>>> From Patent #5,807,541 "NSAID/fluoride periodontal compositions and methods" (15 Sept 1998), filed by the pharmaceutical company Sepracor:

A method for preventing dental caries [cavities] by administering fluoride and, at the same time controlling periodontal bone loss precipitated by the fluoride, by providing a combination of fluoride and NSAID is disclosed.

...

We have found that fluoride, in the concentration range in which it is employed for the prevention of dental caries [cavities], stimulates the production of prostaglandins and thereby exacerbates the inflammatory response in gingivitis and periodontitis.

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Thus, the inclusion of fluoride in toothpastes and mouthwashes for the purpose of inhibiting the development of caries [cavities] may, at the same time, accelerate the process of chronic, destructive periodontitis.

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