Infection control is an important part of dental practice, particularly in ensuring that surfaces are clean and maintained in a hygienic state. Hygiene in this context refers to the elimination of potentially pathogenic microorganisms, including the bacteria that cause tuberculosis and MRSA
infections.
In order to achieve satisfactory disinfection, a good quality disinfectant is required. An ideal disinfectant should have a high inactivating capacity for a wide range of viruses, such as HIV and hepatitis, as well as being effective against bacteria, including tuberculosis. It should be safe to use and suitable
for frequent application. Disinfectants are typically supplied as pre-saturated wipes which may be alcohol-based or non-alcohol based. This article considers the key requirements for a surface disinfectant and examines the comparative advantages of alcohol and non-alcohol wipes.
Disinfection and hygiene
It is the responsibility of everyone working in the practice to ensure that
surfaces are clean and disinfected. The process of wiping down surfaces between patients should be an integral part of good practice. The General
Dental Council (GDC) recognises the importance of disinfection by making it a compulsory subject for continuing professional development (CPD) for dentists and dental care professionals (DCPs).
Disinfection is the process of using a chemical with proven antibacterial, anti-virucidal and anti-fungal characteristics to kill or to inactivate microorganisms. International standards are in place to assess disinfectants in relation to their ability to kill set numbers of microorganisms (termed ‘biocide efficiency’), where a population of microorganisms is reduced to a level that should not be harmful to patient health; and to eliminate a wide-range of different types of microorganisms (the spectrum of activity). Standards for disinfection applied to surfaces are distinct from those that apply to the decontamination of dental instruments.
To achieve good disinfection, there is a choice of different formats and
different types of disinfectants. 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 have the added advantage of containing the correct amount of
disinfectant.
In relation to different types of disinfectant, there are two main types available for wiping hard, non-porous surfaces: those that are alcohol based and those which are non-alcohol based, with the latter group generally being types of quaternary ammonium compounds (‘quats’).
Selecting disinfectants
There are a number of factors that need be considered when selecting the most appropriate type of disinfectant for surface cleaning. These are:
Format
The disinfectant should be in a userfriendly format, ideally in the form of a wipe. Wipes avoid the need to mix and prepare solutions. They also require less stringent health and safety measures to be adopted (the main requirement is for the user to wear gloves).
Safety
It is important that the disinfectants are safe for staff to use, are compatible with the surfaces to which they are applied (in that they do not cause pitting or rusting), and that they can easily be disposed of without harming the environment.
Spectrum of activity
When choosing a suitable disinfectant the bactericidal, virucidal and fungicidal
properties should be carefully studied as these are essential requirements for an effective disinfectant. A product which has all these properties will give the best possible spectrum of protection. When deciding between alcohol and
non-alcohol based disinfectants, it is the alcohol based types that have the widest spectrum of activity.
In recent years there has been considerable concern with the bacteria that cause MRSA (certain types of Staphylococcus aureus that are antibiotic resistant) and those that cause tuberculosis (Mycobacterium tuberculosis). With tuberculosis, reports suggest that cases in the UK have increased in the past 15 years and the incidence in the UK is above the European average, together with a parallel increase in multi-drug resistant types of the bacterium.
In cases of tuberculosis, infection occurs through inhalation of the bacterium which then travels to the alveoli of the lungs. Most people who carry the bacterium do not show any symptoms (latent tuberculosis); however, the condition can be serious for people with weak immune systems. Although the disease is rare, dentists need to be aware of the possible occurrence of oral lesions of tuberculosis and consider them in the differential diagnosis of suspicious oral ulcers. However, in many cases symptoms are not apparent, therefore good disinfection practices should be in force in-between patients. One concern is that Mycobacteria have a tough, waxy cell wall that helps to prevent disinfectant entry.
With the two common types of disinfectants used for surface disinfection, quats are generally regarded as ineffective against the tuberculosis bacterium. There is some evidence that tinctures of quats can inhibit the growth of M. tuberculosis, but not kill it. The effectiveness of inhibiting TB bacteria reduces in the presence of protein residues and the bacteria-killing properties of quat-based disinfectants are weakened when the disinfectants are combined with hard water, or materials such as cotton or gauze pads.
In contrast, alcohols are effective against mycobacteria, with 70 per cent alcohol solutions the most effective against these types of microorganisms.
Aside from the hardiest sporeforming bacteria, alcohols possess the widest disinfectant kill ranges of the commercially available disinfectants.
Another important consideration is with viruses. Quat-based disinfectants are generally virucidal against what are termed ‘enveloped’ viruses, such as HIV and hepatitis B. However, these chemicals are not virucidal against the ‘non-enveloped’ viruses, such as poliovirus, rhinoviruses (which cause
the common cold) and hepatitis A. In contrast, alcohol-based disinfectants,
especially those with high ethanol content, can efficiently destroy viruses of all types. One study determined that the optimal virucidal spectrum was with a concentration alcohol mixture (80 per cent ethanol and five per cent isopropanol) for the elimination of all relevant blood-borne viruses.
Ease to of use
The disinfectants used in a busy dental practice must be in a format that can be applied quickly. They must also have a short ‘contact time’. This is the time in which the disinfectant remains in contact with the surface in order to
kill microorganisms. Both quats and alcohols have fairly rapid contact times,
requiring less than one minute contact time.
Importance of cleaning
Surfaces may contain protein residues, such as blood and pus from the patient. It is important that the disinfection process effectively removes any protein present and allows the disinfectant to work. Alcohols can, in some circumstances, bind proteins to stainless steel instruments. However, this effect has only been demonstrated after a prolonged contact time of over 10 minutes – a period of time which is far in excess of the wiping process required to disinfect surfaces in the practice. Very few dental practices have
surfaces that are composed of stainless steel.
In practice alcohols are as effective as quats on surfaces containing protein
residues, when a double-wiping procedure is adopted. The first rub of the surfaces with the alcohol wipe removes the protein. The second rub with an alcohol wipe brings the alcohol disinfectant into contact with any remaining microorganisms, allowing the disinfectant to penetrate through the microbial cell wall and to destroy the microbe by denaturing its cellular proteins.
Conclusion
The dental health-care setting is an environment where disease transmission can easily occur. Prevention of cross infection is therefore a crucial aspect of good dental practice and dental professionals need to adopt effective basic routines. This includes disinfecting surfaces, especially in-between patient visits particularly for the elimination of pathogenic microorganisms, like TB or
MRSA bacteria.
Given the array of different disinfectant types and formats, the article has considered the optimum criteria for a disinfectant. This assessment has concluded that alcohol wipes offer the best solution for staff and patients. While quats may act quickly on heavily soiled surfaces, a double-wipe with a saturated alcohol wipe ensures that a broader range of pathogens, including TB, are removed, thereby offering better protection of the patient from infection and a more hygienic dental practice.
References available on request.