A 14-year female presented with an atypical looking tooth #7 with a sinus tract on tooth #8. A gutta-percha point inserted into the sinus tract confirmed the affected tooth #7. A radiographic examination of tooth showed a lateral radiolucency with respect to tooth #7. Cone-beam computed tomographic imaging was done for the three-dimensional reconstruction analysis. Dens invaginatus (Oehler's type III) with pulp necrosis and chronic apical periodontitis was the definitive diagnosis. Use of the dental operating microscope and ultrasonics helped in the removal of the invaginated structure. At the two year follow-up, no clinical and radiographic evidence of infection was observed.