Assessment of Potential Silica Exposure During Finishing of Dental Restorative

Objectives: When composite fillings are placed, finishing steps like bur contouring, rubber point polishing, and brushing are applied to achieve good fit and a smooth surface of the restoration. These finishing steps can create and release particles into the room air. The objective of this investigation was to determine respirable crystalline silica concentration in air when finishing restorations with 3M™ ESPE™ Low Shrink Posterior Restorative.

Methods: Two simulated use studies were conducted using a dental manikin as patient surrogate.

- All dry finishing, no suction (worst case)

- Wet and dry finishing with suction (realistic)

Eight restorations were placed for each set of experiments. Air samples for respirable crystalline silica were taken on PVC filters and analyzed by an accredited laboratory. A direct reading dust monitor was used to continuously measure respirable particulate concentration in front of the manikin and recorded these concentrations over time.

Results: Direct reading particulate concentrations were significantly higher (p<0.01) during dry finishing (0.061±0.023 mg/m3) versus wet finishing (0.038±0.016 mg/m3). Only one filter sample (taken on the dentist during dry finishing method) showed a detectable concentration of crystalline silica (0.013 mg/m3). During wet finishing, no sample showed any detectable concentrations of crystalline silica.

Conclusion: Since the only measurable crystalline silica exposure occurred during purely dry finishing without intra-oral suction (which is not the method realistically applied to composite fillings), this sample was considered worst-case scenario. The exposure to crystalline silica did not exceed the occupational exposure limit (TLV ® 0.025mg/m3 TWA, respirable fraction). Based on the overall study results, it is not expected that the occupational exposure limit for crystalline silica is exceeded during the intended use of this restorative material.