Why monitor your sterilizer? To verify infection control, of course. Regular sterilizer monitoring—when properly implemented—is an important part of an effective infection control program in a dental office.

But proper monitoring requires you and your team to understand and correctly implement the factors (a combination of process parameters) leading to successful sterilization. These components need to be in place to evaluate the conditions of the sterilizing process in your office, and your sterilizer’s effectiveness.

We’ll cover two tools you should be using in your office to monitor your sterilizer, and give you a few related and important tips.

Biological Monitoring (Spore Testing): Tests for Sterilization

Biological monitoring—or spore testing—is the standard for assuring proper sterilization of dental instruments.

Texas Administrative Code states that “sterilization equipment and its adequacy shall be tested and verified in accord with American Dental Association (ADA) recommendations.”

ADA recommends that dental offices monitor sterilizers at least weekly with biological indicators.

How does spore testing work?

Biological indicators impregnated with highly-resistant, nonpathogenic bacterial spores test a sterilizer’s function.

Specific spores (Geobacillus stearothermophilus for steam/chemical sterilizers, and Bacillus atrophaeus for dry heat sterilizers) are inoculated onto strips of specialized filter paper.

This paper is packaged in a peel-open, glassine-paper pouch. (Glassine paper is permeable to sterilant, but resistant to moisture and air at ambient temperature and pressure.)

How should spore testing be conducted?

The glassine-bound spore strips should be placed according to the sterilizer manufacturer’s instructions. (Note that lot number and expiration date are printed on each glassine.)

If there are no instructions, place the spore test strip within a wrapped set of instruments in the most difficult area to be sterilized—normally the lower front area of the sterilizer.

It’s a good practice to place the strips in a different location of the sterilizer each week to help identify any “cold spots.”

Chemical Indicators: Tests for procedural errors or inadequate physical conditions (for sterilization)

Chemical indicators help assess physical conditions, and identify procedural errors. They let you know a package has been placed through a sterilization cycle.

Correct readings don’t prove that sterilization occurred. However, incorrect readings can help identify a problem with the sterilization cycle.

It’s recommended that your office includes chemical indicators in each load.

There are two types of chemical indicators:

External chemical indicators: These change color when a specific parameter is reached, and should be applied to the outside of sterilization packages.

Internal chemical indicators: These should be placed inside each package (next to the instruments) to ensure the sterilizing agent reached inside it.

NOTEAside from chemical indicators, physical parameters should also be checked by you and your staff. Gauges and displays on the sterilizer should be monitored for cycle time, temperature, and pressure. As with chemical indicators, though correct readings don’t verify sterilization, incorrect readings can help identify a problem with the sterilization cycle.

What if a Spore Test Result is Positive?

A single positive spore test probably does not indicate sterilizer malfunction—especially if the process indicators demonstrate sterilizer effectiveness.

But when improper sterilization does occur, common factors are:

  • Chamber overload
  • Excessive packaging material
  • Inadequate exposure time
  • Incorrect temperature/pressure settings
  • Failure to preheat the sterilizer (if indicated)
  • Interruption of the cycle
  • Expired chemical solution (chemiclaves only)

So what should you do if a process indicator turns positive (you receive a positive spore test result)? Follow these steps:

  • Ensure the process indicator hasn’t expired.
  • Ensure testing protocol was met.
  • Check the sterilizer for obvious inconsistencies.
  • Retest with the process indicator immediately.
  • Contact your biological monitoring service immediately for assistance.

General tips

  • All staff members who operate the sterilizer should receive training on proper sterilizer operation procedures and instrument processing techniques.
  • Your office should perform general sterilizer maintenance: regular cleaning and checking of door gaskets, vents, and internal and external surfaces of the sterilizer. Follow the sterilizer manufacturer’s instructions.


TDA Perks Program partner OSHA Review Inc.’s Spore Check System lets you know whether or not your sterilizer is working properly, week by week. The system costs $159 per sterilizer/year ($3.05 per test).

OSHA Review’s in-house lab, full-time microbiologist and years of experience deliver accurate results quickly, and can help you track down any problems. For more information regarding OSHA Review, call 800-555-6248 and mention TDA Perks Program.