Saudi Endodontic Journal

REVIEW ARTICLE
Year
: 2020  |  Volume : 10  |  Issue : 1  |  Page : 1--6

Root canal morphology of primary mandibular second molar: A systematic review


R Mahesh1, MS Nivedhitha2,  
1 Department of Pedodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India
2 Department of Conservative and Endodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Chennai, Tamil Nadu, India

Correspondence Address:
Dr. R Mahesh
Department of Pedodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Poonamalle High Road, Chennai - 600 077, Tamil Nadu
India

Abstract

For many years, it has been the constant endeavor of researchers to understand the complexities of root canal anatomy. This systematic review aimed to analyze the root canal morphology of primary mandibular second molar using different diagnostic aids in different ethnic population. An exhaustive search was undertaken to identify published literature related to the root anatomy morphology of the primary mandibular second molar. Using a combination of keywords, search was done up to August 2018 in PubMed, The Cochrane Central Register of Clinical Trials, and Science Direct. The included data consist of type of population, number of teeth per study, number of root canals, and type of root canal configuration. A total of 10 articles were selected for the review. The most common morphology in primary mandibular second molar consists of 3 canals (two mesial and one distal) in 63% of the teeth examined. The mean root length was estimated to be 8.2 mm in the mesial and 8.6 mm in the distal roots. The review concluded that there are variations in canal morphology and number of canals based on the ethnic origin of the study population. The common canal morphology in primary mandibular second molar is 2 separated roots (mesial and distal) with 3 canal systems. Vertucci's Type IV (22) and Type I (11) canal configurations were the most prevalent in the mesial and distal roots, respectively.



How to cite this article:
Mahesh R, Nivedhitha M S. Root canal morphology of primary mandibular second molar: A systematic review.Saudi Endod J 2020;10:1-6


How to cite this URL:
Mahesh R, Nivedhitha M S. Root canal morphology of primary mandibular second molar: A systematic review. Saudi Endod J [serial online] 2020 [cited 2020 Feb 29 ];10:1-6
Available from: http://www.saudiendodj.com/text.asp?2020/10/1/1/274185


Full Text

 Introduction



Root canal configuration plays an important role in biomechanical preparation and removal of root canal debris, which can contribute to endodontic success.[1] Therefore, clinicians need to understand the precise root morphology, pulp chamber, and canal configuration of all groups of teeth. For many years, it has been the constant endeavor of researchers to understand the complexities of root canal anatomy. Although cone beam computed tomography (CBCT) offers a three-dimensional view of the canal morphology, the cost and amount of radiation exposure makes it difficult to a routine application in children.[1],[2],[3],[4],[5]

The root canal morphology of primary molars exhibits a more complex morphology with regard to root canal curvature, pulp chamber volume, and accessory canals when compared to permanent molars.[6] In the primary teeth exists a discrepancy in the carious prevalence in both the arches being the mandibular arch more affected than the maxillary arch. This may be explained because of the high prevalence of occlusal caries in mandibular second primary molar due to the deep pits and fissures seen in occlusal anatomy.[7],[8],[9],[10],[11] Besides, high sugary dietary patterns accompanied with poor oral hygiene in young children result in early carious lesion in the primary molars. In addition, the enamel dentin thickness is comparatively less mineralized and thinner in primary molars which can eventually results in early pulpal involvement.[7],[8]

Radiographs still remain as the main diagnostic aid to determine the extent of carious lesion and identification of canal morphology. It is not expensive and produces less radiation when compared to other diagnostic aids such as CBCT or spiral CT.[1],[2],[3] However, ex vivo studies have been done with the use of micro-CT and histopathological examination, which remain the gold standard procedures for studying root canal morphology.

Systematic review remains at the highest level in the hierarchy of research as it allows a top down approach to locate the best evidence for any research question. This systematic review aimed to analyze the root canal morphology of primary mandibular second molar which can help the clinician during endodontic procedures.

 Structured Question



Is there a variation in canal morphology in primary mandibular second molar with different diagnostic aids and in different ethnic population?

 Search Strategy



Search strategy was based on PubMed Central, Cochrane Database, LILACS, Science Direct, Web of Science and SIGLE and was completed by a manual cross-reference search.

PICO analysis

Patient – children (2–12 years)Comparison – various diagnostic aidsOutcome – canal morphology of primary mandibular second molarStudy design – in vitro and in vivo studies.

Search methods for identification of studies

For the identification of studies to be included for this review, detailed search strategies were developed for each database searched up to August 2018. The following specialized computer databases were used to retrieve articles for the review:

PubMedThe Cochrane Central Register of Clinical TrialsScience DirectLILACSSIGLEThe search term combination for electronic databases was as follows: MeSH headings, text words, and word variants for “primary tooth” and “root canal anatomy” and “diagnostic aid” were combined using Boolean operator.

Search strategy

Search 1 – PubMed (MeSH terms) and (keywords)

The following MeSH terms and keywords were combined with Boolean operator: (“X-Ray Micro tomography” [Mesh] OR “Negative Staining” [Mesh] OR Clearing technique OR “Radiography, Dental” [Mesh] OR “Radiography, Dental, Digital” [Mesh] OR “Spiral Cone-Beam Computed Tomography” [Mesh] OR “Cone-Beam Computed Tomography” [Mesh] AND “Dental Pulp Cavity” [Mesh] AND “Tooth, Deciduous”[Mesh]) [Figure 1].{Figure 1}

Inclusion and exclusion criteria

Studies were selected using the following predefined inclusion criteria:

All studies including

In vivo studiesIn vitro studies.

Studies were excluded using the following predefined exclusion criteria

All studies including

All tooth except primary mandibular second molarCase reports.

Search 2 – hand searching

Hand searching was done for the following journals from 2000 to August 2018:

Journal of Clinical Pediatric DentistryPediatric DentistryJournal of EndodonticsInternational Endodontic Journal.

Data collection and analysis

Screening and selection

Two review authors (MR and MS) independently assessed the titles and abstracts of studies resulting from the searches. Full articles of those studies which met the inclusion criteria, or for which there were insufficient data in the title and abstract to make a clear decision, were retrieved. MR assessed the full text papers independently to establish whether the studies met the inclusion criteria or not. Studies fulfilling the inclusion criteria were then underwent quality assessment and data extraction. The data were analyzed according to the ethnicity of the population and demographic status, number of teeth per study (power), number of roots present, number of root canals, method of tooth analysis, root canal patterns, and number of apical foramina. The root canal morphology, the mean distance between central fissure and pulp chamber, and height of pulp chamber were also evaluated.

Data were extracted independently and in duplicate by two review authors (MR and MS). Titles of articles relevant to the review were selected by discussion. Thirty-nine were identified from the electronic and hand-searched. Abstracts and full texts of the articles were reviewed independently. Articles were selected after discussion, and 29 studies were rejected. After reviewing the articles independently, ten articles were selected.

 Results



A total of 935 primary mandibular second molars were examined in 10 studies, of which were performed using CBCT (n = 3), micro-CT (n = 2), clearing technique (n = 2), CT scan (n = 1), spiral CT (n = 1), and radiography (n = 1) [Table 1].{Table 1}

[Table 2] shows the selected studies with respect to number of roots and canals. A total of 8 studies evaluated the number of roots and canals in primary mandibular second molar. The most common canal morphology was two canals in mesial and one canal in distal root. The common root canal configuration was 2 roots (one mesial and one distal) in 95.5% of the teeth examined. Vertucci's Type IV (2-2) canal configuration was the most prevalent in mesial root and Type I (1-1) canal configuration in the distal root [Table 3]. The most frequent root shapes were flat (82.9%), followed by separated (9.6%) and conical (7.5%). With respect to individual roots, mesial (78.95%) and distal roots (86.84%) were most common. When the relationship between the external root morphology and the root canal type was evaluated, it was found out that Type IV was the most frequently observed root canal type in all three root shapes [2] [Table 4].{Table 2}{Table 3}{Table 4}

[Table 5] shows that the average lengths of mesial and distal roots were 8.2 mm and 8.6 mm, respectively. The root canal length varied from 6.9 mm in mesial and 6.6 mm in the distal canal.[4] When the canal morphology was examined, mesial canal was classified as round in 30%, ribbon-shaped in 60%, and irregular in 10% of the specimens, while distal canal was round in 40%, flat-oval in 20%, and ribbon-shaped in 40% of the roots.[7] The most common canal internal morphology was ribbon shape in both the mesial and distal canals. When two separated canals were observed in the distal root, it was classified as Vertucci's Type IV configuration and the mesial root was more curved/angulated (36.2°) than the distal root (25.8°).[12] With regard to the pulp chamber morphology, the mean distance between the central fissures to furcation was 7.26 mm. Mean distance between central fissures to floor of pulp chamber was 5.54 mm and mean height of pulp chamber was 1.88 mm.[6]{Table 5}

Considering the population examined, there were studies from Turkey, Indian, China, and Iran [Table 1]. Only one study did not mention the ethnic background of the population.[7] With respect to the evaluated population, no consistency was observed among the studies in sample size and diagnostic aids. Two studies from Turkey used CBCT for the evaluation of canal morphology.[2],[4] While one reported study with a sample size of 228 primary molars showing Vertucci's Type IV canal morphology in almost 50% of the teeth examined,[2] the other reported that mesial root had 2 separate canals in 95.5% of the cases and 2 distal canals in 12.2% of the sample (n = 90).[4]

 Discussion



A successful root canal treatment needs a thorough understanding on the internal and external root canal morphology of the particular teeth. Most of treatment failures are due to improper or failure to diagnose additional root canal which may lead to an inadequate debridement of the canal system.[6],[7],[8]

The study done by Demiriz et al.,[2] Katge and Wakpanjar,[3] and Bagherian et al.[10] confirmed that the most common mesial root canal morphology was Vertucci Type IV in >50% of the sample examined, while the distal root showed predominantly Vertucci's Type I configuration. On the other hand, Yang et al.[8] showed that 72.28% of the mandibular primary molars had two separate roots, while 27.52% had three roots, and only one sample had four roots. Bagherian et al.[10] identified that 95.5% of the sample had two roots (mesial and distal) and only 1 out of 22 samples had three roots (mesiobuccal, mesiolingual, and distal). These variations in the number of roots could be explained by differences in the ethnic origin of the sample collected, with Chinese population showing a higher percentage for 3 root molars when compared to the other examined populations. A definite conclusion cannot be drawn because of the inconsistency in the sample size and the diagnostic aids used in various studies.

Ozcan et al.,[4] using CBCT method, concluded that the average root length of mandibular primary second molars ranged from 8.2 to 8.6 mm in the mesial and distal roots, respectively, similarly to Bagherian et al.[10] (Clearing Technique) and Zoremchhingi et al.[12] (CT scan). In summary, these studies demonstrated that distal root length were 0.4–1.2 mm longer than the mesial root length.

Only one study evaluated the mean distance between the central fissure to furcation, which were 7.26 mm in average.[6] Distance between central fissure to floor of pulp chamber was 5.54 mm and the height of pulp chamber was about 1.88 mm.

Primary mandibular second molars have been usually described as having two grooved and divergent roots that flare to accommodate the developing permanent premolars.[10] Two canals in the mesial root and one canal in the distal root comprised the most commonly reported anatomical configuration in this group of teeth.[6],[8],[9],[10] It is difficult to analyze the canal morphology with the use of radiographs because the image of the canal overlaps in a two-dimensional radiograph. On the other hand, ex vivo studies in extracted primary teeth have a limitation of a very less sample size because of physiological and pathological resorption.[3],[10]

Vertucci's canal configuration system has been used as standard reference to classify the canal morphology in research studies. Advanced diagnostic aids such as micro-CT and CBCT provided a better and detailed understanding of the canal morphology compared to conventional radiography and clearing techniques.[7],[9],[12],[14] Although computed tomography is a good method for studying the morphology of root canals, it requires an expensive special device and trained personnel. Radiation safety dosage must also be considered when exposing children for advanced imaging modalities.

This systematic review analyzed the secondary data from various published research articles, which may include biases and drawbacks related to sampling method, study population, inter- or intra-examiner reliability, and investigation methodology. Hence, the main intention of this research was to provide a detailed review in the variation in canal morphology and root canal length in mandibular second primary molars.

 Conclusion



This systematic review identified that morphology of the primary second molar showed variations in the population studied and also regarding the diagnostic aid. The most common morphology of primary mandibular second molar in most of the studies was 2 separate roots (mesial and distal) with 3 canal systems. Vertucci's Type IV canal configuration was the most prevalent in mesial root and Type I canal configuration in the distal root, while the most common canal morphology was ribbon shape, in both roots. Whenever there is an additional root in distal aspect, 4 root canals (2 mesial and 2 distal canals) were reported.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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