Shear bond strength between a dual-curing luting composite and subtractively vs. additively processed hybrid ceramics

Abstract Background: Digital dentistry has transformed restorative workflows through computer-aided design and manufacturing (CAD-CAM), enabling the use of chemically diverse materials for definitive restorations. Among these, subtractive manufacturing (SM) has demonstrated exceptional outcomes with monolithic restorations. With the emergence of additively manufactured (AM) hybrid dental materials for definitive single-tooth restorations, there is growing interest in evaluating their material-specific properties. While the performance of SM materials has been well-documented in multiple studies, comparable evidence for AM counterparts remains scarce, particularly for bonding behavior. Methodology: A total of 306 specimens were prepared, consisting of two hybrid SM materials and one AM material, with 102 specimens per material. Specimens were randomly assigned to six pretreatment groups: Control, Silanization, 50 μm Al₂O₃ sandblasting, Sandblasting+silanization, 9% hydrofluoric acid etching, Etching+silanization. Surface characteristics were analyzed through surface roughness (Ra), and surface free energy (SFE) quantification, and scanning electron microscopy (SEM). Following adhesive application with a dual-cured resin composite, with half undergoing thermocycling (5000 cycles, 5-55°C). Shear bond strength (SBS) was evaluated using a universal testing machine, followed by fractographic analysis via digital microscopy. Statistical analysis employed two-way ANOVA, Mann-Whitney, and independent t-tests. (α=0.05). Results: Surface roughness demonstrated significant material-dependent variations (p=0.001), with pretreatment strategies (p