The hardness testing method for dental PMMA

The hardness testing methods for dental PMMA mainly include Rockwell hardness testing and Brinell hardness testing.

Rockwell hardness testing involves pressing a drill bit into the surface of a sample at a certain rate and recording the pressure required to press into the drill bit. This value is the Rockwell hardness value. Three different types of hardness testers, namely HRA, HRB and HRC, are usually used. When conducting the test, the sample should be placed steadily on the workbench and there should be no displacement during the test process. The thickness of the sample should be uniform and not less than 10mm. The size of the sample should be such that five points can be measured on the same surface, and the distance from the center of each measurement point to the edge of the sample should not be less than 10mm.

The Brinell hardness test involves applying a fixed load to the surface of the sample and then measuring the degree of elastic deformation on the sample's surface. This degree of deformation is the Brinell hardness value. The three different hardness testers commonly used are HBW, HBS and HBT.