there is blood flow to the gingival tissue around the tooth. If the tooth were still infected as you say, there would be one or more of the following: 1)periapical lucency secondary to chronic periodontitis 2)suppuration 3)spontaneous pain 4)percussion sensitivity 5)abnormal (lingering) response to cold
The answer is that most endodontically treated teeth are no longer infected. The canal can never be sterilized, but any residual bacteria are effectively entombed by gutta percha and sealer, and are killed. Otherwise one would see (as occasionaly does happen) one or more of the above signs/symptoms. Your bodies own immune cells sweep in and, with no place to hide anymore, the periapical infection is eliminated.
Vague complaints of fatigue, headaches, etc. cannot be correctly attributed to endodontically treated teeth unless one or more of the above are present.
Its just science. Not difficult science. Basic. Scientific method, studies, etc.
NOT pseudoscience. Sorry I don't speak your language.
I think this is probably not the place for me. The paranoia level is just ratcheted up a bit too high for my tastes.
Best of luck to everyone here. Take some basic Science classes. Get an education. Trust science, not vague, internet opinions, no matter how strongly held, even my own.