An atomic force microscopic study of the ultrastructure of dental enamel afflicted with amelogenesis imperfecta

The ultrastructure of human tooth enamel from a patient diagnosed to have amelogenesis imperfecta (AI) was investigated using atomic force microscopy (AFM) and compared with normal human tooth enamel. AI is a hereditary defect of dental enamel in which the enamel is deficient in either quality or quantity. Tissue-specific proteins, especially amelogenins, have been postulated to play a central role in amelogenesis. The secondary structure of amelogenin has been assigned an important role in directing the architecture of hydroxyapatite (HA) enamel crystallites and an alteration of the secondary structure of amelogenin is expected to result in an altered architecture of the mineral phase in human enamel. Previous studies have shown that the human amelogenin gene encodes for a mutant protein in which a conserved Pro is mutated to a Thr residue (Pro → Thr); such a mutation should be expected to cause a disoriented pattern of the mineral phase in enamel. AFM results presented for the AI tooth enamel clearly demonstrate that the apatite crystal morphology in AI tooth enamel is perturbed in the diseased state; this might result from a defective synthesis of the extracellular matrix proteins, e.g. amelogenin, by the ameloblasts.