Objectives. Although fluoride is important for the healthy development of enamel tissue, its excess may produce dental fluorosis through still unknown mechanisms. Biochemical evidence suggests the participation of the underlying dentin to enamel fluorosis: in this paper, we examine the micromorphology of fluorotic dental tissues by Scanning Electronic Microscopy (SEM). The aim of the work is the identification of dentinal alterations corresponding to fluorotic plaques. Materials and Methods. Six teeth affected by fluorosis (scored “severe” according to 1942 the Dean’s classification) are fractures and their microstructures observed by Scanning Electronic Microscopy (SEM). Results. The microscopic images of enamel corresponding to fluorotic plates show important underlying dentinal modifications, consisting of marked tubular obliteration. On the contrary, the dentin lying beneath the “apparently normal” enamel does not show micromorphological alterations. Conclusions. Our data agree with recently reported findings on dentinal alterations in severe fluorosis and show that the tubular obliteration occurs only in the dentin underneath clinically altered enamel. The mechanism responsible for the dentinal sclerosis and the characters of this micromorphological fluorotic sclerosis need, however, for further investigation because the prevailing literature (although more dated) is inclined to the presence of dentinal hipomineralization (and not of ipermineralization) in cases of fluorosis.