For the vast majority of people, teeth whitening is a pain free simple procedure that can produce remarkable results. For a small number of people there may be some sensitivity to hot & cold food and drink, which rapidly improves when the treatment has finished. Medications and desensitizing toothpastes are very effective at minimizing the effects which will be advised by your dentist.
Occasionally, the whitening gel can cause temporary soreness around the gums. This can be minimized if small amounts of the gel are used and the trays are not overloaded.
The colour improvement can be maintained by good oral hygiene and avoiding highly coloured food & drink. Smoking will rapidly cause the teeth to darken again. The good news is that by reapplying the home whitening solution will soon restore the post treatment colour.