Denture bases printed from a pre-polymerized block via additive technique, using photon S desktop 3D printer* that relies on SLA technology and post cured by post curing unit.

Retention was measured for both groups using the universal testing machine. Modification in each denture was made where two small metal tubes (3 mm diameters) were placed a few millimeters above the laterals in maxillary dentures by self-cure acrylic resin. The distance between the right tube and the geometric center was almost the same distance as between the left tube and the geometric center. The exact distance was checked using an orthodontic wire.

The fitting surfaces of each upper denture was sprayed and scanned after finishing and before delivery, then was saved as an STL file after flipping of the denture's fitting surface to resemble the cast surface. Geomagic software was used to evaluate the accuracy at which the master cast STL file was selected as a reference data and the STL file of the flipped fitting surface of the denture was selected as a measured data. Both files were automatically aligned together by selecting the "best fit alignment "icon. The accuracy of the denture bases generated in a color map according to the 3D deviation between the denture base and reference data. Blue color indicates negative deviation (tissue compression), yellow to red color indicates positive deviation (misfit with space) while green color indicates measured deviation below 0.2mm.