Teeth are an indispensable tool for forensic investigators when it comes to correctly identifying victims. Dental records can be used to identify most victims, including the ones subject to heinous crimes that have left their bodies unrecognizable. And now, researchers at NYU have shown that teeth can do even more—they can reveal impactful events that occurred during a person’s life.
The research focused on cementum, the dental tissue that covers the tooth's root. It begins to form annual layers—similar to a tree's rings—from the time the tooth surfaces in the mouth. The underlying organization of the cementum’s fibers and particles can only be seen through microscopic examination, so Paola Cerrito, a doctoral candidate in NYU's Department of Anthropology and College of Dentistry, turned to light microscopy.
“We used polarized light microscopy to image the thin sections, about 100 micrometers, of the teeth,” she told Forensic. “This type of light microscopy is useful for imaging structures with characteristics related to their optically anisotropic character—i.e. being directionally dependent.”
Cerrito, along with co-authors Shara Bailey and Bin Hu, used polarized light microscopy to examine nearly 50 human teeth, aged 25 to 69, from a skeletal collection with known medical history and lifestyle data, including age, illnesses and movement (i.e., urban to rural environments).
The researchers were able to see permanent changes in the microstructure of cementum based on physiologically impactful events, such as reproduction and menopause in females and incarceration and systemic illnesses in both males and females. More importantly, the researchers determined these changes in the cementum can be accurately timed.
“There are significant efforts to match the bodies of deceased to individual identities. These efforts rely on gaining as much information as possible from human remains,” Cerrito said. “Data regarding a female’s reproductive status, the age(s) at which she gave birth, or the prior contraction of a severe illness can inform medico-legal efforts in their work to restore unidentified victims. Being able, on the basis of cementum analysis, to confirm/exclude the presence/absence of an event for which there is record in the putative corresponding identity can help if not in identifying a body, at least in excluding or confirming a hypothesized identity.”
Cerrito and her team plan to extend their research; first by turning from microscopic to elemental analysis. Results will enable the team to build an event-specific library of changes in ratios of elemental distribution, as each stressful event caused a change in mineral balance. Second, the researchers plan to employ non-destructive analysis methods, which is important in both a historical context as well as for evidence.
“Specifically, we are implementing phase-contrast synchrotron radiation micro-tomography (high-resolution CT scans performed at physics labs),” said Cerrito. “We have already collected pilot data at the Elettra Synchrotron Radiation Facility in Italy, and the preliminary results are encouraging. We are now submitting a proposal to return there with a larger sample size and validate the possibility to perform the analysis published in the current study in non-destructive ways.”
The researchers’ article has been published in Scientific Reports.
Photo: Panel A is a longitudinal section of the maxillary second molar of a 35-year-old female who had children at ages 19 and 24. Panel B is a zoomed-in section of Panel A. Panel C reveals, at left, the dentine, covered, at right, by the cementum, which presents two distinct darker "rings" that correspond to the two reproductive events. Credit: Paola Cerrito