lola32

Very good question but a possibility is that maybe the nerve in the tooth has died which will sometime create that gray hue. This could have been caused by some form of trauma to the tooth ie: getting hit in the mouth, etc. and could have happened years ago. Only your dentist can tell you for sure. And I have to tell you, i have been in the dental field for several years and I would suggest that if you do bleach your teeth, stay away from ZOOM. It is a process that has been touted by "hollywood" dentists as a quick alternative to regular bleaching. The research just isn't out there to support the long term results. With ZOOM the teeth are whitened using uv rays on a blue spectrum which can create enough heat to do damage to tissue. They have to put a gel covering over gums to protect them during these treatments. If it is that dangerous to gums, what is it doing to those delicate nerves inside your teeth? i have attended numerous seminars on the dangers of ZOOM and talked with several people who've had this treatment and ended up with white teeth and increased sensitivity and root canals and dead gum tissue etc... Do it the old way, takes longer (3 weeks) costs less and rarely any side effects. Not to mention that you can control the amount of bleaching so that you may avoid over bleaching.