Background: The aim of this study was to confirm whether the level of lifetime fluoridation exposure is associated with lower dental caries experience in younger adults (15-46 years).

Methods: Data of the cohort born between 1960 and 1990 residing outside Australia's capital cities from the 2004-2006 Australian National Survey of Adult Oral Health were analysed. Residential history questionnaires were used to determine the percentage of each person's lifetime exposure to fluoridated water (<50%/50+%). Examiners recorded decayed, missing, and filled permanent teeth (DMFT). Socio-demographic variables, periodontal risk factors, and access to dental care were included in multivariable least-squares regression models.

Results: In bivariate analysis, the higher level of fluoridation category had significantly lower DMFT (mean 6.01 [SE = 0.62]) than the lower level of fluoridation group (9.14 [SE = 0.73] p < 0.01) and lower numbers of filled teeth (4.08 [SE = 0.43], 7.06 [SE = 0.62], p < 0.01). In multivariate analysis, the higher number of full-time equivalent dentists per 100 000 people was associated with a lower mean number of missing teeth (regression coefficient estimate = –1.75, p = 0.03), and the higher level of water fluoridation with a lower mean DMFT (–2.45, p < 0.01) and mean number of filled teeth (–2.52, p < 0.01)..

Conclusions: The higher level of lifetime fluoridation exposure was associated with substantially lower caries experience in younger rural adults, largely due to a lower number of filled teeth.