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.
A number of different bleaching techniques and products are available to patients. Your dentist will use one of these two methods to whiten your teeth: Vital bleaching is done on living teeth and can be used to whiten your teeth if they have become stained by food or tobacco, or if they have become dark with age.