Femtosecond laser versus hydrofluoric acid: Effects on the resin bond strength of CAD/CAM materials

This study evaluated the influence of femtosecond (fs) laser micromachining and hydrofluoric acid (HF)-etching on the surface roughness (Ra) and resin bond strength of restorative materials. The study used 120 rectangular-shaped specimens from four computer-aided design/manufacturing (CAD/CAM) blocks (lithium-disilicate glass-ceramic [LDS; e.max CAD], leucite-reinforced glass-ceramic [LGC; Empress CAD], zirconia-reinforced lithium-silicate [ZLS; Vita Suprinity], and polymer-infiltrated-ceramic-network [PICN; Vita Enamic]) and divided them into three subgroups based on the surface treatments applied: Control, HF-etching (HF), and fs-laser irradiation (FS). Surface roughness was measured using a surface profilometer. The surfaces were examined by a scanning electron microscope. A silane bonding agent was applied, and a self-adhesive dual-cure resin cement was bonded to the surfaces. The shear bond strength (SBS) test was conducted using a universal test device. FS-treated groups had higher Ra than HF-treated specimens. PICN showed higher Ra than other materials among the FS-treated groups. The HF-treated LDS showed the highest SBS. ZLS had the lowest SBS among the etched groups. Regardless of the material, the fs-laser treatment resulted in significantly higher SBS values than seen for controls. Fs-laser micromachining could be a promising alternative to conventional HF-etching, given its potential to uniformly roughen the bonding surface of CAD/CAM materials and improve resin bonding.