Methods: Were collected 60 human teeth divided into 2 groups, irradiated (Ir), 60 Gy of gamma radiation fractioned in daily values of 2 Gy, five days a week; and non-irradiated (NIr). The teeth were subdivided into a control group (C) and 2 mouthwash protocols used 3 times a day: 0.12% chlorhexidine (Cl) and 0.05% sodium fluoride (F). The specimens were serial cut and the dental structures: enamel (E), coronal dentin (Dc) and root dentin (Dr) were tested parallel (p) and transversal (t), to prism orientation and dentin tubules by microtensile testing. Failure modes were analyzed by scanning electron microscopy.
Results: UTS means and (standard deviation) were: EpNIrC-42.6±12.9, EpNIrF-42.2±15.5, EpNIrCl-43.2±13.7; EpIrC-28.1±8.2, EpIrF-27.3±6.3, EpIrCl- 38.5±4.9; EtNIrC-18.7±4.7, EtNIrF-17.7±4.4, EpNirCl-18.0±2.0; EtIrC-10.7±3.1, EtIrF-11.0±2.6, EpIrCl-15.9±2.7; DcpNIrC-56.9±15.1 DcpNIrF-57.6±12.5, DcpNIrCl-55.1±12.1; DcpIrC-39.2±8.4, DcpIrF-45.1±7.8, DcpIrCl-39.6±7.6; DctNIrC-90.4±15.6, DctNIrF-89.4±16.7, DctNIrCl-91.6±16.9; DctIrC-54.6±10.7, DctIrF-76.2±12.5, DctIrCl-53.2±13.1; DrtNIrC-50.7±10.1, DrpNIrF-51.7±13.4, DrpNIrCl-52.1±13.2; DrpIrC-34.6±12.5, DrpIrF-32.5±7.3, DrpIrCl-34.2±8.5; DrtNIrC-69.2±11.4, 67.4±15.2, 68.2±16.5; DrtNIrF-52.1±19.0, 50.0±12.5, DrtNIrCl-53.2±10.3. The Tukey test (P <0.05) revealed that the presence of irradiation reduces the UTS of enamel, crown and root dentin regardless of the orientation of the prisms and tubules.
Conclusion: The rinsing with chlorhexidine 0.12% prevent partially the damage of the mechanical properties of crown dentin irradiated and that 0.05% sodium fluoride recovered the UTS of enamel irradiated similarly to the non-irradiated enamel.