Blanca Irma Flores-Ferreyra

Despite aesthetic trends, metal–ceramic restorations continue to be widely accepted due to their durability, and variations in surface preparation process can significantly influence bond strength outcomes. The purpose of this study was to determine whether there are differences in the bond strength depending on three surface treatment protocols for veneering ceramics on Ni-Cr alloys. The following surface treatments were used: (1) control (C) (no treatment), (2) airborne-particle abrasion (APA) with 50 µm Al₂O₃ (G1-APA), (3) APA followed by oxidation (G2-APA-O), and (4) APA-O, with a second APA (G3-APA-O-APA). Subsequently surface roughness (R_a and R_z) was evaluated using profilometry, hardness was measured through Leeb’s hardness dynamic test (HLD), morphology was investigated through scanning electron microscopy (SEM), and the chemical composition of the alloy surface was evaluated using energy-dispersive spectroscopy (EDS). After surface treatments, veneering ceramic was applied, the debonding crack initiation strength (DCIS) was investigated through the three-point bending test, failure mode was classified using a stereoscopic microscope, and chemical characterization of the fractured surfaces was performed using Raman spectroscopy (RS). For DCIS, G2-APA-O demonstrated the highest value 63.97 ± 44.40 (MPa) (p < 0.05). The results of this study indicate that oxidation treatment has a positive effect on the bonding strength between veneering ceramic and Ni-Cr alloys.

Bioceramic endodontic cements, known for their antibacterial properties, calcium ion release, and alkaline pH, may come into contact with various irrigants after furcal perforation repair. This study aimed to evaluate the effect of different irrigating solutions and setting times on the shear bond strength (SBS) of Biodentine^® (Septodont, Saint-Maur-des-Fosses Cedex, France) to a self-adhering flowable composite. Sixty Biodentine^® (Septodont, Saint-Maur-des-Fosses Cedex, France) blocks were prepared and divided into two groups based on the setting time: 72 h and 7 days. These were further subdivided into five subgroups based on the irrigation solution applied: distilled water, sodium hypochlorite, ethylenediaminetetraacetic acid, chlorhexidine, and phosphoric acid. They were then restored with Dyad Flow^TM (Kerr^TM, Orange, CA, USA). SBS and failure modes were assessed at 24 h and 6 months. A two-way analysis of variance (ANOVA) test was performed to analyze the effect of the different irrigating solutions and setting times on the SBS of Biodentine^® (Septodont, Saint-Maur-des-Fosses Cedex, France) and Dyad Flow^TM (Kerr^TM, Orange, CA, USA). The level of significance was set at a ≤0.05. At 24 h, SBS was significantly influenced by both the irrigant solution (p = 0.029) and setting time (p = 0.018); at 6 months, SBS was influenced only by the irrigating solutions (p < 0.001). The predominant mode of bond failure was adhesive across all groups. In conclusion, while the setting time did not affect the bond strength, certain irrigating solutions reduced it. Thus, careful consideration of surface treatments applied to Biodentine^® is crucial for successful endodontic and restorative outcomes.

The surface roughness, morphology and shear bond strength (SBS) of dental zirconia using three different surface treatment techniques were evaluated. Three groups of sintered zirconia blocks were treated as follow, 1) Airborne-particle abrasion (APA) group (G1-APA), 50-µm Al2O3; 2) APA and 9% hydrofluoric acid etching (G2-HF); 3) APA and Sodium Hydroxide (G3-NaOH). The specimens were evaluated for roughness [atomic force microscope (AFM)], morphology [Scanning Electron Microscope (SEM)] and for SBS in the universal testing machine. The AFM revealed changes in the roughness after the surface treatments, however there was not Ra difference between groups, SEM analysis revealed changes in surface morphology for all surface treated specimens. For SBS, significant difference was found between G1-APA=8.4±2.7 MPa and G2-HF=3.3±0.6 MPa (p<0.05) and G2-HF and G3-NaOH=9.0±3.0 MPa (p<0.05). The main fracture mode was mixed failure (63%) for G1-APA and G3-NaOH groups. G2-HF showed 100% adhesive failure. SBS was improved with NaOH, however application of HF significantly decreased SBS.