I had my teeth whitened at the dentist in 2004 and every since my teeth have been to sensitive to whiten.. I use a crest strip 1 time and the next day im in so much pain that the next application is out of the question! I called my dentist awhile ago and he said there is an enamel building tooth paste available to help be build the enamel making the teeth less sensitive. Have yall heard of this? Any other opinions? I use sensodine enamel building tooth paste twice/day and have been for awhile but it hasnt helped.