On their quest to obtain a perfectly white Hollywood smile, Americans spend more than a billion dollars on teeth whitening every year. And whether they want great results instantly or noticeable results without breaking the bank, there's an option for them.

How does teeth whitening work?

Teeth can be whitened at a dental office with a professional-strength bleaching gel or at home with a less powerful bleaching gel. At-home methods include dentist-provided teeth-whitening kits with custom-molded bleaching trays and over-the-counter treatments such as traditional strips and bleaching trays that you mold to your teeth at home.

The whitening gels in all the methods work to remove staining agents that have traveled down into the teeth's porous enamel over the years. The chemical agents in the gels (hydrogen peroxide or carbamide peroxide) set off an oxidation reaction that breaks up stains.

Click here to find discounted whitening kits and strips.

What types of stains does teeth whitener treat?

Stains That Can Be Treated: Extrinsic

Extrinsic stains are on the outer layer of teeth. Over time, the enamel absorbs pigments left over from certain beverages, food, and tobacco, including:

• Coffee and tea
• Soda
• Wine
• Cigarettes, cigars, and chewing tobacco
• Berries
• Red sauces and curries

Stains That Cannot Be Treated: Intrinsic

Intrinsic stains are deeper, affecting the tooth layer that lies below your enamel, the dentin. The dark dentin color can be caused by:

• Tetracycline antibiotics
• Trauma to the teeth

Because teeth whitening won't affect intrinsic stains, your best bet for a whiter smile is covering the stained tooth with porcelain veneers.

How do I use a teeth-whitening kit?

There are two types of whitening kits: kits you get from the dentist and kits that you buy over the counter.

• How to use an over-the-counter kit: OTC kits, which tend to be cheaper, use either carbamide- or hydrogen-peroxide gels and bleaching trays. The trays can be one-size-fits all, but they're often thermoforming. If you have a kit with thermoforming trays, soften the trays in boiling water, then mold them around your teeth. Custom molds can mean the difference between getting whitening gel on just the teeth or on the teeth and the gums, which can cause irritation. Fill the trays with bleaching gel, placing only a small drop of in each tooth impression. Place the trays over your teeth and wipe away any excess gel that overflows onto the gums. Wear the trays for about 30–60 minutes once or twice per day. Follow the instructions provided for exact times.

We like the Doctor Diamond Professional Home Whitening Kit ($18.99). Beauty editor Colleen Loggins Loster used the Doctor Diamond kit a few times before her wedding and says that although it was a bit tricky to mold the trays to her teeth, her teeth were noticeably brighter after using the kit for a few weeks.

How many syringes of gel do I need?

It depends on the size of the syringe. Typically, a person will use 0.5mL (0.5ccs) of bleaching gel on the top teeth and 0.5 mL on the bottom teeth each time they whiten. For an entire treatment, they will need about 10 to 15mL (10 to 15ccs) of whitening gel, so about two large syringes.

How do I use whitening strips?

Whitening strips, such as the popular Crest Whitestrips, are polyethylene strips that contain hydrogen peroxide. To use them, remove the liner and apply the gel side to your teeth. Press the strip against your teeth and fold the remainder of the strip behind your teeth. Depending on the instructions, the strips should be worn for 5–45 minutes for 1–4 weeks.

Click here to shop for Crest Whitestrips (from $22.99).

What happens during an in-office treatment?

Dentists first clean teeth with pumice and apply a protective barrier to gums. Next, they apply a 15%–35% hydrogen-peroxide bleaching gel to teeth. They leave the bleaching gel on for several minutes, rinse it off, and then reapply it. The process is repeated a few times. Oftentimes, they use a special light to activate the solution, though studies haven't conclusively shown that a light is necessary.

Watch our video of a Zoom! in-office whitening session:

Find a Zoom! whitening treatment near you.

In-Office Treatments Vs. At-Home Treatments

In-office treatments can brighten teeth up to 10 shades in as little as one hour, whereas take-home kits generally take a few weeks to achieve similar results. Of course, take-home kits tend to be cheaper than in-office treatments.

Whitening treatments purchased over the counter are the cheapest, and they can be used right away. Plus, independent studies have shown that they are effective, though not as effective as professional systems. The other disadvantage of over-the-counter treatments is that they often don't list the strength of the whitening gel and can be ill-fitting, which can cause discomfort and render them less effective.

Will it whiten all of my teeth?

Whitening won't affect existing crowns, veneers, or fillings. With most methods, the bleaching gel is only applied to visible teeth—usually eight teeth on the top and eight on the bottom.

Should I clean my teeth beforehand?

• Professional treatment: Yes. Have a professional cleaning in the dentist's office about two weeks beforehand. A cleaning will remove builtup plaque and tartar to help the whitener better penetrate the enamel.

• Over-the-counter treatment: No, usually. Most instructions will tell you to not brush your teeth before applying a strip or trays. That's because the fluoride in toothpaste will stick to teeth and block the bleach. Additionally, whitening strips stick better to unbrushed teeth.

How long do results last?

Results last about 6–12 months, but how long your exact results will last depends on a variety of factors, including your diet and how easily your teeth stain.

Is there such thing as too much teeth whitening?

Yes, you can overwhiten your teeth and permanently damage your enamel, which can make teeth look splotchy or even translucent. To avoid overwhitening, keep these timelines in mind:

• Professional whitening: Wait about a year between treatments.

• Professional at-home kit: Wait about six months to a year between treatments (depends on the strength of the kit).

• Over-the-counter kit: Wait about six months between treatments.