Chapter 21 Sterilization and Disinfection

Disadvantages of Chemical Vapor Sterilization

Residual chemical vapors containing formaldehyde and methyl alcohol may be released when the chamber door is opened at the end of the cycle These vapors can temporarily leave an unpleasant odor in the area and may be irritating to the eyes

Holding Solution (Cont.)

The container must have a lid and must be labeled with: -A biohazard label (because of the contaminated instruments) -A chemical label (because of the cleaner/detergent) -The holding solution should be changed at least twice daily, and even more frequently if it becomes clouded -Remember, a holding solution is necessary only when contaminated instruments cannot be processed immediately

Instrument-Processing Area (Cont.)

-A deep sink should have hands-free control for instrument rinsing and (if space permits) a foot-operated or other hands-free trash receptacle -The flooring should be an uncarpeted, seamless, hard surface -The size, shape, and accessories of the instrument-processing area vary among dental offices

Contaminated Area

-All soiled instruments are brought into the contaminated area, the initial receiving area, where they are held for processing -disposable items that have not already been discarded in the treatment room are removed from the instrument tray and disposed of as contaminated waste -Thorough cleaning should be done before all disinfection and sterilization processes -Removal of all debris and organic materials (e.g., blood and saliva) -The contaminated area contains clean protective eyewear and utility gloves, counter space, a sink, a waste disposal container, holding solution, an ultrasonic cleaner, an eyewash station, and supplies for wrapping of instruments before sterilization

Forced Air Sterilizers

-Also called the rapid heat transfer sterilizers -Circulate the hot air throughout the chamber at a high velocity -This action permits rapid transfer of heat energy from the air to the instruments, reducing the time needed for sterilization -Exposure time in a forced air sterilizer, after the sterilizing temperature has been reached, ranges from 6 minutes for unpackaged items to 12 minutes for packaged items

Biologic Monitoring

-Biologic monitoring (spore testing), is the only way to determine whether sterilization has occurred and all bacteria and endospores have been killed -The CDC, American Dental Association, and Office of Safety and Asepsis Procedures Research Foundation recommend at least weekly biologic testing of sterilization equipment -Several states also require routine biologic checks at weekly, monthly, or cycle-specific intervals, such as spore testing every 40 hours of use or every 30 days

Classification of Instruments Non-Critical

-Contact only intact skin -Low risk of infection transmission -Cleaned and processed with EPA-registered intermediate- or low-level disinfectant

Drying, Lubrication, and Corrosion Control

-Instruments and burs made of carbon steel will rust during steam sterilization -Rust inhibitors such as sodium nitrate and commercial products can be used to help reduce rust and corrosion -An alternative to a rust inhibitor is to dry the instrument thoroughly with the use of dry heat or unsaturated chemical vapor sterilization (discussed later), which does not cause rusting

Sterilization Monitoring

-It is critical that dental instruments be properly sterilized -Because microorganisms cannot be seen with the naked eye, the major difficulty in sterilization is determining when an item is sterile -Currently, three forms of sterilization monitoring are used: Physical, chemical, and biologic

Process Integrators

-Placed inside instrument packages -They respond to a combination of pressure, temperature, and time -Process integrators are also known as multiparameter indicators -All sterilization factors are integrated The advantage of placing integrators inside each package is that penetration of the packaging by the sterilizing agent is ensured

Instrument-Processing Area

-Should be centrally located in the office to allow easy access from all patient care areas -Dedicated only to instrument processing -Physically separated from operatories and laboratory -Not be part of a common walkway -Needs good air circulation -Large enough to accommodate all equipment and supplies -The area should not have a door or windows that open to the outside because dust may enter the area -Multiple outlets and proper lighting, water, and an air line and a vacuum line for flushing high-speed handpieces

Sterilization Failures

-Sterilization may fail when direct contact for the correct time between the sterilizing agent (chemical or steam) and all surfaces of the items being processed is insufficient -Several factors can cause the sterilization process to fail, including improper instrument cleaning or packaging and sterilizer malfunction

Advantages of Unsaturated Chemical Vapor Sterilization

-The major advantage of the chemical vapor sterilizer is that it does not rust, dull, or corrode dry metal instruments -The low water content of the vapor prevents destruction of items such as endodontic files, orthodontic pliers, wires, bands, and burs -A wide range of items can be sterilized routinely without damage -Other advantages include the short cycle time and the availability of a dry instrument after the cycle

Ethylene Oxide Sterilization

-The use of ethylene oxide gas is a recognized method of sterilization -Sterilizes at the lowest temperatures, which is an advantage for plastic and rubber items that would melt in heat sterilizers -Requires 2 to 3 hours at 120 F -Ineffective on wet items -Toxicity is possible if the gas is not handled properly

7 Steps for Instrument Processing

-Transport: Cleaning -Packaging -Sterilization -Storage -Delivery -Quality

Sterilization of Unwrapped Instruments

-An unwrapped cycle (sometimes called flash sterilization) is a method for sterilizing unwrapped patient care items for immediate use -The time for unwrapped sterilization cycles depends on the type of sterilizer and the type of item (i.e., porous or nonporous) to be sterilized -Unwrapped sterilization should be used only under certain conditions

Packaging Instruments

-Before sterilization, the instruments should be wrapped or packaged to protect them from becoming contaminated after sterilization -When instruments are sterilized without being packaged, they are exposed to the environment as soon as the sterilizer door is opened -They can be contaminated by aerosols in the air, dust, improper handling, or contact with nonsterile surfaces -Additional advantage to packaging instruments is they can be grouped into special setups, such as crown/bridge, amalgam, prophylactic, or composite

About Ultrasonic Cleaning Solutions

-Do not use other chemicals such as plain disinfectants in the ultrasonic cleaner -Some disinfectants can "fix" the blood and debris on the instruments. -Specific ultrasonic solutions are available for the removal of difficult materials such as cement, tartar, stains, plaster, and alginate -Refer to the instructions of the ultrasonic unit's manufacturer regarding the specific solution to be used

Handpiece Flushing Techniques

-Flushing the handpiece is the best way to remove debris from the head -To flush a dental handpiece: Attach a pressurized handpiece cleaner to the intake tube of the handpiece (where the air passes through) -Flush the head of the handpiece to remove debris -Blow out the handpiece using compressed air to remove debris before sterilization

Hand Scrubbing

-Hand scrubbing is the least desirable method of cleaning instruments because it requires direct hand contact with the contaminated instrument

Handpiece Sterilization

-High-speed dental handpieces rotate at speeds up to 400,000 revolutions per minute (rpm) -Blood, saliva, and tooth fragments, as well as restorative materials, may lodge in the head of the handpiece, where they may be retained and transferred to another patient -Dental handpieces must be properly cleaned and heat-sterilized

Holding Solution

-If instruments cannot be cleaned immediately after a procedure, they should be placed in a holding solution to prevent the drying of blood and debris on the instruments -The holding solution may be any noncorrosive liquid A commercial enzymatic solution that partially dissolves organic debris may be used -Dishwasher detergent also makes a good holding solution because it is low-cost, low-foaming, and readily available -It is neither cost-effective nor desirable to use a disinfectant alone as a holding solution

Testing the Ultrasonic Cleaner

-If you notice that the instruments are not being cleaned completely with processing in the ultrasonic cleaner, the unit may not be functioning properly -To determine whether the ultrasonic cleaner is working properly, hold a 5×5-inch sheet of lightweight aluminum foil vertically (like a curtain) half-submerged in fresh, unused solution -Run the unit for 20 seconds, then hold foil up to the light -Surfaces that were submerged should be evenly marked with a tiny pebbling effect over the entire surface -An area without pebbling of more than ½ inch indicates a problem with the unit, and it needs to be serviced by the manufacturer

Automated Washers/Disinfectors

-Look and work similar to a household dishwasher -Must be approved by the U.S. Food and Drug Administration -Use a combination of very hot recirculating water and detergents to remove organic material -After washing, the instruments are automatically dried -These units are classified as thermal disinfectors because they have a disinfecting cycle that subjects the instruments to a level of heat that kills most vegetative microorganisms -Instruments processed in an automatic washer/disinfector must be wrapped and sterilized before use on a patient

Filtration and Monitoring of Chemical Vapors

-Newer sterilizers are equipped with a special filtration device that further reduces the amount of chemical vapor remaining in the chamber at the end of the cycle -Older models can usually be retrofitted -Formaldehyde monitoring badges, similar to radiation monitoring devices, are available for employees

Handpiece Sterilizing Techniques

-Only steam sterilization and chemical vapor sterilizers are recommended because sterilization temperatures should not exceed 275º F (135º C) -Handpieces should be packaged in bags, wraps, or packs to protect them from contamination before use -Never run a handpiece "hot" out of the sterilizer, and avoid rapid cool-downs, such as running the handpiece under cold water -If handpieces need to be cooled quickly after sterilization, use an air fan to blow room-temperature air over them

Ultrasonic Cleaning Solutions

-Only use ultrasonic solutions that are specially formulated for use in the ultrasonic cleanerSome ultrasonic cleaning products have enzyme activity -Other ultrasonic cleaning products have antimicrobial activity, which reduces the buildup of microbes in the solutions with repeated use -Antimicrobial activity does not disinfect the instruments; it merely prevents the microorganisms from multiplying

Dry Heat Sterilization

-Operates by heating air and transferring that heat from the air to the instruments -Requires higher temperatures than does steam or chemical vapor sterilization -Dry heat sterilizers operate at temperatures up from 300F.Time: 60min. At 340 F. -Advantage of dry heat is that the instruments will not rust if they are thoroughly dry before being placed in the sterilizer -There are two types of dry heat sterilizers: Static air and forced air

Process Indicators

-Process indicators (external) are placed outside the instrument packages before sterilization -Process indicators simply identify instrument packs that have been exposed to a certain temperature; they do not indicate duration or pressure -Process indicators are useful in distinguishing between packages that have been processed and those that have not

Workflow Pattern

-Regardless of the size or shape of the instrument-processing area, four basic areas govern the pattern of workflow -Processing of instruments should proceed in a single loop, from dirty to clean to sterile to storage, without ever "doubling back" -If the instrument-processing area is small, you can use signs that read: -Contaminated items only -Precleaning area -Cleaned items only -Sterile items only

Static Air Sterilizers

-Similar to an oven -Heating coils are on the bottom of the chamber, and the hot air rises inside by way of natural convection -Heat is transferred from the static (nonmoving) air to the instruments in 1 to 2 hours -Disadvantages include amount of time it takes and errors due to incorrect processing time -The wrapping material must be heat resistant

Liquid Chemical Sterilants

-Some types of plastics, such as some rubber dam frames, shade guides, and x-ray film-holding devices, are damaged by heat sterilization -A liquid sterilant such as 2.0% to 3.4% glutaraldehyde must be used for sterilization of these items -Glutaraldehyde requires 10 hours of contact time; anything less than 10 hours is disinfection, not sterilization -Be sure you have an MSDS for these products

Methods of Sterilization

-Steam Autoclave -Dry Heat -Chemical Vapor -Ethylene Oxide -Rapid Heat Transfer -Immersion (Disinfectant/ Sterilization)

Steam Autoclave Sterilization

-Sterilization by steam under pressure. -Steam sterilization involves heating water to generate steam, producing a moist heat that rapidly kills microorganisms -It is actually the heat, not the pressure, that kills the microorganisms -Time - 15 min at 250 F Wrapped -Time - 3 min at 270 F Unwrapped

Packaging Materials

-Sterilization packaging materials and cassettes are medical devices and therefore must be FDA-approved -It is of critical importance to use only products and materials that are labeled as "sterilization" packaging -Never substitute products such as plastic wraps, paper, or zipper-lock freezer bags that are not registered for this purpose -Specific types of packaging material are available for each method of sterilization

Ultrasonic Cleaning

-Used to loosen and remove debris from instruments -Reduces the risk of cuts and punctures to the hands during the cleaning process -Puncture-resistant utility gloves, a mask, protective eyewear, and a protective gown should always be worn when the ultrasonic cleaner is being used -Keep a set of tongs near the ultrasonic unit; these can be used to remove instruments after the cleaning cycle has been completed

Hand Scrubbing Precautions

-Wear PPE -Clean only one or two instruments at a time -Use only a long-handled brush, preferably one with a hand guard or wide surface -Keep items above the waterline; fully immersing them in a basin of soapy water interferes with one's ability to see the sharp ends -Allow instruments to air-dry or carefully pat them with thick toweling -Never rub or roll instruments while they are in a towel because of the risk of accidental injury

Care of the Ultrasonic Cleaner

-When the solution is being changed, the inside of the pan and lid should be rinsed with water, disinfected, rinsed again, and dried -All PPE should be worn while solutions are being changed in the ultrasonic cleaner

Ultrasonic Cleaner (Cont.)

-Works by producing sound waves beyond the range of human hearing -Sound waves, which can travel through metal and glass containers, cause cavitation (formation of bubbles in liquid) -Bubbles burst by implosion -Instruments should be processed in the ultrasonic cleaner until they are visibly clean -Time varies from 5 to 15 minutes, depending on amount and type of material on the instruments and the efficiency of the ultrasonic unit

Preparation and Packaging Area

-cleaned instruments and other dental supplies should be inspected, assembled into sets or trays, and wrapped or placed in packages for sterilization -The preparation and packaging area should consist of counter space and storage space for sterilized instruments, fresh disposable supplies, and prepared trays or instrument cassettes -Clean instruments are not sterile and could harbor pathogens -Instruments must be packaged and sterilized before they are used on a patient

Physical Monitoring

-involves looking at the gauges and readings on the sterilizer and recording temperatures, pressure, and exposure time -Although correct readings do not guarantee sterilization, an incorrect reading is the first signal of a problem -Remember that the reading reflects the temperature in the chamber, not inside the pack

Biologic Indicators

Also known as spore tests, biologic indicators (BIs) are vials or strips of paper that contain harmless bacterial spores (which are highly resistant to heat) Three BIs are used in testing: •Two BIs are placed inside instrument packs, and the sterilizer is operated under normal conditions•The third strip is set aside as a control -After the load has been sterilized, all BIs are cultured -if the spores are killed (a negative culture), the sterilization cycle was successful -The culturing of the spore test is usually handled with the use of a mail-in monitoring service

Unsaturated Chemical Vapor Sterilization

Chemical vapor sterilization is uses (alcohol, formaldehyde, ketone, acetone, and water) is used instead of water to create a vapor for sterilization Time: 20min at 270 f wrapped or unwrapped

Classification of Instruments

Critical instruments: •Items used to penetrate soft tissue or bone•Greatest risk of transmitting infection and must be sterilized by heat•Ex: scalpels, blades, burs, chisel, scaler, etc. Semicritical instruments: •Touch mucous membranes or nonintact skin•Lower transmission risk•Sterilized by heat or receive minimum high-level disinfection if not heat tolerant•Ex: plastic handled items, x-ray film holders, amalgam carriers, HVE tips, etc.

Steam Autoclave Operation Cycles

Dental office steam sterilizers usually operate in four cycles: -Heat-up cycle -Sterilizing cycle -Depressurization cycle -Drying cycle

Precleaning and Packaging Instruments

Instruments may be precleaned in one of three ways: Hand scrubbing Ultrasonic cleaning Instrument-washing machine

Chemical Monitoring

Involves the use of a heat-sensitive chemical that changes color when exposed to certain conditions There are two types of chemical indicators: •Process indicators •Process integrators

Flash Sterilization (Rapid Heat Transfer)

Rapid, or "flash," sterilization of dental instruments is accomplished by means of rapid heat transfer, steam, and unsaturated chemical vapor Used only on instruments that are placed in the chamber unwrappedOnly for instruments that are to be promptly used on removal from the sterilizer Sterilizes at the highest temp. of all methods. Time: 6mins at 375 f (Cycle 1)

Pressure, Temperature,and Time

The three major factors in chemical vapor sterilization are: -Pressure, which should measure 20 psi -Temperature, which should measure 131º C (270º F) -Time, which should measure 20 to 40 minutes

Limitations of Process Integrators

They do not indicate sterility and are not a replacement for biologic monitoring

Intermediate- level disinfection

inactivates mycobacterium tuberculosis and destroys all less resistant organisms such as Hepatitis B, HIV.

Low level disinfectant

ineffective against Mycobacterium Tuberculosis and should be used for only household level disinfectant in the dental office.

Sterilization

process that inactivates all microbial life, bacterial spores, viruses, bacteria and fungi.

Disinfection

process that kills disease causing microorganisms but not necessarily all microbial life.

High-level disinfection

process that kills some but not all bacterial endospores and inactivates Mycobacterium Tuberculosis

Precleaning

reduces the amount of microorganisms that are present by physically removing debris.