Is whitening your teeth a good or bad idea?
There are conflicting theories on the internet but reading a news article in the Daily Mail Online I seem to sway towards their findings (probably because they aren’t trying to sell me their product!).
The recommended doses of hydrogen peroxide for any home teeth whitening kit, according to this article, shouldn’t be above 0.1%. But on websites selling home kits the doses seem to vary, one claiming it contained just under 6% -

“The proper use of tooth whitening products containing > .1 to 6.0% hydrogen peroxide (or equivalent for hydrogen peroxide releasing substances) is considered safe after consultation with and approval of the consumer’s dentist”  2006 The Scientific Committee on Consumer Products

So what can too much hydrogen peroxide do to your mouth?
•    Cause chemical burns in the mouth
•    Cause sensitive teeth
•    intensify  gum disease
The news article found that the majority of kits contained more than 0.1% except the Boots Expert Teeth Whitening and Brilliant Tooth Whitening Products (which you can buy at pharmacy outlets).
I recommend using your Dentist, or a specialist, at least you know what you’re getting then!