Study Finds that Fluoride Reduces Adhesion of Bacteria on Teeth

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Despite more than fifty years of scientific research, controversy still exists over exactly how fluoride compounds reduce the risk of tooth decay. New evidence from German researchers suggests that fluoride helps to reduce the adhesion of bacteria to teeth. The study is published in the American Chemical Society (ACS) journal Langumir [1].

The cause of tooth decay and cavities

Research in the late 1940s and early 1950s established that fluoride helps to harden tooth enamel, which protects teeth from the acid produced by decay-causing bacteria [2-4]. Subsequent studies showed that fluoride enhances the tooth remineralization process [5-6].

Tooth decay and cavities are caused by tooth demineralization, a process where an acidic environment draws out some of the mineral content from a tooth’s calcium-hardened tissues. The acids that cause demineralization are produced by specific types of bacteria — primarily Streptococcus mutans and Lactobacillus — that live within dental plaque, the pale yellow biofilm that develops naturally on the teeth.

Fluoride enhances tooth remineralization (think of remineralization as tooth decay in reverse). Fluoride absorbs onto tooth surfaces where demineralization, or tooth decay, has occurred. The presence of fluoride attracts other minerals, increasing the rate of remineralization. In fact, the new tooth mineral created from remineralization is actually harder than the tooth was to begin with.

Another mechanism for fluoride against tooth decay

Researchers from the Saarland University in Germany report that fluoride also works by reducing the ability of decay-causing bacteria to stick to teeth, making it is easier to wash away the bacteria by saliva, brushing and drinking.

To characterize bacterial adhesion on fluoridated samples, experiments were performed on artificial teeth to allow for high-precision analysis techniques. Using force spectroscopy — an analytical technique that allows for the study of the mechanical properties of single polymer molecules, proteins or individual chemical bonds — scientists employed bacterial probes to directly measure adhesion forces. They tested the adhesion of different species of bacteria, including two cariogenic (meaning to cause tooth decay) microorganisms: Streptococcus mutans and Streptococcus oralis.

All bacteria tested, regardless of species, showed decreased adhesion after fluoride treatment of the teeth. The findings suggest that the decrease of adhesion properties is a further key factor for the cariostatic (meaning to stop tooth decay) effect of fluoride in addition to the decrease of demineralization. Understanding fluoride’s effect on bacterial adhesion has the potential to help develop better dental fillings, dental and medical implants.

Community water fluoridation

In the United States, the fluoridation of community water started in 1945, and is the single most effective public health measure to prevent tooth decay.

In a recent letter presented during the 2013 National Oral Health Conference, U.S. Surgeon General Regina Benjamin, M.D., praised community water fluoridation for its effectiveness in preventing tooth decay [7]:

Fluoridation’s effectiveness in preventing tooth decay is not limited to children, but extends throughout life, resulting in fewer and less severe cavities. In fact, each generation born since the implementation of water fluoridation has enjoyed better dental health than the generation that preceded it.

The Centers for Disease Control and Prevention has proclaimed community water fluoridation as one of 10 great public health achievements of the 20th century.

References

1. Loskill et al. Reduced Adhesion of Oral Bacteria on Hydroxyapatite by Fluoride Treatment. Langmuir. 2013 Apr 23. [Epub ahead of print]
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2. Van Huysen and Muhler. Enamel solubility reducing effect of flavored low concentration stannous fluoride solution. J Dent Res. 1948 Feb;27(1):46-51.
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3. Phillips and Swartz. Effect of fluorides on hardness of tooth enamel. J Am Dent Assoc. 1948 Jul;37(1):1-13.
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4. Ericsson Y. Reduction of the solubility of enamel surfaces. Acta Odontol Scand. 1950 Mar;9(1):60-83.
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5. Feagin et al. Study of the effect of calcium, phosphate, fluoride and hydrogen ion concentrations on the remineralization of partially demineralized human and bovine enamel surfaces. Arch Oral Biol. 1971 May;16(5):535-48.
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6. Gron et al. The effect of topically applied fluoride on enamel remineralization in vitro. Arch Oral Biol. 1975 Mar;20(3):223-4.
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7. ADA Welcomes Surgeon General Endorsement of Community Water Fluoridation. American Dental Association. 2013 Apr 22.