Effect of Accelerated Aging on the Microtensile Bond Strength of a Two-Step Adhesive Containing a Universal Adhesive Primer, an in vitro study

Despite the advantages of one-step universal adhesives, concerns about their bond durability exist. By introducing a two-step adhesive using universal bonding technology, the study aimed to evaluate the effect of accelerated aging on the microtensile bond strength (µTBS) of this adhesive when applied to dentin.

In this in vitro study, 16 extracted sound human third molar teeth were selected. Specimens were prepared by cutting the occlusal enamel perpendicular to the longitudinal axis and categorized into four groups of 18 each: G2-Bond Universal (GC Corp, Tokyo, Japan) in etch-and-rinse mode (GU-ER), G2-Bond Universal in self-etch mode (GU-SE), G-Premio Bond in etch-and-rinse mode (GP-ER), and G-Premio Bond (GC Corp, Tokyo, Japan) in self-etch mode (GP-SE). The resin composite was bonded to the dental surfaces based on the manufacturer’s instructions and light-cured for 10 seconds using an LED curing unit (Demetron A2, Kerr, Scafati, Italy, 1200 mW/cm²). The bonded specimens were then sectioned into 1 mm² sticks and divided into two subgroups (n=36). One subgroup (9 specimens from each adhesive) underwent thermal cycling, while the other was immersed in 10% sodium hypochlorite for three hours to simulate accelerated aging. The µTBS was measured, and failure modes were determined. Data were analysed using two-way ANOVA, the Sidak test, and the Independent Samples T-Test

The highest mean μTBS was associated with GU-SE (29.63 ± 8.59 MPa), while the lowest was observed with GP-ER (18.65 ± 9.33 MPa). The µTBS values decreased following aging (p < 0.001). The values for GU-SE and GU-ER were significantly higher than those for GP-ER (p < 0.001 and p = 0.005, respectively). GU-SE and GU-ER showed a slight, statistically insignificant decrease in bond strength with aging (p = 0.133 and p = 0.060, respectively). However, GP-SE and GP-ER showed significant reductions in bond strength after aging (p = 0.004 and p = 0.001, respectively). The interaction between accelerated aging and study groups was not significant (p = 0.311), indicating a uniform effect of aging in all groups. Failure modes were similar in groups (p > 0.05), with adhesive failure being the most common type. G-Premio had more adhesive failures than G2-Bond, though this difference was not statistically significant.

Two-step universal adhesive performed better than one-step system during aging. In etch-and-rinse mode, the two-step adhesive significantly improved bond strength, while in self-etch, both adhesives showed similar performance.