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Automated Instrument Reprocessing

Save Time for Direct Patient Care

There are two technological advances that offer significant time and safety improvements over commonly practiced instrument processing techniques and are becoming more available for noninstitutional use. The first is the automated washer/disinfector for presterilization cleaning and drying; the second, the class B pre- and post-vacuum sterilizer.


Automated Washer/Disinfectors

Most infection control and work efficiency experts recommend reducing manual handling steps in instrument processing, wherever possible. Countless hours, broken or damaged instruments, and probable injuries have been saved by the introduction of ultrasonic cleaners, enzymatic cleaning solutions, and instrument cassettes. The next generation of presterilization technology appears to be automated washers since they prepare contaminated instruments for sterilization rapidly, safely, and efficiently with significantly reduced manual labor. 


Staff time is one of the most important expenses of operating a dental practice, yet many practice owners or managers continue to avoid automatic washers due to the initial cost and the perception that automated instrument washers/disinfectors are only justified for large clinic use. In fact, dental offices with more than four chairs will benefit from the many advantages of automated washer/disinfectors as a part of a larger concept--a systems approach to instrument management. Commercial literature and antidotal information suggest that automating instrument reprocessing can significantly improve employee time efficiency, ergonomic challenges, asepsis, worker safety, space efficiency, staff morale, and office desirability for both the staff and patients.


Essential components of upgrading a sterilization center to include an automated instrument washer:

  1. Adequate under-the-counter space for a washer--about the space of a dishwasher.
  2. Room layout that places the washer correctly along the dirty-to-clean instrument recirculation pathway.
  3. Instrument organization system (ie, instrument cassettes).
    1. High-quality metal cassettes and high heat, resin-reinforced plastic cassettes are recommended.
    2. Select cassettes that have side drain holes.
  4. 220-volt electrical wiring.


Automated washer/disinfector tips:

  1. The typical wash and disinfection cycle takes 50 minutes.
  2. The wash cycle alone requires 30 minutes.
  3. For occasional rapid processing, some offices retain one ultrasonic cleaner.
  4. Naturally occurring minerals found in tap water may have an adverse effect on instruments in washers and at any step along the instrument pathway.  Chlorides and silicates pose the greatest challenge, as these residues can cause discoloration and corrosion.
    1. Some regions of the country have higher mineral concentrations than others. Water should be tested and if necessary, an appropriate water filter system should be provided.
    2. A final rinse cycle with filtered (deionized) water is the most effective way to remove potentially harmful mineral residues. 
  5. Use of improper detergents can affect cleaning efficacy and also be a source of instrument corrosion. Products recommended by the washer/disinfector manufacturer should only be utilized; never use a product that contains sodium hypochlorite (bleach).
  6. Some instruments are not suitable for processing:
    1. Plating may be removed from plated instruments such as syringe barrels.
    2. High carbon content instruments may be corroded.
    3. Lower-quality instruments (ie, some periodontal scalers) may be damaged.
  7. Counter space needs are reduced because soiled instruments may be stored in the washer.  Spraying instruments in cassettes with an enzymatic foam before loading will help prevent organic material from adhering to instruments for better washer results.
(Continued from page 1 )

Heat Sterilizers

There are three types of table-top sterilizers frequently used in dentistry:

  1. Steam under pressure (the autoclave) is the most common method of sterilizing wrapped and unwrapped items that are not sensitive to heat and moisture.  Each item must be exposed to direct steam contact at a required temperature and pressure for a specified time. There are two types of autoclaves: gravity displacement and prevacuum sterilizers.
    1. Gravity displacement

Steam is admitted through lines to the chamber or is generated inside the chamber. The steam then forces unsaturated air out of the chamber through a vent. Air pockets can develop among poorly packaged or loaded instruments, leading to cool spots where sterilization does not occur.

    1. Prevacuum sterilizers pump out air, creating a vacuum in the chamber prior to pressurization with steam. 

Vacuum provides more rapid and positive steam penetration through chamber. Prevacuum sterilizers should be tested periodically with an air removal test (eg, Bowie Dick test) to detect air leaks or inadequate air removal. Air not removed from the chamber will interfere with the steam contact.  Any sterilizer that fails the air removal test should not be used until repaired and retested.

  1. Dry heat sterilizers, primarily used in orthodontics and for instruments, are likely to be damaged by moist heat.  Dry heat sterilizers utilize high heat and time, however, the chamber is not under pressure. There are two types of dry heat sterilizers: Static-air, or “oven type”, and forced-air type, or “rapid-heat-transfer” type.
    1. Static-air dry heat sterilizers: heating coils at the bottom of the unit cause hot air to rise through convection.
    2. Rapid-heat-transfer sterilizers: heated air is circulated through chamber at high velocity, reducing time necessary for cycle.
    3. Instruments.
  2. Unsaturated chemical vapor sterilizers employ a mixture of alcohol and .23% formaldehyde heated under pressure.
    1. Instruments must be dry before sterilizing.
    2. Carbon steel (eg, dental burs, some blades, scalers) corrode less due to absence of water.
    3. Hazardous waste regulations may apply to used solution.


All sterilizers are subject to human error (ie, overloading, poor packaging, and operating without proper fluid levels or maintenance). The more automatic a sterilizer, fewer manual errors are likely.

Prevacuum (Class B) steam sterilizers employ both pre- and post-vacuum cycles to remove both air and moisture from the chamber.  A vacuum condition is created in the sterilization chamber, creating a more efficient and active entry, circulation and later removal of the sterilization agent (steam) into, throughout, and out of the chamber, including within hollow, porous, and bagged or wrapped items. Large models of Class B steam sterilizers have been used in large clinics and hospitals for many years. Recently, smaller table-top models have become available, offering more rapid and efficient sterilization than other autoclaves.

The term “Class B” refers to terminology used in the European Standard, EN 13060 which applies to small steam sterilizers.  Class B sterilizers are intended for sterilizing all wrapped or nonwrapped, solid, hollow, and porous products, including all heat-tolerant dental instruments and handpieces. Several European manufacturers have advertised Class B sterilizers in Europe and the term has carried over to the US for both imported and domestic models. The vacuum drying process is designed to ensure there are no wet pouches that may compromise the sterility of the instruments.  An automatic door remains sealed until risk of wet pouches is eliminated. In some models, built-in, nonrecirculation tanks reduce maintenance time and effort and also keep the chamber cleaner.

Class B sterilizers operate at a higher temperature than standard autoclaves (276°F compared to 245°F).  Caution should be used when processing plastics and rubber items that may melt or warp. 


Advantages of using cassettes:

  1. Organize instruments, accessories, and disposables per procedure for quick identification and access. This is evident when wearing magnifying loupes: knowing the location of each instrument makes finding it easier, with less visual refocusing.
  2. Protect instruments and extend their use-life, preventing breakage, damage, and misplacement during processing.
  3. Eliminate time needed to sort instruments while processing.
  4. Reduce manual handling of contaminated instruments, thereby reducing risk of injuries.
  5. Standardized instrument cassettes increase storage efficiency.
  6. Cassettes are the key module that move instruments through the cycle of preparation, storage and work flow, allowing maximum efficiency of both automated devices and operator use.
  7. Instruments in cassettes provide patients with an orderly, aseptic impression of the office.
  8. Based on customers’ experience, one manufacturer estimates that 30 to 40 minutes per day per staff member is freed up for more profitable activities by using cassettes.


Cassette Tips:

  1. To avoid corrosion, separate stainless steel from carbon steel.
  2. Temperatures above 350° F (176° C) can damage cassettes.
  3. Follow manufacturers’ directions, never overload.
  4. Band instruments to identify procedure, clinician, and/or position in the cassette.
  5. Cassettes packaged in flat sterilization wrap should be repackaged and reprocessed in 30 days, if not used.  Properly sealed sterilization pouches do not have a time limit.


*OSAP member and consultant in infection control.

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