1. Introduction
nxiety is an emotional response and unpleasant feeling [1], i.e., commonly observed in patients and dental centers [2]. This phenomenon is especially experienced in individuals who undergo special dental interventions for the first time, like surgery. Besides, it is considered a barrier to interventions, care, and management of patients in dental departments [1, 3]. Surgical interventions in dentistry, like wisdom tooth surgery, are associated with more anxiety due to the longer duration of the operation, bleeding, and more postoperative pain. Some studies have cited it among the essential reasons for not seeking, following up, and receiving dental care. Anxiety is sometimes accompanied by fear and panic; with the occurrence of coping behaviors in patients, it complicates providing the desired services by the dentist [4]. In general, dental anxiety due to its adverse effect on oral health and quality of life is a public concern in different societies [5]. It is the main cause of changes in the hemodynamic status of patients following the secretion of catecholamines [6, 7]. Studies reported significant changes and differences in some indicators of cardiovascular and respiratory functions in patients during different stages before anesthesia and dental intervention [8]. Therefore, it is necessary to study and pay attention to anxiety and its associated complications in patients undergoing dental surgery. Such measures help to diagnose and prevent emergencies, such as shock, and even coma and death [9].
Dental anxiety can be managed by different approaches, such as pharmacological, psychological, or a combination of both [10] depending on its level, patient characteristics, and clinical condition [10]; however, pharmacological methods may be associated with limitations and adverse effects. A proposed non-pharmacological method, i.e., currently used in various fields, including dentistry, and especially for patients who do not consume anti-anxiety medications due to their adverse effects, is using Virtual Reality (VR) [11, 12]. VR is a relatively new term in the field of health, i.e., in recent years and its application is developing in medical sciences. With this new technology and in a graphical environment, the user feels a physical presence in the real world. Accordingly, they can experience constructive interaction by immersing themselves in a multidimensional environment [13 ,14, 15, 16]. Besides, by creating peace, distraction, and the lack of the patient’s focus on dental interventions, VR reduces complications and increases patient cooperation and quality of dental care [17]. The positive effects of this method have been reported in managing pain and anxiety in numerous conditions, especially in children [18].
However, studies revealed that the prevalence and level of anxiety in dental clients vary in different communities as well as age and gender groups. The results of a systematic review indicated that the rate of anxiety in women, single individuals, and lower age groups was higher than that in other populations [19]. The prevalence of this phenomenon in a cross-sectional study in Iran was reported to be 33.6% in the age group of 15-75 years [20]. In another study, the same prevalence rate was measured as 5%-61% in children [5] and 1%-52% in adults [21]. Furthermore, individuals experience more severe anxiety before dental procedures than in other stages [19]. Accordingly, implementing low-cost methods with limited adverse effects, like VR seems essential in managing anxiety among patients referring to dentistry clinics. 
According to a systematic review and meta-analysis data (2020), studies on the effect of using VR technology on anxiety are more focused on children; therefore, the effect of this technology on anxiety caused by dental procedures in adults remains unaddressed. Researchers emphasize the need for further studies in different groups of patients in dental centers [22]. Other similar studies have reported the limitations and inadequacies of studies on the effect of VR on patients’ anxiety, especially dental interventions, like wisdom tooth surgery, i.e., associated with pain and require anesthesia [23, 24]. Therefore, there is a research gap in this field; current knowledge is inadequate to make a decision or suggest the use of VR.
Due to the high prevalence and adverse effects of anxiety on patients and treatment teams as well as the positive effects of VR as a new, accessible, and safe technology in reducing anxiety and pain in children and adults [18], the present study aimed to determine the impact of VR on preoperative anxiety in the candidates of wisdom tooth surgery.
2. Materials and Methods
This randomized clinical trial (Code: IRCT20181023041425N1) was performed in the Department of Oral and Maxillofacial Surgery at the School of Dentistry of Mashhad University of Medical Sciences in Mashhad City, Iran, in 2019-2020. The study sample consisted of 60 patients who were candidates for the incubation of third molar teeth that first. Respecting the inclusion criteria, they were selected from all eligible clients by a convenience and purposive method. Then, the study subjects were randomly assigned to two equal test and control groups.
The sample size was obtained using the formula for comparing the mean scores of anxiety and considering a 95% confidence interval and 80% test power. In total, about 21 subjects were estimated per study group. Considering the odds of sample dropout, the conditions for establishing the central limit theorem, and increasing the odds of following the data from the normal distribution to use parametric tests, finally, 30 subjects were considered as a sample per group (N=60). The inclusion criteria of the study were willingness to participate in the study and providing informed consent forms, no history of mental or cardiovascular and respiratory conditions based on patients’ medical history, questioning them and considering dental records, the age range of 18-60 years, no use of drugs affecting the mental health, having the necessary vision and hearing and the ability to read and write in Persian. The exclusion criteria of the study also included the following: cancellation and unwillingness to continue participation in each stage of the study at the discretion of the patient and the occurrence of any special medical conditions, i.e., inconsistent with continued participation in the study.
The research tools were as follows: demographic characteristics questionnaire and general information including questions about age, gender, marital status, educational level, employment status, smoking, companionship, and the use of sedatives. This questionnaire was prepared after studying reliable sources and using the opinions of experts; accordingly, the necessary corrections were made to it. After obtaining informed consent forms from all study patients, this tool was completed by them. We also employed the Spielberger State-Trait Anxiety Inventory (STAI), containing 20 four-answer questions, i.e., completed by the explored patients. The test options included very low, low, high, and very high scales. Each phrase in this test is set to positive and negative answers. The interpretation and classification of the questionnaire consist of scoring positive questions (1, 2, 5, 8, 10, 11, 15, 16, 19, 20) as very low (4), low (3), high (2), very high (1) as well as negative questions (3, 4, 6, 7, 9, 12, 13, 14, 17, 18), i.e., scored in reverse: very low (1), low (2), high (3), very high (4). Therefore, the total score of this questionnaire ranges between 20 and 80. The scores are divided between mild anxiety 20-31, moderate anxiety 32-63, and severe anxiety 64-80. The validity and reliability of this questionnaire were assessed and the tool was validated among 600 patients in Mashhad in 1983 by Spielberger and in Iran by Behrouz Mehram in 1994 [25]; its reliability was also confirmed by Nazemian in 2008 [26].
In the experimental group, after completing a questionnaire related to the demographic characteristics and measuring anxiety by patients, the experimental group underwent intervention, i.e., in VR. The equipment used for the VR technology was a VR device and headset (Remax-RT-V03 audio-video glasses with internal memory) that allowed the patient to wait for 12 minutes before surgery; optimized with high-quality sounds and pleasant nature scenes. Accordingly, the conditions were provided for them to experience more peace of mind by distracting and immersing themselves in a pleasant environment, instead of focusing on the surgical process. The control group also waited without special intervention and according to the usual conditions and concurrently underwent surgery according to the call.
To assess the intervention effects on anxiety levels in the patients, the anxiety questionnaire was re-completed by the intervention and control groups before entering the operating room. The waiting time for patients in both groups to enter the operating room was 15 minutes. To blind and prevent bias, the analyst was blind to the test and control groups.
The obtained data were analyzed by SPSS. For this purpose, descriptive statistics were used by determining the indices of central tendency and dispersion for quantitative variables as well as the frequency for qualitative variables. The normality of the variables was evaluated by the Kolmogorov-Smirnov test. Moreover, the Chi-squared test and Independent Samples t-test were used to compare quantitative mean scores between the study groups. Besides, Paired Samples t-test was used to compare these values ​​before and after the intervention per group. P≤0.05 was considered significant.
3. Results
In this study, 60 patients who were candidates for dental surgery (n=30/group), including 28(46.7%) men and 32(53.3%) women participated. The age range of patients was 18-37 years with a Mean±SD of 26.5±4.9 years. The research groups were homogeneous concerning demographic characteristics, such as gender, marital status, educational level, employment status, smoking, and sedatives use (Table 1).


As per Table 2, the Independent Samples t-test data indicated a significant difference between the control and test groups in the mean anxiety scores of patients before and after the intervention (P<0.05).


Additionally, based on the results of Analysis of Covariance (ANCOVA) (Table 3), the difference in anxiety after the intervention was not a function of possible interfering factors between the study groups and has significantly differed respecting VR in patients’ anxiety (P<0.001).


Considering the effect size (0.44), using VR explained 44% of the variance in the level of anxiety in the intervention group.
Based on the results of Paired Samples t-test and Independent Samples t-test (Table 2), the mean score of anxiety in the control group was not different in the pre-test and post-test phases (P>0.05); however, in the experimental group, the difference in the mean score of anxiety before and after the intervention was statistically significant (P<0.05). Moreover, the difference between the pre-test, post-test values ​​of anxiety was significantly different (P<0.001). However, according to Table 4, the difference between the anxiety levels of the research groups before and after the intervention was not statistically significant.


In other words, comparing the level of anxiety in mild, moderate, and severe quality scales revealed that the study groups were not significantly different at pre-test and post-test concerning anxiety (P>0.05).
4. Discussion
 This study determined the effects of VR on preoperative anxiety in patients candidates for dental surgery. According to the present study findings, the mean score of anxiety in the experimental group was significantly reduced, compared to the control group. Therefore, VR positively influenced controlling anxiety induced by oral surgery in the examined patients. This finding is clinically important as a non-invasive and low-risk method and can increase patients’ comfort, cooperation, and quality of dental services. The level of anxiety is influenced by factors, such as age, gender, education, etc.; studies reported a relationship between some demographic characteristics and anxiety experienced due to invasive dental procedures [19]. Thus, the homogeneity of these features was assessed in the intervention and control groups. The related results indicated no significant difference between the study groups in this regard.
Some studies indicated that at younger age and youth, single, and female individuals experience higher levels of anxiety, i.e., related to patients’ previous dental experiences [10, 27, 28]. However, in the present study, the age range and sample size were limited. Accordingly, these differences cannot be examined. However, more attention to the therapist, the need for companionship for psychological support, the use of clinical methods, like VR in reducing anxiety in patients who are candidates for wisdom surgery who are usually not old (in our study: 26.5±4.9 years) is emphasized. 
Various studies, in line with the present study, reported the positive effect of VR on patients’ anxiety. For example, a study conducted by Gunner et al. in 2018 in France used VR to reduce preoperative anxiety in patients with outpatient maxillofacial surgery; the intervention lasted for 5 minutes, using nature images in VR technology. They concluded that using VR biopsychologically and significantly reduced preoperative anxiety in the study units [29].
Arne et al., in 2017, investigated the effects of VR on managing children’s pain and anxiety. Accordingly, it was found that using VR images was much more effective than the current standard care in reducing patients’ pain and anxiety [30].
Asl Aminabadi et al. (2012) in Tabriz evaluated the effects of VR through distraction on anxiety and pain in 4-6-year-old children during dental procedures. This investigation was randomly performed on 120 children. The relevant results indicated that using VR distraction effectively reduced pain and anxiety in children during routine treatment. The current study data were consistent with theirs [31]. Numerous other studies, despite the differences in the content of VR, the technology used, the duration and time of its presentation in the dental surgery process, have suggested similar results in line with those of the present study regarding the positive effects of VR on anxiety [2, 32, 33, 34, 35].
VR, by diverting into a multidimensional and pleasant environment causes distraction [34, 35] and changes the activity of the sympathetic and parasympathetic systems [23]; thus, it improves anxiety and physiological parameters. This finding is clinically essential and increases patients’ comfort, cooperation, and quality of dental services. One of the main reasons for the positive impact of this technology is the new and exciting nature of visual and auditory and simulation. Recognizing that this is a virtual environment, the patient attempts to adapt to it and establish a constructive interaction by overcoming it, overcoming the limitations of the real world, and revealing new horizons. The interesting and attractive graphic and interactive features of this technology lead to the arousal and excitement of patients, by creating the right motivation; it uses the individual’s abilities in a challenging format for a while. Therefore, along with relaxation techniques, it can play an essential role in improving anxiety symptoms [17]. However, some studies have achieved different results and the lack of effect of VR on anxiety [36, 37].
Another study explored the effects of non-pharmacological methods on hemodynamic changes due to anxiety in patients undergoing third molar surgery. In this study, 22 patients received verbal explanations and 18 video demonstrations, including information about the surgical process. The obtained results demonstrated that the heart rate significantly decreased due to reduced anxiety in different stages of surgery in the video display group [38], i.e., consistent with the present study findings. Another study was performed for the same purpose and in the same way; despite the increase in oxygen saturation in the video display group, the changes in other hemodynamic indicators due to the level of anxiety were not different between the two groups [39]. Such data discrepancy could be attributed to the content of the visual and auditory display, the applied technology, the observation of the surgical process, and the awareness of it which did not improve the indicators. Accordingly, in both used technologies, the distraction of thought occurs; however, the distraction of thought and relaxation by observing pleasant scenes of nature with VR technology and three-dimensional space in our study caused an effective reduction of patients’ anxiety.
A systematic review and meta-analysis in April 2020 signified that VR was effective in reducing dental anxiety; however, this effect was not reported to be statistically significant in children. It was also found that there exist few studies in adults and further research is required [22].
However, despite the positive effect of using VR in the present study and the report of other researchers on the different effects of this method in different populations, conducting this study in one center and only on patients who were candidates for wisdom tooth surgery and in the age range was a limitation. Additional studies can answer some of the remaining questions in this regard. However, the results can be generalized to patients and similar groups and candidates for wisdom surgery. Therefore, more attention to the therapist to reduce and treat psychological problems (anxiety) and the need to use clinical methods, like VR for patients candidates for oral surgery (wisdom teeth) who are usually not old, is suggested and emphasized.
5. Conclusion
The present study results, in line with the findings of some other studies, supported the positive effect of using VR in reducing anxiety. Therefore, while proposing the use of this technology similar to what was designed and implemented in our research, it is recommended to conduct additional studies on different groups of patients, different tools, and technologies in presenting VR, time, and duration of its use.

Ethical Considerations
Compliance with ethical guidelines
The Ethics Committee approved the study of Mashhad University of Medical Sciences (Code: IR.MUMS.DENTISTRY.REC.1398.020). While obtaining informed consent from patients, the general code of ethics and clinical trial approved by the Ministry of Health and Medical Education were observed.

Funding
The Vice-Chancellor has provided the financial resources of this project for Research and Technology of Mashhad University of Medical Sciences. The results described in this article are taken from Mina Mohammadpour, a dental student at Mashhad University of Medical Sciences.

Authors' contributions
Writing – original draft, writing – review, editing and methodology: All authors; Conceptualization: Mina Mohammadpour; Final approval: Majid Hosseini Abrishami, Mina Mohammadpour; Data collection: Majid Hosseini Abrishami, Sahand Samiierad, Mina Mohammadpour.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The researchers thank all the patients who participated in this study, the Staff of the Surgery Department, and the Educational and Research Departments of Mashhad Dental School.



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