Abstract: Objective:To detect the optimal fusing temperature, the fusing time and the best filler ratio of α-Si₃N₄ and SP₁SiO₂, and to clarify their influence in the properities of dental resin composites. Methods:The α-Si₃N₄ crystalline were mixed with SP₁SiO₂ particle at the ratio of 5:1(Wt%), and then were sintered under 500℃, 650℃, 800℃, 950℃ and 1 100℃ at a rise rate of 250·h^-1 and maintained for 10 min, 30 min and 3 h, respectively(used as α-Si₃N₄-SP₁SiO₂ groups).SP₁SiO₂ particle, α-Si₃N₄ crystalline, mixed and non-fused α-Si₃N₄ and SP₁SiO₂(mixed) groups were set up, and two commercially available resin composites were selected and used as control groups. And they were fully mixed with the resin matrix in 60%(Wt%) after the treatment of cyclohexane solution to make the samples. The flexural strength of specimen was tested and the morphology of section under SEM was analyzed. Then α-Si₃N₄ was mixed with SP₁SiO₂ in a ratio of 2:1. It was fused under the optimal fusing conditions. After the treatment of cyclohexane solution, it was mixed and polymerized with the resin matrix in the proportions of 20%, 40%, 60%, 70% and 75%(Wt%), and two kinds of commercially available resin composites were selected and used as control groups. The flexural strength of specimens was tested and the morphology of section under SEM was analyzed. Results:The maximum flexural strength value in α-Si₃N₄-SP₁SiO₂ groups was at 800℃ and 30 min(P>0.05);the flexural strength value was significantly higher than those in SP₁SiO₂ group, α-Si₃N₄ crystalline group, mixed group and two control groups(P<0.05), and the morphology of section SEM was consistent with the mechanical properties. The flexural strengths of resin composites were increased gradually with the increasing of filler ratios of α-Si₃N₄ and SP₁SiO₂ fusion from 20% to 60%(P<0.05); the flexural strength values of resin composites with the proportion of 60%-70% were not increased significantly, the flexural strength values of resin composites with the proportion of 70%-75% were decreased, and the flexural strength values of the resin composites with the proportion of 60% and 70% were significantly higher than those of resin composites with the proportions of 20%, 40%, 75% and control groups; the morphology of section under SEM was consistent with the mechanical properties. Conclusion:The optimum fusing condition for α-Si₃N₄ and SP₁SiO₂ is 800℃ for 30 min,and the best filler ratio of α-Si₃N₄ and SP₁SiO₂ is 70%.

Key words: α-silicon nitride, more micropore nanometer SiO₂, fusing temperature, fusing time, filler ratio, resin composites