My favorite conspiracy theory stuff are the multiple unused caries vaccine patents by the dental care industry.
I asked my dad about it (career Air Force). He laughed and said that gasoline consumption was a major logistics problem for the military. If there were 100 mpg carburetors, the military was going to use them, and to hell with any patent blockade.
(Note all the problems the Germans had in WW2 when the US severely damaged their oil refineries.)
Merck & Co 1979: https://patents.google.com/patent/US4287173A/en
Lion Corp 1983: https://patents.google.com/patent/US4693888A/en
In all likelihood these just didn't work, but the commercial interest to not have caries immunization is just too juicy not to theorize!