trapezius muscle activity in using ordinary and ergonomically designed dentistry chairs

background: most dentists complain of musculoskeletal disorders which can be caused by prolonged static posture, lack of suitable rest and other physical and psychological problems. objective: we evaluated a chair with a new ergonomic design which incorporated forward leaning chest and arm supports. methods: the chair was evaluated in the laboratory during task simulation and emg analysis on 12 students and subjectively assessed by 30 professional dentists using an 18-item questionnaire. emg activity of right and left trapezius muscles for 12 male students with no musculoskeletal disorders was measured while simulating common tasks like working on the teeth of the lower jaw. results: normalized emg data showed significant reduction (p<0.05) in all emg recordings of the trapezius muscle. dentists also unanimously preferred the ergonomically designed chair. conclusion: such ergonomically designed chairs should be introduced as early as possible in student training before bad postural habits are acquired.