Sweet tooth: DNA profiling of a cranium from an isolated retained root fragment

Sampling of healthy multi-rooted teeth is recommended for the genetic identification of human skeletal remains. However, this may not always be possible, as in the reported case consisting of an isolated human cranium found in an aggregate crushing and processing plant in Piedmont, Northwest Italy. The cranium displayed significant weathering, suggesting a post-mortem interval of several years, and was edentulous with the exception of the apical root fragment of the upper left canine, consequence of an antemortem horizontal fracture. Prolonged decalcification of the root fragment followed by powder-free DNA extraction from ~10 mg of root tip tissue led to the recovery of >10 ng of high molecular weight human DNA, in comparison with ~0.01 ng of DNA per mg of bone powder obtained from the petrous portion of the temporal bone. Quantity and quality of DNA isolated from apical tooth tissue enabled multiple genotyping, including a reportable female STR profile, mitochondrial DNA analysis, and ancestry-informative insertion/deletion polymorphisms. Although the cranium remained unidentified after DNA comparisons, our findings confirm that apical tooth tissue is a promising source of DNA, easily obtained through a powder-free extraction protocol. Results also indicate that root tips should not be overlooked in challenging identification cases, even in the presence of compromised tooth specimens.