Structural characterization and decontamination of dental calculus for ancient starch research

Abstract

Ancient dental calculus research currently relies on destructive techniques whereby archeological specimens are broken down to determine their contents. Two strategies that could partly remediate a permanent loss of the original sample and enhance future analysis and reproducibility include (1) structural surface characterization through spectroscopy along with crystallographic and spectroscopic analysis of its molecular structure, and (2) surface decontamination protocols in which the efficacy of cleaning dental calculus prior to extraction is demonstrated. Dental calculus provides ancient starch research a niche where granules may be adsorbed to minerals, coated, overgrown, entrapped, and/or protected from chemical degradation. While encapsulation offers protection from degradation, it does not shield the sample’s surface from contamination. The most common approach to retrieving microbotanical particles from archeological calculus has been the direct decalcification of the sample, after a cleaning stage variously consisting of immersion in water, acids, and mechanical dislodgment via gas, sonication, and/or toothbrushes. Little is known about the efficiency of these methods for a complete removal of sediment/soil and unrelated microbotanical matter. In this paper, controlled laboratory experimentation leads to chemical structural characterization and a decontamination protocol to eradicate starch granules. Several concentrations of acids, bases, and enzymes were tested at intervals to understand their potential to gelatinize and fully destroy starch granules; arriving at a procedure that effectively eradicates modern starch prior to dissolution without damaging the matrix or entrapped starch microremains. This is the first attempt at creating synthetic calculus to understand and systematically test effective decontamination protocols for ancient starch research.