Most small breed dogs turn into little piranhas around 5-6 months of age. Their baby teeth often DO NOT fall out, but must be removed. Most people have the baby teeth pulled when their pup is spayed or neutered. Higgins baby teeth were still firmly in his jaw when he was neutered, so we had to wait. All the baby teeth except his four big canines fell out okay, but he just had to have the canines pulled.
Yorkies ain't cheap.....