C-shaped root canal systems in mandibular second molars in an Emirati population
The effect of ethnic groups on the root and canal morphology of the mandibular second molar is well documented in the literature.4, 5, 15. In addition, the mandibular second molar is the most common tooth to exhibit a C-shaped canal morphology.3. Here, we studied the root and canal morphology of the mandibular second molar in the UAE population. We have also described and studied the changes in the C-shaped configuration along the length of the root. This is an effort to fill knowledge gaps related to this population and an attempt to describe C-shaped molars as a single unit.
In the present study, the most common root morphology of mandibular second molars consisted of two distinct roots (78.3%), one mesial and one distal. The other types of root morphology observed were single taper root (2.4%), three root (0.8%), and four root (0.6%) molars. Similar results of the presence of two roots followed by 3 roots in the mandibular second molars have been reported in several studies.16, 17. The prevalence of mandibular three-rooted second molar documented in other populations ranges from 0.26 to 8.98%5, 18, 19. The third root observed in our study was found lingual in 75% of cases, which is in agreement with the reports of other populations.17, 20, 21. Therefore, despite the low prevalence, clinicians should be aware of these morphological variations in the number of roots, to successfully manage endodontic treatment in these cases.
According to our results, CV type I (90.5%) was the most prevalent configuration in the distal root. However, type II (46.5%) and type III (39.4%) CVs were the most common root canal configurations in the mesial root. Contrary to our results, type II and type IV CVs were more frequent in the mesial root of most of the other populations studied.16, 18, 22, 23. The high prevalence of CV type III in the mesial root has been reported in very few studies (range 26.2-48.45%)15, 24, 25. According to our results, Vertucci Type VI, VII and VIII were not detected in the sample of mandibular second molars examined. This is in agreement with several other published studies.18, 19. Therefore, our results showed that type II VC is the most common canal configuration in the mesial root in the Emirati population. Thus, clinicians treating this population should pay particular attention to the management of the mesial root of the non-C-shaped mandibular second molar. Modifications to the cleaning and shaping technique may be considered to avoid tearing. the common apical foramen and avoid stripping, rim and fracture of the instrument26. In addition, the second most common canal configuration in the mesial root is type III VC. Therefore, clinicians should look for a second channel even if there is a coronally orifice. Failure to detect and treat the second canal can lead to endodontic failure.
There is wide variation in the prevalence of C-shaped mandibular second molars depending on ethnicity and the population studied. The prevalence in different populations ranged from 3 to 48.7%5, 19 (Fig. 6). According to our results, the prevalence of C-shaped mandibular second molars in the Emirati population was 17.9%. The prevalence is relatively higher compared to other Middle Eastern countries such as Saudi Arabia 7.9-12.57%27, 28 and Turkey 4.1 to 10.6%22 but lower than that of the Chinese, Korean and Malaysian population (44-48.7%)5, 19. In addition, our analysis showed that the C-shaped molars were significantly higher in women than in men (P 4, 5.
In addition, the effect of ethnicity has also been reported on the configuration of the C-shaped channel at different thirds of the root. In the Iranian population, the most common coronary canal configuration was C1 (50%), in the middle C3d (32.9%) and apical C3d (36.6%)29. While in Saudi Arabia, C3c was most common (37.1%) in the coronal third, C3c (32.3%) in the middle third and C3d (30.6%) in the apical third30. In the present study, the most common root canal configuration in mandibular C-shaped molars at the coronary, middle and apical level was C1 (41.75%), C3c (51.7%) and C3d (65.9%, respectively. ).
In the present study, the majority of mandibular C-shaped second molars had a lingual root groove (88%) while only 12% had a buccal root groove. Our results are similar to those of Jin et al. and Kim et al. in the Korean population31, 32, Martin et al. in the Portuguese population33 and Alfawaz et al. in the Saudi population30, in which the prevalence of the buccal root sulcus was lower than that of the lingual root sulcus (prevalence of 1 to 22.6% of the buccal root sulcus). Contrary to our results, Ladeira et al. observed the presence of an oral root groove in more than two-thirds (69.4%) of the C-shaped mandibular second molars in the Brazilian population34. As documented, the dentin thickness is at least at the level of the groove area35. Therefore, it is important to know the location and direction of the groove to avoid over-preparation of the canal in this region, which can lead to iatrogenic perforation.
Additionally, we observed a change in coronary to apical C-shaped canal configuration in 94.5% of the C-shaped mandibular molars studied. This is similar to the results of Zheng et al. in the Chinese population6. While the change in channel configuration was only observed in 66% of the C-shaped molars of the Korean population32. However, the types of morphological change along the root of the C-shaped channel configuration have not been studied in these populations. Describing the changes in the morphology of the C-shaped channel along the root may provide researchers and clinicians with a better understanding of C-shaped molars as a single unit. This will allow the development of new treatment strategies to manage these teeth. Here we attempted to study such a change and our analysis revealed 4 common types of morphological change in the C-shaped mandibular second molars. Specifically, the most common type was T1: C1-C2-C3d (18 %) followed by T2: C1-C3c-C3d (15.4%), T3: C4-C3c-C3d (7.7%) and T4: C3c-C3c- C3d (7.7%). This finding could indicate an effect of ethnicity on the presence of specific types of morphological change in C-shaped channel configuration in some populations. However, further studies in other populations are needed to confirm such an association. This information, if available, can help clinicians manage these cases, in addition to other available tools and techniques.
The C-shaped canal configuration with the presence of narrow ribbon and fan shaped areas, transverse anastomoses, lateral canals and apical delta make cleaning and shaping of these teeth difficult2. With the relatively high prevalence in the Emirati population, clinicians should consider using advanced tools to diagnose and manage such complex anatomy as CBCT.ten, Dental operating microscope36, advanced irrigation activation and distribution systems (such as passive ultrasonic and negative pressure irrigation, laser activated irrigation)37.38.39 and calcium hydroxide as an intracanal drug3. Additionally, since the most common types of morphological change in the C-shaped molar end with apical C3d, clinicians should be sure to locate and clean both canals to avoid failure.
One of the limitations of our study is that it is a retrospective study, hence the inability to control certain factors such as FOV, voxel size and the quality of the CBCT image. Therefore, in the present study, the overall image resolution and quality was influenced due to the medium-sized (8cm × 8cm) FOV CBCT FOV scans. However, the voxel size used was 0.15 which is considered acceptable compared to other studies.40. In addition, more studies are needed in different populations to determine the effect of ethnicity on the pattern of change of the C-shaped molar along the length of the root. Another limitation of this retrospective study is that ethnicity was determined based on UAE nationality. Therefore, the data may not represent the entire population of UAE, as UAE nationals make up almost 11% of the total population.41.42.43. However, the results of this study are important for clinicians treating UAE nationals, as there is general agreement that there is little variation in ethnic groups among UAE nationals.41.