Effects of simulated pulpal pressure on all-in-one adhesive dentin bonding

Objective: This study evaluated the effect of simulated pulpal pressure on the microtensile bond strength (µTBS) of recently introduced all-in-one self-etching adhesives applied in deep dentine. Methods: Flat deep coronal dentine discs with a 0.7-0.9 µm of residual dentine thickness were obtained from human third molars and divided into 2 groups. Half of the teeth were adapted into a fluid transport model for simulated pulpal pressure (20 cm H₂O) during bonding procedures. Three one-step self-etch adhesives (Clearfil 3S/C3S, G Bond/GB, One Up Bond F Plus /OUPF) were used. Resin composite build-ups were made using a light-cured flowable resin composite (Gradia Direct LoFlo, GC Corp.) Specimens were immediately sectioned into beams that were tested in tension at 0.5mm/min. µTBS data (MPa) The bond strength data were evaluated by a two-way ANOVA design with "adhesive type" and "presence/absence of pulpal pressure” as the two factors. Multiple comparisons were performed with the Fisher's PLSD test. Statistical significance were set at ^ = 0.05. Results: Mean µTBS and standard deviations (MPa) are listed below. For the vertical column "No pulpal pressure", subgroups with the same upper case letter superscripts are not statistically significant (p > 0.05). For the vertical column "With pulpal pressure", subgroups with the same lower case letter superscripts are not statistically significant (p > 0.05). For each horizontal adhesive row, significant difference (p < 0.05) between the "No pulpal pressure" subgroup and the "With pulpal pressure" subgroup is indicated by different numerical superscripts.

Conclusions: C3S exhibited the highest µTBS in the absence of simulated pulpal pressure. When bonding was performed under hydrostatic pulpal pressure, the highest µTBS bond strength was obtained by GB. Intrapulpal pressure produced a significant decrease in bond strengths of the one-step adhesives C3S, GB and OUPF.