I lucked out. Turned out it was the temporary crown that fell off; I have so many crowns at this point I can't tell which are new and which are old. So thankfully, the hygienist was able to clean the temp. crown up, scrape the cement off the tooth (that was NOT fun) and re-cement it. The tooth is a bit sensitive now after all day without the crown covering it. I may try some Tylenol again. Hopefully, it will calm down soon.