Association Between Water Fluoridation and Income-Related Dental Caries of US Children and Adolescents

Epigenome-wide association study of fluoride exposure during early adolescence and DNA methylation among U.S. children

Exposure to fluoride in early childhood has been associated with altered cognition, intelligence, attention, and neurobehavior. Fluoride-related neurodevelopment effects have been shown to vary by sex and very little is known about the mechanistic processes involved. There is limited research on how fluoride exposure impacts the epigenome, potentially leading to changes in DNA methylation of specific genes regulating key developmental processes. In the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), urine samples were analyzed using a microdiffusion method to determine childhood urinary fluoride adjusted for specific gravity (CUFsg) concentrations. Whole blood DNA methylation was assessed using the Infinium MethylationEPIC BeadChip 850 k Array. In a cross-sectional analysis, we interrogated epigenome-wide DNA methylation at 775,141 CpG loci across the methylome in relation to CUFsg concentrations in 272 early adolescents at age 12 years. Among all participants, higher concentrations of CUF were associated with differential methylation of one CpG (p < 6 × 10-8) located in the gene body of GBF1 (cg25435255). Among females, higher concentrations of CUFsg were associated with differential methylation of 7 CpGs; only three CpGs were differentially methylated among males with no overlap of significant CpGs observed among females. Secondary analyses revealed several differentially methylated regions (DMRs) and CpG loci mapping to genes with key roles in psychiatric outcomes, social interaction, and cognition, as well as immunologic and metabolic phenotypes. While fluoride exposure may impact the epigenome during early adolescence, the functional consequences of these changes are unclear warranting further investigation.

Cross-sectional study of association between caries and fluoridated water among third-grade students in Pennsylvania

BACKGROUND

Caries is the most common chronic disease among children. In Pennsylvania, a comprehensive oral health Basic Screening Survey and assessment of the association between caries and community water fluoridation (CWF) among children have not been conducted.

METHODS

From 2021 through 2022, the first Basic Screening Survey was conducted among third-grade students in Pennsylvania. Oral health and demographic data were collected. CWF data were provided by the Pennsylvania Department of Environmental Protection. The relative risk of developing caries in association with CWF was assessed using the GENMOD procedure in SAS, Version 9.4 (SAS Institute) in this cross-sectional study.

RESULTS

Caries prevalence was 59.7% among 4,120 screened students. Participation in the free or reduced lunch program and CWF were each significantly associated with risk of developing caries after adjustment for age, sex, and race and ethnicity. The risk of developing caries was 33% higher among students who participated in the free or reduced lunch program than those who did not participate (relative risk, 1.33; 95% CI, 1.24 to 1.42). Students with the highest CWF coverage had a nearly 16% lower risk of developing caries than those without CWF coverage (relative risk, 0.84; 95% CI, 0.75 to 0.94).

CONCLUSIONS

CWF was significantly associated with a reduced risk of developing caries. Efforts are needed to increase CWF coverage, along with promotion of oral health education and healthy dietary habits among Pennsylvania children.

PRACTICAL IMPLICATIONS

Increasing CWF coverage will reduce caries burden among Pennsylvania children. Although Pennsylvania has no state laws to regulate CWF, these findings are persuasive for local municipalities to consider expanding CWF coverage.

Effect of bottled fluoridated water to prevent dental caries in primary teeth: study protocol for a phase 2 parallel-group 3.5-year randomized controlled clinical trial (waterBEST)

BACKGROUND

Fluoridation of public water systems is known as a safe and effective strategy for preventing dental caries based on evidence from non-randomized studies. Yet 110 million Americans do not have access to a fluoridated public water system and many others do not drink tap water. This article describes the study protocol for the first randomized controlled trial (RCT) of fluoridated water that assesses its potential dental caries preventive efficacy when delivered in bottles.

METHODS

waterBEST is a phase 2b proof-of-concept, randomized, quadruple-masked, placebo-controlled, parallel-group trial designed to estimate the potential efficacy of fluoridated versus non-fluoridated bottled water to prevent dental caries incidence in the first 4 years of life. Two hundred children living in eastern North Carolina, USA, and aged 2-6 months at screening are being allocated at random in a 1:1 ratio to receive fluoridated (0.7 mg/L F) or non-fluoridated bottled water sourced from two local public water systems. Throughout the 3.5-year intervention, study water is delivered monthly in 5-gallon bottles to each child's home with instructions to use it whenever the child consumes water as a beverage or in food preparation. Parents are interviewed quarterly to monitor children's water consumption and health. At annual visits, the presence of dental caries is evaluated with a dental screening examination. Clippings from fingernails and toenails are collected to quantify fluoride content as a biomarker of total fluoride intake. The primary endpoint is the number of primary tooth surfaces decayed, missing, or filled due to dental caries measured by the study dentist near the time of the child's fourth birthday. Tooth decay is assessed at the threshold of macroscopic enamel loss. For the primary aim, a least-squares, generalized linear model will estimate efficacy and its one-tailed, upper 80% confidence limit.

DISCUSSION

waterBEST is the first evaluation of a randomized intervention of fluoridated drinking water in bottles to prevent dental caries in the primary dentition. This innovative method of delivering fluoridated water has the potential to prevent early childhood caries in a large segment of the US population that currently does not benefit from fluoridated public water.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04893681. Registered on March 2022. Last update posted on 10 October 2023. https://clinicaltrials.gov/study/NCT04893681?cond=Dental%20Caries%20in%20Children&term=fluoride&locStr=North%20Carolina,%20USA&country=United%20States&state=North%20Carolina&distance=50&rank=1.

Effect of bottled fluoridated water to prevent dental caries in primary teeth: study protocol for a phase 2 parallel group 3.5-year randomized controlled clinical trial (waterBEST)

Background

Fluoridation of public water systems is known as a safe and effective strategy for preventing dental caries based on evidence from non-randomized studies. Yet 110 million Americans do not have access to a fluoridated public water system and many others do not drink tap water. This article describes the study protocol for the first randomized controlled trial (RCT) of fluoridated water that assesses its potential dental caries preventive efficacy when delivered in bottles.

Methods

waterBEST is a phase 2b proof-of-concept, randomized, quadruple-masked, placebo controlled, parallel group, trial designed to estimate the potential efficacy of fluoridated versus non-fluoridated bottled water to prevent dental caries incidence in the first four years of life. Two hundred children living in eastern North Carolina, USA, and aged 2-6 months at screening are being allocated at random in a 1:1 ratio to receive fluoridated (0.7 mg/L F) or non-fluoridated bottled water sourced from two local public water systems. Throughout the 3.5-year intervention, study water is delivered monthly in 5-gallon bottles to each child's home with instructions to use it whenever the child consumes water as a beverage or in food preparation. Parents are interviewed quarterly to monitor children's water consumption and health. At annual visits, the presence of dental caries is evaluated with a dental screening examination. Clippings from fingernails and toenails are collected to quantify fluoride content as a biomarker of total fluoride intake. The primary endpoint is the number of primary tooth surfaces decayed, missing, or filled due to dental caries measured by the study dentist near the time of the child's fourth birthday. Tooth decay is assessed at the threshold of macroscopic enamel loss. For the primary aim, a least-squares, generalized linear model will estimate efficacy and its one-tailed, upper 80% confidence limit.

Discussion

waterBEST is the first evaluation of a randomized intervention of fluoridated drinking water in bottles to prevent dental caries in the primary dentition. This innovative method of delivering fluoridated water has potential to prevent early childhood caries in a large segment of the U.S. population that currently does not benefit from fluoridated public water.

Regional and racial/ethnic inequalities in public drinking water fluoride concentrations across the US

BACKGROUND

Although the US Centers for Disease Control and Prevention (CDC) considers fluoridation of community water systems (CWSs) to be a major public health achievement responsible for reducing dental disease, recent epidemiologic evidence suggests that chronic exposure to population-relevant levels of fluoride may also be associated with adverse child neurodevelopmental outcomes. To our knowledge, a nationally representative database of CWS fluoride concentration estimates that can be readily linked to US epidemiologic cohorts for further study is not publicly available. Our objectives were to evaluate broad regional and sociodemographic inequalities in CWS fluoride concentrations across the US, and to determine if county-level racial/ethnic composition was associated with county-level CWS fluoride.

METHODS

We generated CWS-level (N = 32,495) and population weighted county-level (N = 2152) fluoride concentration estimates using over 250,000 routine compliance monitoring records collected from the US Environmental Protection Agency's (EPA) Third Six Year Review (2006-2011). We compared CWS-level fluoride distributions across subgroups including region, population size served, and county sociodemographic characteristics. In county-level spatial error models, we also evaluated geometric mean ratios (GMRs) of CWS fluoride per 10% higher proportion of residents belonging to a given racial/ethnic subgroup.

RESULTS

4.5% of CWSs (serving >2.9 million residents) reported mean 2006-2011 fluoride concentrations ≥1500 µg/L (the World Health Organization's guideline for drinking water quality). Arithmetic mean, 90th, and 95th percentile contaminant concentrations were greatest in CWSs reliant on groundwater, located in the Southwest and Eastern Midwest, and serving Semi-Urban, Hispanic communities. In fully adjusted spatial error models, the GMR (95% CI) of CWS fluoride per a 10% higher proportion of county residents that were Hispanic/Latino was 1.16 (1.10, 1.23).

IMPACT STATEMENT

We find that over 2.9 million US residents are served by public water systems with average fluoride concentrations exceeding the World Health Organization's guidance limit. We also find significant inequalities in community water system fluoride concentration estimates (2006-2011) across the US, especially for Hispanic/Latino communities who also experience elevated arsenic and uranium in regulated public drinking water systems. Our fluoride estimates can be leveraged in future epidemiologic studies to assess the potential association between chronic fluoride exposure and related adverse outcomes.

Family income modifies the association between frequent sugar intake and dental caries

AIM

The aim of this cross-sectional study was to investigate whether family income modifies associations between dental caries and sex, age, mother's education, type of preschool, sugar intake, and toothbrushing.

BACKGROUND

Dental caries is a multifactorial dyanamic disease primarily mediated by biofilm and sugar.

DESIGN

A randomly selected sample of 308 Brazilian preschool children aged 1-3 years underwent a clinical oral examination for the assessment of moderate/extensive dental caries using codes 3-6 of the International Caries Detection and Assessment System. Mothers were asked to fill out a form addressing the child's demographic and socioeconomic characteristics as well as the frequency of sugar intake. Statistical analysis involved descriptive statistics, the chi-squared test, and Poisson regression models.

RESULTS

The prevalence of moderate/extensive dental caries was 42.5%. The adjusted model revealed that within low-income families (<2 times the monthly minimum wage), the prevalence of dental caries was higher among children with a high frequency of sugar intake (≥ twice per day) than in those with a low frequency of sugar intake (< twice a day) (RR = 1.79; CI: 1.38-2.33). In families with higher income (≥2 times the monthly wage), no significant association between sugar intake and dental caries was, however, found.

CONCLUSIONS

In conclusion, monthly family income can modify the association between the high frequency of sugar intake and dental caries.

Preventive Oral Health in Pediatric Primary Care

Oral health is an integral part of every child's overall wellness and affects their development, family, and social life, as well as school performance; it should be addressed at every well-child visit. Tooth decay continues to be the most prevalent yet preventable chronic disease of childhood; it leads to unnecessary pain, infections, poor academic performance, and frequent school absences and adds an unnecessary financial burden to the health care system. Despite improvements in oral health, disparities continue to exist for children from minority backgrounds and lower socioeconomic status. As primary care providers for children, it is important to understand factors that lead to oral disease and be able to anticipate, treat, and, most important, prevent oral disease in children early in their development. [Pediatr Ann. 2022;51(12):e474-e479.].

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.

Impact of water fluoridation on dental caries decline across racial and income subgroups of Brazilian adolescents

OBJECTIVES

The aim of this study was to assess the impact of community water fluoridation (CWF) on differences in dental caries decline across racial and socioeconomic subgroups of Brazilian adolescents.

METHODS

Two nationwide Brazilian population-based oral health surveys were used (Brazilian Oral Health Survey 2003 and 2010). In total, 7,198 adolescents from 15 years to 19 years old living in 50 cities investigated in both surveys were included. The mean numbers of untreated decayed teeth (DT) according to racial (Whites vs. Browns/Blacks) and socioeconomic subgroups (at or above the minimum wage per capita vs. under) were analysed. Difference-in-differences negative binomial regressions were adjusted by schooling, age, and sex. Decayed, missing, and filled teeth and DT prevalence, calculated as a categorical variable, were used in sensitivity analyses.

RESULTS

The adjusted difference of reduction in DT was similar across socioeconomic subgroups (β=-0.05; 95% confidence interval [CI], -0.45 to 0.35) and favoured, but not to a significant degree, Whites (β=-0.34; 95% CI, -0.74 to 0.04) compared to Brown/Blacks in fluoridated areas. In non-fluoridated areas, significant differences were observed in the mean number of DT, favouring the higher socioeconomic subgroup (β=-0.26; 95% CI, -0.53 to -0.01) and Whites (β=-0.40; 95% CI, -0.69 to -0.11) in relation to their counterparts. The sensitivity analyses confirmed the findings.

CONCLUSIONS

The similar reduction in DT across income subgroups suggests that CWF has had a beneficial effect on tackling income inequalities in dental caries within a 7-year timeframe.

Seeking community water fluoridation information on state health department websites

Community water fluoridation (CWF) is the most effective and equitable approach to preventing dental caries (tooth decay). Yet millions of Americans, especially those at highest risk of caries, do not know what CWF is or its preventive benefits. State health departments are responsible for educating their respective populations. Thus, this study assessed health department websites (N = 50) to determine if CWF content existed, the ease of finding it, and if it was written in plain language and for a consumer audience. We used the web component of the HLE2: The Health Literacy Environment of Hospitals and Health Centers (HLE2) to assess how easy or difficult it was to the navigate a website and find information. Forty-one websites had CWF information; 37 states had content written for a consumer audience. HLE2 scores ranged from 0 to 54 points (60 possible). Only five states had websites with a HLE2 score of 50 or higher. SHDs with higher HLE2 scores were easy to navigate and their content was written for a consumer audience. Study findings suggest most SHDs should improve their website’s CWF content and its accessibility to better promote the role of fluoridated water in preventing dental caries.

Excess Risk of Dental Caries from Higher Free Sugars Intake Combined with Low Exposure to Water Fluoridation

The study aimed to quantify the excess risk of interaction between high free sugars (sugars) intake and lack of exposure to water fluoridation on child dental caries. Data from the Australian National Child Oral Health Study, a population-based survey of 24,664 children aged 5 to 14 y, were collected using parental questionnaires and oral epidemiological examinations by trained examiners. Information on socioeconomic status, dental health behaviors, and dental service use was used as covariates. The number of servings of sugars-containing foods and drinks consumed in a usual day was assessed as the main exposure, categorized into 5 groups. Residential history was used to calculate lifetime exposure to fluoridated water (LEFW), categorized as low (<25%), medium (25% to <75%), or high (75%-100%). Caries prevalence (dmfs/DMFS >0) and experience (dmfs/DMFS) in the primary (ages 5-10 y) and permanent (ages 8-14 y) dentitions were the main dependent variables. The association of sugars intake and LEFW with each outcome was estimated in multivariable log-Poisson regression models with robust standard error estimation, adjusted for covariates. The relative excess risk due to interaction (RERI) between sugars intake and LEFW was estimated. Strong positive gradients in all outcomes were observed across sugars intake groups. Relative to the lowest intake group, the 3 highest intake groups had significantly higher adjusted prevalence ratios for having caries and higher adjusted mean ratios of caries experience in both dentitions, after controlling for all covariates. LEFW strongly and consistently attenuated the effects of all levels of sugars intake on the outcomes. RERI estimates indicated that a combination of lack of exposure to fluoridated water and high sugars intake resulted in greater excess risk of primary and permanent caries than if there was no interaction. Evidently, children with high sugars intakes and low exposure to water fluoridation are at disproportionately higher risk of dental caries.

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.

Advancing oral health policy through persuasive messaging and effective research measures

Oral health is often excluded from broad health policy discussions, addressed only in a policy silo. There is a paucity of research to guide policymaking as it relates to oral health. In response, AcademyHealth's Oral Health Interest Group organized a meeting during the 2019 AcademyHealth Annual Research Meeting to promote transdisciplinary dialog on the current state of oral health policy and the steps necessary to improve the oral health of Americans. This article summarizes the two main themes that emerged from the proceedings of the Oral Health Interest Group meeting: a) recommendations for advocating the inclusion of oral health in policy discussions and b) critical research topics and measures needed for effective oral health policies in the future.

Effects of Community Water Fluoridation on Dental Caries Disparities in Adolescents

Despite improvements in the prevalence of dental caries, disparities are still observed globally and in the U.S. This study examined whether community water fluoridation (CWF) reduced dental caries disparities in permanent teeth of 10- to 19-year-old schoolchildren in North Carolina. We used cross-sectional data representing K-12 schoolchildren in North Carolina (NC) public schools. A poisson regression model was used to determine whether the association between children’s parental educational attainment and the prevalence of dental caries of children differed by children’s lifetime CWF exposure. We analyzed data on 2075 students. Among the children without any CWF exposure in their life, statistically significant caries disparities by parental educational attainment were observed. Compared to the children of parents with more than high school education, the relative risk for those with a parent with a high school education was 1.16 (95% CI = 1.01, 1.33) and those with less than a high school education was 1.27 (95% CI = 1.02, 1.60). In contrast, these disparities were not observed among children exposed to CWF throughout their lives. Socioeconomic disparities in dental caries were not observed among 10–19-year-old schoolchildren with lifetime CWF exposure. CWF seemed to reduce dental caries disparities.

Emulation of Community Water Fluoridation Coverage Across US Counties

INTRODUCTION

Expansion of community water fluoridation has stalled in the United States, leaving 115 million Americans without fluoridated drinking water.

OBJECTIVE

This study used spatial regression methods to assess contributions of supply-side factors (neighboring counties' fluoridation coverage) and demand-side factors (health literacy, education, and population density of the local county) in predicting the extent of fluoridation in US counties.

METHODS

For this cross-sectional ecological analysis, data from the 2014 Water Fluoridation Reporting System for all 3,135 US counties were merged with sociodemographic data from the 2014 American Community Survey and county-level estimates of health literacy based on the National Association of Adult Literacy Survey. We employed multilevel geographically weighted autoregressive models to predict fluoridation coverage of each county as a function of fluoridation coverage of neighboring counties and local-county covariates: either health literacy or sociodemographic characteristics. Akaike's Information Criterion was used to distinguish the better model in terms of explanatory power and parsimony.

RESULTS

In the best-fit model, an increase from the first to third quartile of neighboring counties' fluoridation coverage was associated with an increase of 27.76 percentage points (95% confidence limits [CI] = 27.71, 27.81) in a local county's fluoridation coverage, while an increase from the first to third quartile of local county's health literacy was associated with an increase of 2.8 percentage points (95% CL = 2.68, 2.89). The results are consistent with a process of emulation, in which counties implement fluoridation based upon their population's health literacy and the extent of fluoridation practiced in neighboring counties.

CONCLUSION

These results suggest that demand for community water fluoridation will increase as health literacy increases within a county. Furthermore, when considering expansion of fluoridation, non-fluoridated communities can benefit from precedents from nearby communities that are fluoridated.

KNOWLEDGE TRANSFER STATEMENT

Expanded coverage of community water fluoridation has stalled in the United States. The economic theory of diffusion describes how, over time and space, policy enacted in one community can influence public opinion in a neighboring community. This study applies geospatial analysis of county-level data and the theory of policy diffusion to demonstrate that fluoridated counties can promote the implementation of community water fluoridation in their neighboring, non-fluoridated communities.