So you want whiter teeth. Fair enough, but what do you know about the process of whitening them? Here are answers to some of the most pressing questions about teeth-whitening.

How white?

This is a pretty subjective question, but a lot of the answer depends on what methods you use and how stained your teeth are to begin with.
In a dentist office, the dentist can use bleaching agents and special lights to whiten your teeth, and it can get your teeth up to seven shades whiter. However, this can be expensive, even if it's one of the most effective methods.
Over the counter methods can whiten your teeth considerably, but you should consider two things. 1) You won't have as much control over the shade as a dentist would. 2) You need to make sure you're using teeth whiteners that have been approved by the American Dental Association, as teeth-whiteners that haven't been approved may be harmful to your teeth.

All stains?

Typically, most stains can be removed from your teeth. Extrinsic stains, or general discoloration of the enamel, can be removed easily with bleaching agents. However, some stains are intrinsic - the involve the darkening of the interior of the tooth. These will not be removed by bleaching and may not be removed at all. In these cases, a dentist will be able to help more than an over-the-counter whitening agent would.
Some stains are age-related. When the outer enamel thins, it allows the yellowish interior of the tooth to show through. This is the point where bleaching agents can still help, but aren't as helpful as they were when you were younger.
When trying to determine whether the stains on your teeth will come off, remember that yellow stains come off more easily than gray ones, and that newer stains are easier to remove than old ones. If you simply ate too much spaghetti sauce, a box of white strips or white trays will do the trick. If you've been smoking for 20 years, you may want to check with your dentist about your options.

Whitening toothpastes?

Some whitening toothpaste can help to keep your teeth cleaner and therefore whiter. However, there are some whitening toothpastes that use abrasion to keep your teeth white. These can damage your teeth. Be careful when choosing your toothpaste and consider just brushing your teeth effectively rather than trying to get them whiter with a strong toothpaste.

Side effects?

Most people don't experience any side effects beyond a little sensitivity, which goes away after a few days. However, with some over-the counter whitening kits, you may experience irritation of the gums due to the poor fit of trays or strips. You can minimize this by trying to keep the whitening solution off the gums, but it's always going to be less precise than in-office whitening.
Women who are pregnant should avoid tooth whitening, as the effect on fetal development is unknown.