# Laser Doppler for Accurate Diagnosis of Oehler's Type III Dens Invagnatus: A Case Report
## 3 Discussion  
In a previous study, the pseudo canal was shown to be the usual site of origin of infection because the invagination acts as a region of stagnation for organic substances and provides a conducive environment for microbes [18]. The invagination of the enamel into the dental papilla results in a tunnel lined by dentin and enamel invaginating into the pulp [19]. In this case report, a necrotic invagination was debrided and filled, and the viable main root canal was followed-up [20]. However, as other major lesions were present, other dental specialists were consulted. A more accurate pulp diagnosis was required for the treatment plan [21; 22]. In 1964, the red blood cell velocity evaluation method of collecting frequency-shift signals using optical measurements and switching to a semi-quantitative mode after the measurement of blood flow and volume was first adopted [14; 23]. Doppler flowmetry has since been widely used to measure blood flow in soft tissues [24]. Since 1970, laser has been used in various clinical fields in Japan and Western countries. In the past decade, with advancements in medical laser devices, the use of lasers in the medical field has become more popular [25]. Laser Doppler mainly uses the Doppler effect to detect the pulp blood flow condition [26]. As a diagnostic technique for pulp disease, laser Doppler flowmetry (LDF) improves the accuracy of dental diagnosis, especially for traumatized and permanent teeth [27]. It reduces the diagnostic errors and improves the prognosis of the diseased teeth [9; 28]. Laser Doppler is a non-invasive, objective, painless, semi-quantitative method, proven to be reliable and reproducible by numerous studies [29]. Laser is used to detect the pulp blood vessels in which the red blood cells scatter the light beams and cause Doppler shifts [13; 30]. The objective data and imaging scans are presented. The calculated signals in the perfusion units represent the red blood cell density and velocity to evaluate the pulp vitality after trauma or pulp capping [29; 31]. Different from previous Doppler flowmetry studies that only recorded waves and data, we report for the first time, the use of laser Doppler blood flow monitor and imager (MoorLDI-2\(\lambda\)) to evaluate the pulp vitality in the dental field. As manufacturers have derived various high-end products from the standard models to satisfy applicability for medical research, this study adopted a new-generation laser Doppler blood flow monitor and imager (MoorLDI-2\(\lambda\)), which allows the observation of accurate images of low blood flow areas in the dental pulp under the slow scanning mode. It has higher sensitivity, wider dynamic range, and higher resolution compared with previous laser Doppler flowmetry (LDF). Through laser beam measurement, the mobile interference caused by traditional operators using the probe is reduced. It does not need to contact tissues, thus effectively avoiding infections and traumas to tissues. However, there are other limitations to the use of laser Doppler imager, such as the cost of the equipment and the interference by extraneous noise and movement near or in the apparatus itself. Contrary to previous reports, we directly presented the pulp-colored image of the anterior teeth to observe the pulp condition in the main root canal. In combination with the objective data, the perfusion units in the diseased tooth did not differ from those in two control teeth, indicating that the main root canal remained viable. The pulp tissues, rich in blood and lymphatic vessels and nerves, connects to the circulation through the root apex [32]. They contain the necessary components of the peripheral immune system and the stem cells responsible for pulp tissue regeneration. They produce the dentin, maintain dental nutrition and esthetics, conduct pain sensation, and produce protective responses against external stimuli [33]. Maintaining the pulp vitality helps extend the life of the diseased tooth.