OP, you keep laughing/brushing off these serious issues with your dad.
I truly believe that you are misplacing your anger and frustration here.
I say this will all due respect.
Very SERIOUSLY.... it is your dad/parents that you have the issue with.
You can change dentists, you can report it to the correct authorities who have oversight in these matters... (and, perhaps you would have valid reason) you can do whatever... None of that is not going to change what is really troubling here.
But, I am telling you this with all due respect and your own best interests at heart...
Your parents are the real issue.
There is nothing good about the invasion of privacy and the control, etc.... that your parents are committing.
You are an adult, married, adult.
It is nothing other than wrong that they assume this kind of access to information and control.
You really need to take responsibility for yourself and your own health, and I cannot recommend to you strongly enough that you begin to create some more normal and healthy boundaries with your parents.
And, to be honest, I do not even suggest 'having a talk' with them.
(only likely to create needless drama)
Like the NIKE commercials.
JUST DO IT