| FAQ - Instrument Processing - 2014
We have a long-standing persistent rust issue in our clinic. Even new instruments that are run through the processing eventually come out stained and rusted. Now a package is being put together to replace all of our instruments. Do you know of any document supporting the fact that instruments that have rust cannot be adequately sterilized and need to be replaced. Also, some time ago the clinic was in a different building where water softener was used for our Brand A washer and the instruments did not rust. Do you have any information supporting use of water softener to combat rust in such situations?
The following information may help you to better understand the issue of rust and corrosion as it pertains to dental instruments.
Infection Control and Management of Hazardous Materials for the Dental Team states as follows:
Corrosion Control, Drying, and Lubrication
Instruments or portions of instruments and burs made of carbon steel will rust during steam sterilization. Examples include non-stainless steel cutting or scraping instruments such as burs, scalers, hoes, hatchets, the cutting surfaces of orthodontic pliers, and the grasping surfaces of forceps. Although one can spray rust inhibitors (e.g., sodium nitrite) on the instruments or use a dip to reduce rusting of some of these items, the best approach is not to process such items through steam. Instead one should dry the instruments thoroughly and use dry heat or unsaturated chemical vapor sterilization on the items most susceptible to rusting in steam. Another alternative is to switch to stainless steel-type instruments, if available.
Instruments to be processed through a steam sterilizer should at least be shaken to remove excess water or dried more thoroughly if they will be packaged in paper or paper-plastic sterilization wrap. This avoids accidental tearing of wet paper during packaging. Some hinged instruments may need to be lubricated to maintain proper functioning, but one should remove as much excess lubricant as possible before heat processing. Hinged instruments should be opened before packaging to facilitate access of the sterilizing agents to all parts of instruments. Drying equipment for cleaned unwrapped instruments is available. 1
Instrument processing can cause damage to instruments, but one can take several steps to keep damage at a minimum (Box 12-2).
Stainless steel instruments are least affected by corrosion from moisture and heat, but some dentists prefer instruments with carbon steel rather than stainless steel because carbon steel cutting surfaces may retain a sharp edge longer. Unfortunately, carbon steel items corrode and lose sharpness during steam sterilization. For example, tungsten carbide burs lose approximately 64% of their cutting efficiency after steam sterilization. Use of dip or spray inhibitors usually reduces corrosion, but with repeated steam sterilization cycles, the items will be damaged. Carbon steel items are sterilized best in a non-corrosion-producing environment such as dry heat or unsaturated chemical vapor sterilizer. One should make every effort to rinse away or remove biological debris, disinfecting or sterilizing solutions, chloride salts, and highly alkaline detergents before heat-processing instruments. These substances may cause pitting or staining of metal surfaces, which can be aggravated with heat. Packaging together of items of widely dissimilar metals during heat processing is not prudent because of a potential for electrolytic damage to instrument surfaces. However, this procedure is difficult to accomplish practically because of the wide variety of instruments needed for single procedures. 1
In Sterilization and Disinfection of Dental Instruments, the American Dental Association states:
All critical and semicritical dental instruments that are heat stable should be sterilized after each use by steam under pressure (autoclaving), dry heat, or chemical vapor. Before sterilization or high-level disinfection, instruments should be cleaned so that any debris is removed. Enzymatic and non-enzymatic solutions facilitate instrument cleaning. Heavy-duty gloves should be worn when handling contaminated instruments. Instruments should soak in water or disinfectant/detergent as soon as possible after use to prevent drying of debris. Instrument cassettes and mechanical cleaning (e.g., ultrasonic cleaners) may be used to reduce direct handling of contaminated instruments. Applying rust inhibitors will protect instruments from corrosion that may result from autoclaving. Packaging rinsed and dried instruments before sterilization protects them from contamination after they are removed from the sterilizer and during transport chairside or to storage. 2
Rust Inhibitors are used to retard corrosion of carbon steel. 2
The US Air Force Dental Evaluation and Consultation Service also provides relevant information in fact sheet format:
Instrument Processing – Cleaning
Instrument Processing – Sterilization and Storage
OSAP does not review, evaluate, certify, recommend or endorse products. OSAP also does not provide technical support for specific products. If you have further questions about procedures and specific products it is recommended that you consult with the manufacturer’s written instruction manual and/or contact the manufacturer of your product. For example, further information about contacting Miele can be accessed on this webpage:
1) Miller CH. Infection Control and Management of Hazardous Materials for the Dental Team, 5th edition. Elsevier/Mosby Publishers. Pages 126 & 145.
2) American Dental Association. Sterilization and Disinfection of Dental Instruments. https://www.ada.org/members/pdfs/instrument_sterilization.pdf Accessed On March 18, 2014.
3) US Air Force Dental Evaluation and Consultation Service. Instrument Processing – Cleaning http://www.afms.af.mil/shared/media/document/AFD-130404-125.pdf Accessed on March 18, 2014.
4) US Air Force Dental Evaluation and Consultation Service. Instrument Processing – Sterilization and Storage http://www.afms.af.mil/shared/media/document/AFD-130404-122.pdf Accessed on March 18, 2014.