# Investigation of a DNA Profiling Method Using Only Cementum More Than 70 Years After Death

## TL;DR

This study shows that DNA profiling using cementum from old teeth is effective for identification even after 70 years.

## Contribution

The study introduces cementum as a viable DNA source for STR profiling in long-postmortem teeth.

## Key findings

- DNA from cementum showed comparable profiling accuracy to dental pulp and dentin.
- Cementum from cervical line or root apex areas provided similar DNA profiling results.
- At least 5 mg of cementum is sufficient for accurate DNA profiling.

## Abstract

Short tandem repeat (STR) typing is widely used not only for blood relationship identification but also for the personal identification of unidentified bodies. However, DNA is susceptible to the effects of environmental factors, consequently leading to reduced DNA yields. Therefore, to maximize the DNA yield required for identification, teeth are generally completely pulverized during DNA extraction. However, this renders subsequent testing after DNA profiling impossible. In this study, we investigated the utility of DNA profiling using only the cementum from teeth that had been left outdoors for long postmortem intervals. We analyzed 90 molars (fresh teeth) that were extracted within six months at a dental clinic and 90 molars (stale teeth) exposed outdoors for over 70 years, and following cementum extraction, the accuracy of STR profiling, optimal site for cementum collection, and minimum amount of cementum required for STR profiling were determined. The results demonstrated that the profiling accuracy of DNA extracted from cementum was comparable to that of DNA from dental pulp and dentin. Furthermore, the collection of cementum from either near the cervical line or from the root apex areas did not show significant differences in DNA profiling accuracy, indicating that securing at least 5 mg of cementum was sufficient to ensure precise DNA profiling. These findings suggest that DNA profiling using only cementum is viable even in teeth that have been subjected to a long postmortem interval.