Effect of Agitation Methods on Dentin Bond Strength of HEMA-free Dentin Adhesive

Objectives: The aim of this study was to evaluate the effect of different agitation methods on bonding performance in 2-hydroxyethyl methacrylate (HEMA)-free universal dentin adhesive.
Methods: Sixteen caries-free third molars were used. The occlusal enamel was removed and the flat dentin surface was exposed. This surface was polished with 320-grit silicon carbide abrasive paper to produce smear layer. The teeth were divided randomly into four groups according to agitation modality and artificial aging time. The HEMA-free universal dentin adhesive (G-Premio BOND, GC Corporation, Japan) was applied to the dentin surface with self-etch mode and light-cured for 20 seconds with passive agitation (PA) or active agitation (AA). The composite resin was built up incrementally to a height of 4mm. Composite resin-dentin beams with 1 x 1mm² surface area were produced for microtensile bond strength (μTBS) test. Specimens were equally divided into two sub-groups; immediate aging (PA0, AA0) and artificial aging (PA1, AA1). Thirty beams were assigned for each experimental group. For artificial aging, the specimens were immersed in a 10% sodium hypochlorite solution for 1 hour. The μTBS test was performed using testing machine (Micro Tensile Tester, BISCO Inc., USA) at a crosshead speed of 0.5mm/minute. Failure modes were observed under a streomicroscope. Each bonded interface was analyzed with transmission electron microscopy (TEM).
Results: One-way ANOVA results indicated that AA groups showed higher μTBS than PA groups (p<0.05). There were no significant differences according to aging within groups of same application mode (p>0.05). Failure mode test presented commonly adhesive failure in the dentin; Adhesive failure mode was over 90% in all experimental groups.
Conclusions: Active agitation modality of universal dentin adhesive may enhance their immediate and aged bonding performance to dentin.