Structural differences in enamel and dentin in human, bovine, porcine, and ovine teeth

Abstract

Background: The aim was to study differences between crystalline nanostructures from the enamel and dentin of human, bovine, porcine, and ovine species.

Methods: Dentine and enamel fragments extracted from sound human, bovine, porcine and ovine incisors and molars were mechanically ground up to a final particle size of <100μm. Samples were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC).

Results: Human enamel (HE) and dentin (HD) showed a-axis and c-axis lengths of the carbonate apatite (CAP) crystal lattice nearer to synthetic hydroxyapatite (SHA), which had the smallest size. Enamel crystal sizes were always higher than those of dentin for all species. HE and HD had the largest crystal, followed by bovine samples. Hydroxyapatites (HAs) in enamel had a higher crystallinity index (CI), CI_Rietveld and CI_FTIR, than the corresponding dentin of the same species. HE and HD had the highest CIs, followed by ovine enamel (OE). The changes in heat capacity that were nearest to values in human teeth during the glass transition (ΔCp) were in porcine specimens. There was a significant direct correlation between the size of the a-axis and the substitution by both type A and B carbonates. The size of the nanocrystals and the crystallinity (CI_Rietveld y CI_FTIR) were significantly and negatively correlated with the proteic phase of all the substrates. There was a strongly positive correlation between the caloric capacity, the CIs and the crystal size and a strongly negative correlation between carbonates type A and B and proteins.

Conclusions: There are differences in the organic and inorganic content of human, bovine, porcine and ovine enamels and dentins which should be taken into account when interpreting the results of studies using animal substrates as substitutes for human material.

Keywords: Crystallographic structure; Dentin; Differential scanning calorimetry (DSC); Enamel; Fourier transform infrared spectroscopy (FTIR); X-ray diffraction (XRD).