Surface and Equipment Asepsis

Types of Surface Covers

Contamination can be prevented by proper placement of a surface cover before an opportunity for contamination exists. Surface covers should be impervious to fluids to keep microorganisms in saliva, blood, or other liquids from soaking through to contact the surface. Examples of appropriate material for surface covers include clear plastic wrap, bags, or tubes, and plastic-backed paper. Some plastics are designed specifically for use as surface covers in the office in that they have the shape of the item to be covered (e.g., air/water syringe handle covers, hose covers, and pen covers). Some sheets of plastic also have a slightly sticky substance on one side to hold them on the surface. Other plastics (e.g., some food wraps) have a natural clinging ability on contact with a smooth surface. Some plastic bags are available with drawstrings that hold the bag around an item to be protected. To reduce costs, one can use thin rather than thick plastic sheets or bags as long as they are not punctured by the surface being covered. Patient bibs are made of plastic-backed paper and also can be used to cover flat operatory surfaces, although thin plastic sheets may be less expensive.

Use of Surface Covers

Dental units come in several shapes and sizes with different positioning of the handpiece control system and light and other accessories. Thus the sizes and shapes of surfaces to be covered vary from one office to the next, but general procedures for use of surface covers are the same (Procedure 12-1).

Clear plastic bags are available in various sizes and are easy to use. For example, if a chair has control buttons on the side, one can use one bag to cover the headrest and the buttons (Figure 12-1). Wraparound backs of side chairs used by the dental team may be touched during patient care and can be covered with a large plastic bag (Figure 12-2). On units with a bracket table, one may use one bag to cover the handpiece control unit and the bracket table (Figure 12-3 and Figure 12-4). One can cover hoses and connectors with plastic tubing that is secured with tape or a rubber band at the connector or can force a narrow, long plastic bag over the connector end (Figure 12-5).

Light handles and light switches commonly are touched during patient care and can be covered with plastic wrap or bags, depending on their shape (Figure 12-6). Some lights have removable handles that can be cleaned and heat sterilized before reuse. Covering the air/water syringe handle with plastic wrap to prevent contamination is better than trying to preclean and disinfect properly around the buttons that tend to retain debris (see Figure 12-5). One can cover the heads of x-ray units and the control panels (Figure 12-7), and if the water at sinks is not controlled by elbow levers, foot pedals, or automatic devices, one can cover faucet handles with plastic bags (Figure 12-8).

Approaches to Precleaning and Disinfection

Surfaces to be disinfected first must be precleaned. Precleaning reduces the number of contaminating microorganisms and the blood or saliva present (referred to as bioburden) and facilitates action of the disinfecting chemical. Precleaning is an important step that one must not slight. The organic material in blood and saliva insulates microorganisms from contact with a disinfecting chemical and also may inactivate a portion of the active chemical in the disinfectant.

During the precleaning process, one may use regular soap and water, but use of a surface cleaner/disinfectant that contains detergents is best for the precleaning step and the disinfecting step. Using a disinfectant/cleaner for the precleaning step starts the killing process early and reduces the chances of spreading the contamination to adjacent surfaces. This (along with wearing heavy utility gloves, a mask, protective eyewear, and protective clothing) provides a little more protection to the person cleaning the surface. Water-based disinfectant-detergents (e.g., some synthetic phenolics, iodophors, and quaternary ammonium compounds—alcohols) solubilize organic materials such as blood and saliva and facilitate their removal. One also can use these same products in the disinfection step.

There are two approaches to precleaning and disinfection (see Procedure 12-2). One (using a liquid disinfectant/cleaner) is spray-wipe-spray and the other (using a disinfectant towelette) is wipe-discard-wipe. For spray-wipe-spray (Figure 12-9) spray the cleaner/disinfectant on the surface and wipe (preclean) the surface vigorously with a paper towel or gauze pad. Then respray the disinfectant/cleaner on the precleaned surface and let it remain moist for the longest contact time indicated on the disinfectant label (usually 10 minutes). If moisture remains, one should wipe it away with a paper towel. Some disinfectants are promoted as “one-step” products (i.e., spray and wipe). Although it is usually best to follow manufacturer’s directions on all products, it won’t hurt to use the one-step products in the two-step procedures (spray-wipe-spray). The two-step procedure becomes even more important should the postcleaning disinfecting contact time stated on the product label be shortened for some reason. If this is the case, at least the precleaning step will have removed/killed some of the microbes in the bioburden on the surface.

Do not store paper towels or gauze pads in a disinfectant and use as wipes to avoid spraying. Wet the towels or pads just before use. Paper towels may be held behind some surfaces to catch overspray, if desired.

An alternative to spray-wipe-spray is the wipe-discard-wipe procedure using disinfectant towelettes. Pull a towelette from its container and wipe (preclean) the surface. Then discard that towelette. Obtain another towelette and wipe (disinfect) the surface, let the surface remain wet for the prescribed time, and discard the towelette. Dry off the surface if necessary. When using containers of disinfectant towelettes, keep the lid closed when not in use to prevent evaporation of the alcohol. Also periodically invert the container to redistribute any settled liquid.

If it is difficult to remove all of the bioburden from a given surface, then consider protecting it with a surface cover during future use. This is usually better than attempting to brush it clean and risk spreading contaminations to nearby surfaces.

Unfortunately, one cannot determine the effectiveness of disinfecting surfaces. Thus performing the procedures carefully and using the disinfectant as described on the product label is important.

Characteristics of Disinfectants

There are four general types of antimicrobial chemicals.

The Centers for Disease Control and Prevention has categorized disinfectants based on their microbial spectrum of activity. This categorization follows and is described further in Table 12-2:

Labels on antimicrobial products can be confusing, but reading these labels carefully before using the product is very important. These labels commonly include the type of antimicrobial agent (active ingredients) and general properties such as the following:

The labels also commonly include the following:

No perfect disinfectant exists that will kill all types of disease-producing microorganisms rapidly, have no toxic properties, be unaffected by organic materials, be odorless, not cause any damage to any surface, and be economical. Nevertheless, several classes of disinfecting chemicals have gained wide use in dentistry and medicine. These classes are identified by the type of antimicrobial agents present in the product, which are listed on the product label as active ingredients (Table 12-3). Because M. tuberculosis var bovis is more difficult to kill than most other microorganisms, disinfectants with tuberculocidal activity are considered as strong disinfectants (see Chapter 11, Figure 11-1, Mycobacterium species). Stronger disinfectants are active against nonenveloped hydrophilic viruses also, as described in Table 12-4. Use of a water-based disinfectant is reported to provide better cleaning of biologic material such as blood than use of an alcohol-based disinfectant. For dental infection control, a water-based surface disinfectant that is EPA-registered and tuberculocidal (such as iodophors, phenolics, or chlorines) is appropriate if used as directed by the manufacturer and careful precleaning is performed.

Manufacturers of disinfectants must submit testing data on the antimicrobial activity and safety of their products to the EPA. If the data are consistent with claims stated on the product labeling and other requirements are met, the EPA registers the product. The U.S. Food and Drug Administration also must grant marketing clearance to liquid chemical sterilants/high-level disinfectants labeled for use on medical devices such as heat-sensitive dental items.

General Considerations

Some basic considerations for equipment decontamination exist. In general, one should try to prevent the equipment from becoming contaminated in the first place. If this is not possible, one should select heat sterilization first. If the equipment cannot be heat sterilized, then one should use a liquid sterilant or an appropriate disinfectant for decontamination. Following the manufacturer’s directions for preventing contamination or for cleaning, sterilization or disinfection of dental equipment is important.

One should use the following principles to reduce the spread of microbes from dental equipment used in the mouth that will penetrate soft tissue or tooth structure (Figure 12-10).

One should use the following approach to decontamination if the item will be used in the patient’s mouth but will not penetrate soft tissue or tooth structure (Figure 12-11).

One should use the following approach for items that are not used in the patient’s mouth (Figure 12-12).

Management of High-tech Equipment

New technologies are developed continually that aid the dental profession in treating patients. These technologies must be compatible with infection control or their use will be limited, but some technologies may present special infection control challenges, such as computers, cameras, and digital x-ray sensors.

For computers, one should avoid their contamination by performing hand hygiene before use. If this does not occur, recent studies have shown that the keyboards can be successfully decontaminated by using disinfectant wipes such as those containing quats. Also the same study showed that no damage occurred to the keyboards after 300 disinfecting procedures. Care should be taken that disinfectant wipes used should not contain excess fluid that might that might enter the base of the keyboard.

For 35-mm, video, and digital cameras, one should try to avoid their contamination. They are not designed to be disinfected. One should cover them with plastic sheeting or operate them only with clean hands.

Computer-aided design/computer-aided manufacturing devices (CAD/CAMS) use close-up intraoral pictures to design and manufacture restorations. These devices use a small camera lens on the end of a wire that transmits pictures from the patient’s mouth to a TV-type monitor. One should check with the manufacturer for proper decontamination of the camera and wire. One model has an outer removable prismatic device that slides over the camera lens, so the prism rather than the camera lens becomes contaminated. The prism can be sterilized in a dry heat sterilizer but not in a steam sterilizer, for the moist heat can damage the prism.

Digital radiography equipment needs special attention. This equipment uses intraoral sensors to provide a digital image that can be manipulated, viewed on a monitor, printed, or stored electronically. Because the sensors are reusable, one must handle them properly to prevent cross-contamination during subsequent use. One type of sensor, the charge-coupled device (CCD), is attached to a wire and should not be heat sterilized. Instead, one should cover the CCD with a plastic barrier that extends down the cable to prevent any contact with patient materials or contaminated hands. If the CCD does become contaminated, one may disinfect it by the spray-wipe-spray technique according to the manufacturer’s directions. Another type of digital x-ray sensor is the complementary metal-oxide semiconductor with active pixel sensors. This device is wired and should be treated with plastic barriers just like the CCD sensor. A third type of sensor, the photostimulable phosphor plate sensor, is wireless and is placed in the patient’s mouth much like a regular film packet. One must cover the device with a plastic barrier; it cannot become contaminated because it cannot be heat sterilized or chemically disinfected.

Aseptic Retrieval

If one stores supply items in bulk, such as a container of cotton rolls, one must use an aseptic retrieval system (rather than saliva-coated gloved fingers) to avoid contamination of unused items in the container. Providing sterile forceps (to retrieve the supply item) with the instruments needed for each patient is one approach to this problem (Figure 12-13). Storing supplies (or instruments) in drawers at chairside lends itself to cross-contamination of the drawer handle (if not covered or precleaned and disinfected) or of bulk items inside (if aseptic retrieval is not used).

Unit Dosing

The dental professional may protect supply containers, bottles, and tubes of materials used at chairside on more than one patient (multidose containers) with a surface cover for each patient or in some instances may preclean and disinfect these between patients. Many types of disposable supplies can be unit dosed, which means that the supplies are distributed or packaged in small numbers sufficient for care of just one patient and are placed at chairside before care begins. For example, a package may contain four cotton rolls, three cotton balls, two gauze pads, articulating paper, or whatever one anticipates for a single patient. Whatever is not used with a patient is discarded. Some supply items are unit dosed by the manufacturers, saving office staff time. Although unit dosing can solve some cross-contamination problems, unfortunately it can be expensive and wasteful if not organized properly.

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______1. Which of the following microbes are not killed by intermediate-level disinfectants?

______2. Which of the following types of antimicrobial agents should be used on floors?

______3. Which of the following antimicrobial agents should not be used for surface disinfection in dentistry?

______4. Which of the following agents is not tuberculocidal?

______5. What types of surfaces should be covered rather than disinfected?

______6. Why should disinfectants used on clinical contact surfaces in dentistry contaminated with blood or saliva have tuberculocidal activity?

______7. Liquid sterilants such as a glutaraldehyde should be used only on reusable items that can be submerged and are:

______8. One should not use ______________ as a surface cover.

______9. Use of a disinfectant-type cleaner to preclean a contaminated operatory surface:

______10. When can a liquid sterilant/high-level disinfectant achieve sterilization?