The effect of surface treatments on the bond strength of different aesthetic restorative materials

Aim: The aim of this study was to evaluate the effects of different surface conditioning methods on the shear bond strength of aesthetic dental restorative materials to enamel. Materials and Methods: In this in vitro study, a total of 146 enamel samples were used. Six teeth were allocated for SEM analysis, and the remaining samples were embedded in acrylic resin with the labial surfaces exposed. The CAD/CAM groups included Vita Enamic (VITA Zahnfabrik, Bad Säckingen, Germany) and Lava Ultimate (3M ESPE, St. Paul, MN, USA). Filtek Ultimate (3M ESPE, St. Paul, MN, USA) was used in the composite groups. CAD/CAM materials were standardized as cylindrical specimens (3 mm × 3 mm), and each material was divided into four subgroups according to the applied surface treatment: sandblasting, hydrofluoric acid, Nd:YAG laser (20 Hz), and control (n = 10). In the composite groups, samples were divided into two main groups according to the adhesive system (total-etch and self-etch). Within each adhesive group, three different surface treatments were applied: Nd:YAG laser (20 Hz), Nd:YAG laser (10 Hz), and control. After enamel standardization, CAD/CAM blocks were cemented using a dual-cure resin cement (RelyX U200, 3M ESPE, St. Paul, MN, USA), and composite specimens were formed using silicone molds. Shear bond strength testing was performed using a universal testing machine (Autograph AGS-X; Shimadzu Corp., Kyoto, Japan), and failure modes were evaluated under a stereomicroscope; SEM analysis was also conducted. Statistical analyses were performed using SPSS software. Results: Surface treatments significantly affected the bond strength of CAD/CAM materials (p < 0.05). The highest bond strength was obtained in the Vita Enamic sandblasting group (29.06 ± 5.36 MPa). Nd:YAG laser showed higher mean shear bond strength values compared with the control groups in both CAD/CAM materials. In composite resin specimens, the total-etch adhesive system demonstrated higher bond strength values than the self-etch system. In the total-etch group, application of 10 Hz Nd:YAG laser significantly increased bond strength (22.85 ± 5.12 MPa). Conclusion: It was observed that the structural characteristics of the restorative material, surface treatment parameters, and adhesive protocol play a decisive role in bond strength. Considering that Nd:YAG laser surface treatment may support bond strength under specific material and application conditions, it can be regarded as an alternative surface preparation method in clinical practice. Keywords: CAD/CAM, Composite Resin, Surface Treatments, Shear Bond Strength, Nd:YAG Laser