Knoop hardness number

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Knoop hardness number

a number obtained by dividing the load in kg applied to a pyramid-shaped diamond of specific size divided by the projected area of the impression: KHN = L/A, where A= the projected area of the impression in mm2 and L= the load in kg; used for measurements of hardness of any materials, especially very hard and brittle substances such as tooth dentin and enamel.