No abstract

No abstract

The objective of this study was to evaluate the interfacial fracture toughness (IFT) of composite cement with dispersed filler (DF) versus polymer-infiltrated ceramic network (PICN) computer-aided design and computer-aided manufacturing (CAD-CAM) composite blocks after 2 different surface pretreatments using the notchless triangular prism (NTP) test. Two DFs (Cerasmart [CRT] and Lava Ultimate [LVA]), 2 PICNs (Enamic [ENA] and experimental PICN [EXP]), and e.max CAD lithium disilicate glass-ceramic (EMX, control) prism samples were bonded to their counterparts with Variolink Esthetic DC composite cement after either hydrofluoric acid etching (HF) or gritblasting (GR). Both procedures were followed by silanization. All samples ( n = 30 per group) were thermocycled (10,000 cycles) and tested for their IFT in a water bath at 36°C. Moreover, representative samples from each group were subjected to a developed interfacial area ratio (Sdr) measurement by profilometry and scanning electron microscopy (SEM) characterization. EXP-HF gave the highest IFT (1.85 ± 0.39 MPa·m), followed by EMX-HF and ENA-HF, while CRT-HF gave the lowest (0.15 ± 0.22 MPa·m). PICNs gave significantly better results with HF, and DF showed better results with GR. A 2-way analysis of variance indicated that there were significantly higher IFT and Sdr for PICNs than for DF. A positive correlation ( r² = 0.872) was found between IFT and Sdr. SEM characterization showed the specific microstructure of the surface of etched PICNs, indicating the presence of a retentive polymer-based honeycomb structure. Etching of the typical double-network microstructure of PICNs causes an important increase in the Sdr and IFT, while DF should be gritblasted. DF exhibited significantly lower Sdr and IFT values than PICNs. The present results show the important influence of the material class and surface texture, and consequently the micromechanical bond, on the adhesive interface performance of CAD-CAM composites.

No abstract

The objective of this study was to introduce a functionally graded (FG) polymer-infiltrated ceramic network (PICN) block, characterized by a gradient of mechanical properties, as a biomimetic material for computer-aided design and manufacturing (CAD-CAM) prostheses. FG-PICN blocks were manufactured from a slurry of glass-ceramic powder, which was subsequently centrifuged and sintered. The ceramic network was infiltrated with urethane dimethacrylate and polymerized under high temperature-pressure. Blocks were sectioned into 9 layers, and each layer was subsequently cut into 3 samples. Samples were loaded into a 3-point bending device and tested for flexural strength, flexural load energy, and flexural modulus. The volume percentage of glass-ceramic, hardness, and brittleness index were also measured and scanning electron microscopy (SEM) observations were performed. Katana translucent zirconia (HT-ZIR) and e.max-CAD (EMX) were tested for comparison. Flexural strength, flexural load energy, and Weibull modulus of FG-PICN were shown to increase from the first (enamel-like zone) to the ninth layer (dentin-like zone), while, on the contrary, flexural modulus, hardness, brittleness index, and ceramic volume percentage decreased. SEM characterization highlighted a higher porosity in layer 9 than in layer 1. Flexural strength of the dentin-like zone (372.7 ± 27.8 MPa) was similar to EMX and lower than HT-ZIR. Flexural modulus was shown to vary from 41.9 ± 5.1 to 28.6 ± 2.0 GPa from surface to depth. Flexural load energy in the dentin-like zone (27.1 ± 4.9 mJ) was significantly superior to EMX and HT-ZIR. Hardness gradient was shown to be close to tooth tissues. This work introduces FG-PICN blocks, with a gradient of mechanical and optical properties through the entire thickness of the block designed to mimic dental tissues. FG-PICN demonstrated a favorable gradient of flexural strength, elastic modulus, and, most of all, flexural load energy and hardness compared to other CAD-CAM materials, which can promote the biomechanical behavior of single-unit restorations on teeth and implants.