Hallier 2010.

Study characteristics
Methods	Trial design: CCT, split‐mouth design Location: School of Dentistry, Cardiff University, Heath Park, Cardiff, UK Setting: 3 dental clinics in the university ‐ clinic 1 and 2 ‐ large open multi‐chair clinical areas, clinic 3 ‐ single‐chair room Language: English Number of centres: 1 Study period: not mentioned Funding source: not mentioned Study protocol: not available
Participants	Age: not mentioned Total number of participants: 8 (2 participants for each treatment episode, thereby allowing comparison of bioaerosols with and without the ACS in operation) Inclusion and exclusion criteria: not mentioned Number randomized: not available Number evaluated (withdrawals/missing participants): 8 (none)
Interventions	Comparison: air cleaning system versus no air cleaning system Intervention: Group name: with IQAir Flex Vac™ Air Cleaning System in operation. The air cleaning system is a general air filtering system consisting of High Efficiency Particulate Air (HEPA) pre‐filters, which retain particles less than 0.3 μm in size (which includes bacteria and many types of virus), a second filtration stage involves 4 cylinder gas filter cartridges, which remove mercury vapour, formaldehyde, glutaraldehyde and odours, and a final filtration stage comprises an electrostatically charged post‐filter. Number of intervention groups: 1 Number randomized to intervention group: not available Description of intervention: the study involved 8 participants (2 participants for each treatment episode, thereby allowing comparison of bioaerosols with and without the ACS in operation) treated by 8 dental students in an attempt to minimize participant and operator bias. Sampling was undertaken in the same dental units in each of the 3 clinics at baseline and during the 4 procedures. The ACS and sampling pump were placed in the same position throughout the study. The blood agar plates were replaced every 10 minutes in the sampling pump during the course of each treatment procedure. Each dental procedure tested was performed on different days. In the intervention group, the IQAir Air Cleaning System (ACS) was activated 1 hour before samples were taken and was operated continuously at 500 m³/hour. History and oral examination, using a standard probe and a mirror, were assessed in Clinic 1. The same clinic was used for the assessment of participants undergoing cavity preparation using a high‐speed dental handpiece. Ultrasonic scaling, in conjunction with high‐volume aspiration (HVA), was assessed in Clinic 2, while tooth extraction under local anaesthesia was assessed in Clinic 3. All baseline and procedure sampling were performed with the clinic windows closed and no air conditioning systems or fans on. The room temperature in all 3 clinical areas was between 21 °C and 24 °C. Any co‐interventions: no Comparator: Group name: without IQAir Flex Vac™ Air Cleaning System in operation Number of control groups: 1 Number randomized: not reported Description of control: same as above without the ACS in operation
Outcomes	Outcome name: mean bacterial count with and without ACS Outcome measurement: CFU/m³ with an air pump connected to a Petri dish (Buck Bio‐Culture™ (Model B30120; A. P. Buck, Inc) Effect estimate: mean (SD not given) Key conclusions: "the results of the present study also provide the first evidence that an ACS can significantly reduce the bioaerosol load during dental procedures. However, on no occasion was the level reduced to that encountered at baseline. Regardless of this, it can be concluded here that the IQ Air Flex Vac™ ACS was efficient at reducing the mean bacterial aerosols within a dental clinic."
Notes	Study authors were contacted for: random sequence generation, allocation concealment, blinding, number randomised, age of participants, SD and study protocol. E‐mail sent on 26 July 2020 and we are yet to receive any response from the contact author.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	1 participant was allocated to the group with the ventilation system on and another side of the same participant was treated with the system off.
Allocation concealment (selection bias)	High risk	No details given
Blinding of participants and personnel (performance bias) All outcomes	Low risk	No details available for participant blinding. However, personnel blinding was not possible and neither of them will be able to alter their behaviour even if they knew the intervention received.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	It is not clear if the CFU were manually counted or any automated colony counters were used ‐ there is subjectivity if manually counted.
Incomplete outcome data (attrition bias) All outcomes	Low risk	No dropouts.
Selective reporting (reporting bias)	Unclear risk	We are not sure of reporting selective outcomes as there is no protocol available.
Other bias	Low risk	Quote: "Each dental procedure tested was performed on different days." This ensured adequate washout period.