Wire Edge

Wire Edge

What are the criteria for judging that your instrument (that you have sharpened) is perfect for the procedure. Explain wire-edge.
Answer. Sharpness can be evaluated by sight and touch in following ways:

• When a dull instrument is held under a light, the rounded surface of its cutting edge reflects light back to the observer. It appears as a bright line running the length of the cutting edge. The acutely angled cutting edge of a sharp instrument, on the other hand, has no surface area to reflect light. When a sharp instrument is held under a light no bright line can be observed.
• Tactile evaluation of sharpness is performed by drawing the instrument lightly across an acrylic rod known as “sharpening test stick.” A dull instrument will slide smoothly, without “biting” into the surface and raising a light shaving as a sharp instrument would.

Wire-edge

• A wire-edge is produced when the direction of the sharpening stroke is away from, rather than into or toward the cutting edge.
• Avoid the formation of a wire edge characterized by minute filamentous projections of metal extended as a roughened ledge from the sharpened cutting edge. When the instrument is used on the root surfaces these projections produced a groove surface rather than a smooth surface.
• When back and forth or up and down sharpening strokes are used formation of a wire edge can be avoided by finishing with a down stroke towards the cutting edge.