Micro-indentation Hardness

¹ Department of Dental Materials, Marquette University School of Dentistry, Milwaukee, Wisconsin

Knoop and Vicker's micro-indentation hardness values for loads of 1, 5, 10, 25, 50, 100, 500, 1,000, and 10,000 gm. were reported for human enamel and dentin, for methyl methacrylate, silicate cement, amalgam, gold foil, gold band, two casting golds, cast copper, Ticonium, and two steel test blocks.

The results of Meyer analysis of the tests were presented in the form of tables and graphs of hardness and exponent, n, as functions of load.

Both Knoop and Vicker's hardness increased with increasing load until a maximum value was reached for a load of 50-100 or 500 gm. A slight decrease in hardness value resulted from further load increase.

Reproducibility of results improved with increasing loads.

For the materials here tested, the exponent, n, in the relationship L = a dⁿ did not exhibit the type of variations at very low loads (5-10 gm.) claimed by other investigators.

It is advocated that the test loads be reported together with Knoop and Vicker's micro-indentation hardness values. This is particularly desirable when low loads are used.