Properties of dentin, enamel and their junction, studied with Brillouin scattering and compared to Raman microscopy

Objective: Dentin, enamel and the transition zone, called the dentin-enamel junction (DEJ), have an organization and properties that play a critical role in tooth resilience and in stopping the propagation of cracks. Understanding their chemical and micro-biomechanical properties is then of foremost importance. The aim of this study is to apply Brillouin microscopy on a complex biological structure, that is, the DEJ, and to compare these results with those obtained with Raman microscopy. Design: Both techniques allow noncontact measurements at the microscopic scale. Brillouin microscopy is based on the interaction between acoustic phonons and laser photons and gives a relation between the frequency shift of the scattered light and the stiffness of the sample. Raman spectra contain peaks related to specific chemical bonds. Results: Comparison of the Brillouin and Raman cartographies reveals correlations between mechanical and chemical properties. Indeed, the shapes of the phosphate content and stiffness curves are similar. The two spectroscopies give compatible values for the mean distance between two tubules, i.e., 4-6 & mu;m. Moreover, for the first time, the daily cross striations of enamel could be studied, indicating a relationship between the variation in the phosphate concentration and the variation in the rigidity within the enamel prisms. Conclusions: We demonstrate here the possibility of using Brillouin scattering microscopy to both study complex biological materials such as the enamel-dentin junction and visualize secondary structures. Correlations between the chemical composition and mechanical properties could help in better understanding the tissue histology.

Automated summary

Studying the chemical and micro-biomechanical properties of dentin, enamel, and the dentin-enamel junction (DEJ) is important for understanding tooth resilience and crack propagation prevention. This study used Brillouin and Raman microscopy techniques to investigate the DEJ and found correlations between mechanical and chemical properties. Additionally, the daily cross striations of enamel were successfully observed for the first time. The application of Brillouin scattering microscopy can provide insights into tissue histology.