Instrument cleaning and sterilisation in daily practice

Laura Yates, Technical Manager, dentisan

Aims & Objectives

  • Teach readers about the three methods of instrument cleaning in the dental practice environment
  • Help readers understand that instruments that are not properly cleaned cannot be effectively sterilised
  • Help readers to understand the benefits of rigorous cleaning and sterilisation procedures

Learning Outcomes

  • Readers will understand that there are three methods of instrument cleaning in the dental practice environment and the benefits and drawbacks of each
  • Readers will understand the principles of cleaning and disinfection
  • Readers will understand why robust cleaning and sterilisation procedures are important

This article relates to GDC development outcome C

The three principal methods of cleaning reusable dental instruments are:

  • manual cleaning;
  • manual combined with ultrasonic cleaning;
  • cleaning using a washer-disinfector.

According to HTM 01-05 guidelines, effective cleaning of instruments is an essential prerequisite before sterilisation and will reduce the risk of transmission of infectious agents. It is advised that wherever possible, cleaning should be undertaken using an automatic and validated washer disinfector in preference to manual cleaning, as a washer disinfector includes a disinfection stage that renders instruments safe for handling and inspection. However, it is recognised that manual and ultrasonic cleaning remain the principal methods of cleaning reusable instruments in dental practices.

It is further advised that instruments are cleaned as soon as possible after use, as they are likely to be more easily cleaned than if left for a number of hours before reprocessing. If cleaning immediately after use is not possible, immersing the instruments in water or the use of a foam spray designed to maintain a moist environment, is considered useful in aiding subsequent decontamination and removal of protein and debris.

Manual Cleaning

HTM 01-05 Section 3.3 states that “manual cleaning, governed by an appropriate protocol, is acceptable within the essential-quality-requirements framework. Within the best-practice framework, however, manual cleaning should be considered only where the manufacturer specifies that the device is not compatible with automated processes (including ultrasonic cleaning) or when the washer disinfector is temporarily unavailable (for example for repair or validation)”.

The main reason why manual cleaning is not considered best practice is that whilst in principle it is the simplest method to set up, it is hard to validate because it is impossible to create a repeatable process every time instruments are cleaned. Compared to other cleaning methods, manual cleaning also presents a greater risk of sharps injuries to staff. In spite of the limitations of manual cleaning, HTM 01-05 states that it is important for each practice to have the facilities, documented procedures and trained staff to carry it out as a backup for when other methods are not appropriate or available. This method must also have systems in place to avoid recontamination of clean instruments.

Ultrasonic cleaning

Instruments can also be cleaned using an ultrasonic bath. This method, when compared to manual cleaning, reduces direct contact with contaminated instruments and decreases the risk of cuts or sharps injuries to staff.

Ultrasonic cleaning can be useful for the removal of debris prior to processing in a washer disinfector, particularly from instruments with hinges and/or intricate parts. However, one important exception is the processing of dental handpieces, unless there is confirmation from the manufacturer that the devices are compatible with ultrasonic cleaning.

It is important that the cleaning solution used in ultrasonic baths is maintained, cleaned and changed at regular intervals. The solution must be changed when it becomes heavily contaminated, or otherwise at the end of every clinical session, as any build-up of debris will reduce the effectiveness of cleaning. It is also important that staff are made aware of the need to assess when a change of solution is necessary.

After ultrasonic cleaning, instruments should be rinsed and as with all other cleaning methods, should be inspected for cleanliness, preferably under a magnifying lamp, and if possible for any wear and damage before sterilisation. Again it is important to stress that instruments that are not scrupulously clean cannot be effectively sterilised.

‘Best-practice’ washer disinfector

Using a washer disinfector is the preferred method of cleaning dental instruments because it offers the best option for the control and reproducibility of cleaning. This cleaning process can be effectively validated and it can perform the processes of cleaning and disinfection consecutively.

A typical washer disinfector cycle for instruments includes the following five stages:

  1. Flush – removes ‘difficult’ gross contamination, including blood, tissue debris and bone fragments. A water temperature of < 45°C is used to prevent protein coagulation and fixing of soil to the instrument.
  2. Wash – removes any remaining soil. Chemical and mechanical processes loosen and break up contamination adhering to the instrument surface. Detergents used in this process must be specified by the manufacturer as suitable for use in washer disinfectors.
  3. Rinse – removes detergent used in the cleaning process.
  4. Thermal disinfection – The load temperature is raised and held at the pre-set disinfection temperature for the required disinfection holding time.
  5. Drying – purges the load and chamber with heated air to remove any residual moisture.

For those using washer disinfectors it is recommended to use a low foam, low residue, non-caustic detergent coupled with a rinse aid that allows rapid drying and reduces water spotting. Both detergent and rinsing agent must be formulated to operate in both hard and soft water areas, helping to prevent scale build-up in rinse jets and pipes, thus reducing the likelihood of future maintenance issues.

Easier cleaning

There is now a wide selection of detergents and products designed for the cleaning and maintenance of dental instruments and many are specially formulated. These include enzyme-based cleaners that use the presence of an enzyme blend to act as a biological catalyst. This speeds up the chemical breakdown of any proteins present into smaller units that can be more easily removed from the surface of instruments.

Detergents must be suitable for each specific cleaning process, have no adverse impact on the instruments, equipment nor the environment and be safe for staff and patients alike. Efficient, correct and thorough cleaning is a central part of dental instrument reprocessing and all members of the dental team must be aware of the procedures required to maintain a safe, compliant and effective working environment.