| FAQ - Sterilization - Archived Through 2012
What is the best sterilizer to use for orthodontic instruments, including hinged instruments?
Typically, orthodontic practices utilize more than one type of sterilizer due to the variety of instruments and supplies used with orthodontic patients.
Because of the many advantages and disadvantages of each method of sterilization, OSAP is not in a position to recommend any one type of sterilizer. Each orthodontic practice must determine which methods of sterilization best meets the needs of their practice. Although dry heat sterilizers are often recommended, their use may not always be practical due to the prolonged process time required to sterilize instruments.
We can however, provide you with general information concerning the methods of sterilization that should help you determine which ones will meet your needs.
The Centers for Disease Control and Prevention's (CDC) Guidelines for Infection Control in
Dental Healthcare Settings provides the following information for each method of sterilization:
Sterilization Procedures. Heat-tolerant dental instruments usually are sterilized by 1) steam under pressure (autoclaving), 2) dry heat, or 3) unsaturated chemical vapor. All sterilization should be performed by using medical sterilization equipment cleared by FDA. The sterilization times, temperatures, and other operating parameters recommended by the manufacturer of the equipment used, as well as instructions for correct use of containers, wraps, and chemical or biological indicators, should always be followed. (1)
Steam Sterilization. Among sterilization methods, steam sterilization, which is dependable and economical, is the most widely used for wrapped and unwrapped critical and semi-critical items that are not sensitive to heat and moisture. Steam sterilization requires exposure of each item to direct steam contact at a required temperature and pressure for a specified time needed to kill microorganisms. Two basic types of steam sterilizers are the gravity displacement and the high-speed pre-vacuum sterilizer. (1)
The majority of tabletop sterilizers used in a dental practice are gravity displacement sterilizers, although pre-vacuum sterilizers are becoming more widely available. In gravity displacement sterilizers, steam is admitted through steam lines, a steam generator, or self-generation of steam within the chamber. Unsaturated air is forced out of the chamber through a vent in the chamber wall. Trapping of air is a concern when using saturated steam under gravity displacement; errors in packaging items or overloading the sterilizer chamber can result in cool air pockets and items not being sterilized. (1)
Pre-vacuum sterilizers are fitted with a pump to create a vacuum in the chamber and 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. Pre-vacuum sterilizers should be tested periodically for adequate air removal, as recommended by the manufacturer. Air not removed from the chamber will interfere with steam contact. If a sterilizer fails the air removal test, it should not be used until inspected by sterilizer maintenance personnel and it passes the test. Manufacturer's instructions, with specific details regarding operation and user maintenance information, should be followed. (1)
Unsaturated Chemical-Vapor Sterilization. Unsaturated chemical-vapor sterilization involves heating a chemical solution of primarily alcohol with 0.23% formaldehyde in a closed pressurized chamber. Unsaturated chemical vapor sterilization of carbon steel instruments (e.g., dental burs) causes less corrosion than steam sterilization because of the low level of water present during the cycle. Instruments should be dry before sterilizing. State and local authorities should be consulted for hazardous waste disposal requirements for the sterilizing solution. (1)
Dry-Heat 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 cost and being non-corrosive, it is a prolonged process and the high temperatures required are not suitable for certain patient-care items and devices. (1)
Dry-heat sterilizers used in dentistry include static-air and forced-air types. (1)
The static-air type is commonly called an oven-type sterilizer. Heating coils in the bottom or sides of the unit cause hot air to rise inside the chamber through natural convection.
The forced-air type is also known as a rapid heat-transfer sterilizer. Heated air is circulated throughout 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.
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 required for unwrapped sterilization cycles depends on the type of sterilizer and the type of item (i.e., porous or nonporous) to be sterilized. The unwrapped cycle in tabletop sterilizers is preprogrammed by the manufacturer to a specific time and temperature setting and can include a drying phase at the end to produce a dry instrument with much of the heat dissipated. If the drying phase requirements are unclear, the operation manual or manufacturer of the sterilizer should be consulted. If the unwrapped sterilization cycle in a steam sterilizer does not include a drying phase, or has only a minimal drying phase, items retrieved from the sterilizer will be hot and wet, making aseptic transport to the point of use more difficult. For dry-heat and chemical-vapor sterilizers, a drying phase is not required. (1)
Unwrapped sterilization should be used only under certain conditions: 1) thorough cleaning and drying of instruments precedes the unwrapped sterilization cycle; 2) mechanical monitors are checked and chemical indicators used for each cycle; 3) care is taken to avoid thermal injury to DHCP or patients; and 4) items are transported aseptically to the point of use to maintain sterility. Because all implantable devices should be quarantined after sterilization until the results of biological monitoring are known, unwrapped or flash sterilization of implantable items is not recommended. (1)
Critical instruments sterilized unwrapped should be transferred immediately by using aseptic technique, from the sterilizer to the actual point of use. Critical instruments should not be stored unwrapped. Semi-critical instruments that are sterilized unwrapped on a tray or in a container system should be used immediately or within a short time. When sterile items are open to the air, they will eventually become contaminated. Storage, even temporary, of unwrapped semi-critical instruments is discouraged because it permits exposure to dust, airborne organisms, and other unnecessary contamination before use on a patient (260). A carefully written protocol for minimizing the risk of contaminating unwrapped instruments should be prepared and followed. (1)
The authors of Practical Infection Control In Dentistry also state that orthodontic pliers and cutters require special attention and are best sterilized with dry heat units. The instruments can be placed in an ultrasonic bath containing a rust inhibitor solution before sterilization. The instruments should then be bagged and sterilized immediately after retrieval from the ultrasonic bath. Pliers and cutters should be lubricated with a silicone lubricant once a week. (2)
Surgical milk may also be used to lubricate instruments prior to sterilization. This agent is a concentrated pre-autoclave dip that extends the life of valuable instruments. The non-toxic, odor-free formula inhibits rust and lubricates all hinged instruments. Information on this product may be viewed at:
Keep in mind that regardless of the method of sterilization used, hinged instruments should be processed open and unlocked.
Because Orthodontics have unique challenges (e.g. orthodontic wires, pliers, cutters, brackets, bands, elastics, orthodontic appliances, etc.) we would like to also refer you to the American Association of Orthodontics for the most current infection control recommendations that address the specific needs of the orthodontic practice.
You may contact The American Association of Orthodontics at:
American Association of Orthodontists
401 North Lindbergh Boulevard
St. Louis, MO 63141-7816
Email address: email@example.com.
(1) The Centers for Disease Control and Prevention's (CDC) Guidelines for Infection Control in
Dental Healthcare Settings:
(2) Practical Infection Control In Dentistry, 2nd. edition. By Cottone, Terezhalmy, and Molinari.
Publisher, Williams & Wilkins. Copyright 1996.