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. 2020 Oct 13;2020(10):CD013686. doi: 10.1002/14651858.CD013686.pub2

4. Comparison 5. Combination system compared to HVE for reduction in the level of contamination in aerosols.

Combination system compared to HVE for reduction in the level of contamination in aerosols
Population: people undergoing aerosol generating procedures
Setting: dental clinic
Intervention: combination system
Comparison: HVE
Outcomes Anticipated absolute effects* (95% CI) Relative effect
(95% CI) Number of sites
(studies) Certainty of the evidence
(GRADE) Comments
Risk with HVE Risk with combination system
Rate of infection of dental staff or patients Not reported
Reduction in volume of contaminated aerosols in the operative environment Not reported
Reduction in level of contamination in aerosols
during water spray using high speed handpiece
The mean CFU level was 117.80 MD 109.30 CFU lower
(153.01 lower to 65.59 lower) 24 ('n of 1' design)
(1 RCT)a ⊕⊝⊝⊝
VERY LOW 1  
*The risk in the intervention group (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CFU: colony forming units; CI: confidence interval; MD: mean difference; RCT: randomized controlled trial
GRADE Working Group grades of evidenceHigh certainty: we are very confident that the true effect lies close to that of the estimate of the effect
Moderate certainty: we are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different
Low certainty: our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect
Very low certainty: we have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect

aFrere 2016

1. Downgraded 2 levels for unclear risk of selection bias and high risk of other bias, and 2 levels for imprecision due to small sample size reported in a single study