Response shift in oral health-related quality of life measurement in patients with partial edentulism

The purposes of this study were to determine whether a response shift was observable after partial denture treatment and to identify the predictors that influenced the response shift magnitude and direction. A total of 173 consecutive patients with no more than eight missing teeth who received implant-supported, fixed or removable partial dentures at Okayama University Dental Hospital were asked to complete a full-version Oral Health-Related Quality of Life (OHRQoL) questionnaire before (pre-test) and after treatment (post-test). Additionally, a short form (then-test) consisting of seven questions selected from the full version had its reliability verified and was utilised to retrospectively assess the pre-treatment OHRQoL status. The difference between the summary scores of the then-test and the pre-test determined the response shift magnitude and direction. The then-test mean score (22.9 +/- 6.6) was significantly lower (worse OHRQoL) than that of the pre-test (26.4 +/- 5.2). The response shift effect size was of moderate magnitude and negative direction (d = -0.78). A multiple regression analysis showed that age (younger patients) (P < 0.01), number of replaced teeth (fewer) (P < 0.01) and pre-test scores (lower) (P < 0.01) were the significant predictors for response shift. In conclusion, a response shift phenomenon with negative and moderate effect size was observed after partial denture treatment. The significant predictor variables were young age, fewer numbers of replaced teeth and lower pre-test scores