Assessment of Structural and Compositional Safety of Dentin Treated with Water-Based Cold Plasma (Magnetic Fields)

Recently, a growing demand for new bleaching techniques that minimize potential damage to dental hard tissues while maintaining bleaching efficacy has been observed in clinical practice. Physically-activated energy- based bleaching methods that assist or replace chemical oxidation reactions are attracting attention. This study evaluated the effects of using sterile distilled water (DW) and cold plasma-based bleaching for vital bleaching (bleaching of vital teeth) on the internal dentin structure. Additionally, the study verified whether the structural stability of dentin hard tissue was maintained after bleaching. Dentin specimens, measuring 1 mm × 2 mm × 1 mm, were prepared and randomly assigned to four groups, untreated control, each receiving either sterile DW or cold plasma alone or in combination for 30 minutes (n = 10/group). Cold plasma treatment was driven by argon (Ar) gas at approximately 3 kVpp and 20 kHz, and irradiated from a distance of 1 cm from the dentin surface. In the plasma-based group, sterile DW was applied, and then reapplied to the specimen surface at 30- second intervals, while plasma was simultaneously irradiated. After all treatments, the specimens were washed with DW and dried. The microhardness was measured using a Vickers hardness tester, and the changes in mineral compositions were determined by comparing the weight ratios of major elements through electron probe microanalysis (EPMA). After 30 minutes of treatment, no significant changes were observed in the dentin surface microhardness and mineral composition in any of the experimental groups (p > 0.05). The study results demonstrated that the single or combined application of sterile DW and/or cold plasma did not affect the dentin hard tissue. These results suggest that bleaching of vital teeth using sterile DW and cold plasma does not induce significant changes in the microhardness and mineral composition of dentin. As such, sterile DW and cold plasma show promise for hard tissue-preserving bleaching applications in esthetic dentistry.