DIV/CED/2011 location:Theoretical Building of the Semmelweis University date:03-09-2011
Today's composites may contain high amounts of nanofillers. Objectives: To characterize composite dust to determine whether possibly hazardous respirable (< 5 µm) dust particles may be released upon grinding or polishing composites. We hypothesized that upon grinding/polishing, the filler particles would remain well embedded in the resin matrix and that no respirable dust would be released. Methods: Standardized blocks of polymerized composite were ground with a diamond bur; and dust was collected on 1-µm pore-size filters and weighed. The released dust was also quantified and ultra-morphologically characterized by transmission electron microscopy. Both (microfilled) hybrid composites (Z100, 3M ESPE; Gradia Anterior, GC), and (hybrid-)nanocomposites (Filtek Supreme, 3M ESPE; Tetric EvoCeram, Ivoclar, Vivadent; CeramX, Dentsply; Premise, Kerr; Herculite XRV Ultra, Kerr) were tested. Results: Gravimetrical analysis revealed that all composites released appreciable amounts of respirable dust, with air concentrations from 7-32 mg/m3 immediately after grinding the composites. In addition, electron microscopic analysis revealed that composites may also release high amounts of particles smaller than 1 µm and even 100 nm. The ratio of dust particles smaller than 1 µm to those larger than 1 µm ranged between 3:1 to 9:1. The respirable fraction of the composite dust most often consisted of multiple fillers in the resin matrix, but also of single nanofillers. Conclusion: Contemporary composites may release small respirable dust particles. Dentists should be urged to always wear protective masks, and to use water coolant during the polishing or removal of composites. However, more research is necessary to determine possible health hazards of the released composite dust.