Symptoms of the neck and upper extremities in dentists. Scand J Work En viron Health 1990;16:129-34. Symptoms of the neck, shoulders. arms, and hands of 99 dentists and a reference group of 100pharmacists were studied by means of a telephone interview. Forty-four percent of the dentists and 26 % of the pharmacists reported symptoms of the neck [relative risk (RR) 2.1, 95 070 confidence interval (95 % CI) 1.4-3.1]. Symptomsof the shoulder were reported by 51 % of the dentists and 23 % of the pharmacists (RR 2.2. 95 % CI 1.5-3.3). Musculoskeletal symptoms in the forearm were present almost exclusively in the dentists (1 2 versus I %) . Numbness and paresthesia were more common among the dentists than among the referents (RR 4.2, 95 % CI 2.3-7.7). Unilateral Raynaud's phenomenon in the dominant hand occurred in six dentists and one pharmacist. The high frequency of symptoms from the neck, shoulders, and upper extremities of the dentists was probably related to their difficult work positions with cervical flexion and rotation, abducted arms, and repetitive precision-demanding handgrips.
Musculoskeletal disorders in the neck, shoulder, and arm are common in some occupational groups, and have been ascribed to high precision demands and sustained static load in the neck-shoulder region. In order to evaluate the influence of precision and force demands in manual work related to arm support, instrument grip size, the muscular activity in neck, shoulder, and arm muscles was recorded by electromyography. This EMG and perceived exertion were estimated during a simulated work situation where 12 subjects followed a rotating track, using a handheld dental instrument. Normalized mean EMG amplitude levels (% reference maximal contraction) were calculated. The analysis of variance of the results showed that (a) the precision factor affected significantly the muscular load of the two dominant muscles with postural stabilization function (extensor carpi radialis and infraspinatus); (b) the force factor itself had no specific influence on the muscular load of the investigated muscles; (c) arm support, but not hand support, was of significant importance for the load of three dominant shoulder muscles (trapezius, supraspinatus, and anterior deltoid); and (d) the two different hand grip diameters did not change the activity of any muscle investigated.
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