Assessment of Monomer Elution From Bulk-fill Resin-composites Over Time

Objectives: To assess resin composition and eluted monomers from bulk fill resin-composites over a three-month storage period in three different storage media.
Methods: Six bulk fill composites were tested: SureFil SDR (SDR), Venus Bulk Fill (VBF), x-tra base (XB), Filtek Bulk Fill (FBF), Sonic fill (SF), and Tetric EvoCeram Bulk Fill (TEC). For assessment of resin composition, samples of uncured resin-composites were analysed with liquid chromatography/mass spectrometry. For assessment of monomer elution from cured material, cylindrical samples (4x4mm) were prepared using the bulk fill technique (n=5). Immediately after cure, the samples were immersed in water, 70% ethanol/water solution (70% E/W), and artificial saliva (AS). Samples were stored at 37°C for periods of 24h, 1 month, and 3 months and the storage solutions were then analysed with high pressure liquid chromatography. Data were analysed with repeated measures ANOVA, one-way ANOVA, and Tukey HSD post hoc test at α=0.05.
Results: All materials contained UDMA except SF. FBF, TEC, and SF contained BisGMA. BISEMA was present in all materials except TEC. TEGDMA was present in all materials and DEGDMA was only identified in XB. All constituent monomers eluted from cured samples stored in 70% E/W. In water and AS, only TEGDMA and UDMA were detected in significantly lower amounts than those detected in 70%E/W. Monomer elution decreased with time except UDMA that continued to elute in similar amounts in AS until three months. XB and SF showed no eluted monomers in both water and artificial saliva during all storage periods. SF showed significantly lower amount of BisGMA and BisEMA release than all materials.
Conclusions: Within three-month storage period, SF showed the highest stability in all media. The stability of UDMA based composites may be compromised by the continuous release of UDMA in AS. BisGMA and BisEMA based systems shows more hydrophobic behaviour and stability than UDMA based materials.