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They adjusted the results for the excretion ratio (adjusted for urinary creatinine and specific gravity, respectively).

Note that at least in Europe the toothpastes for children contain no fluoride.

Some brands of toothpaste substitute fluoride with xylitol. There is evidence that it hardens enamel.

In Germany toothpaste for children contains a third of the flouride of toothpaste for adults (500ppm).