Small-area contextual effects on children's dental caries in Alberta: a multilevel analysis

Fluoridation cessation and oral health equity: a 7-year post-cessation study of Grade 2 schoolchildren in Alberta, Canada

OBJECTIVE

Community water fluoridation, because of its universal scope and passive mechanism of uptake, is one component of a multifaceted approach to promoting equity in dental health. The objective of this study was to examine social inequities in children's dental health in the Canadian cities of Calgary (fluoridation cessation in 2011) and Edmonton (still fluoridated).

METHODS

We analyzed data from surveys of population-based samples of Grade 2 (approx. age 7) children in Calgary in 2009/2010 (pre-cessation; n=557) and in both Calgary and Edmonton in 2013/2014 (Calgary, n=3230; Edmonton, n=2304) and 2018/2019 (Calgary, n=2649; Edmonton, n=2600) (post-cessation). We estimated associations between several socioeconomic indicators and dental caries indicators (i.e., dental caries experience [deft, DMFT] and untreated decay in two or more teeth [untreated decay]) using zero-inflated Poisson, binary logistic regression, and the concentration index of inequality. We compared those associations over time (between survey waves) and between cities at post-cessation.

RESULTS

Persistent social inequities in deft and untreated decay were evident; for example, having no dental insurance was significantly associated with higher odds of untreated decay across city and survey wave. In most (but not all) cases, differences between cities and survey waves were consistent with an adverse effect of fluoridation cessation on dental health inequities. For example, the association between no dental insurance and higher odds of untreated decay in Calgary was greater in 2018/2019 (later post-cessation) than in 2009/2010 (pre-cessation; odds ratio [OR] for comparison of coefficients = 1.89 [1.36-2.63], p<0.001) and 2013/2014 (early post-cessation; OR for comparison of coefficients = 1.67 [1.22-2.28], p=0.001); that same association in 2018/2019 was greater in Calgary (fluoridation cessation) than in Edmonton (still fluoridated) (OR for comparison of coefficients = 1.44 [1.03-2.02], p=0.033).

CONCLUSION

Social inequities in dental caries were present in both Calgary and Edmonton. Those inequities tended to be worse in Calgary where fluoridation was ceased. Our findings may be relevant to other settings where income inequality is high, dental services are costly, and dental public health infrastructure is limited.

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.