Effect of Long-Chain Silane on Mechanical Properties of Experimental Resin-Composite

Abstract

Objectives: The objective is to investigate the mechanical properties of experimental resin composite containing fillers treated with a long chain length silane, 8-methacryloxyoctyltrimethoxysilane (8-MOS; Shin-Etsu, Japan) and comparing them to conventionally used 3-methacryloxypropyltrimethoxysilane (3-MPS; Sigma-Aldrich). Methods: Eight groups of composites were prepared using 3, 6, 9 and 12wt% concentrations of the two silanes. They were first hydrolysed in 95vol% ethanol and 5vol% deionised water mixture at pH4 for 1h. Glass powder fillers (Ø1.0μm, Schott, Germany) were then silanised with the silanes and dried in a vacuum oven (80°C, 50mbar, 2h). Monomer mixture (UDMA:TEGDMA at 70:30 weight ratio, camphorquinone 0.7wt%, 2-(dimethylamino)ethyl methacrylate 0.7wt%) was mixed with the two silanised fillers to produce resin composites. The filler load was 72.7wt%. Resin composites were light-cured in curing device for 25min and left for post curing at RT (24h). Specimens of size 2mm×2mm×25mm were made for the three-point bending test (n=8). Surface microhardness (VHN) test (press-load 2.94N for 10s; Duramin 5, Struers) was performed for the polymer matrix. Specimens were then observed under 3D-optical-microscopy. Statistical analysis was carried out using ANOVA followed with Tukey post hoc test (p<0.05). Results: ANOVA revealed that both factors (silane and concentration) had significant effect (p<0.05) on mechanical values. The composites of fillers treated with 3-MPS group exhibited a higher flexural modulus than the specimens of 8-MOS group. Young’s modulus decreased with by lowering the silane concentration of both silane types. 3-MPS at 9wt% and 8-MOS at 6wt% displayed the highest flexural strength. For microhardness, 3-MPS exhibited higher values than corresponding 8-MOS concentrations. Conclusions: Two silanes with different chain lengths which were used to silinise fillers provided similar flexural modulus of resin composites at their respective concentrations. A longer-chain silane might provide higher flexural strength for the resin composite.