Call it the world's most dangerous gimmick: Dentists and orthodontists are turning to new 3-D scanners that pack more radiation than traditional X-rays.

There's no evidence these machines actually improve treatment or outcomes... but don't worry--they say children have a real blast with them.

"Kids love to see that 3-D image," one orthodontist said in a Webcast sponsored by one of the machine's makers, according to the New York Times. "They can go into our computer and look at their skull."

You'd think it's even better than a trip to the movies!

The devices are called cone-beam CT scanners, and the Journal of the American Dental Association dedicated an entire issue to the technology--and it just so happens that the issue was underwritten by one of the manufacturers.

Maybe that's why the articles offered glowing coverage of the supposedly crisp, clear images... but almost no real discussion of the clear risks that come from blasting kids with high levels of radiation.

One article even downplayed those risks by comparing the levels of radiation to the amount used in full-body airport scanners.

And while that's nothing to brag about--those machines aren't nearly as safe as the mainstream would have you believe, especially for children--it's not even true.

Dr. David Brenner, director of the Center for Radiological Research at Columbia University Medical Center, told the Times that the comparison is "very wrong — by a lot."

In fact, he said the cone-beam scanners can be hundreds of times more powerful than the airport devices.

But dentists are in love with them--and are even using the machines when other radiation-free solutions are available, such as braces that require 3-D images for placement.

There are two ways to get those images: A radiation-free digital camera, which takes about 30 minutes... or the radioactive new scanners, which can do it in seconds.

I'll bet you can guess which one orthodontists are opting for--and it's not because it's better for the kid.

It's because time is money.

One dentist mentioned in the Times article values each minute at his practice at $5. Since the machine saves 30 minutes, it saves $150 each time it's used.

KA-ching!

Over the course of 1,000 patients in a year, it's $150,000 in savings.

KA-ching! KA-ching! KA-ching!

Meanwhile, the Times also found that many dentists who use traditional X-rays still opt for slower D-speed film despite the fact that it uses 60 percent more radiation than the newer, faster film.

Digital X-rays, which are even less common, use less radiation--but if you do actually need images of yourself or your child, that's the one to look for.

And while you're at it, make sure you look for a dentist who will only use it when absolutely necessary.