Intra-Oral Digital Radiography: Direct versus Indirect Methods

Intra-Oral Digital Radiography is quickly emerging as one of the "hottest" areas in dentistry, a popularity that is in great part fueled by the improved accessibility, performance, and decreased price of PC’s. Surveys indicate that Digital Radiography is on or near the top of the wish lists of a very high percentage of dentists. Those who have integrated the technology acknowledge they obtain an image that is diagnostically equivalent to film. Furthermore they enjoy the benefits of more effective patient communication and understanding, time efficiencies, lower radiation exposure, improved diagnosis, the reduction or elimination of film chemistry, and more effective practice marketing.

There are currently two types of systems available on the market today when it comes to digital radiography: direct and indirect.

Direct Systems: Direct systems use a wire-based sensor that contains a computer chip inside a protective casing; the sensor is connected via wire and other cabling to a PC. The sensor is placed in the patients mouth using a variety of different holder systems. The computer chip (CCD or CMOS) captures light information that is emitted by a phosphor plate in the sensor when it is hit by x-rays. This information is then transmitted directly into the computer, digitized, then displayed as an x-ray image on the computer screen. Captured images are stored and archived within a compatible software. Direct Digital radiography systems offer a significant time advantage in general dentistry but particularly during endodontic, implant, and emergency situations; the image processing time with direct systems is around five seconds. Sensors are easily moved from operatory to operatory allowing operators to work with a minimum number of sensors and within a computer network environment . The primary disadvantages of the sensor based systems are: (1) the cost of the sensors which range between $6,500 and $10,500 depending on the size of the sensor and the manufacturer; 2) greater difficulty in placing the sensor with a small percentage of patients due to its rigidity; and (3) working and maneuvering around a wire based device. Examples of leading hardware manufacturers of Direct Digital Radiography systems are: Schick CDR, Sirona Sidexis, Dent-X Eva, Planmeca Dixi3, Gendex VisualiX eHD, Instrumentarium Sigma.

Indirect Systems: Indirect Intra-Oral Digital Radiography systems use film-like photo-phosphor plates that are "activated" using x-ray then scanned in special devices that read the image from the plate. The plates come in sizes essentially the same as familiar film sizes. They are held in the patients mouth using existing holder systems. Once the plates are activated they are brought to a centrally located scanning device and loaded into the device. Scanning time varies from around 30 seconds to 5 minutes depending on the amount of plates being scanned and the type of scanning device used. Scanned images are "loaded" into a compatible software where they are archived in patient files. The main advantage of the indirect systems is that the plates are flexible and thinner than direct type sensors; arguably this makes them more comfortable. The nature of the plates does tend to make it easier for the staff to adapt to the use of the system as they are "film-like" and therefore more familiar. Also some systems offer Panoramic capabilities as an add-on feature, allowing for complete elimination of film in the office. The main disadvantages of the indirect systems are: (1) there is more time required to obtain the images ,and (2) the amount of handling is at least the same as required with film and require; therefore in both instances the opportunity for time efficiencies is lost. Examples of leading hardware manufacturers of Indirect Digital Radiography systems are: Gendex DenOptix, Soredex Optime and AirTechniques ScanX.

One of the things that is important to consider with respect to indirect systems is the cost of replacing the plates. Any user of these systems can attest to the fact that the plates are very easily damaged and the physical damage of the plate shows up as an artefact on the radiograph. Inevitably, plates will need to be discarded and replaced. In addition, exposure to elements light dust and light can have an effect on the overall quality of the image over time. This will also require periodic replacement of plates in order to maintain top-quality images. These are factors that need to be considered when comparing the economics of direct vs indirect methods.

In the end the integration of Digital Radiography into your practice offers the same major advantages regardless of the type of system you choose. The choice of system, be it direct or indirect, will be a matter of your specific needs as they relate to the size, style, and nature of your dental practice. As well, your preference for the software that manages the images captured should be considered in your decision as they will also impact the ease-of-use of the system.


This article was revised as of June 1, 2006 by Mark Crews, The Bridge Network


By: pm.nguyen
On: 04/25/2008 23:51:36
I've been fortunate enough to use both types. The indirect though may appear to be more comfortable for the patient but in the end takes almost as long to process as it does with conventional film. And if you have to retake a radiograph, it is a hassle.

I purchased Schick (direct) and love it. Though there was a steep learning curve but you have to stick with it and not fall back into familiar comfort of conventional films. We had a lot of retakes when we first used it but by the 2nd week, everyone is a pro. We take radiographs of pediatric patients and the instantaneous result lets us know if we have to retake right away or not. Also very beneficial when we do GA cases withoug having to wait for it to process. Not to mention if you do endo, the direct method is an absolute must.

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