Cleaning is the physical removal of debris. It has two major effects. First, it reduces the number of micro-organisms present. Second, it removes organic matter, such as blood, tissue and other debris that may interfere with sterilization or disinfection. In some instances, cleaning is all that is necessary. Most often, however, it is the preliminary step before sterilization or disinfection. In these instances, it is referred to as pre-cleaning. Pre-cleaning is essential, because sterilization and disinfection procedures may not be effective if items have not been cleaned first.
Sterilization is the process that destroys all types and forms of micro- organisms including viruses, bacteria, fungi and bacterial endospores. Major methods of sterilization include the use of steam under pressure (steam autoclave), dry heat and unsaturated chemical vapour.
Disinfection is generally less lethal to pathogenic organisms than sterilization. Three levels of disinfection have been differentiated, depending on the type and form of micro-organisms destroyed.
The effectiveness of any disinfection procedure is influenced by several factors, including the type and number of micro-organisms present, the concentration and length of exposure to the disinfecting agent and the amount of organic matter or other debris present on the item being disinfected. For disinfecting agents to be effective, it is important that they are used according to the manufacturer's instructions.
The major factor determining whether an item must be sterilized, disinfected or simply cleaned is how it is used.
Items To Be Sterilized or Disinfected :-
Items To Be Sterilized or Disinfected/Cleaned
Concerns about the transmission of infectious agents, such as the Hepatitis B virus (HBV) and the Human Immuno deficiency Virus (HIV) have caused us all to be more aware of the need to adequately sterilize and disinfect instruments and other equipments to protect ourselves and our patients.
A number of sterilization methods are available for heat tolerant dental instruments. These include use of steam under pressure (steam autoclave), dry heat or unsaturated chemical vapor. The duration of sterilization, temperatures and other operating parameters recommended by the equipment manufacturer should be used. Additionally, instructions for use of correct containers, wraps and chemical or biological indicators should always be followed.
Heat sterilization methods (steam autoclave, dry heat and unsaturated chemical vapor) are preferred for all equipment that can withstand high temperatures for several reasons:
Liquid chemical disinfectants/sterilants should be used only when heat will damage an item.
Among sterilization methods, steam sterilization is the most widely used for wrapped and unwrapped critical and semicritical items that are not sensitive to heat and moisture. When using an autoclave, the load must be placed so that steam can circulate freely around each item, because steam must be able to reach all instrument surfaces at a required temperature and pressure for a specified time in order to kill all microorganisms and achieve sterilization. Be sure to follow the autoclave manufacturer's operating instructions
The majority of tabletop sterilizers used in dental practice are gravity displacement sterilizers, although prevacuum sterilizers are becoming widely available. Prevacuum sterilizers are fitted with a pump to create a vacuum in the chamber and to ensure air removal from the sterilizing chamber before the chamber is pressurized with steam. Relative to gravity displacement, this procedure allows faster and more positive steam penetration throughout the entire load.
An autoclave is a self locking machine that sterilizes with steam under pressure, achieved by the high temperature. Autoclaves are the universally accepted means for sterilization.
It is generally accepted that an autoclave chamber must reach at least 121°C at 15 Psi for a minimum of 30 minutes to ensure adequate sterilization. Sterilization time may vary depending on the quantity and density of items in the autoclave chamber. Overloading must be avoided.
Instruments and materials for sterilizing in the autoclave are usually enclosed in the muslin wrappers as surgical packs. These packs should be porous to allow steam to penetrate and reach the instruments.
The autoclave is employed for the sterilization of the instruments, extraction forceps, surgical instruments, explorers etc. The sterilized instruments should remain wrapped until next used.
Autoclave indicator tape and autoclave indicator bags change colour when the proper temperature has been reached. While the indicator tape quick-check should be conducted with every load, it must be supplemented periodically by use of a biological indicator (such as Bacillus spores) buried in the center of a load to confirm the sterilization.
Dry heat is used to sterilize materials that might be damaged by moist heat (e.g. burs and certain orthodontic instruments). Although dry heat has the advantages of low operating costs and being non-corrosive, it is a prolonged process and the high temperatures required are not suitable for certain patient care items and devices with temperatures ranging from 300 degrees F (149 degrees C) and upward can be used for sterilization.
Dry heat sterilizers used in dentistry include static-air and forced-air types. The static-air type is commonly called an oven-type sterilizer. The forced-air type is also known as a rapid heat transfer sterilizer. Heated air is circulated through the chamber at a high velocity, permitting more rapid transfer of energy from the air to the instruments, thereby reducing the time needed for sterilization compared to the oven-type sterilizer.
Unsaturated chemical vapour sterilization involves heating a chemical solution of primarily alcohol with formaldehyde in a pressurized chamber. This method of sterilization is ideally suited to carbon steel instruments (e.g. dental burs) because the low level of water present during the cycle results in less corrosion than might be expected with steam sterilization. Instruments must be dry before sterilization. Follow the manufacturer's instructions.
An unwrapped sterilization cycle (sometimes called flash-sterilization) is a method of sterilizing patient care items for immediate use. Critical and semi- critical items that have been sterilized unwrapped should be transferred immediately, using aseptic technique for the ultimate use. The unwrapped sterilization cycle in tabletop sterilizers is usually preprogrammed by the manufacturer to a specific time and temperature setting.
Thorough cleaning and drying of instruments precedes the unwrapped cycle. Mechanical monitors are checked and chemical indicators are used for each cycle. Care is taken to avoid thermal injury to dental workers and patients.
Items are handled and transported aseptically to the point of use to maintain sterility. As implantable devices should be quarantined after sterilization until the results of biological monitoring are known, unwrapped or flash sterilization of implantable devices is not recommended.
Liquid chemical germicides: Heat-sensitive critical and semicritical instruments and devices can be sterilized by immersing them in liquid chemical germicides. However, items sterilized in this manner can require approximately 12 hours of complete immersion.
Additionally items sterilized in this manner must be rinsed with sterile water to remove any toxic or irritating residues, handled using sterile gloves and dried with sterile towels, delivered to the point of use in an aseptic manner and then used immediately.
Because of these limitations, they are almost never used to sterilize instruments. Rather, these chemicals are more often used for high-level disinfection of heat-sensitive semicritical instruments and devices. Shorter immersion times (12-90 minutes) make high-level disinfection more practical than sterilization; however, instruments and devices disinfected in this manner must still be handled as if sterile (e.g. rinsed with sterile water, dried with sterile towels, etc.) and used immediately.
Chemical sterilants (e.g. glutaraldehyde, peracetic acid, hydrogen peroxide) are powerful, sporicidal chemicals and are highly toxic. Instruments can be sterilized by placing them in a 2% solution of glutaraldehyde for 6-10 hours. The chemical sterilants must only be used according to manufacturer's instructions and for those applications indicated on their label. Misapplications include use as an environmental surface disinfectant or instrument holding solution.
Alcohols are effective as skin antiseptics.Usually a 50% to 80% ethyl alcohol solution is recommended.
In general, use of heat-sensitive semi- critical items that must be processed with liquid chemical germicides is discouraged; heat-tolerant or disposable alternatives are available for the majority of such items.
Ethylene oxide gas (ETG): Low temperature sterilization with ETG has been extensively used in larger health care facilities. However, extended sterilization times of 10-48 hours and potential hazards to patients and the dental team that require stringent health and safety requirements make this method impractical for the private-practice setting.
Bead sterilizers: Historically, bead sterilizers have been used in dentistry to sterilize small metallic instruments (e.g. endodontic files). This method employs a heat transfer device. The media used are glass beads or salt and the temperature achieved is 220°C.
The method empolys submersion of small instruments such as endodontic files and burs into the beads; they are sterilized in 10 seconds provided they are clean.
The intended use of the patient-care item should determine the recommended level of disinfection. Dental practices should follow the product manufacturer's directions regarding concentrations and exposure time for disinfectant activity relative to the surface to be disinfected.
Dental practitioners should process all instruments in a designated central processing area to ensure quality control and safety. The central processing area should be divided into sections for
Use mechanical, chemical and biological monitors according to the manufacturer's instructions to ensure the effectiveness of the sterilization process.
Monitor each load with mechanical (e.g. time, temperature and pressure) and chemical indicators. Place a chemical indicator on the inside of each package. If the internal indicator is not visible from the outside, also place an exterior chemical indicator on the package. Do not use instrument packs if mechanical or chemical indicators indicate inadequate processing.
Monitor sterilizers at least weekly by using a biological indicator with a matching control (i.e. biological indicator and control from same lot number). Use a biological indicator for every sterilizer load that contains an implantable device. Verify results before using the implantable device, whenever possible.
Maintain sterilization records (i.e. mechanical, chemical and biological).
In the dental office, the surface contamination can occur during patient care. Certain surfaces especially the ones touched regularly during patient care (e.g. light handles, unit switches and drawer knobs can serve as reservoirs of microbial contamination). These surfaces can be divided into clinical contact surfaces and house keeping surfaces.
Clinical contact surfaces can be directly contaminated from patient materials either by direct spray or spatter generated during dental procedures or by contact with dental professionals gloved hands. These surfaces can subsequently contaminate other instruments, devices, hands or gloves.
Examples of such surfaces include:-
To protect the laboratory personnel, impressions, gypsum casts, fixed and removable prosthesis, wax rims and bite registration records should be appropriately disinfected before sending them to the dental laboratory.
Dental prosthesis, impressions, orthodontic appliances and other prosthodontic materials (e.g. occlusal rims, temporary prosthesis, bite registrations) should be thoroughly rinsed under gentle running water to remove blood, saliva or debris.
The disinfection can be done by a short-term immersion in 0.5% or 1% sodium hypochlorite. In addition, immersion in glutaraldehydes, povidone-iodine diluted in water or halogenated phenol has no apparent effect on the dimensional stability of rubber materials.
The best time to clean and disinfect the impressions, prosthesis or appliances is as soon as possible after removal from the patients mouth, before drying of blood and saliva.
The extracted teeth should either be disposed or should be used for educational purpose.
The majority of blood contamination in dentistry result from spatter during dental procedures using rotary or ultrasonic instrumentation. Although no evidence supports that HBV, HCV or HIV have been transmitted from a housekeeping surface, prompt removal and surface disinfection of an area contaminated by either blood or OPIM are appropriate infection-control practices.
Carpeting is more difficult to clean than non- porous hard- surface flooring and it cannot be reliably disinfected, especially after spills of blood and body substances. Cloth furnishings pose similar contamination risks in areas of direct patient care and places where contaminated materials are managed (e.g. dental operatory, laboratory or instrument processing areas). For these reasons, use of carpeted flooring and fabric-upholstered furnishings in these areas should be avoided.
Dental unit waterlines (i.e. narrow-bore plastic tubing that carries water to the high-speed handpiece, air/water syringe and ultrasonic scaler) may become colonized with micro-organisms, including bacteria, fungi and protozoa. These micro-organisms colonize and replicate on the interior surfaces of the waterline tubing and form a biofilm, which serves as a reservoir that can amplify the number of free-floating (i.e. planktonic) micro-rganisms in water used for dental treatment and exhibit limited pathogenic potential for immunocompetent persons.
Patient material (e.g. oral microorganisms, blood and saliva) can enter the dental water system during patient treatment hence it is necessary to flush out the patient material that might have entered the turbine, air and waterlines.
Multiple semicritical dental devices that touch mucous membranes are attached to the air or waterlines of the dental unit. Among these devices are high and low-speed handpieces, prophylaxis angles, ultrasonic and sonic scaling tips, air abrasion devices and air and water syringe tips. These devices have the potential for retracting oral fluids into their internal compartments. Restricted physical access limits their cleaning. This indicates that retained patient material can be expelled intraorally during subsequent uses.