Root Canal Morphology and Configuration of 118 Mandibular First Molars by Means of Micro–Computed Tomography: An Ex Vivo Study

• Root canal configuration frequency in the mesial root: 2-2-2/2 (31.4%), 2-2-1/1 (15.3%), 2-2-2/3 (11.9%) of maxillary first molars.
• Root canal configuration frequency in the distal root: 1-1-1/1 (58.5%) and 1-1-1/2 (10.2%) of maxillary first molars.
• Connecting canals frequency between the mesiobuccal and mesiolingual root canals in the coronal (20.3%) and middle (14.4%) thirds.
• Accessory apical foramina frequency in the mesiobuccal (1-4; 24.6%), mesiolingual (1-3; 28.0%), distolingual (1-4; 23.7%) and distobuccal (1; 3.4%) root canals.
• The mesiobuccal, mesiolingual, and root canals showed accessory canals in the middle third in 18.6% and 33.9%, whereas the distobuccal and distolingual showed accessory canals in this third in only 4.2% and 4.2%.
• The mesiobuccal root canal had 1–4 accessory apical foramina in 24.6%, and the mesiolingual had 1–3 accessory apical foramina in 28.0%. The distolingual root canal showed 1–4 accessory apical foramina in 23.7%, and in the distobuccal root canal only 1 foramen (3.4%) was observed.

IntroductionThe aim of this study was to investigate the root canal system morphology of the mandibular first molar by means of micro–computed tomography.MethodsThe root canal configuration, foramina, and accessory canals frequency of 118 mandibular first molars were investigated by means of micro–computed tomography and 3-dimensional software imaging. A 4-digit system describes the root canal configuration from the coronal to apical thirds and the main foramina number.ResultsThe most frequent root canal configurations in mesial root were 2-2-2/2 (31.4%), 2-2-1/1 (15.3%), and 2-2-2/3 (11.9%); another 24 different root canal configurations were observed in this root. A 1-1-1/1 (58.5%), 1-1-1/2 (10.2%), and 16 other root canal configurations were observed in the distal root. The mesiobuccal root canal showed 1–4 foramina in 24.6%, and the mesiolingual showed 1–3 foramina in 28.0%. One connecting canal between the mesial root canals was observed in 30.5% and 2 in 3.4%. The distolingual root canal showed 1–4 foramina in 23.7%, whereas a foramen in the distobuccal root canal was rarely detected (3.4%). The mesiobuccal, mesiolingual, and distolingual root canals showed at least 1 accessory canal (14.3, 10.2, and 4.2%, respectively), but the distobuccal had none.ConclusionsThe root canal configuration of mandibular first molars varies strongly. According to our expectations, both the mesial and distal roots showed a high number of morphologic diversifications. The root canal system of the mesial root showed more root canal configuration variations, connecting and accessory canals than the distal root.