The historical importance for routine infection control procedures was underscored by epidemiologic investigations and other scientific evidence in the 1970s and 1980s. It was estimated at that time that an office treating 20 patients a day would encounter one active carrier of hepatitis B virus (HBV) every 7 days.⁹ This early finding, coupled with the fact that most microbial infections, including those caused by HBV, hepatitis C virus (HCV), and human immunodeficiency virus (HIV), can be infectious before distinct signs and symptoms appear, makes the likelihood of unknowingly treating an infectious patient a certainty. Failure to treat every patient as potentially infectious—that is, with standard precautions, previously termed universal precautions—places the health care worker and all patients at needlessly increased risk of infection.^5,7

The overall goals of infection control programs are as follows: (1) to reduce the numbers of pathogenic microorganisms to levels where patients’ normal defense mechanisms can prevent infection, (2) to break the cycle of infection and eliminate cross-contamination, (3) to treat every patient and instrument as capable of transmitting infectious disease, and (4) to protect patients and health care workers from infection and its consequences.^7,15 The proper use of barrier techniques (gloves, mask, gown, eye protection, rubber dam), proper sterilization, disinfection, and antisepsis protocols accomplishes these goals.

It is important at the beginning of this chapter to understand the differences between the terms sterilization, disinfection, and antisepsis.^8,28 Sterilization is the ultimate goal of any infection control protocol because it is the killing of all forms of microorganisms. To eradicate resistant viruses and bacterial endospores effectively requires the application of high heat or chemicals or both for a sufficient time. The most widely used means of attaining this objective in a dental office are dry heat, steam, and chemical vapor sterilization units. In medicine and industry, sterilization includes ethylene oxide and formaldehyde gases, ultraviolet and gamma radiation, and filtration. Disinfection is the application of chemicals to destroy most pathogenic organisms on inanimate surfaces. Although some chemicals used for disinfection are capable of achieving sterilization given sufficient time of exposure, their use to effect sterilization is discouraged because of the number of conditions that can lead to failure in this application. Antisepsis is the use of chemicals to destroy or inhibit pathogenic organisms on skin or living tissue. The difference between disinfection and antisepsis may seem small, but it leads to a wide divergence in the products used and the regulation of the products. Disinfectants fall under the regulatory authority of the U.S. Environmental Protection Agency and are subject to that agency’s rules for demonstration of effectiveness and use in the workplace. Antiseptics, because they are intended for application on living tissue, fall under the regulations of the U.S. Food and Drug Administration (FDA) regarding effectiveness and clinical use.

Numerous treatment area surfaces can become contaminated with saliva, blood, and other potentially infectious substances during provision of care. The routine use of chemical disinfectants and disposable supplies has become historically more appropriate in certain instances because it is neither possible nor necessary to sterilize all contaminated items or surfaces. This trend is especially applicable in dentistry, where many instruments and environmental surfaces become contaminated with saliva and blood during routine procedures.^8,9 Organisms contained in these fluids include staphylococci, streptococci, Mycobacterium tuberculosis, cytomegalovirus, herpes simplex virus (HSV), HBV, HCV, HIV, and a number of upper respiratory tract viruses such as influenza and rhinoviruses. Environmental surfaces in particular do not lend themselves to sterilization and must be cleaned and disinfected or covered with disposable barriers.^5,7,11

Before selecting an environmental surface disinfectant, products under consideration should be compared with criteria for an ideal disinfectant. These criteria are as follows: The disinfectant should have the widest possible antimicrobial spectrum, including the ability to kill the vegetative form of all pathogenic organisms. The chemical agent should be able to remain active in the presence of organic matter (i.e., blood, saliva, sputum). It should be inexpensive, odorless, effective at room temperature, noncorrosive, nonstaining, nontoxic to humans, and require a short time of exposure. Given the numerous similarities in chemical composition and metabolism between humans and microorganisms, this ideal is unlikely to be achieved. In practice, however, proper use of available chemical disinfectants reduces the numbers of viable pathogenic organisms on surfaces to levels that allow a healthy person’s natural defenses to prevent infection.

The ideal antiseptic would have properties similar to those of an ideal disinfectant. Selective toxicity to microorganisms but not to human cells is of primary importance for antiseptics. The degree of selectivity of the antiseptic agents can vary depending on the tissues with which they come in contact. An antiseptic intended for handwashing can be less selective than one used in an oral rinse because the highly keratinized epithelium of the skin affords a greater degree of protection from the antiseptic than does the oral epithelium.

Various antiseptics and disinfectants can be classified according to mechanism of action: agents that denature proteins, agents that cause osmotic disruption of the cell, and agents that interfere with specific metabolic processes. Agents that cause protein denaturation or osmotic disruption tend to kill the organisms and are described as bactericidal, virucidal, or fungicidal in nature. Interference with specific metabolic processes usually affects cell growth and reproduction without killing the cell, causing a bacteriostatic/virustatic/fungistatic effect.

Table 46-1 lists representative classes of compounds used as disinfectants or antiseptics with their effectiveness against various representative organisms. The aldehyde and certain halogen-based and oxidizing compounds have the broadest range of effectiveness. These agents also tend to be the most toxic to human tissue. Consequently, their use has been primarily limited to disinfection. The other chemical classes are less effective antimicrobial agents, but also tend to be less harmful to human tissue and find use as disinfectants and antiseptics. Some distinguishing features of the chemical groups are listed in Table 46-2, and their major clinical uses are noted in Table 46-3.

TABLE 46-2 Characteristics of Common Chemical Disinfectants

TABLE 46-3 Miscellaneous Uses of Disinfectants and Antiseptics