The Reprocessing of Instruments:
Err on the Side of Caution

“All will come out in the scouring,” wrote Miguel Cervantes in his epic Don Quixote. At the time, Cervantes did not realize how intensely some things must be cleaned in order for the adage to be true. When it comes to instruments, cleaning alone would be wholly inappropriate and poses a serious health hazard.

In many countries, recommendations and guidelines for the proper processing of medical devices such as instruments have been published with slight variations depending on the norms and standards that have been adopted by each respective country. The purpose, however, remains the same: to validate and specify disinfecting and cleaning cycles, to maintain reliable functionality, to accomplish hygienic safety, and where necessary, declaration of sterilisation.

To safeguard the health of patients, dentists, doctors, and their staff, seven easy-to-follow steps have been designed. These steps describe the appropriate and safe processing of medical devices that need to be implemented in every dental/medical clinic. These basic steps are explained in the following list:

1. If necessary, precleaning and disassembly of instruments and unfolding of all hinges and jaw parts. Use of disinfectant wipes to clean the exterior of hand-pieces or to remove organic material/cements.
2. Selection of manual or automated disinfection and cleaning of instruments, and if required, rinsing and drying. For manual processing, choose high-level products suitable for immersion disinfection and cleaning. For automated processing, use a class b autoclave or something similar.
3. Disinfection of hands followed by visual inspection of cleanliness of instruments. Check for optical cleanliness; no organic residues or films must be evident.
4. In the event of persistent residue, repetition of step 2 followed by step 3.
5. Reassembly of instruments, functionality check, and maintenance if required. Control for visible damages, abrasion, and sharpness. Blunt or damaged medical devices are not recommended for patient use. If necessary, oil the joints carefully with a small amount of suitable lubricant.
6. Packing, labelling, and storage of noncritical medical devices. Store labelled and packed medical devices in a dry, dust-free, and contamination-free environment.
7. For critical medical devices, packing, labelling, sterilisation, storage, and monitoring of sterilised items. Pack instruments and leave all joints open; ensure that sharp edges do not tear the sterilisation pouch. Select appropriate sterilisation cycle (b and s is recommended for dentistry). After the sterilization process, check for pouch integrity, moisture, or contamination. If found, repack and resterilise, followed by second check. Store sterilized medical devices in a safe manner that eliminates the possibility of contamination, periodically check expiration dates, and resterilise after the safe storage period has expired.

The disinfecting and cleaning of instruments is not quite as straightforward as these steps may suggest. Prior to the disinfection and cleaning of any medical device, every dental practitioner and his staff are required to carry out a risk assessments and classify each instrument accordingly. Guidelines such as the hygiene requirements for the processing of medical devices printed by the Robert Koch Institute (Berlin, 2001) contain lists that subdivides medical devices into the risk categories “non-critical,” “semi-critical,” and “critical” depending on the risks to patients and staff, the type of treatment, as well as the design and material of the medical device. Semicritical and critical medical devices are further subdivided into groups a, b for semicritical, and a, b, and c for critical medical devices.

The following table lists the classification of medical devices as suggested by the Robert Koch Institute: Risk Assessment & Evaluation of Medical Devices

Note: Critical Medical Devices, Group C, has no relevance for dental practitioners

 While a risk assessment table is undoubtedly valuable, the different categories and their subgroups can produce confusion as to how various instruments such as hand-pieces and contra-angles, burs and elevators need to be disinfected and cleaned. Which group does each of these instruments belong to? Numerous risk assessment tables add to the confusion surrounding this important subject. Resulting confusion increases the risk of misplaced disinfection and cleaning practices.

The Processing of Medical Devices Made Simple

For the purpose of simplification, we have grouped the processing of medical devices under two general headings defined as “noncritical” and “critical” modelled after the RKI guidelines. The following format is believed to be easier to understand and more importantly reduces significantly the risk of accidental misclassification of any medical device used during daily routines. We recommend that dental practitioners, doctors, and their staff adopt the following two categories:

 Recommended Processing Cycle for Non-critical Medical Devices

1. No precleaning is required; however, wipe off cement/composites directly after reprocessing.
2. Disassemble instruments, open the hinges, or unfold all jaw parts.
3. After each dental routine, disinfect and clean all noncritical medical devices using a disinfectant wipe or a single-use cloth and a spray disinfectant.
4. Visually inspect medical devices for their cleanliness, and ensure that no organic residues including encrustations, smut or films are evident.
5. Dry and, if necessary, re-assemble items.
6. Inspect noncritical medical devices for visible damages and defects to the surfaces.
7. Use protective packaging such as protective covers and inlays, label packaging, and store noncritical medical devices in a dust-free, dry, and contamination-free environment.

Automated Procedures: The Washer Disinfector

The manual disinfecting and cleaning by means of immersion baths can be replaced by the use of a washer disinfector that cleans and thermally disinfects medical devices. It is imperative that these automated machines operate on validated procedures and that revalidation occurs at least once a year. A combination of biological, physical, as well as chemical methods to test the critical parameters is strongly recommended.

Not all medical devices are suitable to be processed in the washer disinfector. The recommendations published by the respective manufacturer should be carefully studied. Typically, instruments must be heat resistant (to a temperature of up to 95°C) and corrosion resistant in the presence of heat and alkalinity. In certain countries, automated disinfecting and cleaning of medical devices has become statutory. A washer disinfector never replaces sterilization procedures.

Recommended Processing Cycle for Critical, Heat-resistant, Nonsensitive Medical Devices

For example mirrors, impression trays, scalpels, forceps, elevators, endodontic items. This processing cycle is not suitable for instruments such as endoscopes, hand-pieces, contra-angles, turbines, and rotating dental burs.

• No precleaning is required; however, wipe off cement/composites directly after reprocessing.
• Choose manual or automated processing.
  In case of manual processing, use a highly effective concentrate suitable for immersion disinfection and cleaning.
• Prepare diluted solution as indicated on the product label.
  Where possible, assemble instruments, open the hinges, or fold open all jaw parts. Immediately after each dental routine, fully immerse all medical devices in the instrument bath.
• Follow exposure times as indicated on the product label.
  Remove medical devices from the bath, rinse under running water if instructed by the product label.
• Visually inspect medical devices for their cleanliness, ensure that no organic residue including encrustations, smut, or films are evident.
• Dry and re-assemble items.
  Inspect medical devices for visible damages and defects to the surfaces, blade geometry, dimensional stability, or movement of rotating instruments.
• Where possible, perform functionality check such as with regards to conductivity, transmittance, movement of rotating instruments, mobility of mobile construction elements, dynamic friction, and sharpness. (Blunted, defective, or damaged medical devices are not recommended for patient use.)
  If necessary, oil all joints carefully with a small amount of suitable lubricant.
• Critical medical devices should always be sterilized – if suitable for sterilization – using an class B autoclave regardless of the chosen processing method (manual vs. automated). If not suitable for sterilisation, use protective packaging such as protective covers and inlays. Always label packaging and store medical devices in a dust-free, dry, and contamination-free environment.
• Pack instruments using sterile pouches, leave all joints open, and ensure that sharp edges do not tear the sterilisation pouch.
• After sterilization, check for sterile pouch integrity, moisture, or contamination.
• If found, repack and resterilize, followed by a second check.
• If none found, label medical devices as “sterile,” state date up to which safe application is possible, and store sterilized medical devices in a safe manner that eliminates the possibility of contamination. Never store disinfected/sterilized medical devices on window sills or anywhere adjacent to heating and air-conditioning vents.
• Periodically check expiration date and resterilize if safe storage period has expired.

It has been reported that the use of the autoclave for certain medical devices made of biomedical polymers can lead to the softening or degradation of these medical devices, thereby irreversibly altering their surfaces and structure.

Recommended Processing Cycle for Critical Medical Devices such as Rotating Dental Instruments

• Place rotating instruments into burbath container immediately after use.
• Use of a highly effective, ready-to-use solution suitable for both immersion disinfection and cleaning.
• Ensure that all burs are fully immersed in the bath.
• Follow exposure times as indicated on the product label.
• Only rinse burs with water if instructed by the product label.
• Leave to dry, visually inspect for cleanliness, and if necessary, use bur brush for any residues.
• Inspect functionality such as sharpness of burs, extent of abrasive wear, movement of rotating instruments, and check for any signs of defect or damage such as corrosion.
• If material is suitable for sterilization, it is highly recommended to sterilize burs. If not suitable for sterilization, use protective packaging such as protective covers and inlays.
• Pack instruments (e.g. using sterilization pouches).
• After sterilization, check for sterile pouch integrity, moisture, or contamination.
• If found, repack and resterilize, followed by a second check.
• If none found, label medical devices as “sterile,” state date up to which safe application is possible, and store sterilised medical devices in a safe manner that eliminates the possibility of contamination.
• Store medical devices in a dust-free, dry, and contamination-free environment.
• Never store disinfected/sterilized medical devices on window sills or anywhere adjacent to heating and air-conditioning vents. Periodically check expiration date and resterilize if safe storage period has expired.

Tip: Ultrasound Cleaning Bath

A good disinfection and cleaning product designed for rotating and surgical instruments contains protein-dissolving agents making pre- and postcleaning redundant. Remove persistent residue by using a bur brush or place burs together with the burbath container and disinfectant in the ultrasonic cleaning bath. Pour some water or disinfectant solution into the ultrasonic cleaning bath and use ultrasound cycle of 2 to 5 minutes. Note: not all burs and instruments are suitable for cleaning in the ultrasonic cleaning bath. Most ready-to-use disinfection and cleaning products for burs are alcohol-based and thus unsuitable for burs made partly or fully of aluminum or copper.

Recommended Processing Cycle for Heat-labile Medical Devices

Certain medical devices such as endoscopes are heat labile and cannot be placed in washer disinfectors. For the automated processing of endoscopes, use an endoscope disinfection machine.

• For the manual disinfection and cleaning, use a high-level product based on aldehydes or “peracetic acid.”
• Follow exposure times as indicated on the product label.
• Pack medical devices (e.g. using sterilization pouches).
• After sterilization, check for sterile pouch integrity, moisture, or contamination.
• If found, repack and resterilise, followed by a second check.
• If none found, label medical devices as “sterile,” state date up to which safe application is possible, and store sterilised medical devices in a safe manner that eliminates possibility of contamination.
• Never store disinfected/sterilized medical devices on window sills or anywhere adjacent to heating and air-conditioning vents. Periodically check expiration date and resterilize if safe storage period has expired.

Recommended Processing Cycle for Medical Devices Made of Sensitive Material or Complex Design

• Immersion disinfection should not be used for hand-pieces, contra-angles, and turbines.
• Use disinfectant wipes for external disinfection and cleaning of turbines, hand-pieces, and contra-angles.
• Where possible, disassemble or fold open all jaw parts and hinges.
• Use high-level spray or rinse products for the internal disinfection and cleaning of the air and water channels.
• Follow instructions and exposure times as indicated on the product label.
• It is highly recommended to sterilize all turbines, hand-pieces, and contra-angles. If material is suitable for sterilization, it is highly recommended to sterilize burs. If not suitable for sterilisation, use protective packaging such as protective covers and inlays. Always label packaging and store medical devices in a dust-free, dry, and contamination-free environment.
• Pack instruments using sterile pouches, leave all joints open, and ensure that sharp edges do not tear the sterilisation pouch.
• After sterilization, check for sterile pouch integrity, moisture, and contamination.
• If found, repack and resterilise, followed by a second check.
• If none found, label medical devices as “sterile,” state date up to which safe application is possible, and store sterilised medical devices in a safe manner that eliminates possibility of contamination
• Never store disinfected/sterilized medical devices on window sills or anywhere adjacent to heating and air-conditioning vents. Periodically check expiration date and resterilize if safe storage period has expired.

The Processing of Single- and Multiuse Medical Devices

Some medical devices can only be reprocessed safely a limited number of times. The information provided by the manufacturer must be carefully read and followed, and ideally, every processing and use of such medical devices should be documented. For instance, tracking can be achieved by attaching synthetic colored rings to the instruments.

It is not advisable to reprocess medical devices marked as a “single-use device” as their functionality or hygienic condition after processing cannot be guaranteed. While there are some single-use medical devices that can legally be processed according to validated procedures, the possible risks to patients and staff far outmeasures the potential gains.

Green Means Go, Red Means Stop: The Necessity for Robust Disinfection Practices

The level of biological contamination of medical devices varies greatly regardless whether they were used in treatment or not. More importantly, contamination is often invisible. Aerosol particles, dust, even spatter can contain pathogens. Similarly, both the patient’s blood and saliva can contaminate medical devices during a dental routine. Other potential sources for contamination include human body fluids. Other than blood, human tissue and even tooth fragments can carry pathogens.

Robust hygienic practices and the implementation of rigorous processing standards for medical devices are therefore absolutely imperative.

For this reason, every dental/medical practitioner is required to implement safe procedures for the processing of medical devices, which include surgical and rotating instruments as well as accessories such as napkin holders. It is also the responsibility of the dental/medical practitioner to ensure that all staff who are involved in the use or management of any decontamination equipment or processing of medical devices has undertaken relevant documented training and has received appropriate updates. In addition, every dental/medical practitioner must appoint a staff member with appropriate qualifications and level of training to declare medical devices as sterile and monitor their safe storage. Continuous training of staff is, therefore, essential for maintaining acceptable standards of infection control. The training must be comprehensive and cover topics such as quality-assured work practices, sterilization procedures, processing of medical devices, and health hazards. Provision should also be made for the documentation of all staff training, and records should be kept for several years.

It is also the duty of every dental practitioner to identify designated and color-coded zones for the use, processing, and storage of medical devices. In order to avoid any recontamination of previously cleaned products, this is strictly a one-way process. Moreover, identification of such zones ensures that in the event of injuries to the dental/medical team, appropriate actions can be taken if it is known in what zone the injury took place. For example, small cuts or pricks received in the yellow or green zone simply require a high-level disinfectant. Injuries received in the red zone require full documentation and possibly a visit to the local General Practitionel. The introduction of a simple color-coded system prevents cross-contamination and can be easily implemented for instance by using colored tape on the floor.

Zone Concept
To distinguish between contaminated and clean areas, the following system is recommended:

The Quality Issue: Not All Instrument Disinfectants and Cleaners Are the Same

It is very important to buy instrument disinfectants and cleaners that can be trusted. A high-level disinfectant product needs to be at least bactericidal, virucidal including HBV/HIV, and fungicidal. It is essential that the chosen product was tested by independent laboratories and not only by the manufacturer. To avoid fixation of blood and proteins on instruments, it is advised to choose an aldehyde-free product unless its intended use is for the disinfection of endoscopes.

The characteristics of a high-quality instrument disinfectant are a broad effect spectrum, short exposure times, high instrument material compatibility, economical in use, biodegradable, and easy to use. Moreover, a high-quality instrument disinfectant contains anticorrosion agents and prevents the fixation of blood and protein on the instruments.

It is important to remember that immersion disinfection requires the full immersion of the medical devices in the solution. The air must have completely vacated any cavities. The exposure times as indicated on the product label must be followed closely, and the bath solution should be renewed two or three times a week depending on the degree of contamination. A daily bath change is recommended. The use of distilled water for rinsing the instruments after the bath is recommended.

The ultrasonic cleaning bath is ideal for instruments with persistent residues such as cement or plaster. Many ultrasonic cleaning products are not suitable for the cleaning of color-coded instruments and instruments fully/partly made of or with natural bristles, nylon, or aluminum. It is not advisable to place soft items such as rubber wheels into the ultrasonic cleaning bath as the ultrasound waves are simply absorbed.

The Quality Issue: Not All Sterilizers Are the Same

It is very important to use a sterilizer that you can trust. In dentistry, class B autoclaves are commonly used and they are designed to meet strictest European standards. Typically, gentle sterilization takes place at 121 °C. It is imperative that the autoclave reach the correct temperature for the correct amount of time at all times in order to guarantee that heat-resistant spores such as clostridium are inactivated. Certain germs such as spongiform encephalopathies require much higher temperatures (134 °C) or longer sterilization times (at least 1 hour).

The use of chemical indicators, sometimes integrated into sterilisation pouches and autoclave tapes, can confirm whether the sterilization process has killed all microbes. These chemical indicators simply change their color once the medical devices inside the pouch have been autoclaved sufficiently. These indicators are a great “little helpers” to monitor the effectiveness of each sterilisation cycle.