Breaking Down Today's Radiographic Systems

“The choice of what type of system to buy will depend upon what type of practice a dentist has,” explains Allan G. Farman, BDS, PhD, MBA, DSc, a professor of radiology and imaging science in the department of surgical and hospital dentistry at the University of Louisville. “The selection of the type of equipment that will be necessary will be heavily predicated on the type of practice, the scope of the practice, and the ambition of the practitioner.”

Donald Tyndall, DDS, MSPH, PhD, FICD, an oral and maxillofacial radiologist at the University of North Carolina School of Dentistry, concurs with Farman, saying that the right choice depends on the task of the clinician. “Depending on if you’re looking for periapical lesions, caries, periodontal disease—a variety of dental problems—most clinicians would use intraoral imaging. Panoramic imaging is more useful for general observations.” A great deal of information can be obtained from panoramic imaging, but not enough detail can be seen for diagnosing caries or small lesions in the bone.

Another option that is fairly new is the “panoramic bitewing” to be used where intraoral imaging is not practical. Tyndall says the research and scientific evidence still show that intraoral imaging produces a better bitewing for finding caries, but applauds the concept and believes research should continue in the area. “As a patient, it would be nice not to have to stick something in your mouth,” Tyndall says. “This would be very helpful when treating children especially.”

Cone beam computed tomography (CBCT) is an option for 3-dimensional (3D) imaging that complements traditional digital radiographic systems for planning implants, developing surgical guides, and much more.

According to Farman, the cost of an intraoral digital system is about $10,000 plus an additional $5,000 to $6,000 for the x-ray generator. Panoramic systems range from about $25,000 to $80,000. CBCT systems range from $80,000 to $300,000.

There are two different technologies available for 2-dimensional (2D) intraoral or panoramic digital imaging—solid state sensors (direct digital) or phosphor storage plates (PSP) (indirect digital).

For solid state imaging, a sensor with a computer chip in it is placed in the patient’s mouth and an image—via a USB or wireless computer connection—is sent almost instantly to the computer monitor. There are two types of sensors available—CCD (charge-coupled device) and CMOS (complementary metal–oxide–semiconductor). According to Dale A. Miles, DDS, MS, FRCD, either type of sensor is equally effective. “The clinical image is just as good with either. Early on, CDD had an edge, but not anymore. And, it’s cheaper to make CMOS.”

For indirect digital imaging known as computed radiography (CR), photostimulable phosphor (PSP) plates, which are very flexible and look and feel like film, are placed in the patient’s mouth like film. When the radiographic image is taken, some of the energy is absorbed by the phosphor and recorded there. The plate is then taken to a laser scanner for scanning using a solid state red laser, and the image that is released as blue light is photomultiplied and digitized for upload to a personal computer. A computer monitor is used for viewing, Laser scanning introduces an extra step compared to the use of solid state detectors.

Each technology has its pros and cons. According to Tyndall, although about 80% to 90% of U.S. dentists who have a digital system are using solid state imaging, in Europe about 80% of clinicians use storage phosphor. He also notes that most dental schools in the United States use some form of storage phosphor. PSP costs less. The cost of solid state sensors ranges from $6,000 to $10,000 each, depending on the size of the sensors. “These are expensive,” explains Tyndall. “For the cost of less than two sensors, you can buy a PSP scanner and you can use that as a processor or developer and support a whole number of operatories with one system.”

While upfront costs can be a factor in deciding which system to buy, Miles points out that it’s important for dentists to consider how quickly they’ll see a return on their investment, explaining that the biggest margins of all procedures done are seen with radiographic procedures. He suggests that clinicians go into their practice management software and run a report on productivity for 6 months to a year using all CDT codes that correspond to radiographic procedures.

“They will be astonished at the amount of dollars generated,” he says, adding that he is not advocating that dentists take more radiographs to make more money. “It just happens because we pretty well need radiographic information on most patients who walk in the door because there’s no other way of getting the needed information on bone and teeth without taking some kind of radiographic image.”

When choosing a system, Tyndall says dentists who use a dental supply company should ask what their local sales representative suggests and what systems the supply company offers. There are many manufacturers offering solid state digital systems, but only a few who make phosphor plate systems.

Another major issue is patient comfort. Solid state sensors are coated in plastic or aluminum; and they are rigid devices that can’t bend, which Tyndall says can be difficult for some patients.

“Some companies have gone to great lengths to smooth off the corners to make them more comfortable. One company has clipped off the corners, and it tends to be pretty comfortable for patients. Other sensors are not as comfortable,” Tyndall explains. "When first using sensors, training for staff will be necessary to learn how to place the sensors in the mouth, which may differ somewhat from traditional methods.”

The wire that connects the sensor to the computer is the most vulnerable and most likely component to fail, Tyndall warns, because the wires turn horizontally and vertically when placed inside a patient’s mouth and the wires move around inside the cable and can begin to break. Tyndall says some companies offer replaceable wires, so if the wire breaks, only the wire needs to be replaced and not the whole sensor. Some companies have the wires at 45-degree angles so they don’t twist as much, and other companies have the wire connect with a swivel. Miles, on the other hand, says the wire is more of a “perceived problem,” and that good technique can alleviate the problem.

An advantage to phosphor storage is that the sizes of the plates are similar to traditional film radiographs and the techniques for acquiring images are almost identical, so the learning curve is small.

However, the plates tend to get scratches. Tyndall says that in dental schools, about one-third of the plates need to be replaced every year, and estimates that in private practice, about 20% likely need to be replaced each year. This is one of the reasons Miles recommends direct digital over PSP when a practice is making the transition to digital radiography.

Image quality is another factor. From a diagnostic point of view, PSP and direct digital imaging are similar, and on par with film, but most experts agree that the solid state detectors produce a better, higher-quality image.

“PSP and solid state detectors both work well,” says Tyndall, explaining that the consensus of peer-reviewed research shows that the two technologies are equal in diagnostic efficacy, but the images with PSP just don’t look as nice.

Because most practices will have both panoramic and intraoral systems for different diagnostic reasons, Tyndall says that one of the benefits of storage phosphor is that a practice can keep its old panoramic system and just place storage phosphor plates instead of film, allowing the practice to save money while still generating digital images. “The images aren’t as pleasing to the eye,” he says, “but I don’t think there’s much difference in diagnostic ability.”

It is also possible to go direct digital with a panoramic system and use storage phosphor intraorally or vice versa. An ideal imaging solution would be to incorporate a hybrid system of using direct extraoral imaging with both direct sensors and a PSP systems for intraoral use. This enables the clinician to use the ideal technology to address the patient’s and clinician’s needs thus enabling the best quality of care.

The newest available digital radiographic technology for dentistry is CBCT, which provides accurate 3D radiographic images that can also be used for implant treatment planning and guidance and to create 3D epoxy models used for various treatment applications.

To date, Tyndall says, this technology has been used mostly for planning implants and developing surgical guides, and adds that CBCT is very versatile for finding abscesses or teeth that need root canals. He says it’s much better for this than intraoral, though it cannot replace intraoral radiography for finding cavities. CBCT is complementary to standard digital radiographic applications.

Farman also says that CBCT is a valuable tool, but should not replace traditional radiograph systems for detecting dental caries. He does not believe CBCT should be used for every orthodontic patient if good results can be obtained through traditional methods at lower radiation doses. Farman says CBCT should be used as necessary based on the individual patient needs, such as when maxillary canines are impacted. However, he adds that if he were placing implants, he would want a CBCT of the area to get an idea of the relationship of the bone to where the implant may be placed in 3D to determine whether more bone should be added or whether the implant could be placed more optimally, to plan in 3D the placement of the final restorations, and to plan in 3D the implants that would support them.

“CBCT crosses more disciplines and allows dentists to do more of the procedures they’re getting into, such as implant placement and obstructive sleep apnea,” says Miles. “The average general dentist is seeing the advantage of cone beam computed tomography.”

When choosing a CBCT system, the manufacturer’s training program should be an important consideration. According to Farman, continuing education will be emphasized with this technology because many practitioners didn’t learn about it in school. Continuing education for CBCT is required now for dentists who want to treat Medicare or Medicaid patients and be reimbursed for CBCT imaging, because CMS requires accreditation of the facility for the dentist to qualify for reimbursement. The Intersocietal Accreditation Commission (IAC) offers accreditation of dental CBCT imaging systems, and statutes in Minnesota and California will make that accreditation necessary for all dentists, says Farman.

“In fact, the American Academy of Oral and Maxillofacial Radiology and the American Dental Association have teamed up to provide the baseline or basic courses necessary for initial CBCT accreditation,” he adds.

From intraoral to panoramic to 3D CBCT, digital radiography is enhancing the practice of dentistry. Even for those who are closer to retirement than the beginning of their careers, the experts interviewed for this article all agree that it may still be worthwhile to upgrade to a digital system. Maintaining a film-based practice takes up expensive space and there are a lot of costs, such as maintenance and discarding of processing fluids, Farman says.

But no matter what system is in place, the most important thing is to image wisely, Farman stresses. “We go to dental school to acquire knowledge, and professional judgment should be used in selection of all radiographic images that are going to be provided based upon individual patient needs. Therefore, we should select the images that are needed for each particular case and minimize the amount of radiation that is needed for each case. This is particularly important when treating children because they are more highly susceptible to radiation.” He adds that the industry has done a good job in trying to minimize radiation exposure.

Decreasing radiation dose is one of the many reasons that dentists might switch from film to digital, Tyndall says. “Going from film to digital can be up to four times less radiation as long as the dose is minimized. Going from film to PSP can be two times less radiation as long as the dose is minimized.”

When choosing a digital radiographic system, the entire staff must be involved in the decision-making process from day one. Sales representatives should talk to clinicians and staff—it’s critical in making the right decision.

“Before they buy any system, whether it’s 2D or 3D, dentists should talk to people who actually own and use the system. Don’t just look at brochures, don’t just listen to the salesperson and look at the pretty images on the screen,” Tyndall says. “Always talk to your colleagues. Don’t be the dentist who spreads out brochures on a table top and then looks at them for 6 months trying to make a decision. Also, call the radiologist at the dental school you went to—it’s free advice and it’s our job to keep up with this technology.”