Oh dear you are relying on newspapers now?
The Daily Mail is one of the worst in the UK for printing rubbish
They don't research it properly and make a lot of it up.
Look at the studies on teeth whitening not newpaper article.
I quoted one of these and there are several more on whitening.
It's not the same thing as mouthwash
Stonger concentrations are used or for long periods. Acids have been used by some clinics and thats what does the most damage not ClO2