teeth always in pairs?

Rasz39

Gummi Bear has her canine teeth coming in. I'm not too surprised, since she's had all her teeth come in about a month or so early. But every set so far has had the bottom come in where the L & R have cut through within a day of each other and then about a week later the top set come in.

The potential problem we've got this time is that she's been miserable for about a solid week and now there are three little points popping through. The bottom left hasn't popped and when I touch her gums, I don't even feel it.

Anyone have teeth not appear in pairs? or have a delayed half of a pair before? Since all of them have come in as pairs, and so fast, I'm a little startled and she's been so miserable (and acting out) that I'm wondering if I should be worried.