By Serusha Govender

The Rumor: Using certain toothpastes and mouthwashes can regrow lost tooth enamel

You know that the key to a great smile is keeping your pearly whites in top-notch shape. The best way to do that? By taking really good care of your tooth enamel. Enamel is the thin outer covering of teeth that protects the delicate tissues inside. A lifetime of chomping and sipping can stain, chip and wear away that covering, however -- and once that happens, your teeth become extremely sensitive to hot and cold. Even your favorite sugary treats can deliver a twinge (if not a bolt) of pain.

While tooth enamel is actually translucent, teeth start to look more yellow as it wears away, because the yellow dentin underneath begins to show through. Which can leave you wondering: What can you do to get your precious enamel back? Today there are lots of products out there (from toothpastes to mouthwashes to dental guards filled with strange, squishy paste) that allegedly help restore lost enamel. But by making that promise, are manufacturers biting off more than they can chew?

The Verdict: You can do a lot to protect and strengthen your tooth enamel, but once it has eroded, it’s gone, baby, gone!

The human body’s pretty amazing: Broken skin heals; cut nails and hair grow back again; fractured bones knit together. But as amazing as the body's ability to repair itself may be, it can’t regrow tooth enamel. Ever.

Tooth enamel is the hardest tissue in the body. Problem is, it’s not living tissue, so it can't be naturally regenerated. Unfortunately, you can’t regrow it artificially, either -- not even with those special toothpastes. But chin up: Some dental products can help with the tooth-enamel issue; just not in the way you might think. "You can’t regrow tooth enamel, but you can remineralize it," says upwave review-board member Mark Wolff, DDS, a professor of dentistry at New York University. "That's what these [toothpastes] actually do... They push calcium and phosphates back into the tooth, and it hardens the enamel." The secret weapon? Good old fluoride. While acid draws calcium and phosphates out of teeth, fluoride captures the minerals from saliva and forces them back into the tooth.