Chris Miller, PHD
Once contamination (the spreading of microbes to an individual) occurs, disease may or may not develop. Factors influencing the development of disease include the route of entry into the body; disease-producing properties of the microbe; the number of microbes contaminating the individual; and body resistance. Evidence showing how microbes are spread (how contamination occurs) is much easier to obtain than evidence showing the actual spread of disease (damage to the body after the contamination has occurred). Some evidence actually documenting disease after contamination in the dental office does nevertheless exist.
This is the first in a series of articles discussing the five main pathways by which microbes are spread in the office:
- Patient to dental team
- Dental team to patient
- Patient to patient
- Office to community
- and community to office
Regardless of the pathway of microbe spread, six basic steps must be completed for an infectious disease to occur:
1. existence of a source of microbes;
2. escape of the microbes from the source;
3. spread of the microbes to a new host;
4. entrance of the microbes into the new host;
5. growth and survival of the microbe in the new host (infection);
6. damage of the new host.
The actual spread of a microbe from a source to a new person involves steps 2, 3, and 4, and infection-control procedures concentrate on interfering with these steps, preventing or reducing the level of contamination.
We start the series by addressing the spread of microbes from patients to the dental team.
The patient`s mouth is the main source of microbes in this "pathway." Evidence shows that microbes transferred from patients to the dental team may cause disease. The spread of herpes simplex virus from a patient`s mouth (a fever blister) to the hands of a hygienist has been reported. Also, reports describing the occurrence of hepatitis B among dental personnel indicate that dental personnel are at greater risk than the general population. However, since 1985, there has been a 90 percent decrease in the number of health care workers who have acquired hepatitis. This has likely resulted from use of the hepatitis B vaccine and infection-control procedures involving barrier protection.
Direct contact with the patient`s mouth may result in a spread of microbes. Wearing gloves to prevent contamination and to protect "invisible" breaks in the skin addresses this pathway. Hand washing also reduces the level of transient microbes contaminating the hands.
Microbial spread via droplets or aerosols of the patient`s oral fluids may result in contamination of the skin or clothing, as well as the mucous membranes of the eyes, nose, mouth, and respiratory system. This contamination can be managed by wearing gloves, protective clothing, eyewear or face shield, and a mask. The level of contamination that may occur can be reduced by using a pre-procedure mouthrinse, high-volume evacuation, rubber dam, and judicious use of the air/water syringe.
Indirect contact with items (fomites) or surfaces contaminated with microbes also causes a microbial spread. One key pathway is receiving an injury from a contaminated sharp such as an instrument, orthodontic wire, needle, file, scalpel blade, or any item that could puncture the skin. Preventing this contamination in-volves handling sharps carefully and using heavy-duty gloves for operatory cleanup and handling of contaminated instruments. Other modes of preventing sharps injuries include:
- Eliminating hand-scrubbing of contaminated sharp instruments and using an ultrasonic or washer/disinfector cleaning system.
- Using cassettes to reduce direct handling of instruments during processing.
- Eliminating hand-sharpening of contaminated instruments.
- Wearing gloves and other barriers when handling contaminated objects and when cleaning and disinfecting contaminated surfaces. Handwashing also reduces the level of transient microbes contaminating the hands.
Immunization of the dental team with available vaccines greatly aid in preventing the spread of certain diseases, particularly hepatitis B.
- Manzella et al: An outbreak of herpes simples virus type I gingivostomititis in a dental hygiene practice. J Amer Med Assoc 252:2019-2222, 1984
- Cottone and Puttaiah: Hepatitis B virus infection: current status in dentistry. Dent Clin No Amer 40[No 2]:293-307, 1996 (see summary)
Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.