METHODS: The published English version of PIDAQ was pilot tested on 12- to 17-year-old adolescents, resulting in a few modifications to suit the Malaysian variety of English. Psychometric properties were tested on 393 adolescents who attended orthodontic practices and selected schools. Malocclusion was assessed using the Malocclusion Index, an aggregation of Perception of Occlusion Scale and the Aesthetic Component of the Index of Orthodontic Treatment Need, by the subjects (MI-S) and investigators (MI-D). Data were analysed for internal consistency and age-associated invariance, discriminant, construct and criterion validities, reproducibility and floor and ceiling effects using AMOS v.20 and SPSS v.20.

RESULTS: The item Don't like own teeth on video of the Aesthetic Concern (AC) subscale was not relevant to a large proportion of participants (11.7%). Therefore, it was removed and the Malaysian English PIDAQ was analysed based on 22 items instead of 23 items. Confirmatory factor analysis showed good fit statistics (comparative fit index: 0.902, root-mean-square error of approximation: 0.066). Internal consistency was good for the Dental Self-Confidence, Social Impact and Psychological Impact subscales (Cronbach's alpha: 0.70-0.95) but lower (0.52-0.62) though acceptable for the AC subscale as it consisted of only 2 items. The reproducibility test was acceptable (intra-class correlations: 0.53-0.78). For all PIDAQ subscales, the MI-S and MI-D scores of those with severe malocclusion differed significantly from those with no or slight malocclusion. There were significant associations between the PIDAQ subscales with ranking of perceived dental appearance, need for braces and impact of malocclusion on daily activities. There were no floor or ceiling effects.