Preparation and antibacterial properties of Cu-ZnO-loaded dental veneering porcelain

To investigate the antibacterial properties, biocompatibility and mechanical properties of Cu-ZnO-loaded dental veneering porcelain to provide an experimental basis for the development of new dental veneering porcelain.

Cu-ZnO nanoparticles were added to IPS E.max Ceram for restorative veneer porcelain at different mass percentages of 0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, and 6 wt% using ball milling in ceramic powder. A cylindrical specimen with a diameter of 20 mm and a thickness of 2 mm was prepared by high-temperature sintering. Scanning electron microscopy was used to observe the surface morphologies of nano-Cu-ZnO and the specimens. The antibacterial effect of Escherichia coli (E. coli) was quantitatively studied by the plate colony counting method. The CCK-8 method was used to evaluate in vitro the cytotoxicity of the tested piece to mouse fibroblasts (L929). Live and dead cells were observed by fluorescence microscopy. The mechanical properties of modified IPS E. Max Ceram veneering porcelain were tested by a three-point bending strength test.

Under the scanning electron microscope, Cu-ZnO appears with a block-like structure and can be seen dispersed in the veneering porcelain. When the nano Cu-ZnO loading was 1 wt%, 2 wt%, 3 wt%, and 4 wt%, the antibacterial rates of the specimens were 24.85%, 67.94%, 96.92%, and 99.99%, respectively, and the difference between the experimental groups and the control group was statistically significant (F = 23.308,P = 0.001). The relative growth rate of each group was greater than 80% after coculture with mouse fibroblast cells (L929) for 1 day and 3 days, and there was no significant difference between the groups. The morphology of L929 cells was normal after coculture for 24 hours. With the increase in the Cu-ZnO concentration, the flexural strength of the specimen exhibited an increasing trend followed by a decreasing trend. The bending strength of the specimen loaded with 3 wt% nano Cu-ZnO reached the maximum value (84.728 ± 6.82) MPa, and there was no statistically significant difference between groups (F = 0.633,P = 0.702).

The antibacterial rate of IPS E. max Ceram veneering porcelain loaded with 3 wt% nano Cu-ZnO was more than 96% against E. coli after high-temperature sintering at 750 ℃. The bending strength reached the maximum (84.728 ± 6.82) MPa, and there was no obvious cytotoxicity.