Standards in Decontamination

With an ever increasing focus on the importance of infection prevention and control, the need to ensure reusable dental instruments are thoroughly cleaned after each use is more important than ever. In order to ensure that prior to use on patients all instruments are clean, ultrasonic cleaners are fundamental as the first stage in the three part instrument decontamination cycle.

Infection control in dentistry

Infection control has and always will be a subject of paramount importance in medical and healthcare environments. There is increasing awareness, both within the field and amongst the public, of the risks associated with substandard cleaning procedures, highlighting the obligation of every member of the dental team to follow stringent infection control procedures.
The A12 advice sheet states that all instruments contaminated with oral and body fluids must be thoroughly cleaned and sterilised after use. Pockets of debris and bio-burden, if left on the surface of an instrument, increase the risk of infection and cross-contamination by acting as a shield to infectious agents during the sterilisation process. The infection control procedures should protect dental staff as well as patients. It is therefore necessary to recognise the importance of the first of three stages in the decontamination process pre-sterilisation cleaning.

Pre-sterilisation cleaning

The benchmark process for decontaminating medical instruments consists of three stages: cleaning, disinfection and sterilisation.
Cleaning instruments prior to sterilisation is essential. Sterilisation of unclean instruments can cause infectious prions to be baked onto instruments, greatly increasing the likelihood of cross contamination and infection. There are three methods of pre-sterilisation cleaning: manual cleaning, using a washer/disinfector and ultrasonic cleaning.
Dental instruments are often heavily soiled with a variety of contaminants. If these contaminants are not removed prior to sterilisation, then the instrument cannot be considered to be decontaminated. Manual cleaning is the least efficient cleaning technique as it is an invalidated, subjective process where the same results are difficult to achieve each time. Furthermore, it subjects the dental nurse to the risk of infection from sharps injuries.
Washer/disinfectors provide good cleaning results but can struggle to remove heavy contaminants such as dental cement. Only exposed areas of instruments are cleaned meaning contaminants can therefore still be present at the end of the cycle, particularly in hinges, threads and difficult to access box joints. In addition, the cycle of a washer/disinfector can be a long process thus causing problems in a busy dental practice.
Pre-sterilisation cleaning with ultrasonic technology prior to the washer/disinfector eliminates these problems. As well as removing heavy contamination from the complete surface area of the submerged instruments, effective ultrasonic cleaning cycles can be as short as six minutes adding minimal time to the decontamination process.

Ultrasonics in infection control

Ultrasonic cleaning utilises high frequency sound waves, transmitted through a liquid medium. These sound waves create an activity in the liquid called cavitation. This occurs as the sound waves pass through the liquid, causing the formation of microscopic bubbles which are forced to expand. Once they reach a size where they can no longer support their own density, the individual bubbles implode. These implosions are known as cavitation.
The cavitational process creates a scrubbing effect within the liquid as the fluid surrounding the bubble rushes in to fill the remaining space. Where the onrushing fluid contacts the surface area of the item, any contamination is brushed off. The action is similar to that of microscopic scrubbing brushes gently agitating debris off the surface area of any item immersed in the tank. It is this process which allows the complete surface area of the immersed item, including difficult to penetrate box joints, hinges and threads, to be effectively cleaned in every cleaning cycle.
Healthcare guidelines such as HTM2030 and A12 recognise the benefits of ultrasonic cleaning, but suggest that machines should have specific capabilities to ensure that the cleaning process incorporates validation, traceability and safety.
General purpose ultrasonic baths have traditionally been used in industries such as jewellery and machinery component cleaning, but it is not enough to simply use a standard ultrasonic cleaner for reprocessing surgical instruments. If no traceability is provided, operators cannot be sure a complete cycle has occurred at the correct temperature and for the correct time and results cannot be referred to in future.
Without a lockable lid, it is possible to add or remove items from the bath at any time, thus not completing a full cleaning cycle. Furthermore noise levels created by the ultrasonic activity can be invasive and the risk of inhalation of contaminated aerosols exists if the lid is left off. Today, it is no longer enough to subjectively judge that instruments have been effectively cleaned, it is essential that the process is robust, repeatable and able to be validated and are auditable.

Developments in ultrasonic baths

The guidelines specified in documents such as HTM2030 have meant that ultrasonic baths have had to incorporate features to meet these requirements. The Hygea 1250 from Ultrawave is a fully HTM2030 compliant ultrasonic cleaning bath, specifically designed for use in dental surgeries.
Incorporating an electro-magnetic locking lid and integral printer, full process validation is provided after every cleaning cycle. The lid cannot be opened once the cleaning cycle has begun, without showing that it was aborted on the printout and the instruments cannot therefore be considered completely clean. The improved insulation of the MDPE lid cuts down on noise levels and eliminates the risk posed by microbial aerosols.
As well as producing excellent cleaning results, the Hygea 1250 allows a permanent record of every ultrasonic cycle to be kept. It is possible to pre programme all necessary parameters such as date, location, operator name, temperature and cycle time. The integral printer provides a permanent record of the cycle results which must be kept for validation process reference.
A number of software driven control devices are also incorporated into the design of the bath to ensure that the cycle is completed within the operator's chosen parameters. In order to ensure the instruments are fully submerged and can thus be effectively cleaned, fluid level sensors monitor the depth of the water. Ultrasonic energy produced by the bath is monitored by an activity sensor and if this should fail then it will be indicated on the final printout. Temperature sensors ensure the cycle is only valid if the set measurements (usually between 20° and 40° C to prevent coagulation of proteins) are kept to.
The Hygea 1250 incorporates Split-Level-Security meaning that the cleaning cycle parameters are controlled through a separate administration menu. If any of these parameters are not met during the cycle, a clear indication is provided on the validated printout.
In recognition that busy dental practices require the rapid turnaround of instruments, the powerful ultrasonic activity provided by the Hygea 1250 ensures instruments are consistently reprocessed quickly and effectively. Whereas washer/disinfectors commonly have cleaning cycles of more than 30 minutes, ultrasonic baths can process instruments considerably quicker than this independent testing has shown that even the most heavily decontaminated instruments can be fully cleaned in a six minute cycle in the Hygea 1250.

Ultrasonic detergents

A further saving can be made in detergent usage within and testing of the ultrasonic cleaner. The ultrasonic bath needs to be dosed with new cleaning solution (water and detergent) at the start of each clinical session. In an effort to remove the possibility of human error, Ultrawave provide a single shot dose detergent for use in the Hygea� 1250.
Sonozyme is a poly-enzymatic liquid detergent which is packaged in an easy "tear and dose" sachet. Each sachet contains 25ml of detergent, which has been specifically designed to offer the optimum amount of detergent for use in the Hygea 1250's 8 litre tank. The 3 kinds of enzyme in the detergent actively attack, breakdown and digest carbohydrates, proteins and starch, which make up the bioburden found on contaminated surgical instruments, even at lower temperatures. The packaging ensures that no detergent is wasted and that costs are kept to a minimum typically a Hygea 1250 can be dosed with detergent for less than £1.70 per day while contributing to a repeatable, cost effective cleaning cycle time after time.


Although an always important issue in medical and healthcare environments, the awareness of the importance of infection control procedures has grown considerably in recent years. Decontamination of reusable surgical instruments is at the forefront of this and must be seen as a top priority for all members of the dental team. Modern government guidelines recommend that the instrument reprocessing chain is fully validated. The process must be repeatable, minimise the risk of human error and allow complete traceability.
Effectively cleaning instruments is essential in the decontamination cycle and the use of ultrasonic baths is one of the most effective means of carrying this out. Technological developments and stricter guidelines have seen new features incorporated into the ultrasonic baths which are used in the pre-sterilisation cleaning process. The need for validation and traceability is of utmost importance and any ultrasonic bath which has this feature built in reduces the risks associated with infection control, thus ensuring safer procedures for patients, dentists and all dental staff.
As featured in the November-December 2007 issue of Scottish Dentist magazine (