Bond Strength Evaluation of Universal Adhesives Applied in Self-Etch and Etch-and-Rinse Modus on Sound and High-Level Irradiated Dentin - a Controlled Laboratory Study

Background: Radiotherapy is an important part of the medical therapy concept treating tumors in the head and neck region; however, the impact on the field of dentistry could be im-mense. The objective of this study was to evaluate the microtensile bond strength (µTBS) of uni-versal adhesives and to compare the results of different application modes (etch-and-rinse and self-etch) on irradiated and sound human dentin. Methods: Dentin specimen of 180 extracted human wisdom teeth were divided in two superordinate groups. Ninety teeth received either no irradiation (control group) or the high-level therapeutic dose of 60 Gy (test group) applied frac-tionally (2 Gy/day, 5 days/week, 6 weeks). Samples from each group were randomly divided in-to six subgroups assigned to three established universal adhesives (Futurabond® U, VOCO; AdheSE® Universal, Ivoclar Vivadent; Xeno® Select, Dentsply) in both conceivable application modes: etch-and-rinse and self-etch (n = 15). Bond strength was assessed with a universal testing machine immediately after application and light curing of the adhesive materials. Statistical analysis was performed using two-way ANOVA (p<0.01) and Tukey's test (p<0.05). Results: The effect of dentin irradiation and application mode for the adhesive restoration was found to be significant (p<0.01, ANOVA). In all groups, a decrease of µTBS could be observed when used on irradiated dentin. However, no significant influence of high level radiation on the bond strength of Futurabond® U and AdheSE® Universal in both modes could be evaluated (p>0.05, Tukey´s test). Solely in the case of the adhesive system Xeno® Select, significantly reduced bond strength could be determined in self-etch mode after irradiation (group 60 Xse) compared to the control group (0 Xse) (p<0.05, Tukey´s test). Conclusions: Within the limitations of an in vitro study, some effects of high-level tumor irradiation on the bond strength of universal adhesives can be detected. However, these effects were strongly depending on the used material and application mode.