It hasn't happened to Maggie - I brush her teeth every few days with the toothpaste from Petco.  It's mint flavored with a picture of a Yorkie on it.  She LOVES it and that's probably the only reason it's easy to brush her teeth 
 
 
Maybe the toothbrush wasn't soft enough and bothered her gums??  I don't know - I wish they could talk and tell us what's going on 
