Search

To investigate the effects of 3-aminopropyltriethoxysilane (APTES)- or (3-mercaptopropyl)trimethoxysilane (MPTS)-conditioned nanozirconia fillers on the mechanical properties of Bis-GMA-based resin composites. The conditioned fillers were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermodynamic calculations. They were then used to prepare Bis-GMA-based resin composites, whose flexural strength and elastic modulus were evaluated. The Cell Counting Kit-8 (CCK-8) assessed the composites' cytotoxicity. The FTIR spectra of the conditioned fillers showed new absorption bands at 1569 and 1100 cm-1, indicating successful grafting of APTES or MPTS onto nanozirconia. XPS confirmed the Zr-O-Si bonds in the APTES- or MPTS-conditioned fillers at contents of 2.02 and 6.98%, respectively. Thermodynamic calculations reaffirmed the chemical binding between the two silanes and nanozirconia fillers. Composites containing the conditioned nanozirconia fillers had significantly greater flexural strengths (APTES, 121.02 ± 8.31 MPa; MPTS, 132.80 ± 15.80 MPa; control, 94.84 ± 9.28 MPa) and elastic moduli (8.76 ± 0.52, 9.24 ± 0.60, and 7.44 ± 0.83 GPa, respectively) than a control with untreated fillers. The cytotoxicity assay identified no significant cytotoxicity by composites containing the conditioned fillers. Silanes were previously considered to be unable to chemically condition zirconia to bond with resin. Inclusion of APTES- or MPTS-conditioned nanozirconia fillers can improve the mechanical properties of Bis-GMA-based resin composites without obvious cytotoxicity in this study.

Poor osteogenesis caused by limited bioactivity is one of the challenges affecting the use of zirconia-based materials as implants. In this study, four representative silanes with different end groups [γ-methacryloxypropyltrimethoxysilane (γ-MPS, with a vinyl end group), methyltrimethoxysilane (MTMS, methyl end), 3-mercaptopropyltrimethoxysilane (MPTS, mercapto end), and 3-aminopropyltriethoxysilane (APTES, amino end)] were grafted on a Y-TZP surface with the purpose of improving its osteogenic activity. Thermodynamic and analytical chemistry results confirmed that the terminal alkoxy groups of the silanes could condense with the hydroxyl groups on the zirconia surface to form covalent Zr–O–Si bonds; in particular, mercapto- terminated silanes were more effective at combining with zirconia than hydrophobic vinyl- and methyl-terminated silanes. Y-TZP modified with mercapto- and amino-terminated silanes showed improved hydrophilicity, which in turn promoted cell adhesion and growth. In vitro cell experiments showed that mercapto- and amino-terminated silanes promoted osteogenic differentiation and mineralization by increasing osteocalcin (OCN) and osterix (OSX) expression levels, while vinyl- and methyl-terminal silanes exhibited inhibitory effects on the collagen type 1 (COL-1), Runt-related transcription factor 2 (Runx2), and OCN expressions. Therefore, grafting mercapto- and amino-terminal silanes is a simple and effective strategy for enhancing the osteogenic potential of Y-TZP implants.