The Effects of Instrument Handle Design on Forearm Muscle Activity During Scaling by Dental Hygienists

Purpose: The purpose of this study was to determine the effects of 4 different commercially available instrument handle designs (A. 16 grams and 12.7 mm diameter; B. 23 grams and 11.1 mm diameter; C. 21 grams and 7.9 mm diameter; D. 18 grams and 6.35 mm diameter) on the muscle activity of four forearm muscles during a simulated scaling experience. Methods: A convenience sample of 27 dental hygienists used a Columbia 13/14 curet with four different instrument handles to scale artificial calculus. While scaling, each participant’s muscle activity was measured using surface electromyography (sEMG). Participants completed an end user opinion survey. Results: Similar muscle activity was generated when scaling with instruments at 16, 18, and 21 grams with varying diameter handles. Instrument B generated significantly more muscle activity when compared to each of the other 3 instrument handle designs (p=0.001, p=0.002, p=0.039). Additionally, the lower left quadrant displayed significantly less muscle activity during scaling than the right quadrants (p=0.026, p=0.000), although no significant interaction effect was found with instruments within quadrants. Most participants (62.96%) preferred instrument A, which was rated more comfortable based on weight when compared to the other instruments tested (z=2.643, p=0.008; z=3.708, p=0.000; z=3.819, p=0.000). The smallest diameter instrument was rated significantly less comfortable (A. z=4.398, p=0.000; B. z=4.023,p=0.000; C. z=3.333, p=0.001). Conclusions: Instrument handle design has a significant effect on forearm muscle activity when performing scaling in a simulated environment. The heaviest instrument produced the highest muscle activity. Similar amounts of muscle activity were produced by instruments weighing between 16 and 21 g. Participants’ instrument preferences were more affected by handle diameter than weight. The need for further research is needed to determine the impact of these results on arm muscle load related to risk of cumulative trauma disorders in a real-world setting