Got back from Dr. Sturn's office (see the previous post for more info on why I went), and it turns out I'll need a root canal and a new crown for the tooth. Dr. Crackers, the dentist who did the original crown, didn't adequately glue the crown in place and decay had taken place underneath it.
More interestingly, Dr. Crackers billed me for a post and crown procedure when he did this, but Dr. Sturn says that there's no post there. He showed me my x-rays, and then showed me x-rays of a post so that I could see the difference. So apparently, Dr. Crackers is not only incompetent, he's also dishonest. A great combination in a medical caregiver, huh?