Coronavirus – A Dentist’s Simple Guide v3

Coronavirus – A Dentist’s Simple Guide

The following is a personal view. The situation is changing VERY rapidly, and the information may be out of date by the time you read this.

I have updated this as it now a month since my first summary of the situation; and some comments and thoughts on how UK dentistry has reacted.
This is a personal view and as the situation is still changing rapidly, and may be out of date by the time you read this.

– Prof. Ross Hobson

Who am I?

My background is as a dental academic for over 20 years and prior to that a basic scientist, so I am welded to the scientific evidence and not the ‘ask the audience’ of social media. Hence, I am an inbred cynic who believes in data and it’s analysis. I have spent many a happy hour reading and cross-referencing the media and published research. I must acknowledge Dominic O’Hooley who has read even more than I and I thank him for bringing much new information to my attention

Coronavirus – What is it? 

The correct name is SARs-Cov-2 or COVID-19. It is an RNA virus fairly common in animals, causing upper respiratory tract infections.  Due to circumstances in China in late 2019 it mutated and ‘jumped’ from animal to human – this jump between species is fairly uncommon.  COVID is related to the SARS and MERS viruses and epidemics in 2003 (SARS) and 2012 (MERS).
It has been confirmed this is an evolutionary mutation from bats via pangolins to human thought to have occurred in a ‘wet’ (live animal) market in Wuhan, China in late 2020. It is not some virus experiment that has escaped from a laboratory.

The virus targets the ACE2 receptor on human cells, a receptor in blood pressure regulation and is closely related to the SARS virus and hence the respiratory disease it causes and is very contagious with a R0 of about  5.7  ie each infected individual infects 5.7 others. In the UK social distancing/self-isolation and hygiene has reduced the R0 to 0.6-0.7

R0 number is a measure of the infectivity of a disease when everyone in a population is vulnerable: it is a new disease; no one has been vaccinated; there is no means to control the spread of the disease.

The 2018 ‘Spanish flu’ had an R0 of between 1.4 and 2.8, for comparison the R0 numbers for a few ‘well-known disease are below

Disease R0
Hepatitis C 2
Ebola 2
Mumps 10
Measles 18

RNA viruses mutate at much higher rates than the host, so there is a possibility the virus could mutate into a more dangerous virus with increased morbidity (death), but the majority mutations tend to cause the mutation to become extinct.

The link between ACE receptors has become linked with Ibuprofen, which is said to worsen the COVID symptoms. This has resulted in some outlandish Social Media claims that Ibuprofen and Corona Virus has caused deaths in teenagers!  The scientific indicated there is no strong evidence to support this claim. However, to be safe it is recommended that paracetamol is used to manage Corona Virus symptoms.  If you are using NSAIDs if prescribed by your doctor you should not stop them without medical advice

How is it spread? and How do I protect myself?

Corona Virus is similar to SARS and is spread by aerosols and droplets caused by coughing or sneezing by direct inhalation or surface contact, the same modes as influenza.  Surface contact is probably the greater means of person to person transmission.
Hence, the advice for 2m social distancing, regular washing of hands and not touching nose/face.

Under ideal conditions aerosols from coughing/sneezing can travel up to 7m and COVID virus remains viable for up to 2 hours in aerosol, and up to 72 hours on hard surfaces
There is evidence that faeces can harbour the virus for long periods of time after the infection has subsided. This becomes a problem with poor hand hygiene.


Much has been made of medical aerosol and comparisons made with dental generated aerosols. There are significant differences.
Dental aerosols are generated by either handpiece coolant, ultrasonic scaler or 3-in-1 syringe. This are mainly water which is contaminated by saliva, oral and nasal secretions which implies the amount of virus present in dental generated aerosols will be significantly less than medically generated aerosol.  In addition, the use of high-speed suction is known to reduce the amount of aerosol by >90%. The use of rubber down has an even greater reduction in the contaminated aerosol.

Hand washing

Correct handwashing  – soap and warm water for 20seconds minimum is the most effective and it removed the virus from the hands and reduces contract spread. Soap breaks down the lipid (fat) membrane of the virus, killing it..
Sanitisers are less effective especially if hands are visibly dirty or greasy. Many do not use sufficient amount of sanitiser or wipe it off before it has dried. A number of hand sanitisers do not have sufficiently high (at least 60% alcohol) levels of alcohol to be effective.


Public mask-wearing:
Wearing of masks in public places is ineffective unless everyone is wearing them. Public wearing masks reduce potential spread of virus from an infected individual to others by reducing the amount of droplets exhaled especially when coughing. However, use of medical masks en-mass by a population would significantly reduce the number of masks available for health-care workers. The use of cloth / fabric mask is as effective in reducing aerosol transmission, but can lead to compliancy in believing it is providing protection to the wear who may then reduce their hygiene regimes.

Healthcare workers:
During the SARS epidemic FRSM (Fluid Resistant Surgical Mask)  ‘routine’ surgical mask and FFP3 masks were both found to be both around 80% effective.
The FRSM is effective until it becomes damp/moist in routine clinical circumstances. However, it is not very effective when aerosols are being created. These are known as AGPs – Aerosol Generating Procedures.

Dentistry routinely creates aerosols by water cooling of burs in hand pieces, ultrasonic scalers and 3-in-1 syringe. These dental generated aerosols, which are contaminated by the patient’s saliva, oral and nasal secretions, are distributed up to 1.5 meters from the patient’s head/mouth and mainly towards the assistant/nurse. The use of rubber dam and high speed suction significantly reduce the quantity of the aerosol.

Aerosols with viable corona virus can remain in the air for 1-2 hours, but this is affected by gravity and air circulation. Hard surfaces can retain viable corona virus for up to 72 hours. Hence, good air circulation (and why it is safer at outdoor venues over indoor) is important and cleaning of hard surfaces between patients is essential.

In an ideal world a surgery could have a laminar air flow, high-level entry of air and low-level exit essentially ‘pulling’ any aerosol downward assisted by gravity. This methodology is commonly used in industry eg paint spraying.

The FFP3 mask (NB there are 3 levels of FFP protection; levels 1-2-3 : see below) are effective when AGPs are occurring. BUT they must be used on bare skin – NO beards/moustaches! They must be properly fitted and tested that they are sealing correctly.  Once fit tested (where a hood is used and a noxious smell introduced to ensure a seal to the face) only same make/model should be used as variations in design fit differently on different faces.

Remember PPE is there is protect the wearer not necessarily the patient. Some valved FFP3 masks filter the inhaled air, but not exhaled air. So, therefore, there is potential for a non-symptomatic infected individual wearing a valved FFP3 mask to infect another.  This is why some FFP3 wearers are also wearing a FRSM over the valved mask.

The routine FRSM surgical mask are effective in the normal clinical situation and FFP3 are only recommended for use when medical AGPs are being created.

The current UK recommendations are FRSM are for use in circumstances when close patient contact – less than 1m the exception to wearing FRSM as routine are in ICU, ITU and HDU managing COVID-19 patients.

Incubation & Infectious period

It was initially thought that similar to SARS, COVID-19 patients were considered infectious when displaying symptoms and they are not infectious before symptoms occur.

However, this is not clear cut and some non-symptomatic and  pre-symptomatic cases can transmit the disease between 3-6 days before symptoms occur. It appears the level of infectivity is significantly reduced after 7 days from the onset of symptoms with the average time from onset to recovery is 2 weeks and 3-6 weeks for critical cases.

What are the risks?

Well, the problem is this is a very new disease, the data is still incomplete, in that only a few countries have passed through all the phases of the epidemic.

We have passed through the Investigation Phase (recognising the virus) ; Recognition Phase (cases confirmed with person-person transmission);
Many of the worlds countries are either in the Acceleration Phase (virus affecting people) or the Deceleration Phase (constant decreasing numbers of cases).  Finally we will pass into the Preparation Phase, after the epidemic has subsisted, monitoring and preparing for another wave of disease. This is where China appears to be at present

Because very few countries have passed into Deceleration Phase, the data is incomplete and overall infection, morbidity and mortality rates cannot be accurately calculated. Hence science is using mathematical / computing modelling to try and predict the outcomes. As more data becomes available this will affect the models – hence the changes in advice and political actions.

So, let’s look at the data to try and understand the risks

What I believe part of the problem is peoples’ risk perception… we all have varying degrees of risk we are prepared to accept and the media can significantly influence it’s perception.

There are a number of problems when trying to look at and compare the data:

The first problem is in comparing countries, as countries are not undertaking the same testing and reporting regimes: Secondly, countries are all managing the epidemic differently using different strategies, but often using similar terminology which further confuses things: Finally, we are ‘obsessed’ with the number of daily deaths.

The number of daily deaths can be inaccurate due to how they are recorded and in fact are a poor indicator of what is occurring. It is probably better to examine the additional number of deaths over that normally expected and in the UK (population of about 63Million) around 1,400 die every day.  COVID has definitely caused a significant increase in additional deaths. In the UK analysis of additional deaths indicates the peak was 8th of April and since then has been declining.

What is the current risk?

For this we should look at IFR. The Infection Fatality Ratio. WHO has reported the IFR as 3.8%. On the Diamond Princess IFR was overall 1.3% Wuhan, China the IFR has been reported to be between 0.04% and 0.12% which is significantly less than previously thought.

However, this is not the full story as it is known that those with compounding conditions (diabetes, cardiovascular disease and respiratory illness) and those over 60yrs are at greater risk, with a higher IFR  (Diamond Princess the >70yrs IFR was 6.4%). Also IFR varies within a national population ie age groups and areas of population eg cities vs rural. Hence, one number does not ‘fit all’.  In the UK the overall IFR is about 0.8%

This brings me onto the risk for health care workers. This has made regular news in the media and has fuelled the perceived risk. The reality is far from the perception. In Italy the IFR for doctors was almost identical with the general population, esp for those over 70yrs. In the UK similar calculations has found the same – that heath care workers have the same levels of risk of death as the general population.

So what is the risk for dentists?

In the UK dental practices were closed early in the epidemic so it is unlikely any dentists who have contracted COVID caught it in a dental surgery. In many other countries dental practices have not had the same ‘lockdown’ and very few dentist infections have been recorded.
We can compare another UK group who have continued to be potentially exposed – Teachers. Schools have remained partially open, and children are known to be non-symptomatic carriers of COVID and are not as disciplined as adults in practicing social distancing and hygiene measures. Also they are caring for children of key workers who could be expected to be at a higher risk of carrying the virus than the general population. We are not seeing a spike in teachers becoming infected with COVID.

Whilst this data is empirical it would seem reasonable to assume that the risk to dentists is no greater than the general population.

Some thoughts on the UK management of Dentists

Frankly, it has been appalling, with at best poor leadership at all levels, and at worst a condescending lack of knowledge of the clinical skills the dental profession has to offer.

The decision to close all dental practices with no proper provision for the management of patients in pain was a gross error. This coupled with poor and contradictory advice on PPE requirements, Standard Operating Procedures and excessive reliance on personal opinion, much of which is not evidence based, has left the profession in disarray.

Practice Closure

Closing dental practices without provision for patients was a knee jerk reaction with serious consequences for our abandoned patients. Initially, it was not clear if this closure applied to only NHS practices or to both NHS and Private. Many practices immediately took action to organise and set up Urgent Care Centres, to be told they could not. Compounding the error.

Practices should have been given clear PPE guidance, SOPs and allowed to manage patients. However, lack of decision making by our leadership both nationally and locally resulted in unnecessary delays. Dentists were instructed to practice in a manner that for years has been acknowledged as being unacceptable ie phone triage and AAA (Analgesics, Antibiotics and Advice), or in my day in in a busy Max Fac and A&E post known as PPP (Paracetamol, Penicillin and er… I will let you guess what the 3rd P stands for!).

Confusing messages

Almost everyone and their uncle has had published their opinion on PPE and SOPs. Different organisations have called for the “necessary” PPE for all, but not looked at the evidence to make those recommendations.  All have failed to separate “necessary” and “desired”. Necessary is what the evidence deems required to be safe. Desired is what people want, and is mainly way in excess of the actual risk.

Rewards for doing less

The NHS is to continue funding NHS practices, albeit at an abated contracted value, which is yet to be determined. But, with as yet no guidance of how associates are to be paid. In addition, the un-wanted consequence of NHS money with no ties, is that those practices who are working to provide patient care are taking on a massive workload and cost, whilst others sit back. Continuing NHS payments should be linked to activity ; ie if practice is not active, a minimal payment, practices working as UDCCs should receive additional funding.

Private practices are left in limbo with no government support, which is unacceptable. Private dentistry has an important role to play in patient care and way must be found to allow their participation in patient care as well as financial support

Lack of recognising Dentists skills

Dentists and the dental team are highly skilled communicators and organisers with high levels of manual skills. These skills could be used in hospitals to relieve medical staff in A&E on wards etc.