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.
Some products are used twice a day for 2 weeks, while others are intended for overnight use for 1-2 weeks. If you obtain the teeth bleaching solution from your dentist's office, they can make a custom-fitted tray for you that will fit your teeth precisely. Take-home teeth whitening kit cost: $150 to $400. TEETH WHITENING BASICS A whiter, brighter smile is beautiful-it can help you feel better about yourself and make a memorable impression. Extensive research and clinical studies indicate that whitening teeth under the supervision of a dentist is safe.