Abstract: BACKGROUND: Boron nitride nanosheets have demonstrated remarkable advantages in enhancing the properties of dental materials. However, the current research on boron nitride nanosheets-reinforced resin-matrix ceramic materials is still in the preliminary exploration stage.
OBJECTIVE: To investigate the effect of boron nitride nanosheet addition on the properties of resin-matrix ceramics.
METHODS: 60% bisphenol A glycidyl methacrylate and 40% triethylene glycol dimethacrylate were used as the resin matrix, and barium glass powder was used as the inorganic filler. Resin-matrix ceramics were prepared by mixing 83% (mass fraction) of the resin matrix with 17% (mass fraction) of the barium glass powder. Meanwhile, boron nitride nanosheets were added to replace the barium glass powder at mass fractions of 0.3%, 0.5%, 0.7%, and 0.9% to prepare 0.3%, 0.5%, 0.7%, and 0.9% (mass fractions) of boron nitride nanosheet/resin-matrix ceramics, respectively. Resin-matrix ceramics were co-cultured with extracts of 0.3%, 0.5%, 0.7%, and 0.9% boron nitride nanosheets/resin-matrix ceramics, respectively, and mouse fibroblast L929 cells (or human umbilical vein endothelial cells). The CCK-8 assay was used to assess cell viability, and L929 cell viability was assessed using live/dead staining. The wettability, mechanical properties, and wear resistance of the resin-matrix ceramics and extracts of 0.3%, 0.5%, 0.7%, and 0.9% boron nitride nanosheets/resin-matrix ceramics were evaluated.
RESULTS AND CONCLUSION: (1) After co-culture with the resin-matrix ceramics and extracts of 0.3%, 0.5%, 0.7%, and 0.9% boron nitride nanosheets/resin-matrix ceramics, the survival rates of both L929 and human umbilical vein endothelial cells exceeded 85%, with no significant cytotoxicity. Live/dead staining revealed that the resin-matrix ceramics and extracts of 0.3%, 0.5%, 0.7%, and 0.9% boron nitride nanosheets/resin-matrix ceramics did not affect L929 cell viability. (2) With increasing boron nitride nanosheet mass fraction, the water contact angle of the resin-matrix ceramic increased, while the flexural strength and microhardness first increased and then decreased. The 0.5% boron nitride nanosheet/resin-matrix ceramic exhibited the highest flexural strength and microhardness. After 60 000 cycles, the wear depth and wear volume of the resin-matrix ceramic gradually increased with increasing boron nitride nanosheet mass fraction. After 120 000 cycles, the wear depth and wear volume of the resin-matrix ceramic first decreased and then increased with increasing boron nitride nanosheet mass fraction. These results indicate that the appropriate addition of boron nitride nanosheets can significantly improve the overall properties of resin-matrix ceramics.

Key words: boron nitride nanosheet, resin-matrix ceramics, cytotoxicity, contact angle, mechanical property, wear property, ball milling method;, warm isostatic pressing method