Infection Control for Dental Assisting Exam Study Guide (page 3)

Updated on Jun 23, 2011


Sterilization is the process that completely destroys microorganisms (including bacteria and spores) on instruments, equipment, and surfaces.

Instrument Classification

Dental instruments are grouped into three categories, according to their function: critical, semi-critical, and non-critical.

Critical Instruments

Critical instruments are those that contact or penetrate soft tissue or bone. These include scalpels, burs, scalers, and other dental tools that penetrate bone and tissue.

Semi-critical Instruments

Semi-critical instruments are instruments that come in contact with the oral cavity but do not penetrate soft tissue or bone. These include amalgam carriers, condensers, and other items that touch tissue and are contaminated by blood and saliva.

Non-critical Instruments

Non-critical instruments are those that pose the least risk of spreading infection because they do not come in contact with soft tissue, membranes, or broken skin. These include items such as the X-ray unit position indicator device or X-ray film holder (Snap-A-Ray).

Instrument Processing

Instrument processing involves seven steps: transport, cleaning, packaging, sterilization, storage, delivery, and quality assurance of all dental instruments. Personal protective equipment must be worn at all times during the sterilization process. All instruments are packaged after cleaning and before sterilization to group them in sets and to protect them from contamination after sterilization.

Methods of Sterilization

Four of the leading methods of sterilization are autoclave, chemiclave, flash sterilization, and cold sterilization.


An autoclave sterilizes instruments by converting water to steam and pressurizing it. This is known as steam under pressure. High heat and pressure kills any remaining microorganisms or spores. The average cycle of an autoclave is 30 minutes: 20 minutes at 250° F (121° C) at 15–20 pounds per square inch (psi) for sterilizing, and ten minutes venting time for drying.


The chemiclave converts chemical vapor into steam and pressurizes it. The odor emitted is unpleasant, and the office should be equipped with a special vent for use with this type of sterilizer. The average cycle of a chemiclave is 30 minutes: 20 minutes at 270° F (132° C) at 20 psi for sterilizing, and ten minutes for drying.

Flash Sterilization

Flash sterilization is utilized in an office when a particular instrument is needed right away. The average cycle of a flash sterilizer is three minutes at 270° F (132° C) at 15 psi for unwrapped instruments. The instrument needs to be used right away since it is unwrapped.

Forms of Sterilization Monitoring

Whatever type of sterilizing is used, it must be monitored to ensure that the dental instruments are properly sterilized. There are three forms of monitoring: physical, chemical, and biological.

Physical Monitoring

Physical monitoring of the sterilization process involves checking the readings on the indicators on the sterilizer, along with checking if the color-changing pouch or tape has in fact changed color to denote that a certain temperature level was reached.

Chemical Monitoring

Chemical monitoring of sterilization uses heat-sensitive chemicals that change color under certain conditions. Process indicators are placed outside the instrument packs, while process integrators are placed inside.

Biological Monitoring

Biological monitoring involves spore testing to establish whether the sterilization process was successful. Weekly testing is mandated by OSHA for every sterilization device utilized in the office. The spores utilized are bacillus stearothermophilus for steam and chemical vapor sterilizers, and bacillus subtilis for dry heat and ethylene oxide sterilizers.

Hand-Piece Sterilization

Dental hand pieces must be carefully sterilized to avoid cross-contamination.

Pre-cleaning Techniques

Before the actual sterilization begins, wipe down the hand piece with disinfectant wipes or alcohol-soaked gauze 2 x 2s to remove any bioburden. It is recommended that the hand piece be flushed for 20–30 seconds prior to disconnecting to remove any contaminated water. Hand pieces should never be immersed in any type of liquid. Follow the manufacturer’s directions regarding lubrication of the dental hand piece.

Sterilization Techniques

There are only two ways to properly sterilize hand pieces: steam or chemical vapor sterilizers. As with other dental instruments, hand pieces should be packaged before being sterilized.

Practice problems for this study guide can be found at:

Infection Control for Dental Assisting Exam Practice Problems

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