This study was performed at the specialist care
unit of the Helsinki City Health Department in
2004e2005. Restorative dentistry fallout samples
(N ¼ 72) were collected from rooms (N ¼ 6) where
high-speed rotating instruments were used, and
control samples (N ¼ 24) were collected from
rooms (N ¼ 4) used for periodontal and orthodontic
treatment where rotating and ultrasonic instruments
were not used. Rooms at rest (N ¼ 3) were
also sampled for background contamination. The
rooms have two-directional forced ventilation
with class F7 filters (installed in 2001). The air
flow is adjusted to 84 L/s in four of the rooms
(high-speed instruments, control, rest) and to
440 L/s in the two larger rooms (high-speed instruments,
control). This results in one air exchange
every 10 min in the slightly smaller rooms and
one air exchange every 5 min in the larger rooms.
The ventilation was not altered during the sampling
period. The ventilation system is checked
and serviced annually. The rooms do not have
air-conditioning units as they are not necessary in
the Finnish climate.