Development of silicon nitride ceramic for CAD/CAM restoration

White Silicon nitride (Si₃N₄) ceramic has unique characteristics. Because of its high fracture toughness, strength, and biocompatibility, it can therefore be used to fabricate dental restorations. The purpose of this study was to produce partially-sintered block of Si₃N₄ for fabrication of CAD/CAM dental restorations. The related properties of this novel Si₃N₄ were evaluated including sintered shrinkage, flexural strength and fracture toughness. Partially sintered Si₃N₄ ceramic blocks were prepared by heating at 1,400°C for 2 h under N₂ gas. After full sintering at 1,650^oC for 2 h, the linear shrinkage value was recorded at 19.88±0.56%. The flexural strength and fracture toughness were measured, the results were 891.21±37.25 MPa and 6.33±0.30 MPa•m^1/2, respectively. These results showed that flexural strength and fracture toughness of Si₃N₄ were more than 800 MPa and 5 MPa•m^1/2, the white Si₃N₄ developed in this study can be used to fabricate multi-unit dental restorations According to ISO 6872.