Virtual reality technology using a 360° video: development and evaluation of an educational tool for intraoral radiography using the bisecting angle technique

Intraoral radiography (IOR) practice education is essential for dental students. However, the risk of radiation exposure has resulted in the use of textbooks to learn IOR. Thus, a new educational tool that can effectively use fewer shots or provide indirect experience when practice is not feasible is needed. In this study, we developed a new educational tool called “educational media for the bisecting angle technique” using virtual reality (EMBAT-VR) and evaluated the user experience among students. IOR was divided into 12 steps for 14 teeth, and a scenario was prepared from the perspectives of the operator and patient. On the basis of this scenario, the IOR was reenacted and recorded using a 360° camera. The tool was built on a head-mounted display using the Unity Engine. Eighty-four students were enrolled to evaluate the task performance, browsing search, and satisfaction on a 5-point Likert scale; the corresponding values for the tests were 3. 78 ± 0.70, 3.88 ± 0.76, and 4.01 ± 0.71, respectively. EMBAT-VR was used to investigate the satisfaction (user experience). Responses to 21 questions from 24 students who used traditional textbooks (control group) and 22 students who used the VR educational tool (experimental group) were statistically analyzed using the Mann–Whitney U test. A statistically significant difference was observed between the experimental (4.16 ± 0.64) and control (2.69 ± 0.54) groups. In the usability evaluation, EMBAT-VR presented with a higher score than traditional textbooks. Nonetheless, its effect when performing actual IOR imaging needs follow-up research.


Introduction
Dental radiography is an oral examination method used to accurately verify the condition and pathological examination of tooth roots and alveolar bones that are difficult to examine visually (Gröndahl 1992).The accuracy of the dental radiograph influences the accurate diagnosis of several oral diseases.Dental radiography is divided into two types based on the location of the dental X-ray film: extraoral radiography and intraoral radiography (IOR) (Kullman and Al Sane 2012).Extraoral radiography uses a panoramic dental X-ray machine to evaluate the overall structure of the jawbone and teeth, whereas IOR uses an intraoral dental X-ray machine to confirm the apical, proximal, and occlusal conditions of the teeth (Tugnait et al. 2003).In particular, IOR is frequently used to provide detailed information about the areas surrounding the teeth.
IOR can acquire dental radiographic images of the tooth and jawbone using various methods, such as the bisecting angle technique (BAT), paralleling technique, and bite-wing technique.Depending on the type of IOR used and the skill of the operator, additional information regarding the alveolar bone and pathology around the teeth can be obtained in more detail compared with that obtained with extraoral radiography (Vandenberghe et al. 2010).For students, BAT is one of the most complex and challenging IOR techniques to learn.Acquiring dental radiographs using accurate and proficient IOR is essential.The shooting method can be incorrect if the obtained dental radiographic consists of a distorted image of the oral environment.When the position of the dental X-ray sensor and the vertical and horizontal angles of the tube head of the digital X-ray machine are incorrect during IOR, the following errors can occur: foreshortening, which shows a shorter radiographic image than the patient's anatomy; elongation, in which the image appears longer than the actual morphology; overlapping with adjacent teeth; and cone cutting, such as leaving a blank space by the tube head of the dental X-ray machine (McDonald 1984;Kazzi et al. 2007;Mori et al. 2022).The position-indicating device (PID) consists of a part of the machine where the tube head extends into a cylindrical shape.Many errors occur during the central radiation positioning and vertical angulation of the PID; thus, the manipulation of the position by the tube head is important.Radiographic images acquired in the setting of such IOR errors do not accurately show the condition of the patient's oral cavity, which affects the quality of the oral examination and the treatment plan.Therefore, IOR must often be performed repeatedly until an accurate radiograph is obtained, but this could increase the amount of unnecessary radiation exposure to the patient (Vano and Fernandez Soto 2007).Thus, clinicians must learn the IOR method accurately and apply it in a clinical setting.
Knowledge about IOR can be achieved from the dental radiology curriculum, which provides information about physical radiation generation, biological protection of the human body against radiation, and radiographic imaging; additionally, IOR practice sessions required in the clinical field are conducted during this course (IADMFR Education Standards Committee 2007).The risk of accumulation of radiation exposure is constantly reiterated during the IOR sessions due to the emission of radiation from the radiation generator (Manousaridis et al. 2015;Firetto et al. 2019).In Korea, training is conducted using a dental X-ray manikin, which can show a precise structure during the practice process and reduce the risk of radiation exposure.However, the manikin is expensive, and its preparation is not feasible at many educational institutions.Additionally, learners participating in the practice must meet and maintain qualifications as frequent visitors to the radiation management area.Furthermore, the number of X-ray shots is limited or replaced by theoretical education owing to difficult conditions.The lack of opportunities for IOR practice weakens the competency, and learners experience difficulties in conducting IOR because they make mistakes during imaging (Kazzi et al. 2007).Therefore, new IOR educational media that allow learners to experience the situation without spatial restrictions are necessary.
Recently, there has been an increase in the use of virtual reality (VR) technology in the field of dentistry; this technology overcomes environmental constraints, has excellent educational effects, and comprises a clinical field centered on learners who can experience repeated education (Liebermann and Erdelt 2020;Nassar and Tekian 2020).VR allows a realistic experience in a virtual space created by computer simulation (Sutherland et al. 2019).Educational content using VR technology with a head-mounted display (HMD) promotes the user's immersion and understanding of phenomena and is closely related to the student's learning performance because it results in positive experiences and improved motivation (Stepan et al. 2017;Figueiredo et al. 2021).In particular, VR education using HMD promotes learning effects by interacting with students in the field of medicine and pharmacy in the form of a game (Abuhammad et al. 2021).For engineering students, virtual environments promote innovation and creativity, helping students engage and succeed in the educational environment (Katsioloudis et al. 2017).A virtual space provides higher visual realism by modeling objects or environments as three-dimensional (3D) objects or by recording a 360° space with a 360° camera (Huang et al. 2017;Pieri et al. 2022).VR images shot at 360° are simpler to produce than those made with 3D objects; the equipment and materials required for video production are cost-effective, and this technique is efficient for remembering the relative positions of the objects and work processes (Ventura et al. 2019).However, the disadvantage of a 360° video is that the user's viewpoint is fixed.Virtual environments using 3D objects have frequent user interaction effects, but a 360° video lacks interaction with the objects in the virtual environment.In contrast, the process of producing 3D objects is complicated and time-consuming, whereas 360° images can be easily acquired using only a 360° camera.Thus, it is easy to implement VR in various fields of dental education.Additionally, the immersive experience using a 360° VR video increases the students' learning participation and mastery and positively affects individual human factors such as perception and empathy (Pirker and Dengel 2021).Therefore, IOR education using 360° VR technology can provide a visual experience of the actual radiation management area, free from the risk of radiation exposure, and allows learners to practice IOR three-dimensionally and repeatedly.
This study aimed to supplement the environmental constraints of radiation exposure risk and limited practical opportunities in the BAT learning process during IOR by developing an educational medium called "Educational media for the BAT" using VR (EMBAT-VR) for IOR education.The medium can be used by the learner to indirectly experience a virtual environment using VR technology.The EMBAT-VR was developed and investigated through user experience; subsequently, the possibility of a new educational tool was suggested by comparing EMBAT-VR with the traditional learning medium (textbook) based on usability evaluations.Through EMBAT-VR, we intended to provide an educational medium that can help a learner experience the practice process and perform repeated learning indirectly.

Study design
EMBAT-VR was performed sequentially according to the stages of development, user experience investigation in a single group, and user evaluation based on comparisons between EMBAT-VR and traditional learning tools in the control and experimental groups.Figure 1 shows the sequential process for the study design.
For the production of the educational media, the learning process for the clinician's task, patient guidance, and detailed explanation (PID operation, patient management during the shooting process) in BAT were written in a step-by-step manner, in the form of a scenario.The clinician's task was the learning goal, patient guidance was a EMBAT-VR, the educational media for BAT using virtual reality conversation that required explanation to the patient, and detailed explanations represented the details of the imaging method in Table 1.Based on this scenario, a 360° video was produced by reproducing the roles of the operator and the patient.The video was built into an HMD, and the user experience was analyzed among students undergoing dental radiology who voluntarily participated and compared with the traditional learning methods.The traditional learning method involved using a textbook and a dental X-ray manikin (Dental radiography head phantom,41,Kyoto Kagaku Co.,Ltd.,Kyoto,JAPAN),as shown in Fig. 2.
Table 1 Simulation script of intraoral radiography focusing on the bisecting angle technique for 360° video recording in the maxillary and mandibular teeth ATL line of ala to tragus, BAT bisecting angle technique, C canine, CR central radiation of PID, CR central radiation of PID, DRF dental radiographic film, DXS digital X-ray sensor, I incisors, M molars, MnT mandibular teeth, MxT maxillary teeth, OTL line of oral angle to tragus, P premolars, PID position-indicating device, S sequence, VA vertical angle of PID.A1-A4 are the points where the ATL and L1-L4 lines intersect, respectively, and represent the central radiographic points of the maxillary molars, maxillary premolars, maxillary canines, and maxillary central incisors.O1-O4 are the points where the OTL and L1-L4 lines intersect, respectively, and indicate the central radiographic points of the mandibular molars, mandibular premolars, mandibular canines, and mandibular central incisors.L1 a line extending in the vertically inferior direction from the lateral canthus, L2 a line extending in the vertically inferior direction from the center of the pupil, L3 a vertical line at the lateral margin of ala nasi, L4 a line extending in the vertical direction from the nasal tip In the dental radiography room, one operator explained each BAT for 14 teeth, and a 360° panoramic image was recorded for one patient using a 360° camera.The captured image was output as a 360° VR image using editing software and was built on the HMD.For the user experience, participants (using the EMBAT-VR) were required to respond to a questionnaire on normal task action, exploration through browsing, and satisfaction.Factors such as "inconsistency in animation effect and 360° video", "controller operation error (start and stop)," and "discontinuity of operator sound (discontinuity)" were optimized when the HMD was operated by the participant.After the usability evaluation, third-year students enrolled in dental radiology courses were recruited to analyze the differences between the novel education medium and the traditional BAT learning methods.Those with poor general health, poor eye health, anemia, easy dizziness, and fear of using the HMD were not enrolled in the evaluation.This study was approved by the Institutional Review Board of our University (1041479-HR-202102-004).

Scenario script for reenactment of BAT
The behaviors, dialogues, and detailed explanations of one operator and patient were organized into a scenario board according to the BAT stage.A total of 14 localized areas, including the maxillary right molar, maxillary right premolar, maxillary right canine, maxillary incisor, maxillary left canine, maxillary left premolar, maxillary left molar, mandibular left molar, mandibular left premolar, mandibular left canine mandibular incisors, mandibular right canine, mandibular right premolars, and mandibular right molars, were used for dental imaging.Two professors with more than 10 years of dental radiology education and one clinical dental hygienist with more than 7 years of experience participated in the BAT scenario review and filming reenactment.The scenario divided the operator's actions into stages according to the filming process, and the operator's words to the patient were composed of dialogs.The detailed explanation included the location of the sensor in the oral cavity, vertical angle of the irradiation tube, incident point of the central radiation, and structure to be observed when checking the imaging results in Table 1. Figure 3 shows the site of central radiation for the BAT of the tube head as a PID in the dental X-ray machine.Four areas from each maxillary and mandibular tooth were photographed.The maxillary tooth is the point at which an imaginary line passing through the ala nasi and tragus meets an imaginary vertical line at the anatomical landmarks of the lateral canthus, pupil, ala nasi, and nasal tip.The mandibular teeth have the same anatomical landmarks, and instead of the imaginary line connecting the ala nasi and the tragus, it is the point where the line connecting the oral angle meets the tragus.

360° video recording and editing
A 360° camera was fixed to a stand to reenact the BAT process so that the operator and patient are observed in Fig. 4.
A GoPro Fusion (GoPro, San Francisco, USA) was used to obtain the 360° VR video recording; the captured video source was automatically stitched in the GoPro Fusion Studio App (GoPro, San Francisco, USA) and extracted as a 360° video.The extracted video was edited in detail through additional stitching, and the resolution and sound were adjusted.The sound of the operator's explanation was recorded at low volume, re-recorded according to the operator's mouth shape, and superimposed on the 360° video.The rendered video was edited using Premiere Pro (CC 2020, Adobe, San Jose, CA, USA) to match the scene transition and playback times.After Effects (CC 2020, Adobe) was used to add animation effects to the vertical angle of the PID of the dental X-ray machine and a detailed explanation in Fig. 5.The edited video was extracted as a final 360° VR video by encoding the project file into a video using Media Encoder (CC 2020, Adobe).This video was built on Oculus Quest 2 (Android version 10, Oculus, Los Angeles, CA, USA) using Unity Engine (version 2019.4,Unity Technologies, Copenhagen, Denmark).

Evaluation and statistical analysis
Data were analyzed using IBM SPSS Statistics 23 (IBM Co., Armonk, NY, USA).

User experience of EMBAT-VR: one group
The user experience was conducted to improve and supplement the operation of the HMD and output of the 360° VR image.Eighty-four students who took a dental imaging class at the Department of Dental Hygiene at a university in Gyeonggi-do were voluntarily recruited to evaluate the usability of EMBAT-VR.Personal information was deleted, and the students were classified into sequential numbers to prevent personal identification.No financial benefit was provided for study participation.None of the students were excluded from the eligibility review because of poor health at any stage.The purpose of this study and ethical protections were explained to the students using an online recruitment notice, and informed consent was obtained online.In particular, those who felt dizzy while using the HMD were informed that they could stop at any time and end the experiment.However, none of them discontinued the experiment.After using EMBAT-VR, the students filled out a questionnaire regarding the usability of EMBAT-VR as a BAT educational medium.The evaluation scales of Sutclife and Shin were modified, supplemented, and used in the study (Sutcliffe and Kaur 2000;Shin 2003).As shown in Table 2, The questionnaire was classified into three factors and consisted of ten normal task actions, five explorations through browsing, and six satisfactions (21 questions).Each question was marked with a level of agreement according to the 5-point Likert scale: 1 = strongly disagree, 2 = disagree, 3 = neither agree nor disagree, 4 = agree, and 5 = strongly agree.The Cronbach's alpha was calculated as 0.962.The mean and standard deviations of the results for this item were analyzed using descriptive statistics.

Usability evaluation between groups: textbook and EMBAT-VR
Third-year students attending a dental radiology class at the Department of Dental Hygiene, Namseoul University, were recruited to compare the traditional method using textbooks (control group) with the method using the HMD (experimental group).Two of 50 students opted out because they felt dizzy when using the HMD; thus, 48 students were enrolled in the experiment (n = 24 in each group).None of the 48 students demonstrated poor health or fear of HMD at the recruitment stage and during the experiment.Those in the control group learned about the BAT stage only through textbooks and performed simulations on a dental X-ray manikin, whereas those in the experimental group performed the simulations after learning through EMBAT-VR.Individual identifying information of the participants was removed, and only sequential numbers were used.Subsequently, two participants in the control group did not participate for personal reasons, thereby reducing the total number of participants to 46 (24 in the experimental group and in the control group).
The post-test results were compared using the post-test control group design.The 21-item questionnaire of Alfalah et al. ( 2019) was modified, and a 5-point Likert scale was applied.The questionnaire items were as follows: • Q1: Dental radiology educational media help in understanding and remembering dental radiography steps.• Q2: Using dental radiology educational media enhances visual learning.• Q3: Dental radiology educational media clearly show the relative positions of films and regions in the dental radiography process.• Q4: Learning dental radiography using dental radiology educational media is easier to understand.
Fig. 5 Editing process of a 360° video a The process of stitching two-dimensional images obtained by recording with a 360° camera.b A 360° video edited with animations regarding detailed explanation (white dotted box) for intraoral radiography by the bisecting angle technique • Q5: Dental radiology educational media provide an opportunity to learn the steps of dental radiography repeatedly.• Q6: I can use the dental radiology educational media whenever I need them.• Q7: I think dental radiology educational media can be considered a good educational tool.• Q8: I can use dental radiology educational media flexibly (without considering time or space) for learning dental radiography.• Q9: I can view the dental radiography process from various perspectives through the dental radiology educational media.• Q10: I can quickly understand the stages of dental radiography through the dental radiology educational media.• Q11: I can easily find dental radiography steps through the dental radiology educational media.• Q12: Dental radiology educational media can save the time needed to learn basic theory.• Q13: I think that dental radiology educational media will help in building basic theories before going to clinical practice.• Q14: Dental radiology educational media contain a lot of content on the theory of dental radiography.
• Q15: Dental radiology educational media reinforces my learning goals.• Q16: I enjoy learning using dental radiology educational media.• Q17: I can easily interact with others using a dental radiology educational medium.• Q18: Through the dental radiology educational media, I can clearly find and learn the dental radiography equipment and imaging steps required for dental radiography.• Q19: Dental radiology educational media displays essential information for students.• Q20: I can approach the dental radiography process from different angles through the dental radiology educational medium.• Q21: I can have a three-dimensional approach to dental radiography using a dental radiology educational medium.
The Mann-Whitney U test was used to compare differences between the control and experimental groups.After all the experiments were completed, the students from both groups were allowed to use EMBAT-VR.

Results of EMBAT-VR execution
Both the operator and patient could be observed in the 360° video when EMBAT-VR was executed on the HMD with the controller in Fig. 6.The BAT process for the selected tooth could be observed after the user selected one of the 14 teeth.Figure 7 shows the user's view from the stage of the BAT on a 360° video by the HMD.In the 360° VR environment, the BAT stage appeared on top of the patient's head in Fig. 7a; and the position of the dental X-ray sensor, position of the central radiation of the PID, and vertical angle could be checked along with the operator's dialog in Fig. 7b.The information regarding the imaging is shown at the bottom in Fig. 7c.The dental radiograph and detailed explanations to be taken after the shooting were confirmed in Fig. 7d.Additionally, Fig. 7b shows that the tooth names were observed according to the Federation Dentaire International system.In other words, the operator could adjust the PID's position according to the shooting site and observe a 360° video of the interaction between the operator and the patient according to the scenario stage.
Figures 8 and 9 detail the manipulation at the location of PID, focusing on the vertical and central radiation on the HMD in the maxillary teeth.In Fig. 8, the vertical angles of the maxillary molars, maxillary premolars, maxillary canines, and maxillary incisors of the tube head were 20°, 30°, 45°, and 40°, respectively.
After adjusting the position of the PID so that the PID and digital X-ray sensor were parallel, the minus sign indicated that the PID near the patient's face was moved upward in the horizontal plane.In particular, after the 360°  simulation of the BAT, the intraoral radiographic images obtained from the actual clinical trials appeared at the top of the user's screen, and the user could check the different clinical results corresponding to 14 sites.After confirming the intraoral radiographic image, the operator could also check the image that guides the patient to the treatment room or waiting room after removing the lead apron in Fig. 7d.Additionally, after obtaining the dental radiograph of the selected tooth part, the student could select another part of the tooth using the HMD's controller or start over the process.

User experience of EMBAT-VR
In Table 2, The means and standard deviations for the three factors evaluated were as follows: normal task action, 3.78 ± 0.70; exploration through browsing, 3.88 ± 0.76; and satisfaction; 4.01 ± 0.71.In particular, satisfaction was evaluated as a mean score of 4 or higher on a 5-point Likert scale.Items with scores higher than the mean in normal task action factors were 3, 4, 5, 6, and 10; those for exploration through browsing were 11, 13, and 15; and those for satisfaction were 16, 19, and 20.In contrast, the scores for items 1, 2, 7, 8, and 9 for the normal task action; 12 and 14 for exploration through browsing; and 17, 19, and 21 for satisfaction were lower than the mean value.Items 7, 14, and 17 had the lowest scores at 3.60 ± 1.10, 3.85 ± 0.83, and 3.91 ± 0.87, respectively.

Comparison between traditional learning media and EMBAT-VR
The mean values in the experimental and control groups were 4.16 ± 0.64 and 2.69 ± 0.54, respectively, and the medians were 4.17 and 2.80, respectively; the mean and median of the experimental group were higher than those in the control group.As shown in Table 3, the U value was 23.50 and Z value was − 5.293 (p < 0.001); the effect size (r) was 0.77.The mean score for all the questionnaire items was higher in the experimental group than in the control group in Fig. 10.

Discussion
Dental radiography with image defects caused by missing mesial or distal structures of the teeth, overlapping contact parts, missing apices, and cone cuts make it difficult to determine the patient's condition accurately.This increases the number of times the radiograph is repeated and a consequent increase in radiation dose (Senior et al. 2018).Prospective clinicians need to repeatedly learn and master dental radiography techniques to reduce imaging failures in the preclinical phase (Vandenberghe et al. 2010).However, repeated dental radiography practice for learning increases the risk of cumulative radiation exposure among instructors and learners.Thus, limited or insufficient training opportunities can weaken clinical practice competency.It is difficult to overcome these limitations with IOR learning based on existing textbooks; hence, a new educational medium is required to expand the indirect experience and increase the actual shooting efficiency.
VR technology has been used in practical education in the field of dentistry, and many researchers have verified its effectiveness as a learning medium as a learning tool for 3D  practical education (Murbay et al. 2020;Su Yin et al. 2021;Zafar et al. 2021).In particular, VR technology maximizes the user's immersion and 3D effect through information provided in a virtual environment that can be observed in a 360° angle (Vertemati et al. 2019;Kurul et al. 2020).Additionally, education using VR technology has the advantage of encouraging learners to participate in learning actively, thereby positively affecting the achievement of educational goals and overcoming spatial limitations (Morales-Vadillo et al. 2019).
EMBAT-VR allows a 360° VR image to be played based on the part of the tooth selected by the learner, and the filming process is reproduced through the BAT.Fourteen dental radiographs were evaluated for 14 areas on the teeth; the positions of the digital X-ray sensor and PID and the 14 actual intraoral radiographs were observed according to each tooth area.The students could check the detailed steps and cautions at the bottom of the patient's head observed through the HMD, and they experienced the 360° environment in a 3D view.Additionally, various cases were observed using actual clinical dental radiographs of root canal-treated teeth, restored teeth, and implants.The students were able to confirm the position of the digital X-ray sensor, the vertical angle, and the central radiation of PID by the BAT for each tooth through the additionally inserted 2D detail in the 360° VR video and via repeated learning.It is difficult to shoot directly from the operator's point of view because EMBAT-VR uses 360° images.However, the advantage of this system is that the steps of the standardized imaging method can be shown as a whole and can be repeatedly confirmed; additionally, an indirect experience can be achieved within the space of a 3D dental radiology room.
The results of all questionnaire items were higher than normal in the usability evaluation of EMBAT-VR.There were no negative responses in the mean scores for EMBAT-VR; therefore, this medium was used for evaluations between groups.Hanson et al. reported that satisfaction with VR use improves learning and understanding (Hanson et al. 2020).As shown in Table 2, satisfaction had a descriptively higher mean score than normal task action and exploration through browsing, thus indicating that EMBAT-VR enhances learning and understanding compared to traditional educational media.However, these claims require additional testing.In the user experience, the opinions individually presented by the participants (animation effects, operation errors with controls, inconsistency of operator's voice) were corrected and optimized.Nevertheless, some participants expressed difficulties using the controller.Users experiencing the HMD and controller for the first time are unfamiliar with the operation.Thus, a simulation process that can help a user gain experience is required.
A statistically significant difference was observed between the control group, who used textbooks in the dental radiology class, and the experimental group, who used EMBAT-VR in Table 3. EMBAT-VR clearly showed the relative position of the digital X-ray sensor and PID and could be viewed from various angles.EMBAT-VR scored higher than traditional learning tools for all questions based on each survey item.In Fig. 10, EMBAT-VR scored higher on average than traditional learning tools for all questions based on each survey item.Differences were found in understanding, memory, relative positioning, repetitive learning, flexibility, provision of various viewpoints, time-saving, reinforcement of basic theories, reinforcement of learning goals, and interaction.These findings indicate that EMBAT-VR can be used as a new education tool because it promotes subjective learning rather than learning via a two-dimensional textbook.The ability to guide the patient safely and take the shot accurately in the dental radiology room is vital.In particular, the 360° video and HMD give the learners an immersive feeling in the dental radiology room.The effect of education on immersion in a 360° video and the VR environment has been proven in several studies (Chang et al. 2022;Fahim et al. 2022;Moussa et al. 2022;Tak et al. 2023).Additionally, EMBAT-VR can overcome the physical limitations of learning conditions through the VR environment.Thus.EMBAT-VR provides an indirect experience using VR technology to solve problems such as the absence of an actual shooting opportunity or the limited number of shots because of the risk of radiation exposure.Additionally, EMBAT-VR can be used in the prelearning stage because learning through existing textbooks cannot solve real problems.In particular, VR technology using 360° images of IOR by BAT is faster and easier to produce than the existing 3D object creation.Repeated learning through indirect experience helps learners and can be applied to many clinical skills-related subjects.Moreover, this study used a post-test control group design, which was applied to students who were enrolled in a dental radiology class; the results were compared between the experimental and control groups.Although it was confirmed that EMBAT-VR is a good learning tool compared to existing textbooks, additional experiments are needed to prove the causal relationship between EMBAT-VR and the actual shooting.It is also necessary to estimate the population using parametric statistics by increasing the number of participants.Additional studies on the effect of the learning method using EMBAT-VR on dental X-ray manikin and BAT in patients are needed.In the future, a VR application that can perform the function of a simulator by directly manipulating the PID using a 3D object must be produced.

Conclusion
In this study, we developed and evaluated EMBAT-VR using VR technology so that the issues related to dental radiography education, such as the risk of radiation exposure, limitations in practice opportunity, environmental constraints, and repeatability of the experiment could be overcome.Additionally, we reviewed the potential of this new educational medium by comparing the traditional learning method of using textbooks with the EMBAT-VR learning method.EMBAT-VR can provide a user experience through the HMD and a controller.The students in the experimental group learned the IOR process through indirect experience.The satisfaction with EMBAT-VR was high, and this technique scored high in the usability evaluation.These findings indicate the advantages of using EMBAT-VR rather than textbooks in BAT.However, our study did not reveal the causal relationship between EMBAT-VR and the actual shooting.Additional research on the effectiveness of dental X-ray manikins and actual human subjects is warranted.Studies with larger sample sizes are required to determine these causal relationships.Additionally, it is necessary to produce and evaluate VR applications that can perform simulation functions by directly manipulating the PID.

Fig. 1
Fig. 1 Study design and workflow for the development and evaluation of intraoral radiography (IOR), focusing on the bisecting angle technique (BAT) based on virtual reality (VR).EMBAT-VR, the educational media for BAT using virtual reality . I will check the patient's name Confirm the patient's name and the tooth where BAT will be performed 2 Guide to the shooting process Please let me know if you feel uncomfortable while shooting The area to be radiographed is the MxT (right and left M, PM, C, and I) or MnT (right and left M, PM, C, and I) 3 Removal of accessories and removable partial or full denture Please remove accessories on the face and removable partial or full denture in the mouth Guidance on where to store patient's belongings 4 Wear lead apron Patients should wear a lead apron to block radiation exposure to unnecessary areas.I will help you put it on 5 Adjust the patient's head position MxT: Please look straight ahead and put the tip of your chin toward your neck MnT: Please look straight ahead and lift the tip of your chin upward Keep the midsagittal and transverse planes of the patient's head perpendicular.MxT: parallel to ATL and the horizontal plane MnT: parallel to OTL and the horizontal plane 6 DXS positioning and fixing Positioning the DXS in your mouth can be a little uncomfortable If you open your mouth, we will position the DXS Please, hold the DXS with your finger and stay still M: Distal half of the second premolar 3-mm extension from the cusp and including the crown and root PM: Distal half of the canine, including the crown and root of the first premolar I: With the crown and root of the canine in the center of the DXS C: Including the left and right incisors 7 Adjust the position of the PID Please stay in your position. of the dental X-ray machine outside the X-ray room 9 Removal of DXS Please take your hand off the DXS.I will check the DRF Remove the patient's sensor out of the oral cavity 10 Confirmation of DRF Please wait Crown, root, alveolar crest, interproximal surface of teeth, and periodontal region 11 Removal of the lead apron and check the belongings I have checked the DRF Please take off your lead apron and bring your belongings Checking the patient's belongings in the X-ray room 12 Guide to the waiting room I will guide you to the waiting room

Fig. 2
Fig.2Image shows a dental X-ray manikin and a dental X-ray machine.Simulation was performed on a dental X-ray manikin after learning from a textbook

Fig. 4
Fig. 4 Reenactment of the bisecting angle technique recorded with a 360° camera.The asterisk indicates a 360° camera.Abbreviations in black letters indicate the components of the dental X-ray machines.TH, tube head; PID, position-indicating device of the dental X-ray machine.Abbreviations in white indicate the operator, patient, and lead apron of the patient.OP, operator; P, patient; LA, lead apron

Fig. 6
Fig. 6 Using a head-mounted display (HMD) with controller (C) for learning of bisecting angle technique

Fig. 7
Fig. 7 Stage of the intraoral radiography by the bisecting angle technique on a 360° video using the head mounted display.a Patient identification.b Position of the digital X-ray sensor.c Position of the position-indicating device in the dental X-ray machine.d Observation of dental radiograph.The meanings of the Korean text captured as 360° images to the right of a1, a2, b1-b3, c1-c3, d1, and d2 are as follows: a1, Check the patient's name; a2, Hello, sir.I will check

Fig. 8
Fig. 8 Photographs showing the location of the positionindicating device (PID) in the dental X-ray machine focusing on the vertical and central radiation on the head mounted display in maxillary teeth.The angle displayed on the left side of all photographs denotes the central radiation of the PID and indicates that the PID operates in the inferior direction on the horizontal plane.Relatively, the tube head (TH) moves upward.a: maxillary molars, b: maxillary premolars, c: maxillary canine, and d: right and left maxillary incisors

Fig. 10
Fig. 10 Bar chart showing differences in the responses to questions between the experimental and control groups.The control group used textbooks, and the experimental group used virtual reality media

Table 2
Usability evaluation of virtual reality education media for intraoral radiography by the bisecting angle technique (n = 84) M mean, N number of participants, SD standard deviation

Table 3
Comparison of conventional educational tools (textbook) and the educational tool by the bisecting angle technique using virtual reality E experimental group: participants used a head-mounted display for dental radiography, C control group: participants used a textbook as the conventional method in dental radiography, n number of participants, M mean, SD standard deviation, Md median