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 value required to press into the drill bit. This value is the Rockwell hardness value. The three different types of hardness testers commonly used are HRA, HRB and HRC. 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 ensure that five measurement points can be measured on the same surface, and the distance from the center of each measurement point to the edge of the sample shall not be less than 10mm.

Brinell hardness testing involves applying a fixed load to the surface of the sample and then measuring the degree of elastic deformation on the sample surface. This degree of deformation is the Brinell hardness value. Three different types of hardness testers, namely HBW, HBS and HBT, are usually used.