Effect of Radiotherapy, Antioxidant and Adhesive on Bonding of Dentin

Objectives: The purpose of this study was to evaluated the effect of radiotherapy, adhesive systems and antioxidant N-acetylcysteine (NAC) on the microtensile bond strength (μTBS) of the dentin-composite interface.
Methods: Sixty human thirds molars were sectioned to expose middle dentin surface and distributed according to: (1) adhesive system (Adper Single Bond 2 and Clearfil SE Bond) applied, (2) application or not of N-acetylcysteine (NAC), and (3) submission to 60 Gy total radiation (2 Gy daily doses, 5 days/week for 6 weeks) before restoration procedure (RtRes); after restoration procedure (ResRt) or not submitted to radiotherapy (Control group). A block of 6 mm thickness resin composite Z250 (3M ESPE) was constructed on dentin and each 2 mm thickness was light cured for 40 seconds. After stored in deionized water at 37^oC for 24 hours, the specimens were sectioned perpendicularly to bonding area to obtain sticks with a cross-sectional area of 1mm², and submitted to the µTBS at a crosshead speed of 1.0 mm/min. Data were submitted to three way ANOVA and Tukey’s post-hoc test (α=0.05).
Results: There was significant difference between the μTBS (MPa) of Clearfil SE Bond (40.1±3.9) and Single Bond 2 (36.3±3.0). Control (38.4±4.6) and ResRt (40.3±4.6) presented μTBS significantly higher than RtRes (35.9±0.5). N-acetylcysteine (36.5±3.3) significantly reduced μTBS compared to groups without N-acetylcysteine application (39.9±3.9).
Conclusions: The radiotherapy before composite restoration procedure decreased the µTBS. Statistical difference was observed between the adhesive systems. The N-acetylcysteine reduced µTBS regardless the other conditions.