Digital Radiography was first introduced in the mid 1980’s. With each passing decade an increasing number of dental offices have replaced their traditional film-based x-ray systems with this newer technology.
For the sake of being thorough, I feel the need to briefly touch on the two main types of digital x-ray systems. I hope this isn’t too technical…I just want everyone to be able to appreciate how each ‘system’ produces the image that can be seen on the computer monitor.
The Different Types of Digital Systems
There are basically two types of systems. These in a nut-shell are:
1) Charge-Coupled Device (CCD)
A sensor is placed in the patient’s mouth. A cable then connects the sensor to a computer in the dental operatory. Through the energy of electrons, an image is created instantaneously on the computer monitor. The sensor connects to the computer system through a USB connection.
2) Storage Phosphor (SP) Systems
This system uses ‘plates’ which consist of a polyester base coated with an emulsion of a barium fluoro-halide compound.
X-Ray energy is stored in the emulsion and a latent image forms on the SP plate.
This concept is similar to how a latent image forms on a conventional x-ray film.
SP plates are similar in size and thickness to conventional film and the entire surface of the film is active…not necessarily the case with the CCD system.
A Comparison of the Two Systems
The sensors are thicker than conventional film. This makes it harder for patient’s to tolerate them.
It is also easy to damage the cable (wire) that is attached to the sensor. The entire sensor is not active I.e., some sensors may only capture 60 % of the surface area of the film. Less area is captured on a CCD verses a conventional film.
The amount of active area varies between manufacturers. This being said, the active area of the CCD system that we use in our office (Dexis Sytem), is almost 100%. This is because all of the electronics are engineered on the back of the sensor.
With SSP film, one cannot view the images instantaneously as one can with CCD film.
With the CCD system, we leave the dental operatory and press the ray exposure button. When we walk back into the operatory, the image is on the computer screen.
With the SP system, the SP plate is removed from the patient’s mouth and placed into a laser scanner. A laser beam scans the plate and creates an analog signal which is converted into a digital image on a computer monitor.
– Unlike CCD, with the SP system, there is the inconvenience of loading the laser scanner. –
– Depending on the size and number of plates, it can take between a few minutes to 20 minutes for an image to appear on the monitor. As previously mentioned, the CCD image appears immediately on the monitor.
– In addition, the SP plate needs to be erased by applying a strong light to it before it can be re-used. This is more time consuming than the CCD system.
After reading this blog, I hope that you are able to appreciate the fact that technology has entered the dental field in a big way…and it’s not just limited to dental x-rays.
Please stay tuned for the next blog to see the advantages of using Digital Radiography (DR) versus conventional film and how DR benefits the patient.
Yours in good dental health,