Purpose To investigate mechanical properties of experimental resin composites containing 8-methacryloxyoctyltrimethoxysilane (MOS) and a more commonly used silane monomer, 3-methacryloxypropyltrimethoxysilane (MPS).

Materials and methods MOS and MPS were hydrolysed in 95vol% ethanol solution at pH 4 for 1 h before silanisation of SiO2-based bioactive glass powder fillers (o1.0 mu m, Schott, Germany) at 3, 6, 9 and 12wt% of silane. After drying in a vacuum oven (80 degrees C, 5 kPa, 2 h) they were mixed with a monomer mixture of urethane dimethacrylate and triethylene glycol dimethacrylate in a 70:30 weight ratio, camphoroquinone 0.7wt% and 2-(dimethylamino)ethyl methacrylate 0.7wt% to produce eight experimental groups of resin composites with a filler load of 72.7wt%. After photo-polymerisation for 25 min and post-curing at room temperature (24 h), uniform rectangular beams were cut out for the three-point bending test (2 mmx2 mmx25 mm, n = 8). The surface Vickers microhardness (VH) test (press-load 2.94 N for 10s, n = 6) was performed before observation under 3-D optical microscopy. Statistical analysis was performed using ANOVA followed by the Tukey post hoc test (p < 0.05).

Results ANOVA revealed that both the silane type and concentration significantly affected flexural modulus (p < 0.001), flexural strength (p = 0.001) and microhardness (p < 0.001). Resin composites containing MOS exhibited lower flexural modulus but higher strength at a lower concentration than MPS. MOS resin composites exhibited lower surface microhardness than MPS with the corresponding silane content.

Conclusion 8-Methacryloxyoctyltrimethoxysilane may confer different mechanical properties in resin composites compared to 3-methacryloxypropyltrimethoxysilane at the same concentration. Surface microhardness is reduced with 8-methacryloxyoctyltrimethoxysilane.