Abstract
Objectives
The use of questionnaires to assess patients’ dental fear is critical to dental research and practice. As one of the most well-established tools in this field, the Dental Fear Survey (DFS) was translated into Vietnamese (V-DFS) and employed in previous studies. However, its validity and reliability have not been reported. This study aimed to determine the validity and reliability of V-DFS in adults.
Methods
The DFS was translated to Vietnamese in accordance with the “Guideline for the Process of Cross-cultural Adaptation of Self-reported Measures” to create the V-DFS. Next, 414 students at Pham Ngoc Thach University of Medicine completed the V-DFS to examine its validity and reliability. The factorial validity of V-DFS was assessed using exploratory factor analysis (EFA) and structural equation modeling (SEM). The internal consistency and test-retest reliability of the V-DFS were assessed using Cronbach's alpha (α), intraclass correlation coefficient (ICC), and Spearman's rank-order correlation coefficient (rs).
Results
The rotated component matrix of the EFA revealed 3 factors: specific stimuli, anticipatory fear and avoidance, and physiologic arousal. The statistical indices of the best-fitting V-DFS model in SEM analysis satisfied the cutoff values. Cronbach's α ranged from .82 to .94 for the 3 factors. The ICC and rs of the whole questionnaire were .86 and .86, respectively.
Conclusions
DFS was successfully translated into Vietnamese with good validity and reliability. Further research should be conducted to examine its validity in various populations and to improve its characteristics.
Key words: Dental Fear Survey, Vietnamese version, Reliability, Validity, SEM
Introduction
Dental fear is one of the 2 most common barriers preventing people from undergoing oral health examinations. It can be caused by either cognitive perceptions or catastrophic dental experience.1 As a result of this, patients who are more fearful of dental treatment tend to present with more serious oral disease.2 Therefore, the early detection of dental fear can help dentists recognise patients with this problem.
There are numerous methods to assess dental fear, including self-reported, observation-based, and physiologic assessments.3 To date, self-reported assessment using questionnaires is still the most common method because of some advantages. First, it is simple and convenient to perform. Second, questionnaires for assessing dental fear vary in purpose and structure, so clinicians can choose the appropriate one based on their demands.4,5 Third, self-reported assessments are less likely to depend on the patients’ physiologic condition and the assessor.3
Since the first dental fear questionnaire, Corah's Dental Anxiety Survey (DAS), appeared in 1969, a number of others have been developed, including Kleinknecht's Dental Fear Survey (DFS) in 1973, Stouthard's Dental Anxiety Inventory (DAI) in 1995, their modified versions, and some recently introduced questionnaires.5 In a critical review, DFS was one of the most recommended questionnaires for assessing dental fear because the construct was based on an explained behavioral approach with high reliability and validity.6 Originally written in English, the DFS has been translated into several languages for research and use in many countries, including Arabic, Spanish, Portuguese, Japanese, Korean, Turkish, and Greek.7, 8, 9, 10, 11, 12, 13 Employing the DFS in a non-native English-speaking country with different culture is classified as the most challenging scenario.14 As a result of this, some translated versions of DFS showed low reliability or violated principles of construct validity.
In Vietnam, there is a limited understanding of dental fear because of a lack of research. Some previous studies used the Vietnamese version of the DFS (V-DFS) as a method for assessing dental fear but did not evaluate reliability and validity of the translation.15,16 A translated version with confirmed reliability and validity are in demand to guarantee that the questionnaire result can be reproduceable and trustworthy.17 Therefore, using the V-DFS, for which the reliability and validity have not been investigated, makes their results less reasonable, because differences in culture and fear perception can affect translated versions.3 In addition, the previous translation of the V-DFS has not been published for using in daily practice or research. This study aimed to translate the DFS into Vietnamese and examine the validity and reliability of the V-DFS.
Methods
This study was conducted in 2 stages. In stage 1, the original DFS was translated into Vietnamese following the “Guidelines for the Process of Cross-cultural Adaptation of Self-reported Measures.”14 In stage 2, the validity and reliability of the V-DFS were examined in adults.
Stage 1
The original DFS was translated into Vietnamese by 2 bilingual translators. The first translator was a dentist who understood the purpose of using the DFS. The second was an English teacher who was unaware of the aim of the questionnaire and had no professional knowledge of dentistry. The differences between the 2 forward translations are discussed to solve and develop a forward translation of the V-DFS. Backward translation was then conducted by 2 native English speakers who were naïve to the original DFS content. The pre-final translated version was produced based on the consensus of a committee that included all translators and researchers. Thirty volunteer students were asked to answer the pre-final version and give their opinions regarding the translated words. Based on these comments, the prefinal version was modified to produce the final V-DFS (Appendix A. The Vietnamese version of the Dental Fear Survey).
Stage 2
Participants
The participants were undergraduate students at the Pham Ngoc Thach University of Medicine (PNTU). The second largest medical university in Ho Chi Minh City, PNTU particularly educates health care professionals, with approximately 6500 students. The students who participated in this study were from 4 health care programmes: medicine, dentistry, pharmacy, and nursing.
Procedure
From January to March 2021, the questionnaire was distributed and described in all classes of PNTU as an extracurricular activity by the academic advisers. The questionnaire was anonymous so that students were not hesitant to enroll in the study. Under PNTU's rules, this study protocol did not require permission from the ethics committee.
In the first administration, 499 undergraduate students voluntarily agreed to participate in the study (response rate of ≈7.7%). The final V-DFS questionnaire of stage 1 was introduced to the participants by a researcher (T. N. N.), the participants self-answered the questionnaire, and the procedure was repeated at a 3-week interval. Subsequently, a researcher (U.-A. T. D.) screened the answers to remove some participants. Exclusion criteria were as follows: (1) incompletely answered questionnaires, (2) no previous experience of dental treatment, and (3) previous diagnosis of any psychologic problems.
Statistical analysis
Data conversion. The collected data were input into an Excel database and then copied to SPSS 22.0 for statistical analysis.
Validity assessment. The V-DFS was assessed for factorial validity to examine cross-cultural validation. All answer sheets from the first survey were interpreted using exploratory factor analysis (EFA) and structural equation modeling (SEM). The methodology was described in detail in “Multivariate data analysis.”18 EFA was conducted using principal components and the varimax rotation method to determine the latent factors of the questionnaire. Based on this result, the rotated component matrix was input in AMOS 20.0 (IBM) to perform SEM. The preliminary model of the SEM analysis was assessed the goodness-of-fit (GOF) using the following statistical indices: chi-square fit statistics/degree of freedom (CMIN/df), root square mean error of approximation (RSMEA), standardised root mean squared residual (SRMR), comparative fit index (CFI), and parsimony normed fit index (PNFI). According to Hair et al, the recommended cutoff values for GOF were as follows: CMIN/df ≤ 3; RSMEA ≤ .07; SRMR ≤ .08; and CFI ≥ .94. Exceptionally, there is no cutoff value for PNFI, but it should be as high as possible to increase the model fit.18 The best-fitting model was then produced by correlating couples of the observed variables that had high modification indices to improve the GOF.
Reliability assessment. The V-DFS reliability was examined using internal consistency and test-retest reliability. Internal consistency was determined using Cronbach's α test. Test-retest reliability was determined by calculating the intraclass correlation coefficient (ICC) and Spearman's rank-order correlation coefficient (rs).
Results
The number of students who answered the questionnaire in the first administration was 499. After screening the answers, 85 participants were removed due to the following exclusion criteria: uncompleted questionnaire (n = 10), no dental experience (n = 55), and psychological problems (n = 20). Consequently, the V-DFS score of 414 students were used to interpret the V-DFS validity. Of the sample, the mean age was 21.40 ± 2.03 years (range, 19–32 year), and the female percentage was 62.8%. Amongst them, 263 participants finished the V-DFS in the second administration, and their results were used to interpret the V-DFS reliability. The mean value score for each question and for the entire V-DFS questionnaire is shown in Appendix B. The Vietnamese version of the Dental Fear Survey scores in two administrations.
In Table 1, the EFA revealed 3 latent factors of the V-DFS. Based on the medical literature and nature of the questions, factors 1, 2, and 3 were named specific stimuli, anticipatory fear and avoidance, and physiologic arousal, respectively. Statistical analysis showed that the EFA model fit the present study data with a Kaiser–Meyer–Olkin sample adequacy of .923, a P value for Bartlett's test of sphericity <.001, and a total explained variance of 64.70%. All V-DFS questions had factor loadings higher than .40 and communality higher than .25.
Table 1.
Rotated component matrix of the Vietnamese version of the Dental Fear Survey (n = 414).
| Items | Factor loading |
Communality | ||
|---|---|---|---|---|
| 1 | 2 | 3 | ||
| DFS1 | .093 | .587 | .131 | .371 |
| DFS2 | -.057 | .538 | .233 | .347 |
| DFS3 | .231 | .135 | .642 | .484 |
| DFS4 | .206 | .100 | .863 | .797 |
| DFS5 | .174 | .250 | .751 | .657 |
| DFS6 | .086 | .297 | .423 | .275 |
| DFS7 | .313 | .176 | .770 | .722 |
| DFS8 | .282 | .754 | .100 | .657 |
| DFS9 | .382 | .771 | .119 | .755 |
| DFS10 | .386 | .708 | .197 | .689 |
| DFS11 | .551 | .607 | .245 | .731 |
| DFS12 | .494 | .619 | .215 | .674 |
| DFS13 | .517 | .623 | .241 | .713 |
| DFS14 | .823 | .212 | .135 | .741 |
| DFS15 | .820 | .134 | .160 | .716 |
| DFS16 | .849 | .202 | .196 | .801 |
| DFS17 | .845 | .216 | .209 | .805 |
| DFS18 | .826 | .187 | .225 | .767 |
| DFS19 | .577 | .253 | .290 | .481 |
| DFS20 | .720 | .378 | .309 | .757 |
| Eigenvalues | 9.632 | 1.721 | 1.587 | |
| Percentage of explained variance | 48.159 | 8.607 | 7.934 | |
Note. The exploratory factor analysis was conducted with principal components and varimax rotation method.
The preliminary and best-fitting models are shown in Fig. 1, Fig. 2, respectively. For the preliminary model, the model fit test was acceptable, with CMIN/df = 6.24, RMSEA = .11, SRMR = .07, CFI = .86, and PNFI = .74. However, there was a significantly high covariance between the error terms of DFS1 and DFS2, DFS8 and DFS9, DFS9 and DFS10, DFS14 and DFS15, DFS16 and DFS20, DFS17 and DFS20, and DFS19 and DFS20. After adding the relationship between those pairs of items, the best-fitting model showed a significant improvement in model fit with CMIN/df = 2.98, RMSEA = .07, SRMR = .06, CFI = .95, and PNFI = .78. The factor loadings of each question and all correlation indices are presented in Figure 2. Notably, the factor loadings of DFS1, DFS2, and DFS6 with their respective latent factors are low.
Fig. 1.
Preliminary model of the Vietnamese version of the Dental Fear Survey based on rotated component matrix of exploratory factor analysis (n = 414).
Fig. 2.
The best-fitting model of the Vietnamese version of the Dental Fear Survey (n = 414).
As shown in Table 2, the V-DFS revealed good internal consistency for all factors, with Cronbach's α ranging from .82 to .94. All V-DFS items showed acceptable corrected item-total correlations (.35–.88) and α if the item was deleted (.73–.94). Notably, the α values if the DFS1, DFS2, DFS6, and DFS19 items were deleted were slightly higher than the Cronbach's α of the individual factors; however, their corrected item-total correlation values were still higher than .30.
Table 2.
Internal consistency reliability of the Vietnamese version of the Dental Fear Survey.
| Items | First administration (n = 414) |
Second administration (n = 263) |
||||
|---|---|---|---|---|---|---|
| Corrected item-total correlation | Alpha if item deleted | Cronbach's alpha | Corrected item-total correlation | Alpha if item deleted | Cronbach's alpha | |
| Anticipatory fear and avoidance | .90 | .90 | ||||
| DFS1 | .43 | .91 | .35 | .91 | ||
| DFS2 | .36 | .91 | .38 | .91 | ||
| DFS8 | .70 | .88 | .75 | .88 | ||
| DFS9 | .80 | .87 | .82 | .87 | ||
| DFS10 | .78 | .88 | .82 | .87 | ||
| DFS11 | .80 | .87 | .79 | .88 | ||
| DFS12 | .76 | .88 | .76 | .88 | ||
| DFS13 | .79 | .87 | .80 | .88 | ||
| Physiologic arousal | .82 | .84 | ||||
| DFS3 | .54 | .80 | .60 | .82 | ||
| DFS4 | .76 | .73 | .78 | .77 | ||
| DFS5 | .67 | .76 | .64 | .81 | ||
| DFS6 | .35 | .84 | .47 | .85 | ||
| DFS7 | .72 | .74 | .73 | .78 | ||
| Specific stimuli | .94 | .94 | ||||
| DFS14 | .80 | .93 | .77 | .93 | ||
| DFS15 | .79 | .93 | .78 | .93 | ||
| DFS16 | .85 | .92 | .87 | .92 | ||
| DFS17 | .86 | .92 | .88 | .92 | ||
| DFS18 | .84 | .92 | .86 | .92 | ||
| DFS19 | .61 | .94 | .66 | .94 | ||
| DFS20 | .81 | .93 | .80 | .93 | ||
The V-DFS showed excellent overall correlation, with an ICC = .86 and rs = .86 (Table 3). All items of the V-DFS obtained moderate ICC values, ranging from .55 to .77, except for DFS2 and DFS2 (ICC = .45) and DFS6 (ICC = .44). However, the scores between the 2 administrations were significantly correlated (P < .001). ICC values for each factor were as follows: .76 (.70–.81) for anticipatory fear and avoidance, .71 (.64–.76) for physiologic arousal, and .83 (.79–.87) for specific stimuli. Regarding Spearman's rank-order correlation, all rs values were higher than .50, except for DFS2 and DFS6 (rs = .47, P < .001). rs values for anticipatory fear and avoidance, physiologic arousal, and specific stimuli were .73, .68, and .84, respectively.
Table 3.
Test-retest reliability of the Vietnamese version of the Dental Fear Survey (n = 263).
| Items | Intraclass correlation coefficient (95% confidence interval) | F (262, 262) | Spearman's rank-order correlation coefficient |
|---|---|---|---|
| Anticipatory fear and avoidance | .76 (.70–.81) | 7.33 | .73 |
| DFS1 | .56 (.47–.64) | 3.53 | .52 |
| DFS2 | .45 (.35–.54) | 2.65 | .47 |
| DFS8 | .55 (.46–.63) | 3.42 | .49 |
| DFS9 | .61 (.52–.68) | 4.07 | .58 |
| DFS10 | .64 (.56–.71) | 4.55 | .61 |
| DFS11 | .70 (.64–.77) | 5.74 | .69 |
| DFS12 | .67 (.59–.73) | 4.96 | .68 |
| DFS13 | .63 (.56–.70) | 4.46 | .59 |
| Physiologic arousal | .71 (.64–.76) | 5.77 | .68 |
| DFS3 | .62 (.54–.69) | 4.21 | .60 |
| DFS4 | .57 (.48–.65) | 3.67 | .54 |
| DFS5 | .55 (.46–.63) | 3.49 | .50 |
| DFS6 | .44 (.34–.53) | 2.60 | .47 |
| DFS7 | .65 (.57–.71) | 4.74 | .60 |
| Specific stimuli | .83 (.79–.87) | 10.81 | .84 |
| DFS14 | .77 (.72–.82) | 7.76 | .77 |
| DFS15 | .76 (.70–.80) | 7.23 | .76 |
| DFS16 | .70 (.63–.76) | 5.60 | .70 |
| DFS17 | .77 (.72–.82) | 7.75 | .76 |
| DFS18 | .70 (.63–.76) | 5.68 | .69 |
| DFS19 | .66 (.58–.72) | 4.83 | .65 |
| DFS20 | .75 (.69–.80) | 7.12 | .75 |
| Total | .86 (.83–.89) | 13.35 | .86 |
P < .001 for all items, factors, and total Vietnamese version of the Dental Fear Survey in both intraclass correlation coefficient and Spearman's rank-order correlation coefficient analysis.
Discussion
The study results demonstrated the appropriate validity and reliability of the V-DFS. The V-DFS contains 3 main factors related to dentistry: anticipatory fear and avoidance, physiologic arousal, and specific stimuli. The best-fitting model of the V-DFS not only satisfied the statistical requirements of the SEM model fit but also had the same construction with the original DFS. The V-DFS also showed excellent internal consistency and good test-retest reliability.
This study is not the first one in which the Vietnamese translation of DFS was utilised.15,16 One of the authors (S. H. L.) witnessed some patients’ confusion when choosing the appropriate level of dental fear in the previous Vietnamese translation due to ambiguous distinction between translated words for level 2-3-4 of the answer. Such confusion is common in Likert-type questionnaire and may mislead the results.19 Therefore, the authors agreed to make a new translation from the beginning with new translators. Comparing with the translated version of previous studies, the main difference was the words for determining levels of dental fear of the answers.
The DFS was introduced in 1973, and its construct validity was first reported in 1984.6 To date, the translated version of the DFS has been examined for construct validity in some languages, such as Japanese (J-DFS), Korean (K-DFS), Brazilian Portuguese (P-DFS), and Lebanese Arabic (A-DFS). In the original and translated versions of the DFS, 3 main factors related to dental treatment were observed: anticipatory fear and avoidance (DFS1, DFS2, and DFS8 to DFS13), physiologic arousal (DFS3 to DFS7), and specific stimuli (DFS14 to DFS20).6,7,10,13 However, the K-DFS showed a different factorial construct that highlighted the effect of anaesthesia and drilling on dental fear.20 Similarly, another previous study reported that the DFS contained 6 factors that highlighted the influence of needles and drilling on dental fear.21 However, the participants in those studies were patients diagnosed with dental phobia and adolescences, which could affect the assessment of DFS factorial functions when applied to these populations. In accordance with the original DFS and most translated versions, this study identified 3 factors affecting dental fear.
The best-fitting models of the Japanese, Lebanese Arabic, and Vietnamese versions of DFS showed appropriate statistical results for factorial validity with GOF indices that were higher than the recommended cutoff values.18 Although some statistical indices of the V-DFS were not as good as those of other language versions of the DFS, the salient point was that its best-fitting model did not contain any between-construct error covariance that appeared in other language versions of the DFS.18 Additionally, the number of within-construct error covariances of the V-DFS was much lower than those of the J-DFS and P-DFS.7,13 In other words, the factorial validity of the V-DFS was appropriate and complied with the fundamental psychometric principles of a good questionnaire.
The reliability of the V-DFS was confirmed by analysing internal consistency and test-retest reliability. Cronbach's α for each item and factor satisfied the standard requirements of internal consistency, with a corrected item-total correlation higher than .30 and factor α values higher than .80. Compared with the reported Cronbach's α of previous studies, this study's results were somewhat lower. In the J-DFS, K-DFS, A-DFS, and Greek versions of the DFS, all items were examined for internal consistency as one group, whereas the DFS was built on several factors.7, 8, 9, 10 As a result, the Cronbach's α values were too high (≥.94), indicating redundancy.22 According to the authors’ opinion, it would be more appropriate to examine the internal consistency of every group following EFA results. Based on the statistical results, it is likely that DFS1, DFS2, DFS6, and DFS19 could be removed from the V-DFS to reduce the length of the questionnaire without affecting its homogeneity.
The statistical results of the V-DFS showed that the overall questionnaire had good reliability (ICC = .86 and rs = .86). The ICC and rs values of each item ranged from .44 to .77 and .47 to .77, respectively. Amongst the V-DFS items, the statistical results of DFS2 and DFS6 were quite poor, with ICC and rs <.50. One of the most critical factors affecting the test-retest statistical results is the time interval. Increasing the time interval would decrease the test-retest reliability but could reduce the effect of memory.23 A literature review showed that most retests in previous studies were conducted after a week to a month.24 In this study, the second administration of the V-DFS was conducted 3 weeks later, which was longer than with most translated versions of the DFS, to ensure that the effect of memory was minimised. For the DFS in the other languages, the interval times were 1 week for the J-DFS, 2 weeks for the A-DFS and P-DFS, and 4 weeks for the K-DFS. Generally, the reproducibility of the V-DFS was much better than that of the K-DFS (ICC = .40; rs = .09–.49) and comparable to that of the A-DFS (ICC = .92, rs = .70), J-DFS (ICC = .92; rs = .89–.92), and P-DFS (ICC = .88–.90).7,8,10,13 Although the interval between tests was the longest, the V-DFS showed good stability when compared with the other language versions.
The study was conducted with an appropriate method: Translating the DFS questionnaire followed a standard guideline and interpreting the results required specialised statistical calculations. Most previous studies interpreted the factorial validity of the questionnaire with CFA. By using SEM, this study results pointed out the regression relationships between latent factors or observed variables. It is crucial to evaluate the factorial validity and revise the questionnaire in the future. However, there are some limitations that should be overcome in the future studies or clinical practice. First, the study participants were undergraduate students in health sciences, so the V-DFS meaning values might be somewhat lower than those of non–health care related populations because of different knowledge foundations.25 However, the main objective of this study is to evaluate validity and reliability of the V-DFS, but not to provide any reference cutoff value for diagnosing dental fear. Although enrolling health profession students did not affect the study objective, carrying out the V-DFS in the mass population is recommended to acquire more comprehensive understanding of dental fear in Vietnamese patients. Second, although the V-DFS was translated under a rigorous protocol, receiving feedback from other populations, such as people from different majors or generations, is needed to assess dental fear more efficiently when being used amongst a diverse population.26 Third, because there are some minor differences amongst geographic locations in the Vietnamese language, the published V-DFS can be slightly modified to better adapt to individual populations.
Conclusions
Within the limitations of this study, the DFS was translated into Vietnamese with good validity and reliability. The V-DFS can be applied in clinical contexts and in further studies to assess dental fear in Vietnamese patients. The authors also suggest conducting further studies to investigate validity and reliability of the DFS after removing redundant items.
Conflict of Interest
None disclosed.
Acknowledgements
The authors sincerely thank Dr Tien Huu Cao for his valuable contributions to this study.
Footnotes
Supplementary material associated with this article can be found in the online version at doi:10.1016/j.identj.2022.07.009.
Appendix. Supplementary materials
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