Reducing the Risks Posed by Ultrasonic Aerosols

Dental procedures involving handpieces and ultrasonic scalers generate splash and spatter that contain microorganisms, which can potentially cause disease. The majority of splash is composed of large droplets that do not travel far, settling on the patient, oral health professional, and surfaces.¹ Veena et al² found that aerosol contamination was most prevalent on the operator and assistant's arms, chest, and face mask, and that aerosol was present in the air for 30 minutes following ultrasonic scaling. Aerosols are small respiratory particles that can linger in the air for up to 30 minutes and are usually less than 10 microns in diameter, making them a potential hazard for disease transmission.1 It is not known how long bloodborne pathogens can remain infective in dental aerosols.³ While no cases of bloodborne pathogen disease transmission from aerosols to oral health professionals have been documented,⁴ studies have shown that these clinicians have a higher prevalence of antibodies to Legionella pneumophila—which causes Legionnaire's disease—suggesting that a risk exists.⁵ Disease transmission from dental unit waterline aerosols to patients has been documented. Two cases of Legionnaire's disease from contaminated dental unit water aerosols resulted in the deaths of an 85-year-old woman in Italy⁶ and an elderly immunocompromised man in Sweden.⁷ Aerosolized water from a high-speed handpiece was most likely the source of the infection.⁶ The United States Centers for Disease Control and Prevention (CDC) provides two main recommendations for oral health professionals to protect themselves from microorganism-laden aerosols and bloodborne pathogens: engineering controls (safety devices) and work practice controls (safe behaviors).¹ Engineering controls are safety devices such as personal protective equipment (PPE). Wearing a lab coat is an excellent way to minimize contamination of clothing and to cover the skin on the arms, chest, and neck, and its use is required by the Occupational Safety and Health Administration bloodborne pathogens standard.⁸ The employer is responsible for providing the lab coat and laundering.⁸ Other PPE that should be used with ultrasonic scaling include protective eyewear with side shields and a well-fitting surgical mask with at least > 95% bacterial filtration efficiency.¹ Work practice controls are safety behaviors that include the use of high velocity evacuation (HVE). High speed suction significantly reduces the amount of splash, spatter, and aerosols that is generated.^9,10 The CDC recommends the use of HVE vs the saliva ejector, which does not adequately control splash, spatter, and aerosols.1 A study by Holloman10 found high levels of bacterial contamination on agar plates with the use of saliva ejectors. Another protective measure is the use of preprocedural mouthrinses prior to ultrasonic scaling. The 2003 CDC guidelines and their 2016 updated companion document still consider this an "unresolved" issue and do not provide specific recommendations.^1,11 However, many studies recommend preprocedural rinsing, particularly with chlorhexidine, as an effective measure to reduce the bacterial load.¹² Although the CDC does not make a specific recommendation about preprocedural rinsing, oral health professionals should consider the type of patients they are treating. If your practice treats a significant amount of immunocompromised patients, especially older adults and those undergoing cancer treatment, a preprocedural rinse may be a good preventive measure. Based on the evidence, I recommend three strategies to control aerosols associated with ultrasonic instrumentation. First, use proper PPE. Second, use HVE whether with an assistant or an HVE device. Third, use a preprocedural mouthrinse with chlorhexidine to reduce the bacterial load. Employing these measures will protect both clinicians and patients.

REFERENCES

1. Kohn WG, Collins AS, Cleveland JL, et al. Guidelines for infection control in dental health care settings—2003. J Am Dent Assoc. 2004;135:33–47.
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8. Occupational Safety and Health Administration. Bloodborne Pathogens Standard. Available at: osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&pid=10051. Accessed January 15, 2018.
9. Harrel SK, Molinari J. Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc. 2004;135:429–437.
10. Holloman JL, Mauriello SM, Pimenta L, Arnold RR. Comaprison of suction device with saliva ejector for aerosol and spatter reduction during ultrasonic scaling. J Am Dent Assoc. 2015;146:27–33.
11. United States Centers for Disease Control and Prevention. Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care. Available at: cdc.gov/oralhealth/infectioncontrol/guidelines/index.htm. Accessed January 15, 2018.
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