pigment vs tooth enamel

pigment

noun
  • A dry colorant, usually an insoluble powder 

  • Any color in plant or animal cells 

verb
  • To add color or pigment to something. 

tooth enamel

noun
  • The hard, mineralised substance that makes up the visible part of teeth. 

How often have the words pigment and tooth enamel occurred in a corpus of books? (source: Google Ngram Viewer )