Leachable monomers induce the Carfilzomib production of intracellular reactive oxidative species (ROS) that can be generated in both healthy and diseased tissues.19,20 ROS production has been described by several investigators as an early expression of cellular stress in dental monomer cytotoxicity.20 Mohsen et al21 found that the cell viability in vitro with either untreated or polished composites correlated with the curing time of the composites by visible light and post-curing time (aging) with heat for ensuring polymerization. They also attributed the increase in the biocompatibility of the polished specimens to the removal of the oxygen-inhibited layer. The oxygen-inhibited layers allow for un-reacted double bonds at the surfaces rendering a material toxic, even with long periods of light curing.

In healthy cells, ROS can be produced by the incomplete reduction of oxygen during catabolism. The disruption of important macromolecules through free radical reactions within host cells may hamper cellular functions or may even lead to early cell death. ROS have been shown to cause disruption at multiple cellular sites, resulting in lipid peroxidation, protein oxidation and nucleic acid damage. ROS may induce cell damage directly, or act as intracellular messenger during cell death induced by various other kinds of stimuli.19 Ratanasathien et al22 assessed the cytotoxicity of the dentin- bonding components in cell cultures and found that the ranking by toxicity was: Bis-GMA>UDMA>TEGDMA>HEMA (least toxic) after 24 and 72 hours of exposure. In the same study, it was demonstrated that 0.

00360 mmol L?1 of HEMA reduced the cell metabolism by 50% after 24 h of exposure, whilst Hanks et al2 reported that 16 mmol L?1 of HEMA caused an irreversible inhibitory effect when applied to the cells in culture. HEMA is a common ingredient of dental adhesives to enhance the bond strength to dentin and is present in all adhesives evaluated in the present study (Table 1). Although HEMA was found to be less cytotoxic than the other monomers, its low molecular weight (130.14) and high solubility may result in a greater diffusion of unpolymerized HEMA through dentin. Our results concerning Gluma Comfort bond are in agreement with previous findings.1,11 Hanks et al1 examined the nature and levels of metabolic cytotoxicity of the Gluma, Scotchbond 2, glutaraldehyde and HEMA in monolayer cultures and found that glutaraldehyde was much more cytotoxic than HEMA.

Admira bond uses the so-called ��ormocer�� product, ceramic polysiloxane (silicon-oxygen chains). There have been no published studies on the cytotoxicity of Admira Bond. However, it has been reported that the ormocer restorative material, Admira, was more cytotoxic than two other conventional Dacomitinib dimethacrylate composite resins tested.23 ED Primer II and Clearfil Liner Bond 2V contain the same phosphate monomer (10-MDP), but the former proved to be significantly more cytotoxic.