Bitemarks 349was quickly adopted and adapted by others. In 1998 Sweet and Bowers com-
pared five methods in use at the time and stated that the computer-generated
overlay method was superior to other modalities, citing improved accuracy
and objectivity.^46 Sweet et al. published revised methodology later that same
year.^47 In the 2000 book and the 2003 second edition CD version, Johansen and
Bowers provided detailed instructions for the computer-generated method.^48
The computer-generated method is now considered by many to be the gold
standard for comparing the teeth of putative biters to life-sized photographs
or exemplars of bitemarks. The problem with this method and the earlier
methods is that they virtually disregard the three-dimensional features of
teeth. The computer-generated method depends upon scans of the biting
surfaces of teeth using flatbed optical scanners followed by use of various
Photoshop tools to select or illustrate the biting surfaces based upon that
scanned image. Flatbed optical scanners are not laser scanners and record no
three-dimensional information. They record light reflected from the dental
models to “highlight” the biting surfaces. Light reflects similarly from the
biting surfaces of almost all teeth independently of their proximity to the
bed of the scanner. Although some features, such as rotations and variations
in labial or lingual position, are fairly accurately recorded, a tooth that may
be several millimeters “shorter” or “longer,” that is, farther from or closer
to the incisal plane, will reflect light very similarly to one that is on plane.
Hollow-volume overlays created by this method often similarly depict the
outlines of teeth that, because they are millimeters less prominent, could
not have participated in the bite with the same force as the surrounding
teeth. A fractured incisor with part or all of the incisal portion missing may
reflect light with no discernable differences when viewed two-dimensionally.
Experienced forensic odontologists will carefully adjust the hollow-volume
overlays by visually comparing the possibilities to the three-dimensional
models. They will eschew the “magic wand” and utilize the “wise eraser” and
“experienced pencil.” This, of course, greatly reduces the objectivity but not
the accuracy of the method.
The perfect method to produce exemplars or overlays has not yet been
developed. Dailey in 2002 reported a method of considering the third dimen-
sion.^49 Dailey embedded dental models in a contrasting color of dental stone,
then scanned or photographed the models. By selectively grinding away parts
of the biting edges and reimaging in a stepwise manner, he created a series of
images that mimic the slices of computed tomography. The method requires
training, time, and skill to produce useful results and destroys the model.
Foy et al. demonstrated a cone beam computed tomography (CBCT)
method that creates serial hollow-volume overlays at investigator-controlled
levels. The method works similarly whether imaging the putative biter or
his or her dental models. Automated software that facilitates comparing the