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Instrument Design for Optimal Hand Health

Lightweight, large diameter, and tapered shape are key to improving the ergonomics of hand instrumentation.

The practice of dental hygiene is well known for its occupational hazards leading to high prevalence rates of musculoskeletal disorders (MSDs). Research has revealed 60% to 90% of dental hygienists experience MSDs (depending on the study design).1-12 Scaling and root planing requires repetitive, fine motor movements that cause cumulative trauma, affecting the fingers, wrists, and hands. This trauma results in repetitive strain injuries, overuse injuries, and MSDs of the fingers, wrists, and hands.

Related hand injuries may include carpal tunnel syndrome, tendinitis, De Quervain tenosynovitis, and stenosing tenosynovitis (commonly referred to as “trigger finger”).1-3,6-9,11 Pain caused by these MSDs results in lost hours at work, increased sick leave, decreased productivity, and other negative impacts that affect the clinician and practice.13-21

Research has long sought to determine mitigation strategies to prevent MSDs among dental hygienists. Though research has indicated power instrumentation as one ergonomic improvement for preventing MSDs, manual instrumentation is still necessary for patient care. Some research has indicated increased risks with ultrasonic use due to the trauma caused by vibration.22-25

One of the most promising areas of manual instrumentation research to mitigate musculoskeletal trauma involves instrument handle design and its impact on the fingers, hands, wrists, and muscles in the forearm that controls movements of the hands and fingers.7,26-29,31,32

Instrument Handle Designs

Dong et al26,27,31,32 performed several studies on instruments to determine the impact of instrument handle designs on muscle activity production and pinch force generation. This team’s findings laid the foundation for ergonomic principles when designing instruments for scaling and root debridement. In this research, results revealed lightweight instruments and large-diameter instruments produced less muscle activity and pinch force, therefore reducing the risk for MSDs.

Another study by Dong et al26 determined that the shape of the instrument handle may also impact MSD risk. For this study, results revealed that a tapered shape reduced muscle activity and pinch force, therefore reducing MSD risk. However, there were limitations to these studies that impact the generalization of the data. First, instruments were researcher-designed and not commercially available. Though this was necessary to examine weight and diameter independently, it did limit the generalizability of the findings. Second, the instruments used to measure muscle activity and pinch force may have impeded other aspects of the instrument handles in these studies. Finally, pinch force was only measured in the thumb, but likely is impactful to the index finger when grasping instruments for manual instrumentation. Despite these limitations, research has continued to support lightweight and large-diameter instruments for reduction in muscle activity and pinch force in commercially available instruments.7,29

Recent developments in instrument design have incorporated some of these ergonomic characteristics into handle designs. Almost all instrument companies offer ergonomic choices, including handles that are both lightweight and large diameter. Additionally, tapered instrument handle shapes are often utilized.

When looking to order instruments for scaling and root debridement, dental hygienists should consider the weight, diameter, and shape of the handle, as well as how these factors may impact their hand health and MSD risk. Also, a resin handle offers a lightweight option, though many other materials can also be lightweight. Previous research found that instrument handles should ideally have a mass of 15 grams or less and a diameter of 10 millimeters or greater.7,26-29,31,32

Scaling Technique Considerations

The use of titanium nitride-infused stainless steel in the manufacturing of instruments, otherwise known as sharpen-free instruments, is another ergonomic development. This is considered a stronger and sharper material, allowing for a modified scaling technique, using less lateral force without the negative consequence of leaving burnished calculus. The shaving stroke associated with sharpen-free instrument designs is contraindicated in traditional stainless steel instruments because it may cause burnished calculus that is difficult to remove.30,33

My colleagues and I explored differences in the traditional scaling technique vs a modified scaling technique on muscle activity and pinch force generation.30 Results revealed no statistically significant differences in muscle activity production; however, less muscle activity was produced with the modified scaling technique compared to the traditional scaling technique. Additionally, results indicated a statistically significant difference in pinch-force generation of the thumb (p=0.02) and index finger (p=0.03) between the two techniques, with the modified scaling technique producing less pinch force for both the thumb and index finger.

Other Considerations for Manual Instrumentation

Though not yet extensively researched in dentistry, other aspects of manual instrumentation should be considered for ergonomic impacts and potential MSD risk reduction. The efficacy of the instrument in use is of utmost importance. For example, if an instrument reduces muscle activity and/​or pinch force, but requires more strokes to remove the deposit completely, this may increase the risk for MSDs due to the increased repetition of the scaling stroke.

Time is important for dental hygiene appointments and some instruments may require longer use in addition to higher volume of strokes for calculus removal, thus increasing the duration of muscle activation and grasping of the instrument.

Future research should consider these issues and determine the ergonomic impact for clinical use. It is possible that a combination of designs utilized throughout the day may prove impactful for reducing MSD risk, though this is not yet researched. It is possible that alternating diameters, weights, and other characteristics of instrument designs throughout the appointment or workday may alter the activation of muscles and reduce the repetitiveness of scaling and root debridement tasks throughout the day.

Using both power instruments and manual instruments throughout a patient appointment may also benefit in activating muscles differently throughout scaling and root planing.

Conclusion

Research on manual instruments continues to explore the ergonomic impacts of various characteristics of instrument designs. Currently, research indicates dental hygienists should use instruments that are lightweight, have larger diameters, and are tapered in shape. Additionally, the results from at least one pilot study examining the use of a modified scaling technique may reduce MSD risk with sharpen-free instruments; additional research is needed. Further research should be conducted on the additive effects of using multiple instrument designs, ideally to determine if altering designs throughout the day may reduce MSD risk by activating different muscle groups.


References

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From Dimensions of Dental Hygiene. March 2024; 22(2):18-21

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