It's amusing how selective is my memory about UTMB. I remembered lately about some post-UTMB moments. And they weren't so great actually. On the night after the race, I was feverish, feeling sometimes very cold, sometimes fairly hot. And obviously I didn't sleep very well. Also, some tooth pain started before that night. I remember only now that I didn't enjoy so much the final banquet because of that: I couldn't chew properly. This tooth pain lasted for a couple of days.
I've seen quite a few blog and forum entries talking about tooth pain while/after running. Several explanations are given, usually based on abnormal mouth acidity level. This might be caused either by acidic energy drinks, lactic acid in the blood, or dried mouth due to heavy breathing. However, none of these theories seem to hold very well.

Ultra selection.