Monomer Release From Nanofilled and Microhybrid Dental Composites After Bleaching

Objective: the aim of this study was to assess the effect of bleaching on elution of monomers from nanofilled and microhybrid composites.materials and methods: 80 samples (5mm diameter and 3mm thickness) of each composite were prepared. after curing, half of them were randomly polished. each group was divided into 8 subgroups and immersed in water or 10%, 20% and 30% h2o2 for 3 or 8 hours. eluted bis-gma (bis-phenol a glycidyl dimethacrylate), tegdma (triethyleneglycol dimethacrylate), udma (urethane dimethacrylate) and bisema (bis-phenol a ethoxylate dimethacrylate) were quantified by high per-formance liquid chromatography and the results were analyzed by univariate anova and t-test (p<0.05).results: bleach significantly increased the overall release of monomers (p<0.001); tegdma was released more than bis-gma (p<0.001). supreme released more tegdma compared to z250 (p<0.001). bleaching increased the release of this mo-nomer (p<0.001). increasing both the concentration of h2o2, and the immersion time, increased the release of tegdma (p<0.001). polishing had no effect on release of this monomer (p=0.952). supreme released more bis-gma than z250 (p=0.000). the more concentrated h2o2 caused more elution of bis-gma (p= 0.003); while the effect of immersion time was not significant (p=0.824). polishing increased the re-lease of bis-gma (p=0.001). neither the type of composite nor bleaching had any effect on release of udma (p=0.972) and (p=0.811) respectively. immersion dura-tion increased the release of udma (p=0.002), as well as polishing (p=0.024).conclusion: bleaching increased the release of monomers. nanofilled composites re-leased more monomer than the microfilled.