I know what it is like to itch - when I had my shoulder surgery a couple of years ago my feet and ankles itched so bad and I could not scratch them with my hands because I was all bound up with things to keep the shoulder in one place. I used my feet to scratch with and I wore holes in my ankles, but the itching drove me crazy. I am pretty sure it was from the high dosage pain meds.
Hope you get relief soon! And the dentist definitely needs to know what happened. Is he some sort of spa dentist?