I understand your shock. When we took our little 4lb rescue in for his cleaning he came home with only 7 teeth left in his little mouth. Now he has this adorable habit of letting his tongue hang out of the side of his mouth.
I'm sure he was in a lot of pain with all those bad teeth and his whole personality changed after he healed up. It was really just a few days after his dental that he was chewing on crunchy food again. He just chews it at the front of his mouth.
Now he doesn't eat any diferent than the rest of the pack.
And my vet said the same thing about yorkies - dental problems are very common so don't kick yourself too much. Just watch your little one perk up now!