Background: Oral condition and number of teeth were investigated by questionnaire in the Japan Multi-Institutional Collaborative Cohort (J-MICC Study). The aim of the present study was to assess the validity of the tooth number measure by comparing the self-reported number of teeth with the number of teeth determined at clinical dental examination.
Methods: A self-administered questionnaire and dental examination were performed by 1275 participants of a company medical examination who requested dental check-up and 377 subjects of the J-MICC study. The validity of the tooth number measure was assessed by comparing the self-reported number of teeth with that determined at clinical examination. Spearman's rank correlation coefficient was calculated to quantitatively evaluate the validity.
Results: In males, the mean clinically-examined and self-reported numbers of teeth were 26.5 and 24.8 teeth, respectively. In females, the mean clinically-examined and self-reported numbers of teeth were 26.4 and 25.5 teeth, respectively. There was a tendency toward underestimation of the number of natural teeth by self-reporting. A significant correlation was observed between the clinically-examined and self-reported numbers of teeth in total (ρ = 0.69) and both males (ρ = 0.70) and females (ρ = 0.67).
Conclusions: The self-reported oral health variables were valid and reflected clinical status. Further revision of the question on the remaining tooth in the questionnaire improves the validity of self-reported number of teeth.
Keywords: Number of teeth; Questionnaire survey; Self-report; Validity.