Teeth get discoloured generally due to extrinsic factors due to any kind of intake and poor Oral hygiene. If it's external then simple cleaning and polishing can solve the problem with some changes in your intake and regular course of twice brushing. If it's internal due to some injury or any abnormality should be dealt with other mortalities like Root canal treatments n crowns.

hi, there are lot of reasons for discoloration of teeth from poor oral hygiene to lot of coffee drinking, any medication, so you need to visit a dentist for proper diagnosis. Dr srikanth Guduguntla 9849156994

hi, stains on teeth could be extrinsic(on the surface) or intrinsic(from inside), a clinical examination would easily confirm that, and suitable treatment would be advised. For a 16yr old it would most probably be extrinsic which can easily be treated.