A rare case of dilated invaginated odontome with talon cusp in a permanent maxillary central incisor diagnosed by cone beam computed tomography
A healthy 24-year-old male patient visited the Department of Conservative Dentistry and Endodontics with complaints of mild pain and swelling in relation to a maxillary left central incisor that had lasted for a week. Extraoral examination revealed no abnormality. On intraoral examination, the right mandibular first molar, which had been extracted a few months earlier due to caries, was missing. There were metallic restorations in some posterior teeth. The left maxillary central incisor had a diffuse concavity in the mid labial surface, and the tooth was labially placed in relation to the other maxillary incisors (). On the palatal aspect, a pronounced cingulum, or talon cusp (Type I), was observed (). The tip of the talon cusp had a deep pit formation. The tooth did not respond to an electric pulp test. The tooth was tender on percussion.\nConsidering the unusual anatomy observed clinically, it was decided to perform CBCT imaging (Kodak 9500 Cone Beam 3D system, Carestream Health Inc., Rochester, NY, USA) in order to evaluate the anatomy radiographically and reach a treatment plan. The exposure parameters of CBCT were 90 kVp tube voltage, 10 mA tube current, and the images were obtained with a voxel size of 0.20mm×0.20 mm×0.20 mm. The exposure time was 10.8 seconds. The images were examined with Carestream 3D Imaging software (Atlanta, GA, USA). The CBCT panoramic image of the affected tooth () showed an image resembling a wide immature root apex. Based on the image and clinical symptoms, a treatment of apexification with mineral trioxide aggregate (ProRoot MTA, Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) would usually have been considered. However, as the pulp space in the crown portion was not clearly visible on the panoramic radiograph, CBCT reconstructed 3D images were examined in order to further evaluate the anatomy of the tooth prior to attempting endodontic treatment. The images focusing on the maxillary left central incisor were also obtained in sagittal, coronal, and axial planes of 200-µm slice thickness.\nThe reconstructed 3D CBCT images of the involved tooth revealed a complex structure comprising a ring-like formation of the root, and the labial view showed the root surface to be much broader than the contralateral incisor (). The parasagittal sections of the CBCT clearly showed the invagination between the crown proper and talon cusp and extending beyond the crown root junction, at which point the invagination dilated to form a huge ring-like structure in the root. The talon cusp also showed the presence of traces of pulpal tissue within (). The CBCT axial images revealed the pulp space to be compressed and discontinuous within the ring ().\nBased on the clinical and radiographic findings, the diagnosis of dens invaginatus of the most severe variant, termed dilated invaginated odontome, was made in the maxillary left central incisor with talon cusp associated with periapical pathology. As the CBCT revealed a very complex root canal anatomy not amenable to successful cleaning and shaping, the choice of surgical or non-surgical endodontics was ruled out. This was explained to the patient, consent obtained, and the tooth was extracted under local anesthesia. Histological examination was performed for the soft tissue within the ring-like structure. After extirpation of the soft tissue, a distinct invagination pit formation was seen at the beginning of the dilation of the root (). The histological examination of the contents of the invagination revealed that it was not pulp tissue but comprised of a vascular fibrous connective tissue exhibiting a mixed inflammatory cell infiltrate comprising polymorphs, lymphocytes, plasma cells, and focal aggregates of Russell bodies. Basophilic material suggestive of microorganisms was also present ().