Dental magnetic attachments, usually applied locally to oral cavities, produce stray fields (flux leakage) spreading in adjacent tissues. It has been found that human periodontal ligament (PDL) cells change their geometry and the structure of their cytoskeleton F-actins when the cell cultures are exposed to B-field strengths of B = 10mT and 120mT, respectively, which are similar to those generated by dental magnetic attachments. Analytically, after long-time exposures to B-fields for 12h, 36 h and 60 h, respectively, cytoskeleton F-actins are labeled with a fluorescent dye and observed under a laser scanning confocal microscope. The geometrical cell parameters of cell length and cell width and the fluorescence emission of labeled F-actins, respectively, were determined and subjected to an automatic image analysis using a special software. The results on cell shrinkage and filament reorganizations were statistically analyzed by the program ANOVA (P < 0.05). It was found that only long-time (hours) exposure to high fields in the order of 0.1T may produce tissue irritations during long-time medical treatments using open- and closed-field dental magnetic attachments.