Fluoridation Cessation and Children's Dental Caries: A 7-year Follow-up Evaluation of Grade 2 Schoolchildren in Calgary and Edmonton, Canada

Objectives: We examined the effect of fluoridation cessation on children's dental caries experience in the Canadian cities of Calgary (cessation in 2011) and Edmonton (still fluoridated).

Methods: We used a pre-post cross-sectional design with comparison group. We studied Grade 2 schoolchildren (approximately 7 years old) 7-8 years after fluoridation cessation in Calgary, thus capturing children born after cessation occurred. Data collection included a dental examination conducted in school by calibrated dental hygienists, a questionnaire completed by parents, and fingernail clippings for a small subsample. Our overall analytic approach was twofold. We first examined differences in dental caries experience (deft and DMFT, and smooth surface caries based on defs and DMFS) between Calgary and Edmonton and over time (comparing 2018/2019 data to pre-cessation and early post-cessation surveys in our setting). Second, we evaluated whether differences were likely to reflect fluoridation cessation in Calgary, rather than other factors.

Results: The prevalence of caries in the primary dentition was significantly higher (P < .05) in Calgary (fluoridation cessation) than in Edmonton (still fluoridated). For example, crude deft prevalence in 2018/2019 was 64.8% (95% CI 62.3-67.3), n = 2649 in Calgary and 55.1% (95% CI 52.3-57.8), n = 2600 in Edmonton. These differences were consistent and robust: they persisted with adjustment for potential confounders and in the subset of respondents who were lifelong residents and reported usually drinking tap water; they had widened over time since cessation; and they were corroborated by assessments of dental fluorosis and estimates of total fluoride intake from fingernail clippings. Findings for permanent teeth were less consistent, which likely reflects that 7-year-olds have not had the time to accumulate enough permanent dentition caries experience for differences to have become apparent.

Conclusions: Our findings are consistent with an adverse impact of fluoridation cessation on children's dental health in Calgary and point to the need for universal, publicly funded prevention activities-including but not limited to fluoridation.