Dental practices have a responsibility to provide treatment in an environment where the risks of cross-infection are minimised and implementing effective infection control procedures requires the full compliance of all team members.
Hand hygiene
Hands are the most common way in which microorganisms are transmitted and effective hand hygiene is generally recognised as “the single most important measure for preventing the spread of infection”. The term hand hygiene covers not only hand washing, but also hand disinfection using antibacterial based hand rubs/gels.
There are different levels of hand hygiene depending on the potential for contamination of the hands and the procedure being undertaken:
- Social (10-15 seconds) – removes transient microorganisms using an antimicrobial and is undertaken before general non-clinical activities, including decontamination.
- Hygienic (15-30 seconds) – destroys microorganisms and provides a residual effect using an antimicrobial product from a dispenser. This should be performed before putting on gloves to carry out clinical procedures, after contact with blood and other bodily fluids and between patients.
- Surgical scrub (two to three minutes, ensuring all areas of the hands and forearms are covered) – substantially reduces the numbers of resident microorganisms using an antiseptic hand cleaner and is essential before oral, periodontal and implant surgery.
Alcohol based hand rubs have a key role to play in improving compliance and decreasing potential infection. A paper published in The Lancet advised that in healthcare environments “promoting hand cleansing with an alcohol-based hand rub solution seems to be the most practical means of improving compliance. It requires less time, acts faster, irritates hands less often, and is superior to traditional hand washing.”
When decontaminating using an alcohol rub hands should be free from dirt and organic material. The hand rub solution must come into contact with all surfaces of the hand. The hands must be rubbed together vigorously paying particular attention to the tips of the fingers, the thumbs and the areas between the fingers until the solution has evaporated and the hands are dry.
Dental unit waterlines
Dental unit waterlines (DUWL) can easily become contaminated with microorganisms which rapidly lead to biofilm development. Although the large volumes of water produced are removed by high volume aspiration, some is almost certainly swallowed by the patient and droplets may be inhaled by staff.
A study of water obtained from DUWL systems showed that in 95 per cent of water samples microbial loading exceeded European Union drinking water guidelines. The most common pathogen detected was Pseudomonas spp. Legionella pneumophila, Mycobacterium spp. and Candida spp. were also detected.
Biofilms are responsible for high levels of contamination; water flowing down the biofilm coated waterlines contribute to microbial load in the water as it exits the tubing. Biofilms protect organisms from the effects of heat and chemicals, which reduces their susceptibility to the disinfection process.
Biofilms need to be removed as well as ‘killed’ as a ‘killed’ biofilm may still act as a source of endotoxins allowing
rapid recolonisation of new biofilm. Any disinfectant selected should kill bacteria in the water phase, kill biofilm bacteria and remove biofilm from surfaces.
A study evaluating a range of disinfectants found that most did not meet all three of the above criteria. However a product such as schülke watersafe (previously known as schülke DUWL) provides complete elimination of viable bacteria and 100 per cent reduction of biofilm coverage.
Surface decontamination
HTM 01-05 6.61 recommends that: “The patient treatment area should be cleaned after every session using disposable cloths or clean microfibre materials – even if the area appears uncontaminated.”
When selecting a surface cleaner, consideration should be given to efficacy against a wide range of microorganisms, contact times, material compatibility and ease of use. Taking all of these factors into account will ensure the highest standards of best practice are met for both patient and staff safety.
Surfaces should be wiped down between patients with a high quality disinfectant. Wipes pre-saturated with the disinfectant of choice are usually the preferred format in a busy dental practice as they are convenient to use, disposable and require less storage space than sprays. Wipes also have the added advantage of containing the correct amount of disinfectant.
Alcohol based surface disinfectants possess some of the widest disinfectant kill ranges available. They are rapidly
bactericidal and are effective against Tb, fungi and viruses. Recent evidence has demonstrated that Mikrozid alcohol
based wipes effectively eliminate a range of microorganisms from surfaces, without any protein fixation.
When cleaning surfaces, it is recommended that a double wipe procedure is used. The first wipe cleans the surface and physically removes contaminants including dust, soil, large numbers of microorganisms and the organic matter that protects them. The second wipe disinfects the surface; reducing the number of microorganisms to a safe (or relatively safe) level.
Instrument cleaning and disinfection
HTM 01-05 states it is an essential quality requirement that prior to sterilisation cleaned instruments should be free of visible contaminants. The effective cleaning of instruments before sterilisation reduces the risk of transmission of infectious agents and all instruments must be thoroughly cleaned before autoclaving to remove as much matter as possible.
It is easier to clean instruments as soon as possible after use. Blood, saline and iodine are corrosive to stainless steel instruments and will cause pitting, then rusting if they remain on instruments for any length of time. If a delay is anticipated instruments should be kept moist by immersion in water or an enzymatic cleaner. A foam spray may be used to maintain a moist environment. Dental materials, especially cements, can harden on instruments and should be removed as soon as possible to allow effective cleaning.
Where possible, cleaning should be undertaken using an automated and validated washer-disinfector, in preference to manual cleaning. A washer-disinfector provides control and reproducibility of cleaning.
Manual cleaning should be considered if the instrument manufacturer specifies that the device is not compatible with automated processes. Manual cleaning is difficult to validate and there should be a written procedure available
to ensure consistency in cleaning procedures. Detergents specifically designed for the manual cleaning of instruments should always be used.
Sterilisation
Sterilisation is the process intended to kill all microorganisms and their spores and is the highest level of microbial destruction that can be achieved. After following the cleaning procedures outlined above, instruments should be inspected for cleanliness before sterilisation.
The preferred method of sterilisation for most dental instruments and devices involves saturated steam delivered under pressure at the highest temperature compatible with the product. Effective sterilisation requires steam to have contact with all surfaces of the instruments which should therefore be loaded into the chamber to allow free circulation of the steam.
Sterilised instruments must be protected against the possibility of recontamination by wrapping or storing in a covered container. The type of autoclave used affects the wrapping and storing options. After sterilisation, instruments should be stored in a dedicated area.
References available on request.