strategy | 7 | Present the full search strategies for all databases, registers and websites, including any filters and limits used. | 2 |
| Selection process | 8 | Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process. | 3 |
| Data collection process | 9 | Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process. | 3 |
| Data items | 10a | List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect. | 3 |
| 10b | List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information | 3, 7 | |
| Study risk of bias assessment | 11 | Specify the methods used to assess risk of bias in the included studies, including details of the tool (s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process. | 3 |
| Effect measures | 12 | Specify for each outcome the effect measure (s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results. | 3 |
| Synthesis methods | 13a | Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis. | 3 |
| 13b | Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions. | 3, 7 | |
| 13c | Describe any methods used to tabulate or visually display results of individual studies and syntheses. | 3 | |
| 13d | Describe any methods used to synthesise results and provide a rationale for the choice (s). If meta-analysis was performed, describe the model (s), method (s) to identify the presence and extent of statistical heterogeneity, and software package (s) used. | 3 | |
| Reporting bias assessment | 14 | Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases). | 3 |
| Certainty assessment | 15 | Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome. | 3 |
| Results | |||
| Study selection | 16a | Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram | 4 |
| 16b | Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded. | 3 | |
| Study characteristics | 17 | Cite each included study and present its characteristics. | 5-7, 11-13 |
| Risk of bias in studies | 18 | Present assessments of risk of bias for each included study. | 4 |
| Results of individual studies | 19 | For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots. | 5-7, 11-13 |
| Results of syntheses | 20a | For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies. | 3, 4, 7 |
| 20b | Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect. | 3 | |
| Reporting biases | 21 | Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed. | 3, 4 |
| 22 | Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed. | 3, 4, 7 | |
| Discussion | |||
| Discussion | 23a | Provide a general interpretation of the results in the context of other evidence. | 4, 7, 9 |
| 23b | Discuss any limitations of the evidence included in the review. | 9 | |
| 23c | Discuss any limitations of the review processes used. | 9, 14 | |
| 23d | Discuss implications of the results for practice, policy, and future research. | 14 | |
| Other information | |||
| Registration and protocol | 24 | Provide registration information for the review, including register name and registration number, or state that the review was not registered. | 2 |
| Support | 25 | Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review. | 14 |
| Competing interests | 26 | Declare any competing interests of review authors. | 14 |
| Availability of data, code, and other materials | 27 | Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review. | 3 |
The question in focus was, “What is the prevalence of Vertucci canal configuration with additional types in human mandibular incisors and canines as studied by various techniques and in different geographical locations?” It followed the PCC[22] – Population (P), Condition (C), Context (C) criteria for prevalence studies, where the Population (P) was human mandibular incisors and canines; Condition (C) was Vertucci types of canal configuration with its additional modifications, and Context (C) was the various geographical locations and different study designs used to study it.
Search strategy
A concept table was made based on the PCC[22] criteria. It included the key concepts, controlled vocabulary terms (Medical Subject Headings Terms), as well as free-text terms. These terms were used to formulate a search strategy. The terms were combined using suitable Boolean operators (AND, OR, and NOT). A similar search strategy was implemented in all the three electronic database searches – The National Library of Medicine (MEDLINE PubMed), EBSCOhost, Google Scholar – for the identification of studies for this review. Table 1a summarizes the terms and filters used in each database. The full electronic search strategy of the MEDLINE PubMed database is presented in Supplemental Figure 1 (4.9MB, tif) . Hand-searching of the above databases was also done. References were checked of all eligible studies for other relevant studies. The databases were searched between 1965 and September 30, 2020, using the aforementioned search strategy. In addition, hand-searching of two scientific journals (Journal of Endodontics and International Endodontic Journal) was carried out.
Table 1a.
Terms and filters used in each electronic database
| Database | Terms used | Filters |
|---|---|---|
| PubMed | ((((root canal anatomy) OR (root canal morphology)) OR (root canal configuration)) OR (canal morphology)) OR (root canal system) AND (((((((((((((((((((((((human permanent mandibular incisors and mandibular canines) OR (mandibular anterior teeth)) OR (permanent dentition)) OR (human permanent teeth)) OR (human permanent mandibular incisors)) OR (permanent mandibular incisors)) OR (human permanent mandibular canines)) OR (permanent mandibular canines)) OR (mandibular incisor)) OR (mandibular canines)) OR (anterior teeth)) OR (mandibular permanent anterior teeth)) OR (mandibular incisors)) OR (human anterior teeth)) OR (human mandibular canines)) OR (lower incisors)) OR (human mandibular anterior teeth)) OR (lower anterior teeth)) OR (mandibular central and lateral incisors)) OR (permanent teeth)) OR (mandibular permanent teeth)) OR (central and lateral mandibular incisors)) OR (mandibular canine)) AND ((((((Vertucci’s canal configuration) OR (Vertucci’s classification)) OR (root canal pattern)) OR (Vertucci)) OR (Weine classification)) OR (Gulabivala’s modification for Vertucci’s classification)) | N/F Search - “All fields” |
| EBSCOhost | ((((root canal anatomy) OR (root canal morphology)) OR (root canal configuration)) OR (canal morphology)) OR (root canal system) AND (((((((((((((((((((((((human permanent mandibular incisors and mandibular canines) OR (mandibular anterior teeth)) OR (permanent dentition)) OR (human permanent teeth)) OR (human permanent mandibular incisors)) OR (permanent mandibular incisors)) OR (human permanent mandibular canines)) OR (permanent mandibular canines)) OR (mandibular incisor)) OR (mandibular canines)) OR (anterior teeth)) OR (mandibular permanent anterior teeth)) OR (mandibular incisors)) OR (human anterior teeth)) OR (human mandibular canines)) OR (lower incisors)) OR (human mandibular anterior teeth)) OR (lower anterior teeth)) OR (mandibular central and lateral incisors)) OR (permanent teeth)) OR (mandibular permanent teeth)) OR (central and lateral mandibular incisors)) OR (mandibular canine))) AND ((((((Vertucci’s canal configuration) OR (Vertucci’s classification)) OR (root canal pattern)) OR (Vertucci)) OR (Weine classification)) OR (Gulabivala’s modification for Vertucci’s classification)) | Limiters - Full-text expanders - Apply equivalent subjects Search modes - Boolean/Phrase |
| Google Scholar | Root canal anatomy OR root canal morphology OR root canal configuration OR canal morphology OR root canal system AND human permanent mandibular incisors and mandibular canines AND Vertucci’s canal configuration | N/F |
N/F: No filter
Study selection
Initially, the titles and abstracts of the studies were screened and labeled as “appropriate” or “inappropriate.” This was done according to the previously decided inclusion and exclusion criteria [Table 1b]. Following this, the full text of all the appropriate studies was assessed for eligibility according to the same criteria.
Table 1b.
Inclusion and exclusion criteria
| Inclusion criteria | Exclusion criteria |
|---|---|
| Studies using all nonradiographic methods such as tooth clearing and canal staining technique, modeling, and sectioning technique to investigate the root canal anatomy | Reviews and expert opinions |
| Studies using all radiographic methods such as IOPN radiograph - manual and digital, CBCT, and micro-CT system to investigate the root canal anatomy | Only abstracts |
| Studies done on the root canal anatomy of human permanent mandibular incisors and canines in various world populations | Animal studies |
| Publications in English with full text available in hard or soft copy | Articles where the outcome of the study was not clearly specified |
| Articles published between 1965 and September 2020 | Studies done on deciduous mandibular incisors and mandibular canines |
CT: Computed tomography, CBCT: Cone-beam CT, IOPA: Intraoral periapical
Data extraction
Two review authors independently collected data using a specially designed data extraction form. The data extraction form had undergone a pilot test using a few articles. Using those results, it was modified before its usage. Data where the root canal anatomy was studied but was not presented as per any classification system were extracted, but it was included only if both the review authors could convert the data presented into a classification system (provided there was sufficient data given to enable conversion) and if both the review authors independently had the same result. Disagreements were resolved by discussion until a consensus was reached. For each of the included studies and each tooth category, data were extracted under the following headings: author, year of publication, country, method, number of subjects (with their age and gender, if specified), number of teeth, number of roots, Vertucci classification, additional modifications of Vertucci classification (given by Gulabivala et al.,[20] Sert and Bayirli,[6] and Kartal and Yanikoğlu[19]), and the risk of bias.
Scientific merit assessment
The quality of the selected studies was checked using the checklist from the Joanna Briggs Institute (JBI) Critical Appraisal tool for systematic reviews of prevalence studies [Supplemental Table 2].[23] The included studies were evaluated by two endodontists, who scored each JBI question as yes (score 2), no (score 0), unclear (score 1), or not applicable. An interrater reliability test was performed. Any differences in opinion between the evaluators were discussed till a consensus was reached.
Supplemental Table 2.
Joanna Briggs Institute critical appraisal form
| JBI Critical Appraisal tool for systematic reviews of prevalence studies questions | |||||
|---|---|---|---|---|---|
| Number | JBI Question | Yes | No | Unclear | Not applicable |
| 1 | Was the sample frame appropriate to address the target population? | ||||
| 2 | Were study participants sampled in an appropriate way? | ||||
| 3 | Was the sample size adequate? | ||||
| 4 | Were the study subjects and the setting described in detail? | ||||
| 5 | Was the data analysis conducted with sufficient coverage of the identified sample? | ||||
| 6 | Were valid methods used for the identification of the condition? | ||||
| 7 | Was the condition measured in a standard, reliable way for all participants? | ||||
| 8 | Was there appropriate statistical analysis? | ||||
| 9 | Was the response rate adequate, and if not, was the low response rate managed appropriately? | ||||
JBI: Joanna Briggs Institute
When there was no sample size calculation done in the study, we conducted our sample size analysis using the given formula.[24] The prevalence values of Type I root canal anatomy[13] of previous studies[4,6,13,25,26] using tooth clearing and canal staining technique as a method of study (gold standard) were used for calculating the adequate sample size. The minimum sample size required was found to be 207 teeth for mandibular central incisors, 246 teeth for mandibular lateral incisors, and 113 teeth for mandibular canines. A sample size lesser than these values for any one of the mandibular anterior teeth was considered to be inadequate.
The final score of each study applied to the JBI questions was calculated. Then, the risk of bias of each study was categorized according to the final score as “high” (score below 8), “moderate” (score 8–12), or “low” (score 13–16).
RESULTS
Included studies
An exhaustive electronic database search resulted in 225 articles on PubMed, 646 articles on EBSCOhost, 357 articles from Google Scholar search, and 24 articles through a hand search. Mendeley software (Version 1.19.4, Elsevier, London, United Kingdom) was used for duplicate removal of the articles. After removing duplicates, 1130 articles were evaluated. From these, 1012 articles were excluded because they were labeled as “inappropriate” based on titles and abstracts. After a full-text analysis for eligibility, 33 articles were excluded [Supplemental Table 3] because they did not meet the inclusion criteria. Therefore, the study selection process resulted in 85 full-text articles [Figure 1].
Supplemental Table 3.
A list of all the excluded studies from this systematic review along with the reason for their exclusion
| Study | Reason |
|---|---|
| Aggarwal, 2016 | Root canal anatomy is not studied |
| Agholor et al., 2020 | No details of the canal configuration mentioned-like the number of foramina. cannot be classified |
| Ahmad, 2015 | Review article |
| Aldawla et al., 2019 | Review article |
| Amreen et al., 2020 | Data is mismatched |
| Andrei et al., 2011 | Outcome of the study not clearly specified with respect to any type of classification system |
| Barker et al., 1973 | Outcome of the study not clearly specified with respect to any type of classification system |
| Bellizzi et al., 1983 | Root with two canals are not categorized as to whether the canals exit by a common apical foramen or separate apical foramina. Cannot be classified |
| Beshkenadze et al., 2015 | Each type of Vertucci classification is not specified for a particular tooth type |
| Haghanifar et al.,2017 | Each type of Vertucci classification is not given as a separate percentage |
| Hession, 1977 | Details of the apical foramina not given in the roots with multiple canals; therefore, not possible to deduce Vertucci classification |
| Jaiswal et al., 2013 | Root canal anatomy is studied |
| Kaffe et al., 1985 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Kayaoglu et al.,2015 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Kerekes et al., 1977 | Number of root canals neither studied nor classified |
| Kulkarni et al.,2019 | Percentage of prevalence of each type of Vertucci classification in a particular tooth not mentioned |
| Mauger et al., 1998 | Number of root canals neither studied nor classified |
| Mazzi-Chaves et al.,2020 | Number of root canals neither studied nor classified |
| Monsarrat et al.,2016 | No details of the number of apical foramina mentioned, therefore not possible to deduce Vertucci classification |
| Nattress et al.,1991 | Outcome of the study not clearly specified with respect to any type of classification system |
| Neelakantan et al.,2010 | Percentage of prevalence of each type of Vertucci classification in a particular tooth not mentioned |
| Neo et al., 1990 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Oliveira et al., 2009 | Number of root canals neither studied nor classified |
| Prado et al., 2016 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Razumova et al.,2018 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Shaikh et al., 2014 | Details of the apical foramina not given in the roots with two canals; therefore, not possible to deduce Vertucci classification |
| Tiku et al., 2005 | Root canal anatomy not studied |
| Tsujimoto, 2009 | Review article |
| Versiani et al., 2013 | Number of root canals neither studied nor classified |
| Vertucci, 2005 | Review article |
| Wang et al., 2018 | Number of root canals neither studied nor classified |
| Xu et al., 2019 | Number of root canals neither studied nor classified |
| Zhu et al., 2020 | Teeth with only double canals are studied for the presence of bilateral symmetry, not studied the root canal anatomy |
Figure 1.
A flow diagram showing the process from identification to the inclusion of studies
Results of Cohen Kappa interrater reliability performed for the studies submitted to the JBI questionnaire were above 0.7 [Supplemental Table 4]. The risk of bias of each question as answered for all the studies is depicted graphically [Figure 2]. Figure 3 shows the percentage of studies with a moderate and low risk of bias. The average JBI score for the 85 included studies was 84.85%.
Supplemental Table 4.
Joanna Briggs Institute Critical Appraisal tool for systematic reviews of prevalence studies questions
| JBI question | Cohen Kappa interrater reliability between evaluators |
|---|---|
| Was the sample frame appropriate to address the target population? | 0.96 |
| Were study participants sampled in an appropriate way? | 0.92 |
| Was the sample size adequate? | 0.81 |
| Were the study subjects and the setting described in detail? | 0.87 |
| Was the data analysis conducted with sufficient coverage of the identified sample? | 0.83 |
| Were valid methods used for the identification of the condition? | 1.00 |
| Was the condition measured in a standard, reliable way for all participants? | 0.78 |
| Was there appropriate statistical analysis? | 0.94 |
| Was the response rate adequate, and if not, was the low response rate managed appropriately? | Not applicable |
JBI: Joanna Briggs Institute
Figure 2.
Risk of bias of each question as answered for all the studies represented graphically
Figure 3.
Percentage of studies showing a moderate and low risk of bias
The present systematic review includes data of at least 71,404 mandibular anterior teeth (27,852 mandibular central incisors, 27,808 mandibular lateral incisors, and 15,744 mandibular canines) acquired from 26 countries, namely Australia, Brazil, China, Egypt, Germany, Greece, India, Indonesia, Iran, Iraq, Italy, Israel, Japan, Jordan, Malaysia, Myanmar, Pakistan, Poland, Portugal, Saudi Arabia, Serbia, Sri Lanka, Syria, Taiwan, Turkey, and the United States of America, studied by various radiographic and nonradiographic methods.
Root and root canal configuration types
Table 2 summarizes the data extracted from the included studies for mandibular central incisors. Table 3 summarizes the studies that have shown modifications in their root canal configuration types other than those given by Vertucci. Tables 4 and 5 summarize all the data extracted from the included studies for mandibular lateral incisors and canines, respectively. Mandibular incisors show a greater variation in the root canal configuration rather than in the number of roots, with a predominance of Vertucci Type I configuration followed by Type III and in some cases Type II. The overall range of these anatomical deviations seen in mandibular incisors at different geographical locations is – Type II, 0.45%–40.1%; Type III, 0.4%–55.9%; Type IV, 0.1%–15.4%; and Type V, 0.05%–17.9%. Mandibular canines show a greater prevalence of two roots (0.2%–12.08%) and only sometimes show the presence of two canals in a single root (Type II, 0.5%–15.5%; Type III, 0.4%–17.5%; Type IV, 0.15%–12.8%; and Type V, 0.24%–6.94%).
Table 2.
Root and root canal anatomy of mandibular central incisors
| Author, year | Methodology | Demographics | Root and root canal anatomy | Risk of bias | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||||||||||||
| Mandibular central incisor | Country | Number of subjects | Men/women | Age (years) | Number of teeth | Number of roots (%) | Vertucci classification (%) | |||||||||||
|
|
|
|||||||||||||||||
| 1 | 2 | I | II | III | IV | V | VI | VII | VIII | Other‡ | ||||||||
| Ajinkya MP, 2017 | CBCT | India | NA | NA | NA | 100 | NA | NA | 57 | 12 | 24 | 4 | Nil | Nil | Nil | Nil | 3 | Moderate |
| Al-Fouzan, 2012 | Tooth clearing and canal staining | Saudi Arabia | NA | NA | NA | 40 | 100 | Nil | 70 | Nil | 30 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Al-Qudah,* 2006 | Tooth clearing and canal staining | Jordan | NA | NA | NA | 450 | 100 | Nil | 73.8 | 10.9 | 6.7 | 5.1 | 3.6 | Nil | Nil | Nil | Nil | Low |
| Almeida-Gomes,* 2017 | CBCT | Brazil | NA | NA | NA | 148 | NA | NA | 72.3 | 25.67 | Nil | 2.03 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Altunsoy, 2014 | CBCT | Turkey | 827 | 410/417 | 14-70 | 1582 | NA | NA | 84.45 | 0.45 | 0.8 | 4.25 | 10.05 | Nil | Nil | Nil | Nil | Low |
| Aminsobhani, 2013 | CBCT | Iran | 400 | NA | NA | 632 | 100 | Nil | 72.7 | 11.3 | 4.7 | 7.7 | 3.6 | Nil | Nil | Nil | Nil | Low |
| Arslan, 2015 | CBCT | Turkey | 101 | 47/54 | 10-70 | 184 | 100 | Nil | 51.9 | 4.3 | 41.6 | Nil | 0.5 | Nil | Nil | Nil | 1.6 | Low |
| Assadian,* 2016 | Digital radiography | Iran | NA | NA | NA | 76 | NA | NA | 52.6 | 1.3 | 31.6 | Nil | 14.5 | Nil | Nil | Nil | Nil | Low |
| Sectioning | 76 | NA | NA | 69.7 | 5.3 | 25 | Nil | Nil | Nil | Nil | Nil | Nil | ||||||
| CBCT | 76 | NA | NA | 43.4 | 5.3 | 50 | Nil | 1.3 | Nil | Nil | Nil | Nil | ||||||
| Aung, 2020 | Tooth clearing and canal staining | Myanmar | NA | NA | NA | 58 | NA | NA | 72.41 | 1.72 | 17.24 | Nil | Nil | Nil | Nil | Nil | 8.62 | Low |
| Basha, 2018 | CBCT | Egypt | 100 | 50/50 | 15-60 | 200 | NA | NA | 85.5 | Nil | 11 | Nil | 3.5 | Nil | Nil | Nil | Nil | Low |
| Baxter, 2020 | CBCT | Germany | 302 | 116/186 | 18-78 | 604 | NA | NA | 76.15 | 22 | Nil | 0.65 | 1.15 | Nil | Nil | Nil | Nil | Low |
| Benjamin,* 1974 | Radiograph | USA | NA | NA | NA | 364 | NA | NA | 58.6 | 40.1 | Nil | 1.3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Boruah,* 2010 | Tooth clearing and canal staining | India | NA | NA | NA | 480 | NA | NA | 63.75 | 7.08 | 22.92 | Nil | 6.25 | Nil | Nil | Nil | Nil | Low |
| Boruah,* 2011 | Tooth clearing and canal staining | India | NA | NA | NA | 480 | NA | NA | 63.75 | 7.08 | 22.9 | Nil | 6.25 | Nil | Nil | Nil | Nil | Low |
| Caliskan, 1995 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 100 | NA | NA | 68.63 | 13.73 | 13.73 | Nil | 1.96 | Nil | Nil | 1.96 | Nil | Low |
| Chaturvedi, 2019 | Tooth clearing and canal staining | NA | NA | NA | NA | 27 | NA | NA | 66.66 | 3.7 | 18.51 | 11.11 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Dizayee,* 2019 | CBCT | Iraq | 429 | 229/200 | 14-75 | 1716 | NA | NA | 79.25 | 0.47 | 20.28 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Estrela, 2015 | CBCT | Brazil | 618 | 224/394 | M=43.4 | 100 | 100 | Nil | 65 | 35 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Ghabbani, 2020 | CBCT | Saudi Arabia | 406 | 300/106 | 20–80 | 812 | NA | NA | 49.38 | Nil | 43.22 | 0.25 | 4.93 | Nil | 2.22 | Nil | Nil | Low |
| Gomes, 1996 | Modeling | NA | NA | NA | 40-60 | 58 | NA | NA | 63.8 | 22.4 | 1.7 | Nil | 5.2 | 5.2 | 1.7 | Nil | Nil | Moderate |
| Goran, 2020 | CBCT | Iraq | 194 | 72/122 | 16-40 | 388 | NA | NA | 67 | 1 | 22.6 | Nil | 7.7 | Nil | 1.8 | Nil | Nil | Low |
| Green,* 1973 | Sectioning | NA | NA | NA | NA | 500 | 100 | Nil | 79 | 17 | Nil | 4 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Han, 2014 | CBCT | China | 648 | NA | NA | 1286 | 100 | Nil | 84.29 | 3.42 | 6.53 | 1.17 | 3.89 | Nil | 0.31 | Nil | 0.39 | Low |
| Hassani, 2016 | CBCT | NA | 81 | NA | NA | 160 | 100 | Nil | 63.1 | 13.1 | 21.2 | Nil | 2.5 | Nil | Nil | Nil | Nil | Moderate |
| Jaju, 2013 | CBCT | India | 300 | NA | NA | 130 | NA | NA | 54.6 | 6.9 | 38.45 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Kalaitzoglou, 2018 | CBCT | Greece | NA | NA | NA | 143 | NA | NA | 71.3 | 4.2 | 21 | Nil | 1.4 | Nil | Nil | Nil | 2.1 | Moderate |
| Kamtane,* 2016 | CBCT | India | NA | NA | NA | 102 | 100 | Nil | 64.71 | 23.53 | 8.82 | 2.94 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Kartal,* 1992 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 55 | 16 | 20 | 4 | 3 | Nil | Nil | Nil | 2 | Moderate |
| Kartika, 2018 | Radiograph | Indonesia | 55 | NA | NA | 220 | NA | NA | 87.72 | 1.82 | 7.27 | Nil | Nil | Nil | Nil | Nil | 3.18 | Low |
| Kelsen, 1999 | Tooth clearing and canal staining | NA | 66 | NA | 8-40 | 54 | NA | NA | 96.3 | Nil | 3.8 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Kurumboor, 2018 | CBCT | India | NA | NA | NA | 100 | 100 | Nil | 73 | 1 | 13 | 10 | 3 | Nil | Nil | Nil | Nil | Moderate |
| Leoni, 2014 | Micro-CT | Brazil | NA | NA | NA | 50 | NA | NA | 50 | Nil | 28 | Nil | Nil | Nil | 4 | Nil | 18 | Moderate |
| Lin, 2014 | CBCT | China | 353 | 163/190 | 15-75 | 706 | 100 | Nil | 89.1 | 2.4 | 6.2 | 1.7 | 0.6 | Nil | Nil | Nil | Nil | Low |
| Liu, 2014 | CBCT | China | 398 | 190/208 | 16-50 | 768 | NA | NA | 91.1 | 2 | 5.3 | 1.3 | 0.3 | Nil | Nil | Nil | Nil | Low |
| Madeira, 1973 | Tooth clearing and canal staining | NA | NA | NA | NA | 683 | NA | NA | 88.7 | 11 | Nil | 0.3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Martins, 2017 | CBCT | Portugal | 646 | 228/418 | M=51 | 1160 | 100 | Nil | 72.3 | 2.5 | 24.2 | 0.1 | 0.3 | Nil | 5 | Nil | 0.1 | Low |
| Martins, 2018 | CBCT | China | 120 | 54/66 | M=28 | 240 | 100 | Nil | 99.6 | Nil | 0.4 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1203 | 100 | Nil | 72.6 | 2.4 | 24 | 0.1 | 0.3 | Nil | 0.5 | Nil | 0.1 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1203 | NA | NA | 72.57 | 2.41 | 24.02 | 0.08 | 0.33 | Nil | 0.5 | Nil | 0.08 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=50.8 | 1203 | 100 | Nil | 72.57 | 2.41 | 24.02 | 0.08 | 0.33 | Nil | 0.5 | Nil | 0.08 | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17-59 | 410 | 100 | Nil | 73.66 | Nil | 26.34 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17-59 | 410 | 100 | Nil | 73.7 | Nil | 26.3 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Milanezi de Almeida,* 2013 | Micro- CT | Brazil | NA | NA | NA | 324 | NA | NA | 75 | 0.62 | 16 | Nil | 2.47 | Nil | 0.31 | Nil | 4.94 | Low |
| Mirhosseini, 2019 | CBCT | Iran | 180 | NA | NA | 330 | NA | NA | 76.1 | Nil | 15.8 | 0.6 | 7.6 | Nil | Nil | Nil | Nil | Low |
| Mirzaie, 2012 | CBCT | Iran | 66 | NA | NA | 66 | 100 | Nil | 84.8 | 10.6 | 1.5 | 3.1 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Miyashita,* 1997 | Tooth clearing and canal staining | NA | NA | NA | NA | 1085 | 100 | Nil | 87.6 | 9.3 | 1.4 | 1.7 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Naz,* 2015 | Radiograph Sectioning |
Pakistan | 100 | 23/77 | ≥10 | 100 | NA | NA | 91 | Nil | 6 | Nil | 3 | Nil | Nil | Nil | Nil | Low |
| Nogueira,* 2017 | Tooth clearing and canal staining | Brazil | NA | NA | NA | 100 | 100 | NIL | 72 | Nil | 17 | Nil | 1 | Nil | Nil | Nil | Nil | Moderate |
| Paes da Silva Ramos Fernandes,* 2014 | Micro-CT | NA | NA | NA | NA | 40 | NA | NA | 60 | Nil | 40 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Pan, 2019 | CBCT | Malaysia | 208 | 90/118 | 15-66 | 408 | 100 | Nil | 94.9 | Nil | 1 | Nil | 4.2 | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 17-79 | 54 | NA | NA | 57.4 | 1.9 | 37 | Nil | 3.7 | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 15-65 | 54 | NA | NA | 57.4 | 1.9 | 37 | Nil | 3.7 | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Japan | NA | NA | 20-88 | 94 | NA | NA | 86.2 | Nil | 10.6 | Nil | 2.1 | Nil | 1.1 | Nil | Nil | Low |
| Perlea,* 2013 | Radiograph | Rome | NA | NA | NA | 575 | NA | NA | 81 | 17 | Nil | 1 | 1 | Nil | Nil | Nil | Nil | Low |
| Pineda, 1972 | Radiograph | NA | NA | NA | ≤25-55≥ | 179 | NA | NA | 72.4 | 2 | 23.5 | 1 | Nil | 1.1 | Nil | Nil | Nil | Moderate |
| Popovic, 2018 | CBCT | Serbia | NA | NA | NA | 296 | 100 | Nil | 73 | 4.7 | 21.6 | Nil | 0.7 | Nil | Nil | Nil | Nil | Low |
| Rahimi, 2013 | Tooth clearing and canal staining | Iran | NA | NA | NA | 186 | 100 | Nil | 64.52 | 18.28 | 16.67 | 0.54 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Raman, 2017 | CBCT | India | 50 | 32/18 | NA | 100 | NA | NA | 65 | Nil | 33 | Nil | 2 | Nil | Nil | Nil | Nil | Moderate |
| Rankine-Wilson,* 1965 | Radiograph | Australia | NA | NA | NA | 111 | NA | NA | 59.5 | 35.14 | Nil | 5.41 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Saati, 2018 | CBCT | Iran | 207 | 86/121 | NA | 207 | 100 | Nil | 54.5 | Nil | 34.2 | Nil | 11.3 | Nil | Nil | Nil | Nil | Low |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | 200 | 100/100 | NA | 200 | NA | NA | 32.5 | 27 | 26 | 9 | 0.5 | Nil | Nil | 1 | 4 | Low |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 200 | NA | NA | 32.5 | 27.5 | 27 | 10 | 0.5 | Nil | Nil | 2 | 0.5 | Moderate |
| Shemesh, 2017 | CBCT | Israel | 1016 | 446/570 | 13–89 | 1472 | NA | NA | 59.5 | 4 | 33.7 | 0.8 | 0.5 | Nil | Nil | 1.2 | Nil | Low |
| Silva, 2016 | CBCT | NA | 432 | 211/221 | NA | 200 | NA | NA | 64.5 | Nil | 18 | Nil | 14.5 | 0.5 | 2.5 | Nil | Nil | Moderate |
| Singh, 2016 | Tooth clearing and canal staining | India | NA | NA | NA | 100 | 100 | Nil | 84 | 8 | 4 | 4 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Sroczyk-Jaszczyńska, 2019 | CBCT | Poland | 111 | 47/64 | 9-72 | 212 | 100 | Nil | 65.39 | 0.96 | 26.44 | Nil | 5.3 | Nil | 0.96 | Nil | 0.96 | Low |
| Sunil, 2019 | CBCT | India | 40 | 18/22 | 18-49 | 67 | 100 | Nil | 55.2 | 3 | 28.4 | 4.5 | 9 | Nil | Nil | Nil | Nil | Low |
| Uma,* 2004 | Radiograph | India | NA | NA | NA | 50 | NA | NA | 44 | 2 | 52 | Nil | Nil | 2 | Nil | Nil | Nil | Moderate |
| Valenti-Obino, 2019 | CBCT | Italy | 250 | 130/120 | 18-79 | 487 | 100 | Nil | 55 | 34.3 | 9.3 | 0.6 | Nil | Nil | 0.8 | Nil | Nil | Low |
| Verma, 2017 | CBCT | India | 200 | 103/97 | 15-60 | 400 | 100 | Nil | 68.25 | 11 | 15.25 | 1.75 | 3.75 | Nil | Nil | Nil | Nil | Low |
| Vertucci, 1974 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 70 | 5 | 22 | 3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Vertucci, 1984 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 70 | 5 | 22 | 3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Walker, 1988 | Radiograph | China | 151 | NA | NA | 100 | NA | NA | 78 | 21 | Nil | 1 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Wu, 2018 | CBCT | Taiwan | 400 | NA | NA | 800 | NA | NA | 84.4 | Nil | 13.5 | Nil | 2.1 | Nil | Nil | Nil | Nil | Low |
| Zhengyan, 2016 | CBCT | China | 1725 | 923/802 | ≤20-60≥ | 3375 | 100 | Nil | 96.25 | 0.15 | 2.7 | 0.1 | 0.75 | Nil | Nil | Nil | 0.05 | Low |
*The studies which have not differentiated between mandibular central and lateral incisors, † Root canal anatomy studied in patients with Down syndrome, ‡ Other=Additional modifications of Vertucci classification [Table 3]. Micro-CT: Micro-computed tomography, CBCT: Cone-beam CT; NA: Not available, M: Mean age of the population (as stated in the study), ≤25-55≥: Indicates an age range in a study where the population groups were up to 25 years, between 25 and 55 years, and over 55 years of age
Table 3.
Additional modifications of Vertucci classification
| Additional modifications of Vertucci classification | ||||
|---|---|---|---|---|
|
| ||||
| Author, year | Mandibular tooth | Other‡ types (%) | Root canal anatomy | Classification |
| Ajinkya MP, 2017 | Central | 3 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| Lateral | 2 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Amardeep, 2014 | Canine | 1.60 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| Arslan, 2015 | Central | 1.60 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| Lateral | 0.50 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Aung, 2020 | Central | 1.72 | 1-3-2 | NA |
| 6.90 | 1-2-1-2-1 | |||
| Lateral | 2.63 | 2-3-1 | Type XII - Sert and Bayirli | |
| Han, 2014 | Central | 0.39 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| Lateral | 0.08 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Kalaitzoglou, 2018 | Central | 2.10 | 1-2-1-2-1 | NA |
| Lateral | 1.37 | 1-2-1-2-1 | NA | |
| Karataslioglu, 2019 | Canine | 0.70 | NA | NA |
| Kartal,* 1992 | Central and lateral | 1 | 2-3-1 | Type VI - Kartal and Yanikoğlu |
| 1 | 1-2-1-3 | Type VII - Kartal and Yanikoğlu | ||
| Kartika, 2018 | Central | 2.73 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| 0.45 | 1-2-1-2-1 | NA | ||
| Lateral | 1.82 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Leoni, 2014 | Central | 4 | 1-2-1-2-1 | NA |
| 2 | 1-2-3-2-1 | |||
| 2 | 1-2-3-2-3 | |||
| 2 | 1-3-2-1-2-1-2-1 | |||
| 2 | 1-2-1-2-3-2-3-2-1 | |||
| 2 | 1-2-1-2-3-2-1-2-2-1 | |||
| 2 | 1-2-1-2-3-2-1-2-1-2-1 | |||
| 2 | 1-2-3-2-3-2-3-2-1-2-1 | |||
| Lateral | 2 | 1-2-3-2 | Type X - Sert and Bayirli | |
| 2 | 1-2-1-2-1 | NA | ||
| 2 | 1-2-3-2-1 | |||
| 2 | 1-2-3-2-3 | |||
| Martins, 2017 | Central | 0.10 | 1-2-1-2-1 | NA |
| Lateral | 0.20 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| 0.10 | 1-3-1 | Type XVII - Sert and Bayirli | ||
| Canine | 0.10 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Martins, 2018 | Central | 0.10 | Other 2 root canal types | NA |
| Lateral | 0.20 | Other 2 root canal types | NA | |
| 0.10 | Other 3 root canal types | |||
| Canine | 0.10 | Other 2 root canal types | NA | |
| Martins, 2018 | Central | 0.08 | 1-2-1-2-1 | NA |
| Lateral | 0.16 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| 0.08 | 1-3-1 | Type XVII - Sert and Bayirli | ||
| Canine | 0.08 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| Martins, 2018 | Central | 0.08 | Other 2 root canal types | NA |
| Lateral | 0.16 | Other 2 root canal types | NA | |
| 0.08 | Other 3 root canal types | |||
| Canine | 0.08 | Other 2 root canal types | NA | |
| Milanezi de Almeida,* 2013 | Central and lateral | 2.16 | 1-2-1-2-1 | NA |
| 0.93 | 1-3-1 | Type XVII - Sert and Bayirli | ||
| 0.62 | 1-2-3-1 | NA | ||
| 0.31 | 1-3 | Type IX - Sert and Bayirli | ||
| 0.31 | 1-2-1-2-1-2-1 | NA | ||
| 0.31 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | ||
| 0.31 | 1-3-1-3 | NA | ||
| Sert, 2004 | Central | 0.50 | 1-2-3-2 | Type X - Sert and Bayirli |
| 0.50 | 1-2-3-2-1-3 | NA | ||
| 0.50 | 1-2-4-2 | |||
| 0.50 | 1-3-1-2 | |||
| 0.50 | 1-2-4-3-1 | |||
| 0.50 | 1-2-3-1 | |||
| 0.50 | 1-2-3-2-1 | |||
| 0.50 | 1-2-3-2 | Type X - Sert and Bayirli | ||
| Lateral | 0.50 | 1-2-3-2 | Type X - Sert and Bayirli | |
| 0.50 | 2-3-2 | NA | ||
| 0.50 | 2-1/2-1 | |||
| Canine | 0.50 | 1-3-4-1 | NA | |
| Sert, 2004 | Central | 0.50 | 1-2-3-2 | Type X - Sert and Bayirli |
| Lateral | 0.50 | 1-2-3-2 | Type X - Sert and Bayirli | |
| Sroczyk-Jaszczyńska, 2019 | Central | 0.48 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli |
| 0.48 | 1-3 | Type IX - Sert and Bayirli | ||
| Lateral | 0.97 | 2-1-2-1 | Type IV - Gulabivala et al./Type XIX - Sert and Bayirli | |
| 0.50 | 1-2-1-2-1 | NA | ||
| 0.50 | 1-3 | Type IX - Sert and Bayirli | ||
| Canine | 0.49 | 1-3 | Type IX - Sert and Bayirli | |
| Zhengyan, 2016 | Central | 0.05 | NA | NA |
| Lateral | 0.30 | NA | NA | |
| Canine | 0.85 | NA | NA | |
*The studies which have not differentiated between mandibular central and lateral incisors. NA: Not available
Table 4.
Root and root canal anatomy of mandibular lateral incisors
| Author, year | Methodology | Demographics | Root and root canal anatomy | Risk of bias | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||||||||||||
| Mandibular lateral incisor | Country | Number of subjects | Men/women | Age (years) | Number of teeth | Number of roots | Vertucci classification (%) | |||||||||||
|
|
|
|||||||||||||||||
| 1 | 2 | I | II | III | IV | V | VI | VII | VIII | Other‡ | ||||||||
| Ajinkya MP, 2017 | CBCT | India | NA | NA | NA | 100 | NA | NA | 54 | 15 | 27 | 2 | Nil | Nil | Nil | Nil | 2 | Moderate |
| Al-Fouzan, 2012 | Tooth clearing and canal staining | Saudi Arabia | NA | NA | NA | 40 | 100% | Nil | 70 | Nil | 30 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Al-Qudah,* 2006 | Tooth clearing and canal staining | Jordan | NA | NA | NA | 450 | 100% | Nil | 73.8 | 10.9 | 6.7 | 5.1 | 3.6 | Nil | Nil | Nil | Nil | Low |
| Almeida-Gomes,* 2017 | CBCT | Brazil | NA | NA | NA | 148 | NA | NA | 72.3 | 25.67 | Nil | 2.03 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Altunsoy, 2014 | CBCT | Turkey | 827 | 410/417 | 14-70 | 1603 | NA | NA | 80.2 | 1.3 | 1 | 5.4 | 12.1 | Nil | Nil | Nil | Nil | Low |
| Aminsobhani, 2013 | CBCT | Iran | 400 | NA | NA | 614 | 100% | Nil | 70.6 | 7.1 | 3.7 | 15.4 | 3.2 | Nil | Nil | Nil | Nil | Low |
| Arslan, 2015 | CBCT | Turkey | 101 | 47/54 | 10-70 | 190 | 100% | Nil | 52.9 | 2.6 | 42.3 | Nil | 1.6 | Nil | Nil | Nil | 0.5 | Low |
| Assadian,* 2016 | Digital radiography | Iran | NA | NA | NA | 76 | NA | NA | 52.6 | 1.3 | 31.6 | Nil | 14.5 | Nil | Nil | Nil | Nil | Low |
| Sectioning | 76 | NA | NA | 69.7 | 5.3 | 25 | Nil | Nil | Nil | Nil | Nil | Nil | ||||||
| CBCT | 76 | NA | NA | 43.4 | 5.3 | 50 | Nil | 1.3 | Nil | Nil | Nil | Nil | ||||||
| Aung, 2020 | Tooth clearing and Canal staining | Myanmar | NA | NA | NA | 38 | NA | NA | 68.42 | Nil | 28.95 | Nil | Nil | Nil | Nil | Nil | 2.63 | Low |
| Basha, 2018 | CBCT | Egypt | 100 | 50/50 | 15-60 | 200 | NA | NA | 89.5 | Nil | 8 | Nil | 2.5 | Nil | Nil | Nil | Nil | Low |
| Baxter, 2020 | CBCT | Germany | 302 | 116/186 | 18-78 | 604 | NA | NA | 76.65 | 21.35 | Nil | 1 | 1 | Nil | Nil | Nil | Nil | Low |
| Benjamin,* 1974 | Radiograph | USA | NA | NA | NA | 364 | NA | NA | 58.6 | 40.1 | Nil | 1.3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Boruah,* 2010 | Tooth clearing and canal staining | India | NA | NA | NA | 480 | NA | NA | 63.75 | 7.08 | 22.92 | Nil | 6.25 | Nil | Nil | Nil | Nil | Low |
| Boruah,* 2011 | Tooth clearing and canal staining | India | NA | NA | NA | 480 | NA | NA | 63.75 | 7.08 | 22.9 | Nil | 6.25 | Nil | Nil | Nil | Nil | Low |
| Caliskan, 1995 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 100 | NA | NA | 68.63 | 13.73 | 15.69 | Nil | 1.96 | Nil | Nil | Nil | Nil | Low |
| Chaturvedi, 2019 | Tooth clearing and canal staining | NA | NA | NA | NA | 27 | NA | NA | 65.21 | 8.69 | 21.73 | 4.34 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Dizayee,* 2019 | CBCT | Iraq | 429 | 229/200 | 14-75 | 1716 | NA | NA | 79.25 | 0.47 | 20.28 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Estrela, 2015 | CBCT | Brazil | 618 | 224/394 | M=43.4 | 100 | 100% | Nil | 58 | 42 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Ghabbani, 2020 | CBCT | Saudi Arabia | 406 | 300/106 | 20-80 | 812 | NA | NA | 51.35 | Nil | 41.5 | 0.25 | 5.79 | Nil | 1.1 | Nil | Nil | Low |
| Gomes, 1996 | Modeling | NA | NA | NA | 40-60 | 53 | NA | NA | 64.1 | 20.7 | 3.8 | Nil | 5.7 | 5.7 | Nil | Nil | Nil | Moderate |
| Goran, 2020 | CBCT | Iraq | 194 | 72/122 | 16-40 | 388 | NA | NA | 67 | 0.5 | 18 | Nil | 13.9 | Nil | 0.7 | Nil | Nil | Low |
| Green,* 1973 | Sectioning | NA | NA | NA | NA | 500 | 100% | Nil | 79 | 17 | Nil | 4 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Han, 2014 | CBCT | China | 648 | NA | NA | 1294 | 100% | Nil | 72.64 | 4.02 | 15.53 | 2.32 | 5.1 | 0.15 | 0.15 | Nil | 0.08 | Low |
| Hassani, 2016 | CBCT | NA | 81 | NA | NA | 160 | 100% | Nil | 56.9 | 12.5 | 28.1 | Nil | 2.5 | Nil | Nil | Nil | Nil | Moderate |
| Jaju, 2013 | CBCT | India | 300 | NA | NA | 130 | NA | NA | 52.3 | 5.8 | 41.95 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Kalaitzoglou, 2018 | CBCT | Greece | NA | NA | NA | 143 | NA | NA | 69.86 | 5.48 | 23.28 | Nil | Nil | Nil | Nil | Nil | 1.37 | Moderate |
| Kamtane,* 2016 | CBCT | India | NA | NA | NA | 102 | 100% | Nil | 64.71 | 23.53 | 8.82 | 2.94 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Kartal,* 1992 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 55 | 16 | 20 | 4 | 3 | Nil | Nil | Nil | 2 | Moderate |
| Kartika, 2018 | Radiograph | Indonesia | 55 | NA | NA | 220 | NA | NA | 84.55 | 0.9 | 12.73 | Nil | Nil | Nil | Nil | Nil | 1.82 | Low |
| Kelsen,†1999 | Tooth clearing and canal staining | NA | 66 | NA | 8–40 | 44 | NA | NA | 88.6 | Nil | 4.5 | Nil | 6.8 | Nil | Nil | Nil | Nil | Moderate |
| Kurumboor, 2018 | CBCT | India | NA | NA | NA | 100 | 100% | Nil | 67 | 3 | 17 | 8 | 5 | Nil | Nil | Nil | Nil | Moderate |
| Leoni, 2014 | Micro-CT | Brazil | NA | NA | NA | 50 | NA | NA | 62 | Nil | 28 | Nil | Nil | Nil | 2 | Nil | 8 | Moderate |
| Lin, 2014 | CBCT | China | 353 | 163/190 | 15–75 | 706 | 100% | Nil | 74.5 | 3.7 | 19.3 | 2.1 | 0.4 | Nil | Nil | Nil | Nil | Low |
| Liu, 2014 | CBCT | China | 398 | 190/208 | 16–50 | 785 | NA | NA | 82.5 | 3.9 | 10.4 | 2.8 | 0.3 | Nil | Nil | Nil | Nil | Low |
| Madeira, 1973 | Tooth clearing and canal staining | NA | NA | NA | NA | 650 | NA | NA | 88.2 | 11.1 | Nil | 0.8 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Martins, 2017 | CBCT | Portugal | 646 | 228/418 | M=51 | 1191 | 100% | Nil | 69.8 | 6.3 | 23.1 | Nil | 0.3 | Nil | 0.2 | Nil | 0.3 | Low |
| Martins, 2018 | CBCT | China | 120 | 54/66 | M=28 | 240 | 100% | Nil | 95 | 2.9 | 0.8 | Nil | 1.3 | Nil | Nil | Nil | Nil | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1234 | 100% | Nil | 70.1 | 6.1 | 23.1 | Nil | 0.2 | Nil | 0.2 | Nil | 0.3 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1234 | NA | NA | 70.1 | 6.08 | 23.1 | Nil | 0.24 | Nil | 0.24 | Nil | 0.24 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=50.8 | 1234 | 100% | Nil | 70.1 | 6.08 | 23.1 | Nil | 0.24 | Nil | 0.24 | Nil | 0.24 | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17-59 | 412 | 100% | 0 | 69.17 | Nil | 29.85 | Nil | 0.97 | Nil | Nil | Nil | Nil | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17-59 | 412 | 100% | 0.01 | 69.2 | Nil | 29.8 | Nil | 1 | Nil | Nil | Nil | Nil | Low |
| Milanezi de Almeida,* 2013 | Micro-CT | Brazil | NA | NA | NA | 324 | NA | NA | 75 | 0.62 | 16 | Nil | 2.47 | Nil | 0.31 | Nil | 4.94 | Low |
| Mirhosseini, 2019 | CBCT | Iran | 180 | NA | NA | 351 | NA | NA | 65 | 0.6 | 15.7 | 0.9 | 17.9 | Nil | Nil | Nil | Nil | Low |
| Mirzaie, 2012 | CBCT | Iran | 66 | NA | NA | 66 | 100% | Nil | 78.8 | 12.1 | 1.5 | 7.6 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Miyashita,* 1997 | Tooth clearing and canal staining | NA | NA | NA | NA | 1085 | 100% | Nil | 87.6 | 9.3 | 1.4 | 1.7 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Naz,* 2015 | Radiograph Sectioning |
Pakistan | 100 | 23/77 | ≥10 | 100 | NA | NA | 91 | Nil | 6 | Nil | 3 | Nil | Nil | Nil | Nil | Low |
| Nogueira,* 2017 | Tooth clearing and canal staining | Brazil | NA | NA | NA | 100 | 100% | Nil | 72 | Nil | 17 | Nil | 1 | Nil | Nil | Nil | Nil | Moderate |
| Paes da Silva Ramos Fernandes,* 2014 | Micro-CT | NA | NA | NA | NA | 40 | NA | NA | 60 | Nil | 40 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Pan, 2019 | CBCT | Malaysia | 208 | 90/118 | 15-66 | 400 | 100% | Nil | 87.8 | Nil | 3.8 | 0.3 | 8.3 | Nil | Nil | Nil | Nil | Low |
| Papic, 2019 | CBCT | Serbia | 63 | 32/31 | M=28.84 | 126 | NA | NA | 54 | 4.8 | 41.3 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 17-79 | 59 | NA | NA | 35.6 | 8.5 | 55.9 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 15-65 | 60 | NA | NA | 36.7 | 8.3 | 55 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Japan | NA | NA | 20-88 | 100 | NA | NA | 66 | Nil | 30 | Nil | 3 | Nil | 1 | Nil | Nil | Low |
| Perlea,* 2013 | Radiograph | Rome | NA | NA | NA | 575 | NA | NA | 81 | 17 | Nil | 1 | 1 | Nil | Nil | Nil | Nil | Low |
| Pineda, 1972 | Radiograph | NA | NA | NA | ≤25-55≥ | 184 | NA | NA | 76.2 | 3.2 | 19.3 | 1.3 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Popovic, 2018 | CBCT | Serbia | NA | NA | NA | 294 | 100% | Nil | 73.5 | 5.4 | 18.4 | 0.7 | 2 | Nil | Nil | Nil | Nil | Low |
| Rahimi, 2013 | Tooth clearing and canal staining | Iran | NA | NA | NA | 128 | 1 | Nil | 61.71 | 16.41 | 21.09 | 0.78 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Raman, 2017 | CBCT | India | 50 | 32/18 | NA | 100 | NA | NA | 51 | Nil | 48 | Nil | 1 | Nil | Nil | Nil | Nil | Moderate |
| Rankine-Wilson,* 1965 | Radiograph | Australia | NA | NA | NA | 111 | NA | NA | 59.5 | 35.14 | Nil | 5.41 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Saati, 2018 | CBCT | Iran | 207 | 86/121 | NA | 207 | 1 | Nil | 56.5 | Nil | 26.1 | Nil | 17.4 | Nil | Nil | Nil | Nil | Low |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | 200 | 100/100 | NA | 200 | NA | NA | 37 | 26.5 | 26 | 9 | Nil | Nil | Nil | Nil | 1.5 | Low |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 200 | NA | NA | 37 | 27 | 26.5 | 9.5 | Nil | Nil | Nil | Nil | 0.5 | Moderate |
| Shemesh, 2017 | CBCT | Israel | 1016 | 446/570 | 13-89 | 1508 | Na | NA | 62.1 | 4.3 | 31.9 | 0.4 | 0.05 | Nil | Nil | 0.8 | Nil | Low |
| Silva, 2016 | CBCT | NA | 432 | 211/221 | NA | 200 | Na | NA | 60.5 | 0.5 | 25.5 | Nil | 12 | Nil | 1.5 | Nil | Nil | Moderate |
| Singh, 2016 | Tooth clearing and canal staining | India | NA | NA | NA | 100 | 100% | Nil | 80 | 8 | 4 | 8 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Sroczyk-Jaszczyńska, 2019 | CBCT | Poland | 111 | 47/64 | 9-72 | 208 | 100% | Nil | 67.25 | 0.99 | 24.7 | 0.5 | 3.89 | Nil | Nil | Nil | 1.97 | Low |
| Sunil, 2019 | CBCT | India | 40 | 18/22 | 18-49 | 80 | 1 | Nil | 57.5 | 5 | 22.5 | 8.8 | 6.3 | Nil | Nil | Nil | Nil | Low |
| Uma,* 2004 | Radiograph | India | NA | NA | NA | 50 | NA | NA | 44 | 2 | 52 | Nil | Nil | Nil | 2 | Nil | Nil | Moderate |
| Valenti-Obino, 2019 | CBCT | Italy | 250 | 130/120 | 18-79 | 491 | 100% | Nil | 57 | 35.7 | 6.9 | Nil | Nil | Nil | 0.4 | Nil | Nil | Low |
| Verma, 2017 | CBCT | India | 200 | 103/97 | 15-60 | 400 | 1 | Nil | 65 | 13.25 | 15.25 | 3 | 3.5 | Nil | Nil | Nil | Nil | Low |
| Vertucci, 1974 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 75 | 5 | 18 | 2 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Vertucci, 1984 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 75 | 5 | 18 | 2 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Walker, 1988 | Radiograph | China | 151 | NA | NA | 100 | NA | NA | 68 | 31 | Nil | 1 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Wu, 2017 | CBCT | Taiwan | 300 | 179/121 | M=38.55 | 600 | NA | NA | 75 | Nil | 23 | Nil | 2 | Nil | Nil | Nil | Nil | Low |
| Zhengyan, 2016 | CBCT | China | 1725 | 923/802 | ≤20-60≥ | 3257 | 1 | 0 | 89.4 | 1.05 | 7.7 | 0.3 | 1.15 | Nil | Nil | Nil | 0.3 | Low |
*The studies which have not differentiated between mandibular central and lateral incisors, † Root canal anatomy studied in patients with Down syndrome, ‡Other=Additional modifications of Vertucci classification [Table 3]. Micro-CT: Micro computed tomography, CBCT: Cone-beam computed tomography, NA: Not available, M: Mean age of the population (as stated in the study), ≤25-55≥: Indicates an age range in a study where the population groups were up to 25 years, between 25 and 55 years, and over 55 years of age
Table 5.
Root and root canal anatomy of mandibular canines
| Author, year | Methodology | Demographics | Root and root canal anatomy | Risk of bias | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||||||||||||
| Mandibular canine | Country | Number of subjects | Men/women | Age (years) | Number of teeth | Number of roots (%) | Vertucci classification (%) | |||||||||||
|
|
|
|||||||||||||||||
| 1 | 2 | I | II | III | IV | V | VI | VII | VIII | Other‡ | ||||||||
| Al-Dahman, 2019 | CBCT | Saudi Arabia | 707 | 396/311 | 16–79 | 454 | 99.80 | 0.20 | 95.4 | 2.6 | 1.8 | 0.2 | Nil | Nil | Nil | Nil | Nil | Low |
| Altunsoy, 2014 | CBCT | Turkey | 827 | 410/417 | 14–70 | 1604 | NA | NA | 92.8 | 2.1 | 1.2 | 1.35 | 2.65 | Nil | Nil | Nil | Nil | Low |
| Amardeep, 2014 | CBCT | India | NA | NA | NA | 250 | 100 | Nil | 79.6 | 3.2 | 13.6 | Nil | 2 | Nil | Nil | Nil | 1.6 | Low |
| Aminsobhani, 2013 | CBCT | Iran | 400 | NA | NA | 608 | 96 | 4.70 | 71.8 | 10.3 | 2.8 | 12.8 | 2.3 | Nil | Nil | Nil | Nil | Low |
| Basha, 2018 | CBCT | Egypt | 100 | 50/50 | 15–60 | 200 | NA | NA | 100 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Caliskan, 1995 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 100 | NA | NA | 80.39 | 3.92 | 13.73 | Nil | 1.96 | Nil | Nil | Nil | Nil | Low |
| Doumani, 2020 | CBCT | Syria | 418 | 172/246 | 16–60 | 418 | 97.85 | 2.15 | 95.87 | 0.73 | 3.18 | Nil | 0.24 | Nil | Nil | Nil | Nil | Low |
| Estrela, 2015 | CBCT | Brazil | 618 | 224/394 | M=43.4 | 100 | 97 | 3 | 78 | 19 | Nil | 3 | Nil | Nil | Nil | Nil | Nil | Low |
| Goran, 2020 | CBCT | Iraq | 194 | 72/122 | 16–40 | 388 | NA | NA | 90.7 | 0.5 | 1.5 | Nil | 6.7 | Nil | 0.5 | Nil | Nil | Low |
| Green, 1973 | Sectioning | NA | NA | NA | NA | 100 | 100 | Nil | 87 | 10 | Nil | 3 | Nil | Nil | Nil | Nil | Nil | M |
| Han, 2014 | CBCT | China | 648 | NA | NA | 1291 | 98.68 | 1.32 | 93.73 | 0.62 | 3.25 | Nil | 0.54 | Nil | Nil | Nil | Nil | Low |
| Karataslioglu, 2019 | CBCT | Turkey | 220 | 99/121 | 15–60 | 419 | 96.60 | 3.40 | 87.8 | Nil | 9 | Nil | 2 | Nil | 0.5 | Nil | 0.7 | Low |
| Kelsen, † 1999 | Tooth clearing and canal staining | NA | 66 | NA | 8–40 | 12 | NA | NA | 100 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Kurumboor, 2018 | CBCT | India | NA | NA | NA | 100 | 100 | Nil | 79 | 3 | 6 | 9 | 1 | 2 | Nil | Nil | Nil | Moderate |
| Marceliano-Alves, 2018 | Micro-CT | Brazil | NA | NA | NA | 80 | 100 | Nil | 100 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Martins, 2017 | CBCT | Portugal | 646 | 228/418 | M=51 | 1200 | 97.20 | 2.80 | 90.2 | 3.3 | 2.7 | 1.4 | 2.3 | Nil | Nil | Nil | 0.1 | Low |
| Martins, 2018 | CBCT | China | 120 | 54/66 | M=28 | 240 | 99.20 | 0.80 | 97.1 | 1.7 | 0.4 | 0.4 | 0.4 | Nil | Nil | Nil | Nil | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1244 | 97 | 3 | 90.2 | 3.3 | 2.6 | 1.4 | 2.5 | Nil | Nil | Nil | 0.1 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=51 | 1244 | NA | NA | 90.19 | 3.3 | 2.57 | 1.37 | 2.49 | Nil | Nil | Nil | 0.08 | Low |
| Martins, 2018 | CBCT | Portugal | 670 | 243/427 | M=50.8 | 1244 | 97.03 | 2.97 | 90.19 | 3.3 | 2.57 | 1.37 | 2.49 | Nil | Nil | Nil | 0.08 | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17–59 | 410 | 97.32 | 2.68 | 90.73 | Nil | 6.1 | Nil | 3.17 | Nil | Nil | Nil | Nil | Low |
| Mashyakhy, 2019 | CBCT | Saudi Arabia | 208 | 100/108 | 17–62 | 410 | 97.30 | 2.70 | 90.7 | Nil | 6.1 | Nil | 3.2 | Nil | Nil | Nil | Nil | Low |
| Mirzaie, 2012 | CBCT | Iran | 66 | NA | NA | 66 | 100 | Nil | 95.4 | 3.1 | Nil | 1.5 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Naseri, 2019 | CBCT | Iran | NA | NA | NA | 33 | NA | NA | 93.9 | Nil | 6.1 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Tooth clearing and canal staining | 33 | NA | NA | 90.9 | Nil | 9.1 | Nil | Nil | Nil | Nil | Nil | Nil | ||||||
| Pan, 2019 | CBCT | Malaysia | 208 | 90/118 | 15–66 | 411 | 98.78 | 1.22 | 95.13 | 4.87 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Pecora, 1993 | Tooth clearing and canal staining | NA | NA | NA | NA | 830 | 98.30 | 1.70 | 92.2 | 4.9 | Nil | 2.9 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 17–79 | 57 | NA | NA | 70.2 | 8.8 | 17.5 | Nil | 3.5 | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Sri Lanka | NA | NA | 15–65 | 58 | NA | NA | 70.7 | 8.6 | 17.2 | Nil | 3.5 | Nil | Nil | Nil | Nil | Low |
| Peiris, 2008 | Tooth clearing and canal staining | Japan | NA | NA | 20–88 | 107 | NA | NA | 95.3 | Nil | 4.7 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Pineda, 1972 | Radiograph | NA | NA | NA | ≤25–55≥ | 187 | NA | NA | 81.5 | 13.5 | Nil | 5 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Popovic, 2018 | CBCT | Serbia | NA | NA | NA | 312 | 94.20 | 5.80 | 92.9 | 0.6 | 0.6 | Nil | 5.8 | Nil | Nil | Nil | Nil | Low |
| Rahimi, 2013 | Tooth clearing and canal staining | Iran | NA | NA | NA | 149 | 87.92 | 12.08 | 91.6 | 6.11 | 2.29 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Raman, 2017 | CBCT | India | 50 | 32/18 | NA | 98 | NA | NA | 82.65 | Nil | 17.35 | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | 200 | 100/100 | NA | 200 | NA | NA | 76 | 15.5 | 6.5 | 1.5 | Nil | Nil | Nil | Nil | 0.5 | Low |
| Sert, 2004 | Tooth clearing and canal staining | Turkey | NA | NA | NA | 200 | NA | NA | 76 | 16 | 6.5 | 1.5 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Silva, 2016 | CBCT | NA | 432 | 211/221 | NA | 200 | NA | NA | 90.5 | 1 | 4 | 2.5 | 2 | Nil | Nil | Nil | Nil | Moderate |
| Singh, 2016 | Tooth clearing and canal staining | India | NA | NA | NA | 100 | 100 | NIL | 92 | 8 | Nil | Nil | Nil | Nil | Nil | Nil | Nil | Moderate |
| Soleymani, 2017 | CBCT | Iran | 150 | 64/86 | M=42.5 | 300 | 98.67 | 1.33 | 89.7 | 3.7 | 5.7 | Nil | 1 | Nil | Nil | Nil | Nil | Low |
| Sroczyk-Jaszczyńska, 2019 | CBCT | Poland | 111 | 47/64 | 9–72 | 204 | 94.08 | 5.92 | 85.12 | 2 | 3.93 | 0.5 | 6.94 | 0.49 | Nil | Nil | 0.49 | Low |
| Vaziri, 2008 | Sectioning | Iran | NA | NA | NA | 100 | NA | NA | 88 | 5 | 7 | Nil | Nil | Nil | Nil | Nil | Nil | Low |
| Vertucci, 1974 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 78 | 14 | 2 | 6 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Vertucci, 1984 | Tooth clearing and canal staining | NA | NA | NA | NA | 100 | NA | NA | 78 | 14 | 2 | 6 | Nil | Nil | Nil | Nil | Nil | Moderate |
| Zhengyan, 2016 | CBCT | China | 1725 | 923/802 | ≤20–60≥ | 3014 | 99.20 | 0.80 | 95.8 | 0.7 | 2.1 | 0.15 | 0.4 | Nil | Nil | Nil | 0.85 | Low |
† Root canal anatomy studied in patients with Down syndrome, ‡ Other=Additional modifications of Vertucci classification [Table 3]. Micro-CT: Micro-computed tomography, CBCT: Cone-beam CT, NA: Not available, M: Mean age of the population (as stated in the study), ≤25-55≥: Indicates an age range in a study where the population groups were up to 25 years, between 25 and 55 years, and over 55 years of age
DISCUSSION
The knowledge of the root and root canal configurations of mandibular incisors and canines is crucial to avoid the possibility of a missed canal during root canal treatment. A missed root canal is one of the possible causes of failure of endodontic therapy. The signs and symptoms associated with this could range from no clinical symptoms to severe acute apical abscess.[27] A study reported the frequency of posttreatment apical periodontitis in the teeth with at least one untreated canal to be 98%.[28] Another study stated that 82.6% of the teeth with missed canals were associated with periapical lesions.[27] Therefore, clinicians should be completely informed and aware of the root anatomy and root canal configurations, with their possible variations, before commencing endodontic treatment to minimize the possibility of missing canals during treatment.
The numerous methods that have been used to study root canal anatomy include radiographic methods as well as nonradiographic methods.[29] Tooth clearing and canal staining method is generally considered the gold standard in studying root canal anatomy.[20,30,31] Micro-CT assessment is a relatively recent method to study root canal anatomy.[12] The differences in the methodology and the various origins of the investigated teeth account for the highly variable results of the present systematic review.
Demographic factors such as sex and age also play a role in governing the variability of root canal anatomy. Females show a significantly higher number of roots in the mandibular canines and simple root canal configurations in the mandibular incisors.[7,32] A progressive decrease of Vertucci Type I configuration was seen in the mandibular lateral incisors and mandibular canines, when compared to the younger groups. The opposite situation was noted with mandibular central incisors.[8] In the current systematic review, these variations in configurations between different ages and genders have not been mentioned separately but rather calculated as a single value for each type of canal configuration by taking an average of the values given for each age or sex. This has been done to provide a consolidated datasheet to understand the variations in the root and root canal configurations between different populations, as per the aim of this study.
Root canal anatomy was initially studied by Hess and Zurcher in 1925.[33] Since then, it has been studied and classified by various authors for ease of understanding. In this review, the root canal system configurations have been presented according to various classification systems.[6,13,19,20] There have also been a few studies where the root canal anatomy was studied but not presented as per any classification system. An attempt was then made to convert the data given into the Vertucci classification system (done only if the concerned study provided sufficient data to enable conversion).[15,16,34,35,36,37,39]
In the present systematic review, all the mandibular central incisors showed the presence of a single root. The most predominant root canal configuration was Vertucci Type I followed by Type III and in some cases Type II. The population of the Middle Eastern European countries showed the predominance of Vertucci Type I (32.5%–85.5%) and Vertucci type III (13.7%–50%). In previous studies, almost an equal proportion of Vertucci Types I and III canal configurations were seen in the mandibular central incisors of a Turkish and Saudi Arabian population.[32,40] Another study showed almost equal proportions of Type I (32.5%), Type II (27.5%), and Type III (27%) canal configurations in the mandibular central incisors of the Turkish population.[6] In this review, the mandibular central of the population of the Western European countries showed Vertucci Type I (55%–81%) followed by Vertucci type III (9.3%–26.4%) and Vertucci Type II (2.5%–34.3%). Similarly, the population in the Indian subcontinent showed Type I (44%–73%) followed by Type III (4%–38.4%) and Type II (1.7%–23.5%). The Brazilian population also showed Type I (50%–75%) followed by Type III (16%–28%) and Type II (0.6%–35%). On the other hand, Far East Asian countries showed Vertucci Type I (84.4%–99.6%) followed by Vertucci Type II (2%–21%) and Vertucci Type III (0.4%–13.5%). One study found a relatively high percentage of Vertucci Type II canal configuration in the mandibular incisors of the population of the United States, whereas Type III was not found.[35] A similar finding was reported in the mandibular incisors of the Australian population.[16] Overall, the percentages of Vertucci Types IV–VIII were relatively low.
All the mandibular lateral incisors showed the presence of a single root, except in two instances. 0.5% of permanent mandibular lateral incisors in a Saudi Arabian population and 0.3% of the lateral incisors in a Chinese population presented with two roots. The root canal configurations of the mandibular lateral incisors showed a considerable amount of variation. The most predominant configuration was Vertucci Type I followed by Type III. The population of the countries in Middle Eastern Europe showed the presence of Vertucci Type I (37%–89.5%) followed by Vertucci Type III (1.5%–50%), Vertucci Type II (0.5%–26.5%), Vertucci Type IV (0.25%–15.4%), and Vertucci Type V (0.05%–17.9%). Similarly, the Indian subcontinent showed the presence of Type I (35.6%–68.42%) followed by Type III (4%–55.9%), Type II (2%–23.53%), Type IV (2.94%–8.8%), and Type V (3%–6.3%). The Western European countries having a lesser amount of variability showed Vertucci Type I (67.25%–81%) followed by Vertucci Type III (23.1%–24.7%) and Vertucci Type II (0.99%–21.35%). Similarly, the South American population had a Type I (58%–75%), followed by Type III (16%–28%) and Type II (0.62%–42%) canal configuration. Far East Asian countries showed the presence of Vertucci Type I (66%–95%), Vertucci Type II (2.9%–31%), and Vertucci Type III (0.8%–30%). The South East Asian population showed the predominance of Vertucci Type I (84.55%–87.8%), with a lesser number of Type III (3.8%–12.73%). The North American and Australian populations showed canal configurations similar to those seen in the mandibular central incisors. A very interesting finding was reported by Peiris et al., in 2008, who found a higher percentage of Vertucci Type III canal configuration (55.9%) than Type I (35.6%) in the mandibular lateral incisors of the Sri Lankan population.[4,41] However, when a similar study was conducted by the same author in a Japanese population, a higher percentage of Vertucci Type I (66%) was found as compared to Type III (30%).[4] This finding reinforces that root canal morphology is variable among different population groups. Vertucci Types IV–VIII percentages were low but still greater than those seen in the mandibular central incisors.
A small proportion of mandibular canines in almost all the studies showed the presence of two roots. The frequency of two-rooted canines ranged from 0.2% to 12.08%, the greatest being in the Iranian population. Regarding the root canal configurations, a vast majority of mandibular canines showed a Vertucci Type I configuration, whereas the other types were seen to a minimum. Some variations were seen in the root canal configurations of the Middle Eastern European region (Vertucci Type II - 0.5%–16%, Vertucci Type III - 0.6%–13.73%) and the Indian subcontinent (Vertucci Type III - 6%–17.5%, Vertucci Type II - 3.2%–8.8%). However, these were still less than those seen in the mandibular incisors.
The root canal anatomy of the mandibular anterior teeth in patients suffering from Down syndrome has also been studied.[42] The root canal configurations were found to be relatively simple and mostly in Type I canal configuration. This finding can help the conventional endodontic treatment of Down syndrome patients.[42]
The lack of homogeneity across the data reported in the studies concerning the patient age, patient gender, and the methods used to study the root canal anatomy could have led to a bias in the interpretation of the results. The difficulty of standardizing clinicians’ interpretation of Vertucci canal configuration also poses limitations for comparing studies. All these factors must be taken into consideration when interpreting results from this systematic review. The variations in the root and root canal anatomy of the mandibular anterior teeth in genetic disorders other than Down syndrome should be investigated. Further research to study the variations in root canal anatomy of the mandibular incisors and canines due to functional changes occurring over time should also be carried out.
CONCLUSION
There are several prevalence studies on the root canal anatomy of the mandibular anterior teeth studied in different populations with various radiographic and nonradiographic methods. Our systematic review included data from 26 countries including the analysis of 71,404 mandibular anterior teeth. The risk of bias of all the included studies was either low or moderate. Deviations in anatomy were high in the Middle Eastern European countries and the Indian subcontinent. The population of the Far East Asian countries showed the least amount of variations. Taken together, these studies show that the mandibular incisors have a single root, and the most frequent canal configuration is Vertucci Type I followed by Type III and in some cases Type II. The percentage of second canals is higher in lateral incisors than in central incisors. Mandibular canines are mostly single rooted with a Vertucci Type I canal configuration but occasionally show the presence of two roots, though in a relatively low frequency.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
FULL ELECTRONIC SEARCH STRATEGY OF MEDLINE PUBMED DATABASE
REFERENCES
- 1.Martins JN, Marques D, Silva EJ, Caramês J, Versiani MA. Prevalence studies on root canal anatomy using cone-beam computed tomographic imaging: A systematic review. J Endod. 2019;45:372–86.e4. doi: 10.1016/j.joen.2018.12.016. [DOI] [PubMed] [Google Scholar]
- 2.Karabucak B, Bunes A, Chehoud C, Kohli MR, Setzer F. Prevalence of apical periodontitis in endodontically treated premolars and molars with untreated canal: A cone-beam computed tomography study. J Endod. 2016;42:538–41. doi: 10.1016/j.joen.2015.12.026. [DOI] [PubMed] [Google Scholar]
- 3.Martins JN, 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. [DOI] [PubMed] [Google Scholar]
- 4.Peiris R. Root and canal morphology of human permanent teeth in a Sri Lankan and Japanese population. Anthropol Sci. 2008;116:123–33. [Google Scholar]
- 5.Mashyakhy M, Gambarini G. Root and root canal morphology differences between genders: A comprehensive in-vivo CBCT study in a Saudi population. Acta Stomatol Croat. 2019;53:213–46. doi: 10.15644/asc53/3/5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Sert S, Bayirli GS. Evaluation of the root canal configurations of the mandibular and maxillary permanent teeth by gender in the Turkish population. J Endod. 2004;30:391–8. doi: 10.1097/00004770-200406000-00004. [DOI] [PubMed] [Google Scholar]
- 7.Martins JN, Marques D, Francisco H, Caramês J. Gender influence on the number of roots and root canal system configuration in human permanent teeth of a Portuguese subpopulation. Quintessence Int. 2018;49:103–11. doi: 10.3290/j.qi.a39508. [DOI] [PubMed] [Google Scholar]
- 8.Martins JN, Ordinola-Zapata R, Marques D, Francisco H, Caramês J. Differences in root canal system configuration in human permanent teeth within different age groups. Int Endod J. 2018;51:931–41. doi: 10.1111/iej.12896. [DOI] [PubMed] [Google Scholar]
- 9.Pineda F, Kuttler Y. Mesiodistal and buccolingual roentgenographic investigation of 7,275 root canals. Oral Surg Oral Med Oral Pathol. 1972;33:101–10. doi: 10.1016/0030-4220(72)90214-9. [DOI] [PubMed] [Google Scholar]
- 10.Assadian H, Dabbaghi A, Gooran M, Eftekhar B, Sharifi S, Shams N, et al. Accuracy of CBCT, digital radiography and cross-sectioning for the evaluation of mandibular incisor root canals. Iran Endod J. 2016;11:106–10. doi: 10.7508/iej.2016.02.006. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Saati S, Shokri A, Foroozandeh M, Poorolajal J, Mosleh N. Root morphology and number of canals in mandibular central and lateral incisors using cone beam computed tomography. Braz Dent J. 2018;29:239–44. doi: 10.1590/0103-6440201801925. [DOI] [PubMed] [Google Scholar]
- 12.Leoni GB, Versiani MA, Pécora JD, Damião de Sousa-Neto M. Micro-computed tomographic analysis of the root canal morphology of mandibular incisors. J Endod. 2014;40:710–6. doi: 10.1016/j.joen.2013.09.003. [DOI] [PubMed] [Google Scholar]
- 13.Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol. 1984;58:589–99. doi: 10.1016/0030-4220(84)90085-9. [DOI] [PubMed] [Google Scholar]
- 14.Gomes BP, Rodrigues HH, Tancredo N. The use of a modelling technique to investigate the root canal morphology of mandibular incisors. Int Endod J. 1996;29:29–36. doi: 10.1111/j.1365-2591.1996.tb01356.x. [DOI] [PubMed] [Google Scholar]
- 15.Green D. Double canals in single roots. Oral Surg Oral Med Oral Pathol. 1973;35:689–96. doi: 10.1016/0030-4220(73)90037-6. [DOI] [PubMed] [Google Scholar]
- 16.Rankine-Wilson RW, Henry P. The bifurcated root canal in lower anterior teeth. J Am Dent Assoc. 1965;70:1162–5. doi: 10.14219/jada.archive.1965.0189. [DOI] [PubMed] [Google Scholar]
- 17.Weine FS, Healey HJ, Gerstein H, Evanson L. Canal configuration in the mesiobuccal root of the maxillary first molar and its endodontic significance. Oral Surg Oral Med Oral Pathol. 1969;28:419–25. doi: 10.1016/0030-4220(69)90237-0. [DOI] [PubMed] [Google Scholar]
- 18.Weine FS, Pasiewicz RA, Rice RT. Canal configuration of the mandibular second molar using a clinically oriented in vitro method. J Endod. 1988;14:207–13. doi: 10.1016/S0099-2399(88)80171-7. [DOI] [PubMed] [Google Scholar]
- 19.Kartal N, Yanikoğlu FC. Root canal morphology of mandibular incisors. J Endod. 1992;18:562–4. doi: 10.1016/S0099-2399(06)81215-X. [DOI] [PubMed] [Google Scholar]
- 20.Gulabivala K, Aung TH, Alavi A, Ng YL. Root and canal morphology of Burmese mandibular molars. Int Endod J. 2001;34:359–70. doi: 10.1046/j.1365-2591.2001.00399.x. [DOI] [PubMed] [Google Scholar]
- 21.Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: An updated guideline for reporting systematic reviews. Int J Surg. 2021;88:105906. doi: 10.1016/j.ijsu.2021.105906. [DOI] [PubMed] [Google Scholar]
- 22.Munn Z, Moola S, Lisy K, Riitano D, Tufanaru C. Adelaide, South Australia: The Joanna Briggs Institute; 2017. Systematic reviews of prevalence and incidence. Joanna Briggs Institute reviewer’s manual; pp. 5–1. [Google Scholar]
- 23.Munn Z, Moola S, Lisy K, Riitano D, Tufanaru C. Methodological guidance for systematic reviews of observational epidemiological studies reporting prevalence and cumulative incidence data. Int J Evid Based Healthc. 2015;13:147–53. doi: 10.1097/XEB.0000000000000054. [DOI] [PubMed] [Google Scholar]
- 24.Naing L, Winn T, Rusli BN. Practical issues in calculating the sample size for prevalence studies. Arch Orofac Sci. 2006;1:9–14. [Google Scholar]
- 25.Rahimi S, Milani AS, Shahi S, Sergiz Y, Nezafati S, Lotfi M. Prevalence of two root canals in human mandibular anterior teeth in an Iranian population. Indian J Dent Res. 2013;24:234–6. doi: 10.4103/0970-9290.116694. [DOI] [PubMed] [Google Scholar]
- 26.Singh S, Pawar M. Root and canal morphology of mandibular incisors and canines in South Asian Indian population by canal staining and tooth clearing technique. Endodontology. 2016;28:148–53. [Google Scholar]
- 27.Costa FF, Pacheco-Yanes J, Siqueira JF, Jr, Oliveira AC, Gazzaneo I, Amorim CA, et al. Association between missed canals and apical periodontitis. Int Endod J. 2019;52:400–6. doi: 10.1111/iej.13022. [DOI] [PubMed] [Google Scholar]
- 28.Baruwa AO, Martins JN, Meirinhos J, Pereira B, Gouveia J, Quaresma SA, et al. The influence of missed canals on the prevalence of periapical lesions in endodontically treated teeth: A cross-sectional study. J Endod. 2020;46:34–9.e1. doi: 10.1016/j.joen.2019.10.007. [DOI] [PubMed] [Google Scholar]
- 29.Singh S, Ramachandran N, Podar R, Jain R, Bhanushali N, Kulkarni G, et al. Methods to study root canal anatomy: A systematic review. IJSR. 2021;10:27–31. [Google Scholar]
- 30.Neelakantan P, Subbarao C, Subbarao CV. 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. doi: 10.1016/j.joen.2010.05.008. [DOI] [PubMed] [Google Scholar]
- 31.Al-Qudah AA, Awawdeh LA. Root canal morphology of mandibular incisors in a Jordanian population. Int Endod J. 2006;39:873–7. doi: 10.1111/j.1365-2591.2006.01159.x. [DOI] [PubMed] [Google Scholar]
- 32.Arslan H, Ertas H, Ertas ET, Kalabalık F, Saygılı G, Capar ID. Evaluating root canal configuration of mandibular incisors with cone-beam computed tomography in a Turkish population. J Dent Sci. 2015;10:359–64. [Google Scholar]
- 33.Hess W, Zurcher E. London: Basle, Sons and Danielson; 1925. The anatomy of the root canals of the teeth of the permanent dentition and the anatomy of the root canals of the deciduous dentition and the first permanent molars. [Google Scholar]
- 34.de Almeida Gomes F, Barbosa RF, Mesquita YA, Ferreira CM, Teixeira RC, Viana LC. In vitro analysis of the internal anatomy of lower incisors by cone beam computerized tomography. RSBO Rev Sul Bras Odontol. 2017;14:80–05. [Google Scholar]
- 35.Benjamin KA, Dowson J. Incidence of two root canals in human mandibular incisor teeth. Oral Surg Oral Med Oral Pathol. 1974;38:122–6. doi: 10.1016/0030-4220(74)90323-5. [DOI] [PubMed] [Google Scholar]
- 36.Estrela C, Bueno MR, Couto GS, Rabelo LE, Alencar AH, Silva RG, et al. Study of root canal anatomy in human permanent teeth in a subpopulation of Brazil's center region using cone-beam computed tomography – Part 1. Braz Dent J. 2015;26:530–6. doi: 10.1590/0103-6440201302448. [DOI] [PubMed] [Google Scholar]
- 37.Madeira MC, Hetem S. Incidence of bifurcations in mandibular incisors. Oral Surg Oral Med Oral Pathol. 1973;36:589–91. doi: 10.1016/0030-4220(73)90318-6. [DOI] [PubMed] [Google Scholar]
- 38.Pécora JD, Sousa Neto MD, Saquy PC. Internal anatomy, direction and number of roots and size of human mandibular canines. Braz Dent J. 1993;4:53–7. [PubMed] [Google Scholar]
- 39.Walker RT. The root canal anatomy of mandibular incisors in a southern Chinese population. Int Endod J. 1988;21:218–23. doi: 10.1111/j.1365-2591.1988.tb00978.x. [DOI] [PubMed] [Google Scholar]
- 40.Ghabbani H, Marghalani A, Alabiri H. Assessment of root canal morphology of mandibular incisors using cone-beam computed tomography among residents of Al-Madinah Al-Munawara Region, Saudi Arabia. Eur J Gen Dent. 2020;9:40–4. [Google Scholar]
- 41.Peiris R, Pitakotuwage N, Kanazawa E, Dissanayake UB, Peiris R, Pitakotuwage N. Root canal morphology of permanent incisors and canines in a Sri Lankan population. Sri Lanka Dent J. 2008;38:15–23. [Google Scholar]
- 42.Kelsen AE, Love RM, Kieser JA, Herbison P. Root canal anatomy of anterior and premolar teeth in Down's syndrome. Int Endod J. 1999;32:211–6. doi: 10.1046/j.1365-2591.1999.00223.x. [DOI] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
FULL ELECTRONIC SEARCH STRATEGY OF MEDLINE PUBMED DATABASE