During my most recent checkup my dentist asked if I had any change in medication, so I just gave him the full run down of Estradiol, Spiro and Progesterone. He pretty much shrugged and said "OK". that was that. I did show up in a dress that day, so it was pretty obvious anyways.
I have to admit the first time I listed my HRT meds, it was with a mix of happy pride and being nervous. I had asked my GP before if he would want to take care of my hormones and based on his stupid comment I changed doctors in the same practice, I pretty much told the office manager I do not want him any more due to his bad bedside manners.
Most other doctors have not reacted at all, even during the times I did not present female. I am sure any medical professional who is somewhat up to date can figure out what is up simply based on the combination of meds. Dani is absolutely right, whatever you write on that piece of paper is confidential. I also agree that a doctor should know about all meds you take even tough at a dentist there is little need unless you need some dental surgery when they need to know about changes to your blood clotting.
Good luck at the dentist (yeah, my checkup ended in a cracked crown, then a root canal and now he discovered a wisdom tooth needs to be removed. Great.) - I hope you do not have to go through any of this.