Sensors and Digital Radiography
Digital intraoral radiography, developed following the initial digital imaging discovery by Dr. Francis Mouyen of France in the 1980s1, offers a number of features not available with traditional film radiography. These include the ability to digitally archive images and to manipulate them. Such manipulation can involve adjusting the brightness, coloration, and density of the film as well as magnification (however, the content of digital images also can be altered, which has medico-legal implications). Developing and fixing with chemicals is not required, saving time and removing the need to use chemicals. If retakes are minimized, savings in radiation exposure are obtained compared to traditional radiography.
Direct or indirect imaging can be used for digital radiography. If indirect imaging is used, a photostimulable phosphor plate is required, followed by scanning. If direct imaging is performed, no intermediate step is required prior to immediately viewing the image on a computer screen.
Direct imaging requires the use of a wired or wireless sensor ? either a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor that replaces the use of traditional film. One of the disadvantages of sensors in general is that they are rigid and thicker than film, which can lead to discomfort as well as retakes of radiographs.2 Wireless sensors offer several advantages including the removal of a potential source of cross-contamination (the wire), faster taking of oral radiographs than wired sensors, and the elimination of having to allow for the cord during sensor positioning. They are, however, also thicker than wired sensors and reported to be less comfortable.3,4
As with film, the positioning and stability of sensors during imaging is critical to obtaining a suitable radiograph, although it is more difficult due to the size and rigidity of sensors. The sensors should first be completely enveloped in a double layer of disposable sheath barrier protection.5 Barrier sleeves designed for sensors are available. Also, using disposable cushioning tabs/foam covers over the edges of the sensor can make the procedure more comfortable for the patient, increasing the likelihood of the sensor remaining in the correct position long enough to take the radiograph. Fortunately, the latest generation of sensors are smoother with more rounded edges.
A variety of sensor holders and attachments is available, with thinner and less bulky designs for intraoral radiography than initially. Options include disposable bite tabs that are similar to the bitewing tabs used with traditional film radiography; these hold the sensors in position intraorally, with minimal bulk. However, they do not provide guidance for the alignment of the X-ray beam and care must be taken to ensure a suitable alignment. Tabs are available with loops/straps that go around the sensor, holding the tab in position in the center of the sensor, as well as stick-on bite tabs. Sensor holders with bitepieces that clip over the sensor holders work in a similar manner to traditional film bitewing tabs, with the patient closing gently over the bitepiece to hold the sensor in position. When using bitepieces, one consideration is the number required to take bitewings and periapicals for full-mouth radiographs ? the ability to use just two bitepieces (one for periapicals and one for bitewings) simplifies and speeds up the procedure, and can reduce the risk of operator error.
The sensor holder that the bitepiece attaches to must fit well over the sensor. Selecting one that fits all sensor sizes and brands reduces inventory requirements, and a holder that is stable but not tight will be easier to remove, reducing the temptation to pull on the cord of wired sensors to release the sensor from the holder. Bitepieces that attach to autoclavable positioning devices (arms and rings) aid with accurate alignment. Lastly, since infection control is key with patient care items, it is important to follow validated sterilization instructions or to utilize single-use sensor holders and bitepieces and dispose of them after use on a single patient.
1. Horner K, Shearer AC, Walker A, Wilson NH. Radiovisiography: an initial evaluation. Br Dent J. 1990 Mar 24;168(6):244-8.
2. Matzen LH, Christensen J, Wenzel A. Patient discomfort and retakes in periapical examination of mandibular third molars using digital receptors and film. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2009;107(4):566-572.
3. Tsuchida R, Araki K, Endo A, Funahashi I, Okano T. Physical properties and ease of operation of a wireless intraoral x-ray sensor. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005;100(5):603?608.
4. Parks ET. Digital radiographic imaging, is the dental practice ready? J Am Dent Assoc. 2008;139:477?481.
5. Centers for Disease Control and Prevention. Guidelines for infection control in dental healthcare settings 2003. MMWR 2003;52(RR-17):1-68.