I think a vet should not back down from a 12 week old puppy. I don't really know what he expected you to do to it. I mean, if you went all Ceasar on the poor pup, you would probably create a puppy that freaks out at the vet. That would make thinks easier down the line.
I wouldn't worry over-much about it at this point. I never conditioned Babs to have her mouth handled and teeth looked at, but when the vet was in there yesterday, she did not try to eat her.
Sometimes I think the best reaction to some things is no reaction. I teach my girls to be GENTLE when giving them a treat, and then I remind them to be GENTLE when they take a treat, from me or anyone else, and eventually, I use the GENTLE term with anything or anyone I want them to be careful around, babies, old people, vets, treats or no treats. It works.
Jenna, RN CGC & Babs, CD RA CGC HIC
Heidi, RA CGC
SG3 Odessa, SchH1, Kkl1, AD
Ninja, RN CGC & Milla, RN CGC
Joy, Star Puppy, RN CGC
Dolly CGC & Bear CGC