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 com posite (0.04 mu m), on the liberation of biodegradation products derived fr om two model composite systems. The materials were based on bis-phenyl glyc idyl dimethacrylate (bis-GMA) and triethylenene glycol dimethacrylate (TEGD MA) monomers. The composites were produced using silica filler concentratio ns 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. Pr oducts were isolated by high-performance liquid chromatography (HPLC) and i dentified by mass spectrometry. The identified products included TEGDMA, 2, 2-bis[4(2,3-hydroxypropoxy)-phenyl]propane (bis-HPPP) and triethylene glyco l methacrylate (TEGMA). Bis-HPPP was only produced in the presence of enzym e. 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, sign ificantly higher amounts of Bis-HPPP and TEGMA were generated with the lowe r filler model material (composite-20) than the higher filled composite (co mposite-40), while the opposite effect was observed between 8 and 16 days. The data indicate that biodegradation product release profiles are dependen t on the filler/resin ratios, and suggests that this parameter should be co nsidered when assessing product release for biocompatibility issues pertain ing to dental composite systems. (C) 1999 Elsevier Science Ltd. All rights reserved.