It's hard to imagine his fast food tasting any good, judging from his extremely bad taste in the whole perverted matter.
In the "old days" virtually all teeth were crowned by cast gold restorations. Dental gold was often a mixture of actual gold with other metals placed into the mixture for hardness. Relatively speaking, the price of gold at the time was less than what it is now, so quite a few people across the economic spectrum may have had these in their mouths. If they chose to omit a cast restoration like this, then the tooth could be pulled out or might have been allowed to remain in use until it simply rotted out. What the narrator claims to be a tooth is a cast gold crown or 3/4 quarter gold crown with "Pontic" or false tooth soldered or cast alongside the other restoration in order to fill a space where another tooth may have been missing. Crowns don't normally have DNA present unless the tooth and crown fracture off/out together. Without dental records, this is an interesting story but unlikely that the tooth could be tied in any way to Admiral Yamamoto.