The novel coronavirus disease 2019 (COVID-19) hugely impacts individuals’ psychological health and overall wellbeing worldwide [1
]. Social distancing and other public health measures prohibiting social interactions (e.g., city lockdown and school closure) are being implemented by several governments to mitigate the spread of the infection [7
]. Under such circumstances, accessing health care and seeking treatment could be associated with significant psychological distress due to several reasons. First, due to the pain and discomfort associated with the health problems, second, due to the limited availability of health care services and lastly, the fear of risk of COVID-19 infection. More specifically, oral diseases and their treatment could cause significant stress and anxiety during the COVID-19 pandemic. This is because of the high risk of transmission of COVID-19 in dental practices due to the nature of dental treatment procedures and closer proximity of patient with the provider [10
]. For these reasons, there is a greater tendency among individuals to evade dental treatment. This is more so among individuals with dental anxiety who are already more likely to avoid care.
Despite the high risk of cross-infection, adequate protection protocols could help ensure no transmission happens in a dental practice, there is no epidemiological evidence to support that high rates of cross-infection occurs in dental practices. Therefore, oral health care shouldn’t be evaded. It is important that oral health professionals and associated stakeholders adequately identify individuals with dental anxiety [11
To date, one of the commonly used instruments assessing dental fear is the Modified Dental Anxiety Scale (MDAS), which was adapted and refined from the Corah’s Dental Anxiety Scale (CDAS) [16
]. Moreover, the MDAS has been translated into 22 different languages [13
]. Additionally, most psychometric evaluation studies on MDAS show that the MDAS has promising psychometric properties across different populations, including children [13
]. For example, its unidimensionality has been supported in the Arabic version among an adult population [17
]; its test–retest reliability and internal consistency are satisfactory in the Italian version among a pediatric population [20
]; its criterion validity in the Japanese version is confirmed among an outpatient population [13
The MDAS has been translated into Persian to assess the prevalence of dental anxiety [21
]. Although some basic information on the psychometric properties (e.g., internal consistency) has been reported for the Persian MDAS [21
], to the best of our knowledge, no study conducted an advanced analysis to evaluate the psychometric properties of MDAS in Persian or other languages. Table 1
presents the existing psychometric evidence on MDAS from its adaptation in different languages.
The psychometric properties of the MDAS tested in other language versions [13
] cannot guarantee its robustness in assessing dental anxiety for Iranian adolescents. It is possible that the fear or distress associated with COVID-19 might impact the perception of dental anxiety. Hence, the information regarding the psychometric properties of the Persian MDAS during the COVID-19 pandemic is important for oral health professionals to know whether the outcomes assessed using MDAS are trustable. Given the context and the literature gap, the present study aimed to examine the psychometric properties of the Persian MDAS, using two types of psychometric theories [classical test theory (CTT) and modern test theory using Rasch models], among Iranian adolescents during the COVID-19 pandemic period.
Among 3197 participants (mean age was 15.1 years and 47.1% were males), less than a third (31.3%) have visited a dentist in the past year, and nearly one-fifth (18.0%) have never visited a dentist. Regarding their teeth cleaning behaviors, less than a fifth (19.1%) reported of toothbrushing twice a day, and nearly a tenth (8.4%) of the participants never used a toothbrush. Less than a sixth (15.9%) of children used dental floss while nearly half (49.5%) have never used dental floss (Table 2
All the MDAS item scores demonstrated a normal distribution (range of skewness = −0.85 to −0.16; range of kurtosis = −1.09 to −0.18). Moreover, other item properties were satisfactory for all the MDAS items. In the properties derived from CTT, factor loading ranged between 0.87 to 0.98; corrected item to total correlation ranged from 0.69 to 0.78; and test–retest reliability ranged from 0.72 to 0.86. In the properties derived from Rasch analysis, infit MnSq ranged from 0.80 to 1.11; the range of outfit MnSq was 0.84 to 1.10; and DIF values across gender were −0.09 to 0.09 and −0.10 to 0.13 for dentist visit (Table 3
). Apart from item properties, the scale properties of the MDAS were all satisfactory: composite reliability = 0.975; average variance extracted = 0.887; Cronbach’s α = 0.887; McDonald’s ω = 0.851; separation reliability from Rasch = 1.00 (for item separation) and 0.83 (for person separation); separation index from Rasch = 19.87 (for item separation) and 2.23 (for person separation). The results of the EFA showed that the MDAS has a unidimensional structure explaining a variance of 62%. All factor loadings were higher than 0.70 (ranging from 0.72 to 0.87). Moreover, the data confirmed a one-factor structure of MDAS with satisfactory fit indices: CFI = 0.993; TLI = 0.987; RMSEA = 0.069; SRMR = 0.047 (Table 4
The measurement invariance of the MDAS was additionally confirmed by the multigroup CFA. More specifically, no significant differences were found between the nested models of configural model, metric invariance model, scalar invariance model, and strict invariance model across gender (p
-values = 0.57 to 0.97; ΔCFI = 0.000; ΔRMSEA = −0.011 to −0.007; ΔSRMR = −0.006 to 0.001) and time since last dental visit (p
-values = 0.48 to 0.93; ΔCFI = 0.000; ΔRMSEA = −0.011 to −0.006; ΔSRMR = −0.006 to 0.001) (Table 5
The LCA results suggested that the participants should be classified into three levels (AIC = 39,708.98, BIC = 40,085.32, SSABIC = 39,888.32, Entropy = 0.864, LMR test = 1476.572, p
= 0.0337) (Table 5
). The three levels could be identified as low, moderate and high levels of dental anxiety, participant features based on the dental anxiety level are demonstrated in Table 5
. Most of the adolescents clustered in the moderate dental anxiety class, these participants had higher dental anxiety scores than those in the low dental anxiety class but lower than those in the high dental anxiety class. The classes did not differ in relation to the age of the adolescent, fathers’ and mothers’ educational level. The groups with moderate and high levels of dental anxiety had more females (44.6% and 36.7%) than did the group with a low level of dental anxiety (18.8%; p
< 0.001). The groups with moderate and high levels of dental anxiety had fewer participants visiting a dentist in the past six months (90.5% and 90.3%) than did the group with a low level of dental anxiety (91.5%; p
< 0.001) (Table 6
The present study showed that the Persian MDAS had promising psychometric properties among adolescent Iranians, even in the current COVID-19 pandemic situation. More specifically, psychometric testing based on CTT indicated that the Persian MDAS had normally distributed item scores, excellent internal consistency; satisfactory test–retest reliability; and unidimensionality across the genders and dental visiting practice groups. Psychometric testing based on Rasch models also supported the unidimensionality of the Persian MDAS and separation reliability was also excellent. In addition, the Persian MDAS was able to classify the participants into three levels of dental anxiety.
The findings derived from the CTT analyses in the present study are in accordance with the existing literature. For example, the internal consistency of the MDAS was also found to be excellent for Japanese (α = 0.88) [13
], Italian (α = 0.87) [20
], British English (α = 0.89), and Nepali (α = 0.78) adaptations [18
]. The unidimensionality of the MDAS observed in the study was also confirmed in the Arabic version of the MDAS [17
], and the test–retest reliability of the MDAS was satisfactory in the Italian version (r = 0.80) [20
] and the British English version (r = 0.82), similar to this study [19
]. Moreover, the internal consistency findings in the present study echo the prior Iranian study that used the Persian MDAS (α = 0.80) [21
]. Ultimately, the present study’s findings corroborate with other MDAS psychometric studies in different language versions [13
]. Moreover, the present study demonstrated that the MDAS could be applied to the adolescent population, and this finding aligns with a prior study that used MDAS in the pediatric population [20
In this study, we extended our psychometric evaluation to Rasch analysis. Despite both CTT and Rasch analyses being used for psychometric evaluation, they have different statistical assumptions [26
]. Therefore, it is important to provide psychometric information from both analyses to ensure that the instrument is robust and rigorous [26
]. To the best of the authors’ knowledge, no prior research has used Rasch models to investigate the psychometric features of the MDAS. Therefore, findings derived from Rasch models in the present study couldn’t be compared with the existing literature. Future studies should use Rasch models to evaluate the psychometric properties of MDAS in different languages.
During the COVID-19 pandemic period, visiting a dentist may increase the risk of getting infected with COVID-19. Given that oral health is important for individuals’ overall health and quality of life [11
], tackling dental anxiety or dental fear for adolescents during the COVID-19 pandemic period is more critical as the COVID-19 situation further exacerbates the anxiety in dentally anxious individuals. Therefore, it is imperative to identify adolescents with high dental anxiety to promote confidence and provide adequate support to these individuals, thereby preventing avoidance of care in the current COVID-19 situation [30
]. For this purpose, use of validated instruments like ours are of utmost importance to accurately assess dental anxiety. Moreover, the Persian MDAS contains only five items, and its administration requires a very short time. This feature further allows wider use of Persian MDAS in clinical as well as epidemiological contexts.
Limitations of the Study
There are some limitations in the present study. First, the present sample is only representative of Iranian adolescents in Qazvin province, however, the sample size was large. Future studies are thus needed to test the psychometric properties of the Persian MDAS for Iranian adolescents residing in other areas to increase the generalizability of the present study’s findings. Second, we did not compare the Persian MDAS to any gold standard dental fear instruments to examine the criterion validity. Although all the psychometric testing indicated that the Persian MDAS has good reliability and validity, there is still a need to evaluate the criterion validity of the Persian MDAS. Third, the psychometric findings were derived from the data collected during the COVID-19 pandemic. Therefore, level of dental anxiety could have been overestimated by the study participants due to the COVID-19 pandemic. Future studies are warranted to examine the psychometric properties of the Persian MDAS when the COVID-19 pandemic is under control.