Key Findings - Fluoride's Topical vs. Systemic Effects:
When water fluoridation first began in the 1940s, dentists believed that fluoride's main benefit came from ingesting fluoride during the early years of life. This belief held sway for over 40 years.
However, it is now acknowledged by dental researchers to be incorrect. According to the Centers for Disease Control, fluoride's predominant effect is TOPICAL (direct contact with teeth) and not systemic (from ingestion).
Hence, there is no need to ingest fluoride to derive it's purported benefit for teeth.
As stated by the US Centers for Disease Control:
"[L]aboratory and epidemiologic research suggests that fluoride prevents dental caries predominantly after eruption of the tooth into the mouth, and its actions primarily are topical for both adults and children" (CDC, 1999, MMWR 48: 933-940).
CONNETT: You mentioned that fluoride's benefits come from the local, or topical, effect. Could you just discuss a little more what you see as the significance of that fact? Why is it important that fluoride's benefit is topical, and not from ingestion?
CARLSSON: Well, in pharmacology, if the effect is local, it's of course absolutely awkward to use it in any other way than as a local treatment. I mean this is obvious. You have the teeth there, they're available for you, why drink the stuff?... I see no reason at all for giving it in any other way than locally -- topically, if you wish.
Excerpts from the Scientific Literature - Topical Vs. Systemic: (back to top)
"Fluoride is most effective when used topically, after the teeth have erupted."
"it is now accepted that systemic fluoride plays a limited role in caries prevention."
“the major anticaries benefit of fluoride is topical and not systemic.”
"Since the current scientific thought is that the cariostatic activity of fluoride is mainly due to its topical effects, the need to provide systemic fluoride supplementation for caries prevention is questionable."
“The results of more recent epidemiological and laboratory
studies can be summarized by stating that post-eruptive
(topical) application of fluoride plays the dominant role in caries
"When it was thought that fluoride had
to be present during tooth mineralisation to 'improve' the biological
apatite and the 'caries resistance' of the teeth, systemic fluoride
administration was necessary for maximum benefit. Caries
reduction therefore had to be balanced against increasing dental
fluorosis. The 'caries resistance' concept
was shown to be erroneous 25 years ago, but the new paradigm is
not yet fully adopted in public health dentistry, so we
still await real breakthroughs in more effective use of fluorides
for caries prevention."
“Current evidence strongly suggests
that fluorides work primarily by topical
means through direct action on the teeth and dental plaque. Thus
ingestion of fluoride is not essential for caries prevention."
"[T]he majority of benefit from fluoride
is now believed to be from its topical, rather than systemic,
"For a long time, the systemic effect
of fluoride was regarded to be most important, resulting in recommendations
to use fluoride supplements such as tablets or drops. However,
there is increasing evidence that the local effect of fluoride
at the surface of the erupted teeth is by far more important."
"By 1981, it was therefore possible to propose a paradigm
shift concerning the cariostatic mechanisms of fluorides in which
it was argued that the predominant, if not the
entire, explanation for how fluoride controls caries lesion development
lies in its topical effect on de- and remineralization
processes taking place at the interface between the tooth surface
and the oral fluids. This concept has gained wide acceptance...
With today's knowledge about the mechanisms of fluoride action,
it is important to appreciate that, as
fluoride exerts its predominant effect... at the tooth/oral fluid
interface, it is possible for maximum
caries protection to be obtained without the ingestion of fluorides
to any significant extent."
"[F]luoride's predominant effect is post-eruptive
"The prevalence of dental caries in a
population is not inversely related to the concentration of fluoride
in enamel, and a higher concentration of enamel fluoride is not
necessarily more efficacious in preventing dental caries."
"Fluoride incorporated during tooth development
is insufficient to play a significant role in caries protection."
"Current evidence suggests that the predominant
beneficial effects of fluoride occur locally at the tooth surface,
and that systemic (pre-eruptive) effects are of much less importance."
"Fluoride supplementation regimens suffer from several shortcomings,
the first of which may be their derivation from a time when the
major effect of fluoride was thought to be systemic. Although
evidence that fluoride exerts its effects mainly through topical
contact is great, supplementation schemes still focus on the ingestion
"The case is essentially a risk-benefit issue - fluoride
has little pre-eruptive impact on caries prevention, but presents
a clear risk of fluorosis."
"Until recently the major caries-inhibitory effect of fluoride
was thought to be due to its incorporation in tooth mineral during
the development of the tooth prior to eruption...There
is now overwhelming evidence that the primary caries-preventive
mechanisms of action of fluoride are post-eruptive through 'topical'
effects for both children and adults."
"[L]aboratory and epidemiologic research suggests that fluoride
prevents dental caries predominantly after eruption of the tooth
into the mouth, and its actions primarily are topical for both
adults and children."
"[R]esearchers are discovering that the topical
effects of fluoride are likely to mask any benefits that ingesting
fluoride might have... This has obvious implications for the use
of systemic fluorides to prevent dental caries."
"Although it was initially thought that
the main mode of action of fluoride was through its incorporation
into enamel, thereby reducing the solubility of the enamel, this
pre-eruptive effect is likely to be minor. The evidence
for a post-eruptive effect, particularly its role in inhibiting
demineralization and promoting remineralization, is much stronger."
"Recent research on the mechanism of action
of fluoride in reducing the prevalence of dental caries (tooth
decay) in humans shows that fluoride acts topically (at the surface
of the teeth) and that there is neglible benefit in ingesting
"On the basis of the belief that an adequate intake of fluoride
in early life is protective against caries in later life, fluoride
supplements are recommended for infants and children living in
areas in which the fluoride content of the drinking water is low.
However, critical reviews of the evidence have
led to the conclusion that the effect of fluoride in decreasing
the prevalence and severity of dental caries is not primarily
systemic but exerted locally within the oral cavity. Because
fluoride supplements are quickly cleared from the mouth, the possibility
must be considered that they may contribute to enamel fluorosis,
which is unquestionably a systemic effect, while providing relatively
little protection against dental caries."
"It is now well-accepted that the primary
anti-caries activity of fluoride is via topical action."
"I have argued in this paper that desirable
effects of systemically administered fluoride are quite minimal
or perhaps even absent altogether."
"It, therefore, becomes evident that a
shift in thinking has taken place in terms of the mode of action
of fluorides. Greater emphasis is now placed on topical rather
than on systemic mechanisms..."
"[E]vidence has continued to accumulate to
support the hypothesis that the anti-caries mechanism of fluoride
is mainly a topical one."
"Until recently most caries preventive programs
using fluoride have aimed at incorporating fluoride into the dental
enamel. The relative role of enamel fluoride in caries prevention
is now increasingly questioned, and based on rat experiments and
reevaluation of human clinical data, it appears to be of minor
importance... [A]ny method which places particular emphasis
on incorporation of bound fluoride into dental enamel during formation
may be of limited importance."