The most common reasons for teeth to get yellow or stained are:
Using tobacco
Drinking dark-coloured liquids such as coffee, cola, tea and red wine
Not taking good care of your teeth
Aging makes teeth less bright as the enamel gets thinner and the dentin becomes darker.
How It's Done?
There are two main types of whitening procedures. Vital whitening is performed on teeth that have live nerves. Non-vital whitening is done on a tooth that has had root-canal treatment and no longer has a live nerve.