Effect of silanization of barium-glass-fillers on an experimental bis-GMA-TEGDMA composite

Objectives: Biomechanical properties of an experimental (bis-GMA-TEGDMA) composite with fillers silanized with four organofunctional silane coupling agent monomers and their blends with a non-functional cross-linking silane, were evaluated by using 3-point bending testing.  

Methods: BaSiO2-fillers (average diameter 0.7 µm) were silanized in toluene with 1% 3-acryloyloxypropyltrimethoxysilane (ACPS; Toray Dow Corning), 3-methacryloyloxypropyltrimethoxysilane (MPS; Dow Corning), styrylethyltrimethoxysilane (STYRX; ABCR), 3-isocyanatopropyltriethoxysilane (ISC; ABCR) and their blends with 1% (1,2-bis(triethoxysilyl)ethane (BTSE, ABCR). Composites were prepared by mixing 5.0 g of silanized filler with 2.0 g of the resin matrix (60wt% bis-GMA, 40wt% TEGDMA) with a high speed mixer. Specimens (2mmx2mmx25mm) were photopolymerized, fabricated and tested (3-point bending; ISO 10477). The degree of conversion was measured by using Fourier Transform Infra Red spectroscopy FTIR method. Water sorption in weight% was also measured (dry,1,2,3,5,7,14,21,30 days). Specimens (n=8) were load-tested after 30 days in water storage (37.0 ºC, distilled water).

Results: Statistical analysis (ANOVA) showed that the highest 3-point bending strength after the water storage was obtained with using for silanization MPS (83.2 MPa, SD 23.7 MPa) or STYRX (83.1, SD 11.9) and the lowest result with ISC+BTSE (28.9, SD 8.8), respectively. The highest water sorption was attributed to ISC and the lowest to ACPS+BTSE or MPS+BTSE.

The functionality (type of silane monomer) of silanes (p<0.05) affected significantly and addition of the cross-linking silane (p>0.05) did not affect significantly the 3-point bending strength.

Conclusion: Careful selection of the functional silane monomer in developing novel dental composites with improved biomechanical properties can be significant.