Development of silicon nitride ceramic for CAD/CAM restoration.

White Silicon nitride (Si ₃ N ₄ ) 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 Si ₃ N ₄ for fabrication of CAD/CAM dental restorations. The related properties of this novel Si ₃ N ₄ were evaluated including sintered shrinkage, flexural strength and fracture toughness. Partially sintered Si ₃ N ₄ ceramic blocks were prepared by heating at 1,400°C for 2 h under N ₂ gas. After full sintering at 1,650 ^o C 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 Si ₃ N ₄ were more than 800 MPa and 5 MPa•m ^1/2 , the white Si ₃ N ₄ developed in this study can be used to fabricate multi-unit dental restorations According to ISO 6872.