Like more and more consumers, you might want to whiten your teeth, a process that can be done safely and, for many, works well.

Teeth generally become yellow or gray with age. Staining often results from exposure to foods such as blueberries; beverages such as coffee, tea, cola, and red wine; and tobacco. These near-surface stains are generally quite treatable. Yellowish teeth are typically easiest to whiten, brownish-colored teeth more difficult, and grayish-hued teeth the most difficult to improve.

Stains deep in the tooth may result from the use of tetracycline (and similar antibiotics such as doxycycline) while teeth were developing or use of minocycline by adults; deposits of metal ions from adjacent restorations; and many other causes. Teeth with deeper stains are less likely to benefit from whitening, although improvement may be possible.

Excessive exposure to fluoride while teeth are developing—for instance, when a child regularly swallows toothpaste—may produce chalky white areas on tooth surfaces or, in extreme cases, brown staining. This brown staining might be improved somewhat by whitening. Bleaching the non-chalky areas might diminish the contrast between chalky white areas and the remaining tooth surface.

For stains produced by structural damage, or defects that will not benefit from bleaching, covering teeth with a veneer or bonding or capping may be the only appearance-improving solutions.

Be aware that whitening will not affect most restorations—including caps and fillings made with resin composites. If such restorations are on the fronts of visible teeth and matched to the current color of natural teeth, the whitened natural tooth surfaces won’t match areas of restoration, and you may have to resort to veneers or dental bonding.

Regular brushing and the polishing during regular cleanings will prevent or remove some surface discoloration, but significant whitening requires more than surface treatments.

The quickest and most expensive whitening treatments are performed by the dentist who paints whitening gel onto your visible teeth and then may activate it by shining light on them. A slower but less expensive option is a dentist-assisted at-home treatment in which a dentist fits your teeth with a plastic tray that you load with whitening gel and wear for several hours every day or night for a period of days or weeks. In another dentist-assisted option, instead of using gel in a tray the dentist gives you tape-like whitening strips to apply at home to your visible teeth. The least expensive—but least predictable—option is to eschew a dentist’s assistance and buy either whitening strips or gel with some type of tray-like application system at a drugstore. When the right materials are applied for a sufficient period of time, any of these approaches can be effective.

Unfortunately, your newly pearly whites won’t stay pearly forever. In most cases a “satisfactory” level of whiteness usually lasts one to three years, and sometimes more than seven years, but you are likely to partially lose whiteness within a few months—especially if you continue consuming the same foods, drinks, or tobacco products that caused the initial discoloration.

If your teeth become unacceptably less white, you can re-treat them—either with a dentist’s assistance or on your own. One advantage of the dentist-fitted, tray-based system is that you can keep the tray and buy more gel either from your dentist or from an online supplier.