Bonding efficacy of highly translucent zirconia and lithium disilicate glass ceramics after femtosecond laser irradiation

Abstract

Purpose: This study investigated the effects of femtosecond laser (FL) irradiation on the surface roughness and shear bond strength of high-translucency zirconia (6 mol% yttria-partially stabilized zirconia [6Y-PSZ]) and lithium disilicate (Li₂SiO₃) glass ceramics.

Methods: Fully sintered square-shaped specimens of 6Y-PSZ (7 groups; 20 specimens/group) and Li₂SiO₃ (8 groups; 20 specimens/group) were surface-treated via sandblasting (50-μm alumina sand or glass beads) or FL irradiation (20- or 40-μm dot or cross-line patterns) or using Monobond Etch & Prime (Ivoclar Vivadent AG; only for Li₂SiO₃ specimens). The surface roughness (arithmetic average [Sa] and developed interfacial area ratio [Sdr]) and shear bond strength after 24 h and 10,000 thermal cycles were measured and statistically analyzed.

Results: The surface roughness of both ceramics significantly increased after 40-μm cross-line FL irradiation. The Sdr also significantly increased after FL irradiation. The 20- and 40-μm cross-line laser-irradiated 6Y-PSZ samples showed the highest shear bond strength after 24 h and 10,000 thermal cycles, respectively. Li₂SiO₃ glass-ceramic specimens showed the highest shear bond strength after Monobond Etch & Prime treatment for both groups. The 40-μm cross-line laser-irradiated Li₂SiO₃ glass-ceramic specimens exhibited high shear bond strength after thermal cycling.

Conclusions: FL significantly increases the bonding efficacy of 6Y-PSZ and Li₂SiO₃ glass ceramics. Furthermore, Monobond Etch & Prime is effective for the surface treatment of Li₂SiO₃ glass ceramics. Therefore, FL can be used to effectively treat the surfaces of dental restorations in clinical settings, facilitating enhanced adhesion between the restoration and the tooth.