Research design
HMD
RECRUITMENT
This randomized controlled trial compared the control and experimental groups in a dental radiology class. To provide a VR experience using pHMD on a smartphone, we produced a 360° video for DR that can be played on a mobile device. The operator (dental hygienist; 17 years of DR experience) who performed DR wore a helmet (Zoot roing helmet, Foshan Nanhai Sunshine Sports Goods Co., LTD, Guangdong, China) fixed with a 360° camera. The training process for re-enacting the bisecting angle technique from the operator’s point of view was recorded as a 360° video, which was recorded using a GoPro Fusion camera (GoPro, San Francisco, the USA) (see Fig. 
A 360° video recording. Dental radiography using the bisecting angle technique from the operator’s point of view using a 360° camera. The operator controls the intraoral dental X-ray unit to explain the dental radiography process. C: 360° camera, IDU: Intraoral dental X-ray unit, O: Operator, P: patientParticipants were randomly classified into the control and experimental groups. The control group learned using a 2D video. The experimental group learned through 360° videos based on the VR using pHMD (Google Cardboard, Google LLC, California, the USA). Using Zoom video communications (Zoom, San Jose, the USA; The process of installing the YouTube application and using the VR function were explained to the participants in the experimental group. Hence, it can be used as an HMD by attaching a smartphone. Theoretical concepts of the bisecting angle technique were explained by instructors in 3-h online lectures viewed by participants in regular dental radiology classes. The online lecture video provides a theoretical explanation of the bisecting angle technique by the instructor. After regular dental radiology classes, all the participants additionally studied 1 h/week using 2D and 360° VR videos. These 2D and 360° VR videos are recorded re-enactments of the operator and patient’s bisecting angle technique. The control group learned through a 2D video, while the experimental group used the 360° VR video. In both groups, learning satisfaction was assessed once after the participants had used their respective mediums while self-efficacy was measured twice before and after exposure to each medium (see Fig. 
Participant recruitment and survey process. pHMD: Prefabricated head-mounted display