# Laser Doppler for Accurate Diagnosis of Oehler's Type III Dens Invagnatus: A Case Report
## 2 Case Report  
A 31-year-old Taiwanese woman underwent orthodontic treatment in the hospital and the routine examination revealed a large peri-invagination lesion with a unique root canal shape in the upper right lateral incisor; therefore, she was referred to Endodontics and Operative Dentistry department of Kaohsiung Medical University Chung-Ho Memorial Hospital. The patient had fair oral hygiene, with no systemic diseases, food or drug allergies, or history of dental trauma. Intraoral examination revealed normal soft tissues with no swelling or sinus tracts. Clinical imaging revealed a peg-shaped clinical crown with no caries or fillings. However, brackets and wires were present in the maxillary teeth with no tenderness or pain on percussion (Figure 1). The tooth responded normally to thermal and electric pulp testing (Parkell pulp vitality tester, Farmingdale, NY, USA). Moreover, teeth 11 and 13 also showed normal responses to both thermal and electrical pulp testing. Tooth mobility was grade I. A 4-mm periodontal pocket was detected in the buccal area. We can observe the radiolucent invagination from the periapical film (Figure 2a), which looks like a tooth is inside another. A radiopaque invagination of the dentin lined by the enamel could be observed in the crown. A \"pseudo-canal\" was located near the mesial side and extended from the enamel invagination to approximately the cemento-enamel junction, spreading and forming the opening of the pseudo canal, with a lesion at the mesial and lateral part of the root. Considering the irregular shape, root resorption in the \"pseudo-canal\" was suspected. Figure 1: Clinical examination. **(a)** Intraoral examination of a 31-year-old woman showing normal soft tissue. **(b)** Incisal view of tooth 12 showing a Peg-shaped clinical crown. We decided to investigate further with CBCT because of the complex anatomy of tooth 12. As expected, the CBCT scan (EPX-Impla; E-Woo Technology, Yongin, Korea) revealed a type III invagination. We can observe from the CBCT coronal view that the pseudo canal was located near the buccal part, while the CBCT sagittal view showed that the buccal side of the pseudo canal with the opening of the invagination near the cemento-enamel junction, and it was adjacent with a well-defined unilocular peri-invagination radiolucent lesion measuring 8 mm (mesiodistal) \(\times\) 9 mm (labiopalalal) \(\times\) 12 mm (craniocaudal) (Figure 3). Figure 2: Periapical films during the treatment procedure. (**a**) X-ray showed that the radiolucent invagination looks like a tooth inside another. Additionally, there was dentin invagination lined by enamel into the main canal space, spreading into the mesial part of the middle root. Tooth 12 appeared to be associated with a large peri-invagination radiolucent lesion around the opening of the invagination near CDJ. (**b**) Measurement of the working length. (**c**) Mineral trioxide aggregate was used to seal the invagination. (**d**) Follow-up at two postoperative years. The patient complained of no clinical symptoms, and the peri-invagination lesion had healed significantly. Three-dimensional CBCT aided the diagnosis and provided additional information on the root canal during the treatment procedure. A diagnosis of [PERSON]'s type III DI with necrotic invagination and asymptomatic peri-invagination periodontitis was made. We decided to proceed with the vital pulp therapy of the main canal, followed by nonsurgical endodontic treatment for the pseudo root canal, after discussing the treatment plans with the patient. According to previous literature [10], the invagination is the usual site of origin of infection. The main canal is still vital with no other symptoms; therefore, follow-up was recommended. Regarding the pseudo canal, it was infected, and root canal therapy was advised. Due to the necrotic invagination, either apexification or revascularization can be selected. The dentin thickness was sufficient, and it had an open apex on the middle part; therefore, an operation will not be time-consuming.