© 2025 American Dental Association l 9
Fluoridation Facts
1. What is fluoride?
Answer
Fluoride is a naturally occurring mineral that can help prevent tooth decay.
Fact
The element fluorine is abundant in the Earth’s crust as a naturally occurring fluoride compound found
in rocks and soil.70,71 As groundwater moves through the Earth, it passes over rock formations and
dissolves the fluoride minerals that are present, releasing fluoride ions from the naturally occurring
fluorine in the rocks. This increases the fluoride content of the water. The concentration of fluoride
in groundwater (e.g., wells, springs) varies according to such factors as the depth at which the water
is found and the quantity of fluoride-bearing minerals in the area.
Fluoride is present at varied concentrations in all water sources, including rainwater and oceans. For
example, ocean fluoride levels range from 1.2 to 1.4 mg/L.72 In the United States, the natural level of
fluoride in groundwater varies from very low levels to more than 4 mg/L.26 In comparison, the fluoride
concentrations in surface water sources, such as lakes and rivers, are very low. For example, a water
analysis completed by the city of Chicago for 2023 lists the range for Lake Michigan’s natural fluoride
level as 0.06 to 0.11 mg/L.73
2. How does fluoride help prevent tooth decay?
Answer
Tooth decay begins when the outer layer of a tooth loses some of its minerals due to acid produced
by bacteria in dental plaque that breaks down the sugars and other refined carbohydrates that we
eat. This process is called demineralization. Fluoride protects teeth by helping to prevent the loss
of these minerals and by restoring them with a fluoride-containing mineral that is more resistant to
acid attacks. In other words, fluoride protects teeth by reducing demineralization and enhancing
remineralization. Fluoride also works to hinder bacterial activity necessary for the formation of
tooth decay.
Fact
One of fluoride’s main mechanisms of action is its ability to prevent or delay the loss of minerals in
teeth.35,59 Cavities start to form when minerals from the tooth surface are lost due to acid attacks
from bacteria in dental plaque, the soft, sticky film that is constantly forming on teeth. Acid-producing
bacteria thrive on the sugars and refined carbohydrates that we consume.
Fluoride’s second mechanism of action is called remineralization, which is the reversal of this
demineralization process.59,74 Teeth gain back the minerals lost during acid attacks through
remineralization, but with an important difference. Some of the hydroxyapatite crystal lost is
replaced with fluorapatite. This fluoride-rich replacement mineral is even more resistant to acid
attacks than the original tooth surface.59
Effectiveness and Benefits
Section 1
Fluoridation Facts
1. What is fluoride?
Answer
Fluoride is a naturally occurring mineral that can help prevent tooth decay.
Fact
The element fluorine is abundant in the Earth’s crust as a naturally occurring fluoride compound found
in rocks and soil.70,71 As groundwater moves through the Earth, it passes over rock formations and
dissolves the fluoride minerals that are present, releasing fluoride ions from the naturally occurring
fluorine in the rocks. This increases the fluoride content of the water. The concentration of fluoride
in groundwater (e.g., wells, springs) varies according to such factors as the depth at which the water
is found and the quantity of fluoride-bearing minerals in the area.
Fluoride is present at varied concentrations in all water sources, including rainwater and oceans. For
example, ocean fluoride levels range from 1.2 to 1.4 mg/L.72 In the United States, the natural level of
fluoride in groundwater varies from very low levels to more than 4 mg/L.26 In comparison, the fluoride
concentrations in surface water sources, such as lakes and rivers, are very low. For example, a water
analysis completed by the city of Chicago for 2023 lists the range for Lake Michigan’s natural fluoride
level as 0.06 to 0.11 mg/L.73
2. How does fluoride help prevent tooth decay?
Answer
Tooth decay begins when the outer layer of a tooth loses some of its minerals due to acid produced
by bacteria in dental plaque that breaks down the sugars and other refined carbohydrates that we
eat. This process is called demineralization. Fluoride protects teeth by helping to prevent the loss
of these minerals and by restoring them with a fluoride-containing mineral that is more resistant to
acid attacks. In other words, fluoride protects teeth by reducing demineralization and enhancing
remineralization. Fluoride also works to hinder bacterial activity necessary for the formation of
tooth decay.
Fact
One of fluoride’s main mechanisms of action is its ability to prevent or delay the loss of minerals in
teeth.35,59 Cavities start to form when minerals from the tooth surface are lost due to acid attacks
from bacteria in dental plaque, the soft, sticky film that is constantly forming on teeth. Acid-producing
bacteria thrive on the sugars and refined carbohydrates that we consume.
Fluoride’s second mechanism of action is called remineralization, which is the reversal of this
demineralization process.59,74 Teeth gain back the minerals lost during acid attacks through
remineralization, but with an important difference. Some of the hydroxyapatite crystal lost is
replaced with fluorapatite. This fluoride-rich replacement mineral is even more resistant to acid
attacks than the original tooth surface.59
Effectiveness and Benefits
Section 1
