Bleaching stained teeth
A patient informed me that he was interested in bleaching his 2 discolored front teeth. They had been hit when he was in high school and now he is 45 y.o. He has a root canal in one tooth and the other tooth was just gray and dark - there was marked difference between has 2 front teeth and other teeth. I informed him that bleaching was an option but its results are not predictable due to his intrinsic staining from a dead tooth (due to trauma). The most predictable option would be for him to at least get his 2 front teeth crowned with all porcelain emax crowns. He would be happiest and the results would last a long time. If he wanted to spend time and money on bleaching then he maybe disappointed.
Bleaching does work better on teeth that aren't dead or have intrinsic staining. Some teeth will take longer to get to desired results.