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.
The baking soda is gentle enough to slough off the stains without damaging your tooth enamel, and the hydrogen peroxide is a whitening agent that's found in many commercial tooth-bleaching kits. Make sure to check with your dentist before using this treatment, as it may damage veneers and crowns.