In an advance toward solving a 50-year-old mystery, scientists are reporting new evidence on how the fluoride in drinking water, toothpastes, mouth rinses¹（口腔清洗剂） and other oral-care products prevents tooth decay. Their report appears in the ACS journal Langumir. Karin Jacobs and colleagues explain that despite a half-century of scientific research, controversy² still exists over exactly how fluoride compounds reduce the risk of tooth decay. That research established long ago that fluoride helps to harden the enamel³（搪瓷，珐琅） coating that protects teeth from the acid produced by decay-causing bacteria. Newer studies already found that fluoride penetrates⁴ into and hardens a much thinner layer of enamel than previously⁵ believed, lending credence⁶ to other theories about how fluoride works.

 

The report describes new evidence that fluoride also works by impacting the adhesion force of bacteria that stick to the teeth and produce the acid that causes cavities. The experiments -- performed on artificial teeth (hydroxyapatite pellets) to enable high-precision analysis techniques -- revealed that fluoride reduces the ability of decay-causing bacteria to stick, so that also on teeth, it is easier to wash away the bacteria by saliva⁷, brushing and other activity.

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