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The aim of this paper was to assess the effectiveness, safety, stability, and mechanism of tooth whitening using a direct current cold atmospheric pressure air plasma microjet (PMJ) with the assistance of whitening gels (blank or containing 3% H2O2). The results were compared with those obtained from teeth treated with blank gel only and with gel containing 35% H2O2 in a cold light bleaching system. Tooth whitening effectiveness right after various treatments as well as 18 months after treatment was evaluated via CIELAB colorimetry. Type K thermocouple, scanning electron microscope and energy dispersive spectroscopy were employed to study the temperature of pulp chamber, tooth surface morphology, and elemental composition of enamel surface, respectively. Teeth in the plasma groups were effectively whitened in 5 min, though no significant difference was observed between the two plasma groups. Pulp chamber temperature was shown to remain below 35 °C. Morphological and surface elemental analysis showed similar changes to tooth enamel in the plasma groups and in the cold light group. These observations suggested that PMJ with blank gel was more effective for tooth whitening with acceptable safety and good stability. Optical emission spectroscopy results revealed that reactive oxygen species, such as O, •OH, and NO, in plasma may play a dominant role in the process of plasma tooth whitening. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]