Impacted wisdom tooth removal, infection, abcess, burst, lymphatic infection, systemic infection, high fever, major organ damage...et cetera, et cetera.
I recently had a very severe dental infection that several specialists could not diagnose. it lasted for about two months (with strong antibiotics), went away and came back even worse. it's been gone now for about 3 months, but it was extremely painful and disfiguring. I can easily see how it could spread and become fatal. very scary.