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Objective To investigate and analyze the root and root canal morphology of mandibular first molars (MFMs) in the Tibetan population using cone-beam computed tomography (CBCT) and to provide references for clinical root canal treatment in the Tibetan population. Methods This study was reviewed and approved by the Ethics Committee, and informed consent was obtained from the patients. CBCT imaging data of 300 mandibular first molars from 300 Tibetan patients were included. Patient age, the number of roots in mandibular first molars were recorded. The morphology and incidence of mesial root and mesial root canals and the morphology and incidence of distal root and distal root canals were statistically analyzed by Vertucci classification. Results There were 198 double-root teeth and 102 three-root teeth in the 300 mandibular first permanent molars. Among the three-rooted molars, 1 case had mesiolingual roots, and the rest had distolingual roots. The incidence rate of the distolingual root was 33.7%(101/300). The most common root canal configuration was Vertucci Ⅳ 65.7% (197/300), followed by Vertucci Ⅱ 20.3% (61/300) in the mesial roots. The overall incidence of middle mesial canals (MMCs) was 6% (18/300), with the highest incidence of MMCs in the 20-40 year-old group at 9% (9/100). The distal roots canals of single-distal-rooted mandibular first molars were mainly Vertucci Ⅰ 66.8% (133/199), followed by Vertucci Ⅱ 14.6% (29/199) and Vertucci Ⅳ 11.6% (23/199). For the mandibular first permanent molars with two distal roots, 96% (97/101) of the distal buccal roots and 100% (101/101) of the distal lingual roots were Vertucci Ⅰ root canals. Conclusion The root and root canal morphology of mandibular first permanent molars in a Tibetan population is complex and variable. Approximately one-third of patients have distolingual roots, and clinicians should carefully explore the root canals under the guidance of CBCT.

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Aim: This study aimed to analyze incidence of isthmus in human permanent mandibular first molar teeth using cone-beam computed tomographic imaging techniques in a South Indian population. Materials and Methods: Three hundred permanent mandibular first molar teeth were collected, cleaned, and stored in normal saline. They were divided into groups (GPs) I and II based on number of roots, and were further subdivided (right and left [RL] subgroups A and B for GP I; and RL subgroups C and D for GP-II). Samples were processed and isthmus incidence was evaluated by cone-beam tomography, compared, and statistically analyzed. Results: Overall in mandibular first molars, the isthmus incidence in mesial root was 97.2%, distal root was 39%, and distolingual root was 0%. There was no statistically significant difference between the right and left mandibular first molar teeth with regard to incidence of isthmus (P > 0.05). There was an incidence of type I (38.67%), type II (56.33%), type III (3%), and type IV (2%) isthmuses in mesial root and type I (12.33%), type II (16%), and type III (10.67%) in distal root. Conclusion: Incidence of isthmus was very high in the mesial root of the mandibular first molar and should be factored during nonsurgical and surgical endodontic treatment procedures to achieve successful treatment outcomes.

Aim: This study aimed to analyze incidence of isthmus in human permanent mandibular first molar teeth using cone-beam computed tomographic imaging techniques in a South Indian population. Materials and Methods: Three hundred permanent mandibular first molar teeth were collected, cleaned, and stored in normal saline. They were divided into groups (GPs) I and II based on number of roots, and were further subdivided (right and left [RL] subgroups A and B for GP I; and RL subgroups C and D for GP-II). Samples were processed and isthmus incidence was evaluated by cone-beam tomography, compared, and statistically analyzed. Results: Overall in mandibular first molars, the isthmus incidence in mesial root was 97.2%, distal root was 39%, and distolingual root was 0%. There was no statistically significant difference between the right and left mandibular first molar teeth with regard to incidence of isthmus (P > 0.05). There was an incidence of type I (38.67%), type II (56.33%), type III (3%), and type IV (2%) isthmuses in mesial root and type I (12.33%), type II (16%), and type III (10.67%) in distal root. Conclusion: Incidence of isthmus was very high in the mesial root of the mandibular first molar and should be factored during nonsurgical and surgical endodontic treatment procedures to achieve successful treatment outcomes. [ABSTRACT FROM AUTHOR]

This case report describes a mandibular first permanent molar with five root canals, with two canals in the distal root & three canals in the mesial root. All five canals were observed to be independent, having individual orifices in the pulp chamber and individual apical foramina. [ABSTRACT FROM AUTHOR]

The distal root of the mandibular first permanent molar (MFPM) contains one or two canals. More rarely, the second/third distal canal is found in a separate root in a distolingual (DL) position - a radix entomolaris (RE). In Caucasians, this occurs in less than 4% of cases, but it is equally important to be aware of this possibility. Careful examination of the preoperative periapical radiographs (orthoradial and mesially angled) and inspection of the pulp chamber floor during endodontic management may indicate that this radicular variant is present. RE's lingual inclination and buccolingual curvature must be taken into account during cleaning and shaping of the canal within this root to avoid procedural errors, such as straightening and ledging of the root canal, perforation or instrument fracture. The aim of the present paper was to discuss a case report of a young patient, referred to an endodontic office after a ledge was created by inappropriate instrumentation of a buccolingually curved RE canal.