Cytotoxic effects of composite dust on human bronchial epithelial cells

IntroductionPrevious research revealed that during routine abrasive procedures like polishing, shaping or removing of composites, high amounts of respirable dust particles (<5 μm) including nano-sized particles (<100 nm) may be released.ObjectiveTo determine the cytotoxic potential of composite dust particles on bronchial epithelium cells.MethodsComposite dust of five commercial composites (one nano-composite, two nano-hybrid and two hybrid composites) was generated following a clinically relevant protocol. Polymerized composite samples were cut with a rough diamond bur (grain size 100 μm, speed 200,000 rpm) and all composite dust was collected in a sterile chamber. Human bronchial epithelial cells (16HBE14o-) were exposed to serially diluted suspensions of composite dust in cell culture medium at concentrations between 1.1 and 3.3 mg/ml. After 24 h-exposure, cell viability and membrane integrity were assessed by the WST-1 and the LDH leakage assay, respectively. The release of IL-1β and IL-6 was evaluated. The composite dust particles were characterized by transmission electron microscopy and by dynamic and electrophoretic light scattering.ResultsNeither membrane damage nor release of IL-1β was detected over the complete concentration range. However, metabolic activity gradually declined for concentrations higher than 660 μg/ml and the release of IL-6 was reduced when cells were exposed to the highest concentrations of dust.SignificanceComposite dust prepared by conventional dental abrasion methods only affected human bronchial epithelial cells in very high concentrations.