0679 The relationship between chair position and forearm motion of operator
T. OZAWA, M. NAKANO, K. SHIOZAWA, and T. ARAI, Tsurumi University, Yokohama, Japan

Objectives: Operator's forearm motions during dental practice have an effect on hands and forearm muscle activities. The purpose of this study was to estimate the relationship between the chair position and the forearm motion of dentists during root canal instrumentation. Methods: The artificial teeth with canal spaces were used on the artificial jaw in a simulator head. The chair positions of the subject to instrument root canals were prescribed to 10 o'clock or 12 o'clock. Six right-handed dentists instrumented the root canals of a left upper central incisor (#21), a left lower first molar (#36) and a right lower first molar (#46) with K-file. The wrist angle and forearm rotation of the subject were measured using a flexible goniometer system. Electromyographic activity (EMG) of the flexor pollicis brevis muscle (f.p.b) was recorded using bipolar surface electrodes during root canal instrumentation. Results: The difference of the wrist angle between 10 o'clock and 12 o'clock chair position for #46 (28.99.4 deg.) was significantly larger than that for #36 (16.19.0 deg.) (One-way factorial ANOVA test & Fisher's PLSD, p<0.05). There were significant differences about the forearm rotation between 10 o'clock and 12 o'clock chair position for #21 (10 o'clock: 56.221.4 deg., 12 o'clock: 6.916.6 deg.) and #46(10 o'clock: 53.130.9 deg., 12 o'clock: 84.624.3 deg.) (Wilcoxon signed-rank test, p<0.05) The maximum amplitude EMGs for #21 and #36 instrumentation at 10 o'clock chair position (#21: 1.80.9 V, #36: 2.60.7 V) were significantly larger than those at 12 o'clock chair position (#21: 0.70.2 V, #36: 1.10.5 V). Conclusions: These results suggest that the chair position during root canal instrumentation has an effect on the forearm motion and the muscle activity of operators, therefore influences the operators' labor.

Seq #85 - Clinical Trials, Tooth Whitening, Health Promotion
10:15 AM-11:30 AM, Thursday, 11 March 2004 Hawaii Convention Center Exhibit Hall 1-2

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