Internal morphology of distal roots of mandibular first molars revealed by computed microtomography

To evaluate the internal morphology of 100 distal roots of mandibular first molars using micro‐CT. Teeth were scanned to characterise: Vertucci type, root length, canal shape, presence and location of accessory canals, and the number of foramina at 4 mm from the apex, presence of root isthmus and the length from the primary canal to the apical foramen. Vertucci type I was found in 57% of cases, followed by V (27%). The most common cross‐section 1 mm from the apex was oval (49%) and circular (38%). The average root length was 16.06 mm (16.61–19.02 mm). The mean foramen size was 0.32 and 0.53 mm for the minor and major diameters, respectively. The volume, surface area and SMI were 7.84 mm 3 , 68.87 mm 2 and 1.52 mm, respectively. Root isthmi were found in 47% of the samples, and the length mean from the primary canal to the apical foramen was 2,03 mm. The internal morphology of the distal roots of mandibular first molars may be complex and shows variations.