The aim of this laboratory research was to evaluate and compare the effect of various surface pretreatments on the shear-bond strength (SBS) of a self-adhesive resin cement to two CAD/CAM materials: a conventional particulate-composite (Cerasmart 270) and an experimental short glass fiber-reinforced composite (SFRC).

Specimens were prepared from composite blocks with dimensions of 14 mm × 12 mm × 3 mm (n = 80 /material). The bonding surfaces were standardized by grinding with 320-grit silicon carbide papers. The specimens were then divided into two main subgroups (n = 40 /group) based on the surface pretreatment protocol: airborne-particle abrasion (APA) or airborne-particle abrasion plus hydrofluoric acid for 60 s (APA + HF). Following surface pretreatment, a self-adhesive resin cement was applied to the block surface using metallic cylinders. Half of the specimens were subjected to the SBS test after 48 h of water storage, while the remaining half after hydrothermal accelerated aging by 16 h boiling. Scanning electron microscopy (SEM) and three-dimensional optical profilometer were used to examine the topography of CAD/CAM composites following surface pretreatment.

Both CAD/CAM composite type and surface pretreatment protocol significantly influenced SBS (p < 0.05). For Cerasmart 270, the APA + HF protocol resulted in higher SBS values compared with airborne-particle abrasion alone. In contrast, for the SFRC CAD, airborne-particle abrasion alone produced higher SBS values than the APA + HF protocol. The effect of hydrothermal aging on shear bond strength was dependent on the surface pretreatment and material type, rather than aging alone. SEM analysis revealed distinct surface morphological differences among the tested materials and pretreatment methods.

Airborne-particle abrasion alone was sufficient to achieve high and stable bond strength for the SFRC CAD/CAM composite. In contrast, the application of hydrofluoric acid following airborne-particle abrasion was necessary to optimize bonding of the self-adhesive resin cement to the conventional CAD/CAM composite.