Shear Bond Strength of CAD/CAM Ceramics and Composites Bonded to Er:YAG-Irradiated Dentin with Different Universal Adhesive Strategies

This in vitro study evaluated the shear bond strength (SBS), morphology, and chemistry of CAD/CAM (computer-aided design/computer-aided manufacturing) ceramics and composites bonded to Er:YAG-irradiated dentin using universal adhesive strategies. A total of 102 human dentin discs were randomly allocated to etched control (E), laser-irradiated (I; 10 Hz, 150 mJ, 5 s), or irradiated-and-etched (IE) conditions. Ninety specimens were bonded to a Cerasmart composite (CSM) or leucite-reinforced ceramic (LRF), while 12 were used for scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). EDX showed marked mineral depletion after etching, with the Ca/P ratio decreasing from 1.58 in control dentin to 1.28 in E and IE specimens. LRF showed higher SBS than CSM (14.12 ± 5.14 vs. 10.94 ± 3.76 MPa); E-LRF had the highest SBS (15.48 ± 3.75 MPa) and I-CSM the lowest (9.57 ± 4.05 MPa), with Tukey significance only seen between these groups (p = 0.009). A two-way ANOVA showed a significant material effect on SBS (p = 0.002), whereas dentin pretreatment (p = 0.185) and material × pretreatment interaction (p = 0.719) were not significant. In conclusion, although Er:YAG irradiation modified dentin morphology and surface chemistry, dentin pretreatment had no statistically significant effect on SBS. Phosphoric acid etching nonetheless remained the most consistent conditioning approach in descriptive terms, as irradiated-and-etched dentin achieved SBS values comparable to etched-only dentin, whereas irradiation alone yielded the lowest descriptive values. This observation should be confirmed by studies incorporating thermocycling, long-term storage, and fatigue loading.