With the holiday season approaching, it’s time to remind ourselves of the possible threats to our homes and cars during this time. In the lead up to what should be a fun and festive time with loved ones, it’s important to think about what you can do to protect your valuable assets during this period.
Thefts and burglaries increase at this time as a lot of crime is opportunistic; thieves know that houses and cars might be full of newly purchased gifts. Thieves also know that with people away on holidays, there is an increased opportunity to break into cars and homes.
However, holiday dangers aren’t just about thefts and burglaries. People also need to think about what they can do to protect their homes and cars from damage or unnecessary costs while on holidays, as well as keeping themselves safe.
Protecting your home
Before heading off on holidays:
• Be mindful of how you dispose of packaging of gifts or newly purchased items. A bin full of boxes for items such as televisions, game consoles or tablets lets people know what valuable items are in the home.
• Ask a friend or neighbour to collect your mail. A build-up of mail is a sure sign someone isn’t home.
• Use a timer to have your house lights turn on and off at certain periods of the day, creating a look of someone being in.
• Consider what appliances can be turned off within your home. While usage is low, many appliances continue to use power even when they aren’t being used. Items to consider turning off include hot water tanks, televisions, microwaves and computers. However, be sure to think about what you’re turning off before you quickly switch off all power; for example, fridges and freezers, unless empty, should be kept on.
• Clear out your gutters. A build-up of leaves and other debris creates a fire hazard as well as a risk of an overflow of water entering the roof space during a storm.
Protecting your car
• If leaving your car at home while on holidays, where possible leave it locked securely in a garage or somewhere else out of sight. Thieves will notice a car sitting in the sam spot every day which hasn’t moved.
• Don’t keep valuables in sight that could entice those opportunistic
thieves. This applies to items used all year, such as mobile phones. However, over the holiday season it also applies to shopping bags which are clearly full of new items.
• When taking your car on holidays, be sure you have some sort of roadside assistance or breakdown coverage to protect you during those
unexpected moments.
• If sharing driving duties during a road trip, be sure the insurance policy for the car covers all drivers.
• Take regular breaks on long drives by either swapping drivers or taking rest breaks. Also, when on long drives, plan your stops to allow for petrol fill ups and food and drink stops.
• Be particularly careful when driving at dawn and dusk as visibility generally isn’t as clear as during the day.
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Various forms of water are used in the dental practice. The previous article, ‘Dental unit waterlines’, focussed on waterline biofilm issues. In this second article, Professor Laurence Walsh summarises key aspects of water quality that impact on instrument reprocessing and sterilisation.
WATER FOR ULTRASONIC CLEANERS
Tap water has dissolved oxygen and other atmospheric gases. Aerators on taps slow the flow to reduce splash, but they increase the dissolved gases. Degassing of water is essential to remove dissolved gases before undertaking ultrasonic cleaning of items.
WATER FOR CLEANING ITEMS AND FOR RINSING INSTRUMENTS
Water used in instrument cleaning should have low levels of viable bacteria and bacterial products such as endotoxin, and be free of heavy metals and other contaminants. A key property of water that is used with detergents is its hardness. In hard water, there are high levels of calcium and magnesium salts, particularly carbonates, bicarbonates, sulphates and chlorides. This causes faster build-up of limescale, which can foul plumbing in the water distribution system, as well as major problems with detergents, such as low foam height and reduced surfactancy. The reason for this is that calcium or magnesium ions form insoluble salts with detergents, reducing their surfactant effects. Instead, they create a coating of insoluble stearates on the surface of instruments. This is equivalent to ‘soap scum’ seen in a shower recess.
Water softening creates soft water by replacing the calcium and magnesium ions in the water with sodium or potassium ions, so that no insoluble products are created by the reactions with detergents. Typically, water softening uses an ion-exchange resin. When all the available sodium or potassium ions in the resin have been replaced with calcium or magnesium ions, the resin must be re-charged by eluting the bound calcium and magnesium ions off the resin using a very strong solution of domestic salt (sodium chloride).
The hardness of ground water varies considerably around Australia, and water hardness problems are often encountered. This is why some detergents used for instrument cleaning include chelating agents such as citric acid or EDTA, which act as softening agents.
IS RAIN WATER SUITABLE FOR INSTRUMENT CLEANING OR FOR FEEDING STERILISERS?
In short, the answer is no. Normally, rainwater collected into polyethylene tanks is soft as it has low levels of calcium and magnesium ions and so forms a strong lather with detergents. Rainwater stored in concrete-lined tanks becomes hard due to dissolved calcium hydroxide that has been released from Portland cement into the water. Overall, rainwater is not well suited for use in a sterilising room. It is neither sterile nor is it free of anions and cations. Rainwater picks up multiple contaminants from the atmosphere (dust, pollutant gases) and from where it has been collected (off a roof). Normally, rainwater is acidic due to the presence of dissolved carbon dioxide (carbonic acid) as well as containing traces of sulphuric acid and nitric acid, both of which are derived from natural atmospheric sources and from industrial activity
WATER FOR STEAM GENERATION
Demineralised water is used for steam generation in steam sterilisers. Tap water is not suitable because this contains many cations (calcium, magnesium, aluminium, sodium, potassium, iron, and copper ions) and anions (phosphates, carbonates, sulphates, silicates, chlorides, fluorides). Precipitation reactions will cause scale build-up on water heating elements in steam sterilisers, in the same manner as occurs in water distillers, kettles, clothes irons and steam cleaners. In water distillers, regular removal of this white or yellowish mineral scale left on the heating elements of the distiller must be undertaken with an appropriate agent such as citric acid or dilute sulphuric acid.
Water may be demineralised, i.e. rendered free of cations and anions, by one of three different processes – distillation, ion exchange in a deioniser resin, and reverse osmosis (RO). While these processes remove ions, they do not remove uncharged materials including organic compounds and microorganisms. Deionised, distilled and RO water are not sterile.
When water is boiled the condensate is collected, resulting in distilled water free of inorganic minerals, and so is suitable for use in a steam steriliser. Distilled water does not have a neutral pH (7.0), but rather tends to have a low pH, caused by carbon dioxide from the atmosphere dissolving back into the water, forming a dilute solution of carbonic acid. When distilled water is made, the collection container is normally not sterile and so distilled water almost always contains some viable bacteria. To avoid this, additional treatment (such as ozonation or short wavelength ultraviolet light treatment) would be needed. The same holds true for deionised and reverse osmosis water; as with distilled water these are not sterile.
Many dental practices use water deioniser cartridges to generate water for use in a steam steriliser, as the process is easier, less expensive and more energy efficient than distillation or reverse osmosis. In a water deioniser unit, an ion-exchange resin exchanges dissolved cations and anions for hydrogen ions and hydroxide ions. A water deioniser does not remove uncharged organic molecules or bacteria, except by incidental trapping in the resin. As mentioned above for water softening resins, the ion exchange resin beds in a water deioniser unit have a limited capacity and need to be regenerated or replaced periodically. In many cases, this is on a regular schedule (e.g. three monthly) based on the water flow through the cartridge. Often deioniser cartridges are fed by sediment and carbon filters, and will have their own replacement sequence. It is essential to follow the supplier’s advice on when the different cartridges in a multi-cartridge system should be changed. Commercial test strips and meters to check water quality are readily available for monitoring ion content.
The process of RO uses high pressure to force water through a semipermeable membrane to remove ions, molecules, and larger particles including some bacteria. Tap water pressures of around 40 psi can drive a small RO unit. An RO system must have pre-treatment filters to stop membranes clogging. As with water deionisers, RO filter cartridges need to be changed on a regular basis as per the supplier’s instructions. RO water tends to have a neutral pH, but can be too soft and thus corrosive to pipes and control blocks which is why RO water is not approved for use in many types of dental chairs. Similar issues can occur when using distilled or deionised water, since these are mineral-free and can be very aggressive in reacting with some types of dental unit control blocks.
An additional issue with an RO system fed from mains pressure water is that they tend to have low recovery (5-15%) and so will use a lot of water that will be discharged as waste water into the drains. Surprisingly, this can lead to high water usage bills.
To achieve sterility, the steam in a steriliser must condense to transfer the latent heat of condensation onto the instruments or items. This raises an important problem when the water for steam generation is condensed and then re-used in later cycles, rather than being dumped. In re-used water, contaminants (such as handpiece lubricants) build up progressively over time, leading to problems with superheated steam that is too dry and will not condense. For steam sterilisers that condense and re-use water in multiple cycles, demineralised water must be completely replaced every week, and not just topped up.
Disclaimer
Insurance issued by Guild Insurance Limited ABN 55 004 538 863, AFS License No. 233791 and subject to terms, conditions and exclusions. This article contains information of a general nature only, and is not intended to constitute the provision of legal advice. Republished from the ADA News Bulletin, December 2017 No 471 and February 2018 No 472 with the kind permission of the Australian Dental Association. Guild Insurance supports ADA through the payment of referral fees. Please refer to the policy wording and policy schedule for details. For more information call 1800 810 213.
This first article, in a two-part series on water quality in dental practice by Professor Laurence Walsh on behalf of the Infection Control Subcommittee, provides useful guidance for all practitioners managing water quality in their practices.
The second part is published under the article ‘Water quality in dental practice – Understanding water quality’.
Biofilms within dental unit waterlines (DUWL) have been linked to respiratory infections and wound infections, involving pathogens such as Pseudomonas aeruginosa, Legionella pneumophila and nontuberculous mycobacteria. These bacteria are widespread in natural sources of freshwater and are found commonly in manmade water systems. If tap water with no additional chemical additives is fed into a dental chair through a mains water connection or via a bottle, there will be rapid development of biofilm in the waterlines. Even with chemical treatments, growth of biofilms will occur more rapidly when there is stagnation (from periods of non-use such as weekends and holidays), and when the ambient temperature is higher.
Dental units connected directly to mains water must have backflow prevention devices, such as reduced pressure zone (RPZ) valves, to prevent water from the dental practice running back into the reticulated water system.
Many dental chairs now use self-contained bottled water systems, with the bottle located internally or externally. It is essential to check the dental chair manufacturer’s instructions regarding the correct water type and the appropriate chemical additives. When a water bottle contains a continuously acting antimicrobial agent (e.g. silver, iodine, chloramine), the bottle can be left on the chair overnight. However, if any visual contamination is present, the bottle must be removed for thorough washing.
For dental chairs that use short acting antimicrobial agents (e.g. ozone, hydrogen peroxide), the manufacturer may advise removing the water bottle at the end of the day, then flushing the lines with water, purging them with compressed air, and keeping the bottle stored inverted and dry on the bench overnight. As before, if visual contamination is present, remove the bottle for thorough washing.
Regardless of the system used for biofilm control, ADA recommends flushing all waterlines at the start of the working day for two minutes (with no handpieces attached).
A range of chemical agents are available for biofilm prevention and control, including hypochlorites, chloramine T, peroxides, ozonation, silver and iodine. Systems for delivering these agents include external dosing, internal dosing, tablets, liquid dosing, and slow release collection straws. If using tablets, remember that it is necessary to wait two minutes for the tablets to fully dissolve before using the dental unit.
There are special products made for long term ‘mothballing’ of low use dental units, to prevent biofilm growth over several months. These are left sitting in the waterlines, and are flushed out before the chair is brought back into service.
MICROBIAL MONITORING
Commercial tests can be used to assess bacterial levels in water coming from DUWL. These measure the levels of heterotrophic microorganisms using a nutrient agar. A typical test involves incubation at room temperature for 3-5 days, after which colonies are counted. Ideally, there should also be a second sample incubated at body temperature for two days. However, this requires an appropriate incubator.
The objective is to keep bacterial numbers as low as possible. The ADA recommended threshold is no more than 500 colony forming units per mL (CFU/mL) for non-surgical dental procedures since this is a widely used international limit for safe drinking water. When treating medically compromised patients, it is recommended that the water from the dental unit waterlines contain less than 200 CFU/mL. The specimen container used to collect the water sample must be sterile. If there is chlorine present, a small amount of sodium thiosulfate (X-ray film fixer) should be added to the sample to neutralise any residual chlorine.
Frequency of water testing depends on the test results. A starting point would be to assess exit water from a dental chair as a baseline. If results are below 200 CFU/mL, then re-test after three months, and if they remain low, then extend that to every three or six months. With a new dental chair installation, it is advisable to test exit water quality on installation, then three months later. Annual testing would be a workable recommendation for dental chairs in most clinics that are using chemical treatment agents routinely, on the proviso that any indications of water that is turbid or cloudy entering or leaving the dental unit should trigger further testing.
If test results indicate a bacteria level greater than 200 CFU/mL, then undertake a shock treatment to reduce bacterial contamination from the waterlines in that dental chair. Whenever applying a shock treatment, be sure to adhere to the product instructions provided by the manufacturer, as well as the instructions for the dental chair, since not all shock treatment products are compatible with all brands of dental chair. For example, only some control blocks can withstand sodium hypochlorite shock treatment without suffering corrosion. After a shock treatment, flush the agent out and continue normal chemical treatments, then re-test levels of microorganisms. Some types of additives to water bottles come with recommendations for regular dental unit water monitoring and shock treatment.
Disclaimer
Insurance issued by Guild Insurance Limited ABN 55 004 538 863, AFS License No. 233791 and subject to terms, conditions and exclusions. This article contains information of a general nature only, and is not intended to constitute the provision of legal advice. Republished from the ADA News Bulletin, December 2017 No 471 and February 2018 No 472 with the kind permission of the Australian Dental Association. Guild Insurance supports ADA through the payment of referral fees. Please refer to the policy wording and policy schedule for details. For more information call 1800 810 213.