periodontal knives. Sharpening stones are recommended for curettes, chisels, and scalers.
Sharpening stones are available in various grits (textures) and designs to meet a particular need. The Ruby and Arkansas stones are the most commonly used. The Ruby stone is fairly course, cuts rapidly, and is used primarily for initial sharpening of very dull instruments. The Arkansas stone has a fine grit and is used to attain a sharp edge.
Depending on their design and method of use, sharpening stones are either mounted or unmounted. Some are mounted on mandrels for insertion into the dental handpiece, others are mounted in mechanical devices known as mechanical sharpeners. Unmounted stones may be rectangular, cylindrical, or have a special shape. These stones are often lubricated with water or oil to avoid clogging the stone's pores with metal particles as the instrument is ground.
Regardless of the device used, instruments are sharpened by grinding or polishing the surfaces that form the cutting edge. Instruments should be sharpened after every use. If the cutting edge has been markedly reduced because of sharpening, discard the instrument rather than risking the chance of breaking it during a treatment procedure. Keep in mind that the amount of metal ground away by mounted stones is much greater than that removed by unmounted stones.
The most commonly used periodontal knives are the Kirkland #15 and #16, and the Orban #1 and #2. Both types may be sharpened with a hard felt wheel mounted on a dental lathe or handpiece. It is difficult to maintain the knife's functional shape and blade bevel with either technique.
Kirkland knives have three cutting edges to sharpen, the inner, outer, and back edge (figure 6-16). The Orban knives have only two cutting edges, the inner and outer edges (figure 6-17). Apply an abrasive, such as chrome rouge, to the felt wheel to aid in the sharpening process. Sharpen both sides of each edge. Use the following technique:
Hold the knife handle between your thumbs and forefingers (both hands). Stabilize your hands or elbows on the work bench.
Hold the knife so that the felt wheel rotates away from the cutting edge.
Figure 6-16 .- Kirkland knife cutting edges: inner (1), outer (2), and back (3).
Figure 6-17. - Orban knife cutting edges: inner (1) and outer (2).
Place the knife against the wheel at an angle consistent with the bevel of the blade. Gently apply the knife to the wheel. Sharpen both sides of each cutting edge. Check each edge for sharpness.
If using a stone, establish the same alignment as with the felt wheel, then draw the stone across the bevel of the blade.
Curettes are the most commonly used scaling instruments. McCall curettes (universal curettes) have two cutting edges and are sharpened on both sides. Gracey curettes are sharpened only on the outer curve. 6-13