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

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

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Dr. Fatima Ebrahim and Dr. Sue Chincholi started this petition to Provincial Dental Associations and


This letter is in response to the re-opening guidelines issued by Saskatchewan and Ontario dental colleges taking extreme measures against dental aerosols by claiming that they will persist in the air for 120+ or 180+ minutes and that any aerosol generating procedures cannot be performed unless they are in a completely enclosed room. These rooms must then be left unused for 120 or 180 minutes after the procedure to allow aerosols to settle.

First and foremost, what evidence is each College using to formulate their guidelines? All decisions need to be evidence-based as these guidelines can have strong repercussions on the entire industry. Remember that most dental clinics have semi-enclosed bays or completely open bays so they will not have any capacity to meet these requirements and the time required to allow aerosols to settle is extreme making it largely impossible to practice modern 20th century dentistry if only hand instrumentation can be used. Access to affordable care for dental services will be greatly hindered by these guidelines and it will be near impossible for dentists to run a business, pay the bills, maintain their staff load and provide affordable dental services if rooms have to be sequestered and left vacant for half the schedule given these new guidelines.

We have not seen a list of references in any of the re-opening guidelines posted by these Colleges so we wanted to share the following articles and hope that they will be helpful:

1. Study published in the British Dental Journal (part of the highly respected Nature group of journals) demonstrated that aerosols generated within dental clinics settle within 10-30 minutes - i.e. within the time frame of the procedure, so if you start a cavity prep during the first 15 minutes, then fill during the last 15 minutes, the majority of aerosols would have settled.

Microbial aerosols in general dental practice. Bennett,A., Fulford, M., Walker, J. et al.

2. Another study that shows that by using a High Volume Suction / Evacuator (HVE), use of HVE reduced 96%+ of all bacterial aerosols:

Studies on Dental Aerobiology: I. Bacterial Aerosols Generated during Dental Procedures

So use of high vacuum suction is the most effective way to minimize aerosols, but worst case scenario any remaining aerosols will settle within the 10-30 minutes anyway.

3. Based on both these points, we do not need enclosed rooms from floor to ceiling with doors to sequester aerosols. Instead, HVE should being used to decrease 96% of aerosols when doing AGMPs.

4. When considering the airborne nature of COVID-19, please read:

Aerosol and Surface Distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in Hospital Wards, Wuhan, China, 2020

Air, Surface Environmental, and Personal Protective Equipment Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) From a Symptomatic Patient

Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosol in Wuhan Hospitals during COVID-19 Outbreak

Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center

Influenza Virus Aerosols in the Air and Their Infectiousness

Overall Take Away:

Based on the evidence and the discussion by the above researchers, the concern with COVID-19 is not that it is a virus in the air. Instead, it is virus-laden aerosol deposition causing surface contamination and subsequent human infection through contact. Leaving a room vacant or unused for 2-3 hours doesn’t prevent the contact transmission which is the primary form of transmission for COVID-19. So focus should be on preventing the majority of aerosols through HVE. With the remaining aerosols that settle within the next 10-30 minutes, the emphasis should be on disinfecting surfaces. This virus can persist on surfaces for 24-48 hours so leaving a room vacant doesn’t address the primary mode of transmission.

5. When considering PPE and specifically N95s, please see the following infographic:

Studies on Hospital Precautions with SARS for routine procedures have shown surgical and N95 performed equally well against transmission

Large scale studies on transmission of respiratory diseases in hospital settings have shown Surgical Masks are equivalent to N95s for prevention

Effectiveness of N95 Respirators versus Surgical Masks against Influenza: A systematic review and meta-analysis

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial

Overall Take Away:

• Level 2 & Level 3 surgical masks are rated to filter ≥98% of both viruses and bacteria 

• A Level 3 Mask has slightly higher ability to absorb moisture than Level 2 (relevant for high speed with water spray) but if a face shield is being used to prevent splatter, there’s no effective difference

• The CDC only recommends N95 use for patients suspected of being sick with COVID-19 - patients who should not be in our offices in the first place. Special Respiratory Level Precautions in the major hospitals in the USA do not even use N95 masks.

• We should NOT be taking the supply of N95s away from the hospital workers who are working on known infected patients. We should focus on applying our existing Droplet Precautions correctly (like using HVE routinely). N95 masks are not needed for what dentists are doing.

6. Lastly, the study that is commonly being cited with regards to COVID-19 remaining viable in aerosols for 2-3 hours has been wrongly interpreted and misapplied in the context of dentistry: 

Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1

Overall Take Away:

• The aerosol in the study was manufactured and maintained in an artificial TUBE to see how long the virus could survive in particle size.

• The times being reported assess how long the virus can survive within an aerosolized particle (i.e. up to 3 hours)

• The article does not assess how long the aerosols actually persist in the air and how long it takes for the aerosols to settle on surfaces (which from the Nature study posted above is typically between 10-30 minutes in the dental setting).

• Remember, once the virus settles on surfaces and counters, it can be wiped with disinfectant and killed.

• It is not survivability time of the virus in an aerosol that is important, it's sedimentation/settling time of the aerosol that is important. These are two completely different outcomes which should not be confused and the article should not be misapplied when formulating guidelines within the dental context.

• Lastly, the article deals with mechanical creation of aerosols in an artificial tube environment – not the creation of dental aerosols from various dental procedures within the clinical dental setting.

• This article should not be relied upon when evaluating dental aerosols when there are much more applicable studies done in the dental context such as the Nature article posted in #1 above and the article on minimizing 96% of dental aerosols with HVE in #2.

We truly hope the decision regarding the guidelines for dentists to re-open in our province and in Canada as a whole will be evidence based, thoroughly researched and properly supported by the literature.

- On behalf of all Canadian Dentists

Written and compiled by Dr. Fatima Ebrahim, BScH, DDS, MSc, Dip. Ortho, FRCD(C) with assistance from Dr. Scott Frey, BSc, DDS, MSc (Ortho)

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