Neck and shoulder muscle activation patterns among dentists during common dental procedures

BACKGROUND: Dental practitioners often suffer musculoskeletal disorders (MSDs) in the upper extremity due to the static, repetitive and precise nature of work. Knowledge regarding muscle activation patterns in that region is essential in understanding the mechanism behind the upper extremity MSDs. However, the literature review has revealed few studies with such a focus. OBJECTIVE: This study aims to examine the inter-relationship of the exertion levels of eleven upper extremity muscles during common dental procedures. This provides insights into the interactive utilization patterns of the targeted muscles and their implications in the development of MSDs. METHODS: Twelve dentists were recruited. Electromyography (EMG) signals of sampled muscles were collected for 32 trials, i.e. combinations of independent variables (IVs) (and levels): posture (2), precision (2), line of vision (4), and grip type (2). Multivariate statistical methods were used to analyze the effects of IVs on muscle coactivity patterns. RESULTS: MANOVA showed significant main effects and a 2-way interaction between precision and grip type. Most notably, the upper trapezius exhibited consistently higher utilization than other muscles during a seated posture. CONCLUSIONS: Seated postures, preferred by dentists as a way to relieve back stress, may contribute to the development of shoulder or neck MSDs due to elevated upper trapezius exertions.