They're saying that after eating fruit, drinking fruit juice or knocking back fizzy drinks, you should wait an hour before cleaning your set of gnashers.
This is because they contain acid that wears down the enamel - that's the stuff that protects them - on your teeth.
So instead of brushing the bad stuff off your teeth, you're actually rubbing it into them. This can cause pain and make your teeth smaller.
As a result she's had to make 12 visits to the dentist this year to have her teeth rebuilt.
But dentists aren't suggesting you give up cleaning your teeth completely - just wait a bit of time before polishing them!
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Watch Lizo Mzimba's report
How often do you clean your teeth?
