instrument formula

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A method of defining dental hand instruments devised by G. V. Black (1836–1915). It consists of three figures (sometimes four). The first figure denotes the width of the blade in tenths of millimetres; the second denotes the length of the blade in millimetres; and the third describes the angle of the blade in relation to the shaft and is measured in hundredths of a circle (centigrades). A fourth number is added if it is necessary to additionally describe the angle of the cutting edge to the instrument shaft, such as for margin trimmers; the fourth number is entered in brackets as the second number of the formula.

Subjects: Dentistry.

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