I would bet the metal is silver. It was commonly used in making dentures, and still is sometimes. There's a reason that Paul Revere, a silversmith by trade, also made dentures! I have found online several examples of silver and porcelain dentures, but the only ones from the 1860s and before only used silver and did not have the pink 'gum' part. But then I only found two or three examples (one found on the Shiloh battle field), so their may be more out there that would help date yours. BTW - Paul Revere helped identify the body of a U.S. general who had been buried in a mass grave by recognizing the dentures he had made for the general - the first case of identifying a body by dental records (or memory in this case)!