Assessment of the spectral changes in root dentin after irrigation with chlorhexidine: A Raman spectroscopy study

Abstract

Introduction: Chlorhexidine (CHX) is a cationic biguanide that binds to negatively charged dentin molecules being slowly released (substantivity), thereby providing a long-lasting antimicrobial action. The aim of this study was to evaluate the spectral changes in the root dentin due to the presence of CHX used as irrigant by means of Raman spectroscopy. Methodology: Twenty human canine teeth were selected and divided into 4 groups according to the irrigation solution used. After biomechanical preparation, the roots were longitudinally sectioned for scanning by a Raman spectrometer (λ785 nm, 300 mW, 4 cm^-1 resolution). Raman spectra were collected at six points along the root canal, immediately (0 h], 24-h, 48-h, 72-h and 7 days after preparation. Results: The statistical analysis (ANOVA GLM) was applied to the scores of the principal components analysis (PCA). Group CHX showed a strong change in the position of the phosphate hydroxyapatite band at ~963 cm^-1, with a shift to higher wavenumbers for the time t = 0; as time passes this band shifted back to ~963 cm^-1. The higher wavenumber shift in this ~963 cm^-1 peak can be attributed to the presence of remnant CHX up to 7 days after root irrigation. For the Group CHX + Water, the shift to higher wavenumber was slightly pronounced and maintained up to t=72-h. Conclusion: Raman spectroscopy could detect the spectral changes caused by the CHX in the root dentin, thus representing an additional tool for identifying adsorption of this compound after root canal preparation.