Validity and reliability of the Turkish version of the malocclusion impact questionnaire (MIQ)

Background: The Malocclusion Impact Questionnaire (MIQ) assesses oral health-related quality of life (OHRQoL) in patients aged 10-16 years with malocclusion. This cross-sectional study aims to create a Turkish version of the MIQ (MIQ-T) and evaluate its suitability for Turkish adolescents in determining malocclusion's impact on OHRQoL. Methods: The MIQ-T was developed following recommended guidelines. A total of 350 adolescents, aged 10-16 years, were recruited to the study to evaluate the psychometric properties of the questionnaire. For assessing the psychometric properties of the questionnaire, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), content validity, convergent validity, internal consistency and test-retest reliability methods were employed. Results: EFA identified three subgroups with a total variance of 65.911%. The CFA showed all fit indices met acceptable standards: Root Mean Square Error of Approximation (RMSEA) = 0.07, The Chi-square Degree of Freedom (CMIN/df) = 3.016, Tucker-Lewis Index (TLI) = 0.94, Goodness-of-Fit Index (GFI) = 0.90, and Comparative Fit Index (CFI) = 0.95. Convergent validity coefficients for the two global questions and specific items were 0.690 and 0.680, respectively. Test-retest reliability was 0.890, and the MIQ-T demonstrated strong internal consistency with Cronbach's alpha of 0.915. Split-half reliability analysis showed Cronbach's alpha values of 0.918 and 0.745 for the first and last nine items, respectively. Conclusions: These findings suggest that the MIQ-T is a useful tool for assessing the impact of malocclusion on OHRQoL in Turkish adolescents.