Dental Instrument Cleaning and Sterilization

Dental Instrument Cleaning and Sterilization

Unfortunately, dental practices and colleges of Dental Medicine are not immune to lapses in dental instrument processing. One of the most recent incidents occurred at a Florida College of Dental Medicine. More than 1,100 patients were notified of the potential for acquiring a bloodborne pathogen as a result of this breach. A surface disinfectant wipe was used on instruments that should have been sterilized. Cleaning patient care equipment requires proper processes and diligence.

General Sterilization Principles for Dental Instruments

Before going into detail about sterilization, let’s go over some general principles. An instrument or device can’t be sterilized if it isn’t clean. Therefore, the first step in instrument processing is cleaning. Check the instrument manufacturer’s directions for cleaning instructions. For example, some manufacturer’s instructions for torque wrenches instruct the user to disassemble the instrument for cleaning and then reassemble prior to sterilization.

Another great example is a well-known manufacturer’s dental cassette instructions indicate the cassette must be placed in an ultrasonic for 16 minutes every time it is used.  The manufacturer’s instructions should be followed precisely to ensure the bioburden is decreased as much as possible on the instruments, devices, and instrument containers prior to sterilization. Items must be rinsed if placed in an ultrasonic for cleaning to ensure all detergent residue is removed. Lastly, when packaging instruments, an indicator tape should be used on the outside of wrapped packages, and an internal chemical indicator strip should be placed inside every pouch and cassette.

One important principle of sterilization is that the sterilant such as steam must be able to contact all surfaces of the items to be sterilized. If composite material or other soil remains on the instrument, sterilization will not be adequate since the sterilant can’t penetrate such obstacles.

A Deep Dive Into Dental Instrument Cleaning

The Spaulding Classification system is generally used to gain a better understanding of what process should be followed to ensure instruments and devices are safe for patient use. This system contains three classifications: critical, semi-critical, and non-critical.

Critical instruments or devices “penetrate soft tissue or bone or enter into or contact the bloodstream or other normally sterile tissue” (American Dental Association, Sterilization Statement). Examples include biopsy, periodontal surgery, apical surgery, and implant surgery. Any instrument that fits in this category should be sterilized. Steam sterilization is the most frequently used type of heat sterilization in dentistry. However, check the manufacturer’s directions to ensure the correct type of sterilization is used, and the correct sterilization parameters are followed.

Semi-critical instruments or devices contact non-intact skin or mucous membranes. This classification pretty much covers most of the instruments and devices that enter the mouth but don’t contact sterile tissue or the vascular system. Ideally, semi-critical items should be sterilized or, at a minimum, high-level disinfected or cold chemical sterilized. The last statement requires some explanation. Sterilization means all organisms are inactivated, while high-level disinfection is defined as destroying all organisms except bacterial spores.

The only difference between high-level disinfection and cold chemical sterilization is the amount of time that items must remain immersed. Only those chemicals cleared by the FDA as a sterilant should be used for cold chemical sterilization. If not cleared as a sterilant, the chemical may only be used as a high-level disinfectant.

Non-Critical Items

Non-critical items only contact intact skin but not mucous membranes such as blood pressure cuffs. These items require low-level or intermediate-level disinfection. A disinfectant spray or wipe is appropriate for these items. Low-level disinfectants will have a hepatitis B (HBV), and human immunodeficiency virus (HIV) claim, while intermediate-level disinfectants will contain a tuberculocidal claim. Most importantly, ensure the disinfectant is an EPA registered hospital disinfectant.

Critical Items

Critical instruments and devices require sterilization. If an item classified as ‘critical’ can’t be heat sterilized, the Centers for Disease Control and Prevention (CDC) recommends replacing the item with something that can be heat sterilized.

Cold Chemical Sterilization

The American Dental Association (ADA) acknowledges that there is a limited need for cold chemical sterilization. However, the CDC recommends replacing semi-critical heat-sensitive items with either item that are heat-tolerant that can withstand heat sterilization or purchasing disposable alternatives. In my experience visiting dental practices and Colleges of Dental Medicine, I have never seen cold chemical sterilization performed properly. This places patients at risk for acquiring bloodborne pathogens and isn’t a reliable standard precaution for preventing infections caused by a myriad of organisms.

Prior to sterilizing any instrument or device, consult the manufacturer’s instructions. The instructions will detail the type of sterilization that is acceptable for that item as well as provide cycle parameters of time, temperature, and pressure to achieve sterilization. Since the manufacturer has conducted extensive testing to ensure the item is sterile, it is important to follow those directions.

Steam Sterilizer Technology

Since most dental practices use tabletop sterilizers, the remainder of this discussion will focus on that type of steam sterilizer. Some key points related to tabletop sterilizers are:

  • Tabletop sterilizers require a fair amount of maintenance or cleaning. Follow the manufacturer’s directions for daily, weekly, and monthly cleaning.
  • Only use the product(s) recommended in the Owner’s manual for cleaning the sterilizer since other products may not perform as desired or may have deleterious effects on the sterilizer.
  • Generally, tabletop sterilizers require distilled water to operate properly. Some manufacturers, like Tuttnauer, ONLY recommend distilled water. This is key to the proper operation of the sterilizer. If your practice has a ‘filtered’ water system, be sure you know what type of water (distilled, reverse osmosis, deionized) is produced before putting it into your sterilizer. I have seen some sterilizer disasters related to using the wrong type of water.
  • Load the sterilizer according to the manufacturer’s directions. There are pouch racks and cassette racks available for most sterilizers. However, to ensure the items are sterilized, be sure to follow the rack directions for loading. If not using a rack, the orientation of the pouches on the sterilizer tray is critical. Be sure to place the pouches on the tray plastic up or down, based on the sterilizer manufacturer’s recommendations.
  • Wet loads or wet instruments in a load are not acceptable since they signify a sterilization problem. Common reasons for wet loads include:
    • Too many instruments in a paper-plastic pouch. Pouches should contain only one or two lightweight instruments, not an entire set.
    • Pouches touching, overlapping, or not in a single layer on the tray
    • Cassettes touching or overlapping or not wrapped properly
    • Improper sterilizer maintenance
    • Interruption of the drying cycle or not following instrument manufacturer’s directions for drying time (i.e., handpieces will most likely require a longer drying time than probes)


Wet or hot instruments shouldn’t be handled since the pores of the wrapping material are open, which allows organisms to migrate into the package and contaminate the instruments. Most sterilizer owner’s manuals contain a very nice troubleshooting section, which assists with problem-solving. Replace consumable parts of the sterilizer as frequently as recommended for optimal functioning. For example, if gaskets aren’t checked and replaced when worn, the sterilizer may not seal properly, which compromises the sterility of the load.

Although this is not an exhaustive list of problematic areas in dental instrument reprocessing, this information covers many of the significant issues related to a very time-consuming but extremely important task that is essential to keeping patients safe from harm.