Effects of endodontic instrument handle diameter on electromyographic activity of forearm and hand muscles.
OBJECTIVE
To determine the influence of the handle diameter of endodontic instruments on forearm and hand muscle activity using electromyographic (EMG) recording.


METHODS
Size 45 K-type files were fitted with four different handle diameters; 3.5, 4.0, 5.0, and 6.0 mm. Seven dentists then attempted to negotiate to the working length acrylic resin root canals with each of the four handle sizes using a reaming motion. EMG activities were recorded from the flexor pollicis brevis muscle (f.p.b.), the flexor carpi radialis muscle (f.c.r.), and the brachioradialis muscle (b) with bipolar surface electrodes. The time taken to negotiate the canals, the area of integrated EMG that corresponded to the amount of EMG activity required during penetration and the maximum amplitude of EMG were measured using the EMG data. Results were analysed statistically using a one-way factorial ANOVA test and multiple comparison tests.


RESULTS
Reaming time and integrated EMG area of each muscle decreased with an increase in handle diameter. The most significant difference in time and area of integrated EMG was detected between handles of 6 mm and 3.5 mm diameter (time: P < 0.01, area of the f.p.b.: P < 0.01, area of the f.c.r. and b: P < 0.05), and between handles of 5 mm and 3.5 mm diameter (P < 0.05). Both 5 mm and 6 mm handles significantly decreased the maximum amplitude of EMG recorded from the f.p.b. compared with 3.5 mm handles (between 3.5 mm and 6 mm: P < 0.01, between 3.5 mm and 5 mm: P < 0.05).


CONCLUSIONS
The results indicate that handle diameter has an effect on reaming time as well as on muscle activity. As a consequence, handle diameter influenced operator performance during instrumentation.
Ozawa
T
T
Department of Periodontics and Endodontics, Tsurumi University School of Dental Medicine, 2-1-3, Tsurumi, Tsurumi-ku, Yokohama 230-8501, Japan.
Nakano
M
M
Sugimura
H
H
Kurayama
H
H
Tahata
K
K
Nakamura
J
J
Shiozawa
K
K
D000180:Acrylic Resins; D000328:Adult; D000704:Analysis of Variance; D003786:Dental Pulp Cavity / Q000033:anatomy & histology; D004526:Efficiency; D004576:Electromyography; D004867:Equipment Design; D005542:Forearm / Q000502:physiology*; D006225:Hand / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D018482:Muscle, Skeletal / Q000502:physiology*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D013223:Statistics as Topic; D013499:Surface Properties; D013997:Time Factors
D000180:Acrylic Resins