The appearance of matrix vesicles and mineralization during tooth development in three teleost fishes with well-developed enameloid and orthodentine.

Ultra-thin resin sections of tooth bearing parts from three species were examined by electron microscopy. During enameloid matrix formation, matrix vesicles (MV) and fine aggregations of crystal-like structures probably derived from the MV were found in the enameloid matrix. In enameloid, however, no additional mineralization occurred along the collagen fibrils until mineralization had begun initially at the junction between the enameloid and orthodentine areas. Advance of mineralization along collagen fibrils was inhibited in the enameloid area before initial mineralization despite the presence of MV. Many MV were observed at the initial mineralization site; they appeared in the predentine during odontogenesis after the initial mineralization and were still visible during the stage of basal dentine formation. The odontoblasts continued to produce MV from the early stage of enameloid matrix formation until the late stage of basal dentine formation. However, despite their long appearance, MV are probably involved directly with the mineralization only when the initial mineralization starts.