In this in vitro study, electron spin resonance (ESR) and nuclear magnetic resonance (NMR) were used to evaluate free radical generation and chemical structural changes of amino acids in the Carisolv system. In the ESR study, hydroxyl radical (•OH), carbon radical (•C) and 5,5-dimethyl-1-pyrrolidone-(2)-oxyl-(1) (DMPO-X) were detected in the Carisolv system. •OH was detected in a 0.25 % NaClO and 0.25% glutamic acid reaction mixture, •OH and •C were detected in a 0.25% lysine and 0.25% NaClO reaction mixture, and a DMPO-X like signal was detected in a 0.25% leucine and 0.25% NaClO mixture. More •OH was detected when the Carisolv system was irradiated with plasma light than normal room light. The NMR study revealed that all the amino acids were completely degraded to smaller molecules by NaClO. These results indicate that the free radicals generated by the Carisolv system via NaClO attacked the amino acids. Then the generated •OH in particular attacked the collagen in carious dentin and brought about degradation of the dentin structure. In addition, this mechanism was enhanced by plasma-light irradiation.