8DSS-promoted remineralization of demineralized dentin in vitro

Dentin phosphoprotein (DPP) plays an extremely important role in the biomineralization of human tooth. The repetitive nucleotide sequence of aspartate-serine-serine (DSS) is the fundamental unit within DPP, and peptides containing 8 repeats of DSS (8DSS) have been shown to possess the ability to induce remineralization of the demineralized enamel. In this work, we coated the 8DSS peptide on the completely demineralized dentin to evaluate the effect of 8DSS peptide coating on dentin remineralization. Human dentin samples were demineralized with 37% phosphoric acid for 2 min, and then the 8DSS peptide (1 mg mL^-1) was coated and the binding strength of the 8DSS peptide to demineralized dentin was examined using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Then the coated dentin samples were immersed in artificial saliva for 3 weeks. After that, the remineralized dentin samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analysis and ATR-FTIR. The mechanical properties of the remineralized surfaces were determined by nano-indentation and atomic force microscopy (AFM). The results showed that the 8DSS peptide had good binding strength to demineralized dentin and could induce nano-crystals precipitation both on the surfaces and within the dentinal tubules. The mechanical properties of the 8DSS-coated samples were significantly improved. In contrast, there were hardly any newly generated minerals deposited on the samples without 8DSS peptide coating. In conclusion, the 8DSS peptide may be a promising biomaterial for restoring the demineralized human dentin.