Although I don't have the data to support this scientifically (yet), I am convinced that the monolithic polymethyl methacrylate (PMMA) denture is the best denture to use for a conversion prosthesis (rather than a denture with denture teeth or teeth that are adhered to a denture base, or even a 3D printed denture.) I found a pretty easy way to make a denture in preparation for the the conversion prosthesis combining the ease of CAD/CAM and convenience of injection molding (Ivobase). Enjoy the slides:
Here you can see the teeth made out of Alike PMMA and then Ivobase denture base acrylic injection molded to the full arch of teeth. Note the lack of porosity in the Alike teeth and Denture Base material. The acrylic in the intaglio area is Alike PMMA used to pick up the Smart Denture Conversion Ti base. You can see porosity in that acrylic, but also note the homogeneity of the prosthesis.