Thermal degradation of dentin collagen evaluated with ESR, infrared and optical spectroscopy

Abstract

Heating dentin to temperatures <300°C produces tissue browning and electron spin resonance (ESR) radicals. This study reveals the origin of these effects and relates them to conformational changes in collagen molecules and water content in the tissue. Bovine dentin was analyzed by (i) Fourier transform infrared spectroscopy to determine collagen conformation and water content, (ii) ESR spectroscopy operating at the X band to determine the paramagnetic species and (iii) an optical spectrometer in transmission mode to determine changes in the visible spectral absorbance. After heating the tissue to temperatures between 100 and 300°C, some water is eliminated and the hydrogen bonds, which determine collagen alpha-helix structure stabilization, are lost. After elimination, the collagen matrix is changed and electrons are probably trapped, giving rise to ESR signals and absorption bands in the ultraviolet-visible spectral range.