Keywords

1 Introduction

Dental anxiety is one of the most important factors influencing the patient’s dental experience. Because of the phobia of pain and dental treatment equipment such as dental drills, fear of unknown things, or terrible dental treatment experience in childhood, some people are caught in a negative emotion of dental anxiety. Dental anxiety makes patients unable to cooperate with dentists. Delay treatment or even refuse to see a doctor. Statistically, dental anxiety afflicts a significant proportion as high as 50%, with 6%–20% of patients who have severe dental anxiety [1]. Therefore, reliable and timely management of the negative emotions is necessary to improve oral health and life quality for the people who are experiencing dental anxiety.

2 Literature Review

2.1 Dental Anxiety

A growing number of scholars and dentists are aware of the adverse effects of dental anxiety on oral health, and have carried out a series of researches on dental anxiety. They explore the means of assessing dental anxiety and the factors affecting dental anxiety, with the intention of finding ways to relieve dental anxiety. Those effective ways can be applied in clinical practice. Psychological intervention and drug treatment have proven to be effective in alleviating dental anxiety at present. Psychological intervention such as cognitive behavioral therapy, exposure therapy, music therapy, aromatherapy, relaxation and distraction have been increasingly used in the practice of oral treatment with the advantage of no side effect.

Here comes the overview of some psychological intervention methods and their advantages and disadvantages (Table 1).

Table 1. Overview of some psychological intervention methods.
Full size table

2.2 Cognitive Behavioral Therapy

Cognitive behavioral therapy (CBT) is widely used in the practice of dental anxiety through cognitive reorganization, knowledge education, Psychological counseling and relaxation. Mihaela (2014) examined the effectiveness of cognitive behavioral therapy in reducing dental anxiety. Four sessions of cognitive restructuring technique were used in order to reduce the dental anxiety level. Compared with the control group without any intervention, substantial reductions of dental trait anxiety could be obtained through sessions of cognitive restructuring [2]. Tellez (2015) developed a cognitive-behavioral protocol based on psychoeducation, exposure to feared dental procedures, and cognitive restructuring. This computer based tool was confirmed to be efficacious in reducing dental anxiety [5].

However, as a psychological intervention, limitations of cognitive behavioral therapy are also significant. This method requires full follow-up by researchers, dentists or professional psychologists. Moreover, CBT personnel need to undergo rigorous training, which requires a lot of human resources and needs a fixed training location.

Therefore, more auxiliary therapies such as reading therapy and computerized cognitive behavior therapy are developed based on modern technology and resources.

Computerized cognitive behavior therapy can effectively reduce the occupation of professional resources and suggest to be efficacious in alleviating dental anxiety. In recent years, scholars combine cognitive behavior theory with design science furtherly. The interdisciplinary research bridges the deficiencies of traditional cognitive behavior therapy.

2.3 Virtual Reality

With the real-time performance feedback, self-guided exploration and independent practice, low-cost environment that can be duplicated and distributed, virtual reality enables patients to achieve remote self-training in the field of medical, which greatly saves resources. In the field of medical treatment, virtual reality has been widely used in psychotherapy, cognitive rehabilitation, mental disorders and auxiliary training [14,15,16,17]. It also has a good effect on relieving anxiety caused by fear. For example, combining exposure therapy and virtual reality can effectively relieve acrophobia, social phobia and preoperative anxiety [18, 19]. On the other hand, it is also an effective way to provide a relaxing environment in virtual reality to help patients escape from the horrible reality [11].

To this end, this study firstly summarized the existing literature, analyzed the characteristics of the people who are experiencing dental anxiety. Then the whole study developed a relief tool for dental anxiety in virtual reality environment based on serious game and cognitive behavioral therapy, and explored a new type of computerized cognitive behavior therapy framework based on virtual reality. The purpose is to help patients with evasion and fear of oral treatment to relieve their negative emotions and improve their treatment experience (Table 2).

Table 2. Literature review about dental anxiety.
Full size table

3 Materials and Methods

3.1 System Design

Before completing the specific design, the research investigated the reasons of dental anxiety, and determined the horror gradient of the dental clinic scene. It is found that negative associations with dental treatment, insufficient awareness of dental diseases, fear of unknown treatments and barriers to communicate with dentists become the main causes of anxiety. The result will guide subsequent designs.

Four virtual dental treatment scenarios with increasing horror levels are developed according to the research:

  1. 1)

    A dental environment with dental instruments and a virtual dentist surrounding the participant.

  2. 2)

    The virtual dentist with a dental mirror in his hand moves towards to the participant, just like doing an oral examination.

  3. 3)

    The virtual dentist with a dental syringe in his hand moves towards to the participant, just like doing an oral therapy.

  4. 4)

    The virtual dentist with a dental drill in his hand moves towards to the participant, just like doing an oral therapy.

The experiment was performed in a quiet room of 5 m * 3 m. The seat simulates the height and angle of a dental seat. The VR helmet uses HTC VIVE, including a helmet, two handles and two lighthouses. The program is developed by Unity 2018.3.10 and runs in SteamVR.

Experimental Group (VR-CBT).

The VR-CBT group will present a narrative and easy-to-understand interpretation of the dentist’s upcoming treatment before each scene. Participants can autonomously control the course of treatment according to their own adaptation.

Control Group (VR).

The VR group will only be presented in the same 4 virtual scenes as the VR-CBT group (Figs. 1 and 2).

Fig. 1.
figure 1

The virtual reality dental anxiety mitigation product design. (Left: the scene design; Right: the scene from the patient’s perspective.)

Full size image
Fig. 2.
figure 2

The introduction to the upcoming virtual treatment in the form of a pop-up window in the experimental group.

Full size image

3.2 Participants

24 participants who were about to visit a dentist were recruited in order to verify the effectiveness of computerized cognitive-behavioral therapy in virtual reality. All participants were asked to sign a consent and fill out a subjective basic information questionnaire before the experiment. The inclusion criteria are as follow: 1) Participants with a MDAS score ≥15; 2) Participants who don’t have hearing or visual impairments, known balance disorders, post-traumatic stress disorder, developmental or intellectual disability. 3) Participants have never received any cognitive behavioral therapy treatment for their dental anxiety in the past.

3.3 Procedure

A total of 24 samples were tested in the single-blind experiment, with 12 participants in the experimental group and 12 participants in the control group. First of all, participants should filling the modified dental anxiety scale. Then they were asked to wear the physiological testing equipment in order to get their galvanic skin response and heart rate. After that, a video about tooth extraction was provided to determine their baseline of dental anxiety. Participants both in the experimental group and control group then wore the VR helmet for the text. At the same time, quantitative intervention results were obtained during the text.

After the experiment, participants could remove the physiological testing equipment and the VR helmet, then filled out the modified dental anxiety scale again and filled out the user experience questionnaire.

3.4 Measurements

Modified Dental Anxiety Scale (MDAS).

The modified dental anxiety scale is a common measure of dental anxiety which is effective in assessing dental anxiety in an internationally diverse sample. The scale consists of five indicators: 1) If you went to your Dentist for treatment tomorrow, how would you feel? 2) If you were sitting in the waiting room (waiting for treatment), how would you feel? 3) If you were about to have a tooth drilled, how would you feel? 4) If you were about to have your teeth scaled and polished, how would you feel? 5) If you were about to have a local anaesthetic injection in your gum, above an upper back tooth, how would you feel?

Each indicator is divided into five levels with a score from 1 to 5: 1) Not Anxious 2) Slightly Anxious 3) Fairly Anxious 4) Very Anxious 5) Extremely Anxious. The total score ranges from 5 to 25 points, and usually 15 points is the threshold for mid-to-high dental anxiety [20].

Galvanic Skin Response (GSR).

GSR measurements work by detecting the changes in electrical ionic activity resulting from changes in sweat gland activity. It is found that galvanic skin response can respond to anxiety. A statistically significant correlation was found between galvanic skin conductance and dental anxiety. Advantageously, combining with GSR measurements during the experiment can quantify patients’ anxiety. Caprara measured patients’ dental fear scale, GSC and polygraph response to key verbal questions, finally verified that dental anxiety can be measured objectively by skin conductance [21].

Heart Rate (HR).

Heart rate can reflect the patient’s anxiety during oral treatment. When people feel stress or anxiety, a series of responses come out, such as increased heart rate, blood pressure, blood sugar, and dilated pupils. Heart rate is usually included in the evaluation index when measuring the degree of dental anxiety.

In the study, Brand Psytech were used to collect galvanic skin response and heart rate data.

User Experience Questionnaire (UEQ).

User experience questionnaire was used to evaluate a preferably comprehensive impression of the product user experience from the six aspects of attractiveness, perspicuity, efficiency, dependability, stimulation, and novelty.

4 Result

4.1 MDAS

After the F-test, this study used an independent sample T-test to verify whether the baseline levels of dental anxiety in the experimental group and the control group were consistent. The result shows that there is no significant difference in the degree of dental anxiety between the experimental group and the control group (p = 0.792 > 0.05). The samples are statistically significant (Fig. 3).

Fig. 3.
figure 3

Independent samples text of MDAS (group 1: experimental group; group 2: control group).

Full size image

Moreover, the study used paired-samples T-test to compare the self-reported differences in dental anxiety between the experimental and control groups. There are four sets of MDAS data: the experimental group’s pre-text (Mean = 17.75) and post-text (Mean = 14.33), the control group’s pre-text (Mean = 17.42) and post-text (Mean = 15.83). The data shows that the degree of self-reported dental anxiety decreased in both groups after the experiment. there is a significant difference between the pre-test and post-test in the experimental group (p = 0.002 < 0.01), and there has a difference between the pre-test and post-test in the control group, but the difference was not significant. (P = 0.027 < 0.05) The data above proves the effectiveness of the virtual reality dental anxiety mitigation tool based on computerized cognitive behavioral therapy. At the same time, direct exposure to the virtual dental environment also has certain utility (Fig. 4).

Fig. 4.
figure 4

Paired samples text of MDAS.

Full size image

4.2 SC/GSR

Figure 5 shows one typical participant’s GSR, BVP and HR trend which are measured with biosignal recorder during the experiment. It is found that as the experiment progresses, the participant’s GSR decreasing gradually.

Fig. 5.
figure 5

One typical participant’s GSR, BVP and HR trend during the experiment.

Full size image

Furtherly, the study used paired-samples T-text to analyze the changes between the pre-text and post-text of the experimental group and control group after confirming that there is no significant difference in the degree of the galvanic skin response between the experimental group and the control group before the experiment. The first 30 s of the experiment was selected as the pre-test data, and the last 30 s of the experiment was used as the post-test data. The data shows that both experimental group and control group have a significant difference (experimental group: p = 0.003 < 0.05, control group: p = 0.004 < 0.05) (Fig. 6).

Fig. 6.
figure 6

Paired samples text of GSR (group 1: experimental group’s pre-text; group 2: experimental group’s post-text; group 3: control group’s pre-text; group 4: control group’s post-text).

Full size image

The research furtherly used a scatter plot to analyze whether the difference is reflected in relieving or increasing anxiety. In the scatter plot, the pre-text is used as the independent variable, and the post-test is used as the dependent variable. According to the chart, most of the scattered points are below the line y = x. The significant difference is reflected in relieving the dental anxiety. Scilicet, the participants in the two groups’ dental anxiety level decreased after using the product (Fig. 7).

Fig. 7.
figure 7

The scatter plot of the experimental group (left) and control group (right).

Full size image

Moreover, an independent sample T-test was used to compare the difference of GSR between the experimental group and the control group (p = 0.138 > 0.05). It can be seen that the design of the two groups can alleviate the level of anxiety, but the difference between the two groups is not significant.

4.3 HRV

The study used paired-samples T-test to analyze the differences between the time-domain index RMSD and SDNN of the heart rate variability between the experimental group and the control group (Fig. 8).

Fig. 8.
figure 8

Paired samples text of HRV

Full size image

In terms of RMSSD, there is a significant difference between the experimental group’s pre-text and post-test (p = 0.019 < 0.05) while there is no significant difference between the control group’s pre-text and post-test (p = 0.098 > 0.05). And in terms of SDNN, there is a significant difference between the experimental group’s pre-text and post-test (p = 0.002 < 0.05) while there is no significant difference between the control group’s pre-text and post-test (p = 0.119 > 0.05).

4.4 UEQ

The study combines the user experience questionnaire to evaluate the user experience of product design from the six aspects of attractiveness, perspicuity, efficiency, dependability, stimulation, and novelty. In general, the user experience of the experimental group is better than that of the control group. And the product design of the experimental group is more prominent in three aspects of attractiveness, novelty and perspicuity. These three aspects have a significant difference between the two groups (Figs. 9 and 10).

Fig. 9.
figure 9

Independent samples text of UEQ (group 1: experimental group; group 2: control group).

Full size image
Fig. 10.
figure 10

The mean value and standard deviation of the UEQ’s six aspect (experimental group: figure left; control group: figure right).

Full size image

5 Discussion

It is found that participants had higher levels of dental anxiety before intervention. The anxiety level of experimental group and control group are both decreased after intervention. And the anxiety level of VR-CBT group was significantly lower than that of the control group. This demonstrates the effectiveness of cognitive behavioral therapy combined with virtual reality, while also finding that exposing patients to virtual reality environments directly also plays a role. Compared with exposure therapy under virtual reality, cognitive behavioral therapy in virtual reality environment is obviously more effective, and the result shows that the user experience of the VR-CBT group is better than the control group especially in terms of attractiveness, novelty and perspicuity. In addition, combined with the MDAS and GSR index before and after the experiment, the correlation between the GSR and dental anxiety emotions can be verified.

This study is an interdisciplinary research in the field of health care and industrial design. It provides a virtual reality product design to release dental anxiety that can be used at home. The first advantage of the design lies in the vivid dentistry environment that virtual reality simulated. It can let patients who tend to delay or refuse to see a doctor adjust their mood remotely and seek medical advice timely, and the treatment experience becomes better accordingly. Secondly, computerized cognitive behavioral therapy based on virtual reality can replace oral imparting experience. By the time, it allows patients to control the treatment process autonomously and professional therapists will be no longer needed. This is a new practice of virtual reality in the field of medical, which has certain practical significance and clinical value. The study shows that computerized cognitive behavioral therapy combined with virtual reality is an effective method to alleviate the emotion of anxiety in dental treatment. However, there are still some limitations. The experiment belongs to a short-term experiment, which can only test state anxiety but do not reflect the effects of long-term trait anxiety. In the future, the sample size will be expanded and long-term intervention will be included.