Objectives: To study the agreement between self-reported dental conditions and clinical findings in an adult population (20-84 years of age), and thus evaluate questionnaires as a tool in epidemiological studies of oral health, in general, and periodontal health, in particular.
Material and methods: A questionnaire was sent to 900 randomly selected subjects in the age groups 20-29, 50-59 and 75-84 years. Of these, 723 subjects (81.0%) answered the questionnaire and 20% of them underwent a clinical examination.
Results: As regards the remaining teeth, there was a mean difference of 1.4 teeth between the number indicated in the questionnaire and that found on the clinical examination. This difference was most marked in the older subjects. Eight of the nine subjects with removable dentures reported in their answers that they had removable dentures. Periodontal variables--we found significantly more subjects with pathological gingival pockets among those who stated that they had pockets than among those who answered that they did not (P = 0.01; chi-square independent test). Gingival bleeding was common in those who answered 'Yes' than in those who answered 'No' to the question concerning bleeding gums. This difference was significant (P = 0.05; chi-square independent test) in the three age groups. However, there was no correlation between the questionnaires and the clinical examination concerning tooth mobility.
Conclusion: Questionnaires concerning oral status are valid concerning the number of remaining teeth and use of removable dentures. They are less reliable about specific periodontal variables, but can still become a valuable tool for epidemiological studies of periodontal health.