Tipton examines teeth in the lab.
To help identify fire victims from arsons, plane crashes, wildfires, terrorist attacks or genocide, a Master’s graduate from the Department of Forensic Science is investigating the use of teeth to extract DNA.
Samantha Tippen, who graduated with a Master of Science in Forensic Science this spring, returned to the laboratory over the summer to continue her project on incinerated teeth. She hopes to publish several papers on the results of the study that examines the histology and DNA in teeth.
“When people are burned, whether it is in a fire or a plane crash, there may not be anything left but the teeth,” said Tippen. “Teeth are the best way to get DNA if there is no blood or tissue available.”
Tippen got the idea for the project as an intern at the Southeast Texas Applied Forensic Science Facility, one of only six body donation sites in the country for the study of forensic anthropology. While DNA is commonly extracted from blood, semen and saliva, fewer samples are taken from teeth, which are often the last to survive a fire. In a review of academic literature, Tippen found that no one had researched the combination of histology and DNA extraction from teeth after fires. She worked with Dr. Sheree Hughes-Stamm, a DNA specialist from the Department of Forensic Science, on the project.
Tippen studies cross section of a tooth." “What we want to identify is whether there are certain teeth and parts of the teeth that are more vulnerable to damage so that we can identify the teeth that will be more reliable for DNA identification after incineration,” Dr. Hughes-Stamm said.
For her experiments, Tippen used teeth within the mandible and maxilla from remains at STAFS, subjected to 1600°C heat for an initial intense heat blast and an additional 300°C heat for another half-hour.
Because teeth are hard, it is a challenge to work with them in the laboratory to dissect samples, Tippen said. To address this issue, Tippen used a system to dissolve the calcium in the tooth and sent the samples to M.D. Anderson to provide cross sections of the tooth for study.
What Tippen discovered is that although natural and incinerated teeth do break down, minute amounts of DNA can be extracted and used to develop a DNA profile to identify the victim.
“One of the important findings for forensic labs is that, even though there may appear to be no DNA present, they should run through the process anyway to try and get a DNA profile as the kits used for identification are very sensitive,” said Tippen.
A human tooth preserved in plastic.In the histology project, Tippen studied what happens to teeth post-mortem. In all samples – both natural and incinerated – she found the crown disintegrates, while the root remains thick and consistent. In incinerated samples, the remaining tooth will fracture and collapse. Even though the teeth contained no visible nuclei, minute amounts of DNA could still be extracted. In testing different teeth, including incisors, canines, pre-molars, and molars, she found that pre-molar and canine teeth yielded the best results because they were relatively protected from the fire in her experiments. Previous studies have found that the molars typically present as the best sample type as they lie within the back of the mouth and are therefore better protected from the heat. Future studies that better mimic forensic cases involving fire would be expected to produce similar results to these conclusions.
A disintegrated tooth under the microscope." While blood and tissue typically yield high amounts of DNA, in comparison, teeth yield very little. In teeth, 50 picograms of DNA are considered a good sample, but in her incinerated samples, Tippen was getting less than 20 picograms of DNA. However, even in those small cases, Tippen found enough to create a partial DNA profile that could help identify the victim.
While further study is needed, Tippen said the experiment may assist in identifying victims in the forensic field.
Tippen is currently applying for jobs as a research assistant, and she plans to pursue a career in medical genetics after getting her Ph.D. degree. This project has encouraged her to look at genetics to see if they are related to rare diseases that affect individuals.
“I would rather do something that could have a huge impact and fail trying, then repeat the kinds of experiments that are done all the time,” Tippen said, reflecting on both her research into extracting DNA from teeth and future research into rare diseases.