(FORTUNE Small Business) – Parents, brace yourselves. Your kids are still sporting their baby teeth, and you were thinking happily that the only one tugging at your wallet for the next few years would be the tooth fairy. Wrong. Think again. Think orthodontia.

Mere grade-schoolers are sporting tin grins these days. That's because orthodontia has undergone some major changes in recent years. Wearing braces used to be a rite of passage for teens, after their permanent teeth had come in. Now children as young as six are getting orthodontia. These days it's a two-step process that begins with reshaping the facial bones.

There's good news and bad news in this. The good news: With early treatment, your child's teeth are far less likely to drift back toward their old, crooked positions later in life. That has been a problem for baby-boomers who endured years of tinsel teeth as teens only to find themselves snaggletoothed once again in middle age. (There's news for these and other adults too. But that's another story.) The bad news: the bill. Straight teeth for your child can cost as much as $7,000.

If it's any comfort, there's science behind these changes. Most dentists now realize that poor bone structure is the bigger problem behind crooked teeth. So a perfect smile begins with early treatment to re-form poorly aligned jaws. Back in dentistry's Dark Ages--about ten years ago--orthodontists and dentists used to yank teeth out to relieve overcrowding. Now most experts regard a healthy tooth as too precious to pull unless absolutely necessary.

Reshaping facial bones is relatively easy in young children. The ends of their bones are still growing and can be manipulated almost as easily as modeling clay. Early treatment may call for a child's jawbone to be lengthened or her palate to be stretched. Sound gruesome? It isn't as violent as it seems.

To widen the upper jaw, a young child is fitted with a spring-loaded metal device called a palate expander that hugs the roof of the mouth (the palate) and attaches to the molars. Once or twice a day the expander is cranked a fraction of a millimeter wider, typically by the parent, with a little key. The expander pulls apart the boundary between the two bony plates that form the palate. As the child grows, the body fills in the gap with bone, leaving room for adult teeth.

Similar devices can be used to widen the lower jaw. And to lengthen a jaw that is too short, there's some really weird-looking but effective headgear. In any case, early treatment to reshape facial bones generally lasts a year or two. When the jaws are realigned early, permanent teeth have a better chance of coming in straight. Orthodontia, part one, typically costs about $3,600.

After the bones are reshaped, some children will be fitted with traditional braces for a year or two. But sometimes early treatment does the trick. Mairead O'Reilly, an orthodontist in Annapolis, says a significant number of her patients don't need braces as teens.

Not all doctors favor early treatment, but these traditionalists are a shrinking minority. Experts advise parents to have their children seen by a dentist for a general checkup by age three. If early treatment is recommended, get a second or third opinion. You may want to scrimp on the tooth fairy. You're going to need the money.