Effect of an Educational Intervention on Postural Risk Among Endodontic Residents Under Different Magnification Conditions

AIM: To assess the impact of a tailored ergonomic lecture on postural risk among second-year endodontic residents depending on the use of no magnification, ergonomic loupes, or an operating microscope. METHODOLOGY: A within-subjects, repeated measures crossover study was conducted before and after a tailored ergonomic lecture. Ten postgraduate students from the Master's in Endodontics at the European University of Madrid each treated three comparable molar cases under three randomised visual conditions: no magnification, 7.5× ergonomic loupes, and a dental microscope. Baseline and post-lecture procedures were video recorded from three angles, and the most representative still frame was scored using the Rapid Upper Limb Assessment (RULA). A 90-min tailored lecture on clinical ergonomics separated the two recording sessions. Musculoskeletal symptoms data were collected with the Nordic Questionnaire. Aligned-rank-transform ANOVA with Friedman and Conover post hoc tests was used for statistical analysis (α = 0.05). RESULTS: All participants reported musculoskeletal pain during the preceding 12 months, most frequently in the neck (50%) and lower back (50%). At baseline, significant differences were found between magnification conditions (p = 0.00027). Students working without magnification had significantly higher RULA scores than those using loupes (p < 0.001) or a microscope (p < 0.001), with no significant difference between loupes and microscope (p = 0.96). Following the intervention, a marked reduction in RULA scores was observed in the no-magnification group; however, their scores remained significantly higher compared to the microscope group (p < 0.001) and the loupes group (p < 0.001). CONCLUSIONS: A single, task-specific ergonomic session combined with magnification significantly reduced postural load in endodontic residents, although working with no magnification continued to pose moderate to severe risk.