# Study of Root Canal Length Estimations by 3D Spatial Reproduction with Stereoscopic Vision
## 1 Introduction  
In medical education, there is a desire for an environment that enables the acquisition of both accurate knowledge and skills. To facilitate the acquisition of such knowledge and skills, technologies such as virtual reality (VR), which artificially creates spaces that can be experienced as if they were real, and augmented reality (AR), which overlays computer graphics (CG) onto real-world spaces, have been developed. The effectiveness of these technologies in medical education has been reported with head-mounted displays (HMD) in the form of goggles or glasses [1, 2]. These technologies, including VR, AR, and mixed reality (MR), are collectively referred to as extended reality (XR). They allow the display of computer-generated images (CGI) in the wearer's field of view, bridging the gap between the real world and virtual reality [3, 4]. Anatomical training using VR, such as skull models and models of the middle and inner ear, has been shown to have comparable learning effects to conventional teaching methods in medical students [5, 6]. Furthermore, VR has been shown to be an effective method for improving anatomical knowledge, while increasing learner motivation, compared to other educational approaches [7, 8]. In addition, AR and MR have been shown to be superior to traditional methods for skill acquisition in the development of injection needle insertion techniques [9]. In dental education, the use of head-mounted displays (HMDs) to replicate VR and AR environments has allowed for the observation of areas not directly visible to the naked eye [10; 11]. Furthermore, VR-based skill acquisition for maxillofacial surgery trainees has been found to be superior to traditional skill acquisition methods [12], and the use of AR for local anesthesia training for dental students has been reported to allow for faster task completion compared to traditional methods [13; 14]. In addition, the acquisition of cavity preparation skills in conservative dentistry typically requires the consumption of tooth models with each training session, but the use of VR has still been shown to improve the efficiency of skill acquisition [15]. AR/VR applications have been evaluated as being accessible without time constraints and are capable of providing comprehensive educational support to students in undergraduate and graduate dental education [16]. However, skill acquisition devices for dental practice, such as those represented by Simodont (MOOG, Nieuwgeein, The Netherlands), have been reported to be prohibitively expensive, thus posing a challenge for widespread adoption [17]. On the other hand, head-mounted displays (HMD), which are wearable devices, allow for accurate stereoscopic viewing, but they require the interpupillary distance (IPD) to be adjusted for each user and to be reflected in the device [18]. It has also been reported that even after wearing the HMD, differences in the sense of physical distance to objects within the field of view can be perceived [19]. Furthermore, fatigue has been observed when using HoloLens as an HMD due to its 500 g weight, making it less suitable for long-term training [20]. In 2020, a high-resolution stereoscopic display (SRD: Sony, ELF-SR1, Tokyo, Japan, 2020) was developed that allows a naked-eye viewing of three-dimensional images without the need for any device attachments. In dental education, the use of the SRD for the practical training of head and neck anatomy among dental students showed a correlation between the comprehension of anatomical knowledge and the amount of information displayed on the SRD [21]. In addition, the SRD has been reported to have the potential to reduce the effects of convergence and adaptation problems associated with conventional HMDs [22]. Our aim was to investigate the application of 3D computer graphics (3 DCG) in the initial measurement of root canal treatment in endodontics. Root canal length measurement is performed by two reliable methods: electronic apex locators and dental radiography.