Nissit Patel reviews the literature and gives his thoughts on how to protect dental teams and patients after the lockdown.
As a profession, dentistry is classified at being a high risk for transmission of COVID-19. The reasons being that the main routes of infection all are highly relevant to everyday procedures in dental practice with aerosol being the hotly debated topic. We all know that we will not be returning to practice as normal so we must now consider how we can further protect ourselves, staff and patients, not just for COVID-19 but any potentially harmful infectious agents.
Aerosol consists of water, saliva, blood, debris and microorganisms such as bacteria, fungi, viruses and protozoa. Along with their metabolites, such as lipopolysaccharides/endotoxins and other toxins ( Hallier et al, 2010). Not a desirable cocktail!
The use high-speed handpieces and ultrasonic equipment creates more airborne contamination via aerosol than any other instruments in dentistry (Harrel and Molinari, 2004 ). Other devices include the air/water syringe, air polishing, air abrasion and hard tissue lasers, which use water. Aerosol can be classified in order of size:
- Large droplets, greater than 50 microns, will drop until they contact a surface. In the typical dental surgery, this could be the chair, worktop, storage unit, sink, floor, patient and dentist. This is potentially where contact contamination could take place (Szymanska, 2007)
- Droplets less than 50 microns can remain within the air space until evaporation, leaving residual nuclei. These are much smaller at less than 10 microns, containing bacteria that relate to respiratory infection (Atkinson et al, 2009.)
- Droplet nuclei, as referenced above, potentially can contaminate surfaces up to one metre away. They remain airborne for up to two hours (Dutil et al, 2009; James and Mani, 2016).
Van Doremalen et al, highlighted examples of the longevity of COVID-19 in various places:
- The virus is viable up to 72 hours after application to plastic and stainless steel surfaces
- The virus is viable up to 24 hours on cardboard surfaces
- It is viable up to nine hours on copper surfaces
- And the virus is viable in suspended aerosols up to three hours.
In general, I believe that cross infection control and cleaning procedures are at a high level in dental practice. But with this pandemic, our processes will be under even greater scrutiny. It is inevitable that we need careful analysis to further enhance how to minimise aerosol and transmission.
It would seem imperative that we seek to reduce the amount of aerosol in general practice as the first line defence. There are simple ways to do this, which most practices implement already.
High volume aspiration (HVA)
In most practices, we use high volume aspiration (HVA) routinely. A recommended diameter size of 8mm and greater is advised to remove high volumes of air and up to 90% of aerosol (Harrel and Molinari, 2004 ).
Saliva ejectors, have a much lower diameter. They are not effective at removing aerosol, so we should minimise use in everyday practice, unless its use is in addition to the HVA.
With regards to hygiene procedures, it is likely that assistants will need to adequately manoeuvre the HVA. Although this is standard practice at Progressive Dentistry, I accept financially this may not be an option for many practices. However, working schedules may have to be more flexible to accommodate this if employing extra staff is not an option.
Rubber dam should be used in all endodontic and most adhesive dental procedures. However, the level of aerosol is greatly reduced with use as the oral cavity is essentially ‘sealed’. It would therefore make sense to incorporate use within all aerosol producing techniques (Harrel and Molinari, 2004). The challenge would be with routine hygiene procedures. I would suggest a split dam technique as an option, which still allows access to subgingival areas but provides a level of seal. This is not ideal and a compromise option, but an improvement nonetheless.
Alternative options include the use of additional dental isolation systems such as Isovac and Isolite from Zyris. These look promising in terms of hygiene and routine dental procedures.
A recent paper stated that rinsing with 1.5% peroxide for 60 seconds reduces viral load and disinfects the throat. Peroxide drops coronavirus replication by >4 logs. In practice, Peroxyl is a peroxide-based mouthwash that we use routinely.
Other studies have shown the use of anti microbial rinses for 60 seconds significantly reduces the level of oral microorganisms in the aerosols generated during routine dental procedures (Veena et al, 2015). However, there are significant concerns that chlorhexidine is not effective against COVID-19. An alternative would be povidone-iodine mouthwash such as Betadine (Kumar et al, 2007).
Dental practices may struggle with ventilation management, especially if they are situated within confined spaces. There is quite strong evidence that good ventilation can impact on the spread of airborne infection (Li et al, 2007).
Various studies have shown that air cleaning systems do reduce the amount of aerosol created during dental procedures such as ultrasonic use, tooth preparations and extractions (Martin and Moyer, 2000; Noakes et al, 2004).
I have come across a few systems that would suit a dental practice where the systems contain pre filters, HEPA filters, carbon filters and UVC lamps. The theory is not only to filter the air but to destroy bacteria and viruses, which would be the ideal. These include units by Radic8 and Surgically Clean Air.
Personal protective equipment (PPE)
PPE, in particular masks, has been a major news topic. A recent BBC headline states: ‘UK Failed to stockpile crucial PPE’ and Scotland became the first UK nation to advise the use of facial covering when social distancing may not be possible such as on public transport or food shops.
It is useful to have a description of masks and highlight the difference between them.
These are the ones we use routinely in dentistry and were readily available prior to the COVID-19 crisis at a reasonable price. They have a waterproof outer aspect and protect the wearer from splatter and large droplets. They do not protect against airborne infectious agents such as coronavirus.
However, at the very least, if a surgical mask is worn by a contagious person, then this mask will stop the spread to his or her immediate surrounding area. This is the reason some countries, such as the Czech Republic, have made the use of masks mandatory when outdoors.
These are masks that prevent the wearer from inhaling aerosols, gases and vapours that are potentially harmful. These may protect the wearer from airborne infectious agents such as coronavirus if fitted properly.
In Europe, there are three classes of respirator masks FFP1, FFP2 and FFP3 and they must meet the European Standard EN1 149: 2001.
- FFP1 refers to the least filtering of the three masks. It includes an aerosol filtration of at least 80% and leakage to the inside of maximum 22%. This mask is mainly used as a dust mask such as one you would use for DIY
- FFP2 masks have a minimum of 94% filtration percentage and maximum 8% leakage to the inside. Their use is mainly in construction, agriculture and by healthcare professionals against influenza viruses. They are currently used for protection against the coronavirus
- FFP3 masks are the most filtering mask of the FFPs. With a minimum filtration percentage of 99% and maximum 2% leakage to the inside, they protect against very fine particles such as asbestos.
It therefore makes sense for us to use a minimum of FFP2 and ideally FFP3 masks properly fitted when treating suspected COVID-19 cases. There is also the argument of using these for aerosol generating procedures on low-risk patients but with supply problems likely to continue in the short term at least, this may not be a feasible option.
Pre COVID-19, my personal standard practice was a surgical mask and a full face visor. Given the lack of peripheral seal, face shields should not be used alone as a form of PPE. But their use makes complete sense when dealing with aerosol and splatter coupled with appropriate face masks. An excellent review paper by Raymond Roberge (2016) highlights the advantages and disadvantages of face shields.
Loupe companies are now offering face shields that can adapt over the loupes, which was not feasible with traditional visors and shields.
Personal protective gowns and coveralls are classified based on barrier efficiency that validates protection from fluid penetration under certain pressures. Interestingly, it has been shown that surgical gowns made from non woven polypropylene showed significantly decreased virus adherence property compared to chemical protective coveralls with the same or higher barrier efficiencies (Katoh et al, 2019).
Donning and removal
Perform hand hygiene before putting on PPE. The order for putting on PPE is apron or gown, surgical mask or respirator, eye protection and finally gloves.
For removal, gloves are firstly removed, followed by the apron or gown, eye protection and finally mask or respirator. Hand hygiene should immediately follow removal of PPE.
Patient screening is likely to be with us for a while. The first step is identifying suspected cases of COVID-19. We should also measure the temperature of the patient. It is advised that a contact-free forehead thermometer is used for this. There are many available on line.
In terms of taking a history, the following set of screening questions can help identify potential infection:
- Do you have a fever or have you experienced a fever within the past 14 days?
- Have you experienced a recent onset of respiratory problems, such as a cough or difficulty in breathing, within the past 14 days?
- Have you come into contact with a patient with confirmed 2019-nCoV infection within the past 14 days?
- And have you come into contact with people who come from areas with recent documented fever or respiratory problems within the past 14 days?
- Are there at least two people with documented experience of fever or respiratory problems within the last 14 days, having had close contact with you?
- Have you recently participated in any gathering, meetings, or had close contact with many unacquainted people?
After the screening questionnaire:
- If the patient replies yes to any of the screening questions, and his or her body temperature is below 37.3°C, postpone the treatment until 14 days after the exposure event
- If the patient replies yes to any of the screening questions, and his or her body temperature is 37.3°C or higher, postpone treatment and follow advice on the current guidelines for isolation
- However, if the patient replies no to all the screening questions, and his or her body temperature is below 37.3°C, treatment should be permitted
- Finally, if the patient replies no to all the screening questions, but his or her body temperature is 37.3°C or higher, the patient should be directed for further medical care (Peng et al, 2020).
For the foreseeable future, it is unlikely we will see a waiting room full of patients. The guidelines are likely to involve social distancing measures of at least two metres from patients and reception staff and other patients or a one-in one-out protocol. Reception screens may be an option, similar to recent measurements taken at several supermarkets. Hand sanitiser should be available to all.
We are likely to have to offer flexible time frames for appointments with adjustments to the diaries of dentists, hygienist/therapists. Perhaps it will require shifts rather than a continuous working pattern of the surgeries.
I believe dental cross infection systems in terms of cleaning and sterilisation are robust and already highly regulated. It may be that extra time will be required between patients for prolonged disinfection considering areas such as door handles, computers, chairs, desks as well as the usual areas within the practice.
This is speculation for now; time will tell.
The world has changed irreversibly, and every healthcare profession will have to adapt to protect their staff, patients and clinicians. In dentistry, there are 10 steps we could take to start providing treatment aiming to prevent transmission to the best of our capabilities:
- Careful screening of patients pre treatment
- Alteration of patient appointment times/flexible time frames
- Reception screening, social distancing measures
- Consider clean air systems within reception areas and surgeries
- Reducing aerosol
- Always use HVA
- Use rubber dam or consider additional isolation systems such as Isovac/Isolite
- Provide assistants to hygiene/therapists for HVA
- Pre procedural rinse with either Peroxyl or Betadine
- Enhanced PPE:
- Respirator of at least FFP2, ideally FFP3 for aerosol procedures in high risk patients
- Surgical gowns made from polypropylene in high-risk patients
- Face shields for every procedure
- Proper donning and removal procedure
- Robust hand cleaning procedures
- Extra time for disinfection considering additional surfaces within the premises
- Follow up protocol for patients to report any COVID-19 symptoms post treatment.
We can implement most of these measures with relative ease. But they will have a major impact on the delivery of our service and will bear a significant financial element. Clean air systems, for example, require greater planning and expense, which may not be feasible for many practices.
My view is that as a profession we are generally meticulous with regards to infection control. Arguably we do more than any other healthcare provider. There is always a rogue element in any walk of life. This is why the profession should be making the decisions, in partnership with the powers that be, to ensure all of our patients and team members are as safe as possible following COVID-19.
The decision process should be based on fact from past and current events with robust scientific evidence to prove any major adjustments have a significant benefit. I implore the authorities to give dentistry a greater level of respect and allow us to start looking after the dental health of our nation as soon as possible.
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