Effect of filler content on the profile of released biodegradation products in micro-filled bis-GMA/TEGDMA dental composite resins

This study assesses the effect of the filler content, in a micro-filled composite (0.04 μm), on the liberation of biodegradation products derived from two model composite systems. The materials were based on bis-phenyl glycidyl dimethacrylate (bis-GMA) and triethylenene glycol dimethacrylate (TEGDMA) monomers. The composites were produced using silica filler concentrations of 20 and 40% by weight. Samples were incubated with either cholesterol esterase (CE) or phosphate buffer solutions (PBS) for 8, 16 and 32 days. Products were isolated by high-performance liquid chromatography (HPLC) and identified by mass spectrometry. The identified products included TEGDMA, 2,2-bis[4(2,3-hydroxypropoxy)-phenyl]propane (bis-HPPP) and triethylene glycol methacrylate (TEGMA). Bis-HPPP was only produced in the presence of enzyme. The amount of isolated TEGMA, in both composite systems, was shown to be significantly higher for materials incubated with enzyme than their buffer counterparts (P<0.05). Between 0 and 8 days incubation with enzyme, significantly higher amounts of Bis-HPPP and TEGMA were generated with the lower filler model material (composite-20) than the higher filled composite (composite-40), while the opposite effect was observed between 8 and 16 days. The data indicate that biodegradation product release profiles are dependent on the filler/resin ratios, and suggests that this parameter should be considered when assessing product release for biocompatibility issues pertaining to dental composite systems.