Association Between Water Fluoridation and Income-Related Dental Caries of US Children and Adolescents | Adolescent Medicine | JAMA Pediatrics | JAMA Network
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Figure.  Predicted Covariate-Adjusted Number of Tooth Surfaces Affected by Dental Caries in the Primary and Permanent Dentitions (National Health and Nutrition Examination Surveys 1999-2004, 2011-2014), Stratified by County Population Coverage of Fluoridated Community Drinking Water
Predicted Covariate-Adjusted Number of Tooth Surfaces Affected by Dental Caries in the Primary and Permanent Dentitions (National Health and Nutrition Examination Surveys 1999-2004, 2011-2014), Stratified by County Population Coverage of Fluoridated Community Drinking Water

Decayed and filled primary tooth surfaces in children aged 2 to 10 years (A) and decayed, missing, and filled permanent tooth surfaces in those aged 6 to 17 years (B). The values on the x-axis were selected to represent income to poverty ratio. Living in a predominantly fluoridated county reduced the magnitude of income inequalities in dental caries. This attenuation was statistically significant in the primary dentition (P value for interaction of .03) but failed to reach significance in the permanent dentition of those aged 6 to 17 years (P value for interaction, .49). Values were adjusted for sex, age, race/ethnicity, urban rural classification, and time since last dental visit. Tables below plots report mean fluoridation-related caries reductions as absolute differences (adjusted mean caries for <75% population coverage group minus ≥75% population coverage group) and relative differences (absolute difference divided by adjusted mean caries for <75% population coverage group) for selected values of income to poverty ratio. Data given below the plots report mean fluoridation-related caries reductions as absolute differences (adjusted mean caries for <75% population coverage group minus ≥75% population coverage group) and relative differences (absolute difference divided by adjusted mean caries for <75% population coverage group) for selected values of income to poverty ratio.

Table.  Characteristics of 11 093 US Children, County Fluoridation Coverage, and Dental Caries Experience for Primary and Permanent Dentitions, National Health and Nutrition Examination Survey 1999 to 2004 and 2011 to 2014a
Characteristics of 11 093 US Children, County Fluoridation Coverage, and Dental Caries Experience for Primary and Permanent Dentitions, National Health and Nutrition Examination Survey 1999 to 2004 and 2011 to 2014a
1.
Slade  GD, Sanders  AE.  Two decades of persisting income-disparities in dental caries among US children and adolescents.  J Public Health Dent. 2018;78(3):187-191. doi:10.1111/jphd.12261PubMedGoogle ScholarCrossref
2.
McLaren  L, Emery  JC.  Drinking water fluoridation and oral health inequities in Canadian children.  Can J Public Health. 2012;103(7)(suppl 1):eS49-eS56.PubMedGoogle Scholar
3.
Slade  GD, Grider  WB, Maas  WR, Sanders  AE.  Water fluoridation and dental caries in US children and adolescents.  J Dent Res. 2018;97(10):1122-1128. doi:10.1177/0022034518774331PubMedGoogle ScholarCrossref
4.
Dye  BA, Tan  S, Smith  V,  et al.  Trends in oral health status: United States, 1988-1994 and 1999-2004.  Vital Health Stat 11. 2007;(248):1-92.PubMedGoogle Scholar
5.
Bui  AL, Dieleman  JL, Hamavid  H,  et al.  Spending on children’s personal health care in the United States, 1996-2013.  JAMA Pediatr. 2017;171(2):181-189. doi:10.1001/jamapediatrics.2016.4086PubMedGoogle ScholarCrossref
6.
O’Connell  J, Rockell  J, Ouellet  J, Tomar  SL, Maas  W.  Costs and savings associated with community water fluoridation in the United States.  Health Aff (Millwood). 2016;35(12):2224-2232. doi:10.1377/hlthaff.2016.0881PubMedGoogle ScholarCrossref
Research Letter
January 28, 2019

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

Author Affiliations
  • 1Department of Dental Ecology, School of Dentistry, University of North Carolina at Chapel Hill
  • 2US Census Bureau, Durham, North Carolina
  • 3Dental Public Health Consultant, North Bethesda, Maryland
  • 4Odum Institute for Research in Social Science, Department of Political Science, University of North Carolina at Chapel Hill
JAMA Pediatr. 2019;173(3):288-290. doi:10.1001/jamapediatrics.2018.5086

By age 11 years, an American child living in poverty has twice the level of dental caries (tooth decay) as one living at 3 times the poverty threshold.1 To achieve the Healthy People 2020 overarching goal of health equity, interventions must preferentially prevent disease at the lower end of the income distribution. Research conducted in Canada2 suggests that water fluoridation might reduce inequality, but that possibility has not been investigated in the United States. We used 2 nationally representative data sets to investigate whether water fluoridation attenuated income-related inequality in dental caries among US children and adolescents.

Methods

In this cross-sectional epidemiologic investigation, we merged county-level fluoridation data from the Centers for Disease Control and Prevention’s Water Fluoridation Reporting System with dental caries data from 1999-2004 and 2011-2014 cycles of the National Health and Nutrition Examination Survey (NHANES).3 Counties were classified as predominantly fluoridated where 75% or more of the population was served by fluoridated water and otherwise as less fluoridated. Dental caries was quantified as the sum of decayed and filled primary (ie, deciduous) tooth surfaces (dfs) for children aged 2 to 10 years (n = 5835), and the sum of decayed, missing, and filled permanent tooth surfaces (DMFS) for those aged 6 to 17 years (n = 8384). The University of North Carolina's Office of Human Research Ethics determined that this study does not constitute human subjects research. We regressed dental caries on family income to poverty ratio (modeled as a continuous variable), county fluoridation status (dichotomous variable), and the interaction of those variables, adjusting for survey cycle, age, sex, race/ethnicity, rural-urban location, and time since last dental visit. Analysis took account of the NHANES complex survey design, producing estimates for the US child and adolescent populations. Data analysis was conducted between July 2017 and September 2018; SAS, version 9.3 (SAS Institute Inc), software was used. Significance was determined at P < .05.

Results

Children in families with low income—but not those living in poverty—were less likely than other income groups to live in a predominantly fluoridated county (Table). Inverse income gradients in dental caries were most pronounced in the primary dentition.

In predominantly fluoridated counties, the income gradient in dfs was attenuated by 41% (estimated slope [β] = –0.62; SE, 0.13) compared with less-fluoridated counties (β = –1.06; SE, 0.18) and the interaction was statistically significant (P = .03) (Figure, A). Absolute and relative fluoridation-related caries reductions were most pronounced for the lowest income level. For permanent teeth, there was 18% attenuation of the income gradient in DMFS in predominantly fluoridated counties (β = –0.32; SE, 0.06) compared with less-fluoridated counties (β = –0.39; SE, 0.08), although the interaction was not significant (P = .49) (Figure, B). The interaction with income was significant (P = .002) under a more restrictive assumption that the percentage of population living in a fluoridated area, when modeled as a continuous variable, has a linear effect on the income gradient in DMFS.

Discussion

To our knowledge, this is the first US study to show evidence that water fluoridation attenuates income-related inequalities in dental caries. The degree of attenuation was less pronounced in the permanent dentition, possibly because the level of decay was about half that of primary teeth. Greater attenuation in the permanent dentition might be seen in early adulthood, as the burden of DMFS doubles between adolescence and early adulthood.4

One limitation of this study is its cross-sectional study design, which restricts causal interpretations. Also, in the absence of information about individuals' consumption of water, county of residence was used as a proxy for exposure to fluoridation. The resulting misclassification of exposure likely biases measures of association towards the null.

These findings have public health relevance, as dental caries in the primary dentition affects one-half of children aged 6 to 8 years.3 In 2013, the United States spent $26.9 billion on child and adolescent oral health, exceeding the combined spending on asthma, upper respiratory tract infections, other infectious diseases, and anxiety.5 Economic modeling suggests that fluoridation of currently unfluoridated US communities with populations of 1000 or more would annually save $2.5 billion in costs related to dental caries.6 The current findings provide additional support for water fluoridation as a means toward the Healthy People 2020 goals of achieving health equity, eliminating disparities, and improving the health of all groups.

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Article Information

Corresponding Author: Anne E. Sanders, PhD, Department of Dental Ecology, School of Dentistry, University of North Carolina at Chapel Hill, 385 S Columbia St, Koury Oral Health Sciences Building, Chapel Hill, NC 27599 (anne_sanders@unc.edu).

Published Online: January 28, 2019. doi:10.1001/jamapediatrics.2018.5086

Author Contributions: Drs Grider and Slade had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Sanders, Curiel.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Sanders.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Grider, Curiel, Slade.

Obtained funding: Sanders, Slade.

Administrative, technical, or material support: Sanders, Grider, Maas, Slade.

Supervision: Sanders.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was supported by National Institutes of Health/ National Institute of Dental and Craniofacial Research grant UH2DE025494.

Role of the Funder/Sponsor: The funding organization had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: Any opinions and conclusions expressed herein are those of the authors and do not necessarily represent the views of the US Census Bureau. The research in this article does not use any confidential Census Bureau information.

References
1.
Slade  GD, Sanders  AE.  Two decades of persisting income-disparities in dental caries among US children and adolescents.  J Public Health Dent. 2018;78(3):187-191. doi:10.1111/jphd.12261PubMedGoogle ScholarCrossref
2.
McLaren  L, Emery  JC.  Drinking water fluoridation and oral health inequities in Canadian children.  Can J Public Health. 2012;103(7)(suppl 1):eS49-eS56.PubMedGoogle Scholar
3.
Slade  GD, Grider  WB, Maas  WR, Sanders  AE.  Water fluoridation and dental caries in US children and adolescents.  J Dent Res. 2018;97(10):1122-1128. doi:10.1177/0022034518774331PubMedGoogle ScholarCrossref
4.
Dye  BA, Tan  S, Smith  V,  et al.  Trends in oral health status: United States, 1988-1994 and 1999-2004.  Vital Health Stat 11. 2007;(248):1-92.PubMedGoogle Scholar
5.
Bui  AL, Dieleman  JL, Hamavid  H,  et al.  Spending on children’s personal health care in the United States, 1996-2013.  JAMA Pediatr. 2017;171(2):181-189. doi:10.1001/jamapediatrics.2016.4086PubMedGoogle ScholarCrossref
6.
O’Connell  J, Rockell  J, Ouellet  J, Tomar  SL, Maas  W.  Costs and savings associated with community water fluoridation in the United States.  Health Aff (Millwood). 2016;35(12):2224-2232. doi:10.1377/hlthaff.2016.0881PubMedGoogle ScholarCrossref
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