Andrew,

Have you tried Chlorhexidine (aka: Peridex, Periogard, and a few others)? It is used to treat gingivitis and periodontitis and it is by prescription only. My doctors have recommended I use it before and after certain dental procedures. It is pretty potent so they have me dilute it with water before using. It does stained my teeth, so when using it I end up with more frequent cleanings.

I've also used an antibiotic before & after some dental procedures.

And like PaulB and so many others, I also had teeth removed post-RT and had HBOT to promote healing.