Opinion: Dentistry, Diagnostic Test Accuracy (DTA) and the Covid-19 Antibody Test

Link to the Dental Elf

Virus Outbreak Germany

As we are acutely aware the whole country has been locked down in an attemp to reduce the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 (Covid-19)), while we restructure the healthcare systems and direct research funding into either a treatment and/or a vaccine. The next stage is to rapidly scale up diagnostic testing to collect robust base-rate data at both an individual, and population level for future high quality decision-making (Ioannidis, 2020). The need to know who has been infected will be particularily important for dental care professionals due to the potential risk of Covid-19 spread via aerosol generating procedures (Coulthard, 2020). So what is the current state of affairs regarding quick point-of-care antibody testing? How good is it, how good should it be, and why is this important?

Firstly I am going to use a recently published paper that evaluated 10 antibody tests for SARS-CoV-2 using Enzyme-Linked Immunosorbent Assay (ELISA) and Lateral Flow Immune Assay (LFIA), lateral flow assay utilise the same technology commonly used for pregnancy tests (Crook, 2020). This particular paper has sparked considerable controversy which I will go into later. If you need more detail on how these tests work and their advantages/disadvantages then please take a look at the Oxford COVID-19 Evidence Service (Green et al., 2020). When looking at diagnostic accuracy testing the two main concepts to understand are:

Sensitivity The ability of a diagnostic test to give a positive result when it is supposed to be positive.

Specificity The ability of a diagnostic test to indicate a negative result when it is supposed to be negative.


After extracting the primary data from the individual tests, meta-analysis was carried out using the ‘mada’ package in R. The summary estimate for sensitivity was 62.7% (95%CI: 57.5 to 67.7) and specificity 96.9% (95%CI: 95.2 to 98.0) The results for the ELISA test and the 9 LFIA tests were plotted below on to a Summary Receiver Operating Characteristic (sROC) curve ( See Figure 1). The y-axis represents the sensitivity (1.0 =100%), and the x-axis represents 1- specificity (0.10 = 10%). For a test to be perfect the summary estimate point should be in the top left corner representing 100% true-positives and 0% false-positives. The blue dot represents the summary estimate for the tests surrounded by a 95% confidence area, the red dot represents the specification target of >98% (95%CI: 96 to 100%)  for sensitivity, and >98% (95%CI: 96 to 100%) for specificity, set by the Medicines & Healthcare Products Regulatory Agency (MHRA., 2020).

Figure 1. sROC curve – Antibody tests

sROC_DT_1_LI (2)


So why is so important to set the levels of sensitivity and specificity so high? Imagine we have a small city with a population of 100,000. The prevalence of people who have had the virus and recovered is 6%  and you are using an LFIA test with a sensitivity of 63% and specificity of 97%. Out of 6600 people who test positive for virus antibody only 3780 are true positives which corresponds to 57% having a correct positive diagnosis (See Figure 2.). Another important consideration is that 3% of the population who do not have antibodies test positive (n= 2820) and could lead them to believe they are immune.

Figure 2.Frequency tree of Covid-19 antibody screening

Annotation 2020-05-09 193854

The second point about this paper is that in its present format it cannot be used in any future analysis since the companies that supplied the tests required a commercial confidentiality agreement to be signed with the UK Department of Health making it impossible to discriminate between tests. The current set of results show poor performance, and that is why the MHRA has specifically set its targets high because of the risks that  results could pose if they were used to ease a lockdown, or they become part of an immunity passport system (Mahase., 2020; WHO, 2020). The final point is that whenever we have to deal with diagnostic tests or screening devices in either our professional or private lives we need to be able to identify the products, their comparators, and how accurate they are before making a significant decision to use or purchase the product. False-positive and false-negative results can pose significant harms to both ourselves and the population in general.

Disclaimer:  The article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author and not necessarily those of the host institution. The views are not a substitute for professional advice.


COULTHARD, P. 2020. Dentistry and coronavirus (COVID-19) – moral decision-making. Br Dent J, 228, 503-505.

CROOK, D. W. 2020. Evaluation of antibody testing for SARS-CoV-2 using ELISA and lateral flow immunoassays [Online]. Department of Microbiology, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom.  [Accessed].

GREEN, K., , A. W., DICKINSON, R., GRAZIADIO, S., ROBERT WOLFF, MALLETT, S. & ALLEN, A. J. 2020. What tests could potentially be used for the screening, diagnosis and monitoring of COVID-19 and what are their advantages and disadvantages? [Online]. Available: https://www.cebm.net/covid-19/what-tests-could-potentially-be-used-for-the-screening-diagnosis-and-monitoring-of-covid-19-and-what-are-their-advantages-and-disadvantages/ [Accessed].

IOANNIDIS, J. P. 2020. A fiasco in the making? As the coronavirus pandemic takes hold, we are making decisions without reliable data [Online]. STAT. Available: https://www.statnews.com/2020/03/17/a-fiasco-in-the-making-as-the-coronavirus-pandemic-takes-hold-we-are-making-decisions-without-reliable-data/ [Accessed].

MAHASE., E. 2020. Covid-19: Confidentiality agreements allow antibody test manufacturers to withhold evaluation results.

MHRA.2020.Target_Product_Profile_antibody_tests_to_help_determine_if_people_have_immunity_to_SARS-CoV-2_ [Online]. Available: https://www.gov.uk/guidance/guidance-on-coronavirus-covid-19-tests-and-testing-kits [Accessed].

WHO.2020. “Immunity passports” in the context of COVID-19 [Online]. Available: https://www.who.int/news-room/commentaries/detail/immunity-passports-in-the-context-of-covid-19 [Accessed].

Disclaimer: the article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author. The views are not a substitute for professional medical advice.


What is the most appropriate gown/apron for preventing Covid-19 contaminated fluids transfer in dental practice?

Originally posted on the Dental Elf

L0028811 A nurse and a surgeon, both wearing gown and mask. Etching b


Which gown/apron combination provides the best protection in the dental practice?

Bottom-line answer:

From this reanalysis of the primary data the reusable cotton surgical gown may be more practical in the dental environment in the long-term than the disposable fluid resistant gown due to its reduce potential for cross contamination during use. The plastic apron creates the most cross contamination and should only be used if there is significant risk of fluid contamination.


This paper is a reanalysis of a recent systematic review (Verbeek et al., 2020) on personal protective equipment (PPE), reframing the question to fit into the new clinical workflow created by Covid-19, and dental aerosol generating procedures (AGPs). I have covered face masks in a previous post.

Much has been written on the epidemiology of Covid-19 and its transmissibility via contact, droplets, aerosols, or faeco-oral route. The main concern within dentistry being the aerosol generated during many routine dental procedures (Coulthard, 2020). To reduce this contamination risk Public Health England’s guidance document for personal protective equipment updated 3 May 2020 Section 10.4 (GOV.UK, 2020) states that:-

‘Disposable fluid repellent coveralls or long-sleeved gowns must be worn when a disposable plastic apron provides inadequate cover of staff uniform or clothes for the procedure or task being performed, and when there is a risk of splashing of body fluids such as during AGPs in higher risk areas or in operative procedures. If non-fluid-resistant gowns are used, a disposable plastic apron should be worn’.

As this advice is generic and the workflow within a critical care unit differs from a dental practice it is important to evaluate the best available evidence from a primary care rather than secondary care perspective.


To save unnecessary duplication of search strategies and risk of bias/quality assessments I utilised the most up to date Cochrane Review of PPE for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff (Verbeek et al., 2020). This systematic review included 17 studies with 1950 participants evaluating 21 interventions. The authors concluded:

‘We found low- to very low-certainty evidence that covering more parts of the body leads to better protection but usually comes at the cost of more difficult donning or doffing and less user comfort, and may therefore even lead to more contamination. More breathable types of PPE may lead to similar contamination but may have greater user satisfaction.’

The authors conclusion helped to focus the next stage of analysis which was based around the levels of contamination and wearability. From the included studies two randomised simulation trials, one of a parallel design (Wong et al., 2004) and a second of a cross-over design (Guo et al., 2014) were selected as they contained sufficient primary data to undertake a meta-analysis. A simulation trial utilises aerosolised fluorescent dye sprayed on the PPE instead of true viral contamination. It was possible to extract data on contamination of  fluid resistant disposable gowns, standard cotton surgical gowns, and plastic aprons. The data was placed in Excel and then transferred to R for meta-analysis using the ’meta’ package. A random effect model was used with a Hartung Knapp conversion due to variability within the studies. Prediction intervals were included to facilitate the estimation for future studies.


The first meta-analysis compared a fluid resistant disposable gown with a standard cotton gown for both Wong and Guo. In Guo’s study the group tried two methods of doffing PPE: their individual accustomed removal method (IARM), and gown removal methods recommended by the Centers for Disease Control and Prevention (CDC).

The overall result favoured the cotton gown, but the result was non-significant, the mean difference (MD) was 0.91 (95%CI: -0.34 to 2.66) (See Figure 1.). The second meta-analysis showed significantly less contamination of the cotton surgical gowns compared with the plastic apron, the  MD was 8.4 (95%CI: 0.59 to 16.2) (See Figure 2.). The final analysis looked at the  contamination of the clinician post PPE removal showing equal contamination between the different PPE types MD was -0.02 (95% CI: -1.43 to 1.40) (See Figure 3).

Figure 1.Forest plot of disposable fluid resistant gown vs cotton gown


Figure 2. Forest plot of plastic apron vs cotton gown


Figure 3. Forest plot of body contamination



From the results of the meta-analysis there is little difference between the disposable fluid resistant gown and the reusable cotton surgical gown in terms of contamination/protection of both the wearer, patient, and clinical environment. The results favour the cotton gown as cotton through its material and properties can absorb droplet contaminants and thereby reduce opportunities for such contaminants to spread to the environment. The plastic apron performed worst and may significantly increase the risk of cross contamination both to the clinician and patient and should only be necessary where there is a risk of serious fluid contamination.

There is an interesting paper recently published by Phan and co-workers (Phan et al., 2019) who observed that ‘90% of observed doffing was incorrect, with respect to the doffing sequence, doffing technique, or use of appropriate PPE. Common errors were doffing gown from the front, removing face shield of the mask, and touching potentially contaminated surfaces and PPE during doffing’.

These results presented are hypothetical and due to the lack of specific studies of virus penetration through gowns in dentistry and are based on surrogate, and composite outcomes. There is an urgent need for specific studies to address PPE performance in the dental surgery environment.

Disclaimer:  The article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author and not necessarily those of the host institution. The views are not a substitute for professional advice.


COULTHARD, P. 2020. Dentistry and coronavirus (COVID-19) – moral decision-making. Br Dent J, 228, 503-505.

GOV.UK. 2020. COVID-19 ( personal protective equipment (PPE) [Online]. Available: https://www.gov.uk/government/publications/wuhan-novel-coronavirus-infection-prevention-and-control/covid-19-personal-protective-equipment-ppe [Accessed].

GUO, Y. P., LI, Y. & WONG, P. L. 2014. Environment and body contamination: a comparison of two different removal methods in three types of personal protective clothing. Am J Infect Control, 42, e39-45.

PHAN, L. T., MAITA, D., MORTIZ, D. C., WEBER, R., FRITZEN-PEDICINI, C., BLEASDALE, S. C., JONES, R. M. & PROGRAM, C. P. E. 2019. Personal protective equipment doffing practices of healthcare workers. Journal of occupational and environmental hygiene, 16, 575-581.

VERBEEK, J. H., RAJAMAKI, B., IJAZ, S., SAUNI, R., TOOMEY, E., BLACKWOOD, B., TIKKA, C., RUOTSALAINEN, J. H. & KILINC BALCI, F. S. 2020. Personal protective equipment for preventing highly infectious diseases due to exposure to contaminated body fluids in healthcare staff. Cochrane Database Syst Rev, 4, CD011621.

WONG, T. K., CHUNG, J. W., LI, Y., CHAN, W. F., CHING, P. T., LAM, C. H., CHOW, C. B. & SETO, W. H. 2004. Effective personal protective clothing for health care workers attending patients with severe acute respiratory syndrome. American journal of infection control, 32, 90-96.

Other  links

Personal protective equipment: a commentary for the dental and oral health care team on  Verbeek et al .

How much extra protection does an FFP3 mask offer in the dental surgery?



How much additional protection does a Class 3 filtering facepiece (FFP) mask offer over an FFP2 mask or a standard fluid resistant surgical facemask (Type IIR) when worn during aerosol generating procedures (AGPs) in dentistry?

Bottom-line answer:

From the evidence presented below there would appear to be small additional protection (0.4%) offered by and FFP3/FFP2 masks compared to a surgical facemask during aerosol generating procedures in the dental environment if high volume suction and rubber dam are used in combination. In the absence of rubber dam this difference increases to 7%.


Much of the UK emergency planning regarding Covid-19 stems from protocols following the Severe Acute Respiratory Syndrome (SARS) epidemic of 2003. In terms of dentistry our current measures were outlined in  a paper by Li and co-workers (Li et al., 2004). The major difference between the planning for SARS/MERS and Covid-19 is that both the preceding respiratory viruses were considerably more dangerous with a cumulative fatality rate (CFR)  of 11% and 34% respectively, whereas estimates to date suggest a CFR for Covid-19 <1% (Park et al., 2020; Rajgor et al., 2020; Bendavid et al., 2020).

The Public Health England guidance document for personal protective equipment updated 27 April 2020 (GOV.UK, 2020) states the need to limit the use of fluid resistant surgical facemasks (FRSM) to non-AGP procedures, and FFP2/FFP3 for aerosol generating procedures (AGPs) procedures. This guidance is general, and not specific to dental AGPs. In order to assess how effective the use of these masks in the dental environment is when an AGP is created we need to go to a review by Harrel and co-workers post SARS (Harrel and Molinari, 2004) who cited 5 main categories of AGP:

  • Ultrasonic and sonic scalers
  • Air polishing
  • Air-water syringes
  • Tooth preparation with a high/slow speed handpiece
  • Tooth preparation with air abrasion

Besides good cross infection policy the three papers (Harrel and Molinari, 2004; Li et al., 2004; Kohn et al., 2003)  published just after SARS all mention three methods to reduce AGPs; appropriate PPE, rubber dam isolation and high volume suction equipment, which is common to all dental surgeries.

Rubber dam has been in use since 1864 and is used to isolate one or more teeth from the fluids in the oral environment using a thin sheet of latex or silicon rubber. High volume suction draws a large volume of air away from the oral cavity during operative procedure also reducing the amount of aerosol and splatter.


To see how effective these three pieces of equipment a rapid review of high-volume aspiration and rubber dam was undertaken.  A recent systematic review, and rapid review of surgical masks versus FFP3 masks  had already concluded finding no statistical difference in effectiveness between the masks regarding influenza like viral infections (Long et al., 2020; Greenhalgh et al., 2020). The filtration capacity of a standard surgical face mask is highly variable compared to an FFP2 or FFP3 mask, Oberg and co-workers (Oberg and Brosseau, 2008) concluded that none of the surgical masks tested in-vivo on 40 subjects exhibited adequate filter performance and facial fit characteristics to be considered respiratory protection devices. The mean penetration by 0.8μm latex spheres was 37.89 (95% CI: 25.8% to 50.0%) for the dental quality masks in their study (A,B,C, and E).

For the rapid review observational studies comparing the effect on aerosol and bioaerosol contamination form the use of high-volume aspiration and/or rubber dam compared with dental treatment without these procedures in place were identified.  There was no language or date restriction. Ovid (Medline), Scopus (Elsevier) and the Cochrane databases were searched (See Appendix).

Seven studies fulfilled the inclusion criteria. 3 studies related to high volume suction (Harrel et al., 1996; Jacks, 2002; Devker et al., 2012), and 4 related to the use of rubber dam (Cochran et al., 1989; Samaranayake et al., 1989; Dahlke et al., 2012; Al-Amad et al., 2017). The studies were all moderate to low quality. There was insufficient data for meta-analysis.

Summary of findings

High volume suction

Regarding the use of high volume suction Harrel and co-workers (Harrel et al., 1996) undertook an in vitro study using an ultrasonic scaler for 1 minute to generate a dye containing aerosol, the experiment was repeated 10 times. The high-volume evacuator attachment produced a 93% reduction in surface contamination . Jacks performed a similar in-vitro study resulting in a 90.8% reduction in surface contamination (Jacks, 2002). The only in-vivo study was by Devker and co-workers (Devker et al., 2012), 30 dentate subjects  had half their mouths cleaned using an ultrasonic scaler as a control and the other half using high volume suction. 4 culture plates were placed on the operator and patient resulting in an 81% reduction in bacterial culture forming units.

 Rubber dam placement


The second part of the review related to rubber dam usage. In Cochran’s study  (Cochran et al., 1989) microbial collection was performed during preparation and  placement of amalgam and composite resin restorations with and without the rubber dam resulting in a 90% to 98% reduction in microorganisms. Samaranayake (Samaranayake et al., 1989) undertook an in-vivo study with 10 child patients in each arm. The control group had their conservative dentistry with high volume suction only and the experimental group had high volume suction with rubber dam isolation. The mean reduction in culture forming units at 1 meter was 87.9% ±10.3 with the rubber dam . Dahlke conducted an in-vitro study using dye, rubber dam and high-volume suction while preparing the surface of a typodont tooth with a dental handpiece. The experiment was repeated 24 times resulting in a 33% reduction in surface contamination. The final study involved 52 senior dental students performing restorative dental treatment with and without a rubber dam (Al-Amad et al., 2017) and produced a strange outlier results with an increased level of contamination, which may highlight technique sensitivity. The lack of papers is possibly a function of the large effect sizes produced in the earlier studies reducing the demand for duplication.

Putting the three components into a clinical workflow

There are three components here:

  1. High-volume suction reduces bioaerosols by about 81% to 90%
  2. Rubber dam reduces bioaerosols by a further 30% to 90%
  3. Fluid resistant surgical facemask filter 62% airborne particles
  4. FFP2 masks filter 94% airborne particles
  5. FFP3 masks filter 99% of airborne particles

Putting these components together in a clinical environment, a well-trained dental team using high-volume aspiration and rubber dam could reduce the bioaerosol by about 99%. If we take the efficacy of the masks as stated in government guidance and apply it to this reduction, we get an overall reduction in AGPs of 99.62% for the surgical mask, 99.94% for FFP2 masks and 99.99 for FFP3 respectively, with a risk difference (RD) of 0.37% between the surgical mask and FFP3 and a relative risk of 0.996 (See Table 1). With the lower suction efficiency of 81% without the use of rubber dam this difference would change to 7.03% RD and RR of 0.929. There was insufficient data to produce confidence intervals.

Table 1. Differences in face mask effectiveness in dental AGP

Mask Type Filtration (%) HVS* only (%) HVA+ RD (%) RDiff (%) RR
Surgical mask 62 92.78 99.62 6.84 0.931
FFP2 94 98.86 99.94 1.08 0.989
FFP3 99 99.81 99.99 0.18 0.998
HVA- High volume suction    RD – Rubber Dam    RDiff – Risk difference    RR – Relative risk


In the clinical environment where high volume aspiration and rubber dam is in use during dental AGP procedures there may be no significant additional benefit in wearing an FFP3/FFP2 or surgical mask. There is a much larger difference if the quality of the HVS is reduced and rubber dam is not used   It may be that the moderate benefit of FFP2 and FFP3 masks is lost over time due to functional factors such as movement of the mask or cross contamination from extended wear compared to changing masks between patients (Greenhalgh et al., 2020). Where supply of FFP3 masks might limit the delivery of primary dental care we will need to consider if the additional benefit is outweighed by the harms of delaying or restricting care to asymptomatic and healthy patients. These results are hypothetical and due to the lack of specific studies of virus penetration of facemasks in dentistry are based on surrogate, and composite outcomes. There is an urgent need for specific studies to address mask performance in the dental surgery environment.

Disclaimer:  The article has not been peer-reviewed; it should not replace individual clinical judgement, and the sources cited should be checked. The views expressed in this commentary represent the views of the author and not necessarily those of the host institution. The views are not a substitute for professional advice.


AL-AMAD, S. H., AWAD, M. A., EDHER, F. M., SHAHRAMIAN, K. & OMRAN, T. A. 2017. The effect of rubber dam on atmospheric bacterial aerosols during restorative dentistry. Journal of infection and public health, 10, 195-200.

BENDAVID, E., MULANEY, B., SOOD, N., SHAH, S., LING, E., BROMLEY-DULFANO, R., LAI, C., WEISSBERG, Z., SAAVEDRA, R. & TEDROW, J. 2020. COVID-19 Antibody Seroprevalence in Santa Clara County, California. medRxiv.

COCHRAN, M. A., MILLER, C. H. & SHELDRAKE, M. A. 1989. The efficacy of the rubber dam as a barrier to the spread of microorganisms during dental treatment. The Journal of the American Dental Association, 119, 141-144.

DAHLKE, W. O., COTTAM, M. R., HERRING, M. C., LEAVITT, J. M., DITMYER, M. M. & WALKER, R. S. 2012. Evaluation of the spatter-reduction effectiveness of two dry-field isolation techniques. J Am Dent Assoc, 143, 1199-204.

DEVKER, N. R., MOHITEY, J., VIBHUTE, A., CHOUHAN, V. S., CHAVAN, P., MALAGI, S. & JOSEPH, R. 2012. A study to evaluate and compare the efficacy of preprocedural mouthrinsing and high volume evacuator attachment alone and in combination in reducing the amount of viable aerosols produced during ultrasonic scaling procedure. The journal of contemporary dental practice, 13, 681-9.

GOV.UK. 2020. COVID-19 ( personal protective equipment (PPE) [Online]. Available: https://www.gov.uk/government/publications/wuhan-novel-coronavirus-infection-prevention-and-control/covid-19-personal-protective-equipment-ppe [Accessed 29th April 2020].

GREENHALGH, T., CHAN, X. H., KHUNTI, K., DURAND-MOREAU, Q., STRAUBE, S., DEVANE, D., TOOMEY, E., IRELAND, E. S. & IRELAND, C. 2020. What is the efficacy of standard face masks compared to respirator masks in preventing COVID-type respiratory illnesses in primary care staff?[Internet]. Oxford, UK: Oxford COVID-19 Evidence Service.

HARREL, S. K., BARNES, J. B. & RIVERA-HIDALGO, F. 1996. Reduction of aerosols produced by ultrasonic scalers. Journal of periodontology, 67, 28-32.

HARREL, S. K. & MOLINARI, J. 2004. Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. The Journal of the American Dental Association, 135, 429-437.

JACKS, M. E. 2002. A laboratory comparison of evacuation devices on aerosol reduction. Journal of dental hygiene: JDH, 76, 202-206.

KOHN, W. G., COLLINS, A. S., CLEVELAND, J. L., HARTE, J. A., EKLUND, K. J. & MALVITZ, D. M. 2003. Guidelines for infection control in dental health-care settings-2003.

LI, R., LEUNG, K., SUN, F. & SAMARANAYAKE, L. 2004. Severe acute respiratory syndrome (SARS) and the GDP. Part II: Implications for GDPs. British dental journal, 197, 130-134.

LONG, Y., HU, T., LIU, L., CHEN, R., GUO, Q., YANG, L., CHENG, Y., HUANG, J. & DU, L. 2020. Effectiveness of N95 respirators versus surgical masks against influenza: A systematic review and meta-analysis. J Evid Based Med.

OBERG, T. & BROSSEAU, L. M. 2008. Surgical mask filter and fit performance. Am J Infect Control, 36, 276-82.

PARK, M., THWAITES, R. S. & OPENSHAW, P. J. 2020. COVID‐19: Lessons from SARS and MERS. European Journal of Immunology, 50, 308.

RAJGOR, D. D., LEE, M. H., ARCHULETA, S., BAGDASARIAN, N. & QUEK, S. C. 2020. The many estimates of the COVID-19 case fatality rate. The Lancet Infectious Diseases.

SAMARANAYAKE, L., REID, J. & EVANS, D. 1989. The efficacy of rubber dam isolation in reducing atmospheric bacterial contamination. ASDC journal of dentistry for children, 56, 442-444.


Search strategy Ovid Medline

1 exp *dentistry/ or exp *dental care/ 291029
2 (dental or dentistry).m_titl. 141221
3 (high volume suction or high-volume aspiration).af. 18
4 1 or 2 or 3 371934
5 *Aerosols/ 8879
6 (aerosol* or bioaerosol* or bio-aerosols*).m_titl. 18171
7 5 or 6 20618
8 4 and 7 146
9 aspiration.mp. 82401
10 7 and 9 54
11 Suction/ 12363
12 3 or 9 or 11 90954
13 8 and 12 12
14 Rubber Dams/ 498
15 rubber dam*.mp. 1124
16 8 and 15 7

Other References

Dental Elf Blog – 25th Mar 2020