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Fundamental principles in designing reprocessing areas

By Christian Stempf
June 23, 2020

It is recognized all too often that very little consideration is given to sterilization or reprocessing areas in either existing or newly designed dental practices. And yet reprocessing instruments between patients is crucial to meet today's hygiene rules in dental offices. Dental practitioners also have a moral and legal ‘duty of care’ calling for effective, well-defined and implemented infection control measures to prevent the transmission of infectious diseases to patients and staff

Beyond the purely regulatory and safety aspects, many dentists have made the sterilization area a key asset for their activity. Located in a prime and visible location lets patients understand up front that their health and safety is important. The staff don’t hesitate to share this passion for hygiene with patients, happy to answer any questions they may have. Flattered by this attention, it makes the patient feel confident and secure. To create new reprocessing areas or enhance existing ones is not an "insurmountable" challenge. It simply requires some basic principles this article will outline.

Having sufficient space dedicated to the reprocessing area is essential. In most of the cases it is undersized. The room must be functional, well lit and in proportion to the size of the dental practice and volume of instruments to be reprocessed. There must be space for cleaning and sterilization devices with their respective accessories as well as enough bench space for intermediate stages i.e. before/after cleaning; before/after packaging and after sterilization.

The first fundamental principal is to have two areas in the room; a dirty zone and a clean zone. Rationally, instruments must travel in one direction from the dirty zone towards the clean zone. As a consequence of this one-way flow, processed (clean) instruments must not enter the dirty zone; hence one preferred design for a reprocessing area would be rectangular - a corridor with two doors (IN & OUT) (Fig 1). Both zones require ventilation and the airflow should be designed to prevent air from the dirty zone being forced into the clean zone. Where the areas are beside one another, this can be achieved by pressurizing the clean area though air conditioning outlets and/or having exhaust fans in the dirty area.

At the entrance, there should be a hand washing basin equipped with an eye washing station, vital in case of accidental splashing of disinfectant or any harmful fluid. Liquid soap and hydro-alcoholic gel dispensers should have an automated dispensation (or elbow operated) which avoids contaminating them with soiled hands. It is recommended to pat dry hands with paper tissues.

Form follows function

The configuration of each part of the room follows the reprocessing steps i.e. pre-disinfection, rinsing, cleaning, rinsing, drying, packaging and sterilization. This room must not be used for any other purpose. Floors and working surfaces must be smooth, avoiding sharp corners and edges and be easy to clean and disinfect.


Waste should be disposed of into bags or containers through openings in the bench. Sharps and cutting items must be safely disposed of in specific plastic containers to protect staff, be collected and processed by specialized companies in treating contaminated waste. It is imperative to follow your local national guidelines as they may vary from country to country.

Pre-disinfection – Soaking

In order to prevent blood, saliva and debris from drying, all used and non- used instruments must be soaked as soon as possible after the procedure, using one or more disinfecting containers depending on the number, type and size of the instruments i.e. a small one for burs and files, bigger one(s) for bulk of items, kits or cassettes, etc. Note the manufacturer’s guidelines NOT to immerse or soak certain instruments such as transmission instruments in solutions! The manufacturer’s guideline on the concentration and contact time of the chemicals must be strictly observed. The temperature of the solution should not exceed 40-45°C, thus preventing coagulation of blood proteins which increases the challenge of cleaning.

Another benefit of this crucial first step is the reduction of the microbial population, decreasing the risk of infection during handling and cleaning. A basin will permit rinsing of the instruments with tap water aiming to remove any residual chemicals particularly in hollow and hinged items. Chemical residues could lead to irreversible staining and damage to instruments should a thorough rinsing step be missed.


The cleaning step is of utmost importance. Mechanical cleaning by means of an ultrasonic cleaner offers a good level of performance. Note: Manual cleaning is discouraged, as it is the least efficient method of cleaning particularly for complex or hollow instruments and rough surfaces. The degree of cleanliness relies on the operator's experience and appreciation and also raises the risk to staff of skin penetrating injuries.

In order to remove chemicals and bioburden, all instruments must be thoroughly rinsed with tap water in a second basin. Ideally this would be followed by a second rinse with demineralized water to eliminate residues and salts present in tap water that could lead to whitish stains on sterilized instruments.

Washers or washer-disinfectors are a preferred mechanical cleaning method thanks to the higher performance of the cleaning cycle validated by the manufacturer in compliance with stringent applicable standards (i.e. ISO-EN15833-1/-5). The cycle process includes prewashing, rinsing, washing and drying without manual intervention which allows free space on the bench, sparing the soaking container/s and one basin. It is wise to keep the second basin.

Buffer bench space after cleaning

Next to the washing station, space is reserved to check the dryness, cleanliness and integrity of all instruments. Compressed air will assist drying hinged instruments (scissors, forceps, etc.) which may also require periodic lubrication. Transmission instruments will be maintained at the same place. Internal and external cleaning as well as lubrication should be mechanically assisted by means of an automated process validated by the manufacturer. It is virtually impossible to manually complete internal cleaning.

Packaging – Sterilization

An area should be considered for a pouch sealing device as well as an area for the temporary storage of packages prior to process in the bench top sterilizer. To ensure safe and efficient sterilization it is crucial to check the load and cycle–type for compatibility. Selecting a cycle which is not designed and validated for the type of load (instruments) will lead to non-sterile products.

Additional space beside the sterilizer is intended for cooling and labeling of packages which have been released by the operator for storage and use (Fig 3). Special attention must be paid to ensure that pouches are hermetically sealed and are completely dry. Damp instruments/packages are not acceptable as sterile.

For extended storage time, pouched items should be stored outside the reprocessing area and surgery (operatory) in clean and dry drawers or cabinets. In doing so, single pouched items could safely be stored for up to 3 months.


All readers should reflect on these two definitions:
Reprocessing: "All activities required to ensure that a used medical device is safe for reuse" (ADA Guidelines for Infection Control - 2012).
Sterilization: "validated process used to render a product free from viable microorganisms".

"…the presence of a viable microorganism on any individual item can be expressed in terms of probability. This probability may be reduced to a very low number; it can never be reduced to zero." (ISO/TS 11139:2006).

In other words; the better each step is accomplished, the closer to "zero". Always bear in mind that each step of the reprocessing cycle is important. None shall be rushed or skipped which would compromise sterility and the safety of patients and staff.

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