Digital radiography for the dental assistant.
Radiography has long been an essential diagnostic tool in managing patients' oral health in the dental practice. Dental auxiliaries play a vital role in obtaining and processing radiographs; their skills in radiographic technique render diagnostic images and their records management role ensures that those images are available to the dentist whenever they may be needed.
In the past ten years, computer and digital record management has become integral in dental practice. Some offices are entirely digital, also referred to as "paperless," while many others rely on various digital records as well as more traditional hard copy records. Dental radiography is also being fundamentally changed by the evolving digital age.
Digital radiographs are becoming more and more prevalent in dental practice. New dental offices are often designed to use digital radiographs, while others are converting from film radiography to digital. Digital radiographs can be viewed on any computer screen, manipulated to enhance contrast and detail and transmitted electronically without loss of quality.
Basic knowledge of digital radiography is essential to the dental assistant, even if he or she is not currently using the technology in their daily work routine. Chances are, at some point in the future, the assistant will come into contact with and possibly need to master basic digital radiography. The purpose of this article is to introduce basic concepts of digital radiography and contrast that information with the more familiar information about film radiography.
History of Dental Digital Radiography
The first digital x-ray sensor used in dentistry was introduced in the mid-1980s by Francis Mouyen, then a dental student at the University of Toulouse, France. Digital radiology was later introduced in the United States in 1990 after approval from the Food and Drug Administration (FDA). Subsequently digital radiology has seen rapid advancement due to introduction of many electronically readable digital detectors (sensors). At present, there are a large number of digital intraoral radiographic systems available. They can be classified into two main groups, direct and indirect radiographic systems. The direct system uses a sensor based on a charge coupled device (CCD) and the indirect uses photostimulable phosphor plates (PSP). At the present time, CCD technology is more widely used in dental offices.
Comparison: Film vs. Digital
Film has long been the gold standard for imaging in dentistry; however, there are some inherent disadvantages of film-based images. Image acquisition and processing take longer when film is used.
Darkroom processing, maintenance of chemicals and disposal of hazardous chemicals significantly add to the time and long-term cost effectiveness of film-based radiography. Direct image acquisition with digital radiography utilizes a computer to process image data, thus significantly reducing the time for acquisition of the radiographic image.
Furthermore, in film-based radiography, improper exposure or processing methods can have detrimental effects on the image quality, resulting in the need for multiple retakes thus increasing patient radiation exposure. The optical range and contrast resolution are also fixed following the exposure; therefore improper exposure can reduce the diagnostic quality of the film radiograph. In digital systems, image enhancement tools can be used to improve the quality of the image after incorrect exposure and many digital systems require a lower dose of radiation for diagnostic images than for film radiographs.
Manual handling and retrieval of film radiographs can be time-consuming compared to digital images where data retrieval is faster due to hard drive storage or on a third-party server. Digital images can easily be copied or shared with other dentists or insurance companies without deterioration of the image quality. With conventional film, the quality of each subsequently copied image has significantly lower quality and thus lower diagnostic value.
Comparison of cost for film versus digital systems is difficult. There is a high initial set-up cost associated with digital systems, but in the long term their costs can be similar to or less than that of film-based radiography. The initial set-up cost for a film-based dental radiography system is less than digital, but there are more ongoing maintenance costs, especially when the processor, hazardous chemical purchase and disposal, film duplication costs, etc., are considered.
While there are many advantages to digital radiography, there are also a few disadvantages when compared to film radiography. Receptor area of the film is equal to the size of the film packet as compared to the receptor size of the digital detector that is 2-4mm smaller than the outer housing of the sensor. Intraoral film placement must take this relatively smaller image size into consideration. The smaller image size may also necessitate taking multiple images for full view of some dental structures or conditions. With ever-changing technology, current digital systems may become obsolete in the future, thus future investment in equipment and/or other technology may be necessary. There may also be compatibility issues while using different sensors with a single software system. (Table 1)
Types of Digital Systems
There are two types of digital sensors available for use in dentistry, direct and indirect. (Figure 1)Direct sensors transfer digital information to the computer without any intermediary processing; the image is obtained directly from the sensor itself via a connection to the computer. Indirect sensors gather digital information that must be "interpreted" in an intermediary step, and then transferred to the computer; this usually requires an additional piece of technology that "reads" the sensor and transfers the information to the computer.
The two most common types of direct sensors are charged coupled devices (CCD) and complementary metal oxide semiconductors (CMOS). Indirect sensors are photostimulable phosphor (PSP) plates, which resemble radiographic film, and which must be "read" by a scanner that in turn transfers the "interpreted" information to the computer.
[FIGURE 1 OMITTED]
CCD sensors, which tend to be relatively thick and inflexible, were the first type of sensor to be used in dentistry. (1) PSP plate sensors gained initial popularity due to their flexibility and ease of placement, but recent research indicates concerns about their durability. PSP plates develop scratches after 30-50 exposures thus reducing the diagnostic quality of the images. (2)
Although the processing of digital images is much easier and faster than conventional film, the actual taking of the images may be a bit more challenging. The CCD sensor is bulkier and more rigid than film thus at times it can be challenging to position in patients with smaller mouths. Positioning techniques similar to those used for film may be used for the digital sensor with the understanding that the sensor will capture a smaller area than film will allow. (3) This may result in the need to take more radiographs to capture the area of interest.
The CCD sensor is held in specifically designed positioning devices and the paralleling technique can be used, as it would be with film-based radiography. Besides considering the size of the sensor, the user must also consider the positioning of the plastic sleeve and the cord (connected to the computer) when taking the image. The plastic sleeve may hinder visualization and cause the patient to gag while the cord may be in the way of the radiation beam, thus recording a radiographic image of the cord along with the dental image. When placing the sensor intraorally, it is best to keep the plastic sleeve as taut as possible to increase visualization and to keep it from interfering with positioning. The presence of excess plastic sleeve in the mouth can also increase salivation that will make it more difficult to take a radiograph. To restrain the cord, some positioning devices include a notch or clamp that can help direct the cord out of the way of the image.
The PSP plate sensor is similar to film in size and thickness and doesn't require a cord, thus it may be a good choice for pediatric patients because it is less bulky intraorally. PSP plates, however, must be handled with care as they can be scratched, which may result in artifacts and decreased quality of the image.
While there is a learning curve to mastering digital radiography techniques, the advantages over film radiography, including efficiency and ease in archiving and retrieving images, make it an attractive alternative to film-base dental radiography.
As with all dental procedures, universal precautions should be implemented for all radiographic procedures. It is imperative that the CCD sensors and PSP sensor plates be kept contamination-free as they are used over and over again with subsequent patients.
With all of its electronic components, the CCD sensor cannot be sterilized and thus a plastic sleeve should be used to cover the sensor and the positioning device, protecting both from contamination. (Figure 2) For full-mouth radiographs, this sleeve may be changed a few times during the procedure as it may become saturated with saliva and lose its shape. When changing the positioning device, the user should be cautious of removing the sleeve and the sensor as they are delicate and should be kept saliva-free. Gloves should be changed every time the positioning device is changed to decrease the chance of cross contamination. If a CCD sensor becomes contaminated, it should be wiped using a paper towel sprayed with disinfectant or a commercially available disinfectant wipe. Disinfectant should never be sprayed directly onto a CCD sensor, as damage to the sensor can result. CCD sensors are quite expensive to replace so they should be handled with great care.
PSP sensors (PSP plates) have their own infection control requirements. When using PSP technology, the plates are placed in an infection control pouch and can be used in a positioning device just like conventional film. The plates are taken out of the pouch after the image is captured and then scanned, enabling the information that they contain to be "read" and transferred to the computer. All positioning devices should be sterilized before use. The same dental radiograph camera and control panel used for film are also used for digital radiography and this equipment must also be disinfected.
Digital images are processed and viewed using a computer, and thus the associated equipment must also be protected from contamination. The computer keyboard and mouse can be protected through the use of overgloves or by placing a plastic barrier over them to avoid contact with potential contamination.
Digital radiography, by virtue of the equipment and technology used, offers unique infection control challenges. With understanding of basic principles and practice in a clinical setting, the dental assistant should be able to easily master these procedures.
Computer software allows manipulation of digital images to enhance various features to aid in diagnosis. The fact that digital images can be easily manipulated also requires safeguarding of the original images. This issue seems to be of greater concern with digital radiography than with conventional film. (4) Computers should, by default, retain the original image despite the fact that other derived images may be changed by contrast, brightness, or other characteristics. There is also an electronic log file in digital imaging software that documents exactly when an image was taken, when it was last retrieved, and if and when it was changed. As with any computer system, tampering is possible, but digital radiograph management systems will record all the activities in a log file making it difficult and complicated to alter images without detection.
[FIGURE 2 OMITTED]
It is important for the user to know how the software system works because as easy as it is to archive and access images, it may be just as easy to accidentally delete images. Once archived, digital images can generally be easily accessed, using a computer with the ability to connect to the database where the images are stored. In contrast, the physical nature of film makes it more difficult to access remotely and also easier to misplace or lose. Since the patient's digital radiographic images can be easily seen on a computer screen, it is the responsibility of the user to be aware of who can view the screen and to protect the privacy of the patient. The computer screen should be placed in a location that makes it readily available to treatment providers but not to others.
Digital radiography represents one significant way that dentistry is changing in the 21st century. While some dental offices have already embraced this new technology, many others will consider it in the future. There are similarities between film and digital radiography, but understanding the differences eases the adoption of digital techniques, and optimizes results and thus patient care using the new technology.
The dental assistant's role will continue to be crucial in this change, and understanding the basics of digital radiography will make the dental assistant a valuable asset to the practice, and foster the provision of outstanding patient care.
(1.) Farman AG. Fundamentals of image acquisition and processing in the digital era. Orthod Craniofacial Res 2003; 6(suppl 1):17-22.
(2.) Bedard A, et al. Storage phosphor plates: how durable are they as a digital dental radiographic system? J Contemp Dent Pract 2004 May; 5(2):57-65.
(3.) Petrikowski CG. Introducing digital radiography in the dental office: an overview. J Can Dent Assoc 2005; 71 (9):651-651 e.
(4.) Van Der Stelt PF. Filmless imaging: the use of digital radiography in dental practice. J Am Dent Assoc 2005; 136:1379-1387.
By Vania M. Ng, DDS, FICOI; Gurminder Sidhu, BDS, MS; and A. Jeffrey Wood, DDS
The authors of this article are affiliated with the Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, California.
Vania M. Ng, DDS, FICOI, is a Clinical Assistant Professor.
Gurminder Sidhu, BDS, MS, is a Senior International Dental Student and Clinical Assistant Professor.
A. Jeffrey Wood, DDS, is Professor & Chair, Department of Pediatric Dentistry and Director Dental Auxiliary Utilization.
Table 1. Comparison: Film vs. Digital Dental Radiography FILM DIGITAL Image Acquisition Time Delayed (darkroom Immediate processing) Darkroom Processing Required Not required Equipment Required Film, chemical Sensor, computer processor & software Image Enhancement & None Image alteration Measurement Tools possible using software Archiving Manual archiving, Digital archiving, paper patient chart computer memory Radiation Dose High Low Imaging Area Equal to dimension Less than dimension of film packet of sensor housing Cost Low initial set-up High initial cost set-up cost Duplication Quality degradation Quality constant if copied regardless of number of copies Image Sharing Copies of lower Copies of original quality, must be quality, can be physically electronically transferred to transferred to recipient recipient
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|Author:||Ng, Vania M.; Sidhu, Gurminder; Wood, A. Jeffrey|
|Publication:||The Dental Assistant|
|Date:||Sep 1, 2007|
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