Chemical analysis of in vivo-irradiated dentine of head and neck cancer patients by ATR-FTIR and Raman spectroscopy

ObjectivesTo evaluate the effect of in vivo radiotherapy on the chemical properties of human dentine by Fourier-transform infrared spectroscopy (FTIR) and Raman analysis.Materials and methodsChemical composition was evaluated comparing control and irradiated group (n=8). Irradiated teeth were obtained from radiotherapy patients subjected to fractionated X-ray radiation of 1.8Gy daily totaling 72Gy. The teeth were sectioned according to the type of dentine (crown or root dentine), obtaining 3-mm dentine cervical slices. The analyzed parameters by FTIR and Raman spectroscopies were mineral/matrix ratio (M:M), carbonate/mineral ratio (C:M), amide I/amide III ratio, and amide I/CH2 ratio. Raman also calculated the phosphate and carbonate crystallinity.ResultsFTIR revealed that M:M had a decrease in both factors (p=0.008; p=0.043, respectively) and root dentine showed a lower C:M in the irradiated group (p=0.003). Raman revealed a higher phosphate crystallinity and a lower carbonate crystallinity in crown dentine of irradiated group (p=0.021; p=0.039). For amide I/amide III, the irradiated showed a lower ratio when compared to the control group (FTIR p=0.002; Raman p=0.017). For amide I/CH2, the root dentine showed a higher ratio than the crown dentine in both methods (p<0.001).ConclusionsRadiotherapy altered the chemical composition of human dentine. The exchange of phosphate-carbonate ions in the hydroxyapatite and higher concentration of organic components was found after radiotherapy.Clinical relevanceThe increased risk of radiation-related caries in patients undergoing head and neck radiotherapy is due not only to salivary, dietary, and microbiological changes but also to changes in tooth chemical composition.