Confocal Raman mapping of collagen cross-link and crystallinity of human dentin-enamel junction

The separation zone between enamel and dentin [dentin-enamel junction (DEJ)] with different properties in biomechanical composition has an important role in preventing crack propagation from enamel to dentin. The understanding of the chemical structure (inorganic and organic components), physical properties, and chemical composition of the human DEJ could benefit biomimetic materials in dentistry. Spatial distribution of calcium phosphate crystallinity and the collagen crosslinks near DEJ were studied using confocal Raman microscopy and calculated by different methods. To obtain collagen crosslinking, the ratio of two peaks 1660  cm-1 over 1690  cm-1 (amide I bands) is calculated. For crystallinity, the inverse full-width at half maximum of phosphate peak at 960  cm-1, and the ratio of two Raman peaks of phosphate at 960/950  cm-1 is provided. In conclusion, the study of chemical and physical properties of DEJ provides many benefits in the biomaterial field to improve the synthesis of dental materials in respect to the natural properties of human teeth. Confocal Raman microscopy as a powerful tool provides the molecular structure to identify the changes along DEJ and can be expanded for other mineralized tissues.