Abnormal mineralization of both enamel and dentin may occur by exposure excessive fluoride during the stage of tooth germ formation. Some of the mechanisms about enamel fluorosis have been clarified. The knowledge about dentin fluorosis is limited and the mechanism is unclear. When teeth emerge in cavity, enamel developed completely. However, odontoblast continue to form secondary dentin and reactive, reparative dentin as a response to external irritation by caries, so excessive fluoride could affect dentin...