What do measures of 'oral health-related quality of life' measure?

The terms 'health-related quality of life' and 'quality of life' are now in common use to describe the outcomes of oral health conditions and therapy for those conditions. In addition, there has been a proliferation of measures designed to quantify those outcomes. These measures, which were initially designated as socio-dental indicators or subjective oral health indicators are now more usually referred to as measures of oral health-related quality of life (OH-QoL). This is based on the assumption that the functional and psychosocial impacts they document must, of necessity, affect the quality of life. While this assumption has been subject to critical scrutiny in medicine, this is not the case with dentistry. Consequently, exactly what is being measured by indexes of OH-QoL is somewhat unclear. Based on the debate between Gill and Feinstein and Guyatt and Cook, we outline a number of criteria by means of which the construct addressed by measures of OH-QoL may be assessed. These are concerned with how the measures were developed and validated. These criteria are then used to appraise five of the many measures that have been developed over the past 20 years--the GOHAI, OHIP, OIDP, COHQoL and OH-QoL. The main conclusion is that while all document the frequency of the functional and psychosocial impacts that emanate from oral disorders they do not unequivocally establish the meaning and significance of those impacts. Consequently, the claim that oral disorders affect the quality of life has yet to be clearly demonstrated. Verifying this claim requires further qualitative studies of the outcomes of oral disorders as perceived by patients and persons, and the concurrent use of measures that more explicitly address the issue of quality of life.