Saudi Endodontic Journal

: 2023  |  Volume : 13  |  Issue : 1  |  Page : 1--8

Root and root canal morphology of permanent mandibular premolars in Saudi Arabian population: A literature review

Roqayah Aljuailan 
 Department of Conservative Dental Sciences, College of Dentistry, Qassim University, Buraydah, Kingdom of Saudi Arabia

Correspondence Address:


Introduction: Thorough knowledge of the teeth's root and root canal morphology is vital before obtaining access to endodontic therapy. This study aimed to undertake a comprehensive literature review of the root and root canal anatomy of the mandibular premolars in several provinces of Saudi Arabia. Materials and Methods: The PubMed and Scopus databases were screened for relevant literature. Included studies reported data on the number of roots, root canals, canal configurations, and anatomical variations of mandibular premolars in the Saudi population. Gender morphological differences and bilateral symmetry have also been reviewed, along with case reports of anomalies. Results: Fifteen studies that fulfilled the inclusion criteria were included. The weighted average of single-rooted teeth is 91.4% of the mandibular first premolar and 96.7% of the second premolar. Studies of the internal canal morphology revealed that two or more canals were found in 21.5% of the first premolar and 7.1% of the second premolar. Type I Vertucci canal configuration is the most prevalent in mandibular premolars. The multi-rooted or multi-canalled system variants were frequently reported in the clinical case reports. Conclusion: Mandibular first premolars have a higher incidence of multi-canal system than second premolars, hence clinicians should be attentive to the possibility of an extra canal in these teeth. Few studies are available that discuss the root canal morphology of mandibular premolars in the Saudi population, and further studies with a larger sample size covering Saudi Arabia's provinces are indicated.

How to cite this article:
Aljuailan R. Root and root canal morphology of permanent mandibular premolars in Saudi Arabian population: A literature review.Saudi Endod J 2023;13:1-8

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Aljuailan R. Root and root canal morphology of permanent mandibular premolars in Saudi Arabian population: A literature review. Saudi Endod J [serial online] 2023 [cited 2023 Feb 3 ];13:1-8
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Successful surgical and nonsurgical root canal treatment starts with proper knowledge of the external and internal morphology of teeth and possible variations in anatomy. For adequate root canal treatment, location of all canals, biofilm disruption through chemo-mechanical instrumentation, and three-dimensional obturation of the root canal system is mandatory.[1],[2] For endodontic microsurgery, a root-end amputation of 3 mm is required to eliminate the majority of apical ramifications and lateral canals.[3] Advancements in endodontic surgical techniques have improved the management of the apical root anatomy and, consequently, enhanced treatment outcomes.[3]

Mandibular premolars accounted for 10%–11.6% of endodontically treated teeth.[4],[5] During endodontic treatment, recognizing extra root and root canals in mandibular premolars when they are present is essential to avoid treatment failure in these teeth.[6],[7] The frequency of untreated canals in mandibular premolars was 6% of the teeth treated.[8]

Many techniques have been used to study human teeth's root and root canal morphology.[9] Recently, cone-beam computed tomography (CBCT), when indicated, has been used to evaluate the root canal anatomy because it facilitates diagnosis and provides clinicians with three-dimensional information about the morphology of roots, their divergence, and the relation of teeth to the surrounding structures.[10] Mandibular first premolars (MnFPs) and mandibular second premolars (MnSPs) showed one root and one canal system with high frequency in the morphological studies.[11],[12]

In the perusal of the literature studying root canal morphology of different populations, variations in the occurrence of anatomical features are found.[13],[14],[15],[16],[17],[18] Therefore, to help better understand and improve the quality of the provided treatment, in-depth knowledge of morphological features of different populations is essential. Thus, the aim is to review the available literature on mandibular premolars' internal and external morphology in several provinces of Saudi Arabia, relate the root and root canal morphology to the patient's gender, and investigate the degree of bilateral symmetry of these teeth.

 Materials and Methods

Literature search strategy

An electronic literature search has been conducted including PubMed and Scopus databases. A combination of the following search keywords was used: “Mandibular premolar,” “mandibular bicuspid,” “number of roots,” “number of canals,” “root canal morphology,” “extra roots,” “dental anomalies,” “abnormal root morphology,” and “Saudi population\subpopulation.” In addition, to ensure that all possible studies were included, the bibliography of eligible articles, previous literature review articles,[15] and issues of the Saudi Endodontic Journal were manually checked. A total of 321 studies were found in the preliminary search.

Inclusion and exclusion criteria

Anatomic studies and clinical case reports that evaluated the root and root canal morphology of mandibular premolars of the Saudi Arabian population that were published in peer-reviewed journals were included in the current review. Search results include reports in English with no time limits. One case report[19] and two anatomic studies[16],[20] did not report the patient's nationality and so were excluded. Studies that did not examine the anatomical variation feature in each specific premolar tooth were also excluded. After the removal of duplication, retrieved abstracts of published manuscripts were scanned for eligibility by one author. Inconclusive abstracts and potential articles were retrieved in full text.

Data extraction and analysis

Fifteen studies fulfilled the inclusion criteria [Figure 1]. The publication date, authors, number of specimens/patients, and methodology were recorded. Data extracted include:{Figure 1}

The number of roots and root canals per toothType of root canal configuration per tooth according to the eight Vertucci's classification.[12] Additional canal configurations reported were categorized as “others” [Table 1]Distribution of morphological features of the root and root canal system according to the patient's genderBilateral symmetry of the root and root canal morphologyMorphology of apical region, accessory canals, inter-canal communications, and isthmusesStudied anatomical variation feature (e. g., C-shaped canal system) and its frequency.{Table 1}

Data were recorded in an Excel spreadsheet, and weighted averages of the studied morphological features (e.g., single canalled) were obtained by dividing the total number of teeth with that feature by the total number of samples in all studies that evaluated it.

The clinical case reports data were extracted as follows:

Patient's personal information (age and gender)Type and side of premolar tooth studied [FDI (Federation Dentaire Internationale) notation system]Management performed (clinical examination, radiographic examination, or clinical procedure)Reported anatomic variation feature.


Overall, 15 relevant studies that evaluated the root and root canal morphology of mandibular premolars were included in this review.[21],[35] A total of 3143 patients were included in the anatomic studies covering the Central, Northern, Southern, and Western provinces of Saudi Arabia (one study did not report the number of subjects). Regarding gender distribution, 1483 were males and 1494 were females with ages ranging from 15 to 78 years (two did not report the gender and age distribution). Teeth were examined by in vivo CBCT scans, except in one study[23] that used the tooth clearing technique of extracted MnFPs.

External morphology

The root anatomy of mandibular premolars was investigated by 7 studies including 2300 MnFPs and 4306 MnSPs.[21],[27] The weighted average showed MnFP and MnSP had one root in most of the instances (91.4% and 96.7%, respectively). MnFP showed extra roots in an average of 8.6% of the teeth examined, while MnSP had a lower frequency of multi-rooted external anatomy (3.35%) [Table 1].

Internal morphology

In respect of root canal morphology, 7 studies examined the root canal morphology of mandibular premolars including 2300 MnFPs and 4306 MnSPs.[21],[27] MnFP had a higher incidence of more than one canal system (21.5%), whereas MnSP showed a lower percentage (7.1%). Type I root canal configuration was the most prevalent in the included studies for both MnFP and MnSP [Table 1]. The average of the studies that examined canal configurations showed the possible instances that the mandibular first premolar has more than one apical foramen (Types IV, V, VI, VII, and VIII) in 14.99% of teeth. However, it is 1.26% in the mandibular second premolar [Table 1].

Boreak et al.[21]described root canal cross-sectional shape (RCCSS) of mandibular premolars, and they found that the most recurring coronal cross-section in mandibular first and second premolars was oval. In contrast, the most frequent RCCSS in the middle and apical sections was found to be circular. Chourasia et al. examined the number of lateral canals and inter-canal communications in MnFP; lateral canals were found in 38% of the teeth examined, and inter-canal communications in 16%.[23]

Gender differences and bilateral symmetry

Five studies [Table 2] evaluated the morphological gender distribution of morphologic features, including 1756 teeth (890 male and 866 female) for MnFP[22],[24],[25],[26] and 3874 teeth (1979 male and 1895 female) for MnSP[22],[25],[26],[27] [Table 2]. The average of the two-rooted MnFP occurred more frequently in males; however, MnSP showed an almost similar distribution concerning the number of roots. For the number of root canals, the occurrence of two canal systems in both MnFPs and MnSPs was slightly higher in males compared to females.{Table 2}

Three studies[22],[27],[28],[29],[30] assessed the bilateral occurrence of morphological features of the left and right sides of the patients using in vivo CBCT. One of them[30] showed less bilateral symmetry of canal configuration type than the other two studies. [Table 3] summarizes their results.{Table 3}

Anatomical variation studies and clinical case reports

Two studies included in this review report the frequency of the C-shaped canal system in mandibular premolars evaluated by CBCT.[28],[29] In the average of the two studies, MnFP had a C-shaped canal in 8%; in comparison, MnSP had a 3.9% frequency. In addition, radicular grooves affecting mandibular premolars were studied by Srivastava et al.,[28] and they found a prevalence of 13% in MnFP and 4.3% in MnSP.

Five case reports with eight teeth were included in this study.[31],[32],[33],[34],[35] The multi-rooted or multi-canal system commonly reported morphological variation in clinical case reports in mandibular premolars [Table 4].{Table 4}


The findings of anatomic studies showed a variation in the anatomy of human teeth, and many of these factors were studied, one of which is ethnicity differences.[16],[17],[18] The current review assessed the observational studies that investigated root canal morphology of mandibular premolars in several provinces of Saudi Arabia. In addition, the analyzed data have been extracted from studies with variations in their study design and sample number. Out of ten anatomic studies conducted in four provinces, over 6600 teeth were investigated.[21],[22],[23],[24],[25],[26],[27],[28],[29],[30] All studies except one included in this review used in vivo CBCT as the examination method that could approximate the clinical conditions. CBCT three-dimensional image is an invaluable tool for assessing the morphology of the teeth.[10]

Mandibular first premolar had one root in 91.4% and showed an 8.6% frequency of multi-rooted tooth presentation. Trope et al. found a significant difference between African American (16.2%) and Caucasian (5.5%) patients for the prevalence of two-rooted MnFPs.[36] Regarding the number of canals, MnFP showed a 21.5% incidence of a multi-canal system. In addition, the average of studies investigating canal configurations showed a single canal system from the canal orifice to the apex (Type I) in 75.8% of the teeth examined. In comparison to the previous studies of the other populations, a frequency of 24% of an Indian population,[37] 22% of a Spanish population,[38] 34.8% of a Chinese population,[7] 38.8% of an Egyptian population,[39] 39.5% of a Turkish population,[40] and 41.8% of a Jordanian population[41] were reported to have more than one canal system.

MnSPs had a single root in most instances (92.8%). However, it showed a multi-canal system in an average of 7.1% of the included studies, which is lower than the mandibular first premolar. Moreover, this frequency occurred within the range reported in the literature examining MnSP in different populations. Those studies reported a frequency of 2.2% of a Chinese population,[42] 8.75% of an Iranian population,[43] 9.4% of a Spanish population,[38] 28% of a Jordanian population,[41] 29% of a Turkish population,[40] and 42% of Indian population.[37] In general, MnSP had a lesser frequency of more than one root canal compared to the first premolars in different populations.[17],[18] The average of studies examining canal configurations showed a high prevalence of Type I canal configuration (96.9%).

In the present study, the appearance of one-rooted MnFPs was on an average higher in females than males, and in the same frequency in MnSPs. In addition, females showed a tendency to have a single canal in both mandibular premolars. Thanaruengrong et al. investigated the prevalence of bifurcation and trifurcation of mandibular premolars, and the Chi-squared test results indicated no relationship between the gender and the prevalence of a bifurcation or trifurcation.[44] In the same study, their results indicated a high probability of finding an extra canal branching from the main root canal in the middle third level of the mandibular first and second premolar at 75.5% and 50%, respectively.[44]

Data provided in the relevant studies showed that mandibular premolars are expected to have symmetrical morphology in the number of roots almost 100% of the time. However, the canal configuration type had a slightly less tendency for bilateral symmetry. Felsypremila et al. found a 96.1% bilateral symmetry in the number of roots and canals in MnFPs and 98.3% in MnSPs.[45] A study that investigated the bilateral appearance of the same root canal configuration identified its presence in 80.3% and 95.9% of the mandibular first and second premolars, respectively.[44]

The C-shaped canal system affects mandibular premolars with a lower frequency than molars, and MnFP has a higher frequency than MnSP.[29] Yu et al. examined the frequency of the C-shaped canal system in the Chinese population, and it affected 1.1% of the first premolars and 0.6% of the second premolars.[42] Thanaruengrong et al. assessed the prevalence of C-shaped canals in mandibular premolars, and they found 20.9% and 0.6% in the mandibular first and second premolars, respectively, and this was not related to the patients' gender.[44] Additional root or root canals in mandibular premolars are the most common reported morphological variation in the Saudi population. Case reports that described two or more roots and root canals in mandibular premolar teeth are found in the literature.[46],[47],[48]

The impact of root canal anatomy on teeth with a preoperative disease can be recognized from outcome studies. Despite improvements in chemo-mechanical preparation techniques, this has not increased the success rate of nonsurgical root canal treatment over the past century.[49],[50] Thus, well-established infections in complex root canal morphology are difficult to eradicate. Thorough knowledge of the normal root canal anatomy, the potential occurrence of varying anatomy, and improving the manners of eradicating infection from a complex root canal system are needed. Proper interpretation of straight and angled periapical radiographs with the help of a dental operating microscope and CBCT imaging may aid in locating and managing an extra root canal in lower premolars.

One of the limitations of this review is the combined data covering different provinces of Saudi Arabia which could affect the findings. In addition, variability in methodology of the included studies e.g., variation in inclusion criteria. Moreover, studies that assessed differences among gender are few and from different provinces. Hence, further studies with a sufficient sample size covering the entire Saudi Arabia region assessing gender and age effects are advisable. Available CBCT scans in the different centers across the kingdom provide sufficient samples to be used in morphological studies and allow evaluation of teeth noninvasively and assessment of patient-related factors.


Studies investigating MnFPs' anatomy showed an increased possibility of more than one canal presentation than the second premolars. Among case report studies, the multi-canal system is commonly reported morphological variation. Therefore, efforts should be made for locating extra canals in mandibular premolars during endodontic treatment to avoid treatment failure. Few studies are available investigating the Saudi population's root canal morphology and its variation in mandibular premolars.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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