Objectives: The objective of this study was to evaluate the microtensile bond strength (µTBS) of three universal adhesives applied in etch-and-rinse and self-etch mode on irradiated and sound human dentin.
Methods: 180 extracted third molars were specially prepared allowing dentin perfusion and randomly assigned to two superordinate groups. Ninety teeth received either no irradiation or the high-level therapeutic dose of 60 Gy applied fractionally (2 Gy/day, 5 days/week, 6 weeks). Specimens from each group were randomly divided into six subgroups assigned to three established universal adhesives in either etch-and-rinse or self-etch mode (n=15): Futurabond^® U (Fer0, Fer60, Fse0, Fse60), AdheSE^® Universal (Aer0, Aer60, Ase0, Ase60), Xeno® Select (Xer0, Xer60, Xse0, Xse60). Bond strength was measured using an universal testing machine immediately after application and light curing of the adhesive materials.
Results: The effect of dentin irradiation and application mode for the adhesive restoration was significant (p<0.01, ANOVA). In all groups, a decrease of µTBS was observed when used on irradiated dentin. No significant influence of high level radiation on the bond strength in both modes of Futurabond® U and AdheSE^® Universal could be evaluated (p>0.05, Tukey’s test). Only Xeno^® Select showed significantly reduced bond strength in self-etch mode after irradiation (Xse60) compared to non-irradiated specimens (Xse0) (p<0.05, Tukey’s test). Evaluated µTBS of all groups (mean values, standard deviations in MPa): Fer0: 23.64 (6.76); Fer60: 17.88 (7.54); Fse0: 23.87 (7.49); Fse60: 19.21 (7.34); Aer0: 29.97 (7.18); Aer60: 29.24 (7.28); Ase0: 35.10 (8.41); Ase60: 26.30 (10.07); Xer0: 26.06 (8.20); Xer60: 22.74 (6.22); Xse0: 24.17 (8.36); Xse60: 11.42 (3.86).
Conclusions: Within the limitations of an in vitro study, some effects of high-level tumour irradiation on the bond strength of universal adhesives could be detected. These effects were strongly associated to the used material and application mode.