Infection Control for Dental Professionals ________________________________________________________
Certain factors affect the risk of HIV transmission after an occupational exposure. Laboratory studies have determined if needles that pass through latex gloves are solid rather than hollow-bore or are of small gauge (e.g., anesthetic needles), less blood is transferred. In a retrospective, case-control study of healthcare personnel, an increased risk for HIV infection was associated with exposure to a relatively large volume of blood, as with a deep injury with a device that was visibly contaminated with the patient’s blood or a procedure that involved a needle placed in a vein or artery [12]. The risk was also increased if the exposure was to blood from patients with terminal illnesses, possibly reflecting the higher titer of HIV in patients with late-stage AIDS. AEROSOLS, DROPLETS, AND SPLATTER Aerosols, droplets (produced by the respiratory tract), and splat- ter contaminated with blood and bacteria are produced during many dental procedures. Devices such as dental handpieces, ultrasonic and sonic scalers, air polishers, air-water syringes, and air abrasion units produce visible aerosol clouds and possible airborne contamination. Splatter generated by dental procedures such as drilling is a primary risk for transmission of bloodborne pathogens. In general, because of their smaller size, aerosols pose the greatest risk for airborne infection [9]. Several studies have shown that airborne or droplet nuclei may extend up to 6 feet away from the source and can remain airborne for up to 30 minutes after a procedure. Tuberculosis (TB) is of special concern because it is a large particle that can remain airborne or can dry on a surface and become airborne again as part of a dust particle. In 2024, the World Health Organization (WHO) and the Centers for Disease Control and Prevention from the United States, China, Europe, and Africa, published a global consen- sus of the terminology for pathogens that transmit through the air. Key changes include [8]: • Any infected particles that are expelled from an individual through nose or mouth are referred to as “infectious respiratory particles” (IRPs). • IRPs exist on a spectrum of sizes and should no longer be distinguished as “small” (aerosol) or “large” (droplet). • The descriptor “through the air transmission” should be used to characterize any transmission that involves a pathogen moving through the air or being suspended in the air. Two further descriptors can be used: ‒ Airborne transmission or inhalation: IRPs are expelled into the air and inhaled by another person. This can occur at short or long distances, dependent on various factors (e.g., airflow, humidity, temperature, ventilation).
‒ Direct deposition: IRPs are expelled into the air and directly deposited on the exposed mouth, nose, or eyes of another person. Due to the existing research and recommendations primarily using the terms and definitions of “aerosol” and “droplet,” these terms will continue to be used throughout this course, unless otherwise noted. The American Dental Association recommends that in addi- tion to using Universal and Standard Precautions, such as masks, gloves, and eye protection, Transmission-Based Precau- tions, including the proper sterilization of instruments and treatment of dental unit waterlines is necessary to reduce or eliminate this source of potentially contaminated dental aero- sols. Preprocedural rinsing with an antimicrobial mouthwash such as chlorhexidine is also recommended, although it is only effective for oral bacteria found in saliva and those adhering to mucous membranes. It does not penetrate subgingivally and likely has no effect on bacteria in the nasopharynx [5; 6]. Diseases known to spread by aerosols or droplet include: • TB • Pneumonic Yersinia pestis infection (plague) • Influenza • Legionellosis (Legionnaires disease) • Measles • Chickenpox • Disseminated shingles • Severe acute respiratory syndrome and coronavirus (SARS and COVID) Procedures or equipment aimed at eliminating the means of transmission include [5; 6]: • Universal preprocedural rinses • Dental dams for certain procedures • High-volume evacuator (HVE) at the treatment site (An HVE can only remove airborne contamination if it removes a large volume of air. A saliva ejector does not remove enough air to be classified as an HVE.) • High-efficiency particulate arresting and ultraviolet filters in the ventilation system • Disposable PPE discarded after each patient (e.g., gloves, masks, gowns) • Cleaning, disinfection, and sterilization of equipment used by more than one patient • Environmental cleaning and disinfection, especially of high-touch surfaces
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