Evaluation of the effect of non-surgical periodontal treatment on oral health-related quality of life: estimation of minimal important differences 1 year after treatment.

AIM: To evaluate an individually tailored oral health educational programme on patient-reported outcome compared with a standard oral health educational programme, assess change over time and determine minimal important differences (MID) in change scores for two different oral health related quality of life (OHRQoL) instrument after non-surgical periodontal treatment (NSPT). MATERIALS AND METHODS: In a randomized controlled trial evaluating two educational programmes, patients (n = 87) with chronic periodontitis completed a questionnaire at baseline and after 12 months. OHRQoL was assessed with the General Oral Health Assessment Index (GOHAI) and the UK oral health-related quality-of-life measure (OHQoL-UK). In addition, patients' global rating of oral health and socio-demographic variables were recorded. The MID was estimated with anchor-based and distributions-based methods. RESULTS: There were no differences between the two educational groups. The OHRQoL was significantly improved after treatment. The MID was approximately five for OHQoL-UK with a moderate ES, and three for GOHAI with a Small ES, and 46-50% of the patients showed improvements beyond the MID. CONCLUSION: Both oral health educational groups reported higher scores in OHRQoL after NSPT resulting in more positive well-being (OHQoL-UK) and less frequent oral problems (GOHAI). OHQoL-UK gave a greater effect size and mean change scores but both instruments were associated with the participants' self-rated change in oral health. The changes were meaningful for the patients supported by the estimated MID.