By Dr John Hardie BDS, MSc, PhD, FRCDC, and Dr George Freedman BSc, DDS, DiplABAD, FIADFE, FAACD
For at least three decades, masks have been compulsory requirements of the uniform worn by dentists and their clinical staff. The impetus for this behaviour might well have been the belief that masks would prevent contamination of blood and saliva from HIV infected patients. Although such a source of infection has never been documented, masked dentists have become the rule rather than the exception.
Simultaneously with this development, numerous clinical and laboratory studies have led to a better understanding of how respiratory pathogens, and particularly viruses are transmitted. These studies raised serious doubts concerning the ability of traditional masks to stop the transmission of respiratory infections such as influenza. These concerns were ignored during the COVID-19 pandemic when mask wearing became obligatory within all levels of society.
Fortunately, earlier studies on mask efficacy have continued culminating in the release of a recent major study which proves with as much certainty as is possible — that masks do not stop the spread of respiratory diseases such as COVID-19.
Based on this understanding, mask use in dentistry should be a personal decision irrespective of the opinions of peers and regulatory authorities. This article will provide the evidence to substantiate such a reassessment.
A purported reason for a mask is to prevent the airborne transmission of respiratory pathogens expelled as a moisture-laden suspension of droplet, and considerably smaller aerosol particles, during coughing, sneezing, and talking. The suspension experiences rapid dehydration which results in desiccation of the particles. This induces conformational changes in the lipid envelopes surrounding influenza, respiratory syncytial and coronaviruses such that they lose their ability to attach to and infect new host cells, effectively becoming noninfectious (Fig. 1).1,2
A nanometer is one billionth of a metre. A strand of human hair is approximately between 80,000- 100,000nm wide. The influenza and coronaviruses range from 80-120nm, or approximately 0.1µm in diameter. This means that approximately 1,000 of these viruses would fit across the width of a human hair.5,6 The best fitting mask will not prevent a single human hair from passing between it and the face.
N95 mask fabrics are designed to filter out 95% of airborne particles provided they are larger than 0.3µm in diameter and most surgical mask materials filter out particles 2.5µm or larger.7 Therefore, its effectiveness in filtering out viruses of 0.1µm in diameter is highly questionable. Even if such devices did impede the flow of influenza and coronaviruses, millions of stray viruses would continue to pass through the gaps present around the periphery of masks.
The Cochrane Collaboration, based in London, England, is an independent not-for-profit international network of researchers. By adopting meta-analytical methods which limit biases, random errors and increases the statistical power of its conclusions, the Collaboration has earned a global reputation for providing the highest standard in evidence-based healthcare.27
Randomised trials, the gold standard for medical research, are a major focus of the Collaboration. Such a trial for masks would consist of the subjects being divided at random into two groups: one with masks, one without masks, balanced by age, sex, and other pertinent characteristics. The Collaboration has been conducting meta-analysis reviews on physical interventions, including masks, to reduce respiratory viral transmissions since 2006.
The latest review of 11 new and 67 previous randomised trials involving a total of 610,872 participants was released in January 2023.28 It is a comprehensive, detailed 324-page report including results pertinent to the H1N1 pandemic, SARS, and COVID-19. Significant findings are as follows:
First, moderate degree of certainty that wearing masks compared to not wearing masks in the community makes little to no difference to the outcome of influenza-like and COVID19-like illness.
Second, moderate degree of certainty that wearing masks compared to not wearing masks in the community makes little or no difference to the outcome of laboratory-confirmed influenza/SARS-CoV-2.
ABOUT THE AUTHORS
Dr George Freedman is a founder and past president, American Academy of Cosmetic Dentistry; co-founder, Canadian Academy for Esthetic Dentistry; Regent and Fellow, International Academy for Dental Facial Esthetics (IADFE); Diplomate and Chair, American Board of Aesthetic Dentistry; and Adjunct Professor, Dental Medicine at Western University, Pomona, California. Dr Freedman is the author of 14 textbooks and more than 900 articles, and an internationally renowned lecturer.
As an oral pathologist, Dr John Hardie’s career focused on hospital-based dentistry in Ottawa, Vancouver, Saudi Arabia and Northern Ireland. This fostered an interest in infection prevention and control as it related to dentistry. He has published numerous articles on that topic and presented lectures on it and related subjects throughout North America, the UK, Europe and the Middle and Far East.