## 1 Introduction  
While the conventional workflow depends on the operator's experience and technique, the introduction of computer-aided design and computer-aided manufacturing (CAD/CAM) has made it possible to apply the digital workflow in the field of dentistry [1; 2; 3; 4; 5]. The first digital workflow was a partially digital workflow accompanied by intraoral impression-taking and the production of a working model [1; 2; 3] The introduction of intraoral scanners in the 1980s allowed the use of a fully digital workflow [1; 3], which reduced the errors that may occur from the operator's experience and the materials (impression material and plaster) used [1; 2; 3]. The recent digital workflow in dentistry has been improving the range of application and the accuracy of prosthetic fabrication due to the continuous development of dental CAD/CAM system [6]. The concept of intraoral scanner was first introduced for chairside use to perform fixed prosthetic treatment [1, 5]. However, it can be applied to many other treatments including removable prosthetic treatment, orthodontic treatment, and implant procedure planning [7]. Faster and easier scanning of teeth and soft tissues in the oral cavity and 3D modeling suggest that it could be applicable in more areas [8]. In addition, intraoral 3D modeling may play an important role in the communication between the dentist, dental technician, and the patient [5]. A previous study compared the accuracy of a virtual model scanned from the actual oral cavity and that of a virtual model scanned from a working model [9]. Also, it was found that intraoral conditions (saliva and limited space) contribute to the inaccuracy of scanning [9, 10, 11]. In case of difficulty in using an intraoral scanner due to the intraoral conditions, a partially digital workflow (intraoral impression taking and working model production) can be applied [1, 5, 12]. In many studies, the accuracy of the scanning data was evaluated for application in various treatment methods and to test intraoral scanners under limited conditions in the oral cavity [7, 8, 10, 13, 14, 15, 16, 17]. The accuracy of the CAD test model (CTM) obtained with an intraoral scanner is evaluated through three-dimensional (3D) comparison with the CAD reference model (CRM) obtained with a scanner with very high accuracy [7, 8, 10, 13, 14, 15]. Using a 3D inspection software, the CTM and CRM are superimposed to the most similar position, and the mean of the distance of all point clouds of 3D modeling of CRM and CTM was used to calculate the root mean square (RMS) [8, 13, 15]. In addition, the RMS value is the standard for the evaluation of the accuracy of the scanning data in many studies [13, 14, 15, 17]. The previous studies found that deviation of more than 100 \(\upmu\)m from the complete arch resulted in an inaccurate fit of the final restoration in the maxilla and mandible [3, 9] Also, an allowable range of less than 100 \(\upmu\)m was proposed as an acceptable cement space for the prosthesis [3, 18]. The accuracy of intraoral scanners for a complete arch has been evaluated in many previous studies [3, 8, 10, 13, 14, 15, 17, 18, 19]. It was found that the larger the range of scanning, the greater the error, suggesting that the complete arch was inappropriate as the range of intraoral scanning for prosthetic treatment [3]. The limited intraoral condition, the impact of the scanning accuracy on the prosthesis, and the impact of the increase in the range of scanning on the accuracy have been investigated for the development and application of intraoral scanners [3, 7, 8, 10, 11, 13, 20, 21, 22, 23]. However, there are no studies investigating the accuracy of intraoral scanning according to the tooth type, and the anterior and posterior regions. In addition, there are few studies evaluating the scanning accuracy of a complete arch [10, 14, 15].