“Aiming to prevent or contain every case of COVID-19 is simply no longer sustainable…”
The above quotation is from an open letter sent on the 6th July, 2020 to the Prime Minister and Premiers of Canada signed by many of the country’s Deputy Ministers of Health, Chief Public Health Officers and Medical Deans.1
It is a realistic assessment of the evolution of a novel virus within a community. Initially the virus will spread in an epidemic or exponential manner to susceptible individuals, the majority of whom will recover but some of whom will die. Once a sufficient level of immunity has been achieved either through previous infections or by vaccination, the epidemic nature of the infection ceases and it becomes endemic within that population. At this stage infections do not cease as there are always susceptible individuals with a baseline level of infection. This baseline gives way to peak seasonal outbreaks, which for coronaviruses are winter and spring. Fortunately, existing community immunity limits the pathogenicity of these localized outbreaks.
SARS-CoV-2 – the presumptive cause of COVID-19 – can be considered a cousin of, at least, four other human coronaviruses responsible for seasonal flus and colds. Consequently, it is a reasonable assumption – supported by the signees of the above letter – that a state of zero COVID cannot be attained but that endemic annual resurgences of it are to be expected.
This concept has been eluded to by Professor Chris Whitty, England’s Chief Medical Officer, as reported in the article, “COVID anxiety has gripped scientists” by Robert Dingwall which appeared in the April 30th, 2021 edition of the National Post. A pertinent quote from the article is, “Prof. Chris Whitty has talked repeatedly of living with COVID as a generally mild endemic infection, much like all the other respiratory infections that we have always lived with. Any interventions in everyday life must be proportionate to that risk, not the images that have filled our TV screens for the past 12 months.”
In recent years Dentistry’s response to infectious disease threats has been to adopt the “better safe than sorry” approach as dictated by the Precautionary Principle. Its response to COVID-19 has been the latest example.2 This article will offer a critique of that principle, and will illustrate how the dental profession can accommodate to the permanent presence of SARS-CoV-2 by minimally altering its pre-pandemic mode of practice.
Definitions of the Precautionary Principle (PP) tend to be variations of the “Wingspread Consensus Statement” drafted in 1998. It states that, “When an activity raises threats of harm to human health or environment precautionary measures should be taken even if some cause and effect relationships are not fully established.”3 Adoption of the PP by governments, public health agencies and professional regulators permits them to enact rules, restrictions and behaviours without subjecting them to scientifically sound validation. PP recommendations are seldom subjected to thorough cost benefit analyses which gives their supporters the mistaken believe that only good emanates from their practice. Professor Frank Cross of the University of Texas emphasized this fault when he stated, “The truly fatal flaw of the precautionary principle, ignored by almost all commentators, is the unsupported presumption that an action aimed at public health protection cannot possibly have negative effects on public health.”3
Cass R Sunstein – the most cited law professor in the United States – understands the fundamental meaningless of the PP. He believes that since all policies and actions generate risks, precautions against these risks create other risks resulting in a never ending series of precautions. This is especially applicable to the health care field where practicing the PP leads to an escalating series of actions to reach the unattainable goal of a risk free absolutely safe environment. These opinions allowed Sunstein to conclude that, “The problem with the Precautionary Principle is not that it leads in the wrong direction, but that – if taken for all that it is worth – it leads in no direction at all.”4
Precautionary Principle and Dentistry
The PP has some merit if the probability of a threat occurring is high.5
Contrary to common beliefs dental practice is not a source for the prolific transmission of infectious diseases. This opinion is supported by the 1991 landmark studies by Goodman of infections potentially transmitted from out-patient facilities including dental offices,6 by an extensive 2010 investigation of dental infection control in the UK,7 by a 2015 article showing the absence of disease transmission from infection control disasters8 and by a 2016 US review which, over a 12 year period, was unable to detect a single case of dentally transmitted HIV and was unable to substantiate the dental transmission of HBV and HCV.9
The Cochrane Collaboration: Oral Health Group is a pre-eminent source for evidence-based dentistry. In 2008 Philip Riley, the Group’s Administrator indicated in a personal communication to the author, that the low level of frequency of infections transmitted during dental treatment prevented any meaningful study of dentally acquired infections. The recent articles cited above support Riley’s claim.
Despite the documented low level of frequency of nosocomial infections of dental origin, the PP has driven Infection Prevention and Control (IPAC) recommendations for the past twenty years. This has resulted in a plethora of clinically unsubstantiated procedures which have become ritualistic in their performance. All dental staff are aware of the extensive use of plastic covers and disinfectants, the exhaustive procedures associated with the cleaning, packaging and reprocessing of instruments, the detailed recording of every IPAC procedure, and the universal use of gloves.
As indicated by Riley the paucity of dentally acquired infections means that it is impossible to determine to what extent – if any – these pre-pandemic IPAC procedures have had in preventing or controlling dentally acquired infections. However, as noted by Cross and Sunstein these PP induced actions have had negative impacts.
Dental offices have become a source of environmentally hazardous plastics, disinfectants can create anti-bacterial resistance, adult onset asthma and may be carcinogenic especially if they contain triclosan.10,11 The reprocessing of dental instruments is time consuming, expensive and even with the incorporation of biological monitors does not guarantee a sterile state.12 Recent extensive reviews have shown that the overuse of gloves in lieu of proper handwashing is promoting health care associated infections.13 Dental offices are being subjected to stressful often protracted and reputation destroying IPAC related audits occasionally on the flimsiest of excuses (some of which have rancorous overtones).
There is no doubt that PP driven IPAC recommendations have inflated the cost of dental treatment, have created numerous other risks and hazards as predicted by Cross and Sunstein, and have not been shown to reduce the historically low level of dentally acquired infections. It is with this understanding that the relationship between COVID-19 and dentistry will be discussed.
COVID-19, Dentistry and the Precautionary Principle
It is likely that no other disease has been so intensely studied during a twelve month period than has COVID-19. Accordingly, only information on it pertinent to this article will be discussed.
It will begin by defining a disease as, “A disorder of structure or function in a human, animal or plant, especially one that produces specific signs or symptoms or that affects a specific location and is not simply a direct result of a physical injury.”14 Normally a disease is diagnosed by a unique combination of signs and symptoms. According to the Canadian Government, “To date, there is no list of symptoms that has been validated to have high specificity or sensitivity for COVID-19.”15 This is why the controversial PCR test with all of its inherent faults has become the primary means of diagnosing COVID-19.16
Despite this Government admission, the PP demands that dental staff and their patients complete questionnaires on a wide range of signs and symptoms whose frequency of association with COVID-19 is unknown.15 The presence of a single sign or symptom no matter how vague or non-specific (e.g. tiredness, muscle aches, or confusion) results in a failed COVID-19 screening test. As a consequence, individuals could be unjustifiably subjected to self-isolation and further medical interventions. It seems counter intuitive to base a screening test on signs and symptoms that are not specific for the disease under consideration. That might be the reason why a Cochrane Review of screening for Covid-19 concluded that, “We are unsure whether combined screenings, repeated symptom assessment or laboratory tests are useful.”17 In a somewhat similar vein a report by Alberta Health Services indicated that there was limited evidence that subjecting health care workers to screenings prevented the nosocomial transmission of COVID-19.18
The following is a quotation from the Government of Canada. “Fever is only one way to help identify a person who might have COVID-19 infection. Fever often indicates the presence of an infectious disease, but other non-infectious medical conditions can also result in above normal body temperature. Fever is not usually the first symptom of COVID-19, and in some cases, a fever never develops. Temperature readings alone should, therefore, not be used to diagnose, COVID-19, regardless of what kind of thermometer is used.”19 The authors of a December 2020 article in the online journal of the Infectious Disease Society of America stated that non-contact infrared thermometers fail as a screening test for SARS-CoV-2 infection.20
These screening tests are of questionable value, can result in patients being subjected to unnecessary medical investigations and, as additional employees are required, adds to the cost of dental treatment. However, they unambiguously illustrate the negative consequences of a reliance on the PP.
Routes of Transmission
The supposed routes of transmission of COVID-19 when viewed through the lens of the PP have altered dramatically the practice of dentistry. Patients are required to wait in empty rooms bereft of reading material or in their cars, receptionists sit behind plexiglass screens, hand sanitizers are abundant and clinical staff are unrecognizable in face shields, masks, gowns and gloves. An understanding of how COVID-19 is transmitted brings a different perspective to the futility of these new protocols.
For the purposes of this article three routes of transmission will be considered: by fomites from inanimate surfaces and objects, from asymptomatic patients and from aerosols.
A January 2021 review in Nature discusses why the presence of SARS-CoV-2 on doorknobs, magazines, furniture, light handles, countertops, face shields and gowns is not a major source of infection.21 In February 2021 a WHO representative informed Nature that, “…there is limited evidence of the coronavirus being passed through contaminated surfaces.”22 These comments support the investigations performed by Dowell and Goldman.23,24 In real life as opposed to laboratory conditions, Dowell was unable to find viable viruses on fomites.23 Goldman is of the opinion that there has been an exaggerated risk of the transmission of COVID-19 from surfaces and objects and that, “…the chance of transmission through inanimate surfaces is very small, and only in instances where an infected person coughs or sneezes on the surface, and someone else touches that surface soon after the cough or sneeze.”24 Even then physical and immunological defences make it highly unlikely that an infection will occur.
These findings suggest that enthusiastic cleaning, sanitizing and hand washing is unnecessary and that there is no justification for removing reading material. Apart from the increased costs and environmental pollution associated with these activities, they reinforce the idea – promoted by the hygiene hypothesis – that reductions in dental staff immune defences are possible when they are over exposed to cleaning and disinfecting products.10
Rather than recognize such limitations and contraindications, the asymptomatic transmission of COVID-19 is also being employed by the proponents of the PP to promote most of the pandemic inspired IPAC protocols. How is this justifiable?
SARS-CoV-2 is a respiratory virus. There is every reason to expect that it will behave as other similar viruses do especially its endemic coronavirus cousins (OC43, 229E, NL63 and HKU1) which cause approximately 15-30% of common colds.25 To cause infections a sufficient dose of the viable virus must leave its host. Respiratory viruses do this by escaping from the respiratory tract via coughs and sneezes as described by Goldman. An individual might harbour SARS-CoV-2 and have non-existent to very mild symptoms, but unless the live virus is expelled in a sufficient amount by coughing and sneezing to overcome the natural defences of a secondary host, transmission of the infection will not occur. That is why the pre-symptomatic transmission of COVID-19 is considered rare and a negligible risk to the public.26 This means that otherwise healthy patients who do not exhibit the signs and symptoms of a common cold are very unlikely to transmit COVID-19. In addition to this realization is the fact that persons with upper respiratory tract infections are unlikely to undergo elective dental treatment. Therefore, patients without such diseases are not candidates for transmitting SARS-CoV-2.
The concept of the asymptomatic spread of SARS-CoV-2 from individuals who do not have and never exhibit the signs and symptoms associated with COVID-19 has been refuted by the investigation performed by Craig and Engler.26 They emphasize that, “Evidence of asymptomatic transmission has been based on only a handful of instances which themselves are questionable.”26 Following a thorough analysis of the credibility of these instances they concluded that, “The evidence that asymptomatic transmission exists at all is tissue thin.”26 This opinion has been reinforced by a study which found that the signs and symptoms of a flu like illness were requisites for the transmission of COVID-19 among households and, that there was a notable lack of asymptomatic transmissions.27
All of this implies that there is no justification in adopting the PP inspired protocols for dentistry. Patients not suffering from colds do not need to wait in their cars, they can share the waiting room with similar patients, they do not have to communicate through plexiglass barriers, and they do not have to be greeted by staff in space suits wielding infrared thermometers. In a similar vein, there is no reason why staff meetings cannot be held while enjoying lunch.
An obvious disadvantage of the current protocols is that they promote the unfounded idea that a dental practice is a significant source for COVID-19 transmission. This belief demands the adoption of extraordinary and expensive clinically unsubstantiated protocols. To the proponents of the PP, the creation of dentally generated aerosols is another reason to justify these procedures.
The aerosol transmission of SARS-CoV-2 requires that infectious virus must persist between generation of the aerosol and its inhalation by a secondary host.28 The detection of RNA virus by PCR testing especially when high cycle threshold levels are used is not necessarily indicative of transmissible infectious virus.16 Studies on the infectivity retention of aerosolized SARS-CoV-2 tend to be in vitro and should not be assumed to apply in vivo.29 Public Health Ontario (PHO) appreciates this proviso by noting that clinical investigations demonstrate little risk to staff and patients from bio-aerosols generated in dental settings.30
According to PHO, Aerosol Generating Medical Procedures (AGMPs) are those that, “…both potentially create aerosols and are epidemiologically demonstrated to increase the risk of viral transmission.”30 The PHO’s contradictory approach to dentally generated aerosols is illustrated by its emphatic declaration that aerosol secretions from dental procedures are not AGMPs, while at the same time admitting that – though disease transmission from dental aerosols is rare- they are deemed to be AGMPs.30 This is a prime example of the inherently conflicting nature of the PP. Interestingly, real life hospital experiences demonstrate that with or without respiratory protections there have been minimal rates of transmissions from significant AGMPs, and that this route of transmission is likely exaggerated.31
As noted above, any airborne route for SARS-CoV-2 transmission requires that the virus remains infectious throughout its travel. The possibility that dental aerosols transmit the virus or that its transmission can be avoided by using sophisticated air filters, negative pressure rooms and fallow operating times (arbitrary delays between patients) must be justified by live viral studies and not by a reliance on laboratory cultures or simulated experiments. To date, no such investigations have been conducted. Accordingly, pandemic inspired IPAC protocols relating to those issues are manifestations of the PP which, not surprisingly, have generated unintended and expensive consequences with no demonstrable effect on the alleged transmission of SARS-CoV-2 by dental procedures.
Personal Protective Equipment
It is assumed that dental staff wear masks, face shields and gowns to protect them from acquiring COVID-19. Interestingly, a 1994 study demonstrated that compared to controls, dentists had significantly elevated levels of antibodies to influenza A and B and respiratory syncytial virus. The wearing of masks and eyeglasses did not lessen the production of the antibodies.32 Cochrane Reviews published in 2020 found that studies on the effectiveness of protective clothing worn by healthcare workers were of low to very low quality, suffered from simulated as opposed to clinical investigations, had few participants and were subjected to assessor bias.33 There were no studies relating to goggles or face shields.33 Clothes covering more areas of the body while perhaps giving more protection proved to be uncomfortable to wear and more difficult to don and doff creating opportunities for cross contamination.34 Assuming that PPE is worn to protect staff and patients, used PPE must be deemed as potentially infectious demanding its safe removal and disposal after every patient. This is an expensive and time consuming task when treating patients with no evidence of an upper respiratory track infection.
Other disadvantages of protective clothing included difficulty in communicating with fellow workers and patients, skin problems from goggles and masks, the induction of hot flushes and the very real possibility of frightening patients faced by staff in full protective gear.34 Other problems have arisen because of the questionable adequacy of training and in resolving issues when practice policies and procedures on protective equipment varied from national guidelines.34
A 2006 study of N95 respirators and surgical masks concluded that, “The N95 filtering face piece respirators may not provide the expected protection level against small virions. Some surgical masks may let a significant fraction of airborne viruses penetrate through their filters.”35
The use of personal protective equipment would appear to be a “no brainer” however that use is accompanied by distinct problems. This, along with the other examples cited above, illustrates the inherent faults in the PP. Despite its obvious failings, it was predictably inevitable that the PP would be employed to navigate dentistry through the pandemic. Now that the pandemic has become endemic a reassessment of IPAC protocols is necessary.
Dentistry beyond COVID-19
The pandemic phase of COVID-19 will end and it will re-emerge as a seasonally mediated flu like illness. Dentistry should be prepared to adjust to this change. Surprisingly, this will be relatively simple.
The current COVID-19 IPAC procedures are centred on confirmed and suspected cases of COVID-19 supported by the mistaken belief that all patients should be consider as having the disease. As has been demonstrated, screening procedures are redundant apart from determining if patients are exhibiting coughs and sneezes. Patients without these symptoms can be treated using pre-pandemic protocols. Case by case assessments should be made on patients with those symptoms to determine that the IPAC procedures used are commensurate with the planned treatment. In making those determinations, staff should adopt the same criteria as would be applicable to patients with coughs and colds prior to the COVID-19 era.
Additional factors that will alleviate concerns with COVID-19 are the following:
- SARS-CoV- 2 is a lipid enveloped virus that it is readily deactivated by low level disinfectants.36
- The lipid membrane is highly sensitive to disruption by ethanol, chlorhexidine, cetylpyridinium, chloride, hydrogen peroxide and povidone-iodine.36 There is no reason why these products cannot be used to give antibacterial mouthwashes the extra benefit of being antiviral.37
- A comprehensive review published in 2012 described the numerous naturally occurring defense proteins present in saliva which have antibacterial, antifungal and antiviral properties.38 It is likely that these play a significant role in reducing the pathogenic potential of dentally induced aerosols.
- There is a paucity of studies linking dental aerosols to disease transmission.39
- Attempting to achieve an absolutely safe dental environment with a guaranteed zero risk of disease transmission is an impossible goal. This reality must be accepted by dental staff, dental patients and dental regulatory agencies.
This article has demonstrated two facts. One, COVID-19 is or will become endemic. Two, dentistry’s approach to the pandemic has been driven by the highly questionable Precautionary Principle. This has resulted in the adoption of a series of actions not motivated by clinical studies but by worse-case scenarios as required by the “better safe than sorry” philosophy. In turn this has caused a spiral of escalating procedures of doubtful benefit many of which have secondary disadvantages including the hiring of extra staff and significant increases in practice overheads. The realization that SARS-CoV-2 is rarely spread by fomites, asymptomatically or by dentally generated aerosols should be an incentive to return to pre-pandemic IPAC procedures. The degree to which personal protection should be worn should depend on the level of risk that informed staff are willing to accept.
Finally, there should be an acceptance of the fact that the Precautionary Principle is a flawed method of directing infection prevention and control procedures for a profession with a demonstrably low level of disease transmission. The burden of proof that such protocols are necessary rests with the advocates of the Precautionary Principle. Until that occurs this article has provided practical evidence which allows for a realistic perspective of dentistry in the era of endemic COVID-19.
Oral Health welcomes this original article.
Only the principal author is cited.
- Joffe A. R. COVID-19 Rethinking the Lockdown Groupthink. 15th October 2020. Available at: http://orcid.org/0000-0002-4583-70X
- Royal College of Dental Surgeons of Ontario. Covid-19: Managing Infection Risks During In-Person Care. January 14th, 2021 Available at: https://az184419.vo.msecnd.net/rcdso/pdf/standards-of-practice/RCDSO_COVID19_Managing_In_Person_Care_Jan_2021.pd
- Adler J.H. Dangerous Precautions. National Review Online. September 13th, 2002. Available at: www.nationalreview.com/script/printpage.p?ref=/adler/adler091302.asp
- Sunstein C.R. Laws of Fear: Beyond the Precautionary Principle. Cambridge University Press, New York, 2005.
- Durodie B. The Precautionary Principle Assumes That Prevention Is Better than Cure. Spiked. March16th, 2004. Available at: www.durodie.net/articles/spiked/20040316precautionarypriciple.htm
- Goodman R.A. Transmission of Infectious Diseases in Outpatient Health Care Settings. JAMA 1991; 265(18): 2377-2381.
- Evidence Summary: what “cost of illness” is there about cross- infection related infections in dental practice? British Dent J 2010; 209: 87-88.
- Hardie J. The Surprising Absence of Disease Transmission From Infection Control Disasters. Oral Health, September 1st, 2015.
- Cleveland J. L. Transmission of blood- borne pathogens in US dental health care settings: 2016 update. J Am Dent Assoc 2016; 147(9): 729-738.
- Hardie J. Are Our Clean Operatories Harming Us? Oral Health, September 1st, 2011.
- Dinwiddie M.T. Recent Evidence Regarding Triclosan and Cancer Risk. Int J Environ Res Public Health. 2014; 11(2): 2209-2217.
- 3M Company. Policy: Evidence of an effective steam sterilization process will be documented. Available at: https://multimedia.3m.com/mws/media/788642O/ravity-steam-sterilization-process-using-3m-attest-rapid-5.pdf
- Hardie J. Gloves Spread Disease and Have Created an Infection Control Dilemma. Oral Hygiene November, 2018.
- Oxford Languages. Available at: https://languages.oup.com/google-dictionary-en/
- Government of Canada. Covid-19 signs, symptoms and severity of disease: A clinician guide. September, 2020. Available at: https//www.canada.ca/en/public-health/services.
- Hardie J. The Problems with the COVID-19 Test: A Necessary Understanding. Oral Health February, 2021
- Cochrane Rapid Review investigates the effectiveness of screening for COVID-19. October, 2020. Available at: https://www.cochrane.org/news/cochrane-rapid-review-investigates-effectiveness-screening-covid-19.
- Alberta Health Services, COVID-19 Scientific Advisory Group. Are healthcare workers at increased risk of COVID-19 rapid review. May 2020 Available at: albertahealthservices.ca/assets/info/ppih/if-ppih-covid-19-hcw-risk-rapid-review.pdf
- Government of Canada. Non-contact infrared thermometers (NCIT) January, 2021. Available at: https://www.canada.ca/en/health-canada/services
- Wright W.F. Why Temperature Screening for COVID-19 with Non-Contact Infrared Thermometers Doesn’t Work. Open Form Infectious Diseases 2020; DOI: 10.1093/ofid/ofaa603
- Lewis D. COVID-19 rarely spreads through surfaces. So why are we still deep cleaning? Nature. 2021; 590:26-28
- Editorial. Coronavirus is in the air- there’s too much focus on surfaces. Nature 2021; 590: 7
- Dowell S.F. Severe acute respiratory syndrome coronavirus on hospital surfaces. Clin Infect Dis 2004; 39: 652-657.
- Goldman E. Exaggerated risk of transmission of COVID-19 by fomites. Lancet Infect Dis 2020; 20: 892-893.
- Messel-Lemoine M. A Human Coronavirus Responsible for the Common Cold Massively Kills Dendritic Cells but Not Monocytes. J. Virol 2012; 86(14): 7577-7587.
- Craig C. Covid: The woeful case for asymptomatic transmission. Conservative Woman, December, 2020. Available at: https://www.conservativewoman.co.uk/covid-the woeful-case-for-asymptomatic-transmission/
- Madewell Z.J. Household Transmission of SARS-CoV-2 A Systematic Review and Meta-analysis. JAMA Open 2020; 3(12):e2031756.doi:10.1001/jamanetworkopen.2020.31756
- Schuit M. Airborne SARS-CoV-2 Is Rapidly Inactivated by Simulated Sunlight. J Infect Dis 2020; 222: 564-571.
- Fears S.C. Persistence of severe acute respiratory syndrome coronavirus 2 in aerosol suspensions. Emerg Infect Dis 2020; 26(9): Available at: https://doi.org/10.3201/eid2609.201806
- Public Health Ontario. COVID-19 in Dental Settings. August 2020. Available at: https://www.publichealthontario.ca/-/medi/doc
- Chagla Z. Re: It Is Time to Address Airborne Transmission of COVID-19. Clinical Infectious Diseases, 2020;, ciaa1118 Available at: https://doi.org/10.1093/cid/ciaa1118
- Davies K.J. Seroepidemiological study of respiratory virus infections among dental surgeons. Br Dent J 1994; 176(7): 262-265.
- Cochrane Rapid Review. Fast-Tracked Update: Protective clothes and equipment for healthcare workers to prevent coronavirus and other highly infectious diseases. April 2020. Available at: https://www.cochrane.org/news/fast-tracked-update-protective-clothes-and-equipment-healthcare-workers-prevent-coronavirus-
- Chapman S. Personal protective equipment (PPE) for healthcare workers: new Cochrane evidence. April 2020. Available at: https://www.evidentlycochrane.net/author/sarahchapman/
- Balazy A. Do N95 respirators provide 95% protection level against airborne viruses, and how adequate are surgical masks? Am J Infect Control 2006; 34(2): 51-57.
- O’Donnell V.B. Potential Role of Oral Rinses Targeting the Viral Lipid Envelope in SARS-CoV-2 Infection. Function 2020; 1(1): 1-12.
- Fabian T.K. Salivary Defense Proteins: Their Network and Role in Innate and Acquired Oral Immunity. Int J Mol Sci 2012; 13:4295-4320.
- Zemouri C. A scoping review on bio-aerosols in healthcare and the dental environment. PloSOne. 2017; 12(5):e0178007. Available at: https://doi.org/10.1371/journal.pone.0178007
About the Author
Dr. Hardie, although retired from practice, maintains a thirty plus years interest in the discipline of infection control as it relates to dentistry. He has published extensively on the subject and has lectured on it and related subjects throughout North America and in the UK, Europe, the Middle and Far East.