Fallow time: 10 minutes ‘appropriate’ for open-plan clinics, suggests study

The cross-infection risk following AGPs in an open-plan clinic is 'small', prompting researchers to suggest a reduction in fallow timeThe cross-infection risk following AGPs in an open-plan clinic is ‘small’ and most particles settle in the first 10 minutes.

This is according to a new study looking into the implications of COVID-19.

The research analysed the splatter and aerosol distribution from an AGP. It also investigated how long it took for aerosol to settle following an AGP in a dental practice.

Using a dental mannequin and fluorescein dye in the irrigation system of a high-speed handpiece, an eight-metre rig was set up to investigate the effect of fallow time.

Dye was also placed in the mannequins mouth using artificial salivary ducts.

Low levels

The results found that the distribution of fluorescein contamination varied across the open plan clinic and was dependent on the conditions:

  • Unmitigated (no suction) treatments had the potential to contaminate at large distances
  • Medium volume dental suction reduced contamination in the AGP bay by 53%. It reduced by 81-83% in adjacent bays and walkways. Low volume suction yielded similar results
  • Cross-ventilation reduced contamination in adjacent bays and walkways by 80-89%
  • In the most realistic model (dye in the mouth with medium volume suction) the samples in distant bays (over five metres head-to-head chair distance) resulted in zero readings or very low readings. Almost all (99.9%) of the aerosol picked up was within the AGP bay.

Small risk

Additionally, time recordings showed that after 10 minutes, very low levels of additional contaminated aerosol settled in the clinic.

The research team concluded that the cross-infection risk appears small, especially when bays are more than five metres apart.

It also suggests a ‘substantial protective effect’ as a result of using dental suction.

Given that the majority of aerosol settled within the first 10 minutes, the team concluded that environmental decontamination and cleaning may be appropriate after this time period.

Dr Richard Holliday is the study’s corresponding author. You can read the full study here.

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