Combined Therapy for a Rare Case of Type III Dens Invaginatus in a Mandibular Central Incisor with a Periapical Lesion: A Case Report.

Type III dens invaginatus has a complex root canal structure that poses a greater challenge when endodontic treatment is necessary. Type III dens invaginatus rarely affects mandibular central incisors. In this case, we reported a combined therapy of type III dens invaginatus in a mandibular central incisor with a periapical lesion. Cone-beam computed tomographic (CBCT) imaging was used in the diagnosis and management of the unusual anatomy of dens invaginatus. First, the hard tissue of the dens invaginatus was removed using a dental operating microscope. The root canal was then prepared with a nickel-titanium instrument and filled with mineral trioxide aggregate and gutta-percha. Subsequently, a surgical treatment was performed using a dental operating microscope because the patient still had an apical infection after root canal treatment and the periapical lesion was not fully healed. In addition, the patient had requested a quick and thorough treatment for personal reasons. The granulomatous soft tissue was then curetted under local anesthesia followed by a surgical retrograde approach to negotiate and obturate the apical patent portion of the invagination. The bone window was filled with BonaGraft (YHJ Science and Trade, Beijing, China) and covered with a collagen membrane. The use of CBCT imaging and a dental operating microscope was important for ensuring a predictable outcome in this case.