There are many causes of tooth discoloration. The most common include genetics, aging, consumption of staining substances (smoking, coffee, tea, and colas), tetracycline (antibiotic) staining, excessive fluoride, and old fillings. Whitening toothpaste can remove stain that is on the outside of the teeth. Dentists call this extrinsic staining. However, whitening toothpaste and professional dental cleanings will not change the color or intrinsic staining of the teeth. That is why tooth whitening (sometimes called tooth bleaching) is so popular.