I do not know what happened but the doc tor also said also said that a poor diet causes it too which is me I only eat supper due to stress in my life after bleaching only rinse with warm water do not brush teeth put sensodyne on teeth for a half hour then brush teeth the er room told me not rinse with peroxide but I do any it helps me I also took steroide med for 2 weeks but I feel like the peroxide in the bleaching helps remember smoking is the problem too yhe doctor wants me to quit I have not quit and am still smoking but feel better I hope and pray that my theary works please let me know how you feel if you try this theary because I am right there with you!!!