Enamel is a tooth's outside, translucent coat. While enamel can become stained, it's the layer below the enamel, the dentin, that dictates the tooth's color.

Dark liquids and acidic substances are known to contribute to tooth stains, because the acid weakens tooth enamel, allowing the pigment to seep in.

The Egyptians valued white teeth as a sign of wealth and beauty.

About 4,000 years ago the Egyptians began to whiten their smiles with a mix of ground pumice and wine vinegar.

While whitening chewing gum won't get your teeth as white as other products, studies show that gums containing CPP-ACP, an ingredient derived from milk protein, can help keep your smile bright and white.

Teeth with a yellowish hue respond best to whitening because the yellow tint is usually caused by food stains, plaque build-up and aging.

Actually, depending on the shade of lipstick you choose, it can help make your teeth appear whiter. Choose shades that are blue-based pinks and reds to play up your pearly whites.

Urine was once thought of as a good tooth whitener. It's the ammonia content in it that does the trick.

Fluoride strengthens teeth and keeps cavity-causing bacteria at bay, but too much of it may cause spots, stains and weakened enamel.

Potassium hydroxide, also known as lye, is a common ingredient in soap, biodisel, batteries, disinfectants and some cosmetics.

Crunchy fruits and vegetables are naturally abrasive tooth polishers, and they also help to produce saliva which keeps your smile white.

Yes, there is such a thing as too white. Overuse of over-the-counter tooth whitening products can cause teeth to look blotchy.

Flossing removes particles and plaque build-up between teeth, making your smile appear whiter.

Strawberries contain plaque-busting vitamin C and malic acid, which helps lift surface stains from teeth.

Bleach-based tooth whitening products are best for people with healthy teeth and gums and who have no dental restorations, but natural stain-removing methods are often safe for most mouths.

Mouthwashes that contain chlorhexidine, an antiseptic, may stain teeth when they react with tannins found in colas, red wine, coffee and tea.

While over-the-counter whitening products may cause temporary sensitivity, some natural alternatives are highly abrasive and, if used too often, may damage tooth enamel.

It's the calcium and phosphate in dairy that help to remineralize tooth's enamel, helping make teeth whiter. Milk, yogurt and some whitening chewing gums also do the same.

Tea, including green and other non-black varieties, is a teeth stainer, not a teeth whitener.

In addition to washing away stain-causing foods and liquids, saliva also contains calcium and phosphates to help strengthen tooth enamel against acidic foods, making enamel less susceptible to discoloration.