brush one's teeth vs brush up

brush one's teeth

verb
  • To clean one's teeth, especially by using a toothbrush and toothpaste. 

brush up

verb
  • To paint, or make clean or bright with a brush. 

  • To review; to improve an existing but rusty or underdeveloped skill. 

How often have the words brush one's teeth and brush up occurred in a corpus of books? (source: Google Ngram Viewer )