Thinking digital?

Intraoral radiographs are essential to perform quality dental therapy. Teeth can be cleaned and polished without seeing radiographic images below the gingiva, but "dentistry" cannot be performed properly.

How can a diagnostic film be obtained? Intraoral film is exposed with a standard veterinary whole-body system or a dedicated dental unit and processed either manually in hand tanks or by an automatic film processor.

Alternately, a digital sensor instead of film may be exposed, allowing the images to be captured and viewed directly on a computer screen. This way is easier, economic and in many ways more diagnostic compared to the "analog" film methodology.

Making a conversion to digital is up to each practice owner. However, my experience is that it makes sense. It's rewarding to see enlarged images within seconds on a 17-inch monitor. Electronic processing and enhancement allow more diagnostic information to be extracted from the image. Digital images are easily saved in a variety of formats for insertion into the client file, to be e-mailed or used in a report given to the client. Archive image storage on the computer's hard drive is automatic and takes up no physical space or a technician's film-sorting time compared to film storage.

Digital radiography sensors are positioned using parallel and bisecting-angle technique.

•Understanding digital formats

Digital technologies available for dental imaging fall into two basic categories: photo sensitive phosphor (PSP) plates and digital imaging sensors. PSP technology uses an X-ray sensitive plate that replaces film. It is exposed by the X-ray unit, and placed into a scanning device, which records the latent image and converts it to a digital file in a computer within 45 seconds. While the plate is relatively rugged with less size restrictions, it must be handled in light-safe conditions similar to film. The plates need replacing after 50-500 exposures depending on the manufacturer at a cost of about $25.

Digital imaging sensors are wired directly or employ wireless (Schick) technology to communicate with the computer. The image can be viewed on-screen within seconds without additional handling or processing. The original sensors used a charge-coupled device (CCD) combined with a scintillator to produce an instant image. The process was termed RadioVisioGraphy (RVG). RVG was designed for "operative radiology" in human dentistry rather than to replace the full-mouth series of film images. During the past two decades, there have been five additional versions of the RVG — the most recent (Kodak RVG 6000 digital radiography system) is based upon a complementary metal oxide semiconductor (CMOS). With CMOS, high-efficiency, low-noise images are produced, which then are digitized and transmitted to a computer via a standard USB port. AFP Imaging, Bio-Ray, Kodak Dental Systems, Progeny, and Schick represent popular system manufacturers on the market.

•Digital essentials

If you decide to go digital, what will you need to get started?

This oral survey helps the clinician assess the dental health of this patient. This survey depicts the maxillary teeth above mandibular teeth.

A dental X-ray unit is required to expose the sensor. Traditional AC units are adequate, but if the veterinarian is purchasing all new equipment, DC generators produce a homogeneous X-ray beam that works best with the sensor. Because the amount of radiation necessary to produce digital images are less than traditional film, old dental X-ray units might need to be replaced.

A desktop, tablet or laptop computer in the treatment area captures and displays the images. The sensor is portable between treatment tables, but it must be able to attach to a USB port easily unless a wireless system is used. Many computers have USB ports in back, sometimes making it impractical for computers housed inside cabinets. If needed, USB-powered hubs with 6-foot wires allow the USB outlet to be placed in a more accessible location.

The digital sensor replaces film in the patient's mouth. Sensors are available in three sizes similar to film numbers O, 1, 2. Parallel and bisecting angle technique is used to position the sensor properly. The operator chooses the tooth or quadrant to be exposed from software downloaded into the computer. Images can appear on the screen within seconds.

digital dialect

Image quality is equivalent to traditional dental films. The software allows a variety of options for enhancing and manipulating the image for greater diagnostic value. The tools used most often include enlargement, auto contrast, grayscale resolution, spotlight features, inversion of colors and measurement rulers.

•Many choices

There are more than 20 dental digital vendors. It is difficult to compare apples to apples. One element common to all systems is the achieved resolution based upon line-pair discrimination (lp/mm). Differences in lp/mm affect image quality as the image size is increased. The human eye views 10 line pairs per millimeter. Other parameters to consider are sensor size, numbers of pixels in the sensor, pixel size, active image area and readout time.

This digital image shows the radiograph sensor in position.

The most commonly used systems in veterinary medicine include:

• AFP EVA-Vet is a popular veterinary digital dental radiography option. The EVA-Vet produces 16 line pairs per mm resolution. The unit comes equipped with ProImage software, which has undergone improvements and upgrades since coming on the market. Free software upgrades are given to clients. Additionally, the product can be integrated with other image software suites such as Apteryx or TigerView.

• BioRay Dental Intraoral Digital X-Ray's (from Dentalaire) sensor is considered the thinnest on the market at 3.4 mm. The BioRay comes equipped with the off-the shelf Apteryx software.

• The DEXIS CCD sensor yields an image size equivalent to a No. 2 human film. DEXIS offers a full version of the software for specific use by veterinarians (private practices, universities and government agencies) complete with canine and feline teeth numbering. DEXIS also offers image scanning, camera and extra-oral X-ray interfaces, and advance report-writing capabilities.

• Kodak RVG 6000 digital radiography system includes an exclusive superCMOS optical-fiber sensor technology yields true image resolution of greater than 20 line pair per millimeter, the highest resolution of any digital radiography system in the industry. This claim has been validated by independent non-profit dental products testing laboratories. The RVG system also comes equipped with software that enhances diagnostic abilities. An in-line sensor remote control allows for convenient capture. With high-speed USB 2 technology, images are displayed in seconds.

• Progeny MPS Digital X-Ray system is a direct carry-over from the human market. It has a theoretical line pair resolution of 23 lp/mm, which is outstanding.

• Schick CDR (without software) sensor is another direct carry-over from the human dental market, and it is a leader in human digital dental technology. They also have developed wireless digital sensor, which provides ease of movement but can be complicated by theoretical outside interference from other electronics.

•Some considerations

At one time I recommended veterinarians get accustomed to hand-processed film, then purchase an automatic film processor when their dental practice grows and finally convert to digital if warranted. Now, it makes more sense to cut out the film and processing steps. If you were going to buy a camera now, most would not buy a film camera even though it might be less expensive initially. The same reasoning applies to dental radiology.

The choice is yours. Dental radiology is important to dental care, and new technologies are making it easy and economical to bring this valuable asset into your practice.

Dr. Bellows owns Hometown Animal Hospital and Dental Clinic in Weston, Fla. He is a diplomate of the American Veterinary Dental College and the American Board of Veterinary Practitioners. He can be reached at (954) 349-5800; e-mail: dentalvet-@aol.com.