A. The first thing you need to find out is the cause of the discolouration.  This can be due to the nerve inside the tooth dying , the tooth being stained or internal staining possibly caused by antibiotics as a child.  Sometimes if the nerve is cleaned out the tooth can be whitened and it may not need any other treatment.  A veneer can mask the colour and this can be made of composite (tooth coloured filling) or porcelain.  Whatever material is used the underlying colour needs to be blocked out.  You may find tooth whitening is the only treatment needed.