I've had both of my knees replaced. When I did the first one, the recommendation was to take antibiotics before going to the dentist for the rest of your life. By the time I had the second one done, they were recommending them for only the first two years after the replacement. Now, they're back to recommending them for life again. I've been to the dentist numerous times since the second knee surgery and haven't taken antibiotics, and it hasn't been an issue. Same thing with my mother. She has mitral valve prolapse, and for decades was told to take antibiotics before going to the dentist. In the past few years, though, they've told her recommendations have changed, and she could stop taking them.

Interesting thing about polio. I never knew it was a class-based thing. My grandfather's mother (so, my great-grandmother) died of polio two days before her 41st birthday, while 8 months pregnant with what would have been her 9th child in 1935. One of her other eight children had polio, and she nursed him through it, but then got it herself. I asked my great-uncle (her youngest child, who was only three when she died) once if any effort was made to save her baby, who was far enough along to survive on her own. He said his dad, being already overwhelmed with eight kids and having just lost their primary caretaker, told the doctors to wait before removing the baby. So, she was stillborn because they waited, but that's how they knew it was a girl. Different times, man.