Nondestructive automated DNA extraction method from the tooth root surface

Abstract

Skeletal remains are among the most challenging forensic samples, and when extracting DNA from them, destructive grinding is usually employed to obtain a sufficient quantity of DNA. When identifying skeletonized remains, a nondestructive extraction method is of great importance, and undamaged skeletal remains should be returned to relatives after identification due to ethical issues. Teeth are a good source of DNA, which can be found in dental pulp, dentin, and cementum. Similar to bones, highly destructive grinding of the entire tooth is usually employed in the standard forensic extraction procedure. Recent studies have shown that DNA can be best preserved within teeth in the cementum layer of the tooth root. The DNA in the tooth root surface is easily accessible. A simple and fast nondestructive method without grinding, drilling, or scraping of the tooth was developed. A commercial forensic extraction kit was used for automated DNA purification. Sixty-two canines from adult skeletons excavated from two archaeological cemeteries dating from the 13th to 19th centuries were used for analysis. After chemical cleaning and UV irradiation, demineralization was performed by submerging the tooth in 0.5 M EDTA, followed by lysis of demineralized tissue and automated DNA purification. Real-time PCR quantification was employed to determine the quality and quantity of DNA. The efficiency of the nondestructive DNA extraction method developed for genetic analysis of teeth was evaluated by determining the DNA yield, degree of DNA degradation, and success of short tandem repeat (STR) typing. The results showed high efficiency of the method developed, with highly informative STR profiles obtained from 74 % of archaeological canines analyzed. This study highlights the potential of a nondestructive method for analysis of skeletal remains, and it discusses the practical implications of teeth for forensic investigations. The method developed to physically preserve the tooth is simple, fast, and highly efficient, and, because of reduced manual handling, it has a low risk of contamination.