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.
In-office whitening or professional whitening is the most predictable and effective way to whiten your teeth when followed by an at-home whitener for 7-14 days. The whitening results in the office need to be stabilized by a high frequency at-home technique where the real whitening takes place.