Effects of 5 different finger rest positions on arm muscle activity during scaling by dental hygiene students

This study was conducted to determine the effects of 5 different finger rest positions: opposite arch, standard intraoral, basic extraoral, cross arch, and finger on finger on the muscle activity of 4 forearm muscles (extensor carpi radialis longus, flexor carpi ulnaris, biceps brachii, and pronator teres) during a simulated periodontal scaling experience.

A convenience sample of 32 consenting senior dental hygiene students who met inclusion criteria participated. Using a 4 x 5 counter-balanced research design, each participant used a Gracey 11/12 curet to scale one cc of artificial calculus from first permanent molar typodont teeth (#3,14,19,30). Five different typodonts were set up for each participant with fulcrums randomly assigned for use on each typodont. While scaling, the participant's muscle activity was measured by surface electromyography. Two-way analysis of variance with repeated measures was used to determine if significant differences existed in the amount of muscle activity generated with each fulcrum.

Results revealed no statistically significant interaction effect between area of the mouth scaled, muscle activity, and fulcrum used. Similar muscle activity was produced throughout the mouth regardless of the fulcrum used. The upper right quadrant produced the most muscle activity (p= 0.0101) and the lower left quadrant produced the least (p=< .0001). When comparing the overall muscle activity generated with each fulcrum, only the cross arch fulcrum when compared to the opposite fulcrum produced statistically significant results (p=0.0110).

Based on the results, similar muscle activity is produced when using any of the 5 fulcrums in each quadrant of the mouth. Clinicians appear to experience minimal ergonomic advantage in terms of fulcrums used and area of the mouth scaled during a simulated scaling experience.