Tooth enamel evaluation after tooth bleaching with hydrogen peroxide assisted by a DC nonthermal atmospheric-pressure plasma jet

The purpose of this study is to evaluate the changes in dental enamel (morphology, elemental composition, microhardness, and roughness) after applying hydrogen peroxide in conjunction with a nonthermal plasma to bleach the teeth. Extracted human teeth were randomly placed in six groups. Two control groups (one group with no bleaching agent and no plasma treatment of the teeth and another one with only hydrogen peroxide as the bleaching agent) and four plasma groups (receiving hydrogen peroxide of varying concentrations 6% , 15%, 25%, and 35%, in conjunction with a plasma treatment) were prepared. The surface morphology before and after treatment was assessed using a scanning electron microscope (SEM), and the change in the elemental composition was analyzed by an energy-dispersive X-ray spectroscopy system. A total of 36 extracted teeth were used to evaluate the change in enamel microhardness and surface roughness. The use of hydrogen peroxide as a bleaching agent, even in the absence of plasma exposure, causes various etching patterns that are attributable to demineralization during the treatment process. These patterns are more pronounced as the hydrogen peroxide concentration increases. The surface roughness tests confirmed the findings from the SEM analysis. We only found minor essentially insignificant changes in the elemental composition of the enamel and in the surface microhardness as a result of the treatment using hydrogen peroxide and a cold plasma. The use of a cold plasma in conjunction with hydrogen peroxide of varying concentrations in tooth bleaching causes minor changes in the tooth enamel changes that are comparable to those resulting from the standard treatment using 35 % hydrogen peroxide gel without a plasma.