Sterile Storage

Sterility of dental materials, instruments, and supplies is much harder to maintain than it is to achieve. There is little value in precise sterilization procedures if instruments are contaminated upon completion of the process. Items must be dry before they are handled or stored. The time required for drying depends on the type of packs in the load and the sterilizing agent used. Freshly sterilized items are never placed on metal or cold surfaces. Packages become damp from the condensation that occurs and become contaminated.

All sterile supplies, including sterile reusable dental items, must be stored in a manner that will preserve their sterility until used. The following factors affect this process:

Environmental conditions including cleanliness? proper ventilation, and control of excess heat and humidity are important.

The location where sterile supplies are stored should not be in a manner that may contribute to the increased possibility of contamination. Figure 10-9 shows an acceptable sterile storage cabinet containing sterilized packs and instruments.

Sterile items should not be stored in patient treatment or decontamination areas unless they are protected by enclosures, such as drawers or cabinets.

Sterile and clean patient treatment items may be stored in the same drawers or cabinets, as long as there is no possibility of nonsterile items being used inadvertently when sterility is required.

Sterile items should not be stored with items not intended for clinical use (e.g., office and cleaning supplies).

Items must not be stored on the deck, under sinks, in window sills, adjacent to heating and air conditioning vents, or in any area where undetected contamination may occur.

When storing sterilized items, arrange them according to expiration date, placing items with later dates toward the rear. Check supplies periodically to determine any need for resterilizing. Items must be resterilized if the wrapper becomes wet, if the pack touches the deck, if there is any question of contamination, or if the safe storage period has expired.

STERILIZATION METHODS

Because of the composition of many of the items used in dentistry, no single sterilization method is

Figure 10-9.\Sterile storage cabinet.

suitable for all dental items. As a basic dental assistant, you will need to know several approved methods of sterilization.

Steam Heat Sterilization

Steam under pressure (saturated steam) is the most effective means of sterilization for almost all items used in dentistry. To achieve sterility, moist heat under pressure must come in contact with all surfaces of all items for the appropriate length of time. To effectively sterilize items using saturated steam, the temperature of the steam throughout the load must be high enough to destroy the most resistant micro-organisms in the time allotted for sterilization. For example, some spores can withstand temperatures above the normal boiling point of water (212F or 100C); so the relationship of temperature to spore killing power is critical. Steam temperature and exposure time, not pressure, are crucial components of this process. Pressure is used only to raise the temperature of the steam and, in itself, has nothing to do with microbial killing action. At 15 pounds per square inch (psi), the boiling point increases to 121C (250F), a temperature at which all known organisms are killed.

In addition to the high temperature, steam must be saturated so that it will quickly release heat through condensation when it comes into contact with a cool object. Sterilization will not occur unless all air is eliminated from the chamber at the beginning of the process and periodically throughout sterilization. The packaging of supplies and loading of the sterilizer must be done so that steam comes in contact with all areas or surfaces of the items being sterilized.

Flash sterilization is defined as the sterilization of unwrapped items in a gravity displacement or prevacuum sterilizer with recommended minimum exposure times and temperatures. Steam sterilization by this unwrapped method is not recommended. It should be used only for emergency sterilization.

Types of Steam Sterilizers

A steam sterilizer, also know as an "autoclave," is a pressure-type vessel with a door or cover, valves to control the entry and exit of steam and air, and monitoring devices to allow the operator to observe conditions inside. It is designed to hold items and allow steam under pressure to penetrate these items. Steam sterilizers are available in many sizes, ranging from portable countertop to the fixed room-size sterilizer. Two of the most common types of steam sterilizers used in the Navy are the gravity displacement and prevacuum sterilizers.