There are a number of reasons why a persons teeth can start to lose their whiten shine that most people so desperately desire.
The first thing I would like to say is that teeth lose their white colour naturally with age, so it is not abnormal to experience this. However there are certain things that can accelerate this process, one of the most common is tobacco smoke. Other things are red wine, coffee, tea and other foods that have strong food colourings.
In addition to this tooth decay and a build up of tartar can cause teeth to appear yellowish also, and proper dental hygiene is highly recommended in these circumstances. Another cause of teeth losing their color is when the nerves and or blood vessels get damaged that are inside the tooth. This usually happens when the tooth is knocked. When these factors are responsible for tooth discoloration, external teeth whitening products are of no use and should not be used.
One other less common cause of teeth to look yellow, is when an antibiotic called tetracycline is given to children whose teeth are still developing. The result can be that their adult teeth develop a yellowish tinge to them.
There are a number of products and procedures that are available for whitening teeth, however before you consider the best teeth whitener for you, I recommend that you first assess your oral hygiene and take care to look after your teeth and regularly remove all plaque to prevent build up, and reduce foods and drinks that may cause staining.