Assessing the Risk of Aerosol Production
I learned during a recent continuing education course that the use of ultrasonic scalers is no longer contraindicated for patients with hepatitis B, hepatitis C, or human immunodeficiency virus (HIV). Per universal precautions, I understand we need to treat all patients as if they have an infectious disease, but what about the fact that aerosols can linger in the operatory for up to 30 minutes after the ultrasonic scaler is used?
The primary route of contracting hepatitis B, hepatitis C, or HIV in the dental office is through exposure to blood, most commonly through percutaneous injuries (eg, needlestick or puncture with a sharp object) or splash to mucous membranes (during lengthy procedures, clinicians should also don a full-length faceshield in addition to a mask for added protection). The general population most commonly contracts these bloodborne pathogens through direct contact with blood or infected bodily fluids, unprotected sex, shared needles, or vertical transmission during labor and delivery. These pathogens are not as easily spread through airborne contact. HIV does not live long outside of the body, so it may not be as infectious in a droplet/airborne state. The transmission of hepatitis B and hepatitis C requires a high volume of viral load, which is probably not contained in the aerosol form. During the use of ultrasonic scalers, airborne/ respiratory diseases—such as tuberculosis, severe acute respiratory syndrome, and Middle East respiratory syndrome—are of much greater concern than bloodborne pathogens. The use of ultrasonic instrumentation is contraindicated for patients with respiratory illness.
Aerosols/droplets can linger for up to 30 minutes in the dental operatory. The droplets evaporate into droplet nuclei, which can become airborne again as dust particles. Well-fitting personal protective equipment and the implementation of standard/universal precautions are always clinicians’ first line of defense. The literature indicates, however, that preprocedural rinsing (ideally with chlorhexidine) and high-volume suction/ evacuation are effective when used alone as well as together in reducing the microbial load of the aerosols produced during ultrasonic scaling.1 High-volume suction has been shown to significantly reduce airborne pathogens up to 98%.2 Stephen K. Harrel, DDS, a professor at Baylor College of Dentistry in Dallas who has written extensively on aerosol production in the dental setting, states that high-volume suction is a “mandatory infection control precaution” when using ultrasonics.2–4
Many of the studies conducted on aerosols in the dental operatory must be carefully examined. Most count organisms that can be cultured on a petri dish (aerobic bacteria), meaning they are nonpathogenic bacteria. Anaerobic bacteria are much more pathogenic and difficult to measure on an agar plate. Also, viruses, including hepatitis B, hepatitis C, and HIV, cannot be cultured in this medium, so the studies using this design method are flawed.
The United States Centers for Disease Control and Prevention Guidelines for Infection Control in Dental Health-Care Settings are currently being updated. Preprocedural rinsing is a topic that will most likely receive a significant update, as extensive research has been conducted on aerosols since the last edition of the guidelines was published in 2003.
- Devker NR, Mohitey J, Vibhute A, et al. A study to evaluate and compare the efficacy of preprocedural mouthrinsing and high volume evacuator attachment alone and in combination in reducing the amount of viable aerosols produced during ultrasonic scaling procedure. J Contemp Dent Pract. 2012;13:681–689.
- Harrel SK. Airborne spread of disease—the implications for dentistry. J Calif Dent Assoc. 2004;32:901–906.
- Harrel SK. Contaminated dental aerosols. Dimensions of Dental Hygiene. 2003;1(6):16–20.
- Harrel SK. Aerosols and spatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc. 2004;135:429–437.