Fluoride Part I: Why is fluoride such a big deal and why is it so controversial?

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Introduction:

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Fluoride is a big deal in dentistry because of its ability to help prevent tooth decay.  It is also the center of controversy because of claims that it increases the risk for cancer, heart disease, osteoporosis and bone fracture, low intelligence, Alzheimer disease, allergic reactions, and other health conditions.  Just search “fluoride” online and you’ll see the frightening stuff out there!

In this blog post series (it will be at least 2 parts), I hope to provide some basic information about fluoride, its benefits, and the history of fluoride in community water.  I also hope to address some of the concerns associated with it:  Is it safe??  How much fluoride should we use?  Should I be concerned about too much fluoride?  Should I filter my water?  And more.

What is fluoride?

Fluoride_Periodic_table.jpg

Fluorine is element 9 on the periodic table of elements and fluoride is the anion (negatively charged ion) of fluorine.  Because fluorine is the most electronegative element it prefers to be in the form of fluoride, and this is how it is encountered in nature.  It is the 13th most common element in the earth’s crust, comprising 0.06-0.09% of it, and is ubiquitous in soil and all natural waters throughout the earth.1,2  Seawater typically contains fluoride at around 1.2-1.4 mg/L.1  Rivers and lakes typically contain fluoride at or less than about 0.5 mg/L, though there are lakes in Kenya with documented fluoride concentrations of up to 2,800 mg/L!1,2  Fluoride concentration in groundwater can be very low or very high (over 60 mg/L) depending on the nature of surrounding rocks and presence of fluoride-containing minerals.1,2

Fluoride – a champion in dentistry

As mentioned above, fluoride is a big deal in dentistry because of its anti-caries effects:

fluoroapatite.jpg

  • Fluoride enhances remineralization and resistance to demineralization.

  • There is also extensive literature demonstrating fluoride’s antimicrobial effects.

For more details about these benefits, see this post here.

How were these benefits first discovered?  Read on. 

History of Fluoride in the Water

Once upon a time (early 1900’s), in the lands of Colorado Springs, CO and Bauxite, AR, there were two astute dentists who first took note of the above benefits of fluoride.  Although it was unknown at the time, their communities had naturally high levels of fluoride in their water sources and the dentists both noted mottled and stained enamel on the teeth of many of their patients (we now call this fluorosis – to be discussed later).  They also noted that the teeth seemed less susceptible to decay.  Fluoride wasn’t identified as the etiologic agent until 1930, however, and initially the effects were just attributed to an unknown agent in the water sources.3 

In 1930, thanks to spectrographic analysis of the water in Bauxite, AR, fluoride was identified as the causative agent for the mottled enamel.  The NIH then investigated the association between fluoride and mottled enamel, adopting the term “fluorosis” to describe and classify the varying degrees of effected enamel (still to be discussed later).3  

SIDE NOTE: 

ppm = parts per million. 

Equivalent to 1.0 ppm = 1 mg/L. 

Data collected from 26 states showed that children in cities with naturally higher levels of fluoride in their water experienced lower rates of dental decay, with the fluoride concentration of 1.0 ppm being the sweet spot.  At concentrations above 1.0 ppm fluoride the benefits leveled off while the prevalence of dental fluorosis increased.  At 1.0 ppm, the prevalence of dental fluorosis was low and mostly very mild.3

NIH dentists examined the school children and gathered saliva samples in grand rapids, michigan once a year to document the effects of fluoride on teeth.https://www.nidcr.nih.gov/health-info/fluoride/the-story-of-fluoridation

NIH dentists examined the school children and gathered saliva samples in grand rapids, michigan once a year to document the effects of fluoride on teeth.

https://www.nidcr.nih.gov/health-info/fluoride/the-story-of-fluoridation

These findings led to a study that began in 1945 involving community water supplies in Michigan, New York, Illinois, and Ontario, Canada.  Cities with negligible levels of fluoride in their water were selected to have fluoride added to the community water supplies to achieve fluoride concentrations of 1.0-1.2 ppm.  Over the next 13-15 years, cross sectional surveys found that decay was reduced by 50%-70% among children in the communities with the fluoridated water.3  Not surprisingly, these findings led to adoption of community water fluoridation in many cities throughout the US. 

Fluoride in the water today

Unfortunately, dental decay remains one of the most common chronic diseases in children and adults in the US.  According to the CDC, “over 34 million school hours are lost and over $45 billion is lost in productivity each year due to unplanned (emergency) dental care.”4

Nonetheless, because of its “contribution to the dramatic decline in tooth decay over the past 70 years,” the CDC has heralded fluoridation of community water as “1 of 10 great public health achievements of the 20th century.”3

These days, community water fluoridation is given credit for decreasing tooth decay by about 25% (a smaller percentage than the 50-70% in the initial years of water fluoridation due to fluoride availability in other readily accessible sources such as toothpaste).5-8

As of 2014, 74.4% of the US population that receives community water has access to fluoridated water.  The CDC has the goal of this percentage increasing to 80% by 2020.9

What is considered the optimal fluoride level?

INTERESTING SIDE NOTE:

In numerous countries where water fluoridation is not feasible or cost-effective, salt or milk are fortified with fluoride.  This has lead to a drop in the prevalence of tooth decay in those countries similar to the drop seen in countries with fluoridated community water.12,13

In 1962, the range of optimum fluoride concentration in the US was initially determined to be 0.7-1.2 ppm.  This range was set to minimize fluorosis and maximize anti-caries effects.  Lower fluoride concentration was recommended for warmer US climates where water consumption would be higher, and higher concentration was recommended for cooler US climates.10  

However, with the increased availability of fluoride through oral hygiene products as well as increased consumption of food and soft drinks processed with fluoridated water, the original range has become outdated.  In 2015, the US Dept of Health and Human Services determined 0.7 mg/L as the optimal concentration for fluoride in water.10 

The WHO suggests 0.5 – 1.0 mg/L.



Dental fluorosis  

We all know that there is such a thing as too much of a good thing.  Fluoride is no exception.

As previously alluded, excess fluoride ingestion can affect the appearance and structure of teeth.  The term for this is dental fluorosis. 

Fluorosis occurs when the following factors align:

  1. Fluoride present in sufficient quantity (serum fluoride levels are determined by various factors, including fluoride ingestion, bone remodeling, and fluoride excretion in the urine)

  2. Fluoride present for sufficient duration (we would be far more likely to see impact of daily consumption of high fluoride levels than a one-time exposure)

  3. Developing teeth are at the stage of enamel maturation (age birth to 9 years)

Mild fluorosis appears as paper white striations or patches.  More severe fluorosis is characterized by pitting or loss of enamel and often subsequent staining.  Severity of fluorosis depends on the amount and duration of fluoride exposure.  

Dental fluorosis. a Mild with slight accentuation of the perikymata. b Moderate, showing a white opaque appearance. c Moderate, white opaque enamel with some discoloration and pitting. d Severe.DenBesten, Pamela, and Wu Li. “Chronic fluoride toxicit…

Dental fluorosis. a Mild with slight accentuation of the perikymata. b Moderate, showing a white opaque appearance. c Moderate, white opaque enamel with some discoloration and pitting. d Severe.

DenBesten, Pamela, and Wu Li. “Chronic fluoride toxicity: dental fluorosis.” Monographs in oral science vol. 22 (2011): 81-96. doi:10.1159/000327028

How does it occur?  

During normal enamel maturation, the protein matrix (framework) of the enamel is replaced by minerals.  Sufficiently high levels of fluoride can disrupt this process by binding protein, leading to a delay in protein removal.  Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands.11  The end result: more porous enamel. 

Although teeth with mild fluorosis may have increased resistance to decay, severely fluorosed teeth are more susceptible to decay due to the improperly formed enamel.

Can fluorosis be treated?

The treatment options for dental fluorosis is limited, however treatment for fluorosis alone is not necessary unless the appearance bothers the patient.  For the mildest forms of fluorosis, bleaching can decrease the prominence of white striations or patches.  If a more severely fluorosed tooth breaks down or develops decay, a filling or crown would be needed, as with any other tooth that is decayed or broken.

Stay tuned for more

We’ve made it through Part I!  It’s a very dense but very important topic.  In Part II (and probably a Part III) I’ll aim to cover more of the controversy surrounding fluoride.  I will also discuss the significance of all of this and applications for day-to-day living:

  • Do adults benefit from fluoride?  Or just children with developing teeth?

  • If I drink fluoridated water, do I need topical fluoride?

  • What should you do if your child eats his or her toothpaste?

  • Should you be concerned about fluoride when feeding your baby formula reconstituted with fluoridated water?

  • What is done to protect us from too much fluoride?  How can I find out about fluoride in my water?

  • Does filtration remove fluoride?

And maybe more…as I said, stay tuned!

References:

  1. WHO 2017. Guidelines for drinking-water quality. Fourth edition.  World Health Organization, Geneva.  https://www.who.int/water_sanitation_health/dwq/nutrientschap14.pdf?ua=1.

  2. WHO 2006.  Fluoride in Drinking-water. World Health Organization, Geneva.  https://www.who.int/water_sanitation_health/publications/fluoride_drinking_water_full.pdf

  3. Centers for Disease Control and Prevention. Achievements in public health, 1900–1999: fluoridation of drinking water to prevent dental caries. MMWR. 1999;48(41):933–940.

  4. Centers for Disease Control and Prevention.  Oral Health Basics.  2019.  https://www.cdc.gov/oralhealth/basics/index.html

  5. Koulourides T. Summary of session II: Fluoride and the caries process. J Dent Res. 1990;69(Spec Iss):558.

  6. Featherstone JD. Prevention and reversal of dental caries: Role of low level fluoride. Community Dent Oral Epidemiol. 1999;27:30–40.

  7. Truman BI, Gooch BF, Sulemana I, et al. Reviews of evidence on interventions to prevent dental caries, oral and pharyngeal cancers, and sports-related craniofacial injuries. Am J Prev Med. 2002(1S):21–54.

  8. Griffin SO, Regnier E, Griffin PM, Huntley V. Effectiveness of fluoride in preventing caries in adults. J Dent Res. 2007;86:410–415

  9. Centers for Disease Control and Prevention.  Community Water Fluoridation: Water Fluoridation Basics and Statistics.  2016.  https://www.cdc.gov/fluoridation/statistics/2014stats.htm

  10. U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. “U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries.” Public health reports (Washington, D.C. : 1974) vol. 130,4 (2015): 318-31. doi:10.1177/003335491513000408

  11. DenBesten, Pamela, and Wu Li. “Chronic fluoride toxicity: dental fluorosis.” Monographs in oral science vol. 22 (2011): 81-96. doi:10.1159/000327028

  12. Aoun, Antoine et al. “The Fluoride Debate: The Pros and Cons of Fluoridation.” Preventive nutrition and food science vol. 23,3 (2018): 171-180. doi:10.3746/pnf.2018.23.3.171

  13. WHO 2010.  Inadequate or excess fluoride: a major public health concern. World Health Organization, Geneva.  https://www.who.int/ipcs/features/fluoride.pdf?ua=1