There are many criteria that need to be considered and reviewed before practices start treating patients again, and guidance must be given from a UK regulatory body. Here, are some of the considerations that might need to be reviewed.
SARS Cov-2 causes the disease known as COVID-19 (C-19), a virus that first become known to the world towards the end of 2019. Dental professionals carry a high risk of contracting C-19¹, due to the nature of procedures carried out, particularly face-to-face communication with patients, frequent exposure to saliva, blood, and other bodily fluids, and the handling of sharp instruments.
Airborne Spread
Airborne spread of viruses is well documented. When high-speed dental handpieces work in the oral cavity they produce water, which becomes mixed with patients’ saliva and even blood during treatment. To give some perspective to the new risk dental professionals face, the number of viruses in a patient with Hepatitis C is 2,000/ml of saliva²; the number of viruses with a C-19 patient is 158,000/ml of saliva³. That’s almost 80 times more! The highest values in C-19 patients occur approximately one week after the first symptoms. As some people experience very mild symptoms, they may not even be aware they’re carrying the disease.
Aerosol created from dental procedures can stay airborne for long periods before it settles on a surface or enters a respiratory tract. It can be detected in ambient air for up to 30 minutes⁴. Precipitation of the contaminated aerosol cloud is possible over a radius of several metres. Door handles, light switches etc. can all become contaminated⁵.
Two studies⁴⁺² examining the theoretical infection rates with tuberculosis and hepatitis C outlined the risk. As the level of coronaviruses in saliva is so much higher than either of these two conditions, infection via aerosols seems probable. According to one study⁴, during a 15-minute treatment without protective measures, between 0.014 μl – 0.12 μl of saliva is inhaled via the aerosol. Mathematically, this is equivalent to 2-20 coronaviruses per treatment.
Contact spread
Another route to spreading the disease is through contact. A dental professional’s frequent direct or indirect contact with human fluids, patient materials, and contaminated dental instruments or environmental surfaces can cause the virus to spread. Effective infection control strategies are needed to prevent the spread of C-19 through these contact routines.
Contaminated surfaces spread
The other concern with coronaviruses is the length of time they can live on surfaces such as metal, glass or plastic, all of which are commonplace within dental surgeries. These surfaces then become a potential source of coronavirus transmission. It is essential that dental practices maintain a clean and dry environment to help decrease the persistence of C-19.
Infection Control
Dental professionals are very familiar with infection control protocols. So what extra measures might you want to introduce to prevent the transmission of Covid-19?
There are many criteria that need to be considered and reviewed before practices start treating patients again, and guidance must be given from a UK regulatory body. These may include screening patients to identify risk, hand hygiene, PPE, use of rubber dam isolation, review of the practice’s disinfection measures (both in the surgery and public areas) as well as the management of medical waste.
Controlling Aerosol
For the purpose of this article, we are going to review the part played by the suction unit.
Suction with a powerful spray mist suction system is the only way to reduce aerosol⁶. Only a spray mist suction system with a suction volume of approximate 300 l/min is able to reduce aerosol⁷. You should also always work with a large suction tip. A saliva ejector or a suction tip with a small diameter reduces the suction volume. Four-handed dentistry is essential, as the dental nurse will need to focus on suction technique. It is advisable that a rubber dam is also used.
Suction Power
You must also inspect your suction system. Check that the power of your unit is at least 250-300 l/min per treatment room. You should also consider whether the demands on your suction power have changed. Have you expanded your practice, for example? It may well be that the unit you had prior to refurbishing your practice is not now sufficient for your extended facility. The power of your suction unit should only be checked by a trained service technician, using a measuring device.
Suction ‘Reflux’
It is advisable to also use a suction tip that has a secondary air inlet as this will ensure the suction flow is maintained even if the tip becomes clogged. Back in 2005, a potential transmission route for hepatitis via a ‘reflux’ from the suction handpiece and the suction hose⁸ was reported. The risk of microbial contamination of a suction handpiece has also been highlighted⁹. The suction tip and handpiece should therefore be sterilized after every patient.
Viricidal Disinfection
You need to ensure that you’re disinfecting both the handpiece and all potentially contaminated surfaces with a suitable disinfectant in between appointments. A disinfecting agent with, at the very least, a limited viricidal spectrum of efficiency, is required as a minimum to deactivate C-19.
Air Filters
It is also recommended that the practice install an exhaust air filter. Only a small number of suction systems are currently equipped with bacteria filters, this is why you should protect yourself and others by not directing unfiltered suction system exhaust air outside the building. All Durr suction systems can have bacterial filters fitted, which should be changed every 1-2 years (depending on the model) along with compressor filters. The suction motor should be exhausted away from the compressor.
Nothing could have prepared us for the horror of C-19. Its rate of contagion shocked the world. Certainly, the world to which we’ll return is going to be very different; the changes will impact us both professionally and personally.
Ian Pope, Managing Director of Durr Dental UK
References
- Peng et al 2020.
- Xavier et al (2015)
- Kai-WangToet al (2020)
- Driskoet al (2000), Bennet et al (2000)
- Graetzet al (2014)
- Tillner (2016)
- Barnes et al (1998),Harrel et al (1998), Reitmeirer et al 2010)
- Mielkeet al (2005)
- Coleman et al (2010)
Full references available upon request
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