CLINICAL MEDICINE

Detailed explanation-1: -The most common morphology of the maxillary first molar is three roots and four canals. However, the mesiobuccal root of the maxillary first molar often contains a double root canal system, and the incidence of a second mesiobuccal canal (MB2) has been reported to be between 18.6% and 96.1%[16].

Detailed explanation-2: -The two-rooted mandibular first molars usually have three canals. Two root canals are located in the mesial root and one root canal in the distal root. Hess8 reported that the prevalence of three root canals in mandibular permanent molar teeth was 78%.

Detailed explanation-3: -Mandibular first molars have either three canals (80 %) or four canals (20 %), the mesial roots usually have two root canals, and the distal root has one or two canals [ 4 ]. Mean root canal length of first mandibular molar: mesiobuccal 16.4 mm, mesiolingual 14.2 mm, distobuccal 13.1 mm, and distolingual 12.7 mm [ 9 ].

Detailed explanation-4: -The mesiobuccal canals are usually the most challenging to instrument as they leave the pulp chamber in a mesial direction before curving distopalatally. The second mesiobuccal canal is, generally, very fine and may join the main canal.