cementum vs plaster of Paris

cementum

noun
  • A bony substance that covers the root of a tooth; cement. 

plaster of Paris

noun
  • A hemihydrate of calcium sulfate, made by calcining gypsum, that hardens when moistened and allowed to dry; used to make casts, molds and sculpture. 

How often have the words cementum and plaster of Paris occurred in a corpus of books? (source: Google Ngram Viewer )