Mortality and morbidity are no longer the only relevant measures of success for preventive and curative health care, because quality of life and the value that people place on their state of health play to an ever greater extent a decisive role in the decision-making process concerning preventive and curative health care. The aim of the academic discipline ‘quality of life’ (QoL) is to study the relationship between people’s quality of life and their health and to make it possible to measure that relationship. It is important to identify the relevant determining factors and to develop cost-effective, evidence-based interventions to secure and improve the quality of life. It has recently been proposed that quality of life should be considered as a model instead of a concept. Problems of definition are part of the past and the issue of considerable nuancing in existing measurement instruments is giving way to the theoretical modelling of the determinants of QoL.

Quality of life is a subjective evaluation/appreciation of the degree to which someone is satisfied with life in general. This subjective evaluation is not necessarily consistent. Factors determining one’s quality of life may differ interpersonally, but also intrapersonally. Quality of life is a dynamic concept which cannot easily be expressed mathematically.

The phrase ‘quality of life’ is actually misleading. The designation suggests that the issue has to do with 1 quality, whereas in fact more qualities of life are indicated. Four of these qualities are: 1. the ‘livability’ of the surroundings, 2. the ‘life-abilities’ of the individual, 3. the ‘utility of life’ and 4. the subjective ‘satisfaction’ with a person’s own life. The various qualities cannot meaningfully be collected together in an index. The most comprehensive measure of quality of life is how long and happily a person lives. The relationship between that and oral health has still hardly been studied.

A Dutch-language version of the Oral Health Impact Profile, a questionnaire by means of which the impact of oral health on the quality of life of patients can be determined, was developed and subsequently psychometrically tested among a group of patients with complaints concerning missing dentition or their dentures. In addition, a shortened version of this so-called OHIP-NL49, the OHIP-NL14, was psychometrically tested among a group of patients with temporomandibular disorders. The psychometrical characteristics of both the OHIP-NL49 and the OHIP-NL14 were very good: both the reliability and the validity were high. The conclusion was, that the OHIP-NL49 and the OHIP-NL14 are well suited for determining the impact of oral health on the quality of life.

The methods uses most often for developing and analyzing questionnaires, such as the explorative factor analysis and Cronbach’s alpha, presume that psychological constructs are latent (imperceptible) and that there is a reflective-measurement model with the underlying assumption of local independence. Local independence means that the latent variable explains why the variables observed are related. Many questionnaires for measuring oral health-related quality of life are analyzed as if they were based on a reflective-measurement model assuming local independence. This assumption requires these questionnaires to contain solely items reflecting instead of determining oral health-related quality of life. The tenability of this assumption is questionable.

In a comparative study, the influence of oral health on the quality of life was investigated for people with temporomandibular pain, people with tooth wear and people with complete dentures. To this end, the study made use of the Oral Health Impact Profile. Both the total score and the scores on 4 of the 7 domains of the Oral Health Impact Profile were significantly higher in the research group with temporomandibular pain than in the research groups with tooth wear and complete dentures. These results suggest that among people with temporomandibular pain the influence of oral health on the quality of life is more negative than among people with tooth wear and among people with complete dentures. This result can probably be linked with the general finding that patients with temporomandibular pain bear a relatively high psycho-social burden.

One of the options for treating a patient who has lost a tooth is an implantsupported prosthetic construction. Implant therapy has shown to be a predictable and reliable treatment and the implant survival rate is high. The influence this treatment has on the quality of the patient’s life deserves more attention. The overall tendency is that implant treatments have a favourable effect on quality of life.

This study assessed the impact on happiness and quality of life of the cosmetic treatment of frontal teeth. This was compared with the impact of a restorative, not primarily cosmetic, treatment in the (pre)molar region on happiness and quality of life. The hypothesis that a cosmetic dental treatment makes a person happier or improves the quality of one’s life was not supported by the results of the present study. In fact, oral health-related quality of life appeared to decline after the dental cosmetic treatment. Further research is needed to assess whether the results of the present study can be replicated in a larger sample and how the findings can be explained.

Caries is the most prevalent oral disease in children. The majority of caries in toddlers remains untreated, with toothaches as a consequence. Although toothache is an important determinant of the quality of life, prevalence data on toothaches hardly exist. Research results indicate that children’s quality of life improves after caries treatment. The question remains which type of treatment is preferable. To address this question, evidence from randomized controlled clinical trials on various treatment methods is needed.

In recent years, research on the influence of oral health on quality of life among children has become increasingly popular. Half of the children and adolescents will have had moments of diminished oral health and that can lead to functional problems, pain and decreased quality of life. While measuring oral health-related quality of life of children, reports of parents are frequently used as a proxy. Diminished oral health not only has an impact on the child’s quality of life, but also on that of his family members. Results from studies on oral health-related quality of life in children may be used as the basis for useful guidance for parents and children on improving oral health and quality of life.

As part of a large-scale oral health/epidemiological research project among adults in ’s-Hertogenbosch, the impact of a number of clinical and demographic variables on quality of life was studied. Quality of life was measured with the help of the Dutch version of the abridged Oral Health Impact Profile. Half of those questioned appeared to experience no negative impact at all from their oral health on their quality of life. Those with poor oral health and a low level of education were especially likely to have a high score on the Oral Health Impact Profile. The average score of 2.8 was lower than the revealed averages in research in Australia (7), England (5) and New Zealand (8). It was concluded that oral health appears to have an impact on the quality of life of a population although the correlational research format did not permit causational judgements.