Pixie's puppy teeth are coming, the ones in the front, top and bottom. It's amazing how fast they come, compared to people. But I just noticed that she has only one upper canine, on her left side. I thought maybe the other one had fallen out (even thought the vet told me they come out last), but there is no hole or mark on her gum, like you would see after a tooth has fallen out. The gum there is completely smooth. Is that normal?