Many dentists report being put off the process of sharpening their periodontal instruments because textbooks often go into a great deal of detail about oiling the sharpening stone as a necessary part of the sharpening process. This, of course, implies that the instrument is not going to be inserted into the patient's mouth without further scrubbing and sterilisation. And yet we know that the sterilisation process itself will blunt the sharpened edge. Therefore, in practical terms, it is advisable to integrate the sharpening of your periodontal instruments at chairside as part of a patient's periodontal visit.

Instruments become dull very quickly during root-planing procedures, and it is necessary to resharpen them at frequent intervals over the length of an appointment. The sharpening stone should be sterilised, but it is not necessary to use a lubricant if instruments are sharpened regularly. 

Choice of Stones: 

Sharpening stones are manufactured in a wide range of shapes and materials. However, it appears that the dental supply houses only stock a very limited range, and therefore you may feel that your choice is restricted to those few. It is important to use a stone that is large enough for you to secure a firm grip, to reduce the chance of accidental slippage and trauma to your fingers during sharpening. Recommended stones for sharpening both Gracey and Universal style curettes include: 

I. No6. India wedge shape (SS6) (Hu-Friedy) 4 1/2" x 1 7/8" x 3/8" down to 1/8" thick.
This stone is good for sharpening up extremely dull instruments, but is too coarse for everyday maintenance of your curettes.

2. No 6A. Arkansas wedge shape (SSG6A) (Hu-Friedy) 4" x 1 7/8" x 3/8' - 1/8" 

This stone is made for a finer grit material, and is suitable for regular sharpening of curettes.
 

3. No299. ArkansasConical (SS299) (Hu-Friedy) 3 1/2" x 5/16" base.
This is a hard stone with a super-fine grit. Suitable for sharpening the facial surfaces of curettes.

Principles of sharpening
1. Learn how to detect a blunt instrument. With experience, you canjudge when to resharpen an instrument during root-planing through tactile feedback. A dull cutting edge will require the use of greater lateral forces against the root, and will crush or burnish the calculus rather than removing it cleanly. A visual cue to an instrument's sharpness is that a dull instrument will reflect light along the line of it's cutting edge, whereas a sharp cutting edge will not reflect light. Sharpen at the first sign of dullness.

2. Understand the design of your periodontal instrument (see Practice Information Sheet No 6). It is important to retain the curvature of the blade and the angle of the cutting edge. The angle between the face of the blade and the lateral surface of any curette is 70-80 Degrees. The best way to judge this angle is to place the sharpening stone to the lateral surface of the curette so that the angle between the face of the blade and the stone is 90 Degrees. Next, open this angle 10-20 Degrees by rotating the stone laterally. 

3. Maintain this angle during sharpening. Using short up and down strokes with consistent light pressure, sharpen the entire blade from shank end to toe. When approaching the toe, sharpen around it to prevent it from becoming pointed. 

4. Only the cutting edge of Gracey curettes should be sharpened. The curvature of the cutting edge of the Gracey curette blade from shank to toe needs to be preserved during sharpening. If the stone is kept in one place for too many strokes, the blade will be flattened. This can be avoided by turning the stone slowly as you sharpen with up and down strokes. 

5. Avoid excessive pressure that will lead to unnecessary shortening of the life of the instrument.

6. Avoid formation ofa 'tvire edge", which occurs when the direction of the sharpening stroke is away from, rather than into or towards the cutting edge.

7. The face of the blade can be sharpened using a cone-shaped stone applied to the face of the blade and moved with a side-to-side, back and forth motion. This procedure should be performed infrequently, as it weakens the blade by narrowing it from face to back. 

Many periodontists package well-sharpened fine instruments separately from newer, broader instruments. The use of fine instruments is often necessary during the maintenance phase of periodontal care in order to gain access to a residual pocket, particularly if there has been a favourable gingival response with firming up of the tissue consistency. Broad-bladed sharp instruments are ideal to remove heavier subgingival calculus deposits, particularly if the surrounding tissues are inflamed.

If you need further guidance on sharpening of periodontal instruments, an excellent text is: 

Pattison G, Pattison AM. (1992) Periodontal instrumentation - a clinical manual. 2nd edition. Reston Publishing Company, Inc. Virginia, USA. 

This material has been compiled with the assistance of Dr Louise Brown, Lecturer in Periodontics at the University of Melbourne. 

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