Efeito da radiação in vivo sobre a composição química da dentina humana

Abstract

Knowledge about the chemical composition of dentine is important to better understand the effects of radiotherapy on dental hard tissues. The aim of this study was to evaluate the effect of in vivo radiotherapy on the chemical properties of human dentine. For this, two groups were used (n=8), one control and one irradiated. Lower incisors and canines from non-irradiated patients were used as control group. On the other hand, the teeth of the irradiated group were obtained from head and neck radiotherapy patients subjected to fractionated X-ray radiation of 1.8 Gy daily until a total of 72 Gy. In both groups, the patients had advanced periodontal disease, indicating the teeth extraction. Teeth were sectioned according to the type of dentine (crown or root dentine), obtaining slices perpendicular to the longitudinal axis of the tooth, from the cervical region with 3 mm of thickness. Then, these slices were cut in the mesiodistal direction, obtaining two halves. Lingual halves were used to evaluate the chemical composition of dentine by FTIR and Raman spectroscopies. The analyzed parameters 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. Chemical parameters were influenced by radiation and type of dentine. FTIR revealed that M:M ratio showed a significant difference for both factors (radiation p=0.008; type of dentine p=0.043), and the root dentine presented a lower C:M ratio in the irradiated group (p=0.003). Raman showed significant difference in M:M and C:M ratios only for type of dentine (p=0.029 and p=0.031, respectively) and also revealed an increase in phosphate crystallinity and a decrease in carbonate crystallinity in crown dentine for irradiated group (p=0.021 and p=0.039, respectively). For organic portion, the control group had a greater amide I/amide III ratio than the irradiated in both methodologies (FTIR p=0.002, Raman p=0.017). For amide I/CH2 ratio, the root dentine showed a greater ratio than the crown dentine in both methods (p<0.001). Within the limitations of this study, radiotherapy altered the chemical composition of human dentine, as there was an exchange of phosphate-carbonate ions in the hydroxyapatite and an increase in the concentration of the organic components. In addition, crown dentine showed to be more mineralized than the root dentine, which contains a greater organic portion.