Toothache

I went to the dentist the other day, I had my biannual checkup. I don't recall when I suddenly switched from an annual to a biannual schedule, it's definitely twice as expensive. But this appointment was good timing, I have a toothache.
The assistant took an x-ray of my sore molar, the same molar the dentist filled 6 months ago. I figured it was just sensitivity to the filling, but that should have faded over time, this was getting worse. Maybe I pulled the filling loose. But the dentist says he can find nothing wrong with my tooth. It may have a crack which would be almost impossible to see on an x-ray. If it persists, I can go see an endodontist, which will surely cost a packet of money. The dentist said I could wait and see if it would clear up, or get worse, it's not showing any signs it needs urgent intervention.
As I left the dentist, they gave me a little bag with a toothbrush, some toothpaste, and some floss. I didn't look too closely at the bag, it had a cute little tooth pattern on it. But then I got the bag home, emptied it out and set it on a white surface. The bag was transparent, I could see the pattern through both sides, and suddenly my toothache seemed a lot worse.