Sharpening may be the most critical factor in periodontal therapy as it has the potential to affect therapeutic goals, musculoskeletal injury, instrumentation efficiency, operator fatigue, time management, and stress. For many periodontal clinicians, sharpening can be the one limitation in achieving successful nonsurgical therapeutic outcomes.
Without an automated system, the use of a sharpening stone can be a highly subjective, in exact science. Despite the time and effort devoted to sharpening, instruments may still perform poorly or be inconsistent in holding an edge. This means that the desired benchmark is not being achieved and technique must be revisited.
BEVEL AND CONTOUR
The function of the curet is dependent on a properly established blade bevel that is consistent throughout the full length of the blade and maintenance of the contour or original shape of the instrument. The blade bevel relies on a precise angle relationship between the instrument and the stone, which is not subject to wavering as strokes are initiated. Contour is based on maintaining the curvature of the toe while also keeping lateral edges parallel throughout the life of the instrument.
Contour is an often overlooked component of sharpening. Sharpening strokes may be undertaken with a well-established angle relationship, forming a properly set bevel. However, if the curvature of the toe is not kept consistent with the original design of the instrument, it will fail to conform to subgingival root morphology. Without proper attention to keeping the lateral surfaces parallel, over a period of time curets may unintentionally assume a new identity as sickles or quasi-sickles (Figure 1). This creates a serious problem when the instrument is used subgingivally as pointed toes can carve deep grooves in root structure that can harbor pathogens.
Self-assessment is critical to maintaining consistency and achieving a benchmark in sharpening. Because the vast majority of clinicians use the stationary instrument/moving stone technique, which permits chairside sharpening at the first sign of edge loss, this approach is addressed.
Preparation of the lateral surfaces is a simple matter of establishing and maintaining the instrument and stone in each respective position and plane of movement. Problems can occur when sharpening strokes are initiated, resulting in the instrument wobbling due to pressure and movement of the stone against the blade and/or the stone moving out of its established plane. Observe the top of the instrument to check for stability. It should remain motionless as strokes continue, regardless of pressure, and the stone should stay confined to its established plane. Rigid stabilization of the instrument can be challenging but this is fundamental to creating a precise bevel.
GRASP AND STABILIZATION
The grasp used in the nondominant hand holding the instrument is key. Many clinicians are taught to hold the instrument with a spread modified pen grasp, which is appropriate for positioning, but when a stone moves against the instrument, it is no longer stable (Figure 2). This approach creates two problems—instrument movement and musculoskeletal strain. The nondominant hand cannot exert the same force as the dominant hand, making it nearly impossible to prevent the instrument from wobbling as lateral pressure is applied with the stone. Increasing the grasp pressure on the instrument to counteract this movement creates painful stress and strain in the nondominant hand and contributes to musculoskeletal injury. A stronger and more secure approach is the palm grasp with a three-segment spread stabilization of the instrument that takes advantage of the bony tissue of the hand (Figure 3). A second component is the counter edge. Clinicians using a sharpening guide to position their instrument and stone may be accustomed to or dependent on a counter edge.
A freehanded approach may also be used but it is dependent on adhering to prescribed angle relationships. A novice clinician should not undertake this method. With the freehanded method, arm position is integral to keeping the instrument stable in the nondominant hand and to the stone moving in a confined plane of movement. To illustrate this principle, hold the instrument and stone in front of you with your elbows slightly lifted and begin sharpening. Note the lack of finite control you have on the instrument position and the stone’s plane of movement. Now pull your elbows into your sides and tuck them into your ribcage (Figure 4). This is establishing a fulcrum for your hands and ensures that you can effectively control the movement and stabilization of the stone and instrument.
Establishing a secure and unyielding method for keeping the instrument perfectly stable regardless of the pressure applied is the first element of achieving a consistent outcome in sharpening. The formation of a bevel that spans the full length of the blade along the lateral edge can be assured with strokes that are confined to a single plane of movement in their proper position: face parallel to the floor and stone positioned at 11 o’clock or 1 o’clock. The stone should advance forward as strokes are taken, from the heel third of the blade to the toe third. Once you reach the beginning of the curvature, the stone will come out of contact with the blade because it remains parallel to the lateral edge. The lateral portion is now complete.
The next step is preparation of the toe curvature. Note the three segments of the instrument toe in the illustration (Figure 5). The corners, segments X and Z, tend to be used more during instrumentation than the center segment Y and thus, need careful attention. To effectively prepare the toe of the curet, position and stabilize the instrument with the face flat to the floor and the toe directed at 3 o’clock. The stone is positioned at 2 o’clock for its plane of movement. Proceed around the toe in light successive strokes keeping the 2 o’clock plane of movement as the stone sweeps in an arc. Rotate the wrist to move the stone from one side to the other, sweeping around from segments X to Y to Z to Y to X and so on. Keep the pressure light in order to preserve the length of the blade and sharpen only to the point of re-establishing the bevel at the toe. With practice, a rhythm will develop and the process will become more comfortable.
Check the instrument by adapting the upper third of the blade against a plastic test stick and rolling from heel end to toe end. Do not activate a vertical stroke on the plastic as that will only check the minute portion of the blade in contact with the curved test stick. It will also destroy the integrity of the plastic. There should be a consistent bite along the entire length of the blade. Paying close attention to these trouble spots will prevent the most common errors in sharpening and enable a higher standard of nonsurgical care with more favorable therapeutic outcomes.
From Dimensions of Dental Hygiene. June 2005;3(6):32, 34.