Microhardness and elastic modulus analyses
The dynamic microhardness (DH) and elastic modulus (E) of the materials were evaluated using a dynamic ultra-micro-hardness tester (DUH-211 S; Shimadzu Co., Kyoto, Japan) equipped with a Berkovich indenter (115° triangular pyramid-shaped). Three samples were prepared for each subgroup. Once the experimental setup was completed, all specimens were demolded and their surfaces were wet-polished with minimal hand pressure, using 800, 1,200, 2,400, and 4,000 grit silicon carbide sandpapers for 30 s each.During the load-unload test, the load force was continuously increased and decreased at a constant speed ranging from 0 to 100 mN. The indenter was held at the maximum load and minimum load for 10 s and 5 s, respectively. The test force (F) and indentation depth (h) were automatically recorded as the indenter pressed against the specimen. The recorded data were then used to generate a force-depth curve, from which the dynamic microhardness (calculated using Eq. 1) and elastic modulus (calculated using Eq. 2) were obtained and collected by the software. Both equations were obtained from the manufacturer’s manual for the dynamic ultra-micro-hardness tester.1) DH = α × F/hwhere 2) 1/Er = (1-Vwhere In this study, indentations were randomly made on the polished surface, with 0.5 mm between each indentation and the specimen periphery, until ten representative test force and depth curves were obtained for each specimen [