RR:C19 Evidence Scale rating by reviewer:
Potentially informative. The main claims made are not strongly justified by the methods and data, but may yield some insight. The results and conclusions of the study may resemble those from the hypothetical ideal study, but there is substantial room for doubt. Decision-makers should consider this evidence only with a thorough understanding of its weaknesses, alongside other evidence and theory. Decision-makers should not consider this actionable, unless the weaknesses are clearly understood and there is other theory and evidence to further support it.
The results of this in vitro study are potentially informative and actionable in validating the clinical team’s elevated risk for aerosol contamination.
The results indicate that during orthodontic debonding using a slow speed handpiece with dental suction to remove composite, the clinical team is at risk for aerosol contamination. Contamination was detectable up to 3.5 meters away from the clinical team.
However, and not surprisingly, contamination was less than the positive control – an anterior crown preparation using a high-speed air water turbine and dental suction. The clinical team contamination averaged 20% of that created during anterior crown preparation.1,2
The assessment used updated methods,2 pioneered some 50 years ago,3 for assessing aerosol spread during oral health care. The current study used fluorescein dye as a surrogate for salivary borne viral particles. Fluorescein ( 0.0007 microns)4 is approximately 1/150th the size of the SARS-CoV-2 viral particles (0.08 to 0.12 microns).5 Thus the results are likely to overestimate the spread distance of the coronavirus. Conversely, the viral spread pattern is likely to be similar to the fluorescein dye pattern.
The foregoing all speak to the strengths of the study. Troubling, however, are two items. First is the sparse information regarding the analytic methods. Specifically, the numbers on the tables do not appear to reconcile among themselves, or with the graphics, or with the written material in the Abstract and the Results. In parallel, the Figure Legend for the graphics needs greater detail for complete understanding and verification. The foregoing could be due to the reviewer’s misunderstanding of the Methods, Figure Legends, Abstract and Results. Nonetheless, these need to be more explicitly related.
The second item is the absence of a negative control for aerosol free care.6 A negative control would, in itself, be useful to assist in bracketing patterns of aerosol dispersion and potential risk.
Finally, as is true for all surrogate studies, the relationship of these findings to actual infection risk in practice is uncertain. The salivary coronavirus levels in healthy, symptom-free positive, symptom-positive, and validated infectious individual are uncertain.7,8 Similarly, uncertain are the virus’ toxic dose and dynamics of infectivity.9,10
1. Llandro H, Allison J, Currie C, et al. Evaluating aerosol and splatter during orthodontic debonding: implications for the COVID-19 pandemic. 2020:2020.2008.2019.20178319.
2. Allison JR, Currie CC, Edwards DC, et al. Evaluating aerosol and splatter following dental procedures: addressing new challenges for oral healthcare and rehabilitation. Journal of Oral Rehabilitation. 2020;n/a(n/a).
3. Miller RL, Micik RE, Abel C, Ryge G. Studies on dental aerobiology. II. Microbial splatter discharged from the oral cavity of dental patients. J Dent Res. 1971;50(3):621-625.
4. Pu Y, Wang W, Dorshow RB, Das BB, Alfano RR. Mini review of ultrafast fluorescence polarization spectroscopy [invited]. Applied optics. 2013;52(5):917-929.
5. Masters PS. The molecular biology of coronaviruses. Advances in virus research. 2006;66:193-292.
6. Benzian H, Niederman R. A dental response to the COVID-19 pandemic - Safe Aerosol-Free Emergent (SAFER) Dentistry. Frontiers in Medicine, Infectious Diseases – Surveillance, Prevention and Treatment. 2020;7(520).
7. To KK, Tsang OT, Yip CC, et al. Consistent Detection of 2019 Novel Coronavirus in Saliva. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2020;71(15):841-843.
8. Wyllie AL, Fournier J, Casanovas-Massana A, et al. Saliva or Nasopharyngeal Swab Specimens for Detection of SARS-CoV-2. N Engl J Med. 2020;383(13):1283-1286.
9. Chau NVV, Thanh Lam V, Thanh Dung N, et al. The natural history and transmission potential of asymptomatic SARS-CoV-2 infection. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2020.
10. Byrne AW, McEvoy D, Collins AB, et al. Inferred duration of infectious period of SARS-CoV-2: rapid scoping review and analysis of available evidence for asymptomatic and symptomatic COVID-19 cases. BMJ Open. 2020;10(8):e039856.