To investigate the impact of α-Si₃N₄ and SP₁SiO₂ on the properties of composite resin.

α-Si₃N₄ whiskers and SP₁SiO₂ particles, mixed at ratios of 0∶1, 1∶5, 1∶2, 1∶1, 2∶1, 5∶1 and 1∶0 (Wt%) , respectively, were fused under the condition of 800 ℃ and 30 min. After treatment with cyclohexane solution, the fusion was mixed with the resin matrix at a ratio of 60 Wt% to form a polymer. The polymer composite resin, along with two commercially composite resin products, was used to prepared specimens for testing of flexural strength, fracture toughness, and hardness (n=5 for each resin) . Then the flexural strength, fracture toughness and hardness of these specimens were tested, and the sections of these specimens were studied for morphology under SEM.

The fusion ratio of α-Si₃N₄ whisker and SP₁SiO₂ particles showed great impacts on the flexural strength and fracture toughness of the composite resin. The flexural strength presented an ascending-descending trend along with the increasing fusion ratio (all P<0.05) , appearing greatest at a ratio of 2∶1 and declining thereafter. The fracture toughness gradually increased from ratios 0∶1 to 2∶1 (all P<0.05) , appearing greatest at a ratio of 2∶1, and subsequently plateaued at ratios of 5∶1 and 1∶0. The fusion ratio showed modest impact on hardness and brittleness of the composite resin, with hardness basically unchanged over all ratios, and brittleness gradually decreasing from ratios 0∶1 to 1∶1 (all P<0.05) until a plateau with higher ratios. Under SEM, the section morphology of the specimens was consistent with mechanical properties.

The optimum fusion ratio of α-Si₃N₄ whiskers and SP₁SiO₂ particles is 2∶1.

Inorganic filler; Composite resin; α-Si₃N₄; SP₁SiO₂; Fusion ratio; Flexural strength; Fracture toughness