Table 1.

Level of bioaerosol at baseline and during four dental procedures with and without an air cleaning system (ACS) activated

Location	Procedure	Mean bacterial count at baseline cfu/m3		Mean bacterial count during procedure cfu/m3
		ACS off	ACS on	ACS off	ACS on
Clinic 1	No procedure Cavity preparation History and examination	23.9	5.6*	105.1** 69.2**	38.4*** 59.8
Clinic 2	No procedure Ultrasonic scaling	41.9	5.3*	70.9**	38.5***
Clinic 3	No procedure Tooth extraction	9.1	2.5*	66.1**	37.0***

cfu/m³ = colony forming units per cubic metre

^*significant (P=0.01) decrease in baseline bacterial counts with ACS on

^**significant (P<0.05) increase in bacterial counts for procedures compared with baseline (ACS off)

^***significant (P<0.05) decrease in bacterial counts for procedures with ACS on compared with ACS off