An investigation on the Amide i band in vibrational spectra of gingival crevicular fluid during orthodontic treatments

Gingival crevicular fluid (GCF) is an exudate originating in the epithelium lining of the gingival sulcus. GCF analysis can represent a simple and noninvasive tool for monitoring periodontal and bone remodeling during the orthodontic tooth movement (OTM). Gingival crevicular fluid (GCF) samples were investigated by using Fourier transform infrared (FTIR), Raman, and Surface-Enhanced Raman (SERS) micro-spectroscopies. Samples were collected at different stages of orthodontic treatments. Vibrational spectra were acquired on the collected samples for characterizing the biochemical changes that are present during the OTM. The attention was focused on the amide I band region (1500 to 1800 cm-1) of the spectra acquired by using FTIR, Raman, and SERS spectroscopy. Deconvolution procedures were adopted for analyzing this spectral region by means of Gaussian-Lorentzian functions for infrared spectra and Lorentzian ones for Raman spectra. This analysis evidences the different contributions of subcomponents of the amide I band and their changes. These alterations can be attributed to changes in the secondary structure of GCF proteins or to the formation of amyloid aggregates induced by the mechanical stress associated to orthodontic treatments. The results of the present investigation confirm that vibrational spectroscopies can be usefully employed for monitoring orthodontic treatments.