Prevalence of Middle Mesial Canals and Isthmi in the Mesial Root of Mandibular Molars: An In Vivo Cone-beam Computed Tomographic Study



      Many studies have investigated the morphology of the mandibular molar, but the prevalence of the middle mesial (MM) canal in the mesial root of the mandibular molar is still the subject of controversy. In addition, in previous literature, a true MM canal has not been clearly distinguished from an isthmus between the mesiobuccal and mesiolingual canals. Therefore, the objectives of this study were 2-fold:
      • 1.
        To identify the prevalence of a true MM canal and/or isthmus in the mesial root of mandibular molars using a sample of cone-beam computed tomographic images
      • 2.
        To analyze the configuration of MM canals and isthmi in the mesial root of mandibular molars


      Ninety limited field of view cone-beam computed tomographic scans were observed. One hundred twenty-two mature mandibular first and second molars with no previous root canal treatment, no root resorption, and intact crowns were retrospectively evaluated. Data regarding the sex, age, presence of MM canals, and number of root canals in the mesial root were recorded.


      Of the 122 teeth, 20 (16.4%) had true MM canals. The prevalence of MM canals was 26% in first molars and 8% in second molars (P < .05). The frequency of isthmi in the mesial roots was 64.7%. The frequency of isthmi was higher in second molars, but the difference was not statistically significant (P > .05).


      This study showed a high prevalence of mandibular molars with MM canals or isthmi. The detection and biomechanical cleaning of these areas during nonsurgical or surgical root canal treatment are critical.

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