Effect of simulated pulpal pressure on all-in-one adhesive bond strengths to dentine

Objectives: To evaluate the durability of all-in-one adhesive systems bonded to dentine with and without simulated hydrostatic pulpal pressure (PP). Methods: Flat dentine surfaces of extracted human molars were prepared. Two all-in-one adhesive systems, One-Up Bond F (OBF) (Tokuyama Corp., Tokyo, Japan), and Fluoro Bond Shake One (FBS) (Shofu Co., Kyoto, Japan) were applied to the dentine surfaces under either a PP of 0 or 15 cm H₂O. Then, resin composite build-ups were made. The specimens bonded under pressure were stored in 37 °C water for 24 h, 1 and 3 months under 15 cm H₂O PP. Specimens not bonded under pressure were stored under zero PP. After storage, the specimens were sectioned into slabs that were trimmed to hourglass shapes and subjected to micro-tensile bond testing (μTBS). The data were analysed using two-way ANOVA and Holm-Sidak HSD multiple comparison tests (α = 0.05). Results: The μTBS of OBF fell significantly (p < 0.05) when PP was applied during bonding and storage, regardless of storage time. In contrast, although the μTBS of OBF specimens bonded and stored without hydrostatic pressure storage fell significantly over the 3 months period, the decrease was less than half as much as specimens stored under PP. In FBS bonded specimens, although there was no significant difference between the μTBS with and without hydrostatic pulpal pressure at 24 h, by 1 and 3 months of storage under PP, significant reductions were seen compared with the control group without PP. Conclusion: The μTBS of OBF bonded specimens was lowered more by simulated PP than by storage time; specimens bonded with FBS were not sensitive to storage time in the absence of PP, but showed lower bond strengths at 1 and 3 months in the presence of PP.