Currently, there appears to be no consensus to define Health-Related Quality of Life (HRQoL). HRQoL is dynamic, fluctuating and is related to the physical, mental and social (functional and psychosocial) aspects of an individual’s well-being. Although there are generally satisfactory ways of defining and measuring the frequency and severity of diseases, this may not be the case in so far as the measurement of well-being and quality of life is concerned. Similar problems have to be confronted when trying to define Oral Health-Related Quality of Life (OHRQoL) issues. OHRQoL can be considered as the scientific expression of that part of a person’s well-being that is affected by his/her oral health. Therefore, OHRQoL may provide a new perspective when looking at a patient, by measuring treatment efficacy in terms of patient satisfaction, in addition to the more traditional objective data measured in patients’ mouths such as remineralisation of teeth or bleeding indices. The assessment of OHRQoL may therefore help define the assessment needs to dentists, patients and commissioners/planners of health-care provision.

Why is it difficult to evaluate OHRQoL?

OHRQoL deals with conditions that vary in intensity and importance. These conditions may be life-threatening (e.g. oral cancers) or not, progressing (caries, periodontitis, etc.) or not, dealing with aesthetics (staining in anterior teeth such as molar–incisor hypomineralisation (MIH)) or pain (pulpitis, MIH in posterior teeth, etc.). OHRQoL is highly subjective and has to be assessed within the framework of patients’ conditions, sociocultural environments and own experiences and states of mind: because OHRQoL is related to daily life and is unique to each individual, even patients with severe conditions can report having good quality of life. Furthermore, Quality of Life is by itself multi-faceted, showing variation over time for each individual. OHRQoL should therefore be assessed longitudinally to take into account changes over time, using versatile tools.

How to assess OHRQoL?

The main difficulty is to reflect patients’ concerns. This means having relevant questions with well-defined items and being able to analyse answers in a good way. Many limitations can be found to the current validation testing, including relevance of the questions, validity and sensitivity to change, risk of misinterpretations (role of the ethnocultural environment), problems of translation of English questionnaires and difficulty to interpret the significance of a psychometric measurement when reported simply as a numerical score or a mean [1, 2]. This latter point is of importance since the same score can be obtained from people answering in a different way to a majority of questions. Finally, patient-based outcome measures (as named by Fitzpatrick et al. [3]) should provide the opportunity to measure the extent or intensity of the changes in OHRQoL.

Various psychometric instruments have also been used to measure OHRQoL (Tables 1 and 2) [1, 4]. These are based on different criteria that enable them to be more or less patient- or expert-centred. Some are generic (OHIPFootnote 1-49, OHIP-14, OIDP, OH-QoL, SF-36Footnote 2) and can be considered as core indicators; others are adapted to specific conditions/domains (Orthognathic QOL Questionnaire, SOOQ for orthodontic surgery, OHIP-aesthetic,Footnote 3 OHRQOL for Dental Hygiene) or populations (COHQoL and Child-OIDP for children, GOHAI for elderly people, etc.).

Table 1 Conceptual and structural basis of psychometric instruments used in dentistry (adapted from Brondani and McEntee [1])
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Table 2 Oral health outcome measures developed before 2007 (adapted from Locker and Allen [4])
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The OHIP, also called OHIP-49, is the most widely used, and this has enabled investigators to modify forms that can be subsequently adapted to populations or conditions. The initial 49-question form was constructed to assess the ‘social impact’ of oral disorders [5]. Each of the set of 49 statements represented one of seven domains: It is mainly expert-centred and constructed to select items according to their fit with a conceptual framework rather than on the basis of their importance to the patients from whom they were derived [4]. A shorter version of OHIP restricted to 14 items (OHIP-14) was later proposed [6]. One major question is to know if we need to use either a generic questionnaire, an adapted form of a generic questionnaire or to construct a new questionnaire specific to the population or condition to be studied. Constructing or using one of these specific questionnaires may lead to many questions, for example, (1) Is it made specifically for the purpose of research or for clinical practice? or (2) How to adapt each questionnaire to local languages and cultures? This may subsequently lead us to consider the impact of dentin hypersensitivity (DHS) or exposed cervical dentin (ECD) on OHRQoL of those individuals being assessed.

DHS/ECD and OHRQoL: what is known and where are the problems?

Very few studies have been devoted to this aspect of DHS/ECD as recently shown [7], with only two papers written in English specifically dedicated to the evaluation of OHQoL in DHS/ECD patients. One paper provided results using a generic questionnaire [8] and the second paper constructed a specific questionnaire to evaluate OHQoL in DHS/ECD patients but provided no epidemiological results [9]. These studies are more extensively described in an accompanying paper [7]. In the future, studies using validated questionnaires specifically constructed to evaluate the impact of the condition on OHQoL should be employed. These questionnaires should be patient-centred and derived from interviews with patients who are expected to complete the questionnaire [4, 10]. Furthermore, if these studies also attempt to evaluate the efficacy of desensitising agents in reducing DHS/ECD and its subsequent impact on OHQoL, then it is imperative that the condition should be clearly diagnosed by trained and calibrated dentists experienced in conducting clinical studies using recognised and accepted clinical criteria for the evaluation of DHS/ECD. Due to the cultural and language differences between countries, there is also a need of norm or reference value(s) for each population to be studied. For example, when constructing a questionnaire for a non-English-speaking population, the questionnaire should be initially written in English, then translated by two people of the designated native (foreign) language and subsequently translated back into English by two native English-speaking people to identify any potential issues that may have arisen from the translation. Finally, as indicated above, any future study attempting to evaluate the efficacy of a desensitising agent in reducing DHS/ECD and its subsequent impact on OHQoL should be conducted by experienced and calibrated examiners using established guidelines for conducting DHS/ECD clinical studies. Such studies should also be based on a randomised clinical study design and include both placebo or control groups.

What are the recommendations for daily dental practice?

Patients suffering from DHS/ECD have been reported to have a significantly impaired OHRQoL; this may however be improved following treatment with a desensitising agent as reported by several authors. It is therefore of the upmost importance that the use of the OHRQoL as a quality control tool in the dental office be established in robust clinical studies. Furthermore, because of its ability to reflect a patient’s satisfaction with any proposed treatment, it may prove to be a valuable asset for practitioners when assessing their patients’ quality of life before, during and after treatment of various clinical conditions such as DHS/ECD.