First, I just want to say how sorry I am for you and Maddie to have to go through all this. I can't believe they re-opened her to do the dental. I thought that was really dangerous!!??
Now, even if mistakes happen (is this a common mistake at all??) I cannot fathom the fact that the vet did not call you immediately and profusely apologize. It says a lot that the intern was the one who "manned up" and came to your house, and the vet couldn't even pick up the phone!!
I hope Maddie recovers well and quickly (Bandit had his first dental today too-- so he's in recovery mode). I hope you get a call from your vet and are able to express your frustration-- this even has me angry and frustrated!!
Hugs!