(2) The mounted-stone technique. The second technique for sharpening
dental instruments is the mounted-stone technique. This technique is especially useful in
sharpening instruments with curved or irregularly shaped nibs. Equipment consists of
mandrel-mounted stones, a straight handpiece, lubricant, two-inch by two-inch gauge,
and, again, the instrument to be sharpened. Mounted stones are made of two materials,
Arkansas stones and ruby stones (sometimes called sandstones). Ruby stones are
primarily composed of aluminum oxide. The ruby stone is comparatively coarse, has a
rapid cutting ability, and is used for sharpening instruments that are dull. Mounted stones
are cylindrical in shape and appear in several sizes. They have a fine grit and are used
with the straight handpiece. The stones permit rapid sharpening, but without extreme
care, will remove too much metal and may overheat the instrument. Overheating the
instrument will destroy the temper, thereby causing the instrument to no longer hold a
(3) The rotary-hone technique. The rotary-hone technique is the third
technique of sharpening instruments. The rotary hone was invented by Dr. E. L.
Kirkpatrick of Marquette University and it is called the E.L.K. Rotary Hone. The
equipment for this technique is the same as for the mounted-stone technique with the
addition of the hone itself. The hone attaches to the straight handpiece and provides a
table serving as a rest and a guide for the instrument. The advantages/disadvantages of
the rotary-hone technique are the same as that of mounted stones. However, greater
control of the instrument is provided by the table. Oil is used as a lubricant with this
technique as recommended by the manufacturer.
b. Instrument Sharpening Principles. Certain principles of instrument
sharpening MUST be adhered to in order to properly sharpen an instrument.
(1) Establish the proper angle. Before starting to sharpen, establish the
proper angle between the stone and the surface to be ground. The plane of the surface
being ground should be used as a guide. Sharpening entails reducing the surface of the
blade in relation to the dull edges; to accomplish this, reduce the entire surface--do not
create a new bevel at the cutting edge. Do not tilt the stone so that it cuts unevenly
across the surface being ground.
(2) Lubricate the stone. Always lubricate the stone while sharpening. This
avoids unnecessary heat, as indicated earlier, which changes the temper of the
instrument, making the steel softer. Avoid excessive pressure. This heats the edge,
even though the stone is lubricated. A light touch is essential. Sharpen the instrument at
the first sign of dullness.
(3) Wear safety glasses. Finally, the most important principle or precaution is
to always wear safety glasses, especially when using the mounted-stone or rotary-hone
techniques. The metal particles and the lubricant will be flying through the air and
inevitably will strike eyes or face; so be sure the wheel is rotated away from you. The
safety glasses are for your protection. WEAR THEM!