Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used in the fabrication of dental restorative materials such as inlays, crowns, and bridges. Along with the advance in the CAD/CAM systems, various types of CAD/CAM have been developed so far. For instance, contemporary CAD/CAM ceramics, zirconia and lithium disilicate glass, can be used as all-ceramic crowns. On the other hand, the mechanical properties of the CAD/CAM ceramics differ from those of human enamel and dentin.

Polymer-infiltrated ceramic network (PICN) materials have recently received much attention due to their mechanical compatibility with human enamel. The PICN materials are prepared via polymer-infiltration into a pre-sintered porous ceramic. Since the PICN materials have a unique microstructure consisting of a dual-network structure of the ceramic skeleton and polymer phase, their mechanical properties exhibit intermediate between those of ceramics and resins (polymers). The PICN structure differs from conventional resin composites which comprise filler dispersed in a resin matrix. Commercial CAD/CAM block, VITA ENAMIC, is one of the most famous PICN materials. ENAMIC has been applied to tooth restorative material for over a decade. Many basic and clinical studies have been conducted to demonstrate that the PICN materials are relatively close to human enamel in terms of mechanical properties such as flexural strength and flexural modulus. On the other hand, there is room for further improvement of the mechanical properties of PICN materials.

We have developed novel silica-based PICN materials so far. The silica-based PICN composites exhibited a similar Vickers hardness to enamel and flexural modulus to dentin. For instance, the 3D-printed PICN materials have Vickers hardness of ~300 and flexural modulus of ~ 20 GPa. Overall, the silica-based PICN composites are promising candidates for next-generation tooth restorative materials. In this presentation, we introduce recent research on the development of the silica-based PICN composites for applications of CAD/CAM milling materials, 3D-printable materials, and castable materials.