A mold used in duplicating a denture consists of a tissue side mold section and an exterior side mold section. The tissue side mold section is made of a dimensionally stable material, such as dental stone or an addition-cured silicone rubber, so that the tissue side of the denture can be accurately reproduced at a later time. The exterior side mold is made of a resilient material, so that the original denture and its duplicate can be removed from the mold. The mold sections are housed in a two part flask that was initially used to fabricate the mold sections. The mold is fabricated by the steps of forming an impression of the original denture, and of fabricating a replacement denture using this mold.