The Automatic Option

A multitude of automated sharpening machines are currently on the market. When investigating an automated sharpening device, consider whether it sharpens the lateral sides of the blade or the face. Removing metal from the lateral side of the working end is preferred because it maintains the overall strength of the instrument, prolonging the instrument’s usefulness.¹ Also consider whether the device has the space to move the instrument in a pendulum-like motion across the stone to maintain its curvature, which is necessary with Gracey curets and some sickle scalers (Figures 1A and 1B). Maintaining the original shape of the instrument is as important as having a sharp cutting edge. Finally, make sure the manufacturer’s instructions are followed carefully during operation to avoid alteration of the basic design of the scaling instrument.

In general, automated devices consist of sharpening guides and rotating stones. They require accurate set-up and angulation for each instrument type.

HONING MACHINES

Typically, an automated sharpening device is referred to as a honing machine, which is a bench-type piece of equipment with specially designed honing disks mounted on top of the machine. The instrument is then positioned by a sharpening guide according to the instrument classification (Figure 2). The stones are mechanically rotated as the working end is pressed against the stone. The disk rotates up to a powerful 7,000 rpm.

These devices will remove metal from either the face or lateral sides of the blade; the clinician controls the pressure. The honing machine rapidly sharpens instruments, thus saving time. However, the clinician must use care in precise positioning of the instrument and judicious application of pressure. In addition, although sharpening guides assist with proper angulation of instrument to stone, the gentle curve of the Gracey or the flame-shape of some sickles can be altered if a pendulum-like motion from heel to toe is not maintained.

Another example of a mechanical sharpening apparatus that uses ceramic stones is the battery-operated honing device (Figure 3). This sharpener contains an instrument guide channel and a vertical backstop to guide blade placement. A template is provided to guide blade positioning for sharpening either sickle scalers or universal curets along with a separate template to sharpen Gracey curets. It also has a toe guide to assist the clinician in maintaining the rounded toe when sharpening curets.

While this device removes metal from the lateral side of the working end, the clinician must be careful in maintaining the contour of flame-shaped or curved cutting edges. The entire cutting edge of universal curets can be placed flat on the stone, however, the contoured cutting edges of Gracey curets and some sickle scalers need to be moved in a pendulum-like motion from heel to toe to maintain the design curvature.

MOUNTED STONES

Mandrel-mounted stones are used with a slow-speed handpiece. The stones are cylindrical in shape with either a flat end or cone-shaped end. The most commonly used stones are Arkansas and Ruby. The rotating stone should be larger than the diameter of the instrument blade that is being sharpened. While the handpiece is activated at a slow speed, the stone is passed over the face of the blade to sharpen both cutting edges at once. This method requires stabilization of the instrument in one hand and the handpiece in the other. Again, the clinician must be experienced with the application of pressure as too much of the face of the blade can be removed quickly, thereby weakening the working end of the instrument.

BUILT-IN STONES AND SHARPENING GUIDES

A new device for sharpening instruments during debridement features a stone built into the handle of a dental mirror (Figure 4). The stone does not need to be lubricated and is easy to clean. The stone is rinsed with water and placed in an ultrasonic bath for 15 minutes and then sterilized as usual.

Sharpening guides can also be used in conjunction with hand-held stones (Figure 5). These devices provide the clinician with the accuracy of instrument placement against the stone while manually controlling the motion and pressure. With this technique, the stone is stationary while the instrument is moved across the stone in a back and forth motion. A pendulum motion is necessary for flame-shaped or curved cutting edges.

CARE OF STONES

Stones require care to maintain their longevity. They should be lubricated as specified by the manufacturer before use. Stones require either water or oil as a lubricant; the two lubricants should never be interchanged.² The lubricant is used to reduce heat from friction, to prevent metal particles from embedding into the stone, and to prevent dryness.³ However, some manufacturers suggest that stones may be used without any lubricant when instruments are being sharpened during scaling and root planing because oil cannot be properly sterilized.²

Cleaning the stone removes imbedded metal particles and lubricant build-up, and should be based on manufacturers’ guidelines. Stones can be cleaned in an ultrasonic or scrubbed with a brush and hot water, then properly packaged, and sterilized with every use. Some manufacturers require lubrication before sterilization. Stones lubricated with oil should be wrapped in a gauze square to absorb excess oil during sterilization. To maintain the useful life of the stone, sharpening should not be limited to one area of the stone. Using the entire stone’s surface can prevent grooving of the stone.

MAINTENANCE OF A SHARPENED INSTRUMENT

Proper care can maximize the longevity of sharp instruments. Instruments should not be overly crowded in an ultrasonic prior to sterilization because they can become dulled when instruments bump against each other in the ultrasonic bath.⁴ Stainless steel instruments may be sterilized with saturated steam (250° F), chemical vapor (270° F), or dry heat (340° F) without dulling the cutting edges. However, saturated steam sterilization does have a dulling effect on the cutting edges of carbon-steel instruments.⁵ Application of working strokes against the margin of an amalgam restoration or fabricated crown can also lead to dulling of the edge. Instrument blades should be regularly inspected. Those that have become thin from continuous sharpening and use should be discarded to prevent breakage during debridement.⁶

Instrument sharpening is an important procedure for maintaining the usefulness of instruments and for effective deposit removal. The plethora of equipment and device options can be overwhelming. For effective instrument sharpening, the clinician should choose equipment that is easy to use, maintains the original design of the instrument, and is cost-effective.

ACKNOWLEDGEMENT

Special thanks to Darice Pacak, RDH, MSEd, for her professional expertise.

REFERENCES

1. Nield-Gehrig JS. Fundamentals of Periodontal Instrumentation and Advanced Root Instrumentation. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2000.
2. Nield JS. Fundamentals of Periodontal Instrumentation. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2008.
3. Claney P. Sharpening hand cutting instruments. Dent Assist. 1986;55:23-24.
4. Wilkins EM. Clinical Practice of the Dental Hygienist. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2005.
5. Paquette OE, Levin MP. The sharpening of scaling instruments: II. A preferred technique. J Periodontol. 1977;48:169-172.
6. Perry DA, Carranza FA, Beemsterboer P. Techniques and Theory of Periodontal Instrumentation. Philadelphia: WB Saunders; 1990.

From Dimensions of Dental Hygiene. September 2007;5(9): 20-23.