The Japanese Journal of Medical Instrumentation. Vol. 84, No. 5 (2014)

Airborne Contamination in the Dental Operating Room
＊Kaoru Tamazawa , Yoshinori Tamazawa＊１＊, ＊１, Hidetoshi Shimauchi

Abstract
The purpose of this study is to assess airborne contamination of the dental operating room (DOR) inorder to evaluate the risk of infection for the patients and dental staff. To examine DOR, a total of 744
air samples (0.01 Cubic Feet) collected in the particle counter hourly in 24 times a day for 31 days wasused. Further, we investigated the change in the particle during tooth preparation (TP) with a highspeed hand-piece when using or not suction device.
The results were as follows:1)In almost all time from 9:00 to 17:00, the number of 1.0μm, 2.0μm and 5.0μm particles in thetreatment days (20 days), were significantly (Welch’s t-test, p<0.05) greater than the closing office day(11 days).
2)The particle of 0.3μm, 0.5μm, 1.0μm, 2.0μm and 5.0μm during TP as compared to before TP,
increased by 7.5 times, 50.0 times, 158.9 times, 144.6 times and 47.7 times, respectively. When using
the intra-oral suction(IOS), these particles were remarkably reduced. When using the IOS and theextra-oral suction (EOS), 2.0μm and 5.0μm particles were further reduced to the level before TP, andwere significantly (paired t-test, p<0.05) reduced compared to IOS alone.

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

1 Purpose:
This study is to assess airborne contamination of the dental
operating room (DOR) in order to evaluate the risk of infection
for the patients and dental staff.
The study includes theparticle number in the air samples with each particle diameterin every hours, and the aerosol particle number in the air
samples during tooth preparation with by air-turbine handpiece.

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

2 Materials and Methods:
To examine DOR, a total of 744 air samples (0.01 Cubic Feet)collected in the Particle Counter (RION Co. Ltd.; KC-01C type; aircollection flow rate: 500mL/min) hourly in 24 times a day for 31days was used. The particle in the air samples was classified in fivedifferent diameter size as 0.3μm, 0.5μm, 1.0μm, 2.0μm and 5.0μmand larger(>=5.0μm). The air samples was collected in thetreatment days (Monday to Friday; 20 days) and also in the closing
office days (Saturday and Sunday; 11 days).
Further, we investigated the change in the particle during toothpreparation (TP) with a high-speed air-turbine hand-piece (OsadaElectric Co. Ltd.; Smily-fine GM S221LL Type); when using threedifferent types of suctioning conditions of saliva ejector alone,saliva ejector + intra-oral suction (IOS), and saliva ejector + IOS +extra-oral suction (EOS)(Free-Arm 12S (Tokyo Giken Inc.).
Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japansaliva ejector

saliva ejector

saliva ejector
Intra-oralsuction (IOS)

Condition A

Extra-oralsuction (EOS)

Condition B

Intra-oralsuction (IOS)

air turbine
hand-piece

PC suction
tube

Condition C

Condition A : saliva ejector alone
Condition B : saliva ejector + intra-oral suction (IOS)
Condition C : saliva ejector + intra-oral suction (IOS) + extra-oral suction (EOS)
Figure 1 Three types of condition of suction devices during tooth preparation
Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

3 Results:1) The aerosol particle umber in the air samples in DOR (Fig.2, Tab. 1)• Treatment days showed more number of particles than closing office days
• Statistically significant differences were found in 14:00 and 15:00 hours in
0.3μm, >=0.5μm particles between treatment and closing days
• The differences were significant in 10:00 ～ 16:00 hours in 1.0μm particle• The number of 2.0μm particle showed difference I every 9 hours• The >=5.0μm particle showed significant difference in 9:00～ 16:00 hours(Fig. 2)• The mean particle number of 9 hours of treatment days and closing officedays is listed on Table 1, which indicates the particle number was 1.7-, 3.6-,
15.5-hold greater in 1.0μm, 2.0μm and >=5.0μm, respectively in treatmentdays than in closing office days
• The difference became much bigger with increase of the particle diameter(Tab. 1)

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Particle number

0.3 µmparticlehour

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Particle number

0.5 µmparticlehour

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Closing office days
Treatment days

Particle number

1.0 µmparticlehour

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Particle number

2.0 µmparticlehour

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Particle number

5.0 µmparticlehour

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Figure 2 Hourly changes of the particle number in air samples
in the treatment days and the closing office days of the dental
operating room(the treatment days: 20 days, the closing office days: 11 days; 9:00～
17：00 every hour, mean ±SD)
* ： P <0.05（Welch’s t-test）**：P<0.01（Welch’s t-test）

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Table 1 The particle number of air samples in the treatment days and theclosing office days (9:00～17：00 hour, mean ± SD)

0.3μm粒子
0.5μm粒子
1.0μm粒子
2.0μm粒子
5.0μm粒子

unit: particle number

Treatment days

Closing office days

mean ±SDmean ±SD

23815.0±16715.0
2000.9±1822.6
185.5±121.7
119.1±63.8
15.5±12.5

16683.0±8274.0
1344.0±597.0
108.2±36.4
33.0±13.8
1.0±1.2＊ ：P＜0.05 (Welch’s t-test)＊＊： P＜0.01 (Welch’s t-test)

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan＊＊＊＊＊

3 Results:2) The particle number in the air samples during tooth preparation(Changes with three different types of suctioning conditions)(Fig. 3)• Condition A: saliva ejector alone
The particle number showed 7.5-, 50.0-, 158.9-, 144.6-, 47.7-hold increased with
0.3μm, 0.5μm, 1.0μm, 2.0μm and >= 5.0μm, respectively than before preparation.
Air contamination by aerosol particles during tooth preparation can be high withthis condition.
• Condition B : saliva ejector + intra-oral suction (IOS)
The particle number showed 2.2-, 4.8-, 8.5-, 4.7-, 1.3-hold increased with 0.3μm,0.5μm, 1.0μm, 2.0μm and >=5.0μm, respectively than before preparation. The
aerosol particle decreased much in compared with condition A.
• Condition C : saliva ejector + intra-oral suction(IOS) + extra-oral suction (EOS)The particle number showed 1.6-, 1.9-, 2.2-, 1.1-, 0.1-hold increased with 0.3μm,0.5μm, 1.0μm, 2.0μm and >=5.0μm, respectively than before preparation.
Significantly higher suctioning effect was found in 2.0μm and >=5.0μm particles
than condition B. (Fig.3)
Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

Particle number

Condition A : saliva ejector alone
Condition B : saliva ejector + intra-oral suction(IOS)
Condition C : saliva ejector + intra-oral suction(IOS) + extra-oral suction (EOS)*: P< 0.05 (paired t-test)
Beforepreparation

Condition
ACondition
BCondition
CFigure 3 The particle number in the air samples during tooth preparation

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

4 Discussion:1） The aerosol particle umber in the air samples in DOR (Fig.2, Tab. 1)• The particle counter (PC) used in this study consists of 0.01 Cubic Feet with
34 seconds in sampling time, which can be considered suitable for counting
aerosol particles in the air samples and samples during tooth preparation.
• The air samples in the treatment days showed significantly increased
number of particles with >= 1.0 μm in diameter than the closing office daysas the characteristic of DOR.
• The prevention of airborne contamination in DOR will be to reduce thenumber of particles with >= 1.0 μm in the treatment days close to the levelof the closing office days.

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

4 Discussion:2) The particle number in the air samples during tooth preparation(Changes with three different types of suctioning conditions)(Fig. 3)• During tooth preparation under Condition A (saliva ejector alone) theparticle number very much increased than before preparation.
• In Condition B (saliva ejector + IOS) the reduction of the particle number inevery size was observed compared with Condition A.
• By further adding EOS in Condition C (saliva ejector + IOS + EOS) the particle
number showed much decreased to almost same level with before
preparation in 2.0μm and 1/10 in >=5.0μm.
• The activity of IOS and EOS will depend on its flow rate. By measuring theflow rate the saliva ejector had 0.0004 m2/min, IOS 0.1571 m2/min, and EOS
3.5671 m2/min, then showing 1: 392: 8918 in ratio. EOS was 23X stronger
than IOS.
• By adding EOS it was evident with the reduction of larger size of aerosol
particles (2.0μm and >=5.0μm), although the effect to minor particles (like0.3μm and 0.5μm) was slight.
Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan

5 Conclusion:
The present investigation on the aerosol particle number in the air samples inDOR revealed that treatment days showed significantly increased number ofparticles with 1.0μm and larger(>= 1.0μm) in diameter than closing office days.
The difference became much bigger with increase of the particle diameter.
The aerosol particle number in the air samples during tooth preparationmuch decreased by using IOS and EOS. The usage of EOS significantly reduced
the number of large size of aerosol particles (2.0μm and >=5.0μm) whencompared without EOS.

Translation courtesy of Professor Takashi Fujibayashi, DDS, PhD of Tokyo, Japan