# Assessing the Micro- and Macroscopic Changes of Chemically Altered Human Bone and Teeth

## TL;DR

This study examines how chemicals like sodium hydroxide and hydrochloric acid affect human bones and teeth, and how these changes impact DNA recovery for identification purposes.

## Contribution

The study introduces a novel approach to analyzing intervallic micro- and macroscopic changes in chemically treated bones and teeth, focusing on DNA recovery feasibility.

## Key findings

- Teeth provided higher quality and yield of DNA compared to bones after chemical treatment.
- Complete STR profiles were successfully obtained from all tooth samples.
- Alteration patterns and DNA yields varied depending on the chemical treatment and exposure duration.

## Abstract

Sodium hydroxide (NaOH) and hydrochloric acid (HCl) are household chemicals used to disfigure victims in forensic contexts due to their high availability and apparent effects, which alter both the structural integrity and composition of skeletal elements. NaOH dissolves soft tissues and produces violent, exothermic reactions but, ostensibly, fails to alter the structure and color of bones and teeth. HCl is considered one of the most destructive chemical agents utilized, causing rapid demineralization of hard tissues. Current works focus on total dissolution times, rather than on discrete changes and the potential for personal identification. This research aims to comprehensively assess the intervallic micro- and macroscopic changes occurring in chemically altered bones and teeth. Analyses were conducted to investigate how morphological shape and surface area-to-volume ratios may affect the degree of alteration and to evaluate the feasibility of DNA isolation and profiling. The relationships between these factors were not linear, and the results show a variable pattern of alteration and DNA yields depending on the treatment and duration of exposure. Teeth were found to be better sources for obtaining higher quality and yield of DNA compared to bones, and complete STR profiles were obtained from all tooth samples. Overall, this pilot study highlights the challenges of analyzing taphonomically altered remains and underscores the need for effective identification methods.