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The Fragile Immune System

Infection control precautions and practices must be strictly adhered to in order to protect both the immune compromised patient and clinician.

New or emerging diseases that were once considered under control but are now re-emerging are causing much concern for health care providers and patients. While there is no question that some previously unknown diseases such as Ebola and HIV have emerged in the past 20 years, many of the diseases currently causing concern are re-emerging diseases like tuberculosis, polio, and antibiotic resistant Staphylococcal infections.

In the developed world, many of these diseases are found in a population that was nearly nonexistent 30 years ago—the immune compromised individual. For a variety of reasons, these individuals do not have a competent immune system, making them susceptible to diseases that most healthy people can successfully resist. As medical care improves and people live longer, the population of immune compromised individuals is rapidly expanding. Because these individuals often remain ambulatory, they are increasingly seen for routine dental hygiene care. The likelihood also exists that an increasing number of dental hygienists who are immune compromised are continuing to actively practice dental hygiene.

Figure 1. A high volume evacuator placed close to the operating site during ultrasonic scaling. The device shown will eliminate greater than 95% of the airborne contamination created during ultrasonic scaling.

Who is Immune Compromised?

The immune system is our basic defense against infection. It is a highly complex, internally regulated system that recognizes an infectious agent, reacts to the infectious agent by stimulating the body’s defensive system, and finally kills or controls the infectious agent. In the immune compromised individual, some part of this system fails to respond properly and the infectious agent gains the advantage. The end result is that an infection occurs and an immune system failure may lead to serious illness or even death.

Many diseases and medications can cause the immune system to be compromised. The most striking example of immune compromise is the patient infected with HIV/AIDS.1 The virus that causes AIDS attacks a part of the immune system—the T cells—that respond to the invasion of infectious agents. Because the body’s immune defense does not respond adequately to the invading organism, an infection occurs. Due to the weakness of the entire immune defense system in the AIDS patient, serious bacterial or viral infections may occur that would not normally affect a healthy individual.

In the oral cavity, AIDS patients commonly have serious yeast infections caused by Candida albicans.2 This yeast is present in almost everyone’s mouth and normally does not cause a clinically detectable disease but, due to a compromised immune system, an AIDS patient can experience a serious and even life threatening infection. Other diseases can cause varying amounts of immune compromise with a weakening of resistance to infections but most are not as dramatic as HIV/AIDS.

One of the most commonly seen diseases that can cause immune compromise is diabetes mellitus.3 Because diabetes can directly inhibit the immune system, it is possible that even well-controlled diabetics may be more prone to infection than nondiabetics.4 However, the greatest concern is for moderately to poorly controlled diabetics because they can be very susceptible to infection and the treatment of an established infection is often difficult.5 See Table 1 for a list of diseases that can compromise the immune system.

Figure 2. A combination splatter shield and vacuum placed at the work site during air polishing. The device shown will remove greater than 90% of the airborne contamination created during air polishing.

Medications can also compromise the immune system. The most obvious examples are the drugs used to prevent the rejection of transplanted organs and tissues. These so-called antirejection drugs are actually designed to suppress the patient’s natural immune response to foreign tissue. Without this immune suppression, the transplanted organ would be recognized as foreign and rejected. A negative side effect of these drugs is that the patient’s natural immune protection against infection is also suppressed.6 Depending on the exact antirejection drugs used, transplant patients can be extremely susceptible to infections from organisms that would not be harmful to a person who was not taking the drugs.

There are many widely used types of immune suppressing drugs. One of the most common is systemic corticosteroids.7 These drugs are used for many dermatologic lesions of the skin and mouth, Crohn’s disease, lupus erythematosus, and other disorders. Patients using long-term cortisone can become extremely susceptible to infection from organisms that are innocuous to the immune competent individual. Most drugs used for treating cancer (chemotherapy) cause an immune compromised status that continues as long as the patient is undergoing chemotherapy. In most instances, the immune compromised status will no longer be present after chemotherapy ceases. Elective treatment should be avoided during active chemotherapy. There are some cases where chemotherapy medications are used for a longer term as in the use of methotrexate for autoimmune diseases. The dosages of the chemotherapy medications are usually reduced for these chronic conditions compared to their use in anticancer therapy and the risk for significant immune compromise is probably less. Table 2 lists some of the medications that may cause immune suppression.

Precautions for Dental Hygiene Treatment

A thorough medical history and often a medical consultation are indicated for all patients known or suspected to be immune compromised. If there are questions regarding the patient’s treatment, the hygienist should contact the treating physician and determine if preoperative antibiotics, modification of the patient’s medication regime, or avoiding certain treatment is indicated. During hygiene treatment, the immune compromised patient must avoid any contact with organisms carried by dental personnel or other patients.

The routine sterilization of instruments and disinfection of environmental surfaces will greatly reduce the chances of organisms arising from other patients, challenging the immune compromised patient. However, contaminated aerosols generated from patient care are capable of staying airborne for more than 30 minutes and it is possible that contamination from a previous patient could still be airborne when the immune compromised patient enters the room or that a pathogenic organisms could enter the ventilation system and be transferred to another room occupied by an immune compromised patient.8 The only way to minimize this potential threat is to limit the aerosols arising from the treatment site by the routine use of a high volume evacuator (HVE).9 Additionally, dental hygienists should fit their masks firmly in place prior to entering the room and not remove the mask until the patient is dismissed. Avoiding touching anything but the patient and the instruments used for the procedure will also reduce the danger of cross contamination from environmental surfaces and the operator.

Figure 3. An N-95 facemask showing a close fit to the face. This facemask is capable of filtering 95% of all airborne contamination.

Scrupulous infection control protocols should be followed. The Centers for Disease Control and Prevention (CDC) recently issued new infection control guidelines for dentistry.10 Many hygienists view the use of personal protective equipment (PPE), such as masks and gloves, as primarily protection for the operator. For all patients, but especially for the immune compromised patient, the use of PPE must also be viewed as protection for the patient. For the immune compromised patient, organisms that occur in the operator’s mouth, nose, and skin that are usually considered noninfectious have the potential for causing infection. For the patient’s protection, close attention should be given to the fit of masks, potential breaks in barriers, like gloves, and avoiding cross contamination from contaminated surfaces.

In addition to PPE, attention must also be given to what the CDC refers to as “work practices.” Work practices are measures that the CDC recommends for all dental procedures.11 The work practice that most affects the dental hygienist is the routine use of an HVE during ultrasonic scaling and air polishing. The CDC recommends that an HVE be used during any procedure that generates contaminated aerosols or splatter. Two instruments routinely used by the hygienist—the ultrasonic scaler and the air polisher—have been shown to produce large amounts of aerosols and splatter that are highly contaminated with bacteria and blood.12,13 These aerosols are also likely to be contaminated with viruses and other organisms from the naso-pharynx such as the cold virus, influenza, and potentially Severe Acute Respiratory Syndrome (SARS).

Since the immune compromised patient is at increased risk of infection, at first glance it may seem that extra precautions are indicated. However, scrupulous observance of the standard precautions recommended by CDC should be adequate for all but the most immune fragile patient. Unfortunately, with the press of practice schedules and the need to rapidly move a patient in and out of a treatment room, many breaks in infection control may occur. Just as “universal precautions” were initially based on the assumption that all patients carried the HIV/AIDS virus, it should also be assumed that all patients may have some form of immune compromise and strict infection control procedures should be followed.

Precautions for the immune compromised hygienist

The immune compromised hygienist needs to closely follow the CDC guidelines for infection control. Just as the immune compromised patient will be more susceptible to infection when exposed to normally innocuous organisms, immune compromised hygienists must be especially cautious of organisms carried by the patients they treat. Because the practicing hygienist will come in contact with many different patients each day, they will also be exposed to a large variety of organisms carried by those patients.

As in all dental treatment situations, one of the greatest dangers for the hygienist is a puncture by a contaminated instrument. Work practices such as one handed needle recapping and safe instrument sharpening are particularly important for the immune compromised hygienist. As noted for the immune compromised patient, another important work practice is the control of contaminated aerosols. For the safety of an immune compromised hygienist, contaminated dental aerosols should be contained to the greatest extent possible at the treatment site meaning that the aerosol from an ultrasonic scaler should be removed by an HVE held as close to the treatment site as possible.14 Figure 1 shows an attached HVE placed next to the site of ultrasonic scaling. A saliva ejector is not an HVE and is inadequate for the control of aerosols. For the air polisher, the use of a combined suction/barrier device to limit the aerosol spray should be routine.15 Figure 2 shows one of the devices in use. Additionally, the immune compromised hygienist should consider using a mask that gives greater respiratory protection than most masks used in dentistry. Masks that don’t fit closely tend to act only as mucous membrane barriers for the nose and mouth and often will only eliminate airborne contamination in the form of splatter. The use of using an N-95 facemask will greatly increase protection from airborne contamination. This form-fitting (duck-billed) facemask, shown in Figure 3, is capable of filtering out 95% of all organisms. The N-95 mask has been shown to be effective in controlling airborne and droplet borne diseases such as SARS and influenza.16

The number of immune compromised patients and hygienists will continue to increase as improvements in medical care allow more individuals to lead an active life who in the past would have died or been confined to a medical facility. The infection control precautions and work practices that are currently in place are adequate for the treatment of these patients and for the protection of the hygienist but they must be strictly followed to avoid infection in individuals at increased risk.


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  3. Mealey BL, Moritz AJ. Hormonal influences: effects of diabetes mellitus and endogenous female sex steroid hormones on the periodontium. Periodontol 2000. 2003:32;59-81.
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From Dimensions of Dental Hygiene. June 2004;2(6):12-14, 16.

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