Methodological considerations for designing a community water fluoridation cessation study

The Impact of Water Fluoridation on Medicaid-Eligible Children and Adolescents in Alaska

Juneau, Alaska, ceased community water fluoridation (CWF) in 2007, and previous research found a substantial increase in dental caries-related procedures and treatment costs for children from low-income families in Juneau between 2003 and 2012. We collected comparable dental caries-related procedures and treatment cost data for the same years for children in Anchorage, Alaska, where CWF has been continuously maintained. This retrospective study analyzed all Medicaid dental claims records in two separate years for caries-related procedures and associated costs among children (aged 0 to 18 years) residing in Anchorage's 99502 zip code and compared these records to data from Juneau. We obtained descriptive statistics and conducted bivariate analyses and binomial logistic regression. Between 2003 and 2012, children in Anchorage experienced a nonsignificant modest decrease in the mean number of caries-related procedures and only small, statistically nonsignificant changes to the mean inflation-adjusted service costs of caries-related restorative care. The lack of significant change in child dental caries-related procedures and treatment costs in Anchorage between 2003 and 2012 contrasted with the substantial increase in caries-related procedures and treatment costs over the same period in Juneau. Our results are consistent with previous research that has demonstrated a significant protective effect of CWF against dental caries.

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.

Community water fluoridation exposure and dental caries experience in newly enrolled members of the Canadian Armed Forces 2006-2017

OBJECTIVES

This cross-sectional study examines the dental caries experience of new Canadian Armed Forces (CAF) members in relation to enrollment from municipalities with and without water fluoridation.

METHODS

The study population consisted of recruits who enrolled in the CAF between 2006 and 2017 with an enrollment address in municipalities with known fluoridation status (n = 24,552). Odontogram statistics from dental examinations were used to calculate the number of decayed, missing, and filled teeth (DMFT) and tooth surfaces (DMFS) for each recruit. The average difference between recruits from municipalities with and without fluoridation was determined using a linear regression model which adjusted for confounding by age and gender and allowed effect modification based on socio-economic status.

RESULTS

The average recruit was male, 24 years of age, with 5.6 DMFT and 11.6 DMFS. After adjusting for age and gender, recruits residing in municipalities with water fluoridation had lower DMFT by 0.67 (CI - 0.55, - 0.79) points and lower DMFS by 1.77 (- 1.46, - 2.09) points. When allowing for effect modification by median income quintile of the recruits' home census tract, the average reduction in DMFT and DMFS was similar in all income quintiles, with average reductions in DMFT ranging from 0.47 to 1.02 and average reductions in DMFS ranging from 1.33 to 2.70.

CONCLUSION

Residence in a municipality with water fluoridation was associated with reduced caries experience in a national sample of newly enrolled CAF members. The benefits of water fluoridation were uniform across neighbourhood income and military rank classes.

The impact of stopping or reducing the level of fluoride in public water supplies on dental fluorosis: a systematic review

OBJECTIVE

The increased availability of fluoride and concern over the impact of fluorosis, have led to guidance suggesting a decrease or cease in the optimal concentration of fluoride in water fluoridation schemes. To date there have been no systematic reviews looking at both impact of fluoride reduction and total cessation. This review aimed to examine the impact of stopping or reducing the level of fluoride in public water supplies on dental fluorosis.

CONTENT

Multiple databases were searched (MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and the Web of Science). Two reviewers independently screened sources, extracted data and assessed study quality. Results were synthesised qualitatively and quantitatively. The main outcome measure was the prevalence of dental fluorosis.

SUMMARY

Six studies of cross-sectional design were included. Two studies were scored as evidence level B (moderate) and the remaining four publications were evidence level C (poor). Meta-analysis indicated fluorosis prevalence was significantly decreased following either a reduction in the concentration of fluoride or cessation of adding fluoride to the water supply (OR:6.68; 95% CI:2.48 to 18.00).

OUTLOOK

The evidence suggests a significant decrease in the prevalence of fluorosis post cessation or reduction in the concentration of fluoride added to the water supply. However, this work demonstrates that when studies are subject to current expectations of methodological and experimental rigour, there is limited evidence with low methodological quality to determine the effect of stopping or reducing the concentration of fluoride in the water supply on dental fluorosis.