Influence of de-remineralization process on chemical, microstructural, and mechanical properties of human and bovine dentin.

Abstract

This study compared the chemical composition, microstructural, and mechanical properties of human and bovine dentin subjected to a demineralization/remineralization process. Human and bovine incisors were sectioned to obtain 120 coronal dentin beams (6 × 1 × 1mm3) that were randomly allocated into 4 subgroups (n = 15) according to the time of treatment (sound, pH-cycling for 3, 7, and 14days). Three-point bending mechanical test, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), thermogravimetric (TG), and X-ray diffraction (XRD) techniques were employed to characterize the dentin samples. Regarding chemical composition at the molecular level, bovine sound dentin showed significantly lower values in organic and inorganic content (collagen cross-linking, CO3/amide I, and CO3/PO4; p = 0.002, p = 0.026, and p = 0.002, respectively) compared to humans. Employing XRD analyses, a higher mineral crystallinity in human dentin than in bovines at 7 and 14days (p = 0.003 and p = 0.009, respectively) was observed. At the end of the pH-cycling, CI (ATR-FTIR) and CO3/PO4 ratios (ATR-FTIR) increased, while CO3/amide I (ATR-FTIR), PO4/amide I (ATR-FTIR), and %mineral (TG) ratios decreased. The extension by compression values increased over exposure time with significant differences between dentin types (p < 0.001, in all cases), reaching higher values in bovine dentin. However, flexural strength (MPa) did not show differences between groups. We also observed the correlation between compositional variables (i.e., PO4/amide I, CI, and %mineral) and the extension by compression. Human and bovine dentin are different in terms of microstructure, chemical composition, mechanical strength, and in their response to the demineralization/remineralization process by pH-cycling. These dissimilarities may constitute a potential limitation when replacing human teeth with bovines in in vitro studies.