Does orthodontic treatment improve the Oral Health-Related Quality of Life when assessed using the Malocclusion Impact Questionnaire—a 3-year prospective longitudinal cohort study

Objectives

To assess the change in Oral Health-Related Quality of Life (OHRQoL) following orthodontic treatment using the Malocclusion Impact Questionnaire (MIQ) and to test the responsiveness of MIQ to treatment-associated changes.

Methods

A longitudinal prospective cohort study, in an orthodontic postgraduate centre, Kerala, India. Patients under 18 years were invited to complete the MIQ before the start of treatment (T0) and 1 month after treatment completion (T1). TheIndex of Orthodontic Treatment Need and Peer Assessment Rating (PAR) scores were assessed at both time periods as well as a global transition judgement at T1.

Results

Two hundred and ten participants were recruited and 162 completed both questionnaires (45.1% males; 54.9% females; age = 12–18 years, mean = 16.8; SD = 1.7). There was large reduction in MIQ scores from T0 (mean = 28.1, SD = 6.1) to T1 (mean = 3.7, SD = 2.6). 53% reported a large improvement in oral health and related life quality after treatment, 32% minimal change, and 15% no change. None reported worsening in OHRQoL at T1. There was a significant positive correlation between change in MIQ score and change in PAR score (r = 0.358), pretreatment aesthetic component (rho = 0.467) and dental health component (rho = 0.491) of the index of orthodontic treatment (IOTN-DHC), and treatment time (rho = 0.502). Regression analysis revealed the change in PAR score and pretreatment IOTN-DHC to be independent predictors of change in MIQ score. Standardized effect size (4.0) and standardized response mean (2.9) were large and the minimal important difference was 7.7. Receiver operating characteristic analysis reported a high diagnostic accuracy of MIQ.

Conclusions

There was a significant improvement in OHRQoL following orthodontic treatment when assessed using a condition-specific measure for malocclusion. MIQ was found to be responsive to changes associated with orthodontic treatment.