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Objectives: Dental implant treatment (DIT) improves peoples’ oral health-related quality of life (OHQoL). Assessment of changes in OHRQoL may be undermined by response shift (RS). RS is the process by which quality of life change, independent of health status as a result recalibration, reprioritization or reconceptualization. Thus, this research aimed to identify RS in individuals receiving dental implant treatment and to determine the validity of three approaches to measure it; the then-test, the self-anchored scale and the classification and regression trees (CRT). Methods: OHRQoL was assessed in 100 patients receiving DIT using the OHIP-Edent and the self-anchored scale before placement of the final restoration and 3 to 6 months after the treatment was completed. The OHIP-Edent was also used as a retrospective assessment at the follow-up. CRT examined changes in the OHIP-Edent total score as a dependent variable with global changes in oral health and each OHIP-Edent subscale score as independent variables. Results: OHRQoL improved after treatment. The OHIP-Edent score decreased from 36.4 at baseline to 12.7 after treatment. On average participants recalibrated their internal standard downwards (-4.0 OHIP-Edent points). The CRT detected recalibration (5% downwards and 15% upwards). Reprioritization was observed among the social disability and psychological discomfort aspects of OHRQoL. Conclusions: RS affects longitudinal assessments of OHRQoL in DIT reducing the apparent magnitude of change. Results of this study identified then-test and the CRT as valid complementary methods to assess RS.