SPRINGFIELD, Mo. -

Dentists say they see a growing number of people whitening their teeth.  In fact, every year, Americans spend some $1.4 billion on over-the-counter whitening products.  Dentists say, however, there is a white that is too white.

Million dollar smiles used to be reserved for Hollywood stars, but now just about anybody can get one for a lot less.  From do-it-yourself boxes you can take home, to a trip to your dentist to have that professional touch, whitening is big business.

"As my mom says, everything in moderation," said Dr. Steve Dove.

D-I-Y or otherwise, too much of a good thing is not a good thing at all.

"You get that translucency of the enamel," Dove said.

People who overdo it are sometimes referred to bleachorexics, and the results are nothing to smile about.

"Because the back of your mouth is dark, and your teeth are translucent, that would make your teeth look darker than they are supposed to be.  So you're trying to whiten them, but, in all actuality, you're actually darkening them," Dove said.

The damage of overdoing whitening is irreversible.  Those pearly whites can become thin, and grayish blue looking to the point you can almost see through them.

"Making sure you take care of that foundation is super important." 

Dove, who works at Northside Dental Clinic, says getting to the root of the yellowing problem is key.

"Is it because of cavities in your tooth, is it because of food, is it because of a crack in your tooth, is it because of a dead tooth?  And all of those reasons can cause darkening of your tooth," he said.

Dove says the hydrogen peroxide solution is not for everyone.

"Your natural teeth will whiten, but the rest of your crowns and veneers will not."

As you'd imagine, he says professional is best.  The home kits, he says, can leave some parts of each tooth untouched.

"In between the teeth, you will see a little bit darker than you will the rest of the tooth.  So, with the custom trays that we make, that gel is able to get everywhere."

Dental hygienist and teeth bleacher Amanda Smith says she thinks it would be hard to overdo it.

"It just makes me sensitive.  I know a lot of patients it does this, too.  If you do it quite a bit, you'll know it, you'll feel it," Smith said.

She moved from D-I-Y kits in college to professional grade once she was in hygiene school.

"A wedding, a graduation, there's usually an event because it is purely aesthetic, purely cosmetic," she said.

"The media says have beautiful teeth and we see that in movies, and that is what everyone wants, but if it's compromising the health of your teeth, it's not a good thing," Dove said.

Over-the-counter products cost around $50.  Professional cleaning at a dental office usually costs around $200 - $300.  Dentists say it is best to keep the whitening product only on the teeth, because, if it touches the gums, it can cause damage and cause the gums to recede.

If you get your teeth professionally whitened, dentists say they have other products they can use that will help with the sensitivity.