Mandibular permanent second molar with four roots and root canals: a case report.

Although four-rooted mandibular first molars have been observed on a few occasions in the literature, to the best of our knowledge, four-rooted second molars have not been reported. Here, we describe a mandibular second molar with four roots and canals: two mesial and two distal. Mesial roots were separated in the cervical one-third near the cervical margin, while distal roots were divided at a lower level in the middle one-third of the root. We discuss the possibility of different root and canal variations of the mandibular second molar from a developmental point of view.