The essentials of disinfection and decontamination
Kathy Porter, Senior Dental Nurse (Decontamination) at Birmingham Dental Hospital, highlights her perception of "Best Practice" for disinfection and decontamination within Hospital and General Practice environments.
Infection prevention and control is the single most important practice that all the dental team are involved in. It is important to emphasise that infection prevention and control is the responsibility of everyone, not only within the team but also the people that visit the surgery and they should have every encouragement to participate in good practice. This can be achieved by promotional material on view and the evidence that your practice is actively involved in ensuring its patient health and wellbeing.
The General Dental Council (GDC) recognises the importance of this subject by making it a compulsory subject for Continuing Professional Development (CPD) for not only Dentists but also Dental Care Professionals (DCP's).
The whole subject of Infection Prevention and Control is huge and I can only cover one small part of this in this alticle. Hopefully you will feel that it has given you food for thought and inspires you to do more reading and research of your own. My book, The Dental Nurses Guide to Infection Control and Decontamination by Quay Books, gives more in-depth information and sources for further study.
The GDC requires DCP's to complete 10 hours of disinfection and decontamination CPD in every 5 year cycle. This is a small but essential part of the whole subject and is arguably the most important. There can be no effective infection prevention and control without effective and efficient disinfection and decontamination. These two are similar but not the same and the differences must be clear to whoever is performing the task. Confusion could lead to patients being put at risk.
Disinfection has been defined as a process used to reduce the number of micro-organisms, but which does not usually kill or remove all the micro-organisms, rather it reduces them to a level which is not harmful to health.
Decontamination is a term used for the destruction or removal of microbial contamination to render an item safer to handle.
Basic Disinfection procedures
Disinfection should only be used as a means of decontamination for those items or pieces of equipment which cannot be sterilised by autoclaving. It should never be used as a "quick fix" to save time.
In general this relates to large pieces of equipment such as the dental chair and unit, work surfaces etc. The only small items which should be disinfected are items such as protective glasses, some cheek retractors, some photographic minors etc. The key phrase that drives this is "follow the manufacturers' instructions"; this also applies to decontamination advice and sterilisation.
No item designated as "Single Use" should ever be disinfected, decontaminated or sterilised and used a second time.
Large items of equipment should be cleaned using an appropriate cleaner as advised by the manufacturer and then wiped over using a recommended disinfectant. This should be made up to the correct concentration when necessary and applied in the recommended way.
When choosing a suitable disinfectant the bactericidal, virucidal and fungicidal properties should be carefully studied as these are essential for an effective disinfectant. A product which has all these properties will give the best possible spectrum of protection.
For small items, once they have been disinfected, they can be stored in sterilisation pouches to help prevent recontamination. For such items, it may be appropriate to use a similar solution as that used to disinfect items to be sent to the laboratory or for repair. This will entail soaking them in the solution for the recommended time and then rinsing and drying them. For things like protective glasses all that can be done is to wipe them thoroughly using a disinfectant solution or wiping them with an alcohol impregnated wipe.
Whenever handling, mixing or disposing of disinfectant solutions, Personal Protective Equipment must be worn. There should also be a Control of Substances Hazardous to Health (COSHH) risk assessment carried out, documented, updated regularly and kept in the area where the substance is being used. It is also essential that all staff who come into contact with it or use it, are adequately trained in its safe use and storage.
Decontamination
The whole decontamination process is one which renders a contaminated item safe to use on a subsequent patient, by virtue of the fact that all pathogenic micro-organisms have been killed or removed from the item. The process is complete when the item has been sterilised, usually by autoclaving which is the stage when all the pathogens are destroyed. This can only be achieved if the item has been effectively decontaminated before sterilisation.
It should be remembered that although sterilisation will kill or destroy all pathogens it will not necessarily destroy Prions which are not living organisms, but mutant proteins.
The decontamination prior to sterilisation must remove all deposits, blood and saliva. The enzymes in blood and saliva will prohibit the action of the steam against the material of the item, thus giving incomplete sterilisation. Any debris left on the item will not allow penetration of the steam underneath it, so that area will not be sterile.
The first stage in this process is cleaning. This can be achieved by one of two methods:
i) Manual Cleaning
Manual cleaning should be restricted to those large items which cannot be mechanically cleaned i.e. the dental chair and unit etc. It is not recommended for instruments etc. For two main reasons:-
a) Danger of the operator receiving a percutaneous (sharps) injury.
b) Thorough removal of all blood, saliva and debris is very difficult manually.
However it is a fact that not all dental practices have a mechanical cleaning facility, so instruments have to be cleaned manually. This should be carried out in a designated sink which is used for this purpose only and is deep enough so that the instruments can be totally immersed in water during cleaning. Debris should be removed using either a disposable or autoclavable brush or some form of disposable scourer. A brush or scourer should not be used on more than one set of contaminated instruments. If a brush is used, it must be autoclaved after each set of instruments has been cleaned.
After cleaning and before loading into an autoclave, they must be checked for visible cleanliness. If they are not clean then they must be cleaned until they are. If clean, they should be thoroughly rinsed, carefully dried, using disposable cloths and then spread out on an autoclave tray.
Full Personal Protective Equipment (PPE) must be worn to perform this operation.
ii) Mechanical Cleaning.
There are two main types of mechanical cleaner, an Ultrasonic Bath or a Washer / Disinfector. Manufacturers' instructions must be followed for the installation, use and servicing of both types of machine. Instruments decontaminated in either machine, must be sterilised before use. They do not sterilise only decontaminate.
Ultrasonic Baths
These work by using high frequency sound waves to agitate the solution and produce millions of tiny bubbles, which implode against the instrument, forcing the debris, blood or saliva off. They must be subjected to weekly tests as to their efficiency, which must be documented and kept for audit purposes. They also need to be calibrated when first - bought to find the optimum time that instruments should stay in there for.
The solution should be a recognised enzymatic solution which will break down the enzymes left by blood and saliva which would inhibit sterilisation. It is not sufficient to just put washing up liquid into the water.
Instruments must be put into a basket in the bath and not straight onto the floor of the bath to allow circulation of the cleaning fluid. The bath should also have a tight fitting lid which must always be in place when the bath is in use. This is because an aerosol is produced by the bubbles, which is made up of a mixture of cleaning solution and contaminated particles from the instruments.
After removal from the bath, they must be rinsed to remove the enzymatic cleaner and then carefully inspected for cleanliness. If visibly clean then they should be dried and spread out on an autoclave tray and then autoclaved.
As with manual cleaning full PPE must be worn by staff dealing with contaminated instruments and using the ultrasonic bath. There should also be COSHH risk assessments available for the solutions used.
The bath should be emptied and cleaned at least at the end of every session but more often if the water becomes heavily contaminated or obviously dirty. It should be emptied every time it is used to decontaminate heavily blood contaminated items such as forceps, elevators or surgical instruments.
Washer / Disinfectors
These are a relative new innovation for dental surgeries, although they have been used for some time in large purpose built decontamination facilities. They are, basically, sophisticated dish washers. The disadvantages of these machines are - large pieces of equipment, although bench top versions are now available; expensive to buy; time consuming to use; need to have regular maintenance from outside technicians; and need to be plumbed into both the water and waste systems.
There are advantages, these being - give a high level of decontamination; instruments come out dry reducing the risk of percutaneous injury during drying; make the instruments safer to handle; and they decontaminate the lumens inside handpieces etc.
Users must wear full PPE when using the machines and COSHH risk assessments for the solvents used must be available in the area of the machine. All staff using it must be adequately and appropriately trained in its use.
When instruments are removed from the machine they must be checked for cleanliness prior to spreading out on an autoclave tray ready for sterilising.
The mechanical cleaning systems should be the systems of choice but if they are installed, back up systems must be in place to cope with any breakdowns or malfunctions.
The decontamination process is completed by the instruments being sterilised.
Briefly, sterilisation is effected by the action of steam under pressure. This is achieved with a displacement autoclave or a vacuum phase autoclave. The recommendation to Dentists replacing autoclaves is to buy a vacuum phase model as this will ensure the complete sterilisation of all surfaces, including the lumens inside handpieces.
The most commonly used temperature / time cycle is 135°C for a minimum of 3 minutes. Some more delicate instruments need to be sterilised at a lower temperature for a longer time. Again the manufacturer's instructions should be followed. Instruments should be spaced out on the trays to allow adequate exposure of all surfaces to the steam and the autoclave should not be overloaded.
Autoclaves should be drained at the end of each day and left clean and dry. They are also subject to mandatory checks, daily, weekly, quarterly and yearly, all of which must be fully documented and kept for audit purposes.
Disinfection and decontamination should be carried out in a designated "dirty area" and sterilisation in a designated "clean area". There must not be any overlapping of the processes carried out in each area or effective sterilisation will not be achieved.
After sterilisation, instruments taken from a displacement autoclave need to be dried and packed in pouches to be stored. They must not be sterilised in pouches, only instruments going through a vacuum phase autoclave can be packed in pouches prior to autoclaving.
It is imperative that sterilised items are stored in clean dry conditions and used in rotation.
This is only a brief overview of a complicated process and should provide the stimulus to dental nurses to learn more and look at their own disinfection and decontamination practices as well as those of other staff.
About the Author
Kathlyn (Kathy) Porter has been a qualified and now registered Dental Nurse for 38 years mainly spent in various guises at Bilmingham Dental Hospital. Her title now is - Senior Dental Nurse (Decontamination). She is a member of the editorial board of the "Dental Nursing" Journal and also writes articles for them. She has had a book, entitled "The Dental Nurses Guide to Infection Control and Decontamination", published in the spring of 2008.
