No pain No gain

I didn't realise that teeth whitening can cause pain. Bleaching can hurt. The smiling happy Pan Americans on the pack don't display how they suffered to get to where they are today. I notice the packaging has no disclaimer. It should read "product use may lead to you seriously questioning the value of whiter-than-white teeth". Was I left to discover this on my own?

The first day of treatment I felt mislead by my smiling friends. Were they gritting their teeth, or does the pain of bleaching simply firm their resolve to get 'the whitest of teeth'?