Published on February 02-12-21



By Marie T. Fluent, DDS


The purpose of instrument processing is to provide sterile dental instruments for safe patient care. CDC Guidelines provide recommendations for instrument processing and monitoring the effectiveness of autoclaves using a combination of mechanical, chemical, and biological monitors (spore tests). Spore tests remain the gold standard for monitoring the sterilization process because they assess it directly by killing highly resistant bacterial spores rather than merely testing the physical and chemical conditions necessary for sterilization. Although mechanical and chemical indicators do not prove sterilization has been achieved, they allow detection of certain equipment malfunctions, and they certainly can help identify procedural errors. Thus, it is recommended that sterilizers are monitored with spore tests at least weekly, and any load with an implantable device. 

While the combination of monitoring methods is intended to provide safeguards and ultimately ensure sterility, gaps in quality assurance do exist. Consider the following case scenario:

Case scenario: 

Kim, an educated dental assistant was a relatively new employee at a dental facility. She performed a spore test early Monday morning on an autoclave – a different brand than which she was trained. Kim placed the spore test in the center of an empty chamber per manufacturer’s instructions and mailed it for processing. On Thursday, Kim received “immediate notification” from the sterilization monitoring service that her spore test failed! Recognizing the implications, a sense of slight panic and a series of questions raced through Kim’s mind: “Why did it fail? What happened to the instruments that have been processed since the test, and have they been used for patient care? Could I identify unused packages, retrieve and reprocess them? Should the patients who may be impacted be notified?  And, what should I do next?” Kim immediately reported this situation to her Infection Control Coordinator and owner/dentist. 

Unfortunately, incidents such as this still exist. Fortunately, there are measures that can be taken to prevent such situations. This article will address quality assurance measures to ensure instrument sterility and instill a sense of calm-confidence and a culture of safety to dental personnel who reprocess instruments.

“Immediate notification” may not be soon enough

In the scenario above, over three days of patient care had been performed utilizing numerous instrument packages. There is a possibility that the autoclave had been malfunctioning for the entire three days (or more), or that this was an isolated cycle-failure incident. Potentially, one or more patients treated during those three days was infected with a pre-existing bloodborne pathogen (Hepatitis B, Hepatitis C, or HIV). The answers to these possibilities are unknown, and it is evident that a three-day gap in the BI monitoring process represents a gap in quality assurance. Before continuing with this scenario, CDC recommendations for chemical indicator use will be briefly discussed. 

Chemical Indicators: 

CDC Guidelines recommend various types of chemical indicators (CI) including the use of “external” and “internal” chemical indicators stating that a ”type 1 CI be placed on the outside of each instrument package, unless the internal CI is visible from the outside.” CDC Guidelines also address “single-parameter” and “multi-parameter” chemical indicators as they provide a more reliable indication that sterilization conditions have been met. Yet, there are not specific recommendations for the use of these specialty indicators within the Guidelines. The manufacturer’s instructions for use of the chemical indicator will indicate the sterilizer type and cycle in which the CI should be used, placement within the package, storage, expiration date, and how to interpret the exposed CI. Table 1 provides a list of chemical indicator types and a brief description. 

Table 1: Chemical Indicator Types



Type 1

Process indicator (External)

Demonstrates that an item has been exposed to a sterilization process and distinguishes between processed and non-processed items.

Type 2

Indicators for use in specific tests

Used in specific test procedures in certain sterilizers (e.g. pre-vacuum sterilizers). The most common example is the Bowie-Dick test.

Type 3

Single critical process variable indicators (Internal)

Responds to only one critical parameter of the sterilization process (usually time or temperature). Note: The sterilization process has more than one critical parameter, and all must be reached for sterilization to occur.

Type 4

Multicritical process variable indicators (Internal)

Responds to two or more critical parameters of the sterilization process.

Type 5

Integrating indicator


Responds to all critical parameters of the sterilization process (time, temperature, and pressure.) The stated values are generated to be equivalent to, or exceed, the performance requirements for biological indicators.

Type 6

Emulating indicator (Internal)

Responds to all critical parameters of the sterilization process for a specified sterilization cycle.

Reference: ANSI/AAMI/ISO 11140-1:2014



Type 5 Integrating Indicators:



Type 5 integrating indicators mimic the response of a biological indicator. These specialty indicators contain a steam sensitive chemical that imparts a physical change, such as movement of the chemical along a strip or a change of ink from one color to another when all critical parameters of sterilization have been met. They do not guarantee that sterilization has occurred, nor do they replace the need for weekly (or more frequent) spore tests. Yet, as integrating indicators allow detection of certain equipment malfunctions, and can help identify procedural errors, they allow dental personnel to confidently release dental instruments BEFORE the spore tests are known. (Note that sterilization loads containing implantable devices must be quarantined until a passed spore test has been achieved.) 

Type 5 CIs are intended to be used at least once per day and in every load containing an implantable device – in every load or even every pack as the internal indicator. To use a Type 5 integrating indicator for each load, the strip should be placed in the middle of the chamber or within the densest instrument pack. The load should be processed according the sterilizer’s instructions for use. The results may be read immediately upon sterilization cycle completion. The results should be interpreted per the manufacturer’s instructions for use. If the interpretation does not indicate a safe or pass, the load may not be released as these instruments are not considered safe for patient care.

Discussion of the case scenario:

Kim may have averted much anxiety if she had processed a type 5 CI within the same cycle as her spore test. Upon completion, she would have immediately identified a cycle-failure. As the majority of failed spore tests are operator related, she would have followed CDC recommendations for BI failures, reviewed sterilization procedures, and retested the sterilizer using another type 5 integrating indicator and additional spore test. If the subsequent cycle passed the integrator test, Kim would have mailed in the spore test for processing. Most importantly, she would have had confidence that the processed instruments subsequently were safe for patient care.

Follow up:

This situation with the failed spore test is a true story. As events unfolded, the Infection Control Coordinator reviewed the autoclave instructions, and it was determined that the door of the sterilizer was unlocked during the failed cycle. Thus, there was not adequate steam and pressure for sterility to occur. A type 5 CI with an additional BI was then run through an additional sterilization cycle. The integrating indicator passed, the autoclave was placed back into service, and the owner/dentist deemed it was not necessary to notify patients. The repeat BI test was negative for growth of spores, as anticipated.

To prevent future operator error sterilization incidents, several education and training sessions were implemented. CDC recommendations for instrument processing were reviewed utilizing the checklists in the CDC Summary. Standard operating procedures were established regarding the use of Type 5 integrators and logs for each sterilizer and the protocol for instrument packaging and labeling were reviewed. Finally, a training session with a manufacturer’s representative was arranged to review operation of the sterilizer and routine maintenance and cleaning, and training sessions were documented.

Lessons learned and conclusions:

As the above case scenario is reviewed, there are numerous lessons to be learned:

  • Owner’s manuals of infection prevention equipment should be kept in a designated location where they may be easily retrieved, and responsibilities for reprocessing should be assigned to personnel with appropriate education and training.
  • Rely on the expertise of manufacturer representatives of dental equipment and supplies who may help troubleshoot potential errors when experiencing technical difficulties, facilitate loaned equipment, and facilitate training on proper use and maintenance of equipment.
  • CDC’s Summary of Infection Prevention Practices in Dental Settings and accompanying checklists may serve as review or evaluation of the infection control policies and protocols within a dental office, while the CDC Guidelines provide steps to take in case of a failed spore test.
  • Finally, there are many fail-safes within the reprocessing system, and the use of Type 5 integrating indicators adds an element of consistency, efficiency, and quality assurance to the sterilization monitoring process.  


About Marie T. Fluent, DDS


Dr. Fluent is a graduate of the University of Michigan School of Dentistry. Her dental career spans 35 years and includes roles as dentist, both as an associate and practice owner, infection control coordinator, office manager, and dental assistant. Additionally, she has extensive experience and expertise as a dental inflection control clinical instructor, educator, speaker, author, and consultant. Dr. Fluent is passionate and deeply committed to improving dental infection control and patient safety. Through her writing, webinars, and invited lectures, she has educated thousands of dental professionals and students nationally and internationally. Dr. Fluent has written numerous peer reviewed articles on infection control in the dental setting, OSHA compliance, and responsible antibiotic prescribing. For more information, see 


Note: The article is based on CDC recommendations. In some European countries they may be different. We recommend to refer to specific National Guidelines (