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Oral Health Topics

Monitoring Sterilizers


Along with the proper sterilization of instruments and materials, sterilizer monitoring is an essential part of any in-office infection control program (for information on instrument and equipment sterilization, consult "Sterilization and Disinfection of Dental Instruments" in the ADA Roadmap to CDC Guidelines for Infection Control in Dental Health-Care Settings ).

Many factors can cause sterilization to fail-from procedural errors that are easily remedied, like overloading, to mechanical problems that can take your sterilizer out of service until repairs can be made. Since this variety of factors can influence successful sterilization, the ADA and CDC encourage dentists to regularly assess the efficiency of their in-office sterilizers.1 In addition, state or local regulations may exist regarding frequency and record-keeping issues related to sterilizer monitoring. Check with your state dental board for regulatory information.

How to monitor

Sterilization is best monitored using a combination of mechanical, chemical, and biological indicators.

Mechanical Monitoring

  • Record cycle time, temperature, and pressure as displayed on the sterilizer gauges for each instrument load.

Chemical Indicators

  • Use chemical indicators, such as indicator tapes, with each instrument load. These indicators change color after exposure to the proper sterilization environment.
  • Failure of the indicator to change color indicates that it was not exposed to the proper sterilization environment (e.g., proper pressure or temperature). In such cases, the instrument load should be re-sterilized.
  • Indicator tapes are sterilizer-specific (i.e., tapes for steam sterilizers cannot be used to test chemical vapor sterilizers).
  • Chemical indicators should not replace biological indicators, as only a biological indicator consisting of bacterial endospores can measure the microbial killing power of the sterilization process.

Biological Indicators:

  • The CDC recommends that you monitor sterilizers at least weekly with biological indicators.1 Check to see whether your state dental board has different requirements.
  • Biological monitoring can be done in two ways:
    1. In-office incubator and spore monitoring strips (contact your dental supplier for a list of products). This method usually gives results in 24-48 hours.
    2. Mail-in spore monitoring programs (PDF). This process usually takes a week. Although it takes longer to get results using a service, third-party monitoring programs may offer more credibility than in-house monitoring.
  • A positive spore test result indicates that sterilization failed.
  • Maintain a log of spore test results. Check with your state dental board to determine how long you need to keep spore testing records.

What to do when results indicate sterilization failure

If the chemical indicator does not change color or the spore test result is positive, the following steps are recommended:

  • Take the sterilizer out of service.
  • Review the sterilization process being followed in the office to rule out operator error as the cause of failure.
  • Correct any identified procedural problems, and retest the sterilizer using biological, mechanical, and chemical indicators.

If the repeat biological indicator test is negative and the other test results fall within normal limits, the sterilizer can be returned to service.

If the biological indicator test is positive, or the mechanical or chemical test results indicate failure, the sterilizer should not be used until the reason for failure has been identified and corrected.

  • If no procedural errors are identified or failures persist after procedural errors are corrected, the sterilizer should not be used until the reason for failure has been identified and corrected.

Before the sterilizer can be returned to service, negative results should be returned for biological indicator tests conducted during three consecutive empty-chamber sterilization cycles to ensure that the problem has been corrected.

  • To the extent possible, reprocess all instruments that were sterilized since the last negative spore test.
  • Record the positive test results and all actions taken to ensure proper functioning of the sterilizer in the monitoring log.


1. Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings-2003. MMWR 2003;52(No. RR-17): 43. http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5217a1.htm

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