Four- Number Instrument*

Function :-

Numbers on handle indicate width of blade, angle of cutting edge, length of blade, and angle of blade

1 .Indicates width of blade in tenths of millimeters
Example: 20 indicates a width of 2 mm
2. Indicates angle of cutting edge of blade in relation to handle
Example: 95 indicates a cutting edge angle of 95 degrees
3. Indicates length of blade in millimeters
Example: 8 indicates a length of 8 mnm
4. Indicates angle of blade from long axis of shaft
Example: 12 indicates a blade angle of 12 degrees

The designation for the instrument described above is 20-95-8-12; the number of instrument size is indicated on the handle.
Examples of four-numbered instruments: Angle Former, Gingival Margin Trimmers-Mesial and