RESUMEN
Normally, the permanent mandibular first molar has two roots, mesial and distal. However, mandibular molars may have anadditional root located either buccally (radix paramolaris) or lingually (radix entomolaris [RE]). Understanding of the presence ofan additional root and its root canal, anatomy is essential for successful treatment outcome. The aim of this paper is to reviewthe prevalence and morphology of RE and to present two cases of permanent mandibular first molars with an additional thirdroot (RE) in the Indian population. In this study, we did a clinical investigation of two cases; one case of successful endodonticmanagement of permanent mandibular first molar characterized as RE, whereas the second one is a presentation of a case ofsevere bone loss around permanent first molar with an additional third root. The presence of an additional third root in permanentmandibular first molars may affect the prognosis of the tooth if it is misdiagnosed. Thus, an accurate diagnosis and thoroughunderstanding of variation in root canal anatomy are essential for treatment success.