APPLICATION OF SCRATCH HARDNESS TESTS FOR EVALUATION OF PARTIALLY-SINTERED ZIRCONIA CAD/CAM BLOCKS FOR ALL-CERAMIC PROSTHESIS

摘要

Scratch hardness of partially sintered dental zirconia CAD/CAM blocks was determined using the load at which material removal by scratch occurs in a transient mode between the ductile and brittle manners. Scratch hardness increased at low indent loads and decreased at high indent loads. Specifically, the slope of the ascending linear relationship at low loads represents the extent of plastic deformation while the load at the beginning of the descending slope is related to crack opening by scratching, both of which govern machinability of the blocks. Here we demonstrate that the scratch hardness test reveals the machinability and shrinkage of CAD/CAM zirconia, two important pieces of information that may be utilized for fabrication of good dental prosthesis.