Objective The aim of this study was to compare the change of surface morphology, calcium phosphate weight ratio and microhardness on the enamel surface of removed teeth which were bleached by two kinds of cold light bleaching agents. Methods All removed teeth were divided into 2 groups according to two kinds of beyond cold light bleaching method: Homely agent and clinical agent. Using SEM to detect the change of surface morphology and calcium phosphate weight ratio, using microsclerometer to test the change of microhardness for four times: Shortly after bleaching, 1 week after bleaching, 2 week after bleaching, 3 week after bleaching. Results After bleaching, demineralizing appeared in both two groups. The enamel shortly after bleaching showed the lowest microhardness and calcium phosphate weight ratio than other period times, even obviously demineralized（P＜0.05）. However, the change of parameters would recover after 1 week and reach normal after 2 weeks. Conclusion Both the two cold light bleaching methods: Homely agent and clinical agent, will lead removed teeth to demineralizing, but mineralized soon after. All bleaching samples′ parameter will reach normal level at last and homely agent has lower demineralization than clinical agent.
