Number of Microorganisms

To cause disease, a high enough number of pathogenic microorganisms must be present to overwhelm the body’s defenses. The number of pathogens may be directly related to the amount of bioburden present. Bioburden refers to organic materials such as blood and saliva. The use of the dental dam and high-volume evacuation helps to minimize bioburden on surfaces, thereby reducing the number of microorganisms in the aerosol.

Susceptible Host

A susceptible host is a person who is unable to resist infection by a particular pathogen. An individual who is in poor health, is chronically fatigued and under extreme stress, or has a weakened immune system is more likely to become infected. Therefore, staying healthy, washing the hands frequently, and keeping immunizations up-to-date will help members of the dental team to resist infection and stay healthy.

Portal of Entry

To cause infection, pathogens must have a portal of entry, or a means of entering the body. The portals of entry for airborne pathogens are the mouth and the nose. Blood-borne pathogens must have access to the blood supply as a means of entry into the body. This can occur through a break in the skin caused by a needle stick, a cut, or even a human bite. It can also occur through the mucous membranes of the nose and oral cavity.

Acute Infection

In acute infection, symptoms often are severe and usually appear soon after the initial infection occurs. Acute infections are of short duration. For example, with a viral infection such as the common cold, the body’s defense mechanisms usually eliminate the virus within two to three weeks.

Chronic Infection

Chronic infections are those in which the microorganism is present for a long duration; some may persist for life. The person may be asymptomatic (not showing symptoms of the disease) but may still be a carrier of the disease, as with hepatitis C virus (HCV) or human immunodeficiency virus (HIV) infection.

Latent Infection

A latent infection is a persistent infection in which the symptoms “come and go.” Cold sores (oral herpes simplex) and genital herpes are latent viral infections.

The virus first enters the body and causes the original lesion. It then lies dormant, away from the surface, within a nerve cell, until certain conditions (such as illness with fever, sunburn, and stress) cause the virus to leave the nerve cell and seek the surface again. Once the virus reaches the surface, it becomes detectable for a short time and causes another outbreak at that site.

Another herpesvirus, herpes zoster, causes chickenpox. This virus may lie dormant and later may erupt as the painful disease shingles.

Opportunistic Infection

Opportunistic infections, which are caused by normally nonpathogenic organisms, occur in individuals whose resistance is decreased or compromised. For example, in an individual who is recovering from influenza, pneumonia or an ear infection may develop. Opportunistic infections are common in patients with autoimmune disease or diabetes and in elderly persons.

Naturally Acquired Immunity

Naturally acquired immunity occurs when a person has previously contracted a disease and recovered. When the body was fighting the invading pathogen, it formed antibodies that provide future resistance against that particular pathogen. This form of immunity is called active immunity because the body of the host is actively involved in the process.

Artificially Acquired Immunity

When the human body has not been exposed to a disease, it has not developed antibodies and is completely defenseless against the disease. However, antibodies can be introduced into the body artificially by immunization or vaccination.

A vaccine that contains weakened disease-causing organisms or genetically engineered organisms is injected into the body. Harmful characteristics of the disease-producing organisms are eliminated from the vaccine to make them less likely to cause disease. The body then forms antibodies in response to the vaccine, resulting in artificially acquired immunity.

Patient to Dental Team

Dental Team to Patient

Fortunately, the spread of disease from a member of the dental team to a patient is very unlikely to happen. If proper procedures are not followed, however, disease transmission could occur.

Team-to-patient transmission can result if the dental team member has lesions on the hands, or if the hands are cut while in the patient’s mouth, permitting the transfer of microorganisms. Droplet infection of the patient can occur if the dental team member has a cold, but this can also occur outside the dental office.

Infection control measures that help to prevent team-to-patient transmission include (1) masks, (2) gloves, (3) handwashing, and (4) immunization.

Patient to Patient

Patient-to-patient disease transmission has occurred in the medical field, but only one case of this type of transmission has been documented in dentistry. For this type of transmission to occur, contamination from instruments used on one patient would need to be transferred to another patient.

Dental Office to Community

Microorganisms can leave the dental office and enter the community in a variety of ways. For example, contaminated impressions may be sent to the dental laboratory, or contaminated equipment may be sent out for repair. Office-to-community transmission also can occur if members of the dental team transport microorganisms out of the office on their clothing or in their hair.

Infection control measures that help prevent organisms from leaving the dental office include (1) handwashing, (2) changing clothes before leaving the office, and (3) disinfecting impressions and contaminated equipment before such items leave the office.

Community to Dental Office to Patient

Exposure Control Plan

Each dental office must have a written exposure control plan that clearly describes how that office complies with the BBP Standard. This exposure control plan must be reviewed and updated at least annually. A copy must be made available to all employees.