Análise química da dentina radicular irradiada e sua interação com os cimentos resinosos

Abstract

The aim of this study was to investigate the chemical changes of root dentin submitted to in vitro irradiation and how it affects the interaction with resin cements. For this, 40 human premolars were collected and randomly assigned into two groups (n=20): non-irradiated and irradiated. Subsequently, they were divided into two subgroups according to the type of resin cement (n=10): total-etch RelyX ARC and self-adhesive RelyX U200. After endodontic treatment and cementation of fiberglass post, the roots were sectioned. Fourier-transform infrared spectroscopy (FTIR) was used to verify chemical composition changes in root dentin according to thirds (n=08). Three samples per group were taken to Raman spectroscopy to estimate the diffusion zone of the cements and their chemical interaction with dentin. For bonding interface analysis, two other samples per group were prepared with colorants and analyzed under confocal laser scanning microscopy(CLSM). FTIR data were analyzed using One-way ANOVA with repeated measurement (thirds) and Tukey’s test. Raman data were analyzed using Two-way ANOVA and Tukey’s test (α=0.05). For confocal images, a descriptive analysis was done. FTIR revealed significant difference for amide I only for third (p<0.001), and a higher value for the apical in relation to the cervical third within the non-irradiated group. For phosphate and amide III, there was significant difference only for irradiation (p=0.015 and p=0.038, respectively). Tukey’s test revealed that within the cervical third the irradiated dentin presented altered values of these chemical components. For carbonate, there was significant difference only for irradiation (p=0.002), and Tukey’s test showed that within the cervical and apical thirds the irradiated dentin presented lower values of carbonate. Regarding the ratios, showed significant difference for third (p<0.001) in the mineral/matrix ratio (M:M), while irradiation and the interaction between the study factors did not (p=0.826 and p=0.460, respectively). For carbonate/mineral ratio (C:M), there was significant difference only for irradiation (p=0.001). In all thirds, the irradiated dentin presented lower values of C:M ratio when compared to the non-irradiated one. For amide I/CH2 ratio, ANOVA showed significant difference only for third (p=0.007). Raman spectroscopy data were analyzed for 961/1458 cm−1 ratios and revealed that the irradiation (p=0.818), resin cement (p=0.381) and the interaction between them (p=0.273) had no influence. The analysis of the bonding interface by CLSM showed less adhesive interaction in the irradiated dentin in both cements. Under the conditions of this in vitro study, ionizing radiation altered the root dentin molecules, mainly in the cervical third. Resin cements had less interaction with irradiated root dentin. RelyX ARC conventional resin cement had greater interaction with irradiated dentin than RelyX U200 self-adhesive resin cement.