If offices have not converted as of yet, all offices will be facing this decision within this decade. Dental X-ray film is slowly being phased out and virtually all of the radiographic manufacturers are switching to the production of digital imaging systems. Multiple factors need to be considered when a dental office is transitioning from film based radiography to digital techniques.
Conversion to a totally digital imaging environment for a dental practice requires the practitioner to do a little bit of homework on the various digital imaging systems that are available on the market. Additionally, it is advisable for the office to perform a work-flow study to determine the most efficient digital X-ray systems to purchase for the office. All of the currently available systems have similar features but entirely different methods of image capture, i.e., how the radiographic information is received, stored, and displayed. Two basic types of image receptors are in use today for both intraoral and extraoral digital radiographic techniques. The two types of image capture methods can be classified as direct and indirect. The direct method involves capture of the X-ray photons and conversion to a digitally formatted image by either a hardwired or wireless connection to the computer. The indirect method is similar to film in that image capture occurs using a phosphor plate with storage of the information as a latent image and processing of the plate to recover the latent image and conversion into a digital format in the computer. Both methods of image capture and display offer their own unique advantages and disadvantages. The advantages and disadvantages of both methods will be detailed later in this article.
Conversion to a digital-imaging environment offers many distinct advantages over film. Probably the biggest positive factor is the elimination of a darkroom and all of the mess and fuss with maintaining a processor and film chemistry. Additionally, many municipalities have become quite prescriptive as to effluent discharges into the waste water systems and many now require silver collectors to ensure that film processor contaminates do not enter a city’s water system. Purchasing and restocking of film, boxes of film exceeding their shelf life, fogging of film due to heat or scatter radiation, contamination of film from chemistry or other contaminates and the generation of waste from film packaging all become a thing of the past when an office converts to digital.
When an office decides to “take the plunge” into the digital realm there are some ideas to consider in this process. Many dental equipment purchases, such as a dental chair, require the decision-maker to choose the one chair that has all of the features that they like and that best suits their needs; often that one chair is chosen throughout the office. The notion that one size fits all doesn’t quite equate for digital radiographic systems. Different modes of image capture are desirable for different operations in dentistry. For example, hardwired sensors are preferable for endodontics but storage phosphor plates give the operator the optimum opportunity to capture a diagnostic bitewing image. Other considerations in the decision making process are dependant on factors relating to the facility and office work flow. Hardwired sensors require computers at each work station in which images are captured, but one storage phosphor processor with one computer may be sufficient for the entire office. Let’s consider the advantages that each type of system has to offer for the dental practice. Hardwired systems are manufactured with two types of sensors: Charged Couple Device (CCD) or Complimentary Metal Oxide Semiconductor (CMOS). X-ray photons strike the sensor and capture this energy which is then passed through electronics and along a wire as an analog signal to the computer where it is converted into a digital format and displayed on the computer monitor. Although one manufacturer offers a wireless CMOS sensor, the mode of capture is still a direct acquisition of the image and display within a few seconds. Since CCD or CMOS systems offer an almost “instantaneous” display there are certain dental operations where the use of a hardwired system is an advantage. Endodontics involves the capture of multiple individual images during the procedure where it is beneficial to have immediate display. Checking a crown margin, checking implant placement position during surgery, post-op checks of restorations and many emergency situations all benefit from a system which offers immediate image display chairside. An example of a hardwired sensor is seen in Figure 1.
Hardwired systems require a computer at the operatory where images need to be captured and displayed. Offices that do not utilize computers chairside, or have a networked system so that only a monitor is needed at the chair or for other reasons do not want to capture images at the operatory, may find the choice of a hardwired imaging system to be too restrictive.
An office work flow study will help to determine the best location for full mouth surveys to be completed, where individual images during procedures need to be done and where images for emergency visits should be managed. This type of study will help the practice to decide where hardwired imaging systems should be located.
Indirect X-ray systems utilize a phosphor plate technology commonly referred to as Photostimuable Storage Phosphor (PSP). This type of imaging system requires an additional step in processing the image. The radiographic image is stored on the plate in the form of a latent image very much akin to conventional film. The plate is placed into a processor attached to a computer which scans the plate with a laser that releases the stored charges in the form of visible light. These varying wavelengths of light are picked up by a photomultiplier and converted to an electrical signal that is then digitized in the computer and displayed on the monitor. PSP plate techniques offer some advantages over the hardwired systems. These imaging plates are thin and are produced in the same common sizes as film. Additionally, the entire plate is capable of image capture and storage unlike hardwired sensors which usually have some inactive area. The thinness and lack of an inactive area allow for sensor placement as close to film as possible. PSP plates allow portability. Plates can be taken from operatory to operatory negating the need to be tied to a computer. For example, a full mouth survey can be taken in one operatory but processed in an entirely different area of the office. Again, work flow and facilities usage must be considered when incorporating digital radiography into a practice. An example of a PSP imaging plate is seen in Figure 2.
PSP plates are especially advantageous for bitewing imaging. Plate thinness and an active area that encompasses the entire plate allow the practitioner to easily capture the distal of the canine in a premolar bitewing (Figure 3). For ease of use, patient comfort and low cost of sensor replacement makes a PSP system a logical choice when planning for digital imaging in a dental practice.
A practitioner would never consider utilizing only one type of bur to prepare all teeth for all types of restorations, so although imaging systems may not be a fair comparison, an office should look at more than one imaging system when incorporating digital imaging technique into the office. Limiting an office to only one imaging sensor design becomes much too restrictive for a practice. Lingual tori, limited opening, malocclusions, high muscle attachments, and strong gag reflexes are only some of the challenges faced when attempting to take a diagnostically acceptable intraoral digital image. There are some instances when an adequate film image cannot be obtained. These types of situations become even more difficult with digital sensors. The thickness or the inflexibility of the sensor may not allow for ideal placement. When the office is equipped with more than one system, especially when both CCD/CMOS and PSP image receptors are available, the opportunity to get the needed image is improved.
Conversion to digital imaging in a dental practice takes some investigation into currently available systems, as well as a review of the facility and work flow patterns. Cost savings, decreased radiation exposure for patients, elimination of the darkroom and processing chemistry, and the ease and convenience of digital technique make the implementation of digital radiography a must for all dental offices. When planning for conversion to digital radiography consider incorporating more than one digital imaging system and more than one type of imaging sensor.Arizona School of Dentistry & Oral Health A.T. Still University of Health Sciences 5850 E. Still Circle Mesa, Arizona 85206