Insist that Canada-wide Dental Practice Re-Opening Protocols be Evidence-Based!

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Another Letter Written in Support of Evidence-Led Sustainable Precautions.

We would like to thank Dr. Paul Korne for his permission to publish his well-written letter here. We are happy to see similar thought processes and advocacy by our colleagues. 

Please find it below:

"The task of making choices in how we will equip our offices and arm our staff to deal with the coronavirus is fraught with uncertainty. This is made especially cogent given that scientists do not yet understand the true character of this pathogen.

According to Daniel Kahneman in his seminal book ‘Thinking, Fast and Slow,’ “an unbiased appreciation of uncertainty is a cornerstone of rationality – but it is not what people and organizations want. Extreme uncertainty is paralyzing under dangerous circumstances, and the admission that one is merely guessing is especially unacceptable when the stakes are high. Acting on pretend knowledge is often the preferred solution.” And in this period of uncertainty, dentists appear to be making a series of unsubstantiated decisions.

Some of the suggestions put forward at our virtual conference last week included the construction of negative pressure operatory rooms, the wearing of full-body protective gear and changing of same for every patient, the wearing of N95 masks, or even, the full Ebola-like aerosol evacuation setup proposed by an oral surgeon. All of these strategies are designed to mitigate the contamination from potential aerosolized virus emitted from patients during dental procedures.

Moreover, some of the provincial licensing bodies have started to put forward their own recommendations. The Saskatchewan College of Dental Surgeons (CDSS) released their protocol update on April 27, 2020. Guidelines include walled-off AGP (aerosol-generating procedure) operatories whose doors must remain closed to allow aerosols to settle for 2 hours after a procedure prior to cleaning and disinfecting the work area for the next patient.

It is clear that the recommendations put forth are varied and inconsistent. While the safety of the dentist office community (dentists, staff and patients) must always be the ultimate priority, it is the thesis of this essay that are we not using evidence-based protocols to make these important decisions. 

Fact: COVID-19 is primarily transmitted by large droplet and contact transmission. To account for the appreciation of uncertainty, reports will responsibly add that there exists “potential transmission through respiration, indicating that more transmission routes may be possible.”1 It is important to remember that transmission of the virus to front-line health care workers from very sick, COVID-positive patients during intubation or other invasive procedures mandating close contact is not a parallel situation to creating aerosols in dentistry. The medical patients are expectorating large droplets in sputum carrying large viral loads. 

Fact: even if COVID-19 is transmitted through dental aerosols, HVE (high volume evacuation) removes nearly all generated aerosols2.  Close inspection of the raw data from Bennet et al. shows that the average reduction of aerosols was over 99% from both assistant-held and non-assistant held high volume suction devices during cavity preparation, water-spray and polishing restorations. Moreover, any spike in aerosol generation in a dental operatory falls to normal values within 10-15 minutes of completion of the aerosol-generating procedure, allowing enough time for disinfection of the operatory and the seating of the next patient. In addition, “there was no evidence of spread of microbial contamination outside of the treatment room during the peak aerosol concentration periods.” Further reduction of bioaerosol dissemination in a dental office can be achieved through the installation of portable air cleaning systems3,4.

It therefore appears that: 1) aerosol-generating procedures do not have to be performed in closed operatories; 2) the recommendation from the CDSS to wait 2 hours to allow for settling of aerosols within a dental operatory is inconsistent with available evidence and would significantly affect dentists’ productivity and efficiency;  and 3) while portable air filtration systems would further improve air quality and filtration of particle contaminants, their scientific utility is optimized when positioned in dental operatories or close to where aerosol-generating procedures take place.

Even if less than 1% of aerosols escape containment, dentists, hygienists and assistants are further protected by standard personal protective equipment like masks and glasses (or face shields). It is highly improbable that any residual viral load will be in sufficient concentration to infect the dental health care worker with disease (for an excellent description of viral load and disease severity, please read Siddhartha Muckerjee’s essay entitled “How does the coronavirus behave inside a patient?5).

Fact: aerosolized virus is not a new concept to dental treatment. While we do not yet understand the true nature of the novel coronavirus, dentists have always had to deal with the consequences of patients being infected with viruses. This includes pathogens with higher infectivity (R0 values) like tuberculosis, higher mortality rates (AIDS) and greater prevalence (influenza). In addition, given the increasing penetration of this virus (according to the website there were 3,025,726 confirmed worldwide cases of the disease on the morning of May 2, 2020; this figure is likely 10-50 times higher) and the fact that dental offices have been treating patients in many countries, isn’t it surprising that there has not been a single reported case of a dental health care worker being infected from a patient?

Fact: preclinical rinsing with 1% hydrogen peroxide purports no scientifically demonstrated reduction of aerosol generating virus particles. Preclinical rinsing with hydrogen peroxide has been recommended ad infinitum in the COVID-19 dental literature, although a proper study corroborating its use does not exist.  The most referenced article for this claim6  is strictly an opinion and lacks experimental data; another cited systematic review article7 looks at reduction of CFU (colony forming units) of bacteria and not at viruses or the coronavirus in particular. Kahneman would describe this widespread fallacy as confirmation bias, where “people (and scientists, quite often) seek data that are likely to be compatible with the beliefs they currently hold.” Are there other widely recommended practices without scientific validation that in the economy of time and/or effort, we choose to simply follow without proper investigation?

In 1986, I was an intern at Mount Sinai Hospital in Toronto. AIDS was still a disease with no treatment (AZT would only be available a year later) and HIV-positive patients were being referred to hospital dental clinics for routine care. I remember vividly the meticulous preparation: full surgical uniform, double gloves, mask, glasses and bonnet to perform the simplest amalgam or periodontal scaling. The term “universal precautions,” a set of infection control guidelines and practices, was introduced during this period, and dentists have been practicing with these conventions ever since. Nearly forty years after AIDS first appeared, with no cure and a world-wide death toll of 36 million, most dentists today feel quite confident in delivering routine dental care to AIDS patients with their existing infection control setup.

It is my sincere belief that the safest place for me and my staff during this time is in my office, treating patients. Our strict infection control regimens have shielded us, our staff and our patients from many pathogens and will protect us in the face of COVID-19. Do we need to modify our practices? Absolutely. Equipping all staff with masks (level 3 medical masks perform just as well as their N95 counterparts8) and goggles or face-shields for the entire day; minimizing the number of patients and their caregivers in the office; removing magazines and disabling coffee machines and toothbrush stations at the office; asking patients to wash their hands prior to their appointments and perhaps even wearing a mask until the dentist or hygienist is ready to begin their work; doing virtual consultations instead of in-office ones; modifying schedule templates to afford more time on the front and back end of appointments for health history questionnaires and meticulous cleaning of dental operatories; and protecting the front-of-house staff with acrylic sneeze guards – these are some common-sense strategies that everyone should consider prior to reopening their offices.

Why do I think it’s important to convey this information? Firstly, the choices we make as dentists must reassure the public that we are taking the proper, measured and scientifically defendable route to reopening our offices. Inconsistencies in levels of standard of care will only squander the trust and goodwill that we have worked so hard to earn over decades of service to our patients and communities. If we uncritically accept suggestions based on the likelihood of extreme and improbable events, we might push the cost of dental care outside the reach of people who would normally be able to afford it.

Second, I am writing this letter to my colleagues who are more than private-practice dentists: you are educators, leaders in provincial and national general and specialty associations, organizers of conferences, examiners, lecturers and mentors. Dentists must hold our provincial licensing body accountable to develop sensible, evidence-based protocols that mirror the will of their members. If you know someone on the Board of Directors or the Executive Committee of the Ordre des Dentistes du Québec, contact them and discuss these important issues before the protocols are put to paper.

As dentists we have a long history of leading the way in preventing the transmission of communicable, infectious diseases. Consequently, we are already well poised to meet this new challenge. It is my belief that minor modifications to our already exemplary protocols are all that is needed to keep our staff and patients safe.  At times like this we must embrace the scientific method which has guided our profession since inception. 

Paul H. Korne

Montreal  May 3, 2020


1.     Suri S, Vandersluis Y, Kochar A, Bhasin R, Abdullah M. Clinical orthodontic management during the Covid-19 pandemic. Special article published online. Angle Orthod., April 27, 2020


2.     Bennett AM, Fulford, MR, Walker JT, Bradshaw DJ, Martin MV, Marsh PD. Microbial aerosols in general dental practice. Brit Dent J. 2000 Dec 23; 189:664–667


3.     Chen C, Zhao B, Cui W, Dong L, Ouyang X. The effectiveness of an air cleaner in controlling droplet/aerosol particle dispersion emitted from a patient's mouth in the indoor environment of dental clinics. J R Soc Interface. 2010 Jul 6; 7(48): 1105–1118


4.     Hallier C, Williams DW, Potts, AJ, Lewis MA. A pilot study of bioaerosol reduction using an air cleaning system during dental procedures. Brit Dent J. 2010 Oct 23;209(8):E14 


5.     Mukherjee S. How does the coronavirus behave inside a patient? The New Yorker Magazine. March 26, 2020


6.     Peng  X, Xu X, Li Y, Cheng L, Zhou X, Ren B. Transmission routes of 2019-nCoV and controls in dental practice. Int’l J Oral Science. 2020; 12(9)


7.     Marui VC, Souto MLS, Rovei ES, Romito GA, Chambrone L Pannuti CM. Efficacy of preprocedural mouthrinses in the reduction of microorganisms in aerosol. JADA. 2019; 150(12): 1015-1026


8.     Radonovich LJ Jr, Simberkoff MS, Bessesen MT, Brown AC, Cummings DAT, Gaydos CA, Los JG, Krosche AE, Gilbert CL, Gorse GJ, Nyquist AC, Reich NG, Rodriguez-Barradas MC, Price CS, Perl TM, ResPECT Investigators. N95 Respirators vs medical masks for preventing influenza among health care personnel: a randomized clinical trial. JAMA. 2019; 322(9): 824-833. doi:10.1001/jama.2019.11645






Dr. Fatima Ebrahim and Dr. Sue Chincholi
1 year ago