Magnification of the Galilean system and work posture in dental students: a crossover study

This study investigated the effects of different magnifications of the Galilean system on the posture of dental students during pre-clinical procedures. Thirty-seven second-year undergraduate dental students participated in this study. Dependent variables included angular deviation from the neutral position of the neck, neck muscle activity, and working distance from the operator's eyes to the mannequin's mouth. The independent variable was the magnification of the Galilean system loupes at four levels (naked eye, 2.5×, 3.0 × , and 3.5× magnification). Students performed Class I teeth preparations on the maxillary first molar using a dental mannequin, and postures were recorded on photographs during the procedure. The “Software for Postural Assessment” (version 0.69) analyzed the angular deviation and working distance. Muscle activity was assessed bilaterally using surface electromyography of the descending trapezius and sternocleidomastoid muscles. Descriptive statistical analysis and one-way repeated-measures analysis of variance (rANOVA) was conducted (α = 0.050). As a result, a greater angular deviation of the neck was observed with the naked eye during tooth preparation (p < 0.001). However, different magnifications did not affect the muscle activity (p = 0.050–0.911) or working distance (p = 0.136). It was possible to conclude that, regardless of the magnification, using Galilean loupes reduced angular deviation; however, it did not influence muscle activity or working distance.