A mild hydrothermal process is used as a direct method to produce synthetic human enamel prism‐like structures that are biocompatible with dental pulp stem cells. The rod‐like fluorapatite crystals are very similar in chemical composition and in structural dimensions to natural tooth enamel (see figure).

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In natural tooth enamel fluoride is always present in the carbonated hydroxyapatite mineral and plays a key role in the prevention of tooth decay. In this study we aimed at mimicking this natural anticaries ability of the tooth by developing new, effective anticaries materials using fluorapatite nanorods or nanowires. We therefore investigated the conditions necessary to synthesize fluorapatite nanorods of different size, shape and composition for future use either directly or indirectly, that is by incorporation into dental materials, in the treatment and prevention of caries. By controlling the chemical conditions, nanorods of desirable chemical composition and dimension were produced. The mechanism of how these structures were formed is also proposed.

Dentin sialoprotein (DSP) and dentin phosphoprotein (DPP; phosphophoryn) are two principal dentin-specific non-collagenous proteins. DPP is extremely acidic and is rich in aspartic acid and serine. By virtue of this structure, DPP may bind large amounts of calcium and may facilitate initial mineralization of dentin matrix collagen as well as regulate the size and shape of the crystals. The function of DSP is not known. DSP and DPP are encoded by a single gene in both rat and mouse, and are uniquely expressed in odontoblasts and transiently in pre-ameloblasts. Because DSP and DPP are isolated from dentin as distinct proteins and appear to be present in different amounts, the nascent dentin sialophosphoprotein (DSPP) is likely cleaved to yield DSP and DPP. However, when, where and how the DSPP is cleaved into DSP and DPP is not clear. To further elucidate the structure and function of human DSP and DPP, we have cloned DPP and DSP cDNA by reverse transcriptase-polymerase chain reaction (RT-PCR) strategies, and then cloned and initiated characterization of a human dentin sialophosphoprotein gene. The genomic organization of human DSPP is very similar to that of mouse, containing five exons and four introns, suggesting it is a homologue of mouse dentin sialophosphoprotein (DSPP). Exons 1-4 encode for DSP, while exon 5 encodes for the C-terminus of DSP and the whole DPP. A 4.6-kb RNA transcript was detected on Northern blot analyses of total RNA extracted from immature (open root apices) human teeth using either a human DPP or DSP probe.