Discussion

One of the crucial factors that may affect the treatment outcome is knowing the anatomy of the root canal system and the anatomical variations in different types of teeth. The clinical importance of the present study is the coincidence of complex root canal curvatures (S-shaped canals) with RE, which confirms the rarity of the reported cases. The etiology of RE is not precisely known, but it is stated that external factors during odontogenesis can be one of its causalities. Ethnicity and genetic modifications can lead to more phenotypic manifestations of RE (8). The RE prevalence varies according to the ethnic group and up to 30% has been mentioned in studies \RL (3, 9). According to the location of the RE orifice, Carlsen and Alexandersen presented a classification (10): Type A: cervical part of RE located distally - two cone-shaped macrostructures Type B: RE cervical located distally - one cone-shaped macrostructure Type C: cervical part of RE located mesially Type AC: cervical part of RE located Centrally In addition to the classification mentioned above, De Moor et al (8) also provided another classification for RE, which was based on the curvature of the root or root canal: Type 1: without curvature (straight) Type 2: curvature located coronally - without curvature in the middle or apical Type 3: coronal curvature with the middle or apical second curvature RE creates an important challenge in the treatment process due to the root complex morphology and creating miss canal potentially. Due to the placement of the roots behind each other, there is a possibility of misdiagnosis. Therefore, the diagnosis of RE is necessary with a clinical examination along with a careful examination of radiographs, especially periapical radiographs (11). To diagnose RE, complementary angular radiography (mesial or distal) or using CBCT can be helpful. In addition to careful radiographic investigation, clinical examinations are important for the RE diagnosis. The use of periodontal probes, endodontic explorer, micro-opener, and path finder are among the instruments that can help in diagnosis. Also, examining the more prominent distal or distolingual occlusal lobe or the presence of an extra cusp can doubt the RE presence. In addition, it is worth investigating the champagne effect in the pulp chamber (12). One of the most important basic principles for RCT is the principle of Straight-Line Access (SLA). The RE presence may affect the way SLA is established and cause the access cavity to change from the classic triangular shape to larger dimensions such as a trapezoid or rectangle, of course, all these factors are also affected by the caries location. In these cases, Successful management of RE was achieved through thorough irrigation and shaping of the canal system using appropriate disinfectants. Also, using Nickel-Titanium rotary instruments enabled effective penetration in the root curves. Ni-Ti instruments can preserve the original shape of the canal and minimize procedural errors. A summary of some similar studies can be seen in the table below. As expected in the literature review, the principles of a successful RCT were observed in the studies (12-20). In all studies, the canals were irrigated with sodium hypochlorate with concentrations of 1 to 5.25% (12-20). EDTA has also been used as supplemental irrigation in most studies (12-16, 18-20). Like the present study, the use of the crown-down instrumentation technique was mentioned in two studies (12, 19). C-files (13, 14, 20) and K-files (12, 16, 17) for negotiation were mentioned in 3 studies respectively\RL. The use of Ni-Ti rotary systems was suggested in all studies (12-20). In the present study, obturation was performed using the warm vertical technique with gutta-percha and AH plus sealer. In line with the present study, AH plus sealer has been used repeatedly in studies (14, 15, 17-19). Among obturation methods, the continuous wave compaction technique has been the favorite of therapists (13, 15, 20). The comparison of these studies depends on the results of the treatment, and the treatment success will be evident with patients’ follow-up. Unfortunately, in the cited studies, unlike the present study, the follow-up result of the treatment was not mentioned. Of course, it should be mentioned that these studies are only a part of the existing literature review. The noteworthy point in the mentioned studies was the attention to the expansion of the access hole in the direction of better access to RE (14-16). Table A summary of the treatment of radix entomolaris case report studies