Date of Submission

5-2021

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Forensic Science

Advisor

Virginia M. Maxwell, Ph.D.

Committee Member

Angie Ambers, Ph.D.

Committee Member

Paula C. Brumit, DDS, D-ABFO

Keywords

Tooth Root Translucency, Postmortem Diagenesis, Hydroxyapatite, DNA, Unidentified Human Remains (UHR)

MeSH

Durapatite, DNA, Body Remains

LCSH

Diagenesis, Hydroxyapatite, DNA, Anonymous persons, Dead

Abstract

Endogenous genetic material protected by the rigid, mineralized hard tissues of bones and teeth is often targeted for forensic DNA testing in missing persons and unidentified human remains (UHR) investigations. Although standard approaches have narrowed sample selection to a few optimal skeletal elements (i.e., weight-bearing long bones, teeth), subsampling and decisions beyond this can be challenging due to the non-uniform, heterogeneous pattern of postmortem diagenesis. One particular component of skeletal microstructure — the inorganic mineral matrix [hydroxyapatite (HAp), Ca10(PO4)6(OH)2] — is purported to play a major role in DNA preservation. The potential correlation between molecular changes to skeletal microstructure and the quantity/quality of endogenous DNA is an important area of investigation to maximize success and potentially streamline decision making for testing. In casework, forensic odontologists commonly examine a feature called tooth root translucency (TRT) as an established method for estimating the chronological age of an unknown decedent. The ultimate aim of this study was to determine if TRT could be used as a reliable indicator of the viability of teeth for DNA testing.

This research involved: 1) microscopic examination, measurement, and photo-documentation of TRT in intact and sectioned teeth (n=55) from human subjects of known chronological age; 2) X-ray diffraction (XRD) of pulverized tooth powder to assess the crystalline state of HAp in each tooth; and 3) DNA extraction from teeth (n=25) to assess the correlation between degree of TRT and quantity/quality of recovered DNA.

This project successfully created a cost-effective strategy to measure TRT and preserve the physical integrity of tooth samples for downstream DNA testing. The microscopic model described herein could easily be employed in Disaster Mortuary Operational Response Team (DMORT)

tents and other fieldwork scenarios. The crystalline state of HAp was determined to have an insignificant influence on degree of TRT in human teeth. However, TRT was shown to directly correlate to DNA preservation in teeth. Samples with low degrees of TRT possessed higher quantity/quality DNA than those with higher degrees of TRT (p < 0.05). Empirical data from this study could provide a framework to guide forensic odontologists in selecting skeletal samples to submit for forensic DNA testing.

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