Impacto da radioterapia na composição química e propriedades mecânicas na região cervical da dentina humana

Abstract

The objetive of this study was to evaluate the effect of radiotherapy on the chemical composition and mechanical properties of human dentine focused on the cervical region. For this, healthy third ten molar teeth were used, which were submitted to radiotherapy in vitro according to the following radiotherapy protocol: 2 Gy per day, 5 days per Week for 7 weeks, totaling 70 Gy. The teeth were divided according to the experimental groups (n = 5): Non-irradiated group (NR) and Irradiated group (IR). For each group the dentin of the cervical region was evaluated. It was evaluated the chemical composition by Fourier Transform Infrared Spectroscopy (FTIR) and Raman Spectroscopy using the following parameters: mineral / matrix ratio (M: M), carbonate / mineral ratio (C: M), amide I / amide ratio III and amide ratio I / CH2. And evaluation of the mechanical properties by means of Nanohardness test and Elastic Modulus. T-test was done for statistical analysis in each parameter evaluated comparing group NR and IR. For the M: M, only the Raman detected statistical difference between the groups (p <0.001). As for the C: M, there was a significant difference in the FTIR evaluation (p = 0.004). For the amide I / amide III ratio there was difference for FTIR and Raman (p = 0.007 and p <0.001, respectively). And for amide I / CH2 ratio there was statistical difference only for Raman (p <0.001). For mechanical evaluation T test showed difference between the groups only for nanohardness (p = 0.03). It can be concluded that radiotherapy altered the chemical composition and nanohardness of cervical dentin. Raman and FTIR are presented as complementary methodologies to evaluate changes in chemical composition.