Digital Exposure

July 1, 2000
In a world of instant messaging, instant replay, and instant gratification, we can now add instant X-rays. Oh sure, we could always speed up the automatic processor in a pinch or hand dip a film through the developer solution and swish it in fixer when hard-pressed for time, but the film was practically unreadable. Now through the digital "magic" of computers, we can have X-rays appear on a computer screen as soon as we activate the X-ray beam.

Digital imaging hints at a truly remarkable future, but is the future now?

Cathleen Terhune Alty, RDH

In a world of instant messaging, instant replay, and instant gratification, we can now add instant X-rays. Oh sure, we could always speed up the automatic processor in a pinch or hand dip a film through the developer solution and swish it in fixer when hard-pressed for time, but the film was practically unreadable. Now through the digital "magic" of computers, we can have X-rays appear on a computer screen as soon as we activate the X-ray beam.

Why digital X-rays, especially when studies and sales show traditional dental film has never been more popular? In a retrospective study published in Radiology magazine, X-ray film sales increased 57 percent in the decade 1970-1980. In 1980, there were 101 million dental X-ray examinations. Film sales are still strong today. "We sold more dental film last year (1999) than ever before," said Richard Brown, U.S. and Canada marketing manager for dental business at Eastman Kodak Co. Brown estimates that only about 4 percent of dental images in the United States are currently being shot in the digital format.

"I`m not saying digital isn`t growing," Brown said, "but that it`s impact on our business hasn`t been noticeable."

Kodak continues to dedicate much of its vast resources into traditional analog X-ray technology. They have just released a faster "F" speed dental film in Europe which will be available in the U.S. market this summer. Kodak reports the new "F" speed film is 60 percent faster than "D" speed and 20 percent faster than "E" speed dental film.

"We see a long life span ahead for films," said Brown. He predicted that dental offices will still be purchasing film packets and chemicals in 20 years.

A sensor`s sensitivity

Digital X-rays aren`t totally new to the dental scene, but they have improved dramatically during the past few years.

The three types of digital imaging include scanning, phosphorus, and direct. Scanning means taking a regular (or analog) X-ray, developing it the usual way, and then scanning it into a computer for a digital image. This produces a digital copy of the X-ray, but it offers no practical time or dollar savings. In addition, the quality of the resulting image is poor.

Another method called computed radiography uses phosphorus sensors placed in the mouth that capture a latent image of the X-rayed area. The sensor is then "developed" by a laser which prints on the computer screen. Although faster than regular X-ray developing, it requires between 1 minute, 44 seconds and 1 minute, 50 seconds before the image appears.

Direct intraoral digital imaging uses an electronic sensor, which is stiffer and thicker than a film packet. The sensor is connected by wire directly to a chairside computer. The sensor is placed in the mouth and activated by the office X-ray unit. The software almost instantly displays the image on the monitor.

Instant imaging is one of the most obvious positive features of digital imaging equipment. Research reports say it takes more than six minutes to create a viewable image with a standard X-ray, compared with two to five seconds with digital radiography. Instant digital imaging is an advantage to endodontists, implantologists, and oral surgeons because a good, diagnostic quality, instant image will speed up production.

Extraoral direct digital imaging systems, using panoramic X-ray machines, are also beneficial. Some systems, such as Instrumentarium Imaging Corporation`s Ortho-TACT (tuned aperture computed tomography) attachment, can produce a three-dimensional computed tomography (CT) quality image, as well as two-dimensional slices with clear alveolar bone details using the same radiation dose as a digital periapical film.

According to Gordon Hagler, vice president of business development for TREXtrophy, digital images are more than just fast or a novelty. More importantly, digital imaging is a diagnostic tool that offers features you cannot achieve with conventional X-ray film regardless of how good the film image is.

"Instead of a conventional 11/2-inch x 2 1/2-inch image on film," Hagler said, "you can take that same image and put it on a 15- or 17-inch monitor screen. Once the image is captured, it can be enlarged or enhanced with various filters to screen out noise. The doctor can magnify the entire image or a section that is in question. The doctor can view and chart bone density, colorize the image to show even more detail, cross section the image, plus many more diagnostic features - all with the click of the mouse. None of these features are available with film."

A minute here, a minute there

Dental offices using digital systems report that patients are fascinated with seeing their X-rays on the monitor screen. They also report the patient education possibilities are remarkable. Patients could be more involved in their treatment consultation if they can see the image clearly for themselves. Patients claim the sensor is not uncomfortable even though it is larger than a film pack. A print can be made for the patient to take home.

Some systems can integrate the use of the intraoral camera with the digital X-rays and put the images on the screen simultaneously. Some also allow transmission of X-rays via modem to insurance companies or specialists.

Staffs and doctors claim more productivity since treatment is not interrupted for film opening, loading, unloading, and mounting.

A recent laboratory study at the Royal Dental College at the University of Aarhus, Denmark, indicated that a good quality intraoral digital X-ray image is as accurate as dental film for caries detection. Hagler said caries detection is a great example of why a practice needs digital radiography as opposed to film.

"The obvious caries are easy to diagnose for film and digital images, but what about a gray area you see on the mesial or distal of a tooth, and you are not sure just what it is?" he said. "With digital radiography, you can use various diagnostic tools in a matter of seconds to confirm if the area has caries or not. So with digital radiography, you can use all of the diagnostic tools with the click of a mouse in seconds to confirm or dispute a doctor`s educated diagnosis. When you use only film, none of these tools are available to the doctor."

Digital image quality can be affected by the type of system purchased, improper placement of the sensor, or incorrect unit settings. Film image quality can be affected as well by incorrect unit settings, plus stray light exposure, weak or improper chemicals, or poor handling. These issues are not a problem with digital imaging. If necessary, a retake can be made without the sensor being removed from the patient`s mouth.

The paralleling technique is used to place the sensor. Some users find it necessary to adjust their technique slightly to take good digital X-rays. Users say to expect frequent retakes while learning how to perfect placement for the individual system. Some systems provide Rinn-type holders for more effective placement.

A mere dose of radiation

Manufacturers of the new digital equipment also tout reduced patient radiation exposure compared to traditional films. One company claims their system allows a 90 percent reduction in radiation when compared to conventional film X-rays.

Clinical Research Associates, a nonprofit research group in Utah, tested digital radiography equipment to discover what amount of radiation savings were actually realized. While confirming radiation is reduced with direct digital imaging by as much as 22 to 82 percent, CRA`s September 1999 report said, "However, dental X-ray dosages are already much lower than they were in the past and significantly lower than other common sources of X-ray exposure (medical imaging). It is debatable whether or not the small reduction afforded by digital systems represents a significant benefit."

Other benefits cited by the manufacturers of the digital systems include:

- No chemicals to buy or dispose of.

- No film or X-ray mounts to buy.

- An obsolete darkroom.

- No contaminated film packets to deal with. Infection control protocols include disposable sheaths which fit on the sensors and then chemical disinfection for the sensors themselves. Most sensors cannot be autoclaved or heat sterilized.

When will prices fall?

Since some manufacturers claim digital imaging is superior to traditional films in diagnosis, why isn`t every dental office dumping their chemicals and tossing film packets to the wind? A few of these claims have aroused the giants of the imaging world. The largest, Kodak, has entered the digital fray not as a competitor (yet) but in legal wrangling and as a voice of caution to potential purchasers of the expensive equipment.

Kodak`s Brown admits that, in the beginning, the dental film industry basically ignored the dental manufacturers who touted their digital equipment. But when these manufacturers began making "fairly specious claims about their equipment and making false and misleading claims about my product, things changed."

One bone of contention was that digital imaging offers 256 shades of gray and was proclaimed superior to what dental film offered. But Kodak proved that dental film offers an infinite number of shades of gray in a continuous tone from pure white to pure black.

Since Kodak enjoys the lion`s share of the film business, why hasn`t it entered the dental digital imaging market? It`s just a matter of time. Brown feels the future of digital imaging in dental offices is very bright. Brown said Kodak is the world leader in all aspects of X-ray technology. The dental field is no different from medicine and digital photography in greatly benefiting from the technology.

"The technology is not there just yet," says Brown, "but there will come a time when there will be a large amount of direct dental digital imaging in one form or another. Will Kodak have a dental digital product? Absolutely. Are we working on it now? Absolutely. But the downside of being a market leader is that we can`t afford to put out a product that doesn`t have the quality that people expect from Kodak. We enjoy a predominant market share because we sell a good product. We feel there is a very important role for digital to play in dentistry, but the technology is not right for this business at this time."

The biggest obstacle appears to be the current high price of the digital equipment. According to TREXtrophy`s Hagler, the average price of a complete system for a single operatory can range from $6,500 to $10,000. If the office does not already have computers, you can add another $1,500 to $2,000, depending on features.

The digital sensors can be the major part of the total expense of a digital unit, and many are fragile. They can range in price from $2,500 to $7,000 each depending on size and quality. A panoramic sensor falls in the range of $17,000 to $20,000. TREXtrophy offers extended warranties on sensors after the original two-year warranty expires and can be renewed annually thereafter.

Many equipment manufacturers point to the slashed costs associated with film, chemicals, mounts, film processors, repairs, and the time and labor of someone to process the film. They also emphasize the time saved for both patients and doctors. The system pays for itself over time, according to proponents of digital systems. Hagler added, "In one year, we estimate an $18,000 return on investment if an office is taking between 45 and 50 images a day."

But Brown cautions that the cost of the service contract, which takes over after the warranty period, is about 8 to 10 percent of the price of the equipment. "That`s about what it costs to do analog X-rays," says Brown. "The price point needs to be below where it is now. A dental office is a small business. The dentist is spending his own money to buy equipment. You already have the equipment required for analog X-rays in the office, and for a new office, the upfront investment for analog X-rays is a lot less than digital."

Digital dental imaging appears destined to become a powerful force in diagnosis and treatment of dental disease now and in the future. Many upgrades to the current systems can be expected, as well as consolidation of some of the equipment manufacturers. Maybe the film and digital technologies will be able to co-exist in the office, and patients and staff will benefit from the best each has to offer.

Cathleen Terhune Alty, RDH, is a frequent contributor to RDH. She is based in Clarkston, Michigan.


- Dental Clinics of North America Journal, April 2000 www.ncbi.nlm.nih. gov/PubMed

- Clinical Research Associates, Sept 1999

- Trophy Radiology

- Eastman Kodak Company

- Instrumentarium Imaging

- Schick Techologies, Inc.

- Journal of Dental Hygiene vol 71 (2) 71-75, March-April 1997 www.DHNet

- Provision Dental Systems, Inc.

- Dentrix Internet Users Group;

A hygienist`s view

Hygienist Joanne Forbes works at in a New York City office that has been using a digital imaging system for about one year. She values the system because of the reduced radiation to the patient and the instant image. "I can see immediately if I shot the area that I wanted to see. I use the contrast feature which allows me to lighten or darken the image, or I can press a button and colorize the image so the different densities are visible. You can actually see color changes in the enamel because of the changing thickness due to tooth decay."

For hygiene diagnosis, Forbes said you can more easily see the bone height and calculus shows up very clearly. She also mentioned how easy it is to print copies of a film and that her patients seem to like it.