Perceived contra observed physical work load in Swedish dentists.

In an earlier questionnaire study, dentists reported high experienced physical work load in their profession, but low to moderate complaints from their musculoskeletal system. The correlation between reported physical work load and pain from the musculoskeletal system was weak. This discrepancy could not be satisfactorily explained. Therefore, a second study was undertaken, in which the same 27 dentists who reported musculoskeletal problems were video recorded during one hour of clinical work, and the records were later analyzed using PEO (Portable Ergonomic Observation). PEO is a frequency analysis method which allows observation of work in real time using a portable computer or video recordings. PEO can be adjusted for registration of single or multiple work operations. Output data are presented as frequency, duration, and sequence of the various work operations. The aim of the present study was to investigate if there was a relation between observed work load recorded with PEO, and subjectively estimated work load and musculoskeletal complaints recorded with a questionnaire based on Visual Analogue Scales. Sitting and standing postures, and head, trunk and arm movements were analyzed. The PEO observations showed that dentists generally perform their clinical work in a sitting position, with the head bent forward almost half of the time. Only weak to moderate correlations (r =0.0-0.6) were found between observed physical work load and subjective estimations of experienced physical work load and musculoskeletal complaints. These findings support the results in our previous study, but they do not explain the large difference between the observed low work load and the subjectively experienced high work load. The study will be followed up by EMG measurements and free interviews, where both muscular load and psychosocial factors will be evaluated.

Evaluation of muscular activity, local muscular fatigue, and muscular rest patterns among dentists.

In a previous study, dentists reported very high scores for perceived physical workload, but only low to moderate scores for the musculoskeletal system. This is difficult to explain when other occupational groups in the dental services are compared, and is the main reason why the present study was performed. To measure muscular activity, a surface electromyography (sEMG) study was done, and included the subjects who reported neck and shoulder complaints in the previous study. A portable sEMG system (MyoGuard) was used to collect a myoelectric signal on-line and analysis of the myoelectric signal in a computer. sEMG was recorded from both trapezius muscles for approximately 4 h during an ordinary working day. Twenty-seven dentists participated in the study. The results show accumulated rest% fairly close to that of female cashiers and supermarket employees and increased average rectified value percent (ARV%) during work that could contribute to the very high workload perceived by dentists.