Should we be concerned about composite (nano-)dust?

Dental personnel often come into contact with composite dust upon polishing or grinding composites. Contemporary composites typically contain high amounts of (silica) nano-filler, but so far it has never been investigated whether composite dust may be hazardous. Objectives: The objectives of this study were (1) to characterize composite dust in vitro and (2) to assess the clinical exposure. Methods: Polymerized blocks of contemporary composites were ground with a diamond bur according to a clinically relevant protocol, and aerosolized dust was collected on 1-μm pore-size filters and gravimetrically quantified. In addition, the dust was characterized by transmission electron microscopy. Respirable dust was quantified with a mass particle counter in a dental operatory. Results: All composites released respirable dust (<5 μm) in vitro. These observations were corroborated by the clinical measurements; however only short episodes of high concentrations of respirable dust upon polishing composites could be observed. Electron microscopic analysis showed that the size of the dust varied widely with particles larger than 10 μm, but submicron and even nano-sized particles could also be observed. The dust particles often consisted of multiple filler particles contained in resin, but single nano-filler particles could also frequently be distinguished. Significance: This study showed that inhalation of composite dust is better avoided. Therefore, it is recommended to always use water-cooling upon polishing or removing composites, to use good aspiration, to frequently ventilate the dental operatory and to wear masks with high particle-filtration efficiency for small particle sizes.