# Which of the following is a test for measuring hardness?
A. Knoop
B. Toughness
C. Yield strength
D. Resilience
The correct answer is A. Knoop.
The tests most frequently used in determining the hardness of dental materials are known by the names
Barcol, Brinell, Rockwell, Shore, Vickers, and Knoop. Selection of the test should be determined on the basis of the material being measured.
The Knoop hardness test employs a diamond-tipped tool. The impression is rhombic in outline, and the length of the largest diagonal is measured. The load is divided by the projected area to give the Knoop hardness number (usually abbreviated as HK or KHN).
Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, Anusavice, Shen, Rawls, 12th Edition, Page No: 64
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