Dental calculus is when hard, mineralized plaque builds up on your teeth. It's often yellow or brown in color and can cause tooth decay if not removed regularly. Full definition
Restricted diversity of dental calculus methanogens over five centuries, France — Hong T. T. Huynh — Scientific Reports — May 2016 (microbiomedigest.com)
Using advanced sequencing technologies, University of Oklahoma anthropologists demonstrate that human DNA can be significantly enriched from dental calculus (calcified dental plaque) enabling the reconstruction of whole mitochondrial genomes for maternal ancestry analysis — an alternative to skeletal remains in ancient DNA investigations of human ancestry. (sciencedaily.com)
A new era in palaeomicrobiology: prospects for ancient dental calculus as a long - term record of the human oral microbiome — Christina Warinner — Philosophical Transactions of the Royal Society B — December 2014 (microbiomedigest.com)