BUFFALO, N.Y. -- When an explosion, accidental cremation or a
fire set deliberately to cover a crime destroys a body, precious
little may remain to link it to a life once lived.
Yet even among the ashes, a team of forensic dental researchers
at the University at Buffalo has shown that evidence exists that
can help identify human remains when all else -- flesh, bones,
teeth, DNA -- is lost.
The evidence can be hard to recognize, but it is
In a series of experiments reported in the May 2006 issue the
Journal of Forensic Science and in an upcoming article in the same
journal, the researchers show for the first time that inorganic
resins that make up the central matrix of tooth-colored dental
fillings can withstand temperatures of 1,800 degrees Fahrenheit, be
recovered and named by brand or brand group.
Even when only fragments of resin could be found, the
researchers were able to classify the composition of elements in
the filling. Comparing those elements and their proportions to the
composition of the known filling brands recorded in a deceased's
dental chart could, under the best circumstances, help identify the
At the very least, the analysis could determine if the filling
material was or was not consistent with a person's dental
Mary A. Bush, D.D.S., said this new type of evidence could have
a major impact on forensic dentistry.
"To date, no one has recognized that many modern restorative
resins have unique characteristics that can be distinguished and
used for forensic identification," said Bush, assistant professor
of restorative dentistry in the School of Dental Medicine at the
University at Buffalo and lead author on the studies.
"Nobody has applied the standard analytical methods that we have
at UB to survey these materials and determine these
Peter Bush, director of the instrument center where much of the
research analysis was conducted, was a major contributor to the
research, along with Raymond Miller, D.D.S., UB clinical assistant
professor of oral diagnostic sciences and a forensic dental expert,
and Jennifer Prutsman-Pfeiffer, anthropologist and UB doctoral
The team's work has yielded unexpected rewards. The FBI has
offered to include the information in their database, and the
American Society of Forensic Odontology provided a grant to help
assemble the data.
"The importance of identifying these properties is, first, to
show that it can be done," said Bush, "and second, that it can be
done even after extreme events such as mass disasters, plane
crashes or explosions," or a murder.
The 1999 trial of Donald Blom, accused of killing Katie Poirier
after abducting her from a Minnesota convenience store,
demonstrated the usefulness of such forensic evidence. Blom
confessed to the crime, but later recanted. The body never was
found, but human bone fragments and a single tooth were unearthed
in a burn pit on Blom's vacation property. Analysis of the
components of the tooth's filling material matched the brand of
filling recorded in the victim's dental records. That evidence
helped put Blom in prison for life.
Bush and colleagues began their experiments in mid-2005, using
UB's specially equipped instrument center, which includes a
scanning electron microscopy/energy dispersive X-ray spectroscopy
equipment, known as SEM/EDS, and a portable X-ray fluorescence
(XRF) unit to conduct material analysis outside the lab.
They had access to cadavers for the second research phase
through the UB School of Medicine and Biomedical Sciences'
Anatomical Gift Program, to which persons donate their bodies for
use in teaching and scientific research.
Initial experiments were carried out with teeth only.
The investigators created disks of 10 different resins used for
standard tooth fillings to serve as controls, then filled extracted
teeth with the resins and incinerated them in an oven at 900
degrees Centigrade (1,652 degrees Fahrenheit) for 30 minutes.
These conditions were more extreme than in a standard cremation,
Bush noted, because teeth normally would be protected by flesh and
bone, allowing them to withstand the high temperature for a longer
period of time. With no such protection, the extracted teeth
fragmented in half-an-hour.
Dental resins consist of an organic matrix surrounding inorganic
filler particles. "At these high temperatures, everything organic
is destroyed," said Bush. "It was the inorganic material that was
After retrieving the resins fragments, the team analyzed their
elemental composition using SEM/EDS. In the May 2006 issue of
Journal of Forensic Science they reported they were able to
identify the concentration and microstructure of the inorganic
elements in the fragments and link them to the specific brand or
brand group of the material documented in the controls.
"Not only do these materials have various microstructures," said
Bush, "they also have unique elemental compositions, which makes it
possible to distinguish between brand or brand groups. We showed
that the elemental distinction remains even after extreme
conditions such as cremation."
To create a true-to-life scenario, the team worked next with
cadavers donated to the medical school's Anatomical Gift Program.
(Full approval from the university's Human Subject Review Board was
obtained for the study.) They removed all existing resin fillings
from the teeth of six cadavers and replaced them with a total of 70
fillings representing five different resin brands. The filling
brands used were recorded in each cadaver's dental record.
With the new fillings in place, the bodies were put through the
standard two-step cremation process: very high heat (1,800 degrees
Fahrenheit) for two and a half hours, which destroys all flesh and
small bones, then crushed in a grinder and reduced to ashes.
Bush and colleagues were able to find and identify enough of the
resins to make a positive identification of each cadaver, using the
portable XRF unit to mimic investigations that need to be conducted
in the field.
The results of this study will appear in the online version of
the Journal of Forensic Science in December 2006 and will be
published in the January 2007 print issue.
"Even in the ashes, we were able to retrieve small pieces of
resin and distinguish between cadavers," said Bush. "To my
knowledge, this is the first time this type of analysis has been
done. This study provides hope of identification when little hope
may be present.
"If an individual isn't burned to this extreme and the teeth are
intact, but the dental X-ray comparison is questionable or teeth
are fragmented, this type of analysis can give another level of
certainty on which to base an identity," she said.
XRF doesn't provide as much information as the lab-based SEM/EDS
equipment, Bush noted, but its speed compensates for lack of
precision. The device can identify the chemical spectrum of
elements in inorganic material in 6-10 seconds, providing quick
on-site screening of suspected material.
The ability to distinguish between resins gives investigators a
new tool for use in special circumstances, Bush said.
"Retrieving small amounts of resin as we did in this study would
not carry as much weight for identification as a dental chart
comparison, but the evidence was indisputable and unequivocal. This
evidence would serve as an aid in identification when very little
other evidence exists or when added scientific corroboration is
Bush and her co-investigators currently are working with the FBI
to construct a database of the most common brands of dental
restoration materials and their elemental composition for use in
"There are more than 50 filling materials on the market today,"
said Bush. "We have analyzed the 30 most popular resins and 23
historical resins dating back to 1971. There are also many other
unique dental materials -- posts, cements, crowns, sealers -- that
also will be included in our database. Again, no one else has
attempted such a comprehensive survey of their properties."
The database does have limitations: It will be useful only if
dentists document all dental restorations, including brand names,
in their dental records, noted Bush.
The UB researchers will have a role in bringing that point home
to their colleagues and dentists of tomorrow through the new
Laboratory for Forensic Odontology Research (LFOR) housed in the UB
dental school. Bush will direct the laboratory, with Miller as
The laboratory will host demonstrations and seminars on forensic
dentistry for students, and present lectures and continuing
education programs in forensics for practicing dentists.
The knowledge they gain may help deter any future "Donald
The University at Buffalo is a premier research-intensive
public university, the largest and most comprehensive campus in the
State University of New York. The School of Dental Medicine is one
of five schools that constitute UB's Academic Health Center.