Steam sterilization (autoclaving) is the most dependable and economical process. It is the most widely used method for wrapped and unwrapped critical and semi-critical items that are not heat and/or moisture sensitive. To kill microorganisms, steam sterilization requires exposure of each item to direct steam contact at a specified temperature and pressure for a defined period of time. There are two basic types of steam sterilizers: gravity displacement and high-speed prevacuum.
The majority of tabletop sterilizers used in oral healthcare settings are gravity displacement sterilizers. 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. Errors in packaging items or overloading the sterilizer chamber can result in cool air pockets and sterilization failure.
High-speed 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. In comparison to gravity displacement, this technology allows for faster and more positive steam penetration throughout the entire load. Prevacuum sterilizers should be tested daily for adequate air removal (see Quality Assurance). Residual air in the chamber can lead to sterilization failure.2,3