discoloured upper front teeth could be a result of a trauma that happened years ago. don't neglect it as it doens't give any symptoms for years . all we have to do is a root canal treatment which will rescue the tooth for years to come. if ignored it does react as bodies immune system recognise the injured tooth and put up its defense against it causing pain and fistula formations and later a cyst . all these make treatment process difficult. kindly visit your best dentist nearby or contact Lakshmi dental care , porur for making an appointment if you have a tooth changing its colour .