Tooth loss is a complex measure of oral disease: determinants and methodological considerations

Objectives: Counts of missing teeth or measures of incident tooth loss are gaining attention as a simple way to measure dental status in large population studies. We explore the meaning of these metrics and how missing teeth might influence other measures of dental status.

Methods: An observational study was performed in two contrasting adult populations. In total 62,522 adult participants were available with clinically assessed caries and periodontal indices from the Swedish arm of the Gene-Lifestyle Interactions and Dental Endpoints Study (GLIDE) and the Korea National Health and Nutrition Examination Survey (KNHANES) in the Republic of Korea. Longitudinal measures of tooth loss were available for 28,244 participants in GLIDE with median follow up of 10.6 years.

Results: In longitudinal analysis hazard for tooth loss was associated with baseline dental status (previous tooth loss, periodontal status and caries status) and socio-demographic variables (age, smoking status and highest educational level).

Analysis of cross-sectional data suggested that indices of caries exposure were not independent of periodontal status. The strength and direction of association varied between groups, even for measures specifically intended to avoid measuring tooth loss. Individuals with impaired periodontal health (community periodontal index (CPI) 3 or higher in any sextant) had higher standardized DFS (number of decayed and filled surfaces divided by total number of tooth surfaces) in GLIDE (incidence risk ratio (IRR) 1.05 (95% CI 1.04, 1.07), but lower standardized DFS in KNHANES (IRR 0.95 (0.92, 0.98)) than individuals with better periodontal health (CPI less than 3 in all sextants).