190 Forensic dentistry
absorbs much more energy than its surrounding enamel and dentin, allow-
ing less energy to reach the receptor at that location and creating an invisible
latent image. Through some mode of processing of the receptor, the amalgam
will later be displayed in an image that can be detected visually. With dental
film the processing involves chemicals; with digital sensors it may involve
modern electronics and lasers.
Dental x-ray “receptors” have undergone numerous changes over the
history and advances in dental radiography. Included have been chemi-
cally coated glass photographic plates, intraoral films covered with silver
halide emulsions of various grain sizes and image speeds, extraoral silver
halide films requiring light-emitting screens, direct solid-state digital charge
coupled device (CCD) and complementary metal-oxide semiconductor
(CMOS) detectors, and photostimuable phosphor plates.
Each receptor system has its advantages and disadvantages. Film is inex-
pensive, easy to place, and produces an exceptional image if proper tech-
niques are used, but requires several minutes of chemical processing, ideally
in a darkroom setting. Also, film can be fogged by heat, light, pressure, and
overactive chemicals. Unused film eventually must be discarded if it becomes
out of date. Direct digital sensors (CCD and CMOS) provide an immedi-
ate image with no chemical processing or darkroom needs. The ability to
enhance the image density and contrast often reduces retakes. It provides an
image with spatial resolution ranging from 12 to 20 mm/lp.^6 Yet a compara-
tive study showed that digital images are of equal quality to film when evalu-
ating interproximal caries.^5 However, digital sensors are delicate, expensive,
in some cases difficult to place, and require enormous amounts of digital
storage for the resultant images. Most agree that direct digital is the best
image receptor in a mass fatality incident due to it providing an immedi-
ate image and dealing effectively with the exaggerated flow of victims in the
morgue setting (Figure 10.1).
Phosphor technology provides an excellent image with placement ease
similar to that of film but requires several minutes of processing time as the
plate must be scanned by a laser drum to produce the image. The phosphor
plates also scratch easily and must be replaced fairly frequently, depending
on care of handling.
The most useful feature of the three digital systems is the ability to
marry the resultant images with third-party software such as Photoshop™
and WinID™, and the abilities gained through an increasing technology, tele-
radiography, where radiographic images are interpreted at a distance via the
Internet. Digital imaging also produces 256 shades of gray. While humans
and some computer monitors cannot discern that many gray levels, interpre-
tive software can. This may eventually lead to software with the ability to
“match” dental images in determining a dental identification at a rate that
would far exceed human ability. To ensure interoperability with third-party