You should address this issue first with your supervisor and then with HR. In the US at least, this would not be something the supervisor should be doing.
You need to directly talk to your supervisor, tell him or her that you were upset at your medical privacy being violated and ask specifically that it not happen again.
It is too late to undo this instance, but if it upsets you enough, you should talk to HR about it as this type of thing is something that companies are generally very careful to avoid. Only people who have an actual need to know the details of your medical issues (such as HR people who have to get medical accommodations approved and paid for or HR people who help you get short-term disability or supervisors who have to approve the time off (especially if the request is unusual like needing every Friday afternoon off to do dialysis) have a right to know exactly why you are out sick. Even supervisors generally don't need the details (although providing some generally gets these things approved much quicker and with less push back) but may need a doctor's note. Out sick is reason enough for people who have to take over your work while you are out.
You don't need to feel humiliated though, very few people really would find oral surgery to be odd or unusual.