Members of the dental team have a duty to ensure that infection control procedures are followed routinely. The mouth carries a large number of potentially infective microorganisms; saliva and blood are known vectors of infection. vCJD and related conditions raise new infection control questions: ‘prions’ the infectious agents that cause them are much more difficult to destroy than conventional microorganisms, so optimal decontamination standards need to be observed.
All instruments contaminated with oral and other body fluids must be thoroughly cleaned and sterilised after use. The decontamination process, also known as reprocessing includes pre-sterilisation cleaning, disinfection, inspection, sterilisation and storage.
All instruments must be thoroughly cleaned before autoclaving to remove as much matter as possible. Instruments cleaned as soon as possible after use may be more easily cleaned than those left for a number of hours before reprocessing. Blood, saline and iodine are corrosive to stainless steel instruments and will cause pitting and then rusting if remaining on instruments for any length of time. Dental materials, especially cements can harden on instruments so should be removed from instruments as soon as possible after use to allow effective cleaning.
Any debris or organic material remaining on an instrument may shield microorganisms from the effects of steam produced by an autoclave during sterilisation. It is also essential to reduce the number of microorganisms remaining on the surface of the instrument to decrease the likelihood of any microorganisms surviving the sterilisation process.
However, in a busy dental practice it is not always possible or practical to immediately clean, transport and sterilise instruments straight after every use. HTM 01-05 recommends that where a delay is anticipated instruments should be kept moist by immersion in water or an enzymatic cleaner or foam spray to maintain a moist or humid environment.
Research using an OPA/NAC fluorescence-based digital image capture system has demonstrated a five-order of magnitude improvement in protein removal when surgical instruments are kept in a moist environment, compared with test instruments allowed to dry after use. Prions are hydrophobic proteins and the attachment of hydrophobic proteins to surfaces becomes less reversible if they are allowed to dry fully onto a surface. Keeping the environment around soiled instruments at or near saturation humidities (moist) prevents the full attachment of hydrophobic proteins so they are more efficiently removed by cleaning.
ProReveal Study
A study was designed to assess the impact of applying an enzymatic spray to soiled dental instruments in terms of the effects on the protein burden.
Commonly used reusable stainless steel dental instruments were soiled in laboratory conditions using Edinburgh Soil, which simulates the organic material likely to be encountered during dental practice. The soiled instruments were sprayed with an enzymatic foam and left for five minutes. Using the highly sensitive ProReveal system, protein residues were measured at three points: when the ‘clean’ dental instrument was removed from the packet, after soiling and after the five minute application of the enzymatic foam.
The researchers noted that protein was detected on the ‘clean’ instruments, which had not been previously used, highlighting the need to reprocess all dental instruments.
Each instrument was artificially contaminated with the Edinburgh soil. Half the instruments were left to dry and the total protein present was measured. The remaining instruments were contaminated and then sprayed with enzymatic foam (totally covering the instrument), after five minutes contact time the instruments were rinsed using potable water. For both sets of instruments, an average protein loading was obtained.
The results demonstrate a significant reduction in protein removal using the enzymatic foam prior to cleaning.
The ProReveal system has been developed to provide a simple, high sensitivity in-situ system. The test utilises an OPA/NAC spray (o-phthaldialdehyde/Nacetyl cysteine) which is misted over a surgical instrument. In the presence of protein, the spray reacts to emit fluorescence detected under UV light in a viewer. The viewer
automatically shows an image of contaminating proteins in situ on the instrument and measures the amount of residual fluorescent proteins.
Conclusion
Although it is recognised that contaminated dental instruments should be cleaned immediately after use to remove soil before it can dry and harden, in a busy surgery this is not always practical. It may be several hours or longer before reprocessing can take place. Spray on solutions designed to break down blood soil and protein, as well as delay drying of organic soils help keep instruments moist and therefore facilitate more effective cleaning and sterilisation. A new study using the ProReveal system has demonstrated a significant reduction in the protein burden on stainless steel instruments sprayed with an enzymatic foam designed to keep instruments moist prior to transportation and cleaning.
References available on request.