18 l © 2025 American Dental Association
Section 1: Effectiveness and Benefits
The benefits of fluoridation are extended to everyone in a community where
they live, work, attend school or daycare, or play, and it does not require a
change of behavior or access to dental care.
8. With other sources of fluoride now available, is water fluoridation still
an effective method for preventing tooth decay?
Answer
Yes. Even in an era with widespread availability of fluoride from other sources, studies show
that community water fluoridation prevents about 25% of tooth decay in children and adults
throughout the lifespan.
Fact
During the 1940s, studies demonstrated that children in communities with optimally fluoridated drinking
water had reductions in tooth decay rates of approximately 40–60% compared to those living in non-
fluoridated communities.101,102 At that time, drinking water was the only source of fluoride other than
fluoride that occurred naturally in foods.
Increase in the Number of Sources of Fluoride
Fluoride is available today from a number of sources, including water, beverages, food, and dental
products (toothpaste rinses professionally applied fluoride foams, gels, and varnish and dietary
supplements).39 As a result of the widespread availability of these various sources of fluoride, the
difference between decay rates in fluoridated areas and non-fluoridated areas is less than it was
several decades ago, yet it is still significant.39 Contemporary studies show that community water
fluoridation prevents about 25% of tooth decay in children and adults throughout the lifespan.62,63
The benefits of fluoridation are extended to everyone in a community where they live, work, attend
school or daycare, or play, and it does not require a change of behavior or access to dental care.
The Diffusion or Halo Effect
The diffusion or “halo” effect occurs because foods and beverages processed in optimally fluoridated
communities, which generally contain higher levels of fluoride than those processed in non-fluoridated
communities, are also distributed to non-fluoridated areas. This exposure to fluoride in non-fluoridated
areas through the diffusion effect lessens the differences in the amount of tooth decay among
communities.100,103,104 The best available national data demonstrate that the failure to account for the
diffusion effect results in an underestimation of the total benefit of water fluoridation, especially in areas
where large quantities of beverage and food products produced with optimally fluoridated water are
brought into non-fluoridated communities.105
Exposure to Fluoridation over the Lifespan
Another factor in the difference between decay rates in fluoridated areas and non-fluoridated areas is
the high geographic mobility of our society. On a day-to-day basis, many individuals reside in a non-
fluoridated community but spend a significant part of their day in a fluoridated community at work,
school, or daycare. Additionally, over their lifetime, people tend to move and reside in a number of
Section 1: Effectiveness and Benefits
The benefits of fluoridation are extended to everyone in a community where
they live, work, attend school or daycare, or play, and it does not require a
change of behavior or access to dental care.
8. With other sources of fluoride now available, is water fluoridation still
an effective method for preventing tooth decay?
Answer
Yes. Even in an era with widespread availability of fluoride from other sources, studies show
that community water fluoridation prevents about 25% of tooth decay in children and adults
throughout the lifespan.
Fact
During the 1940s, studies demonstrated that children in communities with optimally fluoridated drinking
water had reductions in tooth decay rates of approximately 40–60% compared to those living in non-
fluoridated communities.101,102 At that time, drinking water was the only source of fluoride other than
fluoride that occurred naturally in foods.
Increase in the Number of Sources of Fluoride
Fluoride is available today from a number of sources, including water, beverages, food, and dental
products (toothpaste rinses professionally applied fluoride foams, gels, and varnish and dietary
supplements).39 As a result of the widespread availability of these various sources of fluoride, the
difference between decay rates in fluoridated areas and non-fluoridated areas is less than it was
several decades ago, yet it is still significant.39 Contemporary studies show that community water
fluoridation prevents about 25% of tooth decay in children and adults throughout the lifespan.62,63
The benefits of fluoridation are extended to everyone in a community where they live, work, attend
school or daycare, or play, and it does not require a change of behavior or access to dental care.
The Diffusion or Halo Effect
The diffusion or “halo” effect occurs because foods and beverages processed in optimally fluoridated
communities, which generally contain higher levels of fluoride than those processed in non-fluoridated
communities, are also distributed to non-fluoridated areas. This exposure to fluoride in non-fluoridated
areas through the diffusion effect lessens the differences in the amount of tooth decay among
communities.100,103,104 The best available national data demonstrate that the failure to account for the
diffusion effect results in an underestimation of the total benefit of water fluoridation, especially in areas
where large quantities of beverage and food products produced with optimally fluoridated water are
brought into non-fluoridated communities.105
Exposure to Fluoridation over the Lifespan
Another factor in the difference between decay rates in fluoridated areas and non-fluoridated areas is
the high geographic mobility of our society. On a day-to-day basis, many individuals reside in a non-
fluoridated community but spend a significant part of their day in a fluoridated community at work,
school, or daycare. Additionally, over their lifetime, people tend to move and reside in a number of
