• Yellow or discoloured teeth can be caused by poor oral hygiene, food causing stains such as red wine, turmeric, coffee or tea, and due to age.
• Do seek a professional opinion to understand the cause of your yellow teeth.  Sometimes a good scale and polish would do the trick!
  Occasionally you may need whitening with hydrogen peroxide gels to regain the colour of your teeth.
  Your dentist will be able to help you with that.