C. Hallier, D. W. Williams, A. J. C. Potts and M. A. O. Lewis British Dental Journal 2010; 209: E14

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Key Points

• Dental procedures create bioaerosols that are a potential vector for transmission of infection in the dental surgery.

• The use of an air cleaning system both before and during dental treatment can reduce the size of bioaerosols and therefore reduce the risk of spread of infection.

• Air cleaning systems may have a useful role to play in the treatment of patients, in particular those who may be immune-compromised.

Background

Bioaerosols are defined as airborne particles of liquid or volatile compounds that contain living organisms or have been released from living organisms. The creation of bioaerosols is a recognized consequence of certain types of dental treatment and represents a potential mechanism for the spread of infection.

Objectives

The aims of the present study were to assess the bioaerosols generated by certain dental procedures and to evaluate the efficiency of a commercially available Air Cleaning System (ACS) designed to reduce bioaerosol levels.

Methods

Bioaerosol sampling was undertaken in the absence of clinical activity (baseline) and also during treatment procedures (cavity preparation using an air rotor, history and oral examination, ultrasonic scaling and tooth extraction under local anaesthesia). For each treatment, bioaerosols were measured for two patient episodes (with and without ACS operation) and between five and nine bioaerosol samples were collected. For baseline measurements, 15 bioaerosol samples were obtained. For bioaerosol sampling, environmental air was drawn on to blood agar plates using a bioaerosol sampling pump placed in a standard position 20 cm from the dental chair. Plates were incubated aerobically at 37°C for 48 hours and resulting growth quantified as colony forming units (cfu/m3). Distinct colony types were identified using standard methods. Results were analysed statistically using SPSS 12 and Wilcoxon signed rank tests.

Results

The ACS resulted in a significant reduction (p = 0.001) in the mean bioaerosols (cfu/m3) of all three clinics compared with baseline measurements. The mean level of bioaerosols recorded during the procedures, with or without the ACS activated respectively, was 23.9 cfu/m3 and 105.1 cfu/m3 (p = 0.02) for cavity preparation, 23.9 cfu/m3 and 62.2 cfu/m3 (p = 0.04) for history and oral examination; 41.9 cfu/m3 and 70.9 cfu/m3 (p = 0.01) for ultrasonic scaling and 9.1 cfu/m3 and 66.1 cfu/m3 (p = 0.01) for extraction. The predominant microorganisms isolated were Staphylococcus species and Micrococcus species.

Conclusion

These findings indicate potentially hazardous bioaerosols created during dental procedures can be significantly reduced using an air cleaning system.

Editor's summary

Infection control in dentistry continues to be a hot topic, and one that is the subject of much investigation: recent papers in this Journal have looked at contamination of photographic retractors1 and water quality in dental unit water lines.2 The requirements of HTM01-05 have focused our attention on cleaning of reusable dental instruments and the associated infection control risks. This article investigates an area that is arguably more difficult to control: the production of bioaerosols during dental treatment.

The authors studied the bioaerosols produced during four different dental procedures (cavity preparation using an air rotor, history taking and examination, ultrasonic scaling and tooth extraction), and the ability of an air cleaning system to reduce their levels. The bioaerosol levels were compared against baseline levels taken in the absence of clinical activity. All the procedures resulted in an increase in levels of bioaerosols, with cavity preparation producing the highest levels found in this study. The air cleaning system was effective in significantly reducing bioaerosol levels, although they were never reduced to the levels found at baseline.

Dentists are already familiar with the concept of bioaerosols. The use of aspiration, masks and eye protection are all aimed at reducing their impact, and the fact that transmission of airborne pathogens in the dental surgery is not a frequently reported problem suggests that they are generally effective – or at least effective enough. The authors acknowledge that an air cleaning system is probably not required in every dental setting, but suggest that it could be useful in certain clinical environments, for example in surgeries treating medically compromised patients. The significance of the article lies in its confirmation that in general, such a system can reduce bioaerosols and provide a safer working environment.

Rowena Milan, Managing Editor

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