Sounds simple, doesn’t it? But achieving a goal of sterile instruments for use on all your patients actually is quite involved and requires the careful execution of specific procedures. Still, the reward for this hard work is the satisfaction in knowing that the considerable time, money, and effort spent will help ensure your patients’ safety. The complete process for instrument turn-around involves several procedures that can be divided into the following six steps.
(1) Transport and presoak
Gather the instruments, waste materials, and disposable items and transport them to the instrument processing room. Once there, discard the waste and disposable items. Be sure to check for any sharps that were not previously disposed of at chairside, carefully grasp them using cotton forceps or tongs, and place them in the sharps container.
If there is no time to clean the instruments immediately, soak them in the cleaning solution that will be used later for thorough cleaning. This will prevent drying of debris on the instruments, making instrument cleaning less challenging.
(2) Clean, rinse, and dry
Cleaning
Cleaning reduces the bioburden–the blood, saliva, dental materials, and microbes—on the instruments. The dental materials and the glycoproteins in blood and saliva can insulate microbes from the sterilizing agents and thereby inhibit the agents’ effectiveness.
When cleaning, avoid directly handling sharp instruments, and do not routinely handscrub any instruments. Safe instrument handling can be accomplished easily by using instrument cassettes. Cassettes house the instruments throughout the entire process and provide a container for the setups at chairside. If cassettes are not used, be sure to wear heavy-duty gloves when placing instruments into cleaning solutions.
Ultrasonic cleaners and automatic instrument washers accept cassettes or loose instruments in baskets or trays and provide safer alternatives to handscrubbing. Always use a basket or rack with ultrasonic cleaners to help reduce direct personal contact with the contaminated cleaning solution and to facilitate good cleaning action, which occurs up in the solution and not on the bottom of the tank. Load instrument washers following the manufacturer’s directions to help ensure adequate exposure of the instruments to the washing action of the spray arms. Some handpieces cannot be processed through an ultrasonic cleaner, so be sure to follow the manufacturer’s directions for cleaning and sterilization.
Rinsing
Some built-in ultrasonic cleaners include a drain and fill cycle to facilitate rinsing of the cleaned instruments. For countertop model ultrasonic cleaners, lift out the basket of instruments and rinse under a faucet, avoiding splashing. Most instrument washers have automatic rinse cycles.
The rinsing process is very important and is comparable to the rinsing done during handwashing. In both handwashing and instrument cleaning, the physical/mechanical action suspends the microbes from the surfaces of the hands or instruments, and the rinsing removes them.
Because rinsing washes off any rust inhibitors in the cleaning solutions, consider re-adding a rust inhibitor when carbon steel instruments are processed through a steam sterilizer.
Drying
Drying the instruments and cassettes before packaging them prevents the paper portion of packaging materials from becoming wet and possibly tearing when loading the packs into the sterilizer. If a dry heat or unsaturated chemical vapor sterilizer is used, any residual water on the instruments counteracts the rust-prevention aspect of these two sterilization processes.
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(3) Package
After cleaning, rinsing, and drying, check the completeness of the instrument setups and replace any missing, damaged, or broken items, and prepare to package them. Packaging the instruments and handpieces protects them from re-contamination after they are removed from the sterilizer–that is, during storage and transport to chairside.
Package
This instrument cassette is packed in a pouch to help protect the contents from re-contamination after sterilization.
Disposable items that can withstand the sterilization process can be added to the setup before packaging. The packaging material (e.g., paper/plastic peel pouches, sterilization wrap, paper bags, and nylon-type plastic bags) must be compatible with the sterilization method used. For example, if you place a paper/plastic peel pouch in a dry heat sterilizer, the plastic separates from the paper because the high temperature destroys that seal. Also, the plastic portion of some sterilization wraps will melt in a dry heat sterilizer. Do not package heavy or sharp items in paper bags because puncturing or tearing may occur. Paper bags are more appropriate for 2X2s, cotton rolls, or other non-sharp, lightweight items. In addition, avoid using cloth as an outer sterilization wrap because the cloth’s weave is not tight enough to provide an effective barrier to microbes.
Because instrument cassettes have holes in them to facilitate the cleaning process, the cassettes need to be wrapped or placed in pouches before sterilization to protect their contents from re-contamination after sterilization.
Sterility indicators vital
Remember that the Centers for Disease Control and Prevention (CDC) recommends placing a chemical indicator inside every package to help monitor the success of reaching adequate interior sterilizing conditions next to the surface of the instruments.¹ Also, if sterilization wrap or paper bags are used, and the internal chemical indicator cannot be seen from the outside of the package, another chemical indicator must be placed on the exterior of the package.¹ This offers visual documentation that the package has or has not been processed through a sterilizer. In addition, a spore test must be placed inside of a package for processing through the sterilizer at least once every week.¹
(4) Sterilize and dry
Although the instruments are clean, they still are contaminated with microbes that need to be killed before these instruments are used on another patient. Accomplish this by processing the instrument packages through a Food and Drug Administration (FDA)-cleared sterilizer, in one of three types: steam, dry heat, or unsaturated chemical vapor.
Steam sterilizer
The small office steam sterilizer comes in three basic models–gravity, pulse, and vacuum. These types are distinguished by how the air in the chamber is removed before the sterilization portion of the cycle begins. If the air is not removed, then sterilizing temperatures may not be reached.
• In the gravity steam sterilizer, the air is pushed out as the steam is generated.
• The pulse model uses a series of repeated sequences of steam flushes and pressure pulses to remove the air.
• Vacuum steam sterilizers activate a vacuum pump that removes the air before the steam is generated. Some models also have a post-sterilization vacuum cycle to help remove moisture created by the steam.
Although all steam sterilizers operate at about the same temperatures (e.g., 121?C or 134?C), each brand is somewhat unique in regard to appearance, controls, gauges/printouts, and drying cycles. Most sterilizers have cycles for wrapped instruments, unwrapped instruments, and rubber and plastics items. However, cycle times and temperatures vary slightly from one brand to another. Thus, following manufacturer’s directions is very important. This is because each model of sterilizer is cleared by the FDA based on specific times and temperatures shown to kill highly resistant bacterial spores.
In addition to causing the potential rusting of carbon steel items, steam sterilizers also leave items wet after the end of the sterilization portion of the cycle. Units with a post-sterilization vacuum cycle help alleviate this problem. Other units have drying cycles that pull in filtered air to facilitate drying. If packages are removed from steam sterilizers while still wet, microbes from the air, dust, oral spatter, and solid surfaces that contact the wet paper portion of packaging material will be wicked (drawn) through to the package interior, contaminating the package contents. Because wicking does not occur through dry packages, let the packages dry inside the sterilizer, then store the sterile packages away from sources of moisture.
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Dry heat sterilizer
The dry heat sterilizer operates at about 160?C, but the total cycle time (e.g., 60 to 90 minutes) after heat-up is longer compared to steam. This is because dry heat doesn’t penetrate as quickly as moist heat. On the other hand, carbon steel instruments won’t rust as they do in the steam sterilizer. Also, the instrument packages come out dry.
Unsaturated chemical vapor sterilizer
The unsaturated chemical vapor sterilizer operates at about the same temperature as a steam sterilizer (i.e., 134°C), but it uses a chemical solution instead of steam as the sterilizing agent. The active ingredient in the chemical solution is formaldehyde at a low level of 0.25%. The solution also contains alcohol, some other chemicals, and very little water. This low water content eliminates any rusting of carbon steel instruments, and the instrument packages come out dry.
One of the most critical aspects of the sterilization process with any type of sterilizer is the proper loading of the chamber, thereby ensuring ready access of all packages to the sterilizing agent. This is best accomplished by using a single layer of packages or cassettes, or by placing these items on their edges. Most sterilizers provide a rack for proper package placement.
(5) Distribute packages
Transport dry sterile packages to chairside for immediate use, or store them until needed. Dry sterile packages should hold their sterility for about 6 months, as long as the packaging material is not breached. However, the best way to manage the shelf life of these packages is to use event-related shelf life determination. This means that the instruments in packages are OK to use unless some event has occurred, tearing the packaging material or allowing it to become wet. To determine whether such a damaging event has occurred, carefully check the packaging material for tears or punctures before using the package. Because it can be difficult to determine whether a package has become wet after it dries again, be sure to store dry sterile packages away from all sources of water. The instruments in all damaged packages should be recleaned, repackaged, and resterilized.
(6) Monitor the process
Mechanically monitor each sterilizer load by documenting the time, temperature, and with steam sterilizers, the pressure. This is accomplished by observing printouts or gauge readings.¹ Also, chemical and biological monitoring should be performed,¹ as described in Step 3.
Further information on sterilization monitoring and what to do if a sterilization failure occurs can be found in the Infection Control Reports in the February and March 2008 issues of Dental Products Report.2,3
Proper processing paramount
Proper instrument processing is of utmost importance in providing patient safety. The six steps of instrument processing need to be performed correctly every time to provide sterility assurance.
Chris H. Miller, PhD, is Professor Emeritus of Oral Microbiology and Executive Associate Dean Emeritus at Indiana University School of Dentistry, Indianapolis. Reach him either at chmille@iupui.edu or c/o ewhite@advanstar.com.
References
1. CDC. Guidelines for infection control in dental health-care settings—2003. Available at: “cdc.gov/mmwr/preview/mmwrhtml/rr5217a1.htm”. Accessed May, 2008.
2. Miller CH. Instrumentally clean. Dent Prod Rep 2008;42(2):120.
3. Miller CH: When sterilization stops. Dent Prod Rep 2008;42(3):116.
Photos courtesy of Chris Miller, PhD.
Protection in the process
The following are a few additional CDC guidelines to help you avoid potential injury during instrument processing:
• Don’t use a liquid chemical sterilant or a high-level disinfectant like glutaraldehyde as a holding or soaking solution.
• Use a long-handled brush to keep the scrubbing hand away from sharp instruments during handscrubbing.
• Don’t reach into trays or containers holding or soaking sharp instruments that cannot be seen, such as sinks that have instruments immersed in soapy water.
• Use a strainer-type basket to hold sharp instruments in a sink. Remove the instruments using forceps.
• Wear PPE (such as gowns, masks, and heavy-duty gloves) when cleaning instruments to protect from possible splashes.
Source: Adapted from CDC Guidelines for infection control in dental health-care settings—2003.1