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Dental healthcare professionals may be at risk of exposure to numerous workplace hazards. These hazards include, but are not limited to, a spectrum of bloodborne and other microbial pathogens, pharmaceuticals and other chemical agents (ie, liquid, solid, gaseous), ergonomic hazards, radiation, noise, vibration, heat, traumatic injury, and workplace violence.1 Although there are no Occupational Safety and Health Administration (OSHA) standards specific to dentistry, regulations regarding exposure to numerous biological, chemical, environmental, physical, and psychological workplace hazards that may apply to dentistry are addressed in OSHA's standards for General Industry.1
Infectious Diseases
An infectious disease occurs when a pathogenic microorganism gains access to a susceptible host, then multiplies and causes some type of damage. Depending on their source, infectious diseases can be either endogenous and exogenous.
Endogenous infections involve microorganisms normally present on or in the human body (ie, indigenous, normal flora) that usually do not cause noticeable harm. However, certain changes, including immunosuppression, the onset of diabetes, trauma, occupational exposure, a number of personal behaviors, and antibiotic use can allow these microorganisms (ie, opportunistic pathogens) to cause disease.
Exogenous infections involve microorganisms not normally present on or in the human body. There are many sources of exogenous infections, including the environment, humans, animals, insects, food, and beverages.
Development of Infectious Disease
A number of factors influence whether or not exposure to a pathogenic microorganism will result in disease, including a person's immune, nutritional, and overall health status; therefore, exposure does not always mean than an infection will occur. The usual course of an infectious disease involves six steps or stages. The process is often called the "chain of infection" (see Table 1).2,3
Sources of Pathogens
In dental healthcare settings, the largest sources of microorganisms are the patients. However, microorganisms from dental healthcare professionals can also be involved in cross-transmission. The area with the greatest number of microorganisms present is the patient's oral cavity, but potential pathogens can readily spread outward. It is not possible to identify which patients harbor pathogens. Many are not aware of their infection status (ie, asymptomatic carriers). It is best practice to consider all patients as potentially infectious and to use infection prevention and control procedures (ie, Standard Precautions) routinely and equally.1,2,4
The US Centers for Disease Control and Prevention's (CDC) Standard Precautions are the minimum infection prevention practices that apply to all patient care, regardless of suspected or confirmed infection status of the patient, in any setting where healthcare is delivered. These practices are designed to protect dental healthcare professionals as well as prevent them from spreading infections among patients. The Standard Precautions include: 1) hand hygiene, 2) use of personal protective equipment (PPE) (eg, gloves, masks, eyewear, protective gowns), 3) respiratory hygiene/cough etiquette, 4) sharps safety (ie, engineering and work practice controls), 5) safe injection practices (ie, aseptic technique for parenteral medications), 6) sterile instruments and devices, and 7) clean and disinfected environmental surfaces.5
Release of Pathogens
The second step in the development of an infectious disease is the escape of the pathogens from their source. Normal activities such as talking, sneezing, or coughing release oral microorganisms into the environment. Many dental procedures (eg, high-speed instrumentation, ultrasonic cleaning, use of air-water syringes) facilitate the outward spread of patient body fluids in the form of spatter, droplets, and aerosols. In addition, items that are used intraorally (eg, instruments, x-ray films, gloves) readily become contaminated. Materials such as teeth, gingival tissue, appliances, and restorations that are removed from the patient are also potential sources of infection.1,2,4-6
Transmission
Microorganisms spread from one person to another in four manners:
Direct contact. The direct, unprotected contact of a dental healthcare professional's skin or mucus membranes with a patient's teeth, soft-tissue, or oral fluids is a highly efficient pathway for disease acquisition. Today, the routine use of PPE and the adoption of other infection prevention and control procedures have minimized microbial spread by direct contact.1-6
Indirect contact. This method of transmission involves exposure to items that have been contaminated with microorganisms. Transmission through indirect contact usually results from needlestick accidents and contact with contaminated instruments or pieces of equipment. Inert environmental surfaces (ie, fomites) can also be involved. Proper sterilization, disinfection, and personal and environmental barriers reduce the chances of spreading infectious disease by indirect contact.1-6
Droplet transmission. Many dental treatments cause the release of droplets (ie, liquid drops > 5 microns) from the patient. Being relatively large, droplets tend to settle a short distance from the oral cavity. The correct use of high volume evacuators and air-water syringes can reduce droplet production, and wearing PPE can reduce the chances of droplet infection. Furthermore, the proper management of microorganisms present in dental unit waterline emissions will help reduce the hazards associated with droplets and aerosols. Protection of the immediate environment using various types of physical barriers and effective disinfection is also needed.1-6
Airborne inhalation. This method of transmission involves contact with particles so small (ie, droplet nuclei or aerosol particles < 5 microns) that they can remain suspended in the air for extended periods, increasing their chances of being inhaled. The surgical masks commonly used in dentistry are not designed to protect the wearer from inhaling airborne particles and are less effective than N95 respirators. However, it is more difficult to breathe through a respirator, and their use requires training and fit testing to better ensure proper function. If using a surgical mask, attention should be paid to the mask's shape, level of filtering efficiency, and proper fit. During use, masks can become moist, which not only affects the wearer's ability to breathe, but also reduces the efficacy of filtration. Moistened masks should be changed.1-6
Routes of Entry
Microorganisms gain access to the human body through four routes of entry: inhalation, ingestion, absorption into mucus membranes, and infiltration through breaks in the skin. Inhalation involves breathing in aerosol particles, and ingestion is the swallowing of patient body fluids. Absorption into mucous membranes occurs when droplets of blood and/or saliva are spattered into the eyes, noses, or mouths of dental healthcare professionals. Efforts to reduce the production and release of droplets and aerosols combined with proper use of PPE markedly decrease the chances of microorganisms entering a new host.1-6 Intact skin is an effective barrier to the entrance of microorganisms. However, cuts and abrasions are commonly present and often go unnoticed. Skin is readily compromised by "sharps," such as needles, hand instruments, burs, and files. The proper use of gloves and hand hygiene as well as training in sharps awareness and management can help protect the skin of dental healthcare professionals from microbial penetrance.1-6
Infection
Infection is the state produced by the growth and continued survival of microorganisms on or in a susceptible host. Microorganisms are commonly present in the human body; however, their presence does not mean that a harmful infection and subsequent damage will occur. The pathogenic potential of a microorganism involves its ability to enter a host, multiply, and then avoid and/or interfere with the host's defenses. Bacterial damage can involve degrading enzymes and result in cell death from cytotoxic waste products and toxins, whereas viral damage can interfere with normal cellular functions and actually kill host cells directly.
All microorganisms can produce an inflammatory effect that elicits a host immune response. However, the long-term presence of microorganisms can result in an immune response that is more damaging than protective. A host's response to infection involves a number of disease management processes.1-6
Immunizations
Immunization of dental healthcare professionals against vaccine-preventable diseases is an essential component of a successful infection control program. The routine administration of vaccines prevents disease transmission among practitioners, patients, their families, and the local community. It is always better to take actions to prevent an infection than to adopt a wait and see approach and potentially have to treat and/or contain an infectious disease.
Currently, CDC recommends routine immunization to prevent 17 vaccine-preventable diseases that occur in infants, children, adolescents, or adults. Five of these vaccines are commonly recommended for all healthcare personnel (see Table 2); therefore, it is imperative that all dental healthcare professionals remain up-to-date with these recommended vaccines.7-9
The hepatitis B virus (HBV) spreads through skin punctures; mucosal contact with infectious fluids, including blood and saliva; and exposure to patients' open wounds. HBV can survive on environmental surfaces and remain infectious for at least 7 days. Approximately 2% to 6% of adults will eventually develop a chronic HBV infection, which increases the chances of cirrhosis and liver cancer. After three intramuscular doses of the hepatitis B vaccine, more than 90% of healthy adults develop adequate antibody responses.9,10
Although current information indicates that HBV vaccine-induced antibody levels decline over time, immune memory can remain intact for more than 20 years, so those with declining antibody levels are still protected against significant HBV infection (eg, clinical disease, HBsAg antigenemia, significant elevation of liver enzymes). Exposure to HBV among these individuals results in an anamnestic anti-HBsAg response that prevents clinically significant HBV infection. Chronic HBV infection has rarely been documented among vaccine recipients. The potential need for booster doses will continue to be assessed.9-11
Influenza is a serious disease that can lead to hospitalization and sometimes death. All healthcare personnel should receive a yearly influenza vaccination. Each year, the composition of the vaccine is adjusted to protect against the specific strains of the influenza virus that research has indicated will be most commonly present during the upcoming season. Infected healthcare personnel can spread influenza to their patients, coworkers, and families.9-11
Emphasizing Education
To achieve the highest level of disease prevention, immunizations must be combined with a number of other activities. These include employee education and training, postexposure management, identification of medical conditions and work-related illnesses, and engineering and work practice controls. Also needed are correct sterilization and disinfection procedures, compliance with hand hygiene protocols, and proper selection and use of PPE.
Not all diseases can be prevented through immunization. For dental healthcare professionals in the United States, these include hepatitis C virus, HIV/AIDS, several types of herpesvirus, and tuberculosis.
The transmission of infectious agents among patients and dental healthcare professionals in dental settings is rare. However, from 2003 to 2015, occurrences of transmissions in dental settings, including patient-to-patient transmissions, were documented. These reports highlight the need for comprehensive training to improve dental healthcare professionals' understanding of the underlying principles of infection, the conditions that have to be met for disease transmission, and recommended infection control practices and their implementation.2,12
About the Author
Charles John Palenik, MS, PhD, MBA†
President and CEO
Great Calumet Infection Prevention Control Consultants Inc.
References
1. Occupational Safety and Health Administration. Dentistry. United States Department of Labor Website. https://www.osha.gov/SLTC/dentistry/index.html. Accessed September 28, 2018.
2. Miller CH. Infection Control and Management of Hazardous Materials for the Dental Team. 6th ed. St. Louis, MO: Elsevier; 2018.
3. Palenik CJ. Personal protective equipment (PPE) in the dental workplace: its value and limitations. CDE World Website. https://cdeworld.com/courses/20679-Personal_Protective_Equipment-PPE-in_the_Dental_Workplace:Its_Value_and_Limitations?c=294. Published April 2017. Accessed October 29, 2018.
4. Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings-2003. MMWR 2003;52(No. RR-17):1-61.
5. Centers for Disease Control and Prevention. Standard precautions. CDC Website. https://www.cdc.gov/oralhealth/infectioncontrol/summary-infection-prevention-practices/standard-precautions.html. Accessed August 1, 2018.
6. Centers for Disease Control and Prevention. Summary of Infection Prevention Practices in Dental Settings: Basic Expectations for Safe Care. CDC Website. https://www.cdc.gov/oralhealth/infectioncontrol/pdf/safe-care2.pdf. Published October 2016. August 1, 2018.
7. Centers for Disease Control and Prevention. Immunization of health-care personnel: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recommendations and Reports.60(RR-07);1-45, 2011.
8. Centers for Disease Control and Prevention. Recommended vaccines for healthcare workers. CDC Website. https://www.cdc.gov/vaccines/adults/rec-vac/hcw.html#modalIdString_CDCTable_0. Updated April 20, 2017. Accessed August 2018.
9. Palenik CJ. Recommended vaccines for healthcare workers. Dent Update. 2018; 45(4):364-365.
10. Centers for Disease Control and Prevention. Healthcare personnel: are your vaccinations up-to-date. CDC Website. https://www.cdc.gov/vaccines/pubs/downloads/f_hcp_color_print.pdf. Updated June, 2016. Accessed October 2017.
11. Hamborksy J, Kroger A, Wolfe C. Centers for Disease Control and Prevention. Epidemiology and Prevention of Vaccine-Preventable Diseases. CDC Website. https://www.cdc.gov/vaccines/pubs/pinkbook/downloads/table-of-contents.pdf. Published April 2015. Accessed October 29, 2018.
12. Cleveland JL, Gray SK, Harte JA, et al. Trans-mission of blood-borne pathogens in US dental health care settings 2016 Update. J Am Dent Assoc. 2016;147(9):729-738.
