People considering teeth whitening treatments in London might want to visit a dentist for advice, if the following comments are anything to go by.

Enamel darkens naturally over time and other factors such as smoking and consuming certain foods can also make it look dull, explained 5 News.

A visit to an oral health specialist can inform patients of whether they are suitable for teeth whitening, the website suggested, adding certain tooth or gum conditions may mean such a treatment is not advisable.

"If you’re a candidate for teeth whitening your dentist can tell you how much whitening you can expect and help you choose the best technique for your teeth," the online resource stated.

Because the procedure can temporarily make the mouth more sensitive, the news provider recommended individuals do not brush within half an hour of the procedure.

To maintain a pearly white smile, it concluded people should clean teeth after meals, snack on crunchy vegetables and visit a dental hygienist twice a year.

According to the British Dental Health Foundation, the effects of teeth whitening can last for up to three years.