Physiological Root Resorption of Deciduous Teeth: An ATR-FTIR Approach

Background: The study exploited, for the first time, Attenuated Total Reflectance-Fourier Transform-InfraRed (ATR-FTIR) spectroscopy on human dental pulps at different timings of root resorption (RR) to deepen the biological mechanisms occurring in deciduous teeth (De) during their replacement with permanent ones. Methods: N:36 dental pulps from sound De were divided into the following: G0 (no RR); G1 (RR less than 1/3 of root length); G2 (RR not exceeding 2/3 of root length); and G3 (RR more than 2/3 of root length). Samples were analyzed by ATR-FTIR, and the spectral data were submitted to univariate (One-way ANOVA and Tukey's multiple comparison tests; statistical significance set at p < 0.05) and multivariate (Principal Component Analysis, PCA) analyses. Results: PCA displayed good discrimination among groups, ascribable to: (i) the intensity of the peaks of nucleic acids (~1715 cm^-1, ~1237 cm^-1, ~964 cm^-1, and ~815 cm^-1) and carbohydrates (~1159 cm^-1) which increased from G0 to G3 (p < 0.05); (ii) the relative amount of lipids which decreased from G0 to G3 (p < 0.05); and (iii) the intensity of the peaks at ~1014 cm^-1, and ~875 cm^-1 (phosphates and carbonates in hydroxyapatite), which decreased from G0 to G3 (p < 0.05). Conclusions: This study confirmed ATR-FTIR as a reliable and quick technique for the characterization of the dental pulp and highlighted a correlation between specific molecular changes in the dental pulp of deciduous teeth and different RR stages, shedding new light on this process and paving the way for future research, which could improve the clinical management of the primary dentition.