There are two main ways that your teeth become whiter.
Over time your teeth pick up surface stains. Whitening toothpastes as well as the polishing they do in dental offices removes these surface stains from teeth and results in a slightly lighter appearance. In general, most people shouldn’t use whitening toothpastes. They are much more abrasive than regular toothpaste and can actually lead to you brushing away your enamel over time! You can’t replace lost enamel. If you want whiter teeth, stick with bleaching products instead…
Bleaching uses various peroxides to remove surface stains as well as deeper stains within teeth. The two main ingredients that are used are hydrogen peroxide or carbamide peroxide in varying strengths. The peroxides in these chemicals are very unstable and break apart into highly reactive oxygen molecules. These oxygen molecules react with the complex organic molecules that are responsible for the stains in your teeth. As they break apart and lift away these stain molecules, your teeth whiten. The temporary sensitivity that results from whitening is also a result of these peroxide molecules lifting away some of the material (dentinal plugs) within the microscopic tubules in your teeth. This doesn’t damage the teeth in any way and the tubules accumulate these dentinal plugs again about a week after finishing whitening. You can speed along this process by using prescription strength fluoride toothpaste, fluoride rinses, or sensitivity toothpastes for several weeks before whitening.
Generally the higher the concentration, the shorter amount of time you need to use it. Some products are left on the teeth for 30 minutes to an hour and others are left overnight. If you have trays that seal well, overnight with a lower concentration bleach is recommended. This reduces the risk of causing peroxide burns on your gum tissue and generally gets better results.
The difficulty in whitening teeth is that your mouth is constantly producing saliva. This saliva washes away and dilutes the bleaching solution and makes it ineffective over time. This is the reason that at home whitening products take more time to work than professional products. The at home strips just don’t seal as well around your teeth and the bleach is washed away more quickly. Custom dental trays help seal the bleach in and allow it to work longer. The better sealed the trays, the better the results.