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Because children and adolescents are particularly vulnerable to radiation, doctors three years ago mounted a national campaign to protect them by reducing diagnostic radiation to only those levels seen as absolutely necessary.

It is a message that has resonated in many clinics and hospitals. Yet there is one busy place where it has not: the dental office.

Not only do most dentists continue to use outmoded X-ray film requiring higher amounts of radiation, but orthodontists and other specialists are embracing a new scanning device that emits significantly more radiation than conventional methods, an examination by The New York Times has found.

Designed for dental offices, the device, called a cone-beam CT scanner, provides brilliant 3-D images of teeth, roots, jaw and even skull. This technology, its promoters say, is a safe way for orthodontists and oral surgeons to work with more precision and to identify problems that otherwise might go unnoticed.

But there is little independent research to validate these claims. Instead, the cone beam’s popularity has been fueled in part by misinformation about its safety and efficacy, some of it coming from dentists paid or sponsored by manufacturers to give speeches, seminars and continuing education classes, as well as by industry-sponsored magazines and conferences, according to records and dozens of interviews with dentists and researchers.

Last month, The Journal of the American Dental Association allowed one of the leading cone-beam manufacturers, Imaging Sciences International, to underwrite an issue devoted entirely to cone-beam technology. That magazine, which the association sent to 150,000 dentists, included a favorable article by an author who has equated a cone-beam CT with an airport scan. In fact, a cone beam can produce hundreds of times more radiation, experts say.

Cone-beam CT scans can help dentists deal with complex cases involving implants, impacted teeth and other serious problems. But many experts in dental radiation have raised alarms about what they see as their indiscriminate use. They worry that with few guidelines or regulations, well-meaning orthodontists and other specialists are turning to a new technology they do not fully understand, putting patients at risk, particularly younger ones.

Some orthodontists now use cone-beam CT scans to screen all patients, even though a number of dental groups in this country and in Europe have questioned whether the benefit of routine use justifies the added risk.

“All these different cone-beam CT scanners came out to a world that was unprepared,” said Keith Horner, a professor of oral radiology at the University of Manchester in Britain, who is coordinating a study of cone-beam scanners for the European Commission.

One popular new brand of braces has helped cone-beam sales because it requires 3-D images, which doctors can obtain using either a cone-beam scanner with radiation, or a digital camera without it. Many orthodontists opt for radiation, because it is quicker.

Even those troubled by the widening use of cone-beam technology acknowledge that by itself, the risk from a single scan is relatively small. But patients often get more than one scan, and the lifetime risk increases with each exposure. Without a clear benefit, they say, there is only risk.

“So let me ask a question to the mother of a prospective orthodontic patient,” said Dr. Stuart C. White, former chairman of oral radiology at the UCLA School of Dentistry. “Would you like me to use a tool that is entirely safe — a camera — to record the position of your child’s teeth, or another method that may rarely cause cancer so that we can save time?”

The cone-beam business is lucrative for manufacturers and dentists. According to one industry estimate, more than 3,000 scanners and about 30 different models have been sold, at prices up to $250,000.

Marketers increase interest in the technology by holding drawings for free cone-beam CT scanners and other gifts. A Washington State orthodontist, who gave an online lecture sponsored by Imaging Sciences, offers dentists coupons for free scans for their patients as a way to build referrals.

And then there is the “wow” factor, said Dr. Terry Sellke, an orthodontist in Illinois.

“Kids love to see that 3-D image,” Sellke said in a Webcast sponsored by Imaging Sciences. “They can go into our computer and look at their skull.” Another orthodontist talked about coloring 3-D skulls in green and purple. “Fun for the kids,” he said.

Dr. Allan G. Farman, president of the American Academy of Oral and Maxillofacial Radiology, cautions doctors not to become overly enamored of the new technology, citing the example of how shoe stores once took X-rays of customers’ feet to see if shoes fit.

Regulators are just now recognizing how ill equipped they are to oversee this new technology. “There is not a lot of radiation exposure data out there,” said Jerry Hensley, a state radiation protection official in California.

While protocols and guidelines exist for other types of imaging, Hensley said, “cone beams are off in their own land right now.”

‘A lack of understanding’

Even before cone-beam scanners, the dental profession had problems keeping radiation levels low.

For years, dentists have been advised to stop using slow, D-speed film for X-rays because it requires more radiation than faster film. Yet, most still use the slower film, which requires up to 60 percent more radiation, according to dental experts and government records.

Brian Smith, a spokesman for Carestream Dental, the market leader in dental film, said 70 percent of its film sales in the United States are D-speed. The percentage is lower globally, suggesting that dentists elsewhere do a better job of reducing radiation.

There is no excuse for not switching, the Food and Drug Administration said, because faster films offer the same quality for only pennies more.

Dr. John B. Ludlow, a University of North Carolina professor who has published widely quoted studies on dental radiation, said he suspects that some dentists avoid faster film because they mistakenly believe it is harder to process.

A check of state dental boards found none that were aggressively pressing dentists to use the faster film. Digital X-rays use even less radiation than film, but a minority of dentists use them.

One expert in dental radiation, Dr. Joel E. Gray, said he has found as much as a 500 percent difference in radiation levels because of sloppiness in developing film, including using chemicals that were degraded or at the wrong temperature. To get clearer images, dentists compensate by increasing exposure time — and radiation, said Gray, whose company, Diquad, has contracts with three states, including California, to try to keep dental radiation in check.

New Jersey, which collects data on radiation exposure, found that 20 percent of its dental offices had high or “extremely high” radiation levels.

“There is a lack of understanding of the radiation in dental offices,” Gray said.

That has become even more important with the emergence of cone-beam CT scanners. When first introduced in the United States about a decade ago, they were viewed mostly as a cheaper, lower-radiation alternative to big, medical CT scanners that were often needed to diagnose serious ailments of the mouth and face.

But through aggressive marketing and technological improvements over the last several years, their use has rapidly expanded into other areas, including orthodontics. For many teenagers, getting scanned is now part of the ritual of getting braces.

Quick and easy

In October, 26,000 people gathered in Orlando, Fla., for the annual conference of the American Dental Association.

The presence of cone-beam CT scanners could be seen and heard at every turn. There was the 3-D imaging center, cone-beam exhibits, demonstrations and continuing education lectures.

An open forum on cone-beam imaging was co-moderated by Dr. Michael Glick, editor of the Journal of the American Dental Association. Of the four panelists, one was a founder of Imaging Sciences, another was a consultant to the company’s distributor and a third was a paid speaker for another cone-beam company.

Cone-beam scanners are quick, easy to use, versatile and do not require much space. In most models, the patient sits in a chair for less than a minute while a small scanner circles the head. Enthusiasm for the technology is echoed by dentists around the country.

Dr. Steven A. Guttenberg of Washington said he uses the scanner “for every single implant that I do.” Dr. Rik Vanooteghem of Sunnyvale, Calif., added: “I really feel blindfolded if I don’t use it.”

Dr. Bradford Edgren of Greeley, Colo., said his scanner had found hidden teeth — among other things. “I found a rock in one child’s ear,” Edgren said. “Now she can hear and her grades have gone up.”

A California lawyer, Arthur W. Curley, suggested that dentists might even face legal liability for not using 3-D imaging. “Negligence may be the failure to incorporate new technologies that meet well-defined legal standards,” Curley said in a Web presentation.

Curley, along with Vanooteghem, Guttenberg and Edgren, share more than their enthusiasm. They have all received speaking fees from Imaging Sciences.

At the ADA’s conference last month, six manufacturers spent nearly $290,000 to promote 3-D technology. And the ADA said it had accepted somewhere under $100,000 from Imaging Sciences and its sister company — a specific figure was not given — for the cone-beam supplement that came out around the time of the conference.

The company’s i-CAT scanner is one of the most popular on the market.

Farman, the radiology academy president and a professor at the University of Louisville School of Dentistry, calls the i-CAT an excellent device, but said there is not yet proof that it is better and safer than conventional imaging in all applications.

This month, the academy and the American Association of Endodontists issued a joint statement saying that cone-beam CT “must not” be used “for screening purposes in the absence of clinical signs and symptoms.”

Dr. Lee W. Graber, president of the American Association of Orthodontists, praises the technology and said dentists have worked to reduce radiation over the years. In his suburban Chicago practice, Graber has a machine capable of delivering both cone-beam scans and conventional images, but only uses the higher radiation method when necessary. “Our goal as clinicians is to try to minimize the risk,” he said.

Vatech America, a cone-beam manufacturer, does not support using its scanner as a screening device, said Travis Harrison, the company’s director of business development. “We don’t want to just dose everyone with a CT,” he said.

Imaging Sciences, a unit of the Danaher Corp., a diversified manufacturing and technology company, declined repeated requests for interviews, saying it granted such requests only to trade publications, according to Dan Gagnier, a company spokesman.