Here's What You Need to Know

What they are: A series of clear plastic retainers, called aligners, that fit over your teeth, gradually straightening them. Each aligner is worn for two weeks at a time. (The number of aligners worn depends on how crooked the teeth are.)

Best for: Straightening teeth without a mouthful of metal. Invisaligns aren't recommended for people with extremely crooked teeth or a severe bite problem; in those cases, traditional braces are more effective.

Do they work? Yes. It can take anywhere from three months to two years to get final results (and longer if you aren't consistent about wearing your aligners). But because the aligners are removable, it's easier to eat, floss, and brush than with metal braces.

Cost: $7,000.