University of Oulu

Similä, T., Nieminen, P., Virtanen, J. (2018) Validity of self-reported number of teeth in middle-aged Finnish adults: the Northern Finland Birth Cohort Study 1966. BMC Oral Health, 18 (1). doi:10.1186/s12903-018-0666-4

Validity of self-reported number of teeth in middle-aged Finnish adults : the Northern Finland Birth Cohort Study 1966

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Author: Similä, Toni1,2; Nieminen, Pentti3; Virtanen, Jorma2,4
Organizations: 1Research Unit of Oral Health Sciences, Faculty of Medicine, University of Oulu, P.O. Box 5000, 90014 Oulu, Finland
2Medical Research Center Oulu, Oulu University Hospital, P.O. Box 5000, 90029 Oulu, Finland
3Medical Informatics and Data Analysis Research Group, University of Oulu, P.O. Box 5000, 90014 Oulu, Finland
4Institute of Dentistry, University of Turku, 20014 Turku, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.7 MB)
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Language: English
Published: Springer Nature, 2018
Publish Date: 2019-03-08


Background: We examined the validity of self-reported number of teeth in middle-aged adults by using representative cohort data to compare corresponding self-reported and clinical values.

Methods: This validity study is part of the representative 46-year-old follow-up of the Northern Finland Birth Cohort 1966 (NFBC1966) Study. Mailed questionnaires (n= 5950) requested information on self-reported number of teeth and background variables (education, tooth brushing and smoking), while clinical oral health examinations (n= 1891) assessed the number of teeth (the ‘gold standard’). The main analyses compared the self-reported and clinical values for the number of teeth in 1669 participants. Scatterplot and Bland-Altman plot served for visual analyses, and alternative correlation coefficients (Pearson, Spearman, intraclass) for numerical comparisons separately for men and women, with stratification according to background variables.

Results: The clinical assessment revealed that the mean value for the number of teeth was 27.46 (SD = 2.38), while the corresponding value based on self-reported information was 27.48 (SD = 2.78). According to the Bland-Altman plot, the mean difference between the clinical and self-reported values was − 0.02 (95% limits of agreement, LoA: − 3.37 to 3.32). The observed ranges of intraclass correlation coefficients (ICC) among men and women were 0.72 to 0.95 and 0.72 to 0.85, respectively, depending on the background variables.

Conclusions: Self-reported number of teeth in middle-aged Finnish adults agreed closely with the corresponding clinical measure.

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Series: BMC oral health
ISSN: 1472-6831
ISSN-E: 1472-6831
ISSN-L: 1472-6831
Volume: 18
Article number: 210
DOI: 10.1186/s12903-018-0666-4
Type of Publication: A1 Journal article – refereed
Field of Science: 112 Statistics and probability
313 Dentistry
Copyright information: © The Author(s). 2018 Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.