The Role of Chair Design in Dental Ergonomics: A Kinematic Assessment of Movement and Ergonomic Risk

Dental professionals are susceptible to musculoskeletal disorders due to unphysiological postures during treatment, which can be mitigated by the choice of a work chair to improve ergonomic working posture.

In this study, the influence of five different work chairs on the ergonomic risk assessment using RULA and the working behaviour of 22 right-handed dentists was investigated. To this end, dental treatment was simulated on a phantom head, with the body posture recorded using an inertial motion capture system. The resulting kinematic data were converted into a continuous RULA scheme, and statistical methods (Friedman test with Conover-Iman comparisons and statistical parametric mapping) were used to compare the chairs. The significance level was set at p ≤ 0.05.

The RULA analysis revealed no significant differences between the task chairs that were tested; however, it should be noted that all of the task chairs exhibited an increased ergonomic risk (RULA ≥ 5), which indicates an increased risk of musculoskeletal disorders. Significant multiple comparisons (SPM analysis) between the selected chairs of the relative occurrence of total joint angles were between Chair 1 vs. 5 (p ≤ 0.03 for shoulder left flexion-extension), Chair 2 vs. 4 (p ≤ 0.03 for shoulder right flexion-extension), Chair 1 vs. 3 (p ≤ 0.03 for trunk right flexion-extension, 0.04 for trunk lateral flexion and 0.05 for elbow left flexion-extension), Chair 3 vs. 4 (p ≤ 0.05 for shoulder left flexion-extension and 0.01 shoulder right flexion-extension), and between Chair 2 vs. 3 (p ≤ 0.05 for elbow left flexion-extension).

The study's findings indicate that the selection of work chairs did not have a significant impact on the ergonomic risk, which remained consistently high across all the chairs. Nevertheless, the analysis of joint angles demonstrated that the Ghopec chair was more frequently associated with greater joint angles, with only a few significant deviations. However, it should be noted that these significant differences in joint angles occurred only sporadically, did not demonstrate a clear and consistent trend across all the chairs, and have no clinical impact. Overall, the results confirm that the working posture of the dentists has a potential risk of developing musculoskeletal disorders, while the ergonomic design of the work chairs plays a rather subordinate role.