STUDY ON THE SURFACE OF RESINS THAT BURN WITHOUT RESIDUES IN THE LOST-WAX PROCEDURE

Statement of problem. When compared with waxes and prefabricated compo nents made of dental alloys, processing resins is difficult and often results in a less accurate fit. The exact linear dimension is hard to realize, as the materials required for a dental casting are adjusted t o dental waxes, and usually there are no special processing instructio ns for these resins. Purpose. The surface structure of 16 residue-free burning resins was determined to find which could enlarge the range o f application for waxes in the dental casting technique. Material and methods. A total of 480 specimens (30 castings for each of 16 resins) were marked with an individually cut pyramid, which left an impression in the resin. This was distinctly visible in the metal after casting in ''the lost form.'' The surfaces of these 480 specimens were measure d in three dimensions with a positioning aid ''before casting in resin '' and ''after casting in metal'' by the Perthometer micrometer. ALL s pecimens were treated identically by the lost-wax process by using the rotation symmetry of the muffle. The differences in the surface data before casting in resin and after casting in metal characterize the qu ality of the particular resin. Results. Surface roughness differed bet ween the 16 resins in the range of micrometer. Conclusions. With the d ental casting technique, it is recommended that some resins replace wa xes or wax-resin compositions.