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Dental Caries (Cavities): Community Water Fluoridation

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What the Task Force Found

About The Systematic Review

The Task Force finding is based on evidence from a systematic review published in 2000 (McDonagh et al., search period 1966-1999; 26 studies on caries; 13 on oral health disparities; 88 on fluorosis), combined with more recent evidence (search period 1999-2012; 29 studies of which 2 reported effects on caries, 3 reported on oral health disparities, and all measured fluorosis). All included studies evaluated intervention effectiveness of community water fluoridation among children.

The systematic review was conducted on behalf of the Task Force by a team of specialists in systematic review methods, and in research, practice, and policy related to oral health. The finding updates and replaces the 2000 Task Force finding on Dental Caries: Community Water Fluoridation [PDF - 255 kB].

Context

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Summary of Results

More details about study results are available in the Task Force Finding and Rationale Statement [PDF - 597 kB].

Results from both the McDonough et al. review and the updated search for evidence showed a decrease in new dental caries after community water fluoridation began and an increase in new dental caries when it stopped.

  • Combined evidence showed a median decrease of 15.2 percentage points in caries after community water fluoridation began (12 studies).
  • Included studies showed that community water fluoridation reduced the prevalence of dental caries across socioeconomic groups.

2000 Review -- McDonagh et al. (search period 1966-1999)

  • After community water fluoridation was started:
    • The number of individuals free of dental caries increased by a median of 14.6 percentage points (11 studies).
    • The median number of decayed, missing, or filled teeth decreased by 2.25 (10 studies).
  • When community water fluoridation was stopped:
    • Studies reported an increase in the number of decayed, missing, or filled teeth (6 studies) or surfaces (2 studies).

Updated Evidence (search period 1999-2012)

  • After community water fluoridation was started:
    • The number of individuals free of dental caries increased by a median of 25.1 percentage points (1 study).
  • When community water fluoridation was stopped:
    • The total number of decayed, missing, or filled tooth surfaces decreased by 0.59 among children 8 years of age, and 1.39 among children 14 years of age (1 study) when compared to communities that continued community water fluoridation.
    • The number of new decayed, missing, or filled surfaces increased by 0.13 among children 8 years of age, and by 0.47 among children 14 years of age (1 study) when compared to communities that continued community water fluoridation.

Summary of Economic Evidence

More details about study results are available in the Task Force Finding and Rationale Statement [PDF - 597 kB].

Ten studies were included in the economic review. Monetary values are presented in 2013 U.S. dollars.

Intervention cost:

  • For urban communities, per capita annual cost ranged from $0.11 to $4.92 (6 studies).
  • Population size was the main cause of variation; as the size of a community's population went up, the cost per person went down.
  • Cost estimates were based on two main components:
    • One-time fixed cost (for equipment, pipework, fluoridation pump, and tank area)
    • Annual recurring cost (for fluoride compounds, monitoring, maintenance, and operations)

Intervention benefit:

  • Benefit-only studies that used regression models concluded that the presence of water fluoridation was related to a reduction in dental treatment cost or claims (4 studies).
  • Studies that provided benefit and cost information reported a per capita annual benefit of community water fluoridation that ranged from $5.49 to $93.19 (6 studies).
  • The main causes of variation were the number of benefit components considered in each study (e.g., averted healthcare cost, averted productivity loss, other losses averted) and the assumptions made. Geographic differences in dental treatment and labor costs also played a role.

Benefit–cost ratio:

  • Benefit–cost ratios ranged from 1.1:1 to 135.0:1 (6 studies).
  • Lower benefit–cost ratios generally were associated with small community population sizes, with ratios increasing as community population size increased. This is mainly related to economies of scale on the cost side.

Applicability

Based on results, the Task Force finding should be applicable to the following:

  • Communities across the United States
  • Groups from all socioeconomic status (SES) groups

There is limited information about the unique effects of community water fluoridation among populations that are exposed to fluoride through other sources (e.g., dental products, infant formula).

Evidence Gaps

Additional research and evaluation are needed in these areas, to fill existing gaps in the evidence base. (What are evidence gaps?)

  • The contribution of alternative fluoride sources (e.g., toothpaste, mouth rinses), especially with growing concerns about the overall effect of multiple fluoride exposures
  • The effects of drinking bottled water on the benefits of community water fluoridation
  • The role of water hardness and dietary calcium in the bioavailability of fluoride in individuals and communities with varying milk consumption patterns and degrees of water hardness. The presence of calcium circulating in the body is believed to be associated with reduced fluoride absorption from the gastrointestinal tract.
  • Standardized measurement and reporting of dental fluorosis and caries to reduce measurement errors
  • Non-dental harms of community water fluoridation
  • The benefit of community water fluoridation to adults

Study Characteristics

  • Included studies were conducted in the United States, Europe, Canada, Asia, South America, Africa, Australia, the Middle East, and New Zealand.
  • Fluoride concentrations in most of the intervention sites ranged from 0.7 to 1.2 mg/L.

Publications