Testing the Sharpness of the Gracey Curette Blade
Sharpening Angles
TEST STICK POSITION Position both the test stick and the terminal shank of the Gracey instrument parallel to each other at 12 o’clock. INSTRUMENT POSITION FOR RIGHT HANDERS In your dominant hand, hold the instrument with a modified pen grasp. For odd-numbered Gracey blades, the toe will be pointed toward you. Bring the instrument handle behind the test stick with the cutting edge to be tested against the left side of the test stick and fulcrum on the right side. For even- numbered Gracey blades, the toe will be directed away from you and you will bring the instrument handle in front of the test stick. Hold both the terminal shank and the test stick at the 12:00 position. Be sure not to place your ring finger on the top of the test stick. Instead, position your fulcrum against the side of the test stick opposite the cutting edge to act as a fulcrum while testing. Testing must be done at the same angle that the blade is used for scaling. INSTRUMENT POSITION FOR LEFT HANDERS In your dominant hand, hold the instrument with a modified pen grasp. For even-numbered Gracey blades, the toe will be directed toward you. Bring the instrument handle behind the test stick with the cutting edge to be tested against the right side of the test stick and fulcrum on the left side. For odd- numbered Gracey blades, the toe will be pointed away from you and you will bring the instrument handle in front of the test stick. Hold both the terminal shank and the test stick at the 12 o’clock position. Be sure not to place your ring finger on the top of the test stick. Instead, place your fulcrum against the side of the test stick opposite the cutting edge to act as a fulcrum while testing. Testing must be done at exactly the same angle that the blade is used for scaling, which is visually achieved when the terminal shank is parallel with the test stick. TESTING THE CUTTING EDGE Press the cutting edge laterally into the test stick and release. Test the entire length of the blade. A sharp edge will bite into or grab the test stick. When the edge is removed it produces a metallic sound. If the cutting edge slides over the surface of the test stick it may indicate the blade is still dull or the terminal shank is not positioned correctly.
110˚
70˚ The goal of instrument sharpening is to create a sharp blade while preserving the ordinal shape of the instrument. Whether sharpening universal curettes, area-specific curettes or sickles scalers the angle between the stone
and the blade should always be 110º. The It’s About Time sharpening technique translates these degrees of angulation to simple time positions on a clock face.
Chart of Angles
135˚
110˚
45˚ NOT ENOUGH ANGULATION When the internal angle is greater than 80°, the blade becomes bulky and is difficult to adapt to the tooth.
70˚ TOO MUCH ANGULATION
CORRECT ANGULATION
Instrument Position for Right Handers
R
When the internal angle is less than 70°, the blade becomes weak and also dulls quickly.
When the stone is correctly placed against the blade, the internal angle of approximately 70° is maintained.
135˚
110˚
90˚
90˚
45˚
70˚
Instrument Position for Left Handers
L
135˚
90˚
90˚
45˚
21 IT’S ABOUT TIME
22 A CLASSIC APPROACH TO SHARPENING SCALERS & CURETTES
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