Written by Duane Tinker


Spoiler Alert: Gruesome Pictures Ahead!


We need to have serious talk about instrument reprocessing.

Recently, I was in a dental office doing my thing with an awesome dentist and a great dental team when I stumbled onto something SHOCKING lurking in the sterilization and instrument reprocessing area.

During my office walk throughs, I love to break open “sterile” instruments to check them for rust, damage and “other” stuff. 

This is what I found: In this first picture (‘sterile’ instrument) we see what we may all assume is rust on the hinge. (It would require testing to verify this is actually rust.) I have tested similar-looking instruments which tested positive for protein and ATP (meaning “not clean” and “not sterile”).

This situation, though shocking, is something I encounter fairly often. It dawned on me that I should blog about it, so here I am.


The following is another view of the same instrument.


Does this concern you?

I did not test these discolorations, however every person I have shown this to thinks that it looks like blood. Whether it is blood or not, it definitely does not belong on a clean instrument.

Believe it or not, I find things like this more frequently than I should. So how does this happen? It happens because many dental office staff don’t understand or deviate from (albeit unintentionally) the proper methods of cleaning and inspecting dental equipment. 

We assume clinical team members know what they are doing. We assume they use products and equipment correctly. They certainly should, but do they actually? I find a LOT of errors in knowledge and proper use by clinical staff. I find these errors are not intentional and that people generally do the best they can with the knowledge they have.

We are all familiar with spore testing to monitor the sterilizer, but did you know you are also supposed to monitor your ultrasonic cleaner? This is true!

The CDC Guidelines for Disinfection in Healthcare Facilities (yes, this applies to dentistry) specify to meticulously clean patient-care items with water and detergent, or with water and enzymatic cleaners before high-level disinfection or sterilization procedures. Also, clean medical devices as soon as practical after use (e.g., at the point of use) because soiled materials become dried onto the instruments.

Cleaning is the removal of foreign material (e.g., soil, and organic material) from objects and is normally accomplished using water with detergents or enzymatic products.

Thorough cleaning is required before high-level disinfection and sterilization because inorganic and organic materials that remain on the surfaces of instruments interfere with the effectiveness of these processes.

Also, if soiled materials dry or bake onto the instruments, the removal process becomes more difficult and the disinfection or sterilization process less effective or ineffective. (We see this on the above pics.)

Instruments should be presoaked or rinsed to prevent drying of blood and to soften or remove blood from the instruments. (Good point!) 

Cleaning is done manually or by use of mechanical units (e.g., ultrasonic cleaners or washer- disinfectors). 

Ultrasonic cleaning removes soil by cavitation and implosion in which waves of acoustic energy are propagated in aqueous solutions to disrupt the bonds that hold particulate matter to surfaces.

(Biology and physics play major roles in instrument reprocessing. Pretty cool, huh?)

Users of ultrasonic cleaners should be aware that the cleaning fluid could result in endotoxin contamination of surgical instruments, which could cause severe inflammatory reactions.

(In other words, you could get “the funk” if you come into contact with contaminated solutions from ultrasonic cleaners, so wear proper PPE.)

For instrument cleaning, a neutral or near-neutral pH detergent solution commonly is used because such solutions generally provide the best material compatibility profile and good soil removal.

Enzymes, usually proteases (protein-based), sometimes are added to neutral pH solutions to assist in removing organic material. Enzymes in these formulations attack proteins that make up a large portion of common soil (e.g., blood, pus). Cleaning solutions also can contain lipases (enzymes active on fats) and amylases (enzymes active on starches).

Protease enzymes are the most commonly cleaning chemicals used in dentistry. Though triple enzyme products are widely available, my experience is that they do not seem to outperform protease enzymes.

Enzymatic cleaners are not disinfectants, and proteinaceous enzymes can be inactivated by germicides, so don’t mix products.

Enzyme solutions should be used in accordance with manufacturer’s instructions, which include proper dilution of the enzymatic detergent and contact with equipment for the amount of time specified on the label. Different instruments require different contact times in the ultrasonic. Loads of instruments often contain a mix of instruments with different contact time requirements. From the manufacturer’s instructions for you for each instrument you should be able to determine the minimum contact time for your instruments. For most instruments, the minimum contact time is up to 16 minutes. Keep this mind when setting the timer on your ultrasonic cleaner.

As with all chemicals, enzymes must be rinsed from the equipment or adverse reactions (e.g., fever, residual amounts of high-level disinfectants, proteinaceous residue) could result. Exposure to enzymes can result in asthma or other allergic effects in users.

Neutral pH detergent solutions that contain enzymes are compatible with metals and other materials used in medical instruments and are the best choice for cleaning delicate dental instruments.

The only way to ensure adequate cleaning is to conduct a reprocessing verification test (e.g., microbiologic sampling), but this is not routinely recommended. Validation of the cleaning processes in a laboratory-testing program is possible by microorganism detection, chemical detection for organic contaminants, radionuclide tagging, and chemical detection for specific ions. 

During the past few years, data have been published describing use of an artificial soil, protein, endotoxin, X-ray contrast medium, or blood to verify the manual or automated cleaning process and adenosine triphosphate bioluminescence and microbiologic sampling to evaluate the effectiveness of environmental surface cleaning. At a minimum, all instruments should be individually inspected and be visibly clean.


My friend Steven Kovach, “The CPD Guy” says, “It Can't Be Sterile If It's Not Clean." He also says, “Sterile is not sterile if clean is not clean.”


Enzymes and detergents are used to speed the breakdown of bioburden found on instruments. In the enzyme soak, each enzyme cleaner has an optimal temperature range for best performance. Outside of this range, enzymes become less effective and ultimately inactive. 

In addition to water quality, it is important that the right cleaners are used for the targeted soil to be removed. Using the right amount of cleaner is instrumental to the process as well. Insufficient amounts will not clean effectively -- and excessive amounts may shorten the life of instruments and leave harmful residue.

Note: read the instructions on your enzyme tablet or solution to identify the optimal temperature range to use when soaking/cleaning your instruments. Be sure to pay close attention to the specified concentration, as this makes a significant difference in your instrument cleaning process.


“The failure to adequately reprocess contaminated instruments—that is, not cleaning and disinfecting or sterilizing them—before using them on subsequent patients can lead to the spread of deadly pathogens.” – ECRI


In other words, if your instruments are not clean, they are not sterile either, and using them on patients can harm your patients. Let that sink in for a moment.


The Joint Commission says, “If tissue, bone, or other soil is left behind on a surgical instrument, this unsterile condition obviously could carry risk of infection to the next patient, and it should not be reused.”


Granted, few dental offices are accredited by The Joint Commission, but the fact does not make this statement any less relevant.


Okay, now it’s Tinker-time!

I’ll make this as simple as I can.

There are fundamentally two things happening in sterilization:
  1. Instrument cleaning
  2. Instrument sterilization
If we don’t get the first part right, the second doesn’t matter;
 the end result is still “dirty” instruments.


We monitor sterilizers weekly, pursuant to CDC guidelines, to make sure the sterilizer does its job properly (second part), yet this is only part of the whole equation. The guidelines do specify that instruments should be visually inspected, but there is nothing about testing instruments for cleanliness or testing ultrasonic cleaners or instrument washers for proper performance. That said, we make a lot of assumptions about instrument reprocessing.

We assume clinical team members know what they are doing. We assume they use products and equipment correctly. They certainly should, but do they actually? I find a LOT of errors in knowledge and proper use by clinical staff. I find these errors are not intentional and that people generally do the best they can with the knowledge they have.

I am shocked that many/most states do not require infection control training for dentists, dental hygienists, or dental assistants. Few, if any, states limit instrument reprocessing duties to certified/licensed clinical staff. Sterile technicians in hospitals have to maintain certification, but the same cannot be said for the people who sterilize instruments in dental offices. While hygienists and assistants in most dental offices handle instrument reprocessing this is not always the case.

Another assumption is we make is that clinical staff inspect the instruments while reprocessing, but do they and are they thorough? We really have no idea. I know I find a lot of ‘rusty’ and ‘bloody’ instruments.

We assume if instruments go through the cleaner and sterilizer, they are clean and sterile. We must ask, “What if our assumptions are wrong?”

Proper instrument cleaning and proper sterilization procedures are vitally important to ensure patient safety, control dentist liability, and for moral, legal, even ethical reasons. In my mind, monitoring these processes, cleaning and sterilizing, is mission critical.

Ensuring proper mechanical operation requires periodic and ongoing preventive maintenance and accurate monitoring. Many are familiar with the foil test for ultrasonic machine testing. The problem is this is a subjective test that is open to interpretation.

What if the reader’s interpretation is incorrect? Since few people retain photos of complete foil tests, there is no way to determine changes (degradation) that (likely) occurs over time. Ultrasonic cleaners and instrument washers fail.

When they fail, you need to know, so you can do something to resolve the problem. In my experience, when these machines fail, they don’t sound any different. Often, there are no obvious signs of failure.


Ultrasonic Monitors are available from: 

  • Hu-Friedy – Cleaning Monitors -



How to avoid the situation we see in these pictures:

  1. Hinged instruments should be opened fully to allow adequate contact with the enzymes or detergent solution; and instruments should be disassembled as much as possible before they are placed in the ultrasonic bath or instrument washer.
  2. Avoid overfilling (with instruments) the ultrasonic bath or instrument washer.
  3. Fill your water level up to the fill line every time you use the ultrasonic cleaner. (Failure to do so can damage the unit and burn out the transducers that make it work properly.)
  4. Ensure the concentration of detergent or enzymes is correct.
  5. Change the detergent or enzymes according to the manufacturer’s instructions.
  6. Different instruments require different amounts of time to properly clean them. Figure out what the longest time is for the instruments you have and use that as the minimum cycle time for your ultrasonic. (Hint: 16 minutes is a good rule of thumb.)
  7. If it will be a significant amount of time until the instruments will be cleaned, pre-soak them in enzymes or detergent.
  8. Inspect instruments while repackaging them for sterilization. If instruments are still dirty, rerun them, don’t manually scrub them; your equipment if designed to do one thing well and it will do a better job cleaning instruments than you can do by scrubbing them manually if your equipment works properly and you set the machine up for success (all the steps outlined in this section).
  9. Inspect your instruments before placing them in a patient’s mouth.
  10. Periodically test your ultrasonic cleaner and/or instrument washer to make sure it works properly. Some testing devices recommend daily testing. Your best defense is to always follow the instructions of your device’s manufacturer. (NOTE: when the transducers on ultrasonic machines go bad, the machine does not necessarily sound any different; so noise level and sound have little to no bearing on the actual functioning of your equipment)
  11. Establish and maintain testing records according to your state’s requirements. (I recommend you keep them at least three years in the absence of any regulatory requirement.)