Prevalence of a Second Root and Canal in Mandibular and Maxillary Canines in a Saudi Arabian Population: A Cone-beam Computed Tomography Study

INTRODUCTION

Increasing knowledge of root canal morphology is essential for proper root canal treatment (RCT). Anterior teeth in the maxillary jaw mostly have a simple and straightforward morphology that generally presents with one root and one canal. Mandibular anterior teeth have a more complex anatomy and the presence of two canals is common.^1–5 Mandibular permanent canines typically have a single root with one root canal.^4,5 Many studies on mandibular canines from different populations reported the presence of up to two roots and two canals with Vertucci’s types I–IV canal configurations.^6–12 Two-rooted mandibular canines have reached 5%^5,7, while single-rooted canines with two root canals were reported to be approximately 15%.^1,4,13

In a Saudi Arabian population, only one recent in vivo cone-beam computed tomography (CBCT) study evaluated the anatomy of permanent mandibular canines.¹⁴ In this study, the authors evaluated 454 mandibular canine teeth and found that a single-rooted canine with Vertucci’s type I classification was the most prevalent type (95.4%). Two-rooted mandibular canines comprised 0.2% and two canals were present in 4.6% of the cases. The remaining studies conducted with the same population were case reports of anatomical variations.^15–18

Conversely, few studies have evaluated the morphology of permanent maxillary canines. Maxillary canines usually present with a single root and a single canal; the presence of two roots or canals is rare.^2,19 In recent in vivo CBCT studies among different populations, Martins et al.³ reported that out of 962 teeth, maxillary canines exhibited one root (100%) and one canal (98.6%) and the presence of two canals was 1.4%. Pan et al. found all maxillary canines having one root and one canal Vertucci’s type I.²⁰

An extensive literature search revealed no studies that reported anatomy of permanent maxillary canines and only one study evaluated permanent mandibular canines in a Saudi Arabian population. Therefore, the present study evaluates (a) the prevalence of a second root and canal in mandibular and maxillary canines, (b) gender differences, and (c) bilateral symmetry of canines morphology in a Saudi Arabian population using in vivo CBCT.

MATERIALS AND METHODS

CBCT images were retrieved from the database of College of Dentistry, Jazan University, Jazan, Saudi Arabia from 2016 to 2018, following receipt of the Institute’s ethical research approval. This study included mandibular and maxillary permanent canines with fully developed roots and closed apices. This study excluded root canal-treated, calcification, resorption, or distorted CBCT images. The CBCT machine used in this in vivo retrospective study was a 3D Accuitomo 170 (MORITA, Japan) with the scanning parameters: FOV 170–120 mm, 90 kV, 5–8 mA, 17.5 seconds exposure time, and 0.250 mm voxel size. All CBCT images were processed and reconstructed using Morita’s i-Dixel 3D imaging software, and acquired serial axial, coronal, and sagittal sections to evaluate external and internal morphology of maxillary molars. The same endodontist assessed the CBCT images twice, with a 5-week interval in between each assessment, and evaluated the following parameters:

• The number of roots, number of canals, and canals' configurations according to Vertucci's classification (Fig. 1) in mandibular and maxillary permanent canines.
• The prevalence of a second root and a second canal.
• Differences between genders.
• Bilateral symmetry of the number of roots, number of canals, and canals configurations.

RESULTS

For reliability, one observer (the author) evaluated 30% of the total sample twice with an interval period of 5 weeks in between each evaluation. Results of Cohen’s Kappa test revealed an almost perfect agreement between observations with a value of 85.8% and asymptotic standard error of ±9.8%.

DISCUSSION

Researchers have investigated root canal anatomy using different in vitro and in vivo techniques and, recently, the use of in vivo CBCT has become paramount to obtaining proper details of the root canal morphology during the dental visit.^21,22 CBCT is a 3D technology with low radiation dose,²² which allows for the examination of a relatively large sample size safely and noninvasively to achieve a reliable prevalence.^3,23

The present in vivo CBCT study investigated the prevalence of a second root and canal of mandibular and maxillary canines. The prevalence of two roots and two canals in mandibular canines was 2.7% and 9.3%, respectively. In teeth with two canals, internal configurations were Vertucci’s type III in 6.1% and type V in 3.2%. Our results revealed a higher prevalence than a finding in a recently published study in a Saudi subpopulation,¹⁴ where they reported 0.2% and 4.6% for roots and canals, respectively. The authors of that study found Vertucci’s canal configuration types I–IV in teeth with two canals. In the same study, Aldahman et al.¹⁴ evaluated 454 mandibular canines using in vivo CBCT in a central region of Saudi Arabia (Riyadh city). The differences and inconsistencies of their results and ours might be explained by the regional differences where the study samples were obtained, since our sample came from the southern region of Saudi Arabia (Jazan city). Additionally, the small sample size in both studies might be another reason for the differences, suggesting the need for a larger sample size from different regions of the country to extract outcomes that are more reliable.

Other studies from different populations found two-rooted mandibular canines to be in a range of 0–11.54%^6–12 and two canals in a range of 0–15.1%.^{4,6,7,9–13,20,24–31}

In maxillary canines from the present study, there were no two-rooted teeth and only 1% two canals were present. Vertucci’s canal configuration type III appeared in teeth with two canals. Our results are consistent with those of an in vivo CBCT study from a Portuguese population in which all teeth showed only one root and two canals present in only 1.4% of 962 maxillary teeth with Vertucci’s type II, III, or IV in canines with two canals. A 2019 in vivo CBCT study in Malaysian population reported only one root and one Vertucci’s type I canal classification in 404 maxillary canines.²⁰ Our study is the first in a Saudi population that evaluated maxillary canines and it seems that the presence of two roots or canals is rare in this population as well.

Concerning gender, our study showed no significant differences in the number of roots and canals in males and female in both mandibular and maxillary canines. However, there was a statistically significant difference (near to the cutoff point p = 0.049) between genders regarding canal configurations, where Vertucci’s types III and V were more prevalent in females than in males, and type I was more prevalent in males than in females. This finding is in partial agreement with a study of the same population on mandibular canines in which there was no significant difference in the number of roots between genders, although the presence of two canals was significantly higher in males.¹⁴ This study is in contrast with our findings regarding canal configurations, where types II, III, and IV canal configurations were more prevalent in male patients and type I in female patients with a statistically significant difference between the two.

Pan et al.²⁰ reported results similar to ours, noting no differences between genders in regard to the number of roots and canals. Soleymani et al.¹² studied an Iranian population that showed that males have a higher prevalence of two roots and double canals in mandibular canines; in contrast, a study of a Portuguese population by Martins et al.³² revealed that women had significantly more roots and root canals than men.

In maxillary canines, our result is consistent with other studies from different populations^20,32 in that studies showed no differences between males and females in regard to the number of roots and canals.

The present study also investigated bilateral symmetry and found high bilateral symmetry 95.5%, 91.1%, and 90.1% for the number of roots, number of canals, and canal configurations, respectively, in mandibular canines. These findings are consistent with two studies carried out in Saudi¹⁴ and Iranian¹² populations, which reported a high probability of bilateral symmetry of 97.% and 95.4% in the number of roots and canal configuration, respectively.

Maxillary canines showed higher similarities in the left and right sides, with 100% for the number of roots, 98.9% for the number of canals, and 98.9% for canal configurations. There were no studies to compare bilateral symmetry of maxillary canines; however, it was not of clinical significance. In contrast, the asymmetry in the number of canals (8.9%) and canal configurations (9.9%) of mandibular canines could be of clinical significance when a practitioner treats opposing canines in the same patient. The researchers of a 2019 systematic review of 102,610 teeth using in vivo CBCT from 28 countries concluded that some groups of teeth had a similar morphology among different populations, such as maxillary anterior teeth, while other groups of teeth showed a range of diversity.³³ Therefore, the results of this anatomical study on mandibular and maxillary canines were within the global range and did not show notable diversity.

CONCLUSION

Within the limitations of the present study, mandibular canines showed a higher prevalence of two roots and canals (2.7% and 9.3%, respectively) compared to maxillary canines (0% and 1%, respectively). Gender had no association with the number of roots and canals in mandibular and maxillary canines. Mandibular canines showed higher asymmetries in the number of roots (4.5%) and in the number of canals (8.9%) when compared to maxillary canines (0% and 1.1%, respectively). Therefore, this finding could be of clinical importance in RCT related to mandibular canines.

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