Two forward translations were made of the original English IDAF-4C+ into Finnish. One translator was aware of the concept and the other, the so-called naive translator, was neither aware nor informed of the concept. A new Finnish version was subsequently derived by SL based on the original and the two translated versions. After that, the native English translator, blinded to the original version, translated it back into the original language as a type of validity check. Finally, an expert committee on dental fear (SL and JA) reviewed all the translations including the original version and reached a consensus on discrepancies.
The Finnish version of the IDAF-4C+ was tested in the University of Turku and the study population consisted of dental students of all study grades (n = 202). A printed questionnaire consisting of three parts was given to every dental student after an exam. The first part was the Finnish translation of the IDAF-4C+ consisting of 23 items related to all three modules (8 items for the IDAF-4C, 5 items for the IDAF-P, 10 items for the IDAF-S). The second part was the Finnish version of the MDAS consisting of five questions. Third part consisted of questions about participant’s demographic profile including state of study course, age and gender.
The core fear module (IDAF-4C) of the IDAF-4C+ consists of eight items with five possible responses to each question, ranging from “disagree” (score = 1) to “strongly agree” (score = 5). The core fear module measures the four components of dental anxiety and fear and contains two items about each component: physiological (“I feel anxious shortly before going to the dentist” and “My heart beats faster when I go to the dentist”), behavioral (“I delay making appointments to go to the dentist” and “I generally avoid going to the dentist because I find the experience unpleasant or distressing”), cognitive (“I think that something really bad would happen to me if I were to visit a dentist” and “I often think about all the things that might go wrong prior to going to the dentist”) and emotional (“I get nervous or edgy about upcoming dental visits” and “I feel afraid or fearful when visiting the dentist”. The scale contains items measuring both anxiety (generally regarded as comprising an anticipatory response) and fear (which comprises the set of responses arising out of actual exposure to the feared stimulus). Those with an IDAF-4C+ mean score ≤2.5 were considered to have no to moderate fear, those with mean score ≥3.5 were considered to have high to extreme fear, and those in the middle were considered as having moderate to high fear [7, 15].
The phobia module (IDAF-P) consists of five items with two possible responses, “Yes” or “No”. The first three items address criteria for a dental phobia diagnosis, and the other two items aim to provide a differential diagnosis of social phobia and panic disorder according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) . A response of “Yes” to the first three items and a response of “No” to the last two items, together with marked fear according to IDAF-4C+ mean score (suggested cut-point mean value ≥ 3), is considered as satisfying a case definition for dental phobia [7, 15].
The stimulus module (IDAF-S) includes 10 items with five possible responses to each question, ranging from “Not at all” (score = 1) to “Very much” (score = 5). These items are intended to be analyzed individually.
The MDAS is a widely used five-item instrument for self-rating dental fear showing validity evidence and high internal consistency (Cronbach’s alpha = 0.93) and reliability over time (intra-class correlation coefficient = 0.93) . The items ask people how they would feel if they “…went to your dentist for treatment tomorrow”, “…were sitting in the waiting room (waiting for treatment)”, “…were about to have a tooth drilled”, “…were about to have your teeth scaled and polished”, and “…were about to have a local anesthetic injection in your gum, above an upper back tooth”. Each item has five response alternatives ranging from 1 (‘Not anxious’) to 5 (‘Extremely anxious’), with the range for total sum score being 5–25. Consistent with previous research, the MDAS total score was categorized into ‘No fear’ (5–9), ‘Low/Moderate fear’ (10–18) and ‘High fear’ (19 or more) groups. MDAS has a two factor structure, consisting of anticipatory anxiety (items 1 and 2, range 2–10) and treatment related anxiety (items 3, 4 and 5, range 3–15) .
Distributions of IDAF-4C+, IDAF-4P and IDAF-4S items were evaluated. Prevalence estimates were calculated for IDAF-4C+ and MDAS using the pre-defined cut-points for both scales. The prevalence estimates were compared by participant gender with both scales using cross tabulation and chi square test. As IDAF-4C+ has previously demonstrated one factor structure exploratory factor analysis (EFA) with varimax rotation was conducted to see if there were more than one underlying constructs within the measure. The differences in IDAF-4C+ and MDAS scores between male and female participants were evaluated with Mann-Whitney U tests. The associations between IDAF-4C+ and MDAS scores and their components were evaluated with Spearman correlation coefficients. Reliability of the scales was evaluated using Cronbach’s alphas.