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.
1 (Optional) Use a Desensitizing Gel to calm your the nerves in your teeth prior to whitening. 2  For the most relief, you should apply the gel to your teeth for 10 to 30 minutes before bleaching using the same bleaching trays you got from your dentist and rinse afterwards.