A Functionally Graded PICN Material for Biomimetic CAD-CAM Blocks

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.

Bonding performance of dispersed filler resin composite CAD/CAM blocks with different surface treatment protocols

“…In the last decade, the continuous improvement of resin composites as well as the adhesive dentistry led to the development of resincomposite blocks (RCBs). Easier fabrication, favorable properties such as lower hardness and elastic modulus, and the possibility of a direct intraoral repair are the major advantages of RCBs compared to ceramics [1][2][3] .…”

Orthodontic‐assisted one step‐ no prep technique: A straightforward and minimally‐invasive approach for localized tooth wear treatment using polymer‐infiltrated ceramic network CAD‐CAM prostheses

“…It is noteworthy to mention that minor chippings were observed on posterior restorations: they were related to borders of very thin occlusal veneers, which were submitted to occlusal contacts, while no major fracture of restorations was observed, despite the high occlusal stress 26 . The development of new generations of PICNs, with higher mechanical properties should reduce these types of complications 26,27 . The results confirm those of the 2‐year study about the one step‐no prep approach for treatment of generalized tooth wear, in which PICN palatal veneers behaved very well and some minor chippings were observed with very thin table tops 28 .…”

“…Gulamali et al highlighted the need of maintenance with direct composites 25 . It is noteworthy to mention that minor chippings were observed on posterior restorations: they were related to borders of very thin occlusal veneers, which were submitted to occlusal contacts, while no major fracture of restorations was observed, despite the high occlusal stress 26 . The development of new generations of PICNs, with higher mechanical properties should reduce these types of complications 26,27 .…”

Cerámicas: una actualización

“…En cuanto a sus propiedades ópticas, sin bien es cierto que los fabricantes proveen una gama grande de colores y brillos, con capas de resina transparente y opaca que intentan asemejarse a la dentina y al esmalte, hasta hoy en día, las PICN no consiguen igualar las características ópticas de los dientes naturales 67 .…”

“…As for its optical properties, it is true that manufacturers provide a large range of colors and glare, with layers of transparent and opaque resin that try to resemble dentin and enamel, until today, the PICN can not match the optical characteristics of natural teeth 67 .…”