1 concentration gradient The difference in the concentration of a chemical across a membrane. 2  cytoplasm The living substance inside a cell (not including the nucleus). 3  diffusion The movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration.
Not all stains can be lightened by over-the-counter or professional bleaching, and your dentist will be able to give you guidance. If you have sensitive teeth, gum disease or teeth with worn enamel, your dentist may discourage tooth whitening.
Tooth bleaching is a fast and convenient way to whiten your teeth for most patients. Before starting your treatment, make sure your dentist does a complete exam including x-rays first. Certain types of tooth stains, dental fillings, and crowns will not lighten with bleaching.