Thank you for your encouraging words. I had never been to a live concert, and I believe I would always listen to music at reasonable volume levels. The buzzing sonic toothbrush was in contact with the opening of my ear canal for only a fraction of a second. I had that "full ear" sensation that lasted for over a month. Tinnitus kicked in 12 days after the incident. I started hearing it the evening of the day when I visited an audiologist. I can't imagine my audiologist doing anything to cause it. She performed a "bone-conduction" test... The fact that later that day I started suffering from tinnitus has got to be a coincidence.
Nowadays, my tinnitus seems a little quieter. I am hoping for the best. The alternative - one wrong move causing a lifetime of tinnitus - implies the world is a scary place...