Translation, cross-cultural adaptation, and psychometric properties of the Finnish version of the Malocclusion Impact Questionnaire (MIQ)

Objectives: This study aimed to translate and adapt the Malocclusion Impact Questionnaire (MIQ) into Finnish; to estimate its psychometric properties when applied to Finnish adolescents; and to estimate the effect of demographic characteristics on the perceived impact of malocclusion. Methods: The Finnish version of MIQ (MIQ-Fi) was established through translation, back-translation, and a pilot study. Psychometric properties were estimated using factorial validity (confirmatory factor analysis [CFA]), convergent validity (Average Variance Extracted [AVE]), and reliability (α_ordinal and ω). Structural Equation Model estimated the effect of demographic characteristics on malocclusion impact. Results: A total of 268 Finnish adolescents participated in the study (mean age = 13.4 [standard deviation, SD = 1.5] years, 48.5% girls). MIQ-Fi factor model presented an adequate fit to the data after refinements (CFA: comparative fit index [CFI] = 0.96, Tucker-Lewis index [TLI] = 0.95, standardized root mean square residual [SRMR] = 0.08, exclusion of 4 items and 1 correlation between items error). Convergent validity (AVE = 0.61) and reliability (α_ordinal and ω ≥ 0.90) were adequate. Gender and self-reported need for orthodontic treatment had moderate effects on malocclusion impact (β_standardized = 0.36 and 0.30, respectively, p < 0.01), while other demographic characteristics had weak effects (β_standardized < |0.18|, p < 0.04). Conclusion: MIQ-Fi demonstrated adequate psychometric properties and can measure malocclusion impact in Finnish adolescents. Demographic characteristics had weak to moderate effect on the maloc-clusion impact.