Commercial trends in universal adhesive evolution: updated formulations do not consistently improve dentin bond strength after aging compared with predecessors and a multistep reference.

BACKGROUND

To evaluate whether recent commercial evolutions of universal adhesives improve dentin bond strength after aging and interfacial characteristics compared with predecessor formulations and a multistep reference.

METHODS

Three updated universal adhesives (AFB-00, Scotchbond Universal Plus, and Clearfil Universal Quick 2) and their respective predecessors (G-Premio Bond, Scotchbond Universal, and Clearfil Universal Quick) were evaluated. OptiBond FL served as a multistep etch-and-rinse reference. One hundred eighty human molars were prepared to expose mid-coronal dentin surfaces and assigned to 15 groups (n = 12 per group). Adhesives were applied in self-etch (SE1) or etch-and-rinse (ER2) modes according to the applicable manufacturers' instructions. The macroshear bond strength (SBS) was measured after 6 months of storage in water. Failure modes were recorded, and representative samples were analyzed using scanning electron microscopy (SEM) to assess the interfacial morphology and adhesive layer thickness. The data were analyzed using one-way ANOVA and Tukey's post hoc test (α = 0.05).

RESULTS

After aging, SBS differed among protocols. AFB-00 and Clearfil Universal Quick 2 performed comparably to their predecessors, whereas Scotchbond Universal Plus showed a significantly lower SBS than Scotchbond Universal. Most universal adhesive protocols showed SBS values comparable or superior to the multistep reference, except Clearfil Universal Quick and Clearfil Universal Quick 2 in self-etch mode. SEM revealed strategy-dependent interfacial patterns and marked differences in adhesive film thickness, particularly for AFB-00 without air drying.

CONCLUSIONS

Recent commercial evolutions of universal adhesives did not systematically improve dentin bond strength after aging. The observed modifications primarily affected the interfacial morphology and adhesive thickness rather than demonstrating consistently higher SBS values after aging. For clinicians, these findings suggest that commercial evolutions of universal adhesives may reflect distinct formulation strategies rather than incremental improvements, and that the performance of updated materials cannot be assumed from that of their predecessors.