Bond strength evaluation of universal adhesives applied in etch-and-rinse mode on sound and irradiated dentin.

Purpose: To evaluate the laboratory microtensile bond strength (µTBS) of universal adhesives applied in etch-and-rinse mode on irradiated and sound human dentin.

Methods: Dentin specimens of 135 freshly extracted human third molars were divided in three superordinate groups. Each tooth received either no irradiation (control group), 5 Gy (2 Gy/2 Gy/1 Gy in 3 consecutive days) or the high-level therapeutic dose of 60 Gy (test groups) applied fractionally (2 Gy/day, 5 days/week, 6 weeks). Samples from each group were randomly divided into three subgroups assigned to three established universal adhesives (Futurabond U, AdheSE Universal, Xeno Select) in just the etch-and-rinse application mode (n= 15). Bond strength was assessed with a universal testing machine 15 minutes after application and light curing of the adhesive materials. Statistical analysis was performed using a two-way ANOVA (P< 0.01) and Tukey's test (P< 0.05).

Results: Regarding all experimental groups ANOVA showed significant effects on µTBS of dentin irradiation and the used adhesives (P< 0.01, ANOVA). In nearly all groups, a decrease of µTBS was observed when used on highly irradiated dentin. However, comparing the different groups, no significant influence of high-level radiation on the microtensile bond strength of the three universal adhesives assessed in etch-and-rinse application mode could be determined (P> 0.05, Tukey's test).

Clinical significance: Within the limitations of this laboratory study, no significant effects of low- and high-level tumor irradiation on the bond strength of universal adhesives can be detected after application in etch-and-rinse mode. Consequently, this mode of application may be considered a viable option for patients who have undergone radiation therapy when using universal adhesive systems for luting restorative materials.