Martyn Young - Dental Laboratory Technician, demonstrates the properties of Anutex modelling wax sheets and bite blocks in the preparation of a trial set up
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 article. 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.
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.
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 is now retired having been a qualified and registered Dental Nurse for 38 years mainly spent in various guises at Birmingham Dental Hospital. Her title was – Senior Dental Nurse (Decontamination). She was a member of the editorial board of the “Dental Nursing” Journal and also wrote articles for them. She has had a book, entitled “The Dental Nurses Guide to Infection Control and Decontamination”, published in the spring of 2008. Kathy Porter cannot endorse any of the products advertised in this article.
Richard Clegg RDT, 1st Dental Sheffield, highlights the advantages of providing your clients with top quality Private Occlusal Rims.
In these difficult times many Technicians and Laboratories are looking to increase their profitability by increasing their efficiency and producing more Private work at the expense of their less valuable NHS work. The latter can be achieved by either encouraging their existing clients to do more Private work or, probably more realistically, expanding their customer base by targeting new clients who are more interested in delivering Private work to their patients. Either way the quality of the work the Technician needs to deliver to the Dentist needs to be of a demonstrably higher standard. This can also offer other advantages to both the Dentist and Technician because it can increase their efficiency by saving both of them a significant amount of surgery and lab time, reducing the number of re-tries required and achieve a greater sense of value for money and overall satisfaction for their clients, the patient and Dentist respectively.
Ideal prescription for a set of Private Occlusal Rims
If you provide Dentists with correctly shaped Occlusal Rims it will make it quicker and easier for them to select the correct mould of teeth and ensure that the function and phonetics of the final dentures will be correct.
Rather than simply building my Private Occlusal Rims on a shellac or wax base I use a self curing or light curing acrylic base for both the upper and lower wax block. In the upper I remove the acrylic from around the area of the rugae and incisive papilla and fill this space with wax. Similarly I remove the acrylic from any areas where there are deep labial undercuts and block them out with wax to ensure that it is possible to remove the finished Occlusal Rims off the models afterwards.
Once these acrylic bases have been laid down and waxed up over the rugae etc I add a pre-curved wax bite rim block. The wax bite rim blocks I use have already been preshaped to have the optimum dimensions for the majority of “normal” patients. In the posterior region they are 10mm x 10mm in cross section which is just about the optimum size. Using preformed blocks saves time and also prevents the risk of porosity which may occur when sheets of wax are hand-rolled.
I position them so that the labial border is in the optimum position for the anticipated amount of labial support I expect the Dentist will want to achieve.
The wax rims should be placed where the natural teeth used to be. This needs to take into account that the maxilla atrophies inwards (centripetally), but the mandible atrophies outwards posteriorly (centifrugally) and inwards anteriorly. Therefore, in the posterior area of the upper Occlusal Rim the wax rim should be placed buccal to the ridge centre, and in the lower on or just lingual to the ridge centre.
In the lower jaw the wax rim runs on a plane from the incisal edge to the middle of the retromolar triangle. This forms the occlusal plane in the mandible, which is parallel to the model base and corresponds to Camper’s line.
I then complete the waxing up using more wax. The peripheral margins of each rim should be positioned approximately 5mm short of the mucolabial (muco-buccal) and, in the lower, lingual folds. They should also cover the maxillary tuberosities and retromolar areas. The muscle attachments must remain free.
Then I thin out the wax rims to about 6mm wide on the palatal and lingual surfaces starting at about the premolar/canine area. This produces a lingual space for the tongue so that the patient’s phonetics will be optimised. By thinning them out in this way I can save my clients a significant amount of surgery time and reduce the amount of re-tries we all have to endure.
After they have been finished and polished, they are delivered to my clients in a padded box to avoid any risk of damage. This presentation also creates the appropriate finesse for Private work as far as the patient is concerned. I consider it money well spent.
The Dentist is then responsible for modifying the amount for labial support required for individual patients, by extending or reducing the amount I’ve provided. However there is normally only a minimal amount of adjustment required, so again there is a significant time saving for the Dentist and patient.
The Dentist is also responsible for adjusting the Occlusal Rims so that the patient can achieve the correct “f”, “s” and “t” sounds. These are determined by obtaining the correct vertical height and tongue position at the canine/premolar area. For example, during “f” sounds the maxillary incisors should lightly touch the lower lips between the wet and dry area of the lips.
In my opinion, the maximum a patient’s vertical dimension can be increased at any one time in full edentulous cases is by about 4mm. Anything greater than this simply cannot be tolerated by the vast majority of patients and simply means they would be unable to successfully wear the dentures, no matter how much time and effort are put into them by the Dentist and Technician. The “average” vertical height for most patients is normally about 40mm in total, with the occlusal plane of the lower teeth set just below the level of the tongue in order to allow an appropriate amount of Free Way Space. The correct vertical height is measured using a Willis Bite Gauge. This means that for optimum aesthetic and occlusal results the trimmed Occlusal Rims will normally end up about 21mm high in the maxilla and 19mm high in the mandible. Therefore I produce my Occlusal Rims about 22mm high each. This normally provides more than enough additional height for the Dentist to adjust their heights in order to record the correct occlusion, but not so much that a lot of unnecessary time is wasted trimming them down. Again this saves both the Dentist and patient valuable surgery time.
After the Dentist has finished recording the appropriate centric registration the Occlusal Rims should indicate the exact position of the artificial teeth in the denture set-up. They should be shaped so that in both jaws their labial surfaces are positioned directly over the vestibule. They should be hollowed out lingually so that the tongue has adequate space for correct phonetics and masticatory function.
The bite stage is one of the most important stages in the fabrication of any removable or fixed prosthetic, so great emphasis on communication between the dental team and patient is very important and should be observed. The most common problems that arise in a poor bite registration are the lack of detailed information given to Technicians on such things as the patient’s psychological attitude towards having treatment. Some patients can be very nervous which can cause problems when chair time is short. There are other physiological and pathological notations that should be communicated to the Technician as master models do not always show clearly the condition of the soft tissue present i.e. hyperplasia and flabby fibrous ridges.
The denture plate extension posteriorly needs to be extended fully, but if the patient has a sensitive gag-reflex this also needs investigating and marking on the primary model or secondary impression. The importance of each structure found within the oral cavity is learnt at a very early stage in dental anatomy, but the Palatine Fovia is key to establishing the junction between the hard and soft palate, and location of the vibrating line. Thus the proper distal extension of the denture base plate can be established. This information isn’t always clearly visible on the working model so it is good practice to have this identified at the surgery.
It should be understood that a bite registration appointment should take a minimum of one hour to complete; this surgery time should be incorporated into the treatment plan with the possibility to extend it if needed.
When fabricating my Private Occlusal Rims I particularly like using Kemdent wax products, which I purchase via Skillbond Direct, because they have a composition rigid enough to withstand heat when they are being formed, but do not distort when placed in the mouth during the Occlusal Registration itself. This rigid composition, allied to the fact that they are “sticky enough” to bond to artificial teeth during the set up stage, also means that I can set up the teeth in the Occlusal Rims themselves after the Occlusal Registration has been correctly recorded by the Dentist. This makes achieving the correct aesthetic and functional performance of the final prostheses easier and ultimately saves time. I find some other waxes are too rigid so that the teeth do not stick to them sufficiently well, running the risk of the teeth moving or even falling out during the try-in stage etc.
There are some real benefits to using Kemdent’s new PumiceSafe Universal Cleaner
Because there are no specific EU Regulations regarding disinfection within Laboratories, the DLA, in association with the BDA and BDIA, have developed their own series of Fact Sheets designed to enable Laboratories to implement Best Practice for the control of cross infection within the Laboratory.
These Fact Sheets cover various aspects of cross infection control, including the Laboratories responsibilities in a variety of situations, including performing repairs for the General Public and acting as CDTs.
Within these recommendations they highlight the potential risk of cross infection associated with denture repairs and the use of contaminated pumice slurry between one patient’s prosthesis and another’s.
Within production areas, the DLA Fact Sheet CI01 states that “all work benches, sinks and model trimmers benefit from being wiped down daily with a disinfection solution” and that “as far as practical the Laboratory should be kept as clean as possible”. However, due to the nature of the production work, nobody would be expected to maintain a spotlessly clean working environment. However, there is “no excuse for not cleaning up on a daily basis and in particular making sure dust is removed by vacuuming and wiping down the benches”
With regard to pumice, the DLA Fact Sheet states that “it has been shown that bacteria can survive in dental pumice for extended periods of time.
In a dental laboratory where the polishing lathe is constantly used, it is important that the items polished are free of bacteria when brought into the area. This is particularly important when dealing with items like repairs. If the repaired prosthesis has not been disinfected it may transfer bacteria into the pumice which will then be used on new appliances.
If items are then shipped back to the surgery still contaminated with this pumice it is possible that when the patient is fitted with the appliance, they will be at risk of becoming infected by the bacteria present in the contaminated pumice.
It is therefore important to change the pumice on a regular basis and disinfect the pan holding the pumice before putting fresh pumice into it.
It is strongly advised that the same pumice is not used for new work and repair work. When working on repairs, it is recommended that a small fresh amount of pumice is dispensed and used.
As pumice always produces a contaminated splatter and aerosol, a liquid disinfectant should be used as the mixing medium in pumice.”
“Always wear a dust/mist-type facemask and eye protection when operating a model trimmer, brush trimmer or rag wheel with pumice.
Rag wheels and brushes should be soaked for ten minutes after use and left to dry overnight.”
As well as advising on pumice, Fact Sheet CI01 also highlights the importance of cleaning work surfaces with an appropriate disinfectant, especially if the Laboratory does not have sufficient space for separate benches for processing incoming and outgoing work.
As a bare minimum all work benches should be wiped down with a suitable disinfectant at the beginning and end of each workday.
Finally the Fact Sheet states “If a Laboratory chooses to provide dentures direct to the public it is essential that a high standard of infection controlled should be practised at all times.” In these circumstances it is the CDT who has taken on the legal responsibility for infection control normally undertaken by the Dentist.
What does this mean for pumice?
First and foremost, the DLA Guidelines say that Laboratories should use a disinfectant solution, not just water, to make up their pumice slurries.
Because, unless it is discarded every day, in a warm Laboratory environment a water-based pumice slurry can quickly start to smell and often even develops a mouldy surface, which is unpleasant to deal with and has to be removed before the underlying pumice can be used.
What causes this mould?
If the pumice is not regularly discarded it quickly becomes impregnated with microorganism-laden stagnant water, which starts to smell and develop a surface mould of algae. This problem can be exacerbated where denture repairs are concerned, because the worn dentures are often plastered (sic) in bacteria and other microorganisms from the patient’s mouth, unless the very strictest disinfection protocols have been employed. Even then this can be extremely difficult to achieve with 100% success due to the presence of interstitial bacteria etc. Though this risk can be reduced slightly by having two pumice sources, one for new dentures and one for repairs.
Even if Technicians wear face masks, whilst using their pumice slurry, they are still being exposed to the microorganism-laden pumice spray which is neither pleasant nor healthy.
Another potential source of cross infection are the lathe brushes used as part of the polishing process. These are rarely, if ever, disinfected normally, but if soaked in a suitable disinfectant they can be disinfected easily without causing any damage to them. In addition, this will dramatically reduce the risk of burning the acrylic associated with the use of dry lathe brushes.
What is the answer?
If the pumice is not regularly discarded it quickly becomes impregnated with microorganism-laden stagnant water, which starts to smell and develop a surface mould of algae.
Kemdent have introduced PumiceSafe, which is specifically designed to prevent the development of the mould in pumice slurry as well as offering other benefits.
PumiceSafe is an alcohol-free, water-based cleaning solution which can be used in place of the ordinary tap water most Laboratories currently use to make their pumice slurries. It can also be used as work surface cleaner.
Supplied ready-to-use, so there is no need to dilute any concentrated solution, it can simply be dispensed, a few drops at a time, as and when required. Non-foamy, it is used to produce a pleasant smelling microorganism-free pumice slurry and also helps reduce the presence of dust within the Laboratory environment.
Non-greasy or slimy it is ideal for use with a cloth as a surface cleaner too, where it will help maintain a clean and dust-free environment easily removing light to moderate dirt and other surface debris. PumiceSafe can also be used as a soak for lathe brushes to remove pumice debris. Here it also softens the lathe brushes and as the soak becomes contaminated with debris it changes colour, from pale blue to dark green, providing a clear visible indicator that it is time to change the soak.
Alcohol-free, so that it does not dry out or irritate the Technician’s skin during frequent contact, other benefits associated with PumiceSafe are its pleasant minty fragrance, which helps generate a more pleasant working environment, and its glycerine and emollient content, which help keep the Technician’s hands softer and helps prevent them drying out due to contact with the various irritant chemicals and powders routinely found within Prosthetic Laboratories.
PumiceSafe is supplied in 5 litre refill containers and 500ml spray units for surface applications.
Competitively priced, using PumiceSafe enables Laboratories to use the same pumice for longer before it starts to smell and look unsightly. Consequently it saves time and money compared with traditional pumice/water slurry, which needs replacing at least weekly, if not daily, in heavy duty or warm weather use.
Not only is PumiceSafe nicer to use, but it saves Laboratories money too!
For more information about PumiceSafe Universal Cleaner Click Here