Regardless of how well you care for your teeth, it is inevitable that, over time, some yellowing or discoloration will occur. The gradual change can be caused by aging, substances that stain your teeth (such as coffee and tobacco), excessive fluoride, or the deterioration of a tooth's nerve. A tooth whitening treatment can be performed either as an at-home, dentist-supervised process or in the dentist's chair. Whitening is an immediate way to improve your smile and make you look years younger.