Frequency of middle mesial canal and radix entomolaris in mandibular first molars by cone beam computed tomography in a selected Iranian population

Although there are many studies about the internal anatomy of mandibular molars, there is still controversy over the frequency of middle mesial canals and isthmuses in the mesial root of mandibular molars and distolingual third root (Radix entomolaris) that  it can be seen in any population, but it is more frequent in Asians and makes endodontic treatment difficult. Because of limited studies on the middle mesial canal, isthmus in north of Iran; therefore, the aim of this study was to investigate the frequency of these variations in the north of country.

 In this retrospective cross-sectional study, The cone beam computed tomography (CBCT) images of 200 mandibular first molar teeth without any root canal treatment and completely erupted and developed were evaluated. Samples with open apex, internal root resorption, calcification, crown and extensive restoration were excluded. The patients’ gender, age, tooth location (left and right), count of canals in the mesial root, presence or absence of isthmus in mesial root, middle mesial canal and isthmus level in the mesial root and distolingual root (Radix entomolaris) were studied in three groups based on age; <20, 20-40 and >40.

From 200 samples, 18 teeth (9%) had middle mesial canal, 38 teeth (19%) had isthmus in mesial root and 6 teeth (3%) had distolingual root (Radix entomolaris).

due to the high frequency of isthmuses, middle mesial canals and Radix entomolaris in the population, which cannot be ignored, missing and treating these spaces could be one of the main reasons for failure in root canal treatment. Therefore, it is advised to put more effort into detecting and completely clean and obturate these spaces in surgical and non-surgical endodontic treatments.