RESUMEN
The cases presented here aim to highlight the occurrence of a very rare internal root resorption (IRR) of inflammatory type among mandibular molars (prevalence 0.01%-1%). Patients reported in the outpatient department with a chief complaint of pain in the lower posterior region of the jaws, on thorough clinical and radiological examinations a diagnosis of irreversible pulpitis was made and nonsurgical root canal treatment was planned using thermoplastic obturation technique along with the use of magnification, cone-beam computed tomography, endosonics, and intracanal medicament to attain a successful outcome. Six-month follow-up showed arrest of IRR. This report of two cases with a literature review discusses the etiology, prevalence of IRR, the clinical decision, and the therapeutic management. Early detection of such resorption is the key to successful management and preserves the integrity of the tooth.